Merge "Revert "Add read barriers for the roots in the verifier.""

12 files changed, 478 insertions, 475 deletions

diff --git a/runtime/verifier/method_verifier-inl.h b/runtime/verifier/method_verifier-inl.h
index 0f9aeb5..2d9fd53 100644
--- a/runtime/verifier/method_verifier-inl.h
+++ b/runtime/verifier/method_verifier-inl.h
@@ -66,9 +66,9 @@ inline bool MethodVerifier::HasFailures() const {
   return !failure_messages_.empty();
 }
 
-inline RegType& MethodVerifier::ResolveCheckedClass(uint32_t class_idx) {
+inline const RegType& MethodVerifier::ResolveCheckedClass(uint32_t class_idx) {
   DCHECK(!HasFailures());
-  RegType& result = ResolveClassAndCheckAccess(class_idx);
+  const RegType& result = ResolveClassAndCheckAccess(class_idx);
   DCHECK(!HasFailures());
   return result;
 }
diff --git a/runtime/verifier/method_verifier.cc b/runtime/verifier/method_verifier.cc
index c21a7a4..9cde8da 100644
--- a/runtime/verifier/method_verifier.cc
+++ b/runtime/verifier/method_verifier.cc
@@ -1187,7 +1187,7 @@ bool MethodVerifier::SetTypesFromSignature() {
     // If this is a constructor for a class other than java.lang.Object, mark the first ("this")
     // argument as uninitialized. This restricts field access until the superclass constructor is
     // called.
-    RegType& declaring_class = GetDeclaringClass();
+    const RegType& declaring_class = GetDeclaringClass();
     if (IsConstructor() && !declaring_class.IsJavaLangObject()) {
       reg_line->SetRegisterType(arg_start + cur_arg,
                                 reg_types_.UninitializedThisArgument(declaring_class));
@@ -1219,7 +1219,7 @@ bool MethodVerifier::SetTypesFromSignature() {
         // it's effectively considered initialized the instant we reach here (in the sense that we
         // can return without doing anything or call virtual methods).
         {
-          RegType& reg_type = ResolveClassAndCheckAccess(iterator.GetTypeIdx());
+          const RegType& reg_type = ResolveClassAndCheckAccess(iterator.GetTypeIdx());
           if (!reg_type.IsNonZeroReferenceTypes()) {
             DCHECK(HasFailures());
             return false;
@@ -1253,8 +1253,8 @@ bool MethodVerifier::SetTypesFromSignature() {
           return false;
         }
 
-        RegType& lo_half = descriptor[0] == 'J' ? reg_types_.LongLo() : reg_types_.DoubleLo();
-        RegType& hi_half = descriptor[0] == 'J' ? reg_types_.LongHi() : reg_types_.DoubleHi();
+        const RegType& lo_half = descriptor[0] == 'J' ? reg_types_.LongLo() : reg_types_.DoubleLo();
+        const RegType& hi_half = descriptor[0] == 'J' ? reg_types_.LongHi() : reg_types_.DoubleHi();
         reg_line->SetRegisterTypeWide(arg_start + cur_arg, lo_half, hi_half);
         cur_arg++;
         break;
@@ -1546,7 +1546,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
        * This statement can only appear as the first instruction in an exception handler. We verify
        * that as part of extracting the exception type from the catch block list.
        */
-      RegType& res_type = GetCaughtExceptionType();
+      const RegType& res_type = GetCaughtExceptionType();
       work_line_->SetRegisterType(inst->VRegA_11x(), res_type);
       break;
     }
@@ -1560,7 +1560,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
     case Instruction::RETURN:
       if (!IsConstructor() || work_line_->CheckConstructorReturn()) {
         /* check the method signature */
-        RegType& return_type = GetMethodReturnType();
+        const RegType& return_type = GetMethodReturnType();
         if (!return_type.IsCategory1Types()) {
           Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "unexpected non-category 1 return type "
                                             << return_type;
@@ -1568,7 +1568,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
           // Compilers may generate synthetic functions that write byte values into boolean fields.
           // Also, it may use integer values for boolean, byte, short, and character return types.
           const uint32_t vregA = inst->VRegA_11x();
-          RegType& src_type = work_line_->GetRegisterType(vregA);
+          const RegType& src_type = work_line_->GetRegisterType(vregA);
           bool use_src = ((return_type.IsBoolean() && src_type.IsByte()) ||
                           ((return_type.IsBoolean() || return_type.IsByte() ||
                            return_type.IsShort() || return_type.IsChar()) &&
@@ -1585,7 +1585,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
     case Instruction::RETURN_WIDE:
       if (!IsConstructor() || work_line_->CheckConstructorReturn()) {
         /* check the method signature */
-        RegType& return_type = GetMethodReturnType();
+        const RegType& return_type = GetMethodReturnType();
         if (!return_type.IsCategory2Types()) {
           Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "return-wide not expected";
         } else {
@@ -1600,7 +1600,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
       break;
     case Instruction::RETURN_OBJECT:
       if (!IsConstructor() || work_line_->CheckConstructorReturn()) {
-        RegType& return_type = GetMethodReturnType();
+        const RegType& return_type = GetMethodReturnType();
         if (!return_type.IsReferenceTypes()) {
           Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "return-object not expected";
         } else {
@@ -1608,7 +1608,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
           DCHECK(!return_type.IsZero());
           DCHECK(!return_type.IsUninitializedReference());
           const uint32_t vregA = inst->VRegA_11x();
-          RegType& reg_type = work_line_->GetRegisterType(vregA);
+          const RegType& reg_type = work_line_->GetRegisterType(vregA);
           // Disallow returning uninitialized values and verify that the reference in vAA is an
           // instance of the "return_type"
           if (reg_type.IsUninitializedTypes()) {
@@ -1655,29 +1655,29 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
       /* could be long or double; resolved upon use */
     case Instruction::CONST_WIDE_16: {
       int64_t val = static_cast<int16_t>(inst->VRegB_21s());
-      RegType& lo = reg_types_.FromCat2ConstLo(static_cast<int32_t>(val), true);
-      RegType& hi = reg_types_.FromCat2ConstHi(static_cast<int32_t>(val >> 32), true);
+      const RegType& lo = reg_types_.FromCat2ConstLo(static_cast<int32_t>(val), true);
+      const RegType& hi = reg_types_.FromCat2ConstHi(static_cast<int32_t>(val >> 32), true);
       work_line_->SetRegisterTypeWide(inst->VRegA_21s(), lo, hi);
       break;
     }
     case Instruction::CONST_WIDE_32: {
       int64_t val = static_cast<int32_t>(inst->VRegB_31i());
-      RegType& lo = reg_types_.FromCat2ConstLo(static_cast<int32_t>(val), true);
-      RegType& hi = reg_types_.FromCat2ConstHi(static_cast<int32_t>(val >> 32), true);
+      const RegType& lo = reg_types_.FromCat2ConstLo(static_cast<int32_t>(val), true);
+      const RegType& hi = reg_types_.FromCat2ConstHi(static_cast<int32_t>(val >> 32), true);
       work_line_->SetRegisterTypeWide(inst->VRegA_31i(), lo, hi);
       break;
     }
     case Instruction::CONST_WIDE: {
       int64_t val = inst->VRegB_51l();
-      RegType& lo = reg_types_.FromCat2ConstLo(static_cast<int32_t>(val), true);
-      RegType& hi = reg_types_.FromCat2ConstHi(static_cast<int32_t>(val >> 32), true);
+      const RegType& lo = reg_types_.FromCat2ConstLo(static_cast<int32_t>(val), true);
+      const RegType& hi = reg_types_.FromCat2ConstHi(static_cast<int32_t>(val >> 32), true);
       work_line_->SetRegisterTypeWide(inst->VRegA_51l(), lo, hi);
       break;
     }
     case Instruction::CONST_WIDE_HIGH16: {
       int64_t val = static_cast<uint64_t>(inst->VRegB_21h()) << 48;
-      RegType& lo = reg_types_.FromCat2ConstLo(static_cast<int32_t>(val), true);
-      RegType& hi = reg_types_.FromCat2ConstHi(static_cast<int32_t>(val >> 32), true);
+      const RegType& lo = reg_types_.FromCat2ConstLo(static_cast<int32_t>(val), true);
+      const RegType& hi = reg_types_.FromCat2ConstHi(static_cast<int32_t>(val >> 32), true);
       work_line_->SetRegisterTypeWide(inst->VRegA_21h(), lo, hi);
       break;
     }
@@ -1690,7 +1690,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
     case Instruction::CONST_CLASS: {
       // Get type from instruction if unresolved then we need an access check
       // TODO: check Compiler::CanAccessTypeWithoutChecks returns false when res_type is unresolved
-      RegType& res_type = ResolveClassAndCheckAccess(inst->VRegB_21c());
+      const RegType& res_type = ResolveClassAndCheckAccess(inst->VRegB_21c());
       // Register holds class, ie its type is class, on error it will hold Conflict.
       work_line_->SetRegisterType(inst->VRegA_21c(),
                                   res_type.IsConflict() ? res_type
@@ -1736,7 +1736,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
        */
       const bool is_checkcast = (inst->Opcode() == Instruction::CHECK_CAST);
       const uint32_t type_idx = (is_checkcast) ? inst->VRegB_21c() : inst->VRegC_22c();
-      RegType& res_type = ResolveClassAndCheckAccess(type_idx);
+      const RegType& res_type = ResolveClassAndCheckAccess(type_idx);
       if (res_type.IsConflict()) {
         // If this is a primitive type, fail HARD.
         mirror::Class* klass = dex_cache_->GetResolvedType(type_idx);
@@ -1755,7 +1755,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
       }
       // TODO: check Compiler::CanAccessTypeWithoutChecks returns false when res_type is unresolved
       uint32_t orig_type_reg = (is_checkcast) ? inst->VRegA_21c() : inst->VRegB_22c();
-      RegType& orig_type = work_line_->GetRegisterType(orig_type_reg);
+      const RegType& orig_type = work_line_->GetRegisterType(orig_type_reg);
       if (!res_type.IsNonZeroReferenceTypes()) {
         if (is_checkcast) {
           Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "check-cast on unexpected class " << res_type;
@@ -1778,7 +1778,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
       break;
     }
     case Instruction::ARRAY_LENGTH: {
-      RegType& res_type = work_line_->GetRegisterType(inst->VRegB_12x());
+      const RegType& res_type = work_line_->GetRegisterType(inst->VRegB_12x());
       if (res_type.IsReferenceTypes()) {
         if (!res_type.IsArrayTypes() && !res_type.IsZero()) {  // ie not an array or null
           Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "array-length on non-array " << res_type;
@@ -1791,7 +1791,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
       break;
     }
     case Instruction::NEW_INSTANCE: {
-      RegType& res_type = ResolveClassAndCheckAccess(inst->VRegB_21c());
+      const RegType& res_type = ResolveClassAndCheckAccess(inst->VRegB_21c());
       if (res_type.IsConflict()) {
         DCHECK_NE(failures_.size(), 0U);
         break;  // bad class
@@ -1803,7 +1803,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
             << "new-instance on primitive, interface or abstract class" << res_type;
         // Soft failure so carry on to set register type.
       }
-      RegType& uninit_type = reg_types_.Uninitialized(res_type, work_insn_idx_);
+      const RegType& uninit_type = reg_types_.Uninitialized(res_type, work_insn_idx_);
       // Any registers holding previous allocations from this address that have not yet been
       // initialized must be marked invalid.
       work_line_->MarkUninitRefsAsInvalid(uninit_type);
@@ -1856,7 +1856,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
       work_line_->SetRegisterType(inst->VRegA_23x(), reg_types_.Integer());
       break;
     case Instruction::THROW: {
-      RegType& res_type = work_line_->GetRegisterType(inst->VRegA_11x());
+      const RegType& res_type = work_line_->GetRegisterType(inst->VRegA_11x());
       if (!reg_types_.JavaLangThrowable(false).IsAssignableFrom(res_type)) {
         Fail(res_type.IsUnresolvedTypes() ? VERIFY_ERROR_NO_CLASS : VERIFY_ERROR_BAD_CLASS_SOFT)
             << "thrown class " << res_type << " not instanceof Throwable";
@@ -1877,14 +1877,14 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
 
     case Instruction::FILL_ARRAY_DATA: {
       /* Similar to the verification done for APUT */
-      RegType& array_type = work_line_->GetRegisterType(inst->VRegA_31t());
+      const RegType& array_type = work_line_->GetRegisterType(inst->VRegA_31t());
       /* array_type can be null if the reg type is Zero */
       if (!array_type.IsZero()) {
         if (!array_type.IsArrayTypes()) {
           Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "invalid fill-array-data with array type "
                                             << array_type;
         } else {
-          RegType& component_type = reg_types_.GetComponentType(array_type, GetClassLoader());
+          const RegType& component_type = reg_types_.GetComponentType(array_type, GetClassLoader());
           DCHECK(!component_type.IsConflict());
           if (component_type.IsNonZeroReferenceTypes()) {
             Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "invalid fill-array-data with component type "
@@ -1911,8 +1911,8 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
     }
     case Instruction::IF_EQ:
     case Instruction::IF_NE: {
-      RegType& reg_type1 = work_line_->GetRegisterType(inst->VRegA_22t());
-      RegType& reg_type2 = work_line_->GetRegisterType(inst->VRegB_22t());
+      const RegType& reg_type1 = work_line_->GetRegisterType(inst->VRegA_22t());
+      const RegType& reg_type2 = work_line_->GetRegisterType(inst->VRegB_22t());
       bool mismatch = false;
       if (reg_type1.IsZero()) {  // zero then integral or reference expected
         mismatch = !reg_type2.IsReferenceTypes() && !reg_type2.IsIntegralTypes();
@@ -1931,8 +1931,8 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
     case Instruction::IF_GE:
     case Instruction::IF_GT:
     case Instruction::IF_LE: {
-      RegType& reg_type1 = work_line_->GetRegisterType(inst->VRegA_22t());
-      RegType& reg_type2 = work_line_->GetRegisterType(inst->VRegB_22t());
+      const RegType& reg_type1 = work_line_->GetRegisterType(inst->VRegA_22t());
+      const RegType& reg_type2 = work_line_->GetRegisterType(inst->VRegB_22t());
       if (!reg_type1.IsIntegralTypes() || !reg_type2.IsIntegralTypes()) {
         Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "args to 'if' (" << reg_type1 << ","
                                           << reg_type2 << ") must be integral";
@@ -1941,7 +1941,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
     }
     case Instruction::IF_EQZ:
     case Instruction::IF_NEZ: {
-      RegType& reg_type = work_line_->GetRegisterType(inst->VRegA_21t());
+      const RegType& reg_type = work_line_->GetRegisterType(inst->VRegA_21t());
       if (!reg_type.IsReferenceTypes() && !reg_type.IsIntegralTypes()) {
         Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "type " << reg_type
                                           << " unexpected as arg to if-eqz/if-nez";
@@ -1987,8 +1987,8 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
         // type is assignable to the original then allow optimization. This check is performed to
         // ensure that subsequent merges don't lose type information - such as becoming an
         // interface from a class that would lose information relevant to field checks.
-        RegType& orig_type = work_line_->GetRegisterType(instance_of_inst->VRegB_22c());
-        RegType& cast_type = ResolveClassAndCheckAccess(instance_of_inst->VRegC_22c());
+        const RegType& orig_type = work_line_->GetRegisterType(instance_of_inst->VRegB_22c());
+        const RegType& cast_type = ResolveClassAndCheckAccess(instance_of_inst->VRegC_22c());
 
         if (!orig_type.Equals(cast_type) &&
             !cast_type.IsUnresolvedTypes() && !orig_type.IsUnresolvedTypes() &&
@@ -2043,7 +2043,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
     case Instruction::IF_GEZ:
     case Instruction::IF_GTZ:
     case Instruction::IF_LEZ: {
-      RegType& reg_type = work_line_->GetRegisterType(inst->VRegA_21t());
+      const RegType& reg_type = work_line_->GetRegisterType(inst->VRegA_21t());
       if (!reg_type.IsIntegralTypes()) {
         Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "type " << reg_type
                                           << " unexpected as arg to if-ltz/if-gez/if-gtz/if-lez";
@@ -2192,7 +2192,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
                        inst->Opcode() == Instruction::INVOKE_SUPER_RANGE);
       mirror::ArtMethod* called_method = VerifyInvocationArgs(inst, METHOD_VIRTUAL, is_range,
                                                               is_super);
-      RegType* return_type = nullptr;
+      const RegType* return_type = nullptr;
       if (called_method != nullptr) {
         Thread* self = Thread::Current();
         StackHandleScope<1> hs(self);
@@ -2230,7 +2230,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
                                                                    is_range, false);
       const char* return_type_descriptor;
       bool is_constructor;
-      RegType* return_type = nullptr;
+      const RegType* return_type = nullptr;
       if (called_method == NULL) {
         uint32_t method_idx = (is_range) ? inst->VRegB_3rc() : inst->VRegB_35c();
         const DexFile::MethodId& method_id = dex_file_->GetMethodId(method_idx);
@@ -2262,7 +2262,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
          * allowing the latter only if the "this" argument is the same as the "this" argument to
          * this method (which implies that we're in a constructor ourselves).
          */
-        RegType& this_type = work_line_->GetInvocationThis(inst, is_range);
+        const RegType& this_type = work_line_->GetInvocationThis(inst, is_range);
         if (this_type.IsConflict())  // failure.
           break;
 
@@ -2273,7 +2273,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
         }
 
         /* must be in same class or in superclass */
-        // RegType& this_super_klass = this_type.GetSuperClass(&reg_types_);
+        // const RegType& this_super_klass = this_type.GetSuperClass(&reg_types_);
         // TODO: re-enable constructor type verification
         // if (this_super_klass.IsConflict()) {
           // Unknown super class, fail so we re-check at runtime.
@@ -2322,7 +2322,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
         } else {
           descriptor = called_method->GetReturnTypeDescriptor();
         }
-        RegType& return_type = reg_types_.FromDescriptor(GetClassLoader(), descriptor, false);
+        const RegType& return_type = reg_types_.FromDescriptor(GetClassLoader(), descriptor, false);
         if (!return_type.IsLowHalf()) {
           work_line_->SetResultRegisterType(return_type);
         } else {
@@ -2349,7 +2349,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
       /* Get the type of the "this" arg, which should either be a sub-interface of called
        * interface or Object (see comments in RegType::JoinClass).
        */
-      RegType& this_type = work_line_->GetInvocationThis(inst, is_range);
+      const RegType& this_type = work_line_->GetInvocationThis(inst, is_range);
       if (this_type.IsZero()) {
         /* null pointer always passes (and always fails at runtime) */
       } else {
@@ -2379,7 +2379,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
       } else {
         descriptor = abs_method->GetReturnTypeDescriptor();
       }
-      RegType& return_type = reg_types_.FromDescriptor(GetClassLoader(), descriptor, false);
+      const RegType& return_type = reg_types_.FromDescriptor(GetClassLoader(), descriptor, false);
       if (!return_type.IsLowHalf()) {
         work_line_->SetResultRegisterType(return_type);
       } else {
@@ -2656,7 +2656,7 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
       mirror::ArtMethod* called_method = VerifyInvokeVirtualQuickArgs(inst, is_range);
       if (called_method != NULL) {
         const char* descriptor = called_method->GetReturnTypeDescriptor();
-        RegType& return_type = reg_types_.FromDescriptor(GetClassLoader(), descriptor, false);
+        const RegType& return_type = reg_types_.FromDescriptor(GetClassLoader(), descriptor, false);
         if (!return_type.IsLowHalf()) {
           work_line_->SetResultRegisterType(return_type);
         } else {
@@ -2935,11 +2935,11 @@ bool MethodVerifier::CodeFlowVerifyInstruction(uint32_t* start_guess) {
   return true;
 }  // NOLINT(readability/fn_size)
 
-RegType& MethodVerifier::ResolveClassAndCheckAccess(uint32_t class_idx) {
+const RegType& MethodVerifier::ResolveClassAndCheckAccess(uint32_t class_idx) {
   const char* descriptor = dex_file_->StringByTypeIdx(class_idx);
-  RegType& referrer = GetDeclaringClass();
+  const RegType& referrer = GetDeclaringClass();
   mirror::Class* klass = dex_cache_->GetResolvedType(class_idx);
-  RegType& result = klass != NULL ?
+  const RegType& result = klass != NULL ?
       reg_types_.FromClass(descriptor, klass, klass->CannotBeAssignedFromOtherTypes()) :
       reg_types_.FromDescriptor(GetClassLoader(), descriptor, false);
   if (result.IsConflict()) {
@@ -2961,8 +2961,8 @@ RegType& MethodVerifier::ResolveClassAndCheckAccess(uint32_t class_idx) {
   return result;
 }
 
-RegType& MethodVerifier::GetCaughtExceptionType() {
-  RegType* common_super = NULL;
+const RegType& MethodVerifier::GetCaughtExceptionType() {
+  const RegType* common_super = NULL;
   if (code_item_->tries_size_ != 0) {
     const byte* handlers_ptr = DexFile::GetCatchHandlerData(*code_item_, 0);
     uint32_t handlers_size = DecodeUnsignedLeb128(&handlers_ptr);
@@ -2973,7 +2973,7 @@ RegType& MethodVerifier::GetCaughtExceptionType() {
           if (iterator.GetHandlerTypeIndex() == DexFile::kDexNoIndex16) {
             common_super = &reg_types_.JavaLangThrowable(false);
           } else {
-            RegType& exception = ResolveClassAndCheckAccess(iterator.GetHandlerTypeIndex());
+            const RegType& exception = ResolveClassAndCheckAccess(iterator.GetHandlerTypeIndex());
             if (!reg_types_.JavaLangThrowable(false).IsAssignableFrom(exception)) {
               if (exception.IsUnresolvedTypes()) {
                 // We don't know enough about the type. Fail here and let runtime handle it.
@@ -3008,7 +3008,7 @@ RegType& MethodVerifier::GetCaughtExceptionType() {
 mirror::ArtMethod* MethodVerifier::ResolveMethodAndCheckAccess(uint32_t dex_method_idx,
                                                                MethodType method_type) {
   const DexFile::MethodId& method_id = dex_file_->GetMethodId(dex_method_idx);
-  RegType& klass_type = ResolveClassAndCheckAccess(method_id.class_idx_);
+  const RegType& klass_type = ResolveClassAndCheckAccess(method_id.class_idx_);
   if (klass_type.IsConflict()) {
     std::string append(" in attempt to access method ");
     append += dex_file_->GetMethodName(method_id);
@@ -3019,7 +3019,7 @@ mirror::ArtMethod* MethodVerifier::ResolveMethodAndCheckAccess(uint32_t dex_meth
     return NULL;  // Can't resolve Class so no more to do here
   }
   mirror::Class* klass = klass_type.GetClass();
-  RegType& referrer = GetDeclaringClass();
+  const RegType& referrer = GetDeclaringClass();
   mirror::ArtMethod* res_method = dex_cache_->GetResolvedMethod(dex_method_idx);
   if (res_method == NULL) {
     const char* name = dex_file_->GetMethodName(method_id);
@@ -3126,7 +3126,7 @@ mirror::ArtMethod* MethodVerifier::VerifyInvocationArgsFromIterator(T* it, const
    * rigorous check here (which is okay since we have to do it at runtime).
    */
   if (method_type != METHOD_STATIC) {
-    RegType& actual_arg_type = work_line_->GetInvocationThis(inst, is_range);
+    const RegType& actual_arg_type = work_line_->GetInvocationThis(inst, is_range);
     if (actual_arg_type.IsConflict()) {  // GetInvocationThis failed.
       CHECK(have_pending_hard_failure_);
       return nullptr;
@@ -3147,7 +3147,7 @@ mirror::ArtMethod* MethodVerifier::VerifyInvocationArgsFromIterator(T* it, const
       }
     }
     if (method_type != METHOD_INTERFACE && !actual_arg_type.IsZero()) {
-      RegType* res_method_class;
+      const RegType* res_method_class;
       if (res_method != nullptr) {
         mirror::Class* klass = res_method->GetDeclaringClass();
         std::string temp;
@@ -3189,11 +3189,11 @@ mirror::ArtMethod* MethodVerifier::VerifyInvocationArgsFromIterator(T* it, const
       return nullptr;
     }
 
-    RegType& reg_type = reg_types_.FromDescriptor(GetClassLoader(), param_descriptor, false);
+    const RegType& reg_type = reg_types_.FromDescriptor(GetClassLoader(), param_descriptor, false);
     uint32_t get_reg = is_range ? inst->VRegC_3rc() + static_cast<uint32_t>(sig_registers) :
         arg[sig_registers];
     if (reg_type.IsIntegralTypes()) {
-      RegType& src_type = work_line_->GetRegisterType(get_reg);
+      const RegType& src_type = work_line_->GetRegisterType(get_reg);
       if (!src_type.IsIntegralTypes()) {
         Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "register v" << get_reg << " has type " << src_type
             << " but expected " << reg_type;
@@ -3276,7 +3276,7 @@ mirror::ArtMethod* MethodVerifier::VerifyInvocationArgs(const Instruction* inst,
   // has a vtable entry for the target method.
   if (is_super) {
     DCHECK(method_type == METHOD_VIRTUAL);
-    RegType& super = GetDeclaringClass().GetSuperClass(&reg_types_);
+    const RegType& super = GetDeclaringClass().GetSuperClass(&reg_types_);
     if (super.IsUnresolvedTypes()) {
       Fail(VERIFY_ERROR_NO_METHOD) << "unknown super class in invoke-super from "
                                    << PrettyMethod(dex_method_idx_, *dex_file_)
@@ -3304,7 +3304,7 @@ mirror::ArtMethod* MethodVerifier::GetQuickInvokedMethod(const Instruction* inst
                                                          RegisterLine* reg_line, bool is_range) {
   DCHECK(inst->Opcode() == Instruction::INVOKE_VIRTUAL_QUICK ||
          inst->Opcode() == Instruction::INVOKE_VIRTUAL_RANGE_QUICK);
-  RegType& actual_arg_type = reg_line->GetInvocationThis(inst, is_range);
+  const RegType& actual_arg_type = reg_line->GetInvocationThis(inst, is_range);
   if (!actual_arg_type.HasClass()) {
     VLOG(verifier) << "Failed to get mirror::Class* from '" << actual_arg_type << "'";
     return nullptr;
@@ -3342,7 +3342,7 @@ mirror::ArtMethod* MethodVerifier::VerifyInvokeVirtualQuickArgs(const Instructio
   // We use vAA as our expected arg count, rather than res_method->insSize, because we need to
   // match the call to the signature. Also, we might be calling through an abstract method
   // definition (which doesn't have register count values).
-  RegType& actual_arg_type = work_line_->GetInvocationThis(inst, is_range);
+  const RegType& actual_arg_type = work_line_->GetInvocationThis(inst, is_range);
   if (actual_arg_type.IsConflict()) {  // GetInvocationThis failed.
     return NULL;
   }
@@ -3367,7 +3367,7 @@ mirror::ArtMethod* MethodVerifier::VerifyInvokeVirtualQuickArgs(const Instructio
   if (!actual_arg_type.IsZero()) {
     mirror::Class* klass = res_method->GetDeclaringClass();
     std::string temp;
-    RegType& res_method_class =
+    const RegType& res_method_class =
         reg_types_.FromClass(klass->GetDescriptor(&temp), klass,
                              klass->CannotBeAssignedFromOtherTypes());
     if (!res_method_class.IsAssignableFrom(actual_arg_type)) {
@@ -3403,7 +3403,7 @@ mirror::ArtMethod* MethodVerifier::VerifyInvokeVirtualQuickArgs(const Instructio
                                         << " missing signature component";
       return NULL;
     }
-    RegType& reg_type = reg_types_.FromDescriptor(GetClassLoader(), descriptor, false);
+    const RegType& reg_type = reg_types_.FromDescriptor(GetClassLoader(), descriptor, false);
     uint32_t get_reg = is_range ? inst->VRegC_3rc() + actual_args : arg[actual_args];
     if (!work_line_->VerifyRegisterType(get_reg, reg_type)) {
       return res_method;
@@ -3431,7 +3431,7 @@ void MethodVerifier::VerifyNewArray(const Instruction* inst, bool is_filled, boo
     DCHECK_EQ(inst->Opcode(), Instruction::FILLED_NEW_ARRAY_RANGE);
     type_idx = inst->VRegB_3rc();
   }
-  RegType& res_type = ResolveClassAndCheckAccess(type_idx);
+  const RegType& res_type = ResolveClassAndCheckAccess(type_idx);
   if (res_type.IsConflict()) {  // bad class
     DCHECK_NE(failures_.size(), 0U);
   } else {
@@ -3442,12 +3442,12 @@ void MethodVerifier::VerifyNewArray(const Instruction* inst, bool is_filled, boo
       /* make sure "size" register is valid type */
       work_line_->VerifyRegisterType(inst->VRegB_22c(), reg_types_.Integer());
       /* set register type to array class */
-      RegType& precise_type = reg_types_.FromUninitialized(res_type);
+      const RegType& precise_type = reg_types_.FromUninitialized(res_type);
       work_line_->SetRegisterType(inst->VRegA_22c(), precise_type);
     } else {
       // Verify each register. If "arg_count" is bad, VerifyRegisterType() will run off the end of
       // the list and fail. It's legal, if silly, for arg_count to be zero.
-      RegType& expected_type = reg_types_.GetComponentType(res_type, GetClassLoader());
+      const RegType& expected_type = reg_types_.GetComponentType(res_type, GetClassLoader());
       uint32_t arg_count = (is_range) ? inst->VRegA_3rc() : inst->VRegA_35c();
       uint32_t arg[5];
       if (!is_range) {
@@ -3461,19 +3461,19 @@ void MethodVerifier::VerifyNewArray(const Instruction* inst, bool is_filled, boo
         }
       }
       // filled-array result goes into "result" register
-      RegType& precise_type = reg_types_.FromUninitialized(res_type);
+      const RegType& precise_type = reg_types_.FromUninitialized(res_type);
       work_line_->SetResultRegisterType(precise_type);
     }
   }
 }
 
 void MethodVerifier::VerifyAGet(const Instruction* inst,
-                                RegType& insn_type, bool is_primitive) {
-  RegType& index_type = work_line_->GetRegisterType(inst->VRegC_23x());
+                                const RegType& insn_type, bool is_primitive) {
+  const RegType& index_type = work_line_->GetRegisterType(inst->VRegC_23x());
   if (!index_type.IsArrayIndexTypes()) {
     Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "Invalid reg type for array index (" << index_type << ")";
   } else {
-    RegType& array_type = work_line_->GetRegisterType(inst->VRegB_23x());
+    const RegType& array_type = work_line_->GetRegisterType(inst->VRegB_23x());
     if (array_type.IsZero()) {
       // Null array class; this code path will fail at runtime. Infer a merge-able type from the
       // instruction type. TODO: have a proper notion of bottom here.
@@ -3489,7 +3489,7 @@ void MethodVerifier::VerifyAGet(const Instruction* inst,
       Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "not array type " << array_type << " with aget";
     } else {
       /* verify the class */
-      RegType& component_type = reg_types_.GetComponentType(array_type, GetClassLoader());
+      const RegType& component_type = reg_types_.GetComponentType(array_type, GetClassLoader());
       if (!component_type.IsReferenceTypes() && !is_primitive) {
         Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "primitive array type " << array_type
             << " source for aget-object";
@@ -3516,12 +3516,12 @@ void MethodVerifier::VerifyAGet(const Instruction* inst,
   }
 }
 
-void MethodVerifier::VerifyPrimitivePut(RegType& target_type, RegType& insn_type,
+void MethodVerifier::VerifyPrimitivePut(const RegType& target_type, const RegType& insn_type,
                                         const uint32_t vregA) {
   // Primitive assignability rules are weaker than regular assignability rules.
   bool instruction_compatible;
   bool value_compatible;
-  RegType& value_type = work_line_->GetRegisterType(vregA);
+  const RegType& value_type = work_line_->GetRegisterType(vregA);
   if (target_type.IsIntegralTypes()) {
     instruction_compatible = target_type.Equals(insn_type);
     value_compatible = value_type.IsIntegralTypes();
@@ -3533,7 +3533,7 @@ void MethodVerifier::VerifyPrimitivePut(RegType& target_type, RegType& insn_type
     // Additional register check: this is not checked statically (as part of VerifyInstructions),
     // as target_type depends on the resolved type of the field.
     if (instruction_compatible && work_line_->NumRegs() > vregA + 1) {
-      RegType& value_type_hi = work_line_->GetRegisterType(vregA + 1);
+      const RegType& value_type_hi = work_line_->GetRegisterType(vregA + 1);
       value_compatible = value_type.IsLongTypes() && value_type.CheckWidePair(value_type_hi);
     } else {
       value_compatible = false;
@@ -3543,7 +3543,7 @@ void MethodVerifier::VerifyPrimitivePut(RegType& target_type, RegType& insn_type
     // Additional register check: this is not checked statically (as part of VerifyInstructions),
     // as target_type depends on the resolved type of the field.
     if (instruction_compatible && work_line_->NumRegs() > vregA + 1) {
-      RegType& value_type_hi = work_line_->GetRegisterType(vregA + 1);
+      const RegType& value_type_hi = work_line_->GetRegisterType(vregA + 1);
       value_compatible = value_type.IsDoubleTypes() && value_type.CheckWidePair(value_type_hi);
     } else {
       value_compatible = false;
@@ -3568,19 +3568,19 @@ void MethodVerifier::VerifyPrimitivePut(RegType& target_type, RegType& insn_type
 }
 
 void MethodVerifier::VerifyAPut(const Instruction* inst,
-                                RegType& insn_type, bool is_primitive) {
-  RegType& index_type = work_line_->GetRegisterType(inst->VRegC_23x());
+                                const RegType& insn_type, bool is_primitive) {
+  const RegType& index_type = work_line_->GetRegisterType(inst->VRegC_23x());
   if (!index_type.IsArrayIndexTypes()) {
     Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "Invalid reg type for array index (" << index_type << ")";
   } else {
-    RegType& array_type = work_line_->GetRegisterType(inst->VRegB_23x());
+    const RegType& array_type = work_line_->GetRegisterType(inst->VRegB_23x());
     if (array_type.IsZero()) {
       // Null array type; this code path will fail at runtime. Infer a merge-able type from the
       // instruction type.
     } else if (!array_type.IsArrayTypes()) {
       Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "not array type " << array_type << " with aput";
     } else {
-      RegType& component_type = reg_types_.GetComponentType(array_type, GetClassLoader());
+      const RegType& component_type = reg_types_.GetComponentType(array_type, GetClassLoader());
       const uint32_t vregA = inst->VRegA_23x();
       if (is_primitive) {
         VerifyPrimitivePut(component_type, insn_type, vregA);
@@ -3602,7 +3602,7 @@ void MethodVerifier::VerifyAPut(const Instruction* inst,
 mirror::ArtField* MethodVerifier::GetStaticField(int field_idx) {
   const DexFile::FieldId& field_id = dex_file_->GetFieldId(field_idx);
   // Check access to class
-  RegType& klass_type = ResolveClassAndCheckAccess(field_id.class_idx_);
+  const RegType& klass_type = ResolveClassAndCheckAccess(field_id.class_idx_);
   if (klass_type.IsConflict()) {  // bad class
     AppendToLastFailMessage(StringPrintf(" in attempt to access static field %d (%s) in %s",
                                          field_idx, dex_file_->GetFieldName(field_id),
@@ -3634,10 +3634,10 @@ mirror::ArtField* MethodVerifier::GetStaticField(int field_idx) {
   return field;
 }
 
-mirror::ArtField* MethodVerifier::GetInstanceField(RegType& obj_type, int field_idx) {
+mirror::ArtField* MethodVerifier::GetInstanceField(const RegType& obj_type, int field_idx) {
   const DexFile::FieldId& field_id = dex_file_->GetFieldId(field_idx);
   // Check access to class
-  RegType& klass_type = ResolveClassAndCheckAccess(field_id.class_idx_);
+  const RegType& klass_type = ResolveClassAndCheckAccess(field_id.class_idx_);
   if (klass_type.IsConflict()) {
     AppendToLastFailMessage(StringPrintf(" in attempt to access instance field %d (%s) in %s",
                                          field_idx, dex_file_->GetFieldName(field_id),
@@ -3676,7 +3676,7 @@ mirror::ArtField* MethodVerifier::GetInstanceField(RegType& obj_type, int field_
     return NULL;
   } else {
     mirror::Class* klass = field->GetDeclaringClass();
-    RegType& field_klass =
+    const RegType& field_klass =
         reg_types_.FromClass(dex_file_->GetFieldDeclaringClassDescriptor(field_id),
                              klass, klass->CannotBeAssignedFromOtherTypes());
     if (obj_type.IsUninitializedTypes() &&
@@ -3701,17 +3701,17 @@ mirror::ArtField* MethodVerifier::GetInstanceField(RegType& obj_type, int field_
   }
 }
 
-void MethodVerifier::VerifyISGet(const Instruction* inst, RegType& insn_type,
+void MethodVerifier::VerifyISGet(const Instruction* inst, const RegType& insn_type,
                                  bool is_primitive, bool is_static) {
   uint32_t field_idx = is_static ? inst->VRegB_21c() : inst->VRegC_22c();
   mirror::ArtField* field;
   if (is_static) {
     field = GetStaticField(field_idx);
   } else {
-    RegType& object_type = work_line_->GetRegisterType(inst->VRegB_22c());
+    const RegType& object_type = work_line_->GetRegisterType(inst->VRegB_22c());
     field = GetInstanceField(object_type, field_idx);
   }
-  RegType* field_type = nullptr;
+  const RegType* field_type = nullptr;
   if (field != NULL) {
     Thread* self = Thread::Current();
     mirror::Class* field_type_class;
@@ -3767,17 +3767,17 @@ void MethodVerifier::VerifyISGet(const Instruction* inst, RegType& insn_type,
   }
 }
 
-void MethodVerifier::VerifyISPut(const Instruction* inst, RegType& insn_type,
+void MethodVerifier::VerifyISPut(const Instruction* inst, const RegType& insn_type,
                                  bool is_primitive, bool is_static) {
   uint32_t field_idx = is_static ? inst->VRegB_21c() : inst->VRegC_22c();
   mirror::ArtField* field;
   if (is_static) {
     field = GetStaticField(field_idx);
   } else {
-    RegType& object_type = work_line_->GetRegisterType(inst->VRegB_22c());
+    const RegType& object_type = work_line_->GetRegisterType(inst->VRegB_22c());
     field = GetInstanceField(object_type, field_idx);
   }
-  RegType* field_type = nullptr;
+  const RegType* field_type = nullptr;
   if (field != NULL) {
     if (field->IsFinal() && field->GetDeclaringClass() != GetDeclaringClass().GetClass()) {
       Fail(VERIFY_ERROR_ACCESS_FIELD) << "cannot modify final field " << PrettyField(field)
@@ -3829,7 +3829,7 @@ mirror::ArtField* MethodVerifier::GetQuickFieldAccess(const Instruction* inst,
          inst->Opcode() == Instruction::IPUT_QUICK ||
          inst->Opcode() == Instruction::IPUT_WIDE_QUICK ||
          inst->Opcode() == Instruction::IPUT_OBJECT_QUICK);
-  RegType& object_type = reg_line->GetRegisterType(inst->VRegB_22c());
+  const RegType& object_type = reg_line->GetRegisterType(inst->VRegB_22c());
   if (!object_type.HasClass()) {
     VLOG(verifier) << "Failed to get mirror::Class* from '" << object_type << "'";
     return nullptr;
@@ -3844,7 +3844,7 @@ mirror::ArtField* MethodVerifier::GetQuickFieldAccess(const Instruction* inst,
   return f;
 }
 
-void MethodVerifier::VerifyIGetQuick(const Instruction* inst, RegType& insn_type,
+void MethodVerifier::VerifyIGetQuick(const Instruction* inst, const RegType& insn_type,
                                      bool is_primitive) {
   DCHECK(Runtime::Current()->IsStarted());
   mirror::ArtField* field = GetQuickFieldAccess(inst, work_line_.get());
@@ -3859,7 +3859,7 @@ void MethodVerifier::VerifyIGetQuick(const Instruction* inst, RegType& insn_type
     FieldHelper fh(h_field);
     field_type_class = fh.GetType(can_load_classes_);
   }
-  RegType* field_type;
+  const RegType* field_type;
   if (field_type_class != nullptr) {
     field_type = &reg_types_.FromClass(field->GetTypeDescriptor(), field_type_class,
                                        field_type_class->CannotBeAssignedFromOtherTypes());
@@ -3904,7 +3904,7 @@ void MethodVerifier::VerifyIGetQuick(const Instruction* inst, RegType& insn_type
   }
 }
 
-void MethodVerifier::VerifyIPutQuick(const Instruction* inst, RegType& insn_type,
+void MethodVerifier::VerifyIPutQuick(const Instruction* inst, const RegType& insn_type,
                                      bool is_primitive) {
   DCHECK(Runtime::Current()->IsStarted());
   mirror::ArtField* field = GetQuickFieldAccess(inst, work_line_.get());
@@ -3914,7 +3914,7 @@ void MethodVerifier::VerifyIPutQuick(const Instruction* inst, RegType& insn_type
   }
   const char* descriptor = field->GetTypeDescriptor();
   mirror::ClassLoader* loader = field->GetDeclaringClass()->GetClassLoader();
-  RegType& field_type = reg_types_.FromDescriptor(loader, descriptor, false);
+  const RegType& field_type = reg_types_.FromDescriptor(loader, descriptor, false);
   if (field != NULL) {
     if (field->IsFinal() && field->GetDeclaringClass() != GetDeclaringClass().GetClass()) {
       Fail(VERIFY_ERROR_ACCESS_FIELD) << "cannot modify final field " << PrettyField(field)
@@ -3927,7 +3927,7 @@ void MethodVerifier::VerifyIPutQuick(const Instruction* inst, RegType& insn_type
     // Primitive field assignability rules are weaker than regular assignability rules
     bool instruction_compatible;
     bool value_compatible;
-    RegType& value_type = work_line_->GetRegisterType(vregA);
+    const RegType& value_type = work_line_->GetRegisterType(vregA);
     if (field_type.IsIntegralTypes()) {
       instruction_compatible = insn_type.IsIntegralTypes();
       value_compatible = value_type.IsIntegralTypes();
@@ -4045,7 +4045,7 @@ InstructionFlags* MethodVerifier::CurrentInsnFlags() {
   return &insn_flags_[work_insn_idx_];
 }
 
-RegType& MethodVerifier::GetMethodReturnType() {
+const RegType& MethodVerifier::GetMethodReturnType() {
   if (return_type_ == nullptr) {
     if (mirror_method_.Get() != nullptr) {
       Thread* self = Thread::Current();
@@ -4072,7 +4072,7 @@ RegType& MethodVerifier::GetMethodReturnType() {
   return *return_type_;
 }
 
-RegType& MethodVerifier::GetDeclaringClass() {
+const RegType& MethodVerifier::GetDeclaringClass() {
   if (declaring_class_ == NULL) {
     const DexFile::MethodId& method_id = dex_file_->GetMethodId(dex_method_idx_);
     const char* descriptor
@@ -4093,7 +4093,7 @@ std::vector<int32_t> MethodVerifier::DescribeVRegs(uint32_t dex_pc) {
   DCHECK(line != nullptr) << "No register line at DEX pc " << StringPrintf("0x%x", dex_pc);
   std::vector<int32_t> result;
   for (size_t i = 0; i < line->NumRegs(); ++i) {
-    RegType& type = line->GetRegisterType(i);
+    const RegType& type = line->GetRegisterType(i);
     if (type.IsConstant()) {
       result.push_back(type.IsPreciseConstant() ? kConstant : kImpreciseConstant);
       result.push_back(type.ConstantValue());
@@ -4133,7 +4133,7 @@ std::vector<int32_t> MethodVerifier::DescribeVRegs(uint32_t dex_pc) {
   return result;
 }
 
-RegType& MethodVerifier::DetermineCat1Constant(int32_t value, bool precise) {
+const RegType& MethodVerifier::DetermineCat1Constant(int32_t value, bool precise) {
   if (precise) {
     // Precise constant type.
     return reg_types_.FromCat1Const(value, true);
diff --git a/runtime/verifier/method_verifier.h b/runtime/verifier/method_verifier.h
index af33414..45c0a03 100644
--- a/runtime/verifier/method_verifier.h
+++ b/runtime/verifier/method_verifier.h
@@ -232,7 +232,7 @@ class MethodVerifier {
   bool HasCheckCasts() const;
   bool HasVirtualOrInterfaceInvokes() const;
   bool HasFailures() const;
-  RegType& ResolveCheckedClass(uint32_t class_idx)
+  const RegType& ResolveCheckedClass(uint32_t class_idx)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
  private:
@@ -473,34 +473,34 @@ class MethodVerifier {
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Helper to perform verification on puts of primitive type.
-  void VerifyPrimitivePut(RegType& target_type, RegType& insn_type,
+  void VerifyPrimitivePut(const RegType& target_type, const RegType& insn_type,
                           const uint32_t vregA) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Perform verification of an aget instruction. The destination register's type will be set to
   // be that of component type of the array unless the array type is unknown, in which case a
   // bottom type inferred from the type of instruction is used. is_primitive is false for an
   // aget-object.
-  void VerifyAGet(const Instruction* inst, RegType& insn_type,
+  void VerifyAGet(const Instruction* inst, const RegType& insn_type,
                   bool is_primitive) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Perform verification of an aput instruction.
-  void VerifyAPut(const Instruction* inst, RegType& insn_type,
+  void VerifyAPut(const Instruction* inst, const RegType& insn_type,
                   bool is_primitive) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Lookup instance field and fail for resolution violations
-  mirror::ArtField* GetInstanceField(RegType& obj_type, int field_idx)
+  mirror::ArtField* GetInstanceField(const RegType& obj_type, int field_idx)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Lookup static field and fail for resolution violations
   mirror::ArtField* GetStaticField(int field_idx) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Perform verification of an iget or sget instruction.
-  void VerifyISGet(const Instruction* inst, RegType& insn_type,
+  void VerifyISGet(const Instruction* inst, const RegType& insn_type,
                    bool is_primitive, bool is_static)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Perform verification of an iput or sput instruction.
-  void VerifyISPut(const Instruction* inst, RegType& insn_type,
+  void VerifyISPut(const Instruction* inst, const RegType& insn_type,
                    bool is_primitive, bool is_static)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
@@ -510,18 +510,18 @@ class MethodVerifier {
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Perform verification of an iget-quick instruction.
-  void VerifyIGetQuick(const Instruction* inst, RegType& insn_type,
+  void VerifyIGetQuick(const Instruction* inst, const RegType& insn_type,
                        bool is_primitive)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Perform verification of an iput-quick instruction.
-  void VerifyIPutQuick(const Instruction* inst, RegType& insn_type,
+  void VerifyIPutQuick(const Instruction* inst, const RegType& insn_type,
                        bool is_primitive)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Resolves a class based on an index and performs access checks to ensure the referrer can
   // access the resolved class.
-  RegType& ResolveClassAndCheckAccess(uint32_t class_idx)
+  const RegType& ResolveClassAndCheckAccess(uint32_t class_idx)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   /*
@@ -529,7 +529,7 @@ class MethodVerifier {
    * address, determine the Join of all exceptions that can land here. Fails if no matching
    * exception handler can be found or if the Join of exception types fails.
    */
-  RegType& GetCaughtExceptionType()
+  const RegType& GetCaughtExceptionType()
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   /*
@@ -615,14 +615,14 @@ class MethodVerifier {
   }
 
   // Return the register type for the method.
-  RegType& GetMethodReturnType() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  const RegType& GetMethodReturnType() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Get a type representing the declaring class of the method.
-  RegType& GetDeclaringClass() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  const RegType& GetDeclaringClass() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   InstructionFlags* CurrentInsnFlags();
 
-  RegType& DetermineCat1Constant(int32_t value, bool precise)
+  const RegType& DetermineCat1Constant(int32_t value, bool precise)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   RegTypeCache reg_types_;
@@ -643,7 +643,7 @@ class MethodVerifier {
   // Its object representation if known.
   ConstHandle<mirror::ArtMethod> mirror_method_ GUARDED_BY(Locks::mutator_lock_);
   const uint32_t method_access_flags_;  // Method's access flags.
-  RegType* return_type_;  // Lazily computed return type of the method.
+  const RegType* return_type_;  // Lazily computed return type of the method.
   const DexFile* const dex_file_;  // The dex file containing the method.
   // The dex_cache for the declaring class of the method.
   ConstHandle<mirror::DexCache> dex_cache_ GUARDED_BY(Locks::mutator_lock_);
@@ -651,7 +651,7 @@ class MethodVerifier {
   ConstHandle<mirror::ClassLoader> class_loader_ GUARDED_BY(Locks::mutator_lock_);
   const DexFile::ClassDef* const class_def_;  // The class def of the declaring class of the method.
   const DexFile::CodeItem* const code_item_;  // The code item containing the code for the method.
-  RegType* declaring_class_;  // Lazily computed reg type of the method's declaring class.
+  const RegType* declaring_class_;  // Lazily computed reg type of the method's declaring class.
   // Instruction widths and flags, one entry per code unit.
   std::unique_ptr<InstructionFlags[]> insn_flags_;
   // The dex PC of a FindLocksAtDexPc request, -1 otherwise.
diff --git a/runtime/verifier/reg_type.cc b/runtime/verifier/reg_type.cc
index 30be82f..197b120 100644
--- a/runtime/verifier/reg_type.cc
+++ b/runtime/verifier/reg_type.cc
@@ -81,7 +81,7 @@ Cat2Type::Cat2Type(mirror::Class* klass, const std::string& descriptor, uint16_t
     : PrimitiveType(klass, descriptor, cache_id) {
 }
 
-std::string PreciseConstType::Dump() {
+std::string PreciseConstType::Dump() const {
   std::stringstream result;
   uint32_t val = ConstantValue();
   if (val == 0) {
@@ -98,47 +98,47 @@ std::string PreciseConstType::Dump() {
   return result.str();
 }
 
-std::string BooleanType::Dump() {
+std::string BooleanType::Dump() const {
   return "Boolean";
 }
 
-std::string ConflictType::Dump() {
+std::string ConflictType::Dump() const {
     return "Conflict";
 }
 
-std::string ByteType::Dump() {
+std::string ByteType::Dump() const {
   return "Byte";
 }
 
-std::string ShortType::Dump() {
+std::string ShortType::Dump() const {
   return "Short";
 }
 
-std::string CharType::Dump() {
+std::string CharType::Dump() const {
   return "Char";
 }
 
-std::string FloatType::Dump() {
+std::string FloatType::Dump() const {
   return "Float";
 }
 
-std::string LongLoType::Dump() {
+std::string LongLoType::Dump() const {
   return "Long (Low Half)";
 }
 
-std::string LongHiType::Dump() {
+std::string LongHiType::Dump() const {
   return "Long (High Half)";
 }
 
-std::string DoubleLoType::Dump() {
+std::string DoubleLoType::Dump() const {
   return "Double (Low Half)";
 }
 
-std::string DoubleHiType::Dump() {
+std::string DoubleHiType::Dump() const {
   return "Double (High Half)";
 }
 
-std::string IntegerType::Dump() {
+std::string IntegerType::Dump() const {
     return "Integer";
 }
 
@@ -361,7 +361,7 @@ void BooleanType::Destroy() {
   }
 }
 
-std::string UndefinedType::Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+std::string UndefinedType::Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   return "Undefined";
 }
 
@@ -391,7 +391,7 @@ PreciseReferenceType::PreciseReferenceType(mirror::Class* klass, const std::stri
   DCHECK(klass->IsInstantiable());
 }
 
-std::string UnresolvedMergedType::Dump() {
+std::string UnresolvedMergedType::Dump() const {
   std::stringstream result;
   std::set<uint16_t> types = GetMergedTypes();
   result << "UnresolvedMergedReferences(";
@@ -405,20 +405,20 @@ std::string UnresolvedMergedType::Dump() {
   return result.str();
 }
 
-std::string UnresolvedSuperClass::Dump() {
+std::string UnresolvedSuperClass::Dump() const {
   std::stringstream result;
   uint16_t super_type_id = GetUnresolvedSuperClassChildId();
   result << "UnresolvedSuperClass(" << reg_type_cache_->GetFromId(super_type_id).Dump() << ")";
   return result.str();
 }
 
-std::string UnresolvedReferenceType::Dump() {
+std::string UnresolvedReferenceType::Dump() const {
   std::stringstream result;
   result << "Unresolved Reference" << ": " << PrettyDescriptor(GetDescriptor().c_str());
   return result.str();
 }
 
-std::string UnresolvedUninitializedRefType::Dump() {
+std::string UnresolvedUninitializedRefType::Dump() const {
   std::stringstream result;
   result << "Unresolved And Uninitialized Reference" << ": "
       << PrettyDescriptor(GetDescriptor().c_str())
@@ -426,40 +426,40 @@ std::string UnresolvedUninitializedRefType::Dump() {
   return result.str();
 }
 
-std::string UnresolvedUninitializedThisRefType::Dump() {
+std::string UnresolvedUninitializedThisRefType::Dump() const {
   std::stringstream result;
   result << "Unresolved And Uninitialized This Reference"
       << PrettyDescriptor(GetDescriptor().c_str());
   return result.str();
 }
 
-std::string ReferenceType::Dump() {
+std::string ReferenceType::Dump() const {
   std::stringstream result;
   result << "Reference" << ": " << PrettyDescriptor(GetClass());
   return result.str();
 }
 
-std::string PreciseReferenceType::Dump() {
+std::string PreciseReferenceType::Dump() const {
   std::stringstream result;
   result << "Precise Reference" << ": "<< PrettyDescriptor(GetClass());
   return result.str();
 }
 
-std::string UninitializedReferenceType::Dump() {
+std::string UninitializedReferenceType::Dump() const {
   std::stringstream result;
   result << "Uninitialized Reference" << ": " << PrettyDescriptor(GetClass());
   result << " Allocation PC: " << GetAllocationPc();
   return result.str();
 }
 
-std::string UninitializedThisReferenceType::Dump() {
+std::string UninitializedThisReferenceType::Dump() const {
   std::stringstream result;
   result << "Uninitialized This Reference" << ": " << PrettyDescriptor(GetClass());
   result << "Allocation PC: " << GetAllocationPc();
   return result.str();
 }
 
-std::string ImpreciseConstType::Dump() {
+std::string ImpreciseConstType::Dump() const {
   std::stringstream result;
   uint32_t val = ConstantValue();
   if (val == 0) {
@@ -474,7 +474,7 @@ std::string ImpreciseConstType::Dump() {
   }
   return result.str();
 }
-std::string PreciseConstLoType::Dump() {
+std::string PreciseConstLoType::Dump() const {
   std::stringstream result;
 
   int32_t val = ConstantValueLo();
@@ -488,7 +488,7 @@ std::string PreciseConstLoType::Dump() {
   return result.str();
 }
 
-std::string ImpreciseConstLoType::Dump() {
+std::string ImpreciseConstLoType::Dump() const {
   std::stringstream result;
 
   int32_t val = ConstantValueLo();
@@ -502,7 +502,7 @@ std::string ImpreciseConstLoType::Dump() {
   return result.str();
 }
 
-std::string PreciseConstHiType::Dump() {
+std::string PreciseConstHiType::Dump() const {
   std::stringstream result;
   int32_t val = ConstantValueHi();
   result << "Precise ";
@@ -515,7 +515,7 @@ std::string PreciseConstHiType::Dump() {
   return result.str();
 }
 
-std::string ImpreciseConstHiType::Dump() {
+std::string ImpreciseConstHiType::Dump() const {
   std::stringstream result;
   int32_t val = ConstantValueHi();
   result << "Imprecise ";
@@ -532,7 +532,7 @@ ConstantType::ConstantType(uint32_t constant, uint16_t cache_id)
     : RegType(NULL, "", cache_id), constant_(constant) {
 }
 
-RegType& UndefinedType::Merge(RegType& incoming_type, RegTypeCache* reg_types)
+const RegType& UndefinedType::Merge(const RegType& incoming_type, RegTypeCache* reg_types) const
     SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   if (incoming_type.IsUndefined()) {
     return *this;  // Undefined MERGE Undefined => Undefined
@@ -540,7 +540,7 @@ RegType& UndefinedType::Merge(RegType& incoming_type, RegTypeCache* reg_types)
   return reg_types->Conflict();
 }
 
-RegType& RegType::HighHalf(RegTypeCache* cache) const {
+const RegType& RegType::HighHalf(RegTypeCache* cache) const {
   DCHECK(IsLowHalf());
   if (IsLongLo()) {
     return cache->LongHi();
@@ -588,10 +588,12 @@ bool UnresolvedType::IsNonZeroReferenceTypes() const {
 }
 std::set<uint16_t> UnresolvedMergedType::GetMergedTypes() const {
   std::pair<uint16_t, uint16_t> refs = GetTopMergedTypes();
-  RegType& _left(reg_type_cache_->GetFromId(refs.first));
-  UnresolvedMergedType* left = down_cast<UnresolvedMergedType*>(&_left);
+  const RegType& _left(reg_type_cache_->GetFromId(refs.first));
+  RegType& __left(const_cast<RegType&>(_left));
+  UnresolvedMergedType* left = down_cast<UnresolvedMergedType*>(&__left);
 
-  RegType& _right(reg_type_cache_->GetFromId(refs.second));
+  RegType& _right(
+      const_cast<RegType&>(reg_type_cache_->GetFromId(refs.second)));
   UnresolvedMergedType* right = down_cast<UnresolvedMergedType*>(&_right);
 
   std::set<uint16_t> types;
@@ -614,7 +616,7 @@ std::set<uint16_t> UnresolvedMergedType::GetMergedTypes() const {
   return types;
 }
 
-RegType& RegType::GetSuperClass(RegTypeCache* cache) {
+const RegType& RegType::GetSuperClass(RegTypeCache* cache) const {
   if (!IsUnresolvedTypes()) {
     mirror::Class* super_klass = GetClass()->GetSuperClass();
     if (super_klass != NULL) {
@@ -636,7 +638,7 @@ RegType& RegType::GetSuperClass(RegTypeCache* cache) {
   }
 }
 
-bool RegType::CanAccess(RegType& other) {
+bool RegType::CanAccess(const RegType& other) const {
   if (Equals(other)) {
     return true;  // Trivial accessibility.
   } else {
@@ -652,7 +654,7 @@ bool RegType::CanAccess(RegType& other) {
   }
 }
 
-bool RegType::CanAccessMember(mirror::Class* klass, uint32_t access_flags) {
+bool RegType::CanAccessMember(mirror::Class* klass, uint32_t access_flags) const {
   if ((access_flags & kAccPublic) != 0) {
     return true;
   }
@@ -663,7 +665,7 @@ bool RegType::CanAccessMember(mirror::Class* klass, uint32_t access_flags) {
   }
 }
 
-bool RegType::IsObjectArrayTypes() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+bool RegType::IsObjectArrayTypes() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   if (IsUnresolvedTypes() && !IsUnresolvedMergedReference() && !IsUnresolvedSuperClass()) {
     // Primitive arrays will always resolve
     DCHECK(descriptor_[1] == 'L' || descriptor_[1] == '[');
@@ -676,11 +678,11 @@ bool RegType::IsObjectArrayTypes() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   }
 }
 
-bool RegType::IsJavaLangObject() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+bool RegType::IsJavaLangObject() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   return IsReference() && GetClass()->IsObjectClass();
 }
 
-bool RegType::IsArrayTypes() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+bool RegType::IsArrayTypes() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   if (IsUnresolvedTypes() && !IsUnresolvedMergedReference() && !IsUnresolvedSuperClass()) {
     return descriptor_[0] == '[';
   } else if (HasClass()) {
@@ -690,7 +692,7 @@ bool RegType::IsArrayTypes() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   }
 }
 
-bool RegType::IsJavaLangObjectArray() {
+bool RegType::IsJavaLangObjectArray() const {
   if (HasClass()) {
     mirror::Class* type = GetClass();
     return type->IsArrayClass() && type->GetComponentType()->IsObjectClass();
@@ -698,7 +700,7 @@ bool RegType::IsJavaLangObjectArray() {
   return false;
 }
 
-bool RegType::IsInstantiableTypes() {
+bool RegType::IsInstantiableTypes() const {
   return IsUnresolvedTypes() || (IsNonZeroReferenceTypes() && GetClass()->IsInstantiable());
 }
 
@@ -706,7 +708,7 @@ ImpreciseConstType::ImpreciseConstType(uint32_t constat, uint16_t cache_id)
   : ConstantType(constat, cache_id) {
 }
 
-static bool AssignableFrom(RegType& lhs, RegType& rhs, bool strict)
+static bool AssignableFrom(const RegType& lhs, const RegType& rhs, bool strict)
     SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
   if (lhs.Equals(rhs)) {
     return true;
@@ -754,11 +756,11 @@ static bool AssignableFrom(RegType& lhs, RegType& rhs, bool strict)
   }
 }
 
-bool RegType::IsAssignableFrom(RegType& src) {
+bool RegType::IsAssignableFrom(const RegType& src) const {
   return AssignableFrom(*this, src, false);
 }
 
-bool RegType::IsStrictlyAssignableFrom(RegType& src) {
+bool RegType::IsStrictlyAssignableFrom(const RegType& src) const {
   return AssignableFrom(*this, src, true);
 }
 
@@ -776,11 +778,11 @@ int32_t ConstantType::ConstantValueHi() const {
   }
 }
 
-static RegType& SelectNonConstant(RegType& a, RegType& b) {
+static const RegType& SelectNonConstant(const RegType& a, const RegType& b) {
   return a.IsConstantTypes() ? b : a;
 }
 
-RegType& RegType::Merge(RegType& incoming_type, RegTypeCache* reg_types) {
+const RegType& RegType::Merge(const RegType& incoming_type, RegTypeCache* reg_types) const {
   DCHECK(!Equals(incoming_type));  // Trivial equality handled by caller
   if (IsConflict()) {
     return *this;  // Conflict MERGE * => Conflict
@@ -960,16 +962,16 @@ mirror::Class* RegType::ClassJoin(mirror::Class* s, mirror::Class* t) {
 void RegType::CheckInvariants() const {
   if (IsConstant() || IsConstantLo() || IsConstantHi()) {
     CHECK(descriptor_.empty()) << *this;
-    CHECK(klass_.IsNull()) << *this;
+    CHECK(klass_ == NULL) << *this;
   }
-  if (!klass_.IsNull()) {
+  if (klass_ != NULL) {
     CHECK(!descriptor_.empty()) << *this;
   }
 }
 
 void RegType::VisitRoots(RootCallback* callback, void* arg) {
-  if (!klass_.IsNull()) {
-    klass_.VisitRoot(callback, arg, 0, kRootUnknown);
+  if (klass_ != nullptr) {
+    callback(reinterpret_cast<mirror::Object**>(&klass_), arg, 0, kRootUnknown);
   }
 }
 
@@ -980,37 +982,36 @@ void UninitializedThisReferenceType::CheckInvariants() const {
 void UnresolvedUninitializedThisRefType::CheckInvariants() const {
   CHECK_EQ(GetAllocationPc(), 0U) << *this;
   CHECK(!descriptor_.empty()) << *this;
-  CHECK(klass_.IsNull()) << *this;
+  CHECK(klass_ == NULL) << *this;
 }
 
 void UnresolvedUninitializedRefType::CheckInvariants() const {
   CHECK(!descriptor_.empty()) << *this;
-  CHECK(klass_.IsNull()) << *this;
+  CHECK(klass_ == NULL) << *this;
 }
 
 void UnresolvedMergedType::CheckInvariants() const {
   // Unresolved merged types: merged types should be defined.
   CHECK(descriptor_.empty()) << *this;
-  CHECK(klass_.IsNull()) << *this;
+  CHECK(klass_ == NULL) << *this;
   CHECK_NE(merged_types_.first, 0U) << *this;
   CHECK_NE(merged_types_.second, 0U) << *this;
 }
 
 void UnresolvedReferenceType::CheckInvariants() const {
   CHECK(!descriptor_.empty()) << *this;
-  CHECK(klass_.IsNull()) << *this;
+  CHECK(klass_ == NULL) << *this;
 }
 
 void UnresolvedSuperClass::CheckInvariants() const {
   // Unresolved merged types: merged types should be defined.
   CHECK(descriptor_.empty()) << *this;
-  CHECK(klass_.IsNull()) << *this;
+  CHECK(klass_ == NULL) << *this;
   CHECK_NE(unresolved_child_id_, 0U) << *this;
 }
 
 std::ostream& operator<<(std::ostream& os, const RegType& rhs) {
-  RegType& rhs_non_const = const_cast<RegType&>(rhs);
-  os << rhs_non_const.Dump();
+  os << rhs.Dump();
   return os;
 }
 
diff --git a/runtime/verifier/reg_type.h b/runtime/verifier/reg_type.h
index 1682d4e..f211f8a 100644
--- a/runtime/verifier/reg_type.h
+++ b/runtime/verifier/reg_type.h
@@ -26,7 +26,6 @@
 
 #include "base/macros.h"
 #include "base/mutex.h"
-#include "gc_root.h"
 #include "globals.h"
 #include "object_callbacks.h"
 #include "primitive.h"
@@ -109,7 +108,7 @@ class RegType {
     return IsLowHalf();
   }
   // Check this is the low half, and that type_h is its matching high-half.
-  inline bool CheckWidePair(RegType& type_h) const {
+  inline bool CheckWidePair(const RegType& type_h) const {
     if (IsLowHalf()) {
       return ((IsPreciseConstantLo() && type_h.IsPreciseConstantHi()) ||
               (IsPreciseConstantLo() && type_h.IsImpreciseConstantHi()) ||
@@ -121,7 +120,7 @@ class RegType {
     return false;
   }
   // The high half that corresponds to this low half
-  RegType& HighHalf(RegTypeCache* cache) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  const RegType& HighHalf(RegTypeCache* cache) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   bool IsConstantBoolean() const {
     return IsConstant() && (ConstantValue() >= 0) && (ConstantValue() <= 1);
@@ -200,54 +199,55 @@ class RegType {
   virtual bool HasClass() const {
     return false;
   }
-  bool IsJavaLangObject() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  bool IsArrayTypes() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  bool IsObjectArrayTypes() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  bool IsJavaLangObject() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  bool IsArrayTypes() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  bool IsObjectArrayTypes() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   Primitive::Type GetPrimitiveType() const;
-  bool IsJavaLangObjectArray() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  bool IsInstantiableTypes() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  bool IsJavaLangObjectArray() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  bool IsInstantiableTypes() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   const std::string& GetDescriptor() const {
     DCHECK(HasClass() || (IsUnresolvedTypes() && !IsUnresolvedMergedReference() &&
                           !IsUnresolvedSuperClass()));
     return descriptor_;
   }
-  mirror::Class* GetClass() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+  mirror::Class* GetClass() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     DCHECK(!IsUnresolvedReference());
-    DCHECK(!klass_.IsNull()) << Dump();
+    DCHECK(klass_ != NULL) << Dump();
     DCHECK(HasClass());
-    return klass_.Read();
+    return klass_;
   }
   uint16_t GetId() const {
     return cache_id_;
   }
-  RegType& GetSuperClass(RegTypeCache* cache)
+  const RegType& GetSuperClass(RegTypeCache* cache) const
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  virtual std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) = 0;
+  virtual std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) = 0;
 
   // Can this type access other?
-  bool CanAccess(RegType& other) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  bool CanAccess(const RegType& other) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Can this type access a member with the given properties?
-  bool CanAccessMember(mirror::Class* klass, uint32_t access_flags)
+  bool CanAccessMember(mirror::Class* klass, uint32_t access_flags) const
     SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Can this type be assigned by src?
   // Note: Object and interface types may always be assigned to one another, see comment on
   // ClassJoin.
-  bool IsAssignableFrom(RegType& src) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  bool IsAssignableFrom(const RegType& src) const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Can this type be assigned by src? Variant of IsAssignableFrom that doesn't allow assignment to
   // an interface from an Object.
-  bool IsStrictlyAssignableFrom(RegType& src) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  bool IsStrictlyAssignableFrom(const RegType& src) const
+      SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Are these RegTypes the same?
-  bool Equals(RegType& other) const {
+  bool Equals(const RegType& other) const {
     return GetId() == other.GetId();
   }
 
   // Compute the merge of this register from one edge (path) with incoming_type from another.
-  virtual RegType& Merge(RegType& incoming_type, RegTypeCache* reg_types)
+  virtual const RegType& Merge(const RegType& incoming_type, RegTypeCache* reg_types) const
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   /*
@@ -276,7 +276,7 @@ class RegType {
  protected:
   RegType(mirror::Class* klass, const std::string& descriptor, uint16_t cache_id)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_)
-      : descriptor_(descriptor), klass_(GcRoot<mirror::Class>(klass)), cache_id_(cache_id) {
+      : descriptor_(descriptor), klass_(klass), cache_id_(cache_id) {
     if (kIsDebugBuild) {
       CheckInvariants();
     }
@@ -286,7 +286,7 @@ class RegType {
 
 
   const std::string descriptor_;
-  GcRoot<mirror::Class> klass_;
+  mirror::Class* klass_;  // Non-const only due to moving classes.
   const uint16_t cache_id_;
 
   friend class RegTypeCache;
@@ -302,7 +302,7 @@ class ConflictType : public RegType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Get the singleton Conflict instance.
   static ConflictType* GetInstance();
@@ -332,7 +332,7 @@ class UndefinedType : public RegType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Get the singleton Undefined instance.
   static UndefinedType* GetInstance();
@@ -351,7 +351,7 @@ class UndefinedType : public RegType {
       : RegType(klass, descriptor, cache_id) {
   }
 
-  virtual RegType& Merge(RegType& incoming_type, RegTypeCache* reg_types)
+  virtual const RegType& Merge(const RegType& incoming_type, RegTypeCache* reg_types) const
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   static UndefinedType* instance_;
@@ -374,7 +374,7 @@ class IntegerType : public Cat1Type {
   bool IsInteger() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   static IntegerType* CreateInstance(mirror::Class* klass, const std::string& descriptor,
                                      uint16_t cache_id)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -393,7 +393,7 @@ class BooleanType : public Cat1Type {
   bool IsBoolean() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   static BooleanType* CreateInstance(mirror::Class* klass, const std::string& descriptor,
                                      uint16_t cache_id)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -413,7 +413,7 @@ class ByteType : public Cat1Type {
   bool IsByte() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   static ByteType* CreateInstance(mirror::Class* klass, const std::string& descriptor,
                                   uint16_t cache_id)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -432,7 +432,7 @@ class ShortType : public Cat1Type {
   bool IsShort() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   static ShortType* CreateInstance(mirror::Class* klass, const std::string& descriptor,
                                    uint16_t cache_id)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -451,7 +451,7 @@ class CharType : public Cat1Type {
   bool IsChar() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   static CharType* CreateInstance(mirror::Class* klass, const std::string& descriptor,
                                   uint16_t cache_id)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -470,7 +470,7 @@ class FloatType : public Cat1Type {
   bool IsFloat() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   static FloatType* CreateInstance(mirror::Class* klass, const std::string& descriptor,
                                    uint16_t cache_id)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -492,7 +492,7 @@ class Cat2Type : public PrimitiveType {
 
 class LongLoType : public Cat2Type {
  public:
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   bool IsLongLo() const {
     return true;
   }
@@ -514,7 +514,7 @@ class LongLoType : public Cat2Type {
 
 class LongHiType : public Cat2Type {
  public:
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   bool IsLongHi() const {
     return true;
   }
@@ -533,7 +533,7 @@ class LongHiType : public Cat2Type {
 
 class DoubleLoType : public Cat2Type {
  public:
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   bool IsDoubleLo() const {
     return true;
   }
@@ -555,7 +555,7 @@ class DoubleLoType : public Cat2Type {
 
 class DoubleHiType : public Cat2Type {
  public:
-  std::string Dump();
+  std::string Dump() const;
   virtual bool IsDoubleHi() const {
     return true;
   }
@@ -622,7 +622,7 @@ class PreciseConstType : public ConstantType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
 
 class PreciseConstLoType : public ConstantType {
@@ -634,7 +634,7 @@ class PreciseConstLoType : public ConstantType {
   bool IsPreciseConstantLo() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
 
 class PreciseConstHiType : public ConstantType {
@@ -646,7 +646,7 @@ class PreciseConstHiType : public ConstantType {
   bool IsPreciseConstantHi() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
 
 class ImpreciseConstType : public ConstantType {
@@ -656,7 +656,7 @@ class ImpreciseConstType : public ConstantType {
   bool IsImpreciseConstant() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
 
 class ImpreciseConstLoType : public ConstantType {
@@ -667,7 +667,7 @@ class ImpreciseConstLoType : public ConstantType {
   bool IsImpreciseConstantLo() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
 
 class ImpreciseConstHiType : public ConstantType {
@@ -678,7 +678,7 @@ class ImpreciseConstHiType : public ConstantType {
   bool IsImpreciseConstantHi() const {
     return true;
   }
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
 
 // Common parent of all uninitialized types. Uninitialized types are created by "new" dex
@@ -719,7 +719,7 @@ class UninitializedReferenceType : public UninitializedType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
 
 // Similar to UnresolvedReferenceType but not yet having been passed to a constructor.
@@ -738,7 +738,7 @@ class UnresolvedUninitializedRefType : public UninitializedType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
  private:
   void CheckInvariants() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
@@ -763,7 +763,7 @@ class UninitializedThisReferenceType : public UninitializedType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
  private:
   void CheckInvariants() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -783,7 +783,7 @@ class UnresolvedUninitializedThisRefType : public UninitializedType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
  private:
   void CheckInvariants() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
@@ -808,7 +808,7 @@ class ReferenceType : public RegType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
 
 // A type of register holding a reference to an Object of type GetClass and only an object of that
@@ -830,7 +830,7 @@ class PreciseReferenceType : public RegType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
 
 // Common parent of unresolved types.
@@ -858,7 +858,7 @@ class UnresolvedReferenceType : public UnresolvedType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
  private:
   void CheckInvariants() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 };
@@ -884,7 +884,7 @@ class UnresolvedSuperClass : public UnresolvedType {
     return static_cast<uint16_t>(unresolved_child_id_ & 0xFFFF);
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
  private:
   void CheckInvariants() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
@@ -919,7 +919,7 @@ class UnresolvedMergedType : public UnresolvedType {
     return true;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
  private:
   void CheckInvariants() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
diff --git a/runtime/verifier/reg_type_cache-inl.h b/runtime/verifier/reg_type_cache-inl.h
index fdf96a8..fc9e5c9 100644
--- a/runtime/verifier/reg_type_cache-inl.h
+++ b/runtime/verifier/reg_type_cache-inl.h
@@ -24,14 +24,14 @@
 namespace art {
 namespace verifier {
 
-inline RegType& RegTypeCache::GetFromId(uint16_t id) const {
+inline const art::verifier::RegType& RegTypeCache::GetFromId(uint16_t id) const {
   DCHECK_LT(id, entries_.size());
   RegType* result = entries_[id];
   DCHECK(result != NULL);
   return *result;
 }
 
-inline ConstantType& RegTypeCache::FromCat1Const(int32_t value, bool precise) {
+inline const ConstantType& RegTypeCache::FromCat1Const(int32_t value, bool precise) {
   // We only expect 0 to be a precise constant.
   DCHECK(value != 0 || precise);
   if (precise && (value >= kMinSmallConstant) && (value <= kMaxSmallConstant)) {
diff --git a/runtime/verifier/reg_type_cache.cc b/runtime/verifier/reg_type_cache.cc
index 482bb4d..641f327 100644
--- a/runtime/verifier/reg_type_cache.cc
+++ b/runtime/verifier/reg_type_cache.cc
@@ -65,8 +65,8 @@ void RegTypeCache::FillPrimitiveAndSmallConstantTypes() {
   DCHECK_EQ(entries_.size(), primitive_count_);
 }
 
-RegType& RegTypeCache::FromDescriptor(mirror::ClassLoader* loader, const char* descriptor,
-                                      bool precise) {
+const RegType& RegTypeCache::FromDescriptor(mirror::ClassLoader* loader, const char* descriptor,
+                                            bool precise) {
   DCHECK(RegTypeCache::primitive_initialized_);
   if (descriptor[1] == '\0') {
     switch (descriptor[0]) {
@@ -97,7 +97,7 @@ RegType& RegTypeCache::FromDescriptor(mirror::ClassLoader* loader, const char* d
   }
 };
 
-RegType& RegTypeCache::RegTypeFromPrimitiveType(Primitive::Type prim_type) const {
+const RegType& RegTypeCache::RegTypeFromPrimitiveType(Primitive::Type prim_type) const {
   CHECK(RegTypeCache::primitive_initialized_);
   switch (prim_type) {
     case Primitive::kPrimBoolean:
@@ -156,8 +156,8 @@ mirror::Class* RegTypeCache::ResolveClass(const char* descriptor, mirror::ClassL
   return klass;
 }
 
-RegType& RegTypeCache::From(mirror::ClassLoader* loader, const char* descriptor,
-                            bool precise) {
+const RegType& RegTypeCache::From(mirror::ClassLoader* loader, const char* descriptor,
+                                  bool precise) {
   // Try looking up the class in the cache first. We use a StringPiece to avoid continual strlen
   // operations on the descriptor.
   StringPiece descriptor_sp(descriptor);
@@ -210,7 +210,7 @@ RegType& RegTypeCache::From(mirror::ClassLoader* loader, const char* descriptor,
   }
 }
 
-RegType& RegTypeCache::FromClass(const char* descriptor, mirror::Class* klass, bool precise) {
+const RegType& RegTypeCache::FromClass(const char* descriptor, mirror::Class* klass, bool precise) {
   DCHECK(klass != nullptr);
   if (klass->IsPrimitive()) {
     // Note: precise isn't used for primitive classes. A char is assignable to an int. All
@@ -220,7 +220,7 @@ RegType& RegTypeCache::FromClass(const char* descriptor, mirror::Class* klass, b
     // Look for the reference in the list of entries to have.
     for (size_t i = primitive_count_; i < entries_.size(); i++) {
       RegType* cur_entry = entries_[i];
-      if (cur_entry->klass_.Read() == klass && MatchingPrecisionForClass(cur_entry, precise)) {
+      if (cur_entry->klass_ == klass && MatchingPrecisionForClass(cur_entry, precise)) {
         return *cur_entry;
       }
     }
@@ -313,15 +313,17 @@ void RegTypeCache::CreatePrimitiveAndSmallConstantTypes() {
   }
 }
 
-RegType& RegTypeCache::FromUnresolvedMerge(RegType& left, RegType& right) {
+const RegType& RegTypeCache::FromUnresolvedMerge(const RegType& left, const RegType& right) {
   std::set<uint16_t> types;
   if (left.IsUnresolvedMergedReference()) {
-    types = (down_cast<UnresolvedMergedType*>(&left))->GetMergedTypes();
+    RegType& non_const(const_cast<RegType&>(left));
+    types = (down_cast<UnresolvedMergedType*>(&non_const))->GetMergedTypes();
   } else {
     types.insert(left.GetId());
   }
   if (right.IsUnresolvedMergedReference()) {
-    std::set<uint16_t> right_types = (down_cast<UnresolvedMergedType*>(&right))->GetMergedTypes();
+    RegType& non_const(const_cast<RegType&>(right));
+    std::set<uint16_t> right_types = (down_cast<UnresolvedMergedType*>(&non_const))->GetMergedTypes();
     types.insert(right_types.begin(), right_types.end());
   } else {
     types.insert(right.GetId());
@@ -348,7 +350,7 @@ RegType& RegTypeCache::FromUnresolvedMerge(RegType& left, RegType& right) {
   return *entry;
 }
 
-RegType& RegTypeCache::FromUnresolvedSuperClass(RegType& child) {
+const RegType& RegTypeCache::FromUnresolvedSuperClass(const RegType& child) {
   // Check if entry already exists.
   for (size_t i = primitive_count_; i < entries_.size(); i++) {
     RegType* cur_entry = entries_[i];
@@ -367,7 +369,7 @@ RegType& RegTypeCache::FromUnresolvedSuperClass(RegType& child) {
   return *entry;
 }
 
-UninitializedType& RegTypeCache::Uninitialized(RegType& type, uint32_t allocation_pc) {
+const UninitializedType& RegTypeCache::Uninitialized(const RegType& type, uint32_t allocation_pc) {
   UninitializedType* entry = NULL;
   const std::string& descriptor(type.GetDescriptor());
   if (type.IsUnresolvedTypes()) {
@@ -397,7 +399,7 @@ UninitializedType& RegTypeCache::Uninitialized(RegType& type, uint32_t allocatio
   return *entry;
 }
 
-RegType& RegTypeCache::FromUninitialized(RegType& uninit_type) {
+const RegType& RegTypeCache::FromUninitialized(const RegType& uninit_type) {
   RegType* entry;
 
   if (uninit_type.IsUnresolvedTypes()) {
@@ -439,44 +441,44 @@ RegType& RegTypeCache::FromUninitialized(RegType& uninit_type) {
   return *entry;
 }
 
-ImpreciseConstType& RegTypeCache::ByteConstant() {
-  ConstantType& result = FromCat1Const(std::numeric_limits<jbyte>::min(), false);
+const ImpreciseConstType& RegTypeCache::ByteConstant() {
+  const ConstantType& result = FromCat1Const(std::numeric_limits<jbyte>::min(), false);
   DCHECK(result.IsImpreciseConstant());
-  return *down_cast<ImpreciseConstType*>(&result);
+  return *down_cast<const ImpreciseConstType*>(&result);
 }
 
-ImpreciseConstType& RegTypeCache::CharConstant() {
+const ImpreciseConstType& RegTypeCache::CharConstant() {
   int32_t jchar_max = static_cast<int32_t>(std::numeric_limits<jchar>::max());
-  ConstantType& result =  FromCat1Const(jchar_max, false);
+  const ConstantType& result =  FromCat1Const(jchar_max, false);
   DCHECK(result.IsImpreciseConstant());
-  return *down_cast<ImpreciseConstType*>(&result);
+  return *down_cast<const ImpreciseConstType*>(&result);
 }
 
-ImpreciseConstType& RegTypeCache::ShortConstant() {
-  ConstantType& result =  FromCat1Const(std::numeric_limits<jshort>::min(), false);
+const ImpreciseConstType& RegTypeCache::ShortConstant() {
+  const ConstantType& result =  FromCat1Const(std::numeric_limits<jshort>::min(), false);
   DCHECK(result.IsImpreciseConstant());
-  return *down_cast<ImpreciseConstType*>(&result);
+  return *down_cast<const ImpreciseConstType*>(&result);
 }
 
-ImpreciseConstType& RegTypeCache::IntConstant() {
-  ConstantType& result = FromCat1Const(std::numeric_limits<jint>::max(), false);
+const ImpreciseConstType& RegTypeCache::IntConstant() {
+  const ConstantType& result = FromCat1Const(std::numeric_limits<jint>::max(), false);
   DCHECK(result.IsImpreciseConstant());
-  return *down_cast<ImpreciseConstType*>(&result);
+  return *down_cast<const ImpreciseConstType*>(&result);
 }
 
-ImpreciseConstType& RegTypeCache::PosByteConstant() {
-  ConstantType& result = FromCat1Const(std::numeric_limits<jbyte>::max(), false);
+const ImpreciseConstType& RegTypeCache::PosByteConstant() {
+  const ConstantType& result = FromCat1Const(std::numeric_limits<jbyte>::max(), false);
   DCHECK(result.IsImpreciseConstant());
-  return *down_cast<ImpreciseConstType*>(&result);
+  return *down_cast<const ImpreciseConstType*>(&result);
 }
 
-ImpreciseConstType& RegTypeCache::PosShortConstant() {
-  ConstantType& result =  FromCat1Const(std::numeric_limits<jshort>::max(), false);
+const ImpreciseConstType& RegTypeCache::PosShortConstant() {
+  const ConstantType& result =  FromCat1Const(std::numeric_limits<jshort>::max(), false);
   DCHECK(result.IsImpreciseConstant());
-  return *down_cast<ImpreciseConstType*>(&result);
+  return *down_cast<const ImpreciseConstType*>(&result);
 }
 
-UninitializedType& RegTypeCache::UninitializedThisArgument(RegType& type) {
+const UninitializedType& RegTypeCache::UninitializedThisArgument(const RegType& type) {
   UninitializedType* entry;
   const std::string& descriptor(type.GetDescriptor());
   if (type.IsUnresolvedTypes()) {
@@ -502,10 +504,10 @@ UninitializedType& RegTypeCache::UninitializedThisArgument(RegType& type) {
   return *entry;
 }
 
-ConstantType& RegTypeCache::FromCat1NonSmallConstant(int32_t value, bool precise) {
+const ConstantType& RegTypeCache::FromCat1NonSmallConstant(int32_t value, bool precise) {
   for (size_t i = primitive_count_; i < entries_.size(); i++) {
     RegType* cur_entry = entries_[i];
-    if (cur_entry->klass_.IsNull() && cur_entry->IsConstant() &&
+    if (cur_entry->klass_ == NULL && cur_entry->IsConstant() &&
         cur_entry->IsPreciseConstant() == precise &&
         (down_cast<ConstantType*>(cur_entry))->ConstantValue() == value) {
       return *down_cast<ConstantType*>(cur_entry);
@@ -521,7 +523,7 @@ ConstantType& RegTypeCache::FromCat1NonSmallConstant(int32_t value, bool precise
   return *entry;
 }
 
-ConstantType& RegTypeCache::FromCat2ConstLo(int32_t value, bool precise) {
+const ConstantType& RegTypeCache::FromCat2ConstLo(int32_t value, bool precise) {
   for (size_t i = primitive_count_; i < entries_.size(); i++) {
     RegType* cur_entry = entries_[i];
     if (cur_entry->IsConstantLo() && (cur_entry->IsPrecise() == precise) &&
@@ -539,7 +541,7 @@ ConstantType& RegTypeCache::FromCat2ConstLo(int32_t value, bool precise) {
   return *entry;
 }
 
-ConstantType& RegTypeCache::FromCat2ConstHi(int32_t value, bool precise) {
+const ConstantType& RegTypeCache::FromCat2ConstHi(int32_t value, bool precise) {
   for (size_t i = primitive_count_; i < entries_.size(); i++) {
     RegType* cur_entry = entries_[i];
     if (cur_entry->IsConstantHi() && (cur_entry->IsPrecise() == precise) &&
@@ -557,7 +559,7 @@ ConstantType& RegTypeCache::FromCat2ConstHi(int32_t value, bool precise) {
   return *entry;
 }
 
-RegType& RegTypeCache::GetComponentType(RegType& array, mirror::ClassLoader* loader) {
+const RegType& RegTypeCache::GetComponentType(const RegType& array, mirror::ClassLoader* loader) {
   if (!array.IsArrayTypes()) {
     return Conflict();
   } else if (array.IsUnresolvedTypes()) {
diff --git a/runtime/verifier/reg_type_cache.h b/runtime/verifier/reg_type_cache.h
index c0427eb..8baf3ff 100644
--- a/runtime/verifier/reg_type_cache.h
+++ b/runtime/verifier/reg_type_cache.h
@@ -51,99 +51,99 @@ class RegTypeCache {
     }
   }
   static void ShutDown();
-  RegType& GetFromId(uint16_t id) const;
-  RegType& From(mirror::ClassLoader* loader, const char* descriptor, bool precise)
+  const art::verifier::RegType& GetFromId(uint16_t id) const;
+  const RegType& From(mirror::ClassLoader* loader, const char* descriptor, bool precise)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  RegType& FromClass(const char* descriptor, mirror::Class* klass, bool precise)
+  const RegType& FromClass(const char* descriptor, mirror::Class* klass, bool precise)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  ConstantType& FromCat1Const(int32_t value, bool precise)
+  const ConstantType& FromCat1Const(int32_t value, bool precise)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  ConstantType& FromCat2ConstLo(int32_t value, bool precise)
+  const ConstantType& FromCat2ConstLo(int32_t value, bool precise)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  ConstantType& FromCat2ConstHi(int32_t value, bool precise)
+  const ConstantType& FromCat2ConstHi(int32_t value, bool precise)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  RegType& FromDescriptor(mirror::ClassLoader* loader, const char* descriptor, bool precise)
+  const RegType& FromDescriptor(mirror::ClassLoader* loader, const char* descriptor, bool precise)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  RegType& FromUnresolvedMerge(RegType& left, RegType& right)
+  const RegType& FromUnresolvedMerge(const RegType& left, const RegType& right)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  RegType& FromUnresolvedSuperClass(RegType& child)
+  const RegType& FromUnresolvedSuperClass(const RegType& child)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  RegType& JavaLangString() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+  const RegType& JavaLangString() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     // String is final and therefore always precise.
     return From(NULL, "Ljava/lang/String;", true);
   }
-  RegType& JavaLangThrowable(bool precise)
+  const RegType& JavaLangThrowable(bool precise)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     return From(NULL, "Ljava/lang/Throwable;", precise);
   }
-  ConstantType& Zero() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+  const ConstantType& Zero() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     return FromCat1Const(0, true);
   }
-  ConstantType& One() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+  const ConstantType& One() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     return FromCat1Const(1, true);
   }
   size_t GetCacheSize() {
     return entries_.size();
   }
-  RegType& Boolean() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+  const RegType& Boolean() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     return *BooleanType::GetInstance();
   }
-  RegType& Byte() {
+  const RegType& Byte() {
     return *ByteType::GetInstance();
   }
-  RegType& Char()  {
+  const RegType& Char()  {
     return *CharType::GetInstance();
   }
-  RegType& Short()  {
+  const RegType& Short()  {
     return *ShortType::GetInstance();
   }
-  RegType& Integer() {
+  const RegType& Integer() {
     return *IntegerType::GetInstance();
   }
-  RegType& Float() {
+  const RegType& Float() {
     return *FloatType::GetInstance();
   }
-  RegType& LongLo() {
+  const RegType& LongLo() {
     return *LongLoType::GetInstance();
   }
-  RegType& LongHi() {
+  const RegType& LongHi() {
     return *LongHiType::GetInstance();
   }
-  RegType& DoubleLo() {
+  const RegType& DoubleLo() {
     return *DoubleLoType::GetInstance();
   }
-  RegType& DoubleHi() {
+  const RegType& DoubleHi() {
     return *DoubleHiType::GetInstance();
   }
-  RegType& Undefined() {
+  const RegType& Undefined() {
     return *UndefinedType::GetInstance();
   }
-  RegType& Conflict() {
+  const RegType& Conflict() {
     return *ConflictType::GetInstance();
   }
-  RegType& JavaLangClass(bool precise) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+  const RegType& JavaLangClass(bool precise) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     return From(NULL, "Ljava/lang/Class;", precise);
   }
-  RegType& JavaLangObject(bool precise) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
+  const RegType& JavaLangObject(bool precise) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
     return From(NULL, "Ljava/lang/Object;", precise);
   }
-  UninitializedType& Uninitialized(RegType& type, uint32_t allocation_pc)
+  const UninitializedType& Uninitialized(const RegType& type, uint32_t allocation_pc)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   // Create an uninitialized 'this' argument for the given type.
-  UninitializedType& UninitializedThisArgument(RegType& type)
+  const UninitializedType& UninitializedThisArgument(const RegType& type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  RegType& FromUninitialized(RegType& uninit_type)
+  const RegType& FromUninitialized(const RegType& uninit_type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  ImpreciseConstType& ByteConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  ImpreciseConstType& CharConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  ImpreciseConstType& ShortConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  ImpreciseConstType& IntConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  ImpreciseConstType& PosByteConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  ImpreciseConstType& PosShortConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  RegType& GetComponentType(RegType& array, mirror::ClassLoader* loader)
+  const ImpreciseConstType& ByteConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  const ImpreciseConstType& CharConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  const ImpreciseConstType& ShortConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  const ImpreciseConstType& IntConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  const ImpreciseConstType& PosByteConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  const ImpreciseConstType& PosShortConstant() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  const RegType& GetComponentType(const RegType& array, mirror::ClassLoader* loader)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   void Dump(std::ostream& os) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  RegType& RegTypeFromPrimitiveType(Primitive::Type) const;
+  const RegType& RegTypeFromPrimitiveType(Primitive::Type) const;
 
   void VisitRoots(RootCallback* callback, void* arg) SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
@@ -153,7 +153,7 @@ class RegTypeCache {
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
   bool MatchDescriptor(size_t idx, const StringPiece& descriptor, bool precise)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
-  ConstantType& FromCat1NonSmallConstant(int32_t value, bool precise)
+  const ConstantType& FromCat1NonSmallConstant(int32_t value, bool precise)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void AddEntry(RegType* new_entry);
diff --git a/runtime/verifier/reg_type_test.cc b/runtime/verifier/reg_type_test.cc
index e27558a..9dc0df1 100644
--- a/runtime/verifier/reg_type_test.cc
+++ b/runtime/verifier/reg_type_test.cc
@@ -33,21 +33,21 @@ TEST_F(RegTypeTest, ConstLoHi) {
   // Tests creating primitive types types.
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache(true);
-  RegType& ref_type_const_0 = cache.FromCat1Const(10, true);
-  RegType& ref_type_const_1 = cache.FromCat1Const(10, true);
-  RegType& ref_type_const_2 = cache.FromCat1Const(30, true);
-  RegType& ref_type_const_3 = cache.FromCat1Const(30, false);
+  const RegType& ref_type_const_0 = cache.FromCat1Const(10, true);
+  const RegType& ref_type_const_1 = cache.FromCat1Const(10, true);
+  const RegType& ref_type_const_2 = cache.FromCat1Const(30, true);
+  const RegType& ref_type_const_3 = cache.FromCat1Const(30, false);
   EXPECT_TRUE(ref_type_const_0.Equals(ref_type_const_1));
   EXPECT_FALSE(ref_type_const_0.Equals(ref_type_const_2));
   EXPECT_FALSE(ref_type_const_0.Equals(ref_type_const_3));
 
-  RegType& ref_type_const_wide_0 = cache.FromCat2ConstHi(50, true);
-  RegType& ref_type_const_wide_1 = cache.FromCat2ConstHi(50, true);
+  const RegType& ref_type_const_wide_0 = cache.FromCat2ConstHi(50, true);
+  const RegType& ref_type_const_wide_1 = cache.FromCat2ConstHi(50, true);
   EXPECT_TRUE(ref_type_const_wide_0.Equals(ref_type_const_wide_1));
 
-  RegType& ref_type_const_wide_2 = cache.FromCat2ConstLo(50, true);
-  RegType& ref_type_const_wide_3 = cache.FromCat2ConstLo(50, true);
-  RegType& ref_type_const_wide_4 = cache.FromCat2ConstLo(55, true);
+  const RegType& ref_type_const_wide_2 = cache.FromCat2ConstLo(50, true);
+  const RegType& ref_type_const_wide_3 = cache.FromCat2ConstLo(50, true);
+  const RegType& ref_type_const_wide_4 = cache.FromCat2ConstLo(55, true);
   EXPECT_TRUE(ref_type_const_wide_2.Equals(ref_type_const_wide_3));
   EXPECT_FALSE(ref_type_const_wide_2.Equals(ref_type_const_wide_4));
 }
@@ -56,11 +56,11 @@ TEST_F(RegTypeTest, Pairs) {
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache(true);
   int64_t val = static_cast<int32_t>(1234);
-  RegType& precise_lo = cache.FromCat2ConstLo(static_cast<int32_t>(val), true);
-  RegType& precise_hi = cache.FromCat2ConstHi(static_cast<int32_t>(val >> 32), true);
-  RegType& precise_const = cache.FromCat1Const(static_cast<int32_t>(val >> 32), true);
-  RegType& long_lo = cache.LongLo();
-  RegType& long_hi = cache.LongHi();
+  const RegType& precise_lo = cache.FromCat2ConstLo(static_cast<int32_t>(val), true);
+  const RegType& precise_hi = cache.FromCat2ConstHi(static_cast<int32_t>(val >> 32), true);
+  const RegType& precise_const = cache.FromCat1Const(static_cast<int32_t>(val >> 32), true);
+  const RegType& long_lo = cache.LongLo();
+  const RegType& long_hi = cache.LongHi();
   // Check sanity of types.
   EXPECT_TRUE(precise_lo.IsLowHalf());
   EXPECT_FALSE(precise_hi.IsLowHalf());
@@ -80,7 +80,7 @@ TEST_F(RegTypeTest, Primitives) {
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache(true);
 
-  RegType& bool_reg_type = cache.Boolean();
+  const RegType& bool_reg_type = cache.Boolean();
   EXPECT_FALSE(bool_reg_type.IsUndefined());
   EXPECT_FALSE(bool_reg_type.IsConflict());
   EXPECT_FALSE(bool_reg_type.IsZero());
@@ -112,7 +112,7 @@ TEST_F(RegTypeTest, Primitives) {
   EXPECT_TRUE(bool_reg_type.IsArrayIndexTypes());
   EXPECT_FALSE(bool_reg_type.IsNonZeroReferenceTypes());
 
-  RegType& byte_reg_type = cache.Byte();
+  const RegType& byte_reg_type = cache.Byte();
   EXPECT_FALSE(byte_reg_type.IsUndefined());
   EXPECT_FALSE(byte_reg_type.IsConflict());
   EXPECT_FALSE(byte_reg_type.IsZero());
@@ -144,7 +144,7 @@ TEST_F(RegTypeTest, Primitives) {
   EXPECT_TRUE(byte_reg_type.IsArrayIndexTypes());
   EXPECT_FALSE(byte_reg_type.IsNonZeroReferenceTypes());
 
-  RegType& char_reg_type = cache.Char();
+  const RegType& char_reg_type = cache.Char();
   EXPECT_FALSE(char_reg_type.IsUndefined());
   EXPECT_FALSE(char_reg_type.IsConflict());
   EXPECT_FALSE(char_reg_type.IsZero());
@@ -176,7 +176,7 @@ TEST_F(RegTypeTest, Primitives) {
   EXPECT_TRUE(char_reg_type.IsArrayIndexTypes());
   EXPECT_FALSE(char_reg_type.IsNonZeroReferenceTypes());
 
-  RegType& short_reg_type = cache.Short();
+  const RegType& short_reg_type = cache.Short();
   EXPECT_FALSE(short_reg_type.IsUndefined());
   EXPECT_FALSE(short_reg_type.IsConflict());
   EXPECT_FALSE(short_reg_type.IsZero());
@@ -208,7 +208,7 @@ TEST_F(RegTypeTest, Primitives) {
   EXPECT_TRUE(short_reg_type.IsArrayIndexTypes());
   EXPECT_FALSE(short_reg_type.IsNonZeroReferenceTypes());
 
-  RegType& int_reg_type = cache.Integer();
+  const RegType& int_reg_type = cache.Integer();
   EXPECT_FALSE(int_reg_type.IsUndefined());
   EXPECT_FALSE(int_reg_type.IsConflict());
   EXPECT_FALSE(int_reg_type.IsZero());
@@ -240,7 +240,7 @@ TEST_F(RegTypeTest, Primitives) {
   EXPECT_TRUE(int_reg_type.IsArrayIndexTypes());
   EXPECT_FALSE(int_reg_type.IsNonZeroReferenceTypes());
 
-  RegType& long_reg_type = cache.LongLo();
+  const RegType& long_reg_type = cache.LongLo();
   EXPECT_FALSE(long_reg_type.IsUndefined());
   EXPECT_FALSE(long_reg_type.IsConflict());
   EXPECT_FALSE(long_reg_type.IsZero());
@@ -272,7 +272,7 @@ TEST_F(RegTypeTest, Primitives) {
   EXPECT_FALSE(long_reg_type.IsArrayIndexTypes());
   EXPECT_FALSE(long_reg_type.IsNonZeroReferenceTypes());
 
-  RegType& float_reg_type = cache.Float();
+  const RegType& float_reg_type = cache.Float();
   EXPECT_FALSE(float_reg_type.IsUndefined());
   EXPECT_FALSE(float_reg_type.IsConflict());
   EXPECT_FALSE(float_reg_type.IsZero());
@@ -304,7 +304,7 @@ TEST_F(RegTypeTest, Primitives) {
   EXPECT_FALSE(float_reg_type.IsArrayIndexTypes());
   EXPECT_FALSE(float_reg_type.IsNonZeroReferenceTypes());
 
-  RegType& double_reg_type = cache.DoubleLo();
+  const RegType& double_reg_type = cache.DoubleLo();
   EXPECT_FALSE(double_reg_type.IsUndefined());
   EXPECT_FALSE(double_reg_type.IsConflict());
   EXPECT_FALSE(double_reg_type.IsZero());
@@ -344,9 +344,9 @@ TEST_F(RegTypeReferenceTest, JavalangObjectImprecise) {
   // match the one that is imprecise.
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache(true);
-  RegType& imprecise_obj = cache.JavaLangObject(false);
-  RegType& precise_obj = cache.JavaLangObject(true);
-  RegType& precise_obj_2 = cache.FromDescriptor(NULL, "Ljava/lang/Object;", true);
+  const RegType& imprecise_obj = cache.JavaLangObject(false);
+  const RegType& precise_obj = cache.JavaLangObject(true);
+  const RegType& precise_obj_2 = cache.FromDescriptor(NULL, "Ljava/lang/Object;", true);
 
   EXPECT_TRUE(precise_obj.Equals(precise_obj_2));
   EXPECT_FALSE(imprecise_obj.Equals(precise_obj));
@@ -359,14 +359,14 @@ TEST_F(RegTypeReferenceTest, UnresolvedType) {
   // a hit second time.
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache(true);
-  RegType& ref_type_0 = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
+  const RegType& ref_type_0 = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
   EXPECT_TRUE(ref_type_0.IsUnresolvedReference());
   EXPECT_TRUE(ref_type_0.IsNonZeroReferenceTypes());
 
-  RegType& ref_type_1 = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
+  const RegType& ref_type_1 = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
   EXPECT_TRUE(ref_type_0.Equals(ref_type_1));
 
-  RegType& unresolved_super_class =  cache.FromUnresolvedSuperClass(ref_type_0);
+  const RegType& unresolved_super_class =  cache.FromUnresolvedSuperClass(ref_type_0);
   EXPECT_TRUE(unresolved_super_class.IsUnresolvedSuperClass());
   EXPECT_TRUE(unresolved_super_class.IsNonZeroReferenceTypes());
 }
@@ -375,21 +375,21 @@ TEST_F(RegTypeReferenceTest, UnresolvedUnintializedType) {
   // Tests creating types uninitialized types from unresolved types.
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache(true);
-  RegType& ref_type_0 = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
+  const RegType& ref_type_0 = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
   EXPECT_TRUE(ref_type_0.IsUnresolvedReference());
-  RegType& ref_type = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
+  const RegType& ref_type = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
   EXPECT_TRUE(ref_type_0.Equals(ref_type));
   // Create an uninitialized type of this unresolved type
-  RegType& unresolved_unintialised = cache.Uninitialized(ref_type, 1101ull);
+  const RegType& unresolved_unintialised = cache.Uninitialized(ref_type, 1101ull);
   EXPECT_TRUE(unresolved_unintialised.IsUnresolvedAndUninitializedReference());
   EXPECT_TRUE(unresolved_unintialised.IsUninitializedTypes());
   EXPECT_TRUE(unresolved_unintialised.IsNonZeroReferenceTypes());
   // Create an uninitialized type of this unresolved type with different  PC
-  RegType& ref_type_unresolved_unintialised_1 =  cache.Uninitialized(ref_type, 1102ull);
+  const RegType& ref_type_unresolved_unintialised_1 =  cache.Uninitialized(ref_type, 1102ull);
   EXPECT_TRUE(unresolved_unintialised.IsUnresolvedAndUninitializedReference());
   EXPECT_FALSE(unresolved_unintialised.Equals(ref_type_unresolved_unintialised_1));
   // Create an uninitialized type of this unresolved type with the same PC
-  RegType& unresolved_unintialised_2 = cache.Uninitialized(ref_type, 1101ull);
+  const RegType& unresolved_unintialised_2 = cache.Uninitialized(ref_type, 1101ull);
   EXPECT_TRUE(unresolved_unintialised.Equals(unresolved_unintialised_2));
 }
 
@@ -397,12 +397,12 @@ TEST_F(RegTypeReferenceTest, Dump) {
   // Tests types for proper Dump messages.
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache(true);
-  RegType& unresolved_ref = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
-  RegType& unresolved_ref_another = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExistEither;", true);
-  RegType& resolved_ref = cache.JavaLangString();
-  RegType& resolved_unintialiesd = cache.Uninitialized(resolved_ref, 10);
-  RegType& unresolved_unintialized = cache.Uninitialized(unresolved_ref, 12);
-  RegType& unresolved_merged = cache.FromUnresolvedMerge(unresolved_ref, unresolved_ref_another);
+  const RegType& unresolved_ref = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
+  const RegType& unresolved_ref_another = cache.FromDescriptor(NULL, "Ljava/lang/DoesNotExistEither;", true);
+  const RegType& resolved_ref = cache.JavaLangString();
+  const RegType& resolved_unintialiesd = cache.Uninitialized(resolved_ref, 10);
+  const RegType& unresolved_unintialized = cache.Uninitialized(unresolved_ref, 12);
+  const RegType& unresolved_merged = cache.FromUnresolvedMerge(unresolved_ref, unresolved_ref_another);
 
   std::string expected = "Unresolved Reference: java.lang.DoesNotExist";
   EXPECT_EQ(expected, unresolved_ref.Dump());
@@ -422,16 +422,16 @@ TEST_F(RegTypeReferenceTest, JavalangString) {
   // The JavaLangObject method instead of FromDescriptor. String class is final.
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache(true);
-  RegType& ref_type = cache.JavaLangString();
-  RegType& ref_type_2 = cache.JavaLangString();
-  RegType& ref_type_3 = cache.FromDescriptor(NULL, "Ljava/lang/String;", true);
+  const RegType& ref_type = cache.JavaLangString();
+  const RegType& ref_type_2 = cache.JavaLangString();
+  const RegType& ref_type_3 = cache.FromDescriptor(NULL, "Ljava/lang/String;", true);
 
   EXPECT_TRUE(ref_type.Equals(ref_type_2));
   EXPECT_TRUE(ref_type_2.Equals(ref_type_3));
   EXPECT_TRUE(ref_type.IsPreciseReference());
 
   // Create an uninitialized type out of this:
-  RegType& ref_type_unintialized = cache.Uninitialized(ref_type, 0110ull);
+  const RegType& ref_type_unintialized = cache.Uninitialized(ref_type, 0110ull);
   EXPECT_TRUE(ref_type_unintialized.IsUninitializedReference());
   EXPECT_FALSE(ref_type_unintialized.IsUnresolvedAndUninitializedReference());
 }
@@ -442,9 +442,9 @@ TEST_F(RegTypeReferenceTest, JavalangObject) {
   // The JavaLangObject method instead of FromDescriptor. Object Class in not final.
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache(true);
-  RegType& ref_type = cache.JavaLangObject(true);
-  RegType& ref_type_2 = cache.JavaLangObject(true);
-  RegType& ref_type_3 = cache.FromDescriptor(NULL, "Ljava/lang/Object;", true);
+  const RegType& ref_type = cache.JavaLangObject(true);
+  const RegType& ref_type_2 = cache.JavaLangObject(true);
+  const RegType& ref_type_3 = cache.FromDescriptor(NULL, "Ljava/lang/Object;", true);
 
   EXPECT_TRUE(ref_type.Equals(ref_type_2));
   EXPECT_TRUE(ref_type_3.Equals(ref_type_2));
@@ -455,19 +455,20 @@ TEST_F(RegTypeReferenceTest, Merging) {
   // String and object , LUB is object.
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache_new(true);
-  RegType& string = cache_new.JavaLangString();
-  RegType& Object = cache_new.JavaLangObject(true);
+  const RegType& string = cache_new.JavaLangString();
+  const RegType& Object = cache_new.JavaLangObject(true);
   EXPECT_TRUE(string.Merge(Object, &cache_new).IsJavaLangObject());
   // Merge two unresolved types.
-  RegType& ref_type_0 = cache_new.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
+  const RegType& ref_type_0 = cache_new.FromDescriptor(NULL, "Ljava/lang/DoesNotExist;", true);
   EXPECT_TRUE(ref_type_0.IsUnresolvedReference());
-  RegType& ref_type_1 = cache_new.FromDescriptor(NULL, "Ljava/lang/DoesNotExistToo;", true);
+  const RegType& ref_type_1 = cache_new.FromDescriptor(NULL, "Ljava/lang/DoesNotExistToo;", true);
   EXPECT_FALSE(ref_type_0.Equals(ref_type_1));
 
-  RegType& merged = ref_type_1.Merge(ref_type_0, &cache_new);
+  const RegType& merged = ref_type_1.Merge(ref_type_0, &cache_new);
   EXPECT_TRUE(merged.IsUnresolvedMergedReference());
+  RegType& merged_nonconst = const_cast<RegType&>(merged);
 
-  std::set<uint16_t> merged_ids = (down_cast<UnresolvedMergedType*>(&merged))->GetMergedTypes();
+  std::set<uint16_t> merged_ids = (down_cast<UnresolvedMergedType*>(&merged_nonconst))->GetMergedTypes();
   EXPECT_EQ(ref_type_0.GetId(), *(merged_ids.begin()));
   EXPECT_EQ(ref_type_1.GetId(), *((++merged_ids.begin())));
 }
@@ -478,27 +479,27 @@ TEST_F(RegTypeTest, MergingFloat) {
   RegTypeCache cache_new(true);
 
   constexpr int32_t kTestConstantValue = 10;
-  RegType& float_type = cache_new.Float();
-  RegType& precise_cst = cache_new.FromCat1Const(kTestConstantValue, true);
-  RegType& imprecise_cst = cache_new.FromCat1Const(kTestConstantValue, false);
+  const RegType& float_type = cache_new.Float();
+  const RegType& precise_cst = cache_new.FromCat1Const(kTestConstantValue, true);
+  const RegType& imprecise_cst = cache_new.FromCat1Const(kTestConstantValue, false);
   {
     // float MERGE precise cst => float.
-    RegType& merged = float_type.Merge(precise_cst, &cache_new);
+    const RegType& merged = float_type.Merge(precise_cst, &cache_new);
     EXPECT_TRUE(merged.IsFloat());
   }
   {
     // precise cst MERGE float => float.
-    RegType& merged = precise_cst.Merge(float_type, &cache_new);
+    const RegType& merged = precise_cst.Merge(float_type, &cache_new);
     EXPECT_TRUE(merged.IsFloat());
   }
   {
     // float MERGE imprecise cst => float.
-    RegType& merged = float_type.Merge(imprecise_cst, &cache_new);
+    const RegType& merged = float_type.Merge(imprecise_cst, &cache_new);
     EXPECT_TRUE(merged.IsFloat());
   }
   {
     // imprecise cst MERGE float => float.
-    RegType& merged = imprecise_cst.Merge(float_type, &cache_new);
+    const RegType& merged = imprecise_cst.Merge(float_type, &cache_new);
     EXPECT_TRUE(merged.IsFloat());
   }
 }
@@ -509,50 +510,50 @@ TEST_F(RegTypeTest, MergingLong) {
   RegTypeCache cache_new(true);
 
   constexpr int32_t kTestConstantValue = 10;
-  RegType& long_lo_type = cache_new.LongLo();
-  RegType& long_hi_type = cache_new.LongHi();
-  RegType& precise_cst_lo = cache_new.FromCat2ConstLo(kTestConstantValue, true);
-  RegType& imprecise_cst_lo = cache_new.FromCat2ConstLo(kTestConstantValue, false);
-  RegType& precise_cst_hi = cache_new.FromCat2ConstHi(kTestConstantValue, true);
-  RegType& imprecise_cst_hi = cache_new.FromCat2ConstHi(kTestConstantValue, false);
+  const RegType& long_lo_type = cache_new.LongLo();
+  const RegType& long_hi_type = cache_new.LongHi();
+  const RegType& precise_cst_lo = cache_new.FromCat2ConstLo(kTestConstantValue, true);
+  const RegType& imprecise_cst_lo = cache_new.FromCat2ConstLo(kTestConstantValue, false);
+  const RegType& precise_cst_hi = cache_new.FromCat2ConstHi(kTestConstantValue, true);
+  const RegType& imprecise_cst_hi = cache_new.FromCat2ConstHi(kTestConstantValue, false);
   {
     // lo MERGE precise cst lo => lo.
-    RegType& merged = long_lo_type.Merge(precise_cst_lo, &cache_new);
+    const RegType& merged = long_lo_type.Merge(precise_cst_lo, &cache_new);
     EXPECT_TRUE(merged.IsLongLo());
   }
   {
     // precise cst lo MERGE lo => lo.
-    RegType& merged = precise_cst_lo.Merge(long_lo_type, &cache_new);
+    const RegType& merged = precise_cst_lo.Merge(long_lo_type, &cache_new);
     EXPECT_TRUE(merged.IsLongLo());
   }
   {
     // lo MERGE imprecise cst lo => lo.
-    RegType& merged = long_lo_type.Merge(imprecise_cst_lo, &cache_new);
+    const RegType& merged = long_lo_type.Merge(imprecise_cst_lo, &cache_new);
     EXPECT_TRUE(merged.IsLongLo());
   }
   {
     // imprecise cst lo MERGE lo => lo.
-    RegType& merged = imprecise_cst_lo.Merge(long_lo_type, &cache_new);
+    const RegType& merged = imprecise_cst_lo.Merge(long_lo_type, &cache_new);
     EXPECT_TRUE(merged.IsLongLo());
   }
   {
     // hi MERGE precise cst hi => hi.
-    RegType& merged = long_hi_type.Merge(precise_cst_hi, &cache_new);
+    const RegType& merged = long_hi_type.Merge(precise_cst_hi, &cache_new);
     EXPECT_TRUE(merged.IsLongHi());
   }
   {
     // precise cst hi MERGE hi => hi.
-    RegType& merged = precise_cst_hi.Merge(long_hi_type, &cache_new);
+    const RegType& merged = precise_cst_hi.Merge(long_hi_type, &cache_new);
     EXPECT_TRUE(merged.IsLongHi());
   }
   {
     // hi MERGE imprecise cst hi => hi.
-    RegType& merged = long_hi_type.Merge(imprecise_cst_hi, &cache_new);
+    const RegType& merged = long_hi_type.Merge(imprecise_cst_hi, &cache_new);
     EXPECT_TRUE(merged.IsLongHi());
   }
   {
     // imprecise cst hi MERGE hi => hi.
-    RegType& merged = imprecise_cst_hi.Merge(long_hi_type, &cache_new);
+    const RegType& merged = imprecise_cst_hi.Merge(long_hi_type, &cache_new);
     EXPECT_TRUE(merged.IsLongHi());
   }
 }
@@ -563,50 +564,50 @@ TEST_F(RegTypeTest, MergingDouble) {
   RegTypeCache cache_new(true);
 
   constexpr int32_t kTestConstantValue = 10;
-  RegType& double_lo_type = cache_new.DoubleLo();
-  RegType& double_hi_type = cache_new.DoubleHi();
-  RegType& precise_cst_lo = cache_new.FromCat2ConstLo(kTestConstantValue, true);
-  RegType& imprecise_cst_lo = cache_new.FromCat2ConstLo(kTestConstantValue, false);
-  RegType& precise_cst_hi = cache_new.FromCat2ConstHi(kTestConstantValue, true);
-  RegType& imprecise_cst_hi = cache_new.FromCat2ConstHi(kTestConstantValue, false);
+  const RegType& double_lo_type = cache_new.DoubleLo();
+  const RegType& double_hi_type = cache_new.DoubleHi();
+  const RegType& precise_cst_lo = cache_new.FromCat2ConstLo(kTestConstantValue, true);
+  const RegType& imprecise_cst_lo = cache_new.FromCat2ConstLo(kTestConstantValue, false);
+  const RegType& precise_cst_hi = cache_new.FromCat2ConstHi(kTestConstantValue, true);
+  const RegType& imprecise_cst_hi = cache_new.FromCat2ConstHi(kTestConstantValue, false);
   {
     // lo MERGE precise cst lo => lo.
-    RegType& merged = double_lo_type.Merge(precise_cst_lo, &cache_new);
+    const RegType& merged = double_lo_type.Merge(precise_cst_lo, &cache_new);
     EXPECT_TRUE(merged.IsDoubleLo());
   }
   {
     // precise cst lo MERGE lo => lo.
-    RegType& merged = precise_cst_lo.Merge(double_lo_type, &cache_new);
+    const RegType& merged = precise_cst_lo.Merge(double_lo_type, &cache_new);
     EXPECT_TRUE(merged.IsDoubleLo());
   }
   {
     // lo MERGE imprecise cst lo => lo.
-    RegType& merged = double_lo_type.Merge(imprecise_cst_lo, &cache_new);
+    const RegType& merged = double_lo_type.Merge(imprecise_cst_lo, &cache_new);
     EXPECT_TRUE(merged.IsDoubleLo());
   }
   {
     // imprecise cst lo MERGE lo => lo.
-    RegType& merged = imprecise_cst_lo.Merge(double_lo_type, &cache_new);
+    const RegType& merged = imprecise_cst_lo.Merge(double_lo_type, &cache_new);
     EXPECT_TRUE(merged.IsDoubleLo());
   }
   {
     // hi MERGE precise cst hi => hi.
-    RegType& merged = double_hi_type.Merge(precise_cst_hi, &cache_new);
+    const RegType& merged = double_hi_type.Merge(precise_cst_hi, &cache_new);
     EXPECT_TRUE(merged.IsDoubleHi());
   }
   {
     // precise cst hi MERGE hi => hi.
-    RegType& merged = precise_cst_hi.Merge(double_hi_type, &cache_new);
+    const RegType& merged = precise_cst_hi.Merge(double_hi_type, &cache_new);
     EXPECT_TRUE(merged.IsDoubleHi());
   }
   {
     // hi MERGE imprecise cst hi => hi.
-    RegType& merged = double_hi_type.Merge(imprecise_cst_hi, &cache_new);
+    const RegType& merged = double_hi_type.Merge(imprecise_cst_hi, &cache_new);
     EXPECT_TRUE(merged.IsDoubleHi());
   }
   {
     // imprecise cst hi MERGE hi => hi.
-    RegType& merged = imprecise_cst_hi.Merge(double_hi_type, &cache_new);
+    const RegType& merged = imprecise_cst_hi.Merge(double_hi_type, &cache_new);
     EXPECT_TRUE(merged.IsDoubleHi());
   }
 }
@@ -615,8 +616,8 @@ TEST_F(RegTypeTest, ConstPrecision) {
   // Tests creating primitive types types.
   ScopedObjectAccess soa(Thread::Current());
   RegTypeCache cache_new(true);
-  RegType& imprecise_const = cache_new.FromCat1Const(10, false);
-  RegType& precise_const = cache_new.FromCat1Const(10, true);
+  const RegType& imprecise_const = cache_new.FromCat1Const(10, false);
+  const RegType& precise_const = cache_new.FromCat1Const(10, true);
 
   EXPECT_TRUE(imprecise_const.IsImpreciseConstant());
   EXPECT_TRUE(precise_const.IsPreciseConstant());
diff --git a/runtime/verifier/register_line-inl.h b/runtime/verifier/register_line-inl.h
index 378c6d3..0989cd0 100644
--- a/runtime/verifier/register_line-inl.h
+++ b/runtime/verifier/register_line-inl.h
@@ -25,7 +25,7 @@
 namespace art {
 namespace verifier {
 
-inline RegType& RegisterLine::GetRegisterType(uint32_t vsrc) const {
+inline const RegType& RegisterLine::GetRegisterType(uint32_t vsrc) const {
   // The register index was validated during the static pass, so we don't need to check it here.
   DCHECK_LT(vsrc, num_regs_);
   return verifier_->GetRegTypeCache()->GetFromId(line_[vsrc]);
diff --git a/runtime/verifier/register_line.cc b/runtime/verifier/register_line.cc
index 4d67cfb..556056c 100644
--- a/runtime/verifier/register_line.cc
+++ b/runtime/verifier/register_line.cc
@@ -36,7 +36,7 @@ bool RegisterLine::CheckConstructorReturn() const {
   return true;
 }
 
-bool RegisterLine::SetRegisterType(uint32_t vdst, RegType& new_type) {
+bool RegisterLine::SetRegisterType(uint32_t vdst, const RegType& new_type) {
   DCHECK_LT(vdst, num_regs_);
   if (new_type.IsLowHalf() || new_type.IsHighHalf()) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "Expected category1 register type not '"
@@ -53,8 +53,8 @@ bool RegisterLine::SetRegisterType(uint32_t vdst, RegType& new_type) {
   return true;
 }
 
-bool RegisterLine::SetRegisterTypeWide(uint32_t vdst, RegType& new_type1,
-                                       RegType& new_type2) {
+bool RegisterLine::SetRegisterTypeWide(uint32_t vdst, const RegType& new_type1,
+                                       const RegType& new_type2) {
   DCHECK_LT(vdst + 1, num_regs_);
   if (!new_type1.CheckWidePair(new_type2)) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_SOFT) << "Invalid wide pair '"
@@ -75,21 +75,21 @@ void RegisterLine::SetResultTypeToUnknown() {
   result_[1] = result_[0];
 }
 
-void RegisterLine::SetResultRegisterType(RegType& new_type) {
+void RegisterLine::SetResultRegisterType(const RegType& new_type) {
   DCHECK(!new_type.IsLowHalf());
   DCHECK(!new_type.IsHighHalf());
   result_[0] = new_type.GetId();
   result_[1] = verifier_->GetRegTypeCache()->Undefined().GetId();
 }
 
-void RegisterLine::SetResultRegisterTypeWide(RegType& new_type1,
-                                             RegType& new_type2) {
+void RegisterLine::SetResultRegisterTypeWide(const RegType& new_type1,
+                                             const RegType& new_type2) {
   DCHECK(new_type1.CheckWidePair(new_type2));
   result_[0] = new_type1.GetId();
   result_[1] = new_type2.GetId();
 }
 
-RegType& RegisterLine::GetInvocationThis(const Instruction* inst, bool is_range) {
+const RegType& RegisterLine::GetInvocationThis(const Instruction* inst, bool is_range) {
   const size_t args_count = is_range ? inst->VRegA_3rc() : inst->VRegA_35c();
   if (args_count < 1) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "invoke lacks 'this'";
@@ -97,7 +97,7 @@ RegType& RegisterLine::GetInvocationThis(const Instruction* inst, bool is_range)
   }
   /* Get the element type of the array held in vsrc */
   const uint32_t this_reg = (is_range) ? inst->VRegC_3rc() : inst->VRegC_35c();
-  RegType& this_type = GetRegisterType(this_reg);
+  const RegType& this_type = GetRegisterType(this_reg);
   if (!this_type.IsReferenceTypes()) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "tried to get class from non-reference register v"
                                                  << this_reg << " (type=" << this_type << ")";
@@ -107,9 +107,9 @@ RegType& RegisterLine::GetInvocationThis(const Instruction* inst, bool is_range)
 }
 
 bool RegisterLine::VerifyRegisterType(uint32_t vsrc,
-                                      RegType& check_type) {
+                                      const RegType& check_type) {
   // Verify the src register type against the check type refining the type of the register
-  RegType& src_type = GetRegisterType(vsrc);
+  const RegType& src_type = GetRegisterType(vsrc);
   if (!(check_type.IsAssignableFrom(src_type))) {
     enum VerifyError fail_type;
     if (!check_type.IsNonZeroReferenceTypes() || !src_type.IsNonZeroReferenceTypes()) {
@@ -125,7 +125,7 @@ bool RegisterLine::VerifyRegisterType(uint32_t vsrc,
     return false;
   }
   if (check_type.IsLowHalf()) {
-    RegType& src_type_h = GetRegisterType(vsrc + 1);
+    const RegType& src_type_h = GetRegisterType(vsrc + 1);
     if (!src_type.CheckWidePair(src_type_h)) {
       verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "wide register v" << vsrc << " has type "
                                                    << src_type << "/" << src_type_h;
@@ -139,17 +139,17 @@ bool RegisterLine::VerifyRegisterType(uint32_t vsrc,
   return true;
 }
 
-bool RegisterLine::VerifyRegisterTypeWide(uint32_t vsrc, RegType& check_type1,
-                                          RegType& check_type2) {
+bool RegisterLine::VerifyRegisterTypeWide(uint32_t vsrc, const RegType& check_type1,
+                                          const RegType& check_type2) {
   DCHECK(check_type1.CheckWidePair(check_type2));
   // Verify the src register type against the check type refining the type of the register
-  RegType& src_type = GetRegisterType(vsrc);
+  const RegType& src_type = GetRegisterType(vsrc);
   if (!check_type1.IsAssignableFrom(src_type)) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "register v" << vsrc << " has type " << src_type
                                << " but expected " << check_type1;
     return false;
   }
-  RegType& src_type_h = GetRegisterType(vsrc + 1);
+  const RegType& src_type_h = GetRegisterType(vsrc + 1);
   if (!src_type.CheckWidePair(src_type_h)) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "wide register v" << vsrc << " has type "
         << src_type << "/" << src_type_h;
@@ -162,9 +162,9 @@ bool RegisterLine::VerifyRegisterTypeWide(uint32_t vsrc, RegType& check_type1,
   return true;
 }
 
-void RegisterLine::MarkRefsAsInitialized(RegType& uninit_type) {
+void RegisterLine::MarkRefsAsInitialized(const RegType& uninit_type) {
   DCHECK(uninit_type.IsUninitializedTypes());
-  RegType& init_type = verifier_->GetRegTypeCache()->FromUninitialized(uninit_type);
+  const RegType& init_type = verifier_->GetRegTypeCache()->FromUninitialized(uninit_type);
   size_t changed = 0;
   for (uint32_t i = 0; i < num_regs_; i++) {
     if (GetRegisterType(i).Equals(uninit_type)) {
@@ -200,7 +200,7 @@ void RegisterLine::MarkAllRegistersAsConflictsExceptWide(uint32_t vsrc) {
   }
 }
 
-std::string RegisterLine::Dump() {
+std::string RegisterLine::Dump() const {
   std::string result;
   for (size_t i = 0; i < num_regs_; i++) {
     result += StringPrintf("%zd:[", i);
@@ -213,7 +213,7 @@ std::string RegisterLine::Dump() {
   return result;
 }
 
-void RegisterLine::MarkUninitRefsAsInvalid(RegType& uninit_type) {
+void RegisterLine::MarkUninitRefsAsInvalid(const RegType& uninit_type) {
   for (size_t i = 0; i < num_regs_; i++) {
     if (GetRegisterType(i).Equals(uninit_type)) {
       line_[i] = verifier_->GetRegTypeCache()->Conflict().GetId();
@@ -224,7 +224,7 @@ void RegisterLine::MarkUninitRefsAsInvalid(RegType& uninit_type) {
 
 void RegisterLine::CopyRegister1(uint32_t vdst, uint32_t vsrc, TypeCategory cat) {
   DCHECK(cat == kTypeCategory1nr || cat == kTypeCategoryRef);
-  RegType& type = GetRegisterType(vsrc);
+  const RegType& type = GetRegisterType(vsrc);
   if (!SetRegisterType(vdst, type)) {
     return;
   }
@@ -238,8 +238,8 @@ void RegisterLine::CopyRegister1(uint32_t vdst, uint32_t vsrc, TypeCategory cat)
 }
 
 void RegisterLine::CopyRegister2(uint32_t vdst, uint32_t vsrc) {
-  RegType& type_l = GetRegisterType(vsrc);
-  RegType& type_h = GetRegisterType(vsrc + 1);
+  const RegType& type_l = GetRegisterType(vsrc);
+  const RegType& type_h = GetRegisterType(vsrc + 1);
 
   if (!type_l.CheckWidePair(type_h)) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "copy2 v" << vdst << "<-v" << vsrc
@@ -250,7 +250,7 @@ void RegisterLine::CopyRegister2(uint32_t vdst, uint32_t vsrc) {
 }
 
 void RegisterLine::CopyResultRegister1(uint32_t vdst, bool is_reference) {
-  RegType& type = verifier_->GetRegTypeCache()->GetFromId(result_[0]);
+  const RegType& type = verifier_->GetRegTypeCache()->GetFromId(result_[0]);
   if ((!is_reference && !type.IsCategory1Types()) ||
       (is_reference && !type.IsReferenceTypes())) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD)
@@ -267,8 +267,8 @@ void RegisterLine::CopyResultRegister1(uint32_t vdst, bool is_reference) {
  * register to another register, and reset the result register.
  */
 void RegisterLine::CopyResultRegister2(uint32_t vdst) {
-  RegType& type_l = verifier_->GetRegTypeCache()->GetFromId(result_[0]);
-  RegType& type_h = verifier_->GetRegTypeCache()->GetFromId(result_[1]);
+  const RegType& type_l = verifier_->GetRegTypeCache()->GetFromId(result_[0]);
+  const RegType& type_h = verifier_->GetRegTypeCache()->GetFromId(result_[1]);
   if (!type_l.IsCategory2Types()) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD)
         << "copyRes2 v" << vdst << "<- result0"  << " type=" << type_l;
@@ -281,40 +281,40 @@ void RegisterLine::CopyResultRegister2(uint32_t vdst) {
 }
 
 void RegisterLine::CheckUnaryOp(const Instruction* inst,
-                                RegType& dst_type,
-                                RegType& src_type) {
+                                const RegType& dst_type,
+                                const RegType& src_type) {
   if (VerifyRegisterType(inst->VRegB_12x(), src_type)) {
     SetRegisterType(inst->VRegA_12x(), dst_type);
   }
 }
 
 void RegisterLine::CheckUnaryOpWide(const Instruction* inst,
-                                    RegType& dst_type1, RegType& dst_type2,
-                                    RegType& src_type1, RegType& src_type2) {
+                                    const RegType& dst_type1, const RegType& dst_type2,
+                                    const RegType& src_type1, const RegType& src_type2) {
   if (VerifyRegisterTypeWide(inst->VRegB_12x(), src_type1, src_type2)) {
     SetRegisterTypeWide(inst->VRegA_12x(), dst_type1, dst_type2);
   }
 }
 
 void RegisterLine::CheckUnaryOpToWide(const Instruction* inst,
-                                      RegType& dst_type1, RegType& dst_type2,
-                                      RegType& src_type) {
+                                      const RegType& dst_type1, const RegType& dst_type2,
+                                      const RegType& src_type) {
   if (VerifyRegisterType(inst->VRegB_12x(), src_type)) {
     SetRegisterTypeWide(inst->VRegA_12x(), dst_type1, dst_type2);
   }
 }
 
 void RegisterLine::CheckUnaryOpFromWide(const Instruction* inst,
-                                        RegType& dst_type,
-                                        RegType& src_type1, RegType& src_type2) {
+                                        const RegType& dst_type,
+                                        const RegType& src_type1, const RegType& src_type2) {
   if (VerifyRegisterTypeWide(inst->VRegB_12x(), src_type1, src_type2)) {
     SetRegisterType(inst->VRegA_12x(), dst_type);
   }
 }
 
 void RegisterLine::CheckBinaryOp(const Instruction* inst,
-                                 RegType& dst_type,
-                                 RegType& src_type1, RegType& src_type2,
+                                 const RegType& dst_type,
+                                 const RegType& src_type1, const RegType& src_type2,
                                  bool check_boolean_op) {
   const uint32_t vregB = inst->VRegB_23x();
   const uint32_t vregC = inst->VRegC_23x();
@@ -333,9 +333,9 @@ void RegisterLine::CheckBinaryOp(const Instruction* inst,
 }
 
 void RegisterLine::CheckBinaryOpWide(const Instruction* inst,
-                                     RegType& dst_type1, RegType& dst_type2,
-                                     RegType& src_type1_1, RegType& src_type1_2,
-                                     RegType& src_type2_1, RegType& src_type2_2) {
+                                     const RegType& dst_type1, const RegType& dst_type2,
+                                     const RegType& src_type1_1, const RegType& src_type1_2,
+                                     const RegType& src_type2_1, const RegType& src_type2_2) {
   if (VerifyRegisterTypeWide(inst->VRegB_23x(), src_type1_1, src_type1_2) &&
       VerifyRegisterTypeWide(inst->VRegC_23x(), src_type2_1, src_type2_2)) {
     SetRegisterTypeWide(inst->VRegA_23x(), dst_type1, dst_type2);
@@ -343,8 +343,8 @@ void RegisterLine::CheckBinaryOpWide(const Instruction* inst,
 }
 
 void RegisterLine::CheckBinaryOpWideShift(const Instruction* inst,
-                                          RegType& long_lo_type, RegType& long_hi_type,
-                                          RegType& int_type) {
+                                          const RegType& long_lo_type, const RegType& long_hi_type,
+                                          const RegType& int_type) {
   if (VerifyRegisterTypeWide(inst->VRegB_23x(), long_lo_type, long_hi_type) &&
       VerifyRegisterType(inst->VRegC_23x(), int_type)) {
     SetRegisterTypeWide(inst->VRegA_23x(), long_lo_type, long_hi_type);
@@ -352,8 +352,8 @@ void RegisterLine::CheckBinaryOpWideShift(const Instruction* inst,
 }
 
 void RegisterLine::CheckBinaryOp2addr(const Instruction* inst,
-                                      RegType& dst_type, RegType& src_type1,
-                                      RegType& src_type2, bool check_boolean_op) {
+                                      const RegType& dst_type, const RegType& src_type1,
+                                      const RegType& src_type2, bool check_boolean_op) {
   const uint32_t vregA = inst->VRegA_12x();
   const uint32_t vregB = inst->VRegB_12x();
   if (VerifyRegisterType(vregA, src_type1) &&
@@ -371,9 +371,9 @@ void RegisterLine::CheckBinaryOp2addr(const Instruction* inst,
 }
 
 void RegisterLine::CheckBinaryOp2addrWide(const Instruction* inst,
-                                          RegType& dst_type1, RegType& dst_type2,
-                                          RegType& src_type1_1, RegType& src_type1_2,
-                                          RegType& src_type2_1, RegType& src_type2_2) {
+                                          const RegType& dst_type1, const RegType& dst_type2,
+                                          const RegType& src_type1_1, const RegType& src_type1_2,
+                                          const RegType& src_type2_1, const RegType& src_type2_2) {
   const uint32_t vregA = inst->VRegA_12x();
   const uint32_t vregB = inst->VRegB_12x();
   if (VerifyRegisterTypeWide(vregA, src_type1_1, src_type1_2) &&
@@ -383,8 +383,8 @@ void RegisterLine::CheckBinaryOp2addrWide(const Instruction* inst,
 }
 
 void RegisterLine::CheckBinaryOp2addrWideShift(const Instruction* inst,
-                                               RegType& long_lo_type, RegType& long_hi_type,
-                                               RegType& int_type) {
+                                               const RegType& long_lo_type, const RegType& long_hi_type,
+                                               const RegType& int_type) {
   const uint32_t vregA = inst->VRegA_12x();
   const uint32_t vregB = inst->VRegB_12x();
   if (VerifyRegisterTypeWide(vregA, long_lo_type, long_hi_type) &&
@@ -394,7 +394,7 @@ void RegisterLine::CheckBinaryOp2addrWideShift(const Instruction* inst,
 }
 
 void RegisterLine::CheckLiteralOp(const Instruction* inst,
-                                  RegType& dst_type, RegType& src_type,
+                                  const RegType& dst_type, const RegType& src_type,
                                   bool check_boolean_op, bool is_lit16) {
   const uint32_t vregA = is_lit16 ? inst->VRegA_22s() : inst->VRegA_22b();
   const uint32_t vregB = is_lit16 ? inst->VRegB_22s() : inst->VRegB_22b();
@@ -413,7 +413,7 @@ void RegisterLine::CheckLiteralOp(const Instruction* inst,
 }
 
 void RegisterLine::PushMonitor(uint32_t reg_idx, int32_t insn_idx) {
-  RegType& reg_type = GetRegisterType(reg_idx);
+  const RegType& reg_type = GetRegisterType(reg_idx);
   if (!reg_type.IsReferenceTypes()) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "monitor-enter on non-object (" << reg_type << ")";
   } else if (monitors_.size() >= 32) {
@@ -425,7 +425,7 @@ void RegisterLine::PushMonitor(uint32_t reg_idx, int32_t insn_idx) {
 }
 
 void RegisterLine::PopMonitor(uint32_t reg_idx) {
-  RegType& reg_type = GetRegisterType(reg_idx);
+  const RegType& reg_type = GetRegisterType(reg_idx);
   if (!reg_type.IsReferenceTypes()) {
     verifier_->Fail(VERIFY_ERROR_BAD_CLASS_HARD) << "monitor-exit on non-object (" << reg_type << ")";
   } else if (monitors_.empty()) {
@@ -460,9 +460,9 @@ bool RegisterLine::MergeRegisters(const RegisterLine* incoming_line) {
   DCHECK(incoming_line != nullptr);
   for (size_t idx = 0; idx < num_regs_; idx++) {
     if (line_[idx] != incoming_line->line_[idx]) {
-      RegType& incoming_reg_type = incoming_line->GetRegisterType(idx);
-      RegType& cur_type = GetRegisterType(idx);
-      RegType& new_type = cur_type.Merge(incoming_reg_type, verifier_->GetRegTypeCache());
+      const RegType& incoming_reg_type = incoming_line->GetRegisterType(idx);
+      const RegType& cur_type = GetRegisterType(idx);
+      const RegType& new_type = cur_type.Merge(incoming_reg_type, verifier_->GetRegTypeCache());
       changed = changed || !cur_type.Equals(new_type);
       line_[idx] = new_type.GetId();
     }
@@ -508,8 +508,7 @@ void RegisterLine::WriteReferenceBitMap(std::vector<uint8_t>& data, size_t max_b
 
 std::ostream& operator<<(std::ostream& os, const RegisterLine& rhs)
     SHARED_LOCKS_REQUIRED(Locks::mutator_lock_) {
-  RegisterLine& rhs_non_const = const_cast<RegisterLine&>(rhs);
-  os << rhs_non_const.Dump();
+  os << rhs.Dump();
   return os;
 }
 
diff --git a/runtime/verifier/register_line.h b/runtime/verifier/register_line.h
index 06b7cca..a9d0dbb 100644
--- a/runtime/verifier/register_line.h
+++ b/runtime/verifier/register_line.h
@@ -81,26 +81,26 @@ class RegisterLine {
   // Set the type of register N, verifying that the register is valid.  If "newType" is the "Lo"
   // part of a 64-bit value, register N+1 will be set to "newType+1".
   // The register index was validated during the static pass, so we don't need to check it here.
-  bool SetRegisterType(uint32_t vdst, RegType& new_type)
+  bool SetRegisterType(uint32_t vdst, const RegType& new_type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  bool SetRegisterTypeWide(uint32_t vdst, RegType& new_type1, RegType& new_type2)
+  bool SetRegisterTypeWide(uint32_t vdst, const RegType& new_type1, const RegType& new_type2)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   /* Set the type of the "result" register. */
-  void SetResultRegisterType(RegType& new_type)
+  void SetResultRegisterType(const RegType& new_type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  void SetResultRegisterTypeWide(RegType& new_type1, RegType& new_type2)
+  void SetResultRegisterTypeWide(const RegType& new_type1, const RegType& new_type2)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   // Get the type of register vsrc.
-  RegType& GetRegisterType(uint32_t vsrc) const;
+  const RegType& GetRegisterType(uint32_t vsrc) const;
 
-  bool VerifyRegisterType(uint32_t vsrc, RegType& check_type)
+  bool VerifyRegisterType(uint32_t vsrc, const RegType& check_type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
-  bool VerifyRegisterTypeWide(uint32_t vsrc, RegType& check_type1, RegType& check_type2)
+  bool VerifyRegisterTypeWide(uint32_t vsrc, const RegType& check_type1, const RegType& check_type2)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void CopyFromLine(const RegisterLine* src) {
@@ -110,7 +110,7 @@ class RegisterLine {
     reg_to_lock_depths_ = src->reg_to_lock_depths_;
   }
 
-  std::string Dump() SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
+  std::string Dump() const SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void FillWithGarbage() {
     memset(&line_, 0xf1, num_regs_ * sizeof(uint16_t));
@@ -126,7 +126,7 @@ class RegisterLine {
    * to prevent them from being used (otherwise, MarkRefsAsInitialized would mark the old ones and
    * the new ones at the same time).
    */
-  void MarkUninitRefsAsInvalid(RegType& uninit_type)
+  void MarkUninitRefsAsInvalid(const RegType& uninit_type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   /*
@@ -134,7 +134,7 @@ class RegisterLine {
    * reference type. This is called when an appropriate constructor is invoked -- all copies of
    * the reference must be marked as initialized.
    */
-  void MarkRefsAsInitialized(RegType& uninit_type)
+  void MarkRefsAsInitialized(const RegType& uninit_type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   /*
@@ -173,30 +173,30 @@ class RegisterLine {
    * The argument count is in vA, and the first argument is in vC, for both "simple" and "range"
    * versions. We just need to make sure vA is >= 1 and then return vC.
    */
-  RegType& GetInvocationThis(const Instruction* inst, bool is_range)
+  const RegType& GetInvocationThis(const Instruction* inst, bool is_range)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   /*
    * Verify types for a simple two-register instruction (e.g. "neg-int").
    * "dst_type" is stored into vA, and "src_type" is verified against vB.
    */
-  void CheckUnaryOp(const Instruction* inst, RegType& dst_type,
-                    RegType& src_type)
+  void CheckUnaryOp(const Instruction* inst, const RegType& dst_type,
+                    const RegType& src_type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void CheckUnaryOpWide(const Instruction* inst,
-                        RegType& dst_type1, RegType& dst_type2,
-                        RegType& src_type1, RegType& src_type2)
+                        const RegType& dst_type1, const RegType& dst_type2,
+                        const RegType& src_type1, const RegType& src_type2)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void CheckUnaryOpToWide(const Instruction* inst,
-                          RegType& dst_type1, RegType& dst_type2,
-                          RegType& src_type)
+                          const RegType& dst_type1, const RegType& dst_type2,
+                          const RegType& src_type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void CheckUnaryOpFromWide(const Instruction* inst,
-                            RegType& dst_type,
-                            RegType& src_type1, RegType& src_type2)
+                            const RegType& dst_type,
+                            const RegType& src_type1, const RegType& src_type2)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   /*
@@ -205,19 +205,19 @@ class RegisterLine {
    * against vB/vC.
    */
   void CheckBinaryOp(const Instruction* inst,
-                     RegType& dst_type, RegType& src_type1, RegType& src_type2,
+                     const RegType& dst_type, const RegType& src_type1, const RegType& src_type2,
                      bool check_boolean_op)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void CheckBinaryOpWide(const Instruction* inst,
-                         RegType& dst_type1, RegType& dst_type2,
-                         RegType& src_type1_1, RegType& src_type1_2,
-                         RegType& src_type2_1, RegType& src_type2_2)
+                         const RegType& dst_type1, const RegType& dst_type2,
+                         const RegType& src_type1_1, const RegType& src_type1_2,
+                         const RegType& src_type2_1, const RegType& src_type2_2)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void CheckBinaryOpWideShift(const Instruction* inst,
-                              RegType& long_lo_type, RegType& long_hi_type,
-                              RegType& int_type)
+                              const RegType& long_lo_type, const RegType& long_hi_type,
+                              const RegType& int_type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   /*
@@ -225,20 +225,20 @@ class RegisterLine {
    * are verified against vA/vB, then "dst_type" is stored into vA.
    */
   void CheckBinaryOp2addr(const Instruction* inst,
-                          RegType& dst_type,
-                          RegType& src_type1, RegType& src_type2,
+                          const RegType& dst_type,
+                          const RegType& src_type1, const RegType& src_type2,
                           bool check_boolean_op)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void CheckBinaryOp2addrWide(const Instruction* inst,
-                              RegType& dst_type1, RegType& dst_type2,
-                              RegType& src_type1_1, RegType& src_type1_2,
-                              RegType& src_type2_1, RegType& src_type2_2)
+                              const RegType& dst_type1, const RegType& dst_type2,
+                              const RegType& src_type1_1, const RegType& src_type1_2,
+                              const RegType& src_type2_1, const RegType& src_type2_2)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   void CheckBinaryOp2addrWideShift(const Instruction* inst,
-                                   RegType& long_lo_type, RegType& long_hi_type,
-                                   RegType& int_type)
+                                   const RegType& long_lo_type, const RegType& long_hi_type,
+                                   const RegType& int_type)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);
 
   /*
@@ -248,7 +248,7 @@ class RegisterLine {
    * If "check_boolean_op" is set, we use the constant value in vC.
    */
   void CheckLiteralOp(const Instruction* inst,
-                      RegType& dst_type, RegType& src_type,
+                      const RegType& dst_type, const RegType& src_type,
                       bool check_boolean_op, bool is_lit16)
       SHARED_LOCKS_REQUIRED(Locks::mutator_lock_);