Avoid use of std::string where we have const char*.

Removing the ClassHelper caused std::string creation for all calls to
Class::GetDescriptor and a significant performance regression. Make the
std::string an out argument so the caller can maintain it and its life time
while allowing GetDescriptor to return the common const char* case.

Don't generate GC maps when compilation is disabled.

Remove other uses of std::string that are occuring on critical paths.
Use the cheaper SkipClass in CompileMethod in CompilerDriver.
Specialize the utf8 as utf16 comparison code for the common shorter byte
encoding.
Force a bit of inlining, remove some UNLIKELYs (they are prone to pessimizing
code), add some LIKELYs.

x86-64 host 1-thread interpret-only of 57 apks:
Before: 29.539s
After: 23.467s

Regular compile:
Before: 1m35.347s
After: 1m20.056s

Bug: 16853450
Change-Id: Ic705ea24784bee24ab80084d06174cbf87d557ad

3 files changed, 18 insertions, 12 deletions

diff --git a/runtime/interpreter/interpreter_common.cc b/runtime/interpreter/interpreter_common.cc
index b35da0c..6705695 100644
--- a/runtime/interpreter/interpreter_common.cc
+++ b/runtime/interpreter/interpreter_common.cc
@@ -270,12 +270,13 @@ bool DoFieldPut(Thread* self, const ShadowFrame& shadow_frame, const Instruction
         }
         if (!reg->VerifierInstanceOf(field_class)) {
           // This should never happen.
+          std::string temp1, temp2, temp3;
           self->ThrowNewExceptionF(self->GetCurrentLocationForThrow(),
                                    "Ljava/lang/VirtualMachineError;",
                                    "Put '%s' that is not instance of field '%s' in '%s'",
-                                   reg->GetClass()->GetDescriptor().c_str(),
-                                   field_class->GetDescriptor().c_str(),
-                                   f->GetDeclaringClass()->GetDescriptor().c_str());
+                                   reg->GetClass()->GetDescriptor(&temp1),
+                                   field_class->GetDescriptor(&temp2),
+                                   f->GetDeclaringClass()->GetDescriptor(&temp3));
           return false;
         }
       }
@@ -588,12 +589,13 @@ bool DoCall(ArtMethod* method, Thread* self, ShadowFrame& shadow_frame,
             }
             if (!o->VerifierInstanceOf(arg_type)) {
               // This should never happen.
+              std::string temp1, temp2;
               self->ThrowNewExceptionF(self->GetCurrentLocationForThrow(),
                                        "Ljava/lang/VirtualMachineError;",
                                        "Invoking %s with bad arg %d, type '%s' not instance of '%s'",
                                        method->GetName(), shorty_pos,
-                                       o->GetClass()->GetDescriptor().c_str(),
-                                       arg_type->GetDescriptor().c_str());
+                                       o->GetClass()->GetDescriptor(&temp1),
+                                       arg_type->GetDescriptor(&temp2));
               return false;
             }
           }
@@ -775,7 +777,7 @@ static void UnstartedRuntimeFindClass(Thread* self, Handle<mirror::String> class
   if (found == nullptr && abort_if_not_found) {
     if (!self->IsExceptionPending()) {
       AbortTransaction(self, "%s failed in un-started runtime for class: %s",
-                       method_name.c_str(), PrettyDescriptor(descriptor).c_str());
+                       method_name.c_str(), PrettyDescriptor(descriptor.c_str()).c_str());
     }
     return;
   }
diff --git a/runtime/interpreter/interpreter_goto_table_impl.cc b/runtime/interpreter/interpreter_goto_table_impl.cc
index abd4b44..e098ac8 100644
--- a/runtime/interpreter/interpreter_goto_table_impl.cc
+++ b/runtime/interpreter/interpreter_goto_table_impl.cc
@@ -341,11 +341,12 @@ JValue ExecuteGotoImpl(Thread* self, MethodHelper& mh, const DexFile::CodeItem*
       }
       if (!obj_result->VerifierInstanceOf(return_type)) {
         // This should never happen.
+        std::string temp1, temp2;
         self->ThrowNewExceptionF(self->GetCurrentLocationForThrow(),
                                  "Ljava/lang/VirtualMachineError;",
                                  "Returning '%s' that is not instance of return type '%s'",
-                                 obj_result->GetClass()->GetDescriptor().c_str(),
-                                 return_type->GetDescriptor().c_str());
+                                 obj_result->GetClass()->GetDescriptor(&temp1),
+                                 return_type->GetDescriptor(&temp2));
         HANDLE_PENDING_EXCEPTION();
       }
     }
@@ -615,10 +616,11 @@ JValue ExecuteGotoImpl(Thread* self, MethodHelper& mh, const DexFile::CodeItem*
       ThrowNullPointerException(NULL, "throw with null exception");
     } else if (do_assignability_check && !exception->GetClass()->IsThrowableClass()) {
       // This should never happen.
+      std::string temp;
       self->ThrowNewExceptionF(self->GetCurrentLocationForThrow(),
                                "Ljava/lang/VirtualMachineError;",
                                "Throwing '%s' that is not instance of Throwable",
-                               exception->GetClass()->GetDescriptor().c_str());
+                               exception->GetClass()->GetDescriptor(&temp));
     } else {
       self->SetException(shadow_frame.GetCurrentLocationForThrow(), exception->AsThrowable());
     }
diff --git a/runtime/interpreter/interpreter_switch_impl.cc b/runtime/interpreter/interpreter_switch_impl.cc
index c635648..5401495 100644
--- a/runtime/interpreter/interpreter_switch_impl.cc
+++ b/runtime/interpreter/interpreter_switch_impl.cc
@@ -256,11 +256,12 @@ JValue ExecuteSwitchImpl(Thread* self, MethodHelper& mh, const DexFile::CodeItem
           }
           if (!obj_result->VerifierInstanceOf(return_type)) {
             // This should never happen.
+            std::string temp1, temp2;
             self->ThrowNewExceptionF(self->GetCurrentLocationForThrow(),
                                      "Ljava/lang/VirtualMachineError;",
                                      "Returning '%s' that is not instance of return type '%s'",
-                                     obj_result->GetClass()->GetDescriptor().c_str(),
-                                     return_type->GetDescriptor().c_str());
+                                     obj_result->GetClass()->GetDescriptor(&temp1),
+                                     return_type->GetDescriptor(&temp2));
             HANDLE_PENDING_EXCEPTION();
           }
         }
@@ -529,10 +530,11 @@ JValue ExecuteSwitchImpl(Thread* self, MethodHelper& mh, const DexFile::CodeItem
           ThrowNullPointerException(NULL, "throw with null exception");
         } else if (do_assignability_check && !exception->GetClass()->IsThrowableClass()) {
           // This should never happen.
+          std::string temp;
           self->ThrowNewExceptionF(self->GetCurrentLocationForThrow(),
                                    "Ljava/lang/VirtualMachineError;",
                                    "Throwing '%s' that is not instance of Throwable",
-                                   exception->GetClass()->GetDescriptor().c_str());
+                                   exception->GetClass()->GetDescriptor(&temp));
         } else {
           self->SetException(shadow_frame.GetCurrentLocationForThrow(), exception->AsThrowable());
         }