Fix code generation with materialized conditions.

Change-Id: I8630af3c13fc1950d3fa718d7488407b00898796

6 files changed, 57 insertions, 21 deletions

diff --git a/compiler/optimizing/code_generator_arm.cc b/compiler/optimizing/code_generator_arm.cc
index ad62279..804d352 100644
--- a/compiler/optimizing/code_generator_arm.cc
+++ b/compiler/optimizing/code_generator_arm.cc
@@ -577,7 +577,7 @@ void LocationsBuilderARM::VisitIf(HIf* if_instr) {
   DCHECK(cond->IsCondition());
   HCondition* condition = cond->AsCondition();
   if (condition->NeedsMaterialization()) {
-    locations->SetInAt(0, Location::Any());
+    locations->SetInAt(0, Location::RequiresRegister());
   }
 }
 
@@ -590,7 +590,7 @@ void InstructionCodeGeneratorARM::VisitIf(HIf* if_instr) {
     DCHECK(if_instr->GetLocations()->InAt(0).IsRegister());
     __ cmp(if_instr->GetLocations()->InAt(0).AsArm().AsCoreRegister(),
            ShifterOperand(0));
-    __ b(codegen_->GetLabelOf(if_instr->IfTrueSuccessor()), EQ);
+    __ b(codegen_->GetLabelOf(if_instr->IfTrueSuccessor()), NE);
   } else {
     // Condition has not been materialized, use its inputs as the comparison and its
     // condition as the branch condition.
diff --git a/compiler/optimizing/code_generator_x86.cc b/compiler/optimizing/code_generator_x86.cc
index 3383cb2..f7b8495 100644
--- a/compiler/optimizing/code_generator_x86.cc
+++ b/compiler/optimizing/code_generator_x86.cc
@@ -541,14 +541,18 @@ void InstructionCodeGeneratorX86::VisitIf(HIf* if_instr) {
   DCHECK(cond->IsCondition());
   HCondition* condition = cond->AsCondition();
   if (condition->NeedsMaterialization()) {
-    // Materialized condition, compare against 0
-    Location lhs = if_instr->GetLocations()->InAt(0);
-    if (lhs.IsRegister()) {
-      __ cmpl(lhs.AsX86().AsCpuRegister(), Immediate(0));
-    } else {
-      __ cmpl(Address(ESP, lhs.GetStackIndex()), Immediate(0));
+    // Moves do not affect the eflags register, so if the condition is evaluated
+    // just before the if, we don't need to evaluate it again.
+    if (!condition->IsBeforeWhenDisregardMoves(if_instr)) {
+      // Materialized condition, compare against 0
+      Location lhs = if_instr->GetLocations()->InAt(0);
+      if (lhs.IsRegister()) {
+        __ cmpl(lhs.AsX86().AsCpuRegister(), Immediate(0));
+      } else {
+        __ cmpl(Address(ESP, lhs.GetStackIndex()), Immediate(0));
+      }
     }
-    __ j(kEqual,  codegen_->GetLabelOf(if_instr->IfTrueSuccessor()));
+    __ j(kNotEqual,  codegen_->GetLabelOf(if_instr->IfTrueSuccessor()));
   } else {
     Location lhs = condition->GetLocations()->InAt(0);
     Location rhs = condition->GetLocations()->InAt(1);
@@ -625,6 +629,9 @@ void LocationsBuilderX86::VisitCondition(HCondition* comp) {
 void InstructionCodeGeneratorX86::VisitCondition(HCondition* comp) {
   if (comp->NeedsMaterialization()) {
     LocationSummary* locations = comp->GetLocations();
+    Register reg = locations->Out().AsX86().AsCpuRegister();
+    // Clear register: setcc only sets the low byte.
+    __ xorl(reg, reg);
     if (locations->InAt(1).IsRegister()) {
       __ cmpl(locations->InAt(0).AsX86().AsCpuRegister(),
               locations->InAt(1).AsX86().AsCpuRegister());
@@ -636,7 +643,7 @@ void InstructionCodeGeneratorX86::VisitCondition(HCondition* comp) {
       __ cmpl(locations->InAt(0).AsX86().AsCpuRegister(),
               Address(ESP, locations->InAt(1).GetStackIndex()));
     }
-    __ setb(X86Condition(comp->GetCondition()), locations->Out().AsX86().AsCpuRegister());
+    __ setb(X86Condition(comp->GetCondition()), reg);
   }
 }
 
diff --git a/compiler/optimizing/code_generator_x86_64.cc b/compiler/optimizing/code_generator_x86_64.cc
index ca03af8..283d850 100644
--- a/compiler/optimizing/code_generator_x86_64.cc
+++ b/compiler/optimizing/code_generator_x86_64.cc
@@ -424,14 +424,18 @@ void InstructionCodeGeneratorX86_64::VisitIf(HIf* if_instr) {
   DCHECK(cond->IsCondition());
   HCondition* condition = cond->AsCondition();
   if (condition->NeedsMaterialization()) {
-    // Materialized condition, compare against 0.
-    Location lhs = if_instr->GetLocations()->InAt(0);
-    if (lhs.IsRegister()) {
-      __ cmpl(lhs.AsX86_64().AsCpuRegister(), Immediate(0));
-    } else {
-      __ cmpl(Address(CpuRegister(RSP), lhs.GetStackIndex()), Immediate(0));
+    // Moves do not affect the eflags register, so if the condition is evaluated
+    // just before the if, we don't need to evaluate it again.
+    if (!condition->IsBeforeWhenDisregardMoves(if_instr)) {
+      // Materialized condition, compare against 0.
+      Location lhs = if_instr->GetLocations()->InAt(0);
+      if (lhs.IsRegister()) {
+        __ cmpl(lhs.AsX86_64().AsCpuRegister(), Immediate(0));
+      } else {
+        __ cmpl(Address(CpuRegister(RSP), lhs.GetStackIndex()), Immediate(0));
+      }
     }
-    __ j(kEqual, codegen_->GetLabelOf(if_instr->IfTrueSuccessor()));
+    __ j(kNotEqual, codegen_->GetLabelOf(if_instr->IfTrueSuccessor()));
   } else {
     Location lhs = condition->GetLocations()->InAt(0);
     Location rhs = condition->GetLocations()->InAt(1);
@@ -505,6 +509,9 @@ void LocationsBuilderX86_64::VisitCondition(HCondition* comp) {
 void InstructionCodeGeneratorX86_64::VisitCondition(HCondition* comp) {
   if (comp->NeedsMaterialization()) {
     LocationSummary* locations = comp->GetLocations();
+    CpuRegister reg = locations->Out().AsX86_64().AsCpuRegister();
+    // Clear register: setcc only sets the low byte.
+    __ xorq(reg, reg);
     if (locations->InAt(1).IsRegister()) {
       __ cmpq(locations->InAt(0).AsX86_64().AsCpuRegister(),
               locations->InAt(1).AsX86_64().AsCpuRegister());
@@ -515,8 +522,7 @@ void InstructionCodeGeneratorX86_64::VisitCondition(HCondition* comp) {
       __ cmpq(locations->InAt(0).AsX86_64().AsCpuRegister(),
               Address(CpuRegister(RSP), locations->InAt(1).GetStackIndex()));
     }
-    __ setcc(X86_64Condition(comp->GetCondition()),
-             comp->GetLocations()->Out().AsX86_64().AsCpuRegister());
+    __ setcc(X86_64Condition(comp->GetCondition()), reg);
   }
 }
 
diff --git a/compiler/optimizing/graph_visualizer.cc b/compiler/optimizing/graph_visualizer.cc
index 7f64be4..0fb4737 100644
--- a/compiler/optimizing/graph_visualizer.cc
+++ b/compiler/optimizing/graph_visualizer.cc
@@ -82,6 +82,8 @@ class HGraphVisualizerPrinter : public HGraphVisitor {
   }
 
   char GetTypeId(Primitive::Type type) {
+    // Note that Primitive::Descriptor would not work for us
+    // because it does not handle reference types (that is kPrimNot).
     switch (type) {
       case Primitive::kPrimBoolean: return 'z';
       case Primitive::kPrimByte: return 'b';
@@ -127,6 +129,12 @@ class HGraphVisualizerPrinter : public HGraphVisitor {
       }
     } else if (location.IsConstant()) {
       output_ << "constant";
+      HConstant* constant = location.GetConstant();
+      if (constant->IsIntConstant()) {
+        output_ << " " << constant->AsIntConstant()->GetValue();
+      } else if (constant->IsLongConstant()) {
+        output_ << " " << constant->AsLongConstant()->GetValue();
+      }
     } else if (location.IsInvalid()) {
       output_ << "invalid";
     } else if (location.IsStackSlot()) {
diff --git a/compiler/optimizing/nodes.cc b/compiler/optimizing/nodes.cc
index 1a24677..73936e7 100644
--- a/compiler/optimizing/nodes.cc
+++ b/compiler/optimizing/nodes.cc
@@ -534,14 +534,22 @@ bool HCondition::NeedsMaterialization() const {
     return true;
   }
 
-  // TODO: should we allow intervening instructions with no side-effect between this condition
-  // and the If instruction?
+  // TODO: if there is no intervening instructions with side-effect between this condition
+  // and the If instruction, we should move the condition just before the If.
   if (GetNext() != user) {
     return true;
   }
   return false;
 }
 
+bool HCondition::IsBeforeWhenDisregardMoves(HIf* if_) const {
+  HInstruction* previous = if_->GetPrevious();
+  while (previous != nullptr && previous->IsParallelMove()) {
+    previous = previous->GetPrevious();
+  }
+  return previous == this;
+}
+
 bool HInstruction::Equals(HInstruction* other) const {
   if (!InstructionTypeEquals(other)) return false;
   DCHECK_EQ(GetKind(), other->GetKind());
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index af173c8..d3ae7c3 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -1087,8 +1087,15 @@ class HCondition : public HBinaryOperation {
       : HBinaryOperation(Primitive::kPrimBoolean, first, second) {}
 
   virtual bool IsCommutative() { return true; }
+
+  // For register allocation purposes, returns whether this instruction needs to be
+  // materialized (that is, not just be in the processor flags).
   bool NeedsMaterialization() const;
 
+  // For code generation purposes, returns whether this instruction is just before
+  // `if_`, and disregard moves in between.
+  bool IsBeforeWhenDisregardMoves(HIf* if_) const;
+
   DECLARE_INSTRUCTION(Condition);
 
   virtual IfCondition GetCondition() const = 0;