VM-codegen: Clean up the way we emit code for comparison instructions.

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
diff --git a/runtime/vm/intermediate_language_x64.cc b/runtime/vm/intermediate_language_x64.cc
index e9c8f208bd53f20c50df4774d02553c538e7f99b..b947742092ea4131014fc362e4f07c3fb82019ec 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -165,8 +165,11 @@ void IfThenElseInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ xorq(RDX, RDX);
 
   // Emit comparison code. This must not overwrite the result register.
+  // IfThenElseInstr::Supports() should prevent EmitComparisonCode from using
+  // the labels or returning an invalid condition.
   BranchLabels labels = {NULL, NULL, NULL};
   Condition true_condition = comparison()->EmitComparisonCode(compiler, labels);
+  ASSERT(true_condition != INVALID_CONDITION);
 
   const bool is_power_of_two_kind = IsPowerOfTwoKind(if_true_, if_false_);
 
@@ -573,13 +576,13 @@ Condition EqualityCompareInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
 }
 
 
-void EqualityCompareInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  ASSERT((kind() == Token::kEQ) || (kind() == Token::kNE));
-
+void ComparisonInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   Label is_true, is_false;
   BranchLabels labels = {&is_true, &is_false, &is_false};
   Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
+  if (true_condition != INVALID_CONDITION) {
+    EmitBranchOnCondition(compiler, true_condition, labels);
+  }
 
   Register result = locs()->out(0).reg();
   Label done;
@@ -592,13 +595,13 @@ void EqualityCompareInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 }
 
 
-void EqualityCompareInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                          BranchInstr* branch) {
-  ASSERT((kind() == Token::kNE) || (kind() == Token::kEQ));
-
+void ComparisonInstr::EmitBranchCode(FlowGraphCompiler* compiler,
+                                     BranchInstr* branch) {
   BranchLabels labels = compiler->CreateBranchLabels(branch);
   Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
+  if (true_condition != INVALID_CONDITION) {
+    EmitBranchOnCondition(compiler, true_condition, labels);
+  }
 }
 
 
@@ -631,20 +634,6 @@ Condition TestSmiInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
 }
 
 
-void TestSmiInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  // Never emitted outside of the BranchInstr.
-  UNREACHABLE();
-}
-
-
-void TestSmiInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                  BranchInstr* branch) {
-  BranchLabels labels = compiler->CreateBranchLabels(branch);
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
-}
-
-
 LocationSummary* TestCidsInstr::MakeLocationSummary(Zone* zone,
                                                     bool opt) const {
   const intptr_t kNumInputs = 1;
@@ -696,30 +685,9 @@ Condition TestCidsInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
   } else {
     __ jmp(deopt);
   }
-  // Dummy result as the last instruction is a jump, any conditional
-  // branch using the result will therefore be skipped.
-  return ZERO;
-}
-
-
-void TestCidsInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                   BranchInstr* branch) {
-  BranchLabels labels = compiler->CreateBranchLabels(branch);
-  EmitComparisonCode(compiler, labels);
-}
-
-
-void TestCidsInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  Register result_reg = locs()->out(0).reg();
-  Label is_true, is_false, done;
-  BranchLabels labels = {&is_true, &is_false, &is_false};
-  EmitComparisonCode(compiler, labels);
-  __ Bind(&is_false);
-  __ LoadObject(result_reg, Bool::False());
-  __ jmp(&done, Assembler::kNearJump);
-  __ Bind(&is_true);
-  __ LoadObject(result_reg, Bool::True());
-  __ Bind(&done);
+  // Dummy result as this method already did the jump, there's no need
+  // for the caller to branch on a condition.
+  return INVALID_CONDITION;
 }
 
 
@@ -767,31 +735,6 @@ Condition RelationalOpInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
 }
 
 
-void RelationalOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  Label is_true, is_false;
-  BranchLabels labels = {&is_true, &is_false, &is_false};
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
-
-  Register result = locs()->out(0).reg();
-  Label done;
-  __ Bind(&is_false);
-  __ LoadObject(result, Bool::False());
-  __ jmp(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result, Bool::True());
-  __ Bind(&done);
-}
-
-
-void RelationalOpInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                       BranchInstr* branch) {
-  BranchLabels labels = compiler->CreateBranchLabels(branch);
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
-}
-
-
 LocationSummary* NativeCallInstr::MakeLocationSummary(Zone* zone,
                                                       bool opt) const {
   return MakeCallSummary(zone);
@@ -3109,6 +3052,7 @@ void CheckedSmiComparisonInstr::EmitBranchCode(FlowGraphCompiler* compiler,
   compiler->AddSlowPathCode(slow_path);
   EMIT_SMI_CHECK;
   Condition true_condition = EmitComparisonCode(compiler, labels);
+  ASSERT(true_condition != INVALID_CONDITION);
   EmitBranchOnCondition(compiler, true_condition, labels);
   __ Bind(slow_path->exit_label());
 }
@@ -3123,6 +3067,7 @@ void CheckedSmiComparisonInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   compiler->AddSlowPathCode(slow_path);
   EMIT_SMI_CHECK;
   Condition true_condition = EmitComparisonCode(compiler, labels);
+  ASSERT(true_condition != INVALID_CONDITION);
   EmitBranchOnCondition(compiler, true_condition, labels);
   Register result = locs()->out(0).reg();
   __ Bind(&false_label);
@@ -3951,32 +3896,6 @@ Condition DoubleTestOpInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
 }
 
 
-void DoubleTestOpInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                       BranchInstr* branch) {
-  ASSERT(compiler->is_optimizing());
-  BranchLabels labels = compiler->CreateBranchLabels(branch);
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
-}
-
-
-void DoubleTestOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  Label is_true, is_false;
-  BranchLabels labels = {&is_true, &is_false, &is_false};
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
-
-  Register result = locs()->out(0).reg();
-  Label done;
-  __ Bind(&is_false);
-  __ LoadObject(result, Bool::False());
-  __ jmp(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result, Bool::True());
-  __ Bind(&done);
-}
-
-
 LocationSummary* BinaryFloat32x4OpInstr::MakeLocationSummary(Zone* zone,
                                                              bool opt) const {
   const intptr_t kNumInputs = 2;
@@ -6638,36 +6557,6 @@ Condition StrictCompareInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
 }
 
 
-void StrictCompareInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  ASSERT(kind() == Token::kEQ_STRICT || kind() == Token::kNE_STRICT);
-
-  Label is_true, is_false;
-  BranchLabels labels = {&is_true, &is_false, &is_false};
-
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
-
-  Register result = locs()->out(0).reg();
-  Label done;
-  __ Bind(&is_false);
-  __ LoadObject(result, Bool::False());
-  __ jmp(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result, Bool::True());
-  __ Bind(&done);
-}
-
-
-void StrictCompareInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                        BranchInstr* branch) {
-  ASSERT(kind() == Token::kEQ_STRICT || kind() == Token::kNE_STRICT);
-
-  BranchLabels labels = compiler->CreateBranchLabels(branch);
-  Condition true_condition = EmitComparisonCode(compiler, labels);
-  EmitBranchOnCondition(compiler, true_condition, labels);
-}
-
-
 LocationSummary* ClosureCallInstr::MakeLocationSummary(Zone* zone,
                                                        bool opt) const {
   const intptr_t kNumInputs = 1;