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

runtime/vm/intermediate_language_mips.cc

Index: runtime/vm/intermediate_language_mips.cc
diff --git a/runtime/vm/intermediate_language_mips.cc b/runtime/vm/intermediate_language_mips.cc
index 07959dead945cdd3d628852d344bb0cb03a0f482..e513f5ed3f22e3d5ac63481219c66b9825492c87 100644
--- a/runtime/vm/intermediate_language_mips.cc
+++ b/runtime/vm/intermediate_language_mips.cc
@@ -178,8 +178,11 @@ void IfThenElseInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   __ LoadImmediate(result, Smi::RawValue(true_value));
 
   // 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};  // Emit branch-free code.
   Condition true_condition = comparison()->EmitComparisonCode(compiler, labels);
+  ASSERT(true_condition.IsValid());
   if (swapped) {
     true_condition = NegateCondition(true_condition);
   }
@@ -781,16 +784,15 @@ Condition EqualityCompareInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
 }
 
 
-void EqualityCompareInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  ASSERT((kind() == Token::kNE) || (kind() == Token::kEQ));
-  __ Comment("EqualityCompareInstr");
-
+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.IsValid()) {
+    EmitBranchOnCondition(compiler, true_condition, labels);
+  }
 
-  Register result = locs()->out(0).reg();
+  Register result = this->locs()->out(0).reg();
   Label done;
   __ Bind(&is_false);
   __ LoadObject(result, Bool::False());
@@ -801,14 +803,13 @@ void EqualityCompareInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
 }
 
 
-void EqualityCompareInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                          BranchInstr* branch) {
-  __ Comment("EqualityCompareInstr::EmitBranchCode");
-  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.IsValid()) {
+    EmitBranchOnCondition(compiler, true_condition, labels);
+  }
 }
 
 
@@ -840,20 +841,6 @@ 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;
@@ -906,29 +893,9 @@ Condition TestCidsInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
   } else {
     __ b(deopt);
   }
-  // Dummy result as the last instruction is a jump or fall through.
-  return Condition(CMPRES1, ZR, AL);
-}
-
-
-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());
-  __ b(&done);
-  __ 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 Condition(ZR, ZR, INVALID_RELATION);
 }
 
 
@@ -982,35 +949,6 @@ Condition RelationalOpInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
 }
 
 
-void RelationalOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  __ Comment("RelationalOpInstr");
-
-  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());
-  __ b(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result, Bool::True());
-  __ Bind(&done);
-}
-
-
-void RelationalOpInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                       BranchInstr* branch) {
-  __ Comment("RelationalOpInstr");
-
-  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);
@@ -3247,6 +3185,7 @@ void CheckedSmiComparisonInstr::EmitBranchCode(FlowGraphCompiler* compiler,
   compiler->AddSlowPathCode(slow_path);
   EMIT_SMI_CHECK;
   Condition true_condition = EmitComparisonCode(compiler, labels);
+  ASSERT(true_condition.IsValid());
   EmitBranchOnCondition(compiler, true_condition, labels);
   __ Bind(slow_path->exit_label());
 }
@@ -3261,6 +3200,7 @@ void CheckedSmiComparisonInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   compiler->AddSlowPathCode(slow_path);
   EMIT_SMI_CHECK;
   Condition true_condition = EmitComparisonCode(compiler, labels);
+  ASSERT(true_condition.IsValid());
   EmitBranchOnCondition(compiler, true_condition, labels);
   Register result = locs()->out(0).reg();
   __ Bind(&false_label);
@@ -3975,7 +3915,7 @@ Condition DoubleTestOpInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
       }
       __ b(labels.true_label);
     }
-    return Condition();  // Unused.
+    return Condition(ZR, ZR, INVALID_RELATION);  // Unused.
   } else {
     ASSERT(op_kind() == MethodRecognizer::kDouble_getIsInfinite);
     __ mfc1(CMPRES1, EvenFRegisterOf(value));
@@ -3990,38 +3930,6 @@ 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);
-  // Branches for isNaN are emitted in EmitComparisonCode already.
-  if (op_kind() == MethodRecognizer::kDouble_getIsInfinite) {
-    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);
-  // Branches for isNaN are emitted in EmitComparisonCode already.
-  if (op_kind() == MethodRecognizer::kDouble_getIsInfinite) {
-    EmitBranchOnCondition(compiler, true_condition, labels);
-  }
-  const Register result = locs()->out(0).reg();
-  Label done;
-  __ Comment("return bool");
-  __ Bind(&is_false);
-  __ LoadObject(result, Bool::False());
-  __ b(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result, Bool::True());
-  __ Bind(&done);
-}
-
-
 LocationSummary* BinaryFloat32x4OpInstr::MakeLocationSummary(Zone* zone,
                                                              bool opt) const {
   UNIMPLEMENTED();
@@ -5986,37 +5894,6 @@ Condition StrictCompareInstr::EmitComparisonCode(FlowGraphCompiler* compiler,
 }
 
 
-void StrictCompareInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  __ Comment("StrictCompareInstr");
-  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());
-  __ b(&done);
-  __ Bind(&is_true);
-  __ LoadObject(result, Bool::True());
-  __ Bind(&done);
-}
-
-
-void StrictCompareInstr::EmitBranchCode(FlowGraphCompiler* compiler,
-                                        BranchInstr* branch) {
-  __ Comment("StrictCompareInstr::EmitBranchCode");
-  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* BooleanNegateInstr::MakeLocationSummary(Zone* zone,
                                                          bool opt) const {
   return LocationSummary::Make(zone, 1, Location::RequiresRegister(),