[Interpreter] Merges ToBoolean and JumpIfTrue/False bytecodes

src/interpreter/bytecode-array-builder.cc

Index: src/interpreter/bytecode-array-builder.cc
diff --git a/src/interpreter/bytecode-array-builder.cc b/src/interpreter/bytecode-array-builder.cc
index 2ce9d51377571c58f027bc3e3f07ff983e4e0eee..03330ea2c7b5885abdd7094531d518feb15a2588 100644
--- a/src/interpreter/bytecode-array-builder.cc
+++ b/src/interpreter/bytecode-array-builder.cc
@@ -450,33 +450,43 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::PopContext(Register context) {
 }
 
 
+bool BytecodeArrayBuilder::IsAccumulatorBoolean() {
+  if (!LastBytecodeInSameBlock()) {
+    // If the previous bytecode was from a different block return false.
+    return false;
+  }
+
+  // If the previous bytecode puts a boolean in
+  // the accumulator return true.

[rmcilroy, 2015/10/30 10:36:00]

nit - put comment on one line (or as much of it as will fit on the line above).

[mythria, 2015/10/30 11:44:47]

Done.

+  switch (Bytecodes::FromByte(bytecodes()->at(last_bytecode_start_))) {
+    case Bytecode::kToBoolean:
+      UNREACHABLE();
+    case Bytecode::kLdaTrue:
+    case Bytecode::kLdaFalse:
+    case Bytecode::kLogicalNot:
+    case Bytecode::kTestEqual:
+    case Bytecode::kTestNotEqual:
+    case Bytecode::kTestEqualStrict:
+    case Bytecode::kTestNotEqualStrict:
+    case Bytecode::kTestLessThan:
+    case Bytecode::kTestLessThanOrEqual:
+    case Bytecode::kTestGreaterThan:
+    case Bytecode::kTestGreaterThanOrEqual:
+    case Bytecode::kTestInstanceOf:
+    case Bytecode::kTestIn:
+      return true;
+    default:
+      return false;
+  }
+}
+
+
 BytecodeArrayBuilder& BytecodeArrayBuilder::CastAccumulatorToBoolean() {
-  if (LastBytecodeInSameBlock()) {
-    // If the previous bytecode puts a boolean in the accumulator
-    // there is no need to emit an instruction.
-    switch (Bytecodes::FromByte(bytecodes()->at(last_bytecode_start_))) {
-      case Bytecode::kToBoolean:
-        UNREACHABLE();
-      case Bytecode::kLdaTrue:
-      case Bytecode::kLdaFalse:
-      case Bytecode::kLogicalNot:
-      case Bytecode::kTestEqual:
-      case Bytecode::kTestNotEqual:
-      case Bytecode::kTestEqualStrict:
-      case Bytecode::kTestNotEqualStrict:
-      case Bytecode::kTestLessThan:
-      case Bytecode::kTestLessThanOrEqual:
-      case Bytecode::kTestGreaterThan:
-      case Bytecode::kTestGreaterThanOrEqual:
-      case Bytecode::kTestInstanceOf:
-      case Bytecode::kTestIn:
-        return *this;
-      default:
-        // Fall through to output kToBoolean.
-        break;
-    }
+  // If the previous bytecode puts a boolean in the accumulator
+  // there is no need to emit an instruction.
+  if (!IsAccumulatorBoolean()) {
+    Output(Bytecode::kToBoolean);
   }
-  Output(Bytecode::kToBoolean);
   return *this;
 }
 
@@ -573,8 +583,29 @@ void BytecodeArrayBuilder::PatchJump(
 }
 
 
+// static
+Bytecode BytecodeArrayBuilder::GetJumpWithToBoolean(Bytecode jump_bytecode) {
+  switch (jump_bytecode) {
+    case Bytecode::kJump:
+      return Bytecode::kJump;
+    case Bytecode::kJumpIfTrue:
+      return Bytecode::kJumpIfToBooleanTrue;
+    case Bytecode::kJumpIfFalse:
+      return Bytecode::kJumpIfToBooleanFalse;
+    default:
+      UNREACHABLE();
+  }

[rmcilroy, 2015/10/30 10:36:00]

You probably need to return return static_cast<Bytecode>(-1); at the bottom here
otherwise gcc (on the bots) will complain. 

[mythria, 2015/10/30 11:44:47]

Done.

+}
+
+
 BytecodeArrayBuilder& BytecodeArrayBuilder::OutputJump(Bytecode jump_bytecode,
                                                        BytecodeLabel* label) {
+  // Check if the value in accumulator is boolean, if not choose an
+  // appropriate JumpIfToBoolean bytecode.
+  if (!IsAccumulatorBoolean()) {
+    jump_bytecode = GetJumpWithToBoolean(jump_bytecode);
+  }
+
   int delta;
   if (label->is_bound()) {
     // Label has been bound already so this is a backwards jump.
@@ -619,18 +650,6 @@ BytecodeArrayBuilder& BytecodeArrayBuilder::JumpIfFalse(BytecodeLabel* label) {
 }
 
 
-BytecodeArrayBuilder& BytecodeArrayBuilder::JumpIfToBooleanTrue(
-    BytecodeLabel* label) {
-  return OutputJump(Bytecode::kJumpIfToBooleanTrue, label);
-}
-
-
-BytecodeArrayBuilder& BytecodeArrayBuilder::JumpIfToBooleanFalse(
-    BytecodeLabel* label) {
-  return OutputJump(Bytecode::kJumpIfToBooleanFalse, label);
-}
-
-
 BytecodeArrayBuilder& BytecodeArrayBuilder::Throw() {
   Output(Bytecode::kThrow);
   exit_seen_in_block_ = true;