[Interpreter] Ensure ToBoolean bytecodes are correctly emitted at the start of basic blocks

src/interpreter/bytecode-array-builder.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/interpreter/bytecode-array-builder.h"
 
 namespace v8 {
 namespace internal {
 namespace interpreter {
 
@@ skipping 92 matching lines @@
   Handle<BytecodeArray> output =
       factory->NewBytecodeArray(bytecode_size, &bytecodes_.front(), frame_size,
                                 parameter_count(), constant_pool);
   bytecode_generated_ = true;
   return output;
 }
 
 
 template <size_t N>
 void BytecodeArrayBuilder::Output(Bytecode bytecode, uint32_t(&operands)[N]) {
+  // Don't output dead code.
+  if (exit_seen_in_block_) return;
+
   DCHECK_EQ(Bytecodes::NumberOfOperands(bytecode), static_cast<int>(N));
   last_bytecode_start_ = bytecodes()->size();
   bytecodes()->push_back(Bytecodes::ToByte(bytecode));
   for (int i = 0; i < static_cast<int>(N); i++) {
     DCHECK(OperandIsValid(bytecode, i, operands[i]));
     switch (Bytecodes::GetOperandSize(bytecode, i)) {
       case OperandSize::kNone:
         UNREACHABLE();
       case OperandSize::kByte:
         bytecodes()->push_back(static_cast<uint8_t>(operands[i]));
@@ skipping 24 matching lines @@
 }
 
 
 void BytecodeArrayBuilder::Output(Bytecode bytecode, uint32_t operand0) {
   uint32_t operands[] = {operand0};
   Output(bytecode, operands);
 }
 
 
 void BytecodeArrayBuilder::Output(Bytecode bytecode) {
+  // Don't output dead code.
+  if (exit_seen_in_block_) return;
+
   DCHECK_EQ(Bytecodes::NumberOfOperands(bytecode), 0);
   last_bytecode_start_ = bytecodes()->size();
   bytecodes()->push_back(Bytecodes::ToByte(bytecode));
 }
 
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::BinaryOperation(Token::Value op,
                                                             Register reg,
                                                             Strength strength) {
   if (is_strong(strength)) {
@@ skipping 374 matching lines @@
 }
 
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::Bind(BytecodeLabel* label) {
   if (label->is_forward_target()) {
     // An earlier jump instruction refers to this label. Update it's location.
     PatchJump(bytecodes()->end(), bytecodes()->begin() + label->offset());
     // Now treat as if the label will only be back referred to.
   }
   label->bind_to(bytecodes()->size());
+  LeaveBasicBlock();
   return *this;
 }
 
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::Bind(const BytecodeLabel& target,
                                                  BytecodeLabel* label) {
-  DCHECK_EQ(label->is_bound(), false);
-  DCHECK_EQ(target.is_bound(), true);
+  DCHECK(!label->is_bound());
+  DCHECK(target.is_bound());
   PatchJump(bytecodes()->begin() + target.offset(),
             bytecodes()->begin() + label->offset());
   label->bind_to(target.offset());
+  LeaveBasicBlock();
   return *this;
 }
 
 
 // static
 Bytecode BytecodeArrayBuilder::GetJumpWithConstantOperand(
     Bytecode jump_bytecode) {
   switch (jump_bytecode) {
     case Bytecode::kJump:
       return Bytecode::kJumpConstant;
@@ skipping 64 matching lines @@
       return Bytecode::kJumpIfToBooleanFalse;
     default:
       UNREACHABLE();
   }
   return static_cast<Bytecode>(-1);
 }
 
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::OutputJump(Bytecode jump_bytecode,
                                                        BytecodeLabel* label) {
+  // Don't emit dead code.
+  if (exit_seen_in_block_) return *this;
+
   // Check if the value in accumulator is boolean, if not choose an
   // appropriate JumpIfToBoolean bytecode.
   if (NeedToBooleanCast()) {
     jump_bytecode = GetJumpWithToBoolean(jump_bytecode);
   }
 
   int delta;
   if (label->is_bound()) {
     // Label has been bound already so this is a backwards jump.
     CHECK_GE(bytecodes()->size(), label->offset());
@@ skipping 11 matching lines @@
     Output(jump_bytecode, static_cast<uint8_t>(delta));
   } else {
     size_t entry = GetConstantPoolEntry(handle(Smi::FromInt(delta), isolate()));
     if (FitsInIdx8Operand(entry)) {
       Output(GetJumpWithConstantOperand(jump_bytecode),
              static_cast<uint8_t>(entry));
     } else {
       UNIMPLEMENTED();
     }
   }
+  LeaveBasicBlock();
   return *this;
 }
 
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::Jump(BytecodeLabel* label) {
   return OutputJump(Bytecode::kJump, label);
 }
 
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::JumpIfTrue(BytecodeLabel* label) {
@@ skipping 43 matching lines @@
   return *this;
 }
 
 
 BytecodeArrayBuilder& BytecodeArrayBuilder::ForInDone(Register for_in_state) {
   Output(Bytecode::kForInDone, for_in_state.ToOperand());
   return *this;
 }
 
 
-BytecodeArrayBuilder& BytecodeArrayBuilder::EnterBlock() { return *this; }
-
-
-BytecodeArrayBuilder& BytecodeArrayBuilder::LeaveBlock() {
+void BytecodeArrayBuilder::LeaveBasicBlock() {
   last_block_end_ = bytecodes()->size();
   exit_seen_in_block_ = false;
-  return *this;
 }
 
 
 void BytecodeArrayBuilder::EnsureReturn() {
   if (!exit_seen_in_block_) {
     LoadUndefined();
     Return();
   }
 }
 
@@ skipping 482 matching lines @@
   DCHECK_GT(next_consecutive_count_, 0);
   builder_->BorrowConsecutiveTemporaryRegister(next_consecutive_register_);
   allocated_.push_back(next_consecutive_register_);
   next_consecutive_count_--;
   return Register(next_consecutive_register_++);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8