[interpreter] Streamline bytecode array writing.

src/interpreter/bytecode-array-writer.h

 // 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.
 
 #ifndef V8_INTERPRETER_BYTECODE_ARRAY_WRITER_H_
 #define V8_INTERPRETER_BYTECODE_ARRAY_WRITER_H_
 
 #include "src/interpreter/bytecode-pipeline.h"
 #include "src/interpreter/source-position-table.h"
 
@@ skipping 16 matching lines @@
   // BytecodePipelineStage interface.
   void Write(BytecodeNode* node) override;
   void WriteJump(BytecodeNode* node, BytecodeLabel* label) override;
   void BindLabel(BytecodeLabel* label) override;
   void BindLabel(const BytecodeLabel& target, BytecodeLabel* label) override;
   Handle<BytecodeArray> ToBytecodeArray(
       int fixed_register_count, int parameter_count,
       Handle<FixedArray> handler_table) override;
 
  private:
+  // Maximum sized packed bytecode is comprised of a prefix bytecode,
+  // plus the actual bytecode, plus the maximum number of operands times
+  // the maximum operand size.
+  static const size_t kMaxSizeOfPackedBytecode =
+      2 * sizeof(Bytecode) +
+      Bytecodes::kMaxOperands * sizeof(static_cast<size_t>(OperandSize::kLast));

[rmcilroy, 2016/06/28 09:07:26]

I don't think you want the sizeof here any longer, OperandSize::kLast gives you
the size directly

+
   // Constants that act as placeholders for jump operands to be
   // patched. These have operand sizes that match the sizes of
   // reserved constant pool entries.
   const uint32_t k8BitJumpPlaceholder = 0x7f;
   const uint32_t k16BitJumpPlaceholder =
       k8BitJumpPlaceholder | (k8BitJumpPlaceholder << 8);
   const uint32_t k32BitJumpPlaceholder =
       k16BitJumpPlaceholder | (k16BitJumpPlaceholder << 16);
 
   void PatchJump(size_t jump_target, size_t jump_location);
@@ skipping 24 matching lines @@
 
   friend class BytecodeArrayWriterUnittest;
   DISALLOW_COPY_AND_ASSIGN(BytecodeArrayWriter);
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_ARRAY_WRITER_H_