[TurboFan][TurboProp] Optimize bytecode iterator.

Optimize BytecodeArrayRandomIterator to reserve roughly the right
size index array based on bytecode array length. Also save the
bytecode length in BytecodeArrayAccessor to avoid a more expensive
heap read accessor on BytecodeArray.

BUG=v8:9684

Change-Id: I7f85439877dbfc5ccf5aacc9d4006bd285f1c891
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2593330
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Auto-Submit: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71772}

src/interpreter/bytecode-array-accessor.cc

@@ -57,6 +57,7 @@ class OnHeapBytecodeArray final : public AbstractBytecodeArray {
 BytecodeArrayAccessor::BytecodeArrayAccessor(
     std::unique_ptr<AbstractBytecodeArray> bytecode_array, int initial_offset)
     : bytecode_array_(std::move(bytecode_array)),
+      bytecode_length_(bytecode_array_->length()),
       bytecode_offset_(initial_offset),
       operand_scale_(OperandScale::kSingle),
       prefix_offset_(0) {
@@ -103,7 +104,7 @@ void BytecodeArrayAccessor::UpdateOperandScale() {
 }
 
 bool BytecodeArrayAccessor::OffsetInBounds() const {
-  return bytecode_offset_ >= 0 && bytecode_offset_ < bytecode_array()->length();
+  return bytecode_offset_ >= 0 && bytecode_offset_ < bytecode_length_;
 }
 
 Bytecode BytecodeArrayAccessor::current_bytecode() const {

src/interpreter/bytecode-array-accessor.h

@@ -147,6 +147,8 @@ class V8_EXPORT_PRIVATE BytecodeArrayAccessor {
 
   std::ostream& PrintTo(std::ostream& os) const;
 
+  int bytecode_length() const { return bytecode_length_; }
+
  private:
   bool OffsetInBounds() const;
 
@@ -157,6 +159,7 @@ class V8_EXPORT_PRIVATE BytecodeArrayAccessor {
   void UpdateOperandScale();
 
   std::unique_ptr<AbstractBytecodeArray> bytecode_array_;
+  const int bytecode_length_;
   int bytecode_offset_;
   OperandScale operand_scale_;
   int prefix_offset_;

src/interpreter/bytecode-array-iterator.cc

@@ -23,7 +23,7 @@ void BytecodeArrayIterator::Advance() {
 }
 
 bool BytecodeArrayIterator::done() const {
-  return current_offset() >= bytecode_array()->length();
+  return current_offset() >= bytecode_length();
 }
 
 }  // namespace interpreter

src/interpreter/bytecode-array-random-iterator.cc

@@ -13,6 +13,7 @@ namespace interpreter {
 BytecodeArrayRandomIterator::BytecodeArrayRandomIterator(
     Handle<BytecodeArray> bytecode_array, Zone* zone)
     : BytecodeArrayAccessor(bytecode_array, 0), offsets_(zone) {
+  offsets_.reserve(bytecode_array->length() / 2);
   Initialize();
 }