[ignition] Add a reverse bytecode iterator

src/interpreter/bytecode-array-reverse-iterator.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-reverse-iterator.h"
+#include "src/objects-inl.h"
+
+namespace v8 {
+namespace internal {
+namespace interpreter {
+
+BytecodeArrayReverseIterator::BytecodeArrayReverseIterator(
+    Handle<BytecodeArray> bytecode_array, Zone* zone)
+    : BytecodeArrayAccessor(bytecode_array, 0), offsets_(zone) {
+  // Run forwards through the bytecode array to determine the offset of each
+  // bytecode.
+  while (current_offset() < bytecode_array->length()) {
+    offsets_.push_back(current_offset());
+    SetOffset(current_offset() + current_bytecode_size());
+  }
+  Reset();
+}
+
+void BytecodeArrayReverseIterator::Advance() {
+  it_offsets_++;
+  UpdateOffsetFromIterator();
+}
+
+void BytecodeArrayReverseIterator::Reset() {
+  it_offsets_ = offsets_.rbegin();
+  UpdateOffsetFromIterator();
+}
+
+bool BytecodeArrayReverseIterator::done() const {
+  return it_offsets_ == offsets_.rend();
+}
+
+void BytecodeArrayReverseIterator::UpdateOffsetFromIterator() {
+  if (it_offsets_ != offsets_.rend()) {
+    SetOffset(*it_offsets_);
+  }
+}
+
+}  // namespace interpreter
+}  // namespace internal
+}  // namespace v8