Contribution of PowerPC port.

src/frames.h

 // Copyright 2012 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_FRAMES_H_
 #define V8_FRAMES_H_
 
 #include "src/allocation.h"
 #include "src/handles.h"
 #include "src/safepoint-table.h"
@@ skipping 53 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(InnerPointerToCodeCache);
 };
 
 
 class StackHandlerConstants : public AllStatic {
  public:
   static const int kNextOffset     = 0 * kPointerSize;
   static const int kCodeOffset     = 1 * kPointerSize;
   static const int kStateOffset    = 2 * kPointerSize;
+#if V8_TARGET_LITTLE_ENDIAN || !V8_HOST_ARCH_64_BIT
+  static const int kStateIntOffset = kStateOffset;

[danno, 2014/07/29 13:24:08]

If kStateOffset isn't used for anything else but kStateIntOffset, then simply
remove it.

Perhaps it makes sense to put a constant kLowWordOfIntOffset in v8.h or
somewhere common that is keyed off of V8_TARGET_LITTLE_ENDIAN ||
!V8_HOST_ARCH_64_BIT, and then this can simply be

static const int kStateOffset = 2 * kPointerSize + kLowWordOfIntOffset;

[andrew_low, 2014/07/30 13:27:05]

Both kStateOffset and kStateIntOffset are used is a handful of places. I agree
with your comment about kLowWordOfIntOffset - but would like more guidance
before I start down that path.

$ grep kStateOffset *
frames.cc:  Memory::uintptr_at(address() + StackHandlerConstants::kStateOffset)
= state;
frames.h:  static const int kStateOffset    = 2 * kPointerSize;
frames.h:  static const int kStateIntOffset = kStateOffset;
frames.h:  static const int kStateIntOffset = kStateOffset + kIntSize;

$ grep kStateIntOffset *
frames.h:  static const int kStateIntOffset = kStateOffset;
frames.h:  static const int kStateIntOffset = kStateOffset + kIntSize;
frames-inl.h:  const int offset = StackHandlerConstants::kStateIntOffset;
frames-inl.h:  const int offset = StackHandlerConstants::kStateIntOffset;

+#else
+  static const int kStateIntOffset = kStateOffset + kIntSize;
+#endif
   static const int kContextOffset  = 3 * kPointerSize;
   static const int kFPOffset       = 4 * kPointerSize;
 
   static const int kSize = kFPOffset + kFPOnStackSize;
   static const int kSlotCount = kSize >> kPointerSizeLog2;
 };
 
 
 class StackHandler BASE_EMBEDDED {
  public:
@@ skipping 848 matching lines @@
 };
 
 
 // Reads all frames on the current stack and copies them into the current
 // zone memory.
 Vector<StackFrame*> CreateStackMap(Isolate* isolate, Zone* zone);
 
 } }  // namespace v8::internal
 
 #endif  // V8_FRAMES_H_