Make some constants' meaning clear for X64

Make some constants' meaning clear for X64

R=danno@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16061

[haitao.feng, 2013-08-02 04:41:17]

Addressed danno's comments on https://codereview.chromium.org/18014003/.

https://codereview.chromium.org/21721002/diff/1/src/x64/assembler-x64.h
File src/x64/assembler-x64.h (right):

https://codereview.chromium.org/21721002/diff/1/src/x64/assembler-x64.h#newco...
src/x64/assembler-x64.h:598: static const int kDebugBreakSlotLength =
kCallSequenceLength;
It seems that we could use short call and RUNTIME_ENTRY to patch the JS return
and debug break slot as the patched site and target are all in the code range
for X64.  I leave it to another CL.

[danno, 2013-08-02 14:01:20]

https://codereview.chromium.org/21721002/diff/1/src/x64/assembler-x64.h
File src/x64/assembler-x64.h (right):

https://codereview.chromium.org/21721002/diff/1/src/x64/assembler-x64.h#newco...
src/x64/assembler-x64.h:582: // The length of call(kScratchRegister).
I am not sure that it is help to include "Scratch" in the name here an below.
Perhaps a little more generic is better, e.g.

kCallRegisterShortInstructionSize = 3;
kCallImmediateShortInstructionSize = 5;
kMoveAddressIntoRegisterShortInstructionSize

etc...

https://codereview.chromium.org/21721002/diff/1/src/x64/assembler-x64.h#newco...
src/x64/assembler-x64.h:585: static const int kShortCallInstructionLength = 5;
Unify to either "...Length" or "...Size". I think "Length" is better.

[haitao.feng, 2013-08-02 15:10:56]

danno, thanks a lot for the review. All comments are addressed. Please take
another look.

https://codereview.chromium.org/21721002/diff/1/src/x64/assembler-x64.h
File src/x64/assembler-x64.h (right):

https://codereview.chromium.org/21721002/diff/1/src/x64/assembler-x64.h#newco...
src/x64/assembler-x64.h:582: // The length of call(kScratchRegister).
If the register number is less than 8, then the call instruction size is 2. For
move instruction, it is true for 64-bit system for REX.W, but for x32, if the
register number is less than 8, we do not need the REX prefix.

kShortCallInstruction is better as it is short indeed. It only could access
[-2G, 2G] relative to the current pc address.

https://codereview.chromium.org/21721002/diff/1/src/x64/assembler-x64.h#newco...
src/x64/assembler-x64.h:585: static const int kShortCallInstructionLength = 5;
On 2013/08/02 14:01:20, danno wrote:
> Unify to either "...Length" or "...Size". I think "Length" is better.

Done.

[danno, 2013-08-05 15:36:38]

lgtm

[haitao.feng, 2013-08-06 00:09:20]

Committed patchset #2 manually as r16061 (presubmit successful).