MIPS: Improve compare and branch combining.

MIPS: Improve compare and branch combining.

TEST=
BUG=
R=paul.lind@imgtec.com

Committed: https://code.google.com/p/v8/source/detail?r=25120

[dusmil.imgtec, 2014-11-04 15:07:24]

dusan.milosavljevic@imgtec.com changed reviewers:
+ akos.palfi@imgtec.com, balazs.kilvady@imgtec.com, danno@chromium.org,
jkummerow@chromium.org, paul.lind@imgtec.com

[dusmil.imgtec, 2014-11-04 15:07:47]

PTAL

[paul.l..., 2014-11-04 19:04:27]

LGTM, but please fix the nit.

https://codereview.chromium.org/700873002/diff/1/src/compiler/mips/code-gener...
File src/compiler/mips/code-generator-mips.cc (right):

https://codereview.chromium.org/700873002/diff/1/src/compiler/mips/code-gener...
src/compiler/mips/code-generator-mips.cc:243: // Psuedo-instruction used for
tst/branch.
Suggest adding "No opcode emitted here." to comment, as below.

Please either add back the 'break' or put in a comment: // Fall-through.

I don't think either approach will significantly change the generated code, so
it probably best to use explicit break.

[dusmil.imgtec, 2014-11-04 19:46:11]

https://codereview.chromium.org/700873002/diff/1/src/compiler/mips/code-gener...
File src/compiler/mips/code-generator-mips.cc (right):

https://codereview.chromium.org/700873002/diff/1/src/compiler/mips/code-gener...
src/compiler/mips/code-generator-mips.cc:243: // Psuedo-instruction used for
tst/branch.
On 2014/11/04 19:04:27, paul.l... wrote:
> Suggest adding "No opcode emitted here." to comment, as below.
> 
> Please either add back the 'break' or put in a comment: // Fall-through.
> 
> I don't think either approach will significantly change the generated code, so
> it probably best to use explicit break.

Done.

[dusmil.imgtec, 2014-11-04 19:48:42]

Committed patchset #2 (id:20001) manually as 25120 (presubmit successful).