A64: Use the result of compare IC in StringCompareAndBranch.

A64: Use the result of compare IC in StringCompareAndBranch.

TEST=mjsunit/third_party/string-trim
R=jacob.bramley@arm.com

Committed: https://code.google.com/p/v8/source/detail?r=19101

[ulan, 2014-02-05 12:58:16]

PTAL

[jbramley, 2014-02-05 13:01:41]

https://codereview.chromium.org/149083004/diff/1/src/a64/lithium-codegen-a64.cc
File src/a64/lithium-codegen-a64.cc (right):

https://codereview.chromium.org/149083004/diff/1/src/a64/lithium-codegen-a64....
src/a64/lithium-codegen-a64.cc:5111: __ Tst(x0, x0);
ARM (and AArch64) processors generally prefer "Cmp(x0, 0)". (I assume that the
condition can be either EQ or NE here.)

However, in this case, you're probably better off using EmitCompareAndBranch
because that will use Cbz or Cbnz if possible.

[ulan, 2014-02-05 13:09:21]

Thanks, I uploaded new patch set.

https://codereview.chromium.org/149083004/diff/1/src/a64/lithium-codegen-a64.cc
File src/a64/lithium-codegen-a64.cc (right):

https://codereview.chromium.org/149083004/diff/1/src/a64/lithium-codegen-a64....
src/a64/lithium-codegen-a64.cc:5111: __ Tst(x0, x0);
On 2014/02/05 13:01:41, jbramley wrote:
> ARM (and AArch64) processors generally prefer "Cmp(x0, 0)". (I assume that the
> condition can be either EQ or NE here.)
> 
> However, in this case, you're probably better off using EmitCompareAndBranch
> because that will use Cbz or Cbnz if possible.

Done.

[jbramley, 2014-02-05 13:11:12]

lgtm

[ulan, 2014-02-05 13:15:22]

Committed patchset #2 manually as r19101 (presubmit successful).