ARM64: Avoid iterating through all unresolved branch infos when many are pending.

ARM64: Avoid iterating through all unresolved branch infos when many are pending.

Instead, inspect the label chain and delete pending information for every branch
in the chain.

R=ulan@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=20715

[Alexandre Rames, 2014-04-07 12:54:15]

This patch diminishes the regression observed at
https://codereview.chromium.org/209333004 .

With this patch applied, the timings for
make -j32 arm64.release.check TESTFLAGS=--time
TESTJOBS=mozilla/js1_5/Regress/regress-280769-2
become:

Without the regexp veneer patch:
   1 (00:06.818) mozilla/js1_5/Regress/regress-280769-2
   2 (00:01.910) mozilla/js1_5/Regress/regress-280769-2
   3 (00:01.711) mozilla/js1_5/Regress/regress-280769-2

With the regexp veneer patch:
   1 (00:11.922) mozilla/js1_5/Regress/regress-280769-2
   2 (00:04.014) mozilla/js1_5/Regress/regress-280769-2
   3 (00:04.014) mozilla/js1_5/Regress/regress-280769-2

[ulan, 2014-04-07 13:24:40]

https://codereview.chromium.org/227043010/diff/1/src/arm64/assembler-arm64.cc
File src/arm64/assembler-arm64.cc (right):

https://codereview.chromium.org/227043010/diff/1/src/arm64/assembler-arm64.cc...
src/arm64/assembler-arm64.cc:612:
DeleteUnresolvedBranchInfoForLabelTraverse(label);
Ignoring ADR instructions, chain length <= unresolved_branches_.size(), right?
Then why not always use this function?

[Alexandre Rames, 2014-04-09 13:22:06]

https://codereview.chromium.org/227043010/diff/1/src/arm64/assembler-arm64.cc
File src/arm64/assembler-arm64.cc (right):

https://codereview.chromium.org/227043010/diff/1/src/arm64/assembler-arm64.cc...
src/arm64/assembler-arm64.cc:612:
DeleteUnresolvedBranchInfoForLabelTraverse(label);
On 2014/04/07 13:24:41, ulan wrote:
> Ignoring ADR instructions, chain length <= unresolved_branches_.size(), right?

Yes.

> Then why not always use this function?

I initially kept it as I was worried that digging through the chain could be
more expensive than a simple iteration. Removed the iterative function to always
traverse the label chain.

[ulan, 2014-04-09 13:33:13]

lgtm

[Alexandre Rames, 2014-04-14 11:08:22]

Committed patchset #2 manually as r20715 (presubmit successful).