[Turbofan] Allow compiler to elide complex aliasing code.

[Turbofan] Allow compiler to elide complex aliasing code.
- Add a const bool kSimpleFPAliasing variable for each platform so it's
easier for the compiler to eliminate dead code.
- Modify RegisterAllocator to use it.

LOG=N
BUG=v8:4124
Committed: https://crrev.com/5107f1c135afb081ab58e275cde48fe207e7db11
Cr-Commit-Position: refs/heads/master@{#37288}

[bbudge, 2016-06-26 23:08:32]

https://codereview.chromium.org/2101473002/diff/1/src/compiler/register-alloc...
File src/compiler/register-allocator.cc (right):

https://codereview.chromium.org/2101473002/diff/1/src/compiler/register-alloc...
src/compiler/register-allocator.cc:1559: assigned_double_registers_->Add(index);
Fixes a bug.

[bbudge, 2016-06-27 00:10:20]

bbudge@chromium.org changed reviewers:
+ bmeurer@chromium.org

[bbudge, 2016-06-27 00:10:20]

I think this change will help keep performance at par for non-ARM targets,
especially as I add SIMD 128 registers. I'll probably also change
canonicalization to conflate all FP types on non-ARM.

[Benedikt Meurer, 2016-06-27 03:53:37]

Makes sense, thx. LGTM.

[bbudge, 2016-06-27 11:29:28]

The CQ bit was checked by bbudge@chromium.org

[bbudge, 2016-06-27 11:29:28]

The patchset sent to the CQ was uploaded after l-g-t-m from bmeurer@chromium.org
Link to the patchset: https://codereview.chromium.org/2101473002/#ps40001
(title: "Rebase.")

[commit-bot: I haz the power, 2016-06-27 11:29:37]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-06-27 11:56:59]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-06-27 11:58:01]

Description was changed from

==========
[Turbofan] Allow compiler to elide complex aliasing code.
- Add a const bool kSimpleFPAliasing variable for each platform so it's
easier for the compiler to eliminate dead code.
- Modify RegisterAllocator to use it.

LOG=N
BUG=v8:4124
==========

to

==========
[Turbofan] Allow compiler to elide complex aliasing code.
- Add a const bool kSimpleFPAliasing variable for each platform so it's
easier for the compiler to eliminate dead code.
- Modify RegisterAllocator to use it.

LOG=N
BUG=v8:4124

Committed: https://crrev.com/5107f1c135afb081ab58e275cde48fe207e7db11
Cr-Commit-Position: refs/heads/master@{#37288}
==========

[commit-bot: I haz the power, 2016-06-27 11:58:02]

Patchset 3 (id:??) landed as
https://crrev.com/5107f1c135afb081ab58e275cde48fe207e7db11
Cr-Commit-Position: refs/heads/master@{#37288}