MIPS: [turbofan] Optimize certain chains of Branch into a Switch.

MIPS: [turbofan] Optimize certain chains of Branch into a Switch.

Port acd9c46ca7a0ada723d717f2545fd484c824eaa2

Original commit message:
This adds a new ControlFlowOptimizer that - for now - recognizes chains
of Branches generated by the SwitchBuilder for a subset of javascript
switches into Switch nodes. Those Switch nodes are then lowered to
either table or lookup switches.

Also rename Case to IfValue (and introduce IfDefault) for consistency.

BUG=v8:3872
LOG=n

Committed: https://crrev.com/97a4a21a6acfd77bbdf2b027bfa5c459b54acbdd
Cr-Commit-Position: refs/heads/master@{#26707}

[balazs.kilvady, 2015-02-17 18:53:39]

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

[paul.l..., 2015-02-17 19:33:59]

There are some issues that need to be fixed, but I am giving this an LGTM to
un-break the build. (It does pass tests in its current state)

Please submit a follow-up CL tomorrow to address these issues.

https://codereview.chromium.org/931263002/diff/1/src/compiler/mips/code-gener...
File src/compiler/mips/code-generator-mips.cc (right):

https://codereview.chromium.org/931263002/diff/1/src/compiler/mips/code-gener...
src/compiler/mips/code-generator-mips.cc:905: __ bal(&here);
We need a BlockTrampolinePoolFor() call before this bal() to cover the table
size, and the instructions to index the table.

https://codereview.chromium.org/931263002/diff/1/src/compiler/mips/instructio...
File src/compiler/mips/instruction-selector-mips.cc (right):

https://codereview.chromium.org/931263002/diff/1/src/compiler/mips/instructio...
src/compiler/mips/instruction-selector-mips.cc:764: size_t table_space_cost = 4
+ value_range;
The cost numbers here are incorrect for MIPS, since we use more instructions for
the jump table implementation. Please update these.

https://codereview.chromium.org/931263002/diff/1/src/compiler/mips64/code-gen...
File src/compiler/mips64/code-generator-mips64.cc (right):

https://codereview.chromium.org/931263002/diff/1/src/compiler/mips64/code-gen...
src/compiler/mips64/code-generator-mips64.cc:1061: // Ensure that dd-ed labels
goes to 8 byte aligned addresses.
nit: "goes to ... " should probably be "use 8 byte aligned locations"

https://codereview.chromium.org/931263002/diff/1/src/compiler/mips64/code-gen...
src/compiler/mips64/code-generator-mips64.cc:1065: __ bal(&here);
Add BlockTrampolinePoolFor() to cover table and indexing into it.

https://codereview.chromium.org/931263002/diff/1/src/compiler/mips64/instruct...
File src/compiler/mips64/instruction-selector-mips64.cc (right):

https://codereview.chromium.org/931263002/diff/1/src/compiler/mips64/instruct...
src/compiler/mips64/instruction-selector-mips64.cc:986: size_t table_time_cost =
3;
as in mips32 port, the costs must be calculated correctly based on our actual
instruction counts.

[balazs.kilvady, 2015-02-17 20:04:45]

The CQ bit was checked by balazs.kilvady@imgtec.com

[commit-bot: I haz the power, 2015-02-17 20:05:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/931263002/1

[commit-bot: I haz the power, 2015-02-17 20:44:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-17 20:44:23]

Patchset 1 (id:??) landed as
https://crrev.com/97a4a21a6acfd77bbdf2b027bfa5c459b54acbdd
Cr-Commit-Position: refs/heads/master@{#26707}