[turbofan] Add backend support for float32 operations.

[turbofan] Add backend support for float32 operations.

This adds the basics necessary to support float32 operations in TurboFan.
The actual functionality required to detect safe float32 operations will
be added based on this later. Therefore this does not affect production
code except for some cleanup/refactoring.

In detail, this patchset contains the following features:
- Add support for float32 operations to arm, arm64, ia32 and x64
  backends.
- Add float32 machine operators.
- Add support for float32 constants to simplified lowering.
- Handle float32 representation for phis in simplified lowering.

In addition, contains the following (related) cleanups:
- Fix/unify naming of backend instructions.
- Use AVX comparisons when available.
- Extend ArchOpcodeField to 9 bits (required for arm64).
- Refactor some code duplication in instruction selectors.

BUG=v8:3589
LOG=n
R=dcarney@chromium.org

Committed: https://crrev.com/8dad78cdbd21c2cd02d6e0645313bd4b9983c78e
Cr-Commit-Position: refs/heads/master@{#27509}

[Benedikt Meurer, 2015-03-30 04:59:36]

PTAL

[dcarney, 2015-03-30 07:21:48]

lgtm, assuming all that assembler/disassembler stuff is correct.

[dcarney, 2015-03-30 07:31:32]

The CQ bit was checked by dcarney@chromium.org

[commit-bot: I haz the power, 2015-03-30 07:31:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1044793002/20001

[commit-bot: I haz the power, 2015-03-30 07:33:52]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-30 07:34:15]

Patchset 2 (id:??) landed as
https://crrev.com/8dad78cdbd21c2cd02d6e0645313bd4b9983c78e
Cr-Commit-Position: refs/heads/master@{#27509}

[jochen (gone - plz use gerrit), 2015-11-25 13:02:22]

jochen@chromium.org changed reviewers:
+ jochen@chromium.org

[jochen (gone - plz use gerrit), 2015-11-25 13:02:23]

https://codereview.chromium.org/1044793002/diff/20001/test/cctest/test-disasm...
File test/cctest/test-disasm-arm.cc (right):

https://codereview.chromium.org/1044793002/diff/20001/test/cctest/test-disasm...
test/cctest/test-disasm-arm.cc:98: // clang-format off
please don't do that. clang-format off is supposed to be used for a scope of
things you want to format differently, not as a blanket thing for an entire file