Add ability to do "else-if" clauses in IfBuilder

Add ability to do "else-if" clauses in IfBuilder

- In an Else block it's possible to add more If<>'s in the same builder that are
  treated as an else if.
- Simplified and cleaned-up some of the IfBuilder's internals.

R=mstarzinger@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=17780

[danno, 2013-11-08 16:40:32]

PTAL

[Michael Starzinger, 2013-11-12 09:50:00]

This just blows my mind. LGTM.

https://codereview.chromium.org/66983002/diff/1/src/hydrogen.cc
File src/hydrogen.cc (right):

https://codereview.chromium.org/66983002/diff/1/src/hydrogen.cc#newcode1164
src/hydrogen.cc:1164: set_current_block(NULL);
This change confuses me. HGraphBuilder::FinishExitCurrentBlock is only ever
called with either HReturn or HAbnormalExit instructions. I agree that our block
building is in need of hardening, but this seems to introduce asymmetry to
HGraphBuilder::FinishCurrentBlock.

https://codereview.chromium.org/66983002/diff/1/src/hydrogen.h
File src/hydrogen.h (right):

https://codereview.chromium.org/66983002/diff/1/src/hydrogen.h#newcode1466
src/hydrogen.h:1466: void ThenDeopt(const char* reason) {
nit: Let's move that down to line 1474 into the block with the other deopts.

[danno, 2013-11-14 14:46:39]

Feedback addressed, landing

https://codereview.chromium.org/66983002/diff/1/src/hydrogen.cc
File src/hydrogen.cc (right):

https://codereview.chromium.org/66983002/diff/1/src/hydrogen.cc#newcode1164
src/hydrogen.cc:1164: set_current_block(NULL);
On 2013/11/12 09:50:00, Michael Starzinger wrote:
> This change confuses me. HGraphBuilder::FinishExitCurrentBlock is only ever
> called with either HReturn or HAbnormalExit instructions. I agree that our
block
> building is in need of hardening, but this seems to introduce asymmetry to
> HGraphBuilder::FinishCurrentBlock.

Done.

https://codereview.chromium.org/66983002/diff/1/src/hydrogen.h
File src/hydrogen.h (right):

https://codereview.chromium.org/66983002/diff/1/src/hydrogen.h#newcode1466
src/hydrogen.h:1466: void ThenDeopt(const char* reason) {
On 2013/11/12 09:50:00, Michael Starzinger wrote:
> nit: Let's move that down to line 1474 into the block with the other deopts.

Done.

[danno, 2013-11-15 10:36:09]

Committed patchset #2 manually as r17780 (presubmit successful).