Remove previous_ast_id and related code in hydrogen.

Remove previous_ast_id and related code in hydrogen.

BUG=

Committed: https://code.google.com/p/v8/source/detail?r=14308

[Hannes Payer (out of office), 2013-04-17 11:34:47]

LGTM

[danno, 2013-04-17 12:04:06]

lgtm if you address my comment

https://codereview.chromium.org/14178011/diff/1/src/hydrogen.cc
File src/hydrogen.cc (right):

https://codereview.chromium.org/14178011/diff/1/src/hydrogen.cc#newcode236
src/hydrogen.cc:236: predecessor->last_environment()->set_ast_id(ast_id);
This turns out to be wrong. Please remove this last line, there is no need to
set the predecessor's ast_id here.

[titzer, 2013-04-17 13:19:16]

https://codereview.chromium.org/14178011/diff/1/src/hydrogen.cc
File src/hydrogen.cc (right):

https://codereview.chromium.org/14178011/diff/1/src/hydrogen.cc#newcode236
src/hydrogen.cc:236: predecessor->last_environment()->set_ast_id(ast_id);
On 2013/04/17 12:04:06, danno wrote:
> This turns out to be wrong. Please remove this last line, there is no need to
> set the predecessor's ast_id here.

Tried this, and many tests are now failing with

#
# Fatal error in ../src/hydrogen.cc, line 555
# CHECK(predecessor->last_environment()->ast_id() == id) failed
#

This is in code that was added in this CL, copied over from the pre-previous_ast
code. Should I also remove these checks?

[danno, 2013-04-17 13:22:51]

https://codereview.chromium.org/14178011/diff/1/src/hydrogen.cc
File src/hydrogen.cc (right):

https://codereview.chromium.org/14178011/diff/1/src/hydrogen.cc#newcode236
src/hydrogen.cc:236: predecessor->last_environment()->set_ast_id(ast_id);
I must have been confused. I think it is only incorrect if you also include the
follow-on changes that I have, it's true that the assert you added back in
checks this. After hunting around, I found that lithium overwrites this ast_id
anyway, so the value set here doesn't matter, so it's ok to keep in. So, LGTM
On 2013/04/17 13:19:16, titzer wrote:
> On 2013/04/17 12:04:06, danno wrote:
> > This turns out to be wrong. Please remove this last line, there is no need
to
> > set the predecessor's ast_id here.
> 
> Tried this, and many tests are now failing with
> 
> #
> # Fatal error in ../src/hydrogen.cc, line 555
> # CHECK(predecessor->last_environment()->ast_id() == id) failed
> #
> 
> This is in code that was added in this CL, copied over from the
pre-previous_ast
> code. Should I also remove these checks?

[titzer, 2013-04-17 14:11:47]

Committed patchset #1 manually as r14308 (presubmit successful).