Propagate and combine constants in Hydrogen

Propagate and combine constants in Hydrogen

BUG=none
TEST=none
Committed: http://code.google.com/p/v8/source/detail?r=10034

[m.m.capewell, 2011-11-04 14:52:37]

The patch passes all the tests in release mode, but fails the debug mode.
A few tests fail with following error.

# Fatal error in src/ia32/assembler-ia32-inl.h, line 293
# CHECK(!(v8::internal::Isolate::Current()->heap())->InNewSpace(obj)) failed

It looks like something goes wrong with the GC.
With GDB I can see that upon failure obj->IsHeapNumber() is true.
Are the double values incorrectly allocated when new HConstants are added to the
HGraph?

Any pointers or ideas where to look at to fix that?

[Sven Panne, 2011-11-07 09:49:44]

http://codereview.chromium.org/8473002/diff/1/src/flag-definitions.h
File src/flag-definitions.h (right):

http://codereview.chromium.org/8473002/diff/1/src/flag-definitions.h#newcode124
src/flag-definitions.h:124: DEFINE_bool(use_constant_propagation, true, "use
hydrogen constant propagation")
Is there a reason for this flag? If the patch works, I can't see a negative
effect of having it enabled permanently, and we already have about 100000
flags...

[Alexandre, 2011-11-07 09:56:00]

http://codereview.chromium.org/8473002/diff/1/src/flag-definitions.h
File src/flag-definitions.h (right):

http://codereview.chromium.org/8473002/diff/1/src/flag-definitions.h#newcode124
src/flag-definitions.h:124: DEFINE_bool(use_constant_propagation, true, "use
hydrogen constant propagation")
Removed!
On 2011/11/07 09:49:44, Sven wrote:
> Is there a reason for this flag? If the patch works, I can't see a negative
> effect of having it enabled permanently, and we already have about 100000
> flags...

[danno, 2011-11-07 23:10:14]

Adding Kevin. Please don't commit until we clarify signing of the CLA.

[danno, 2011-11-14 10:59:09]

Adding florian, since Kevin is out of the office this week. The license is OK,
the code still need review.

[fschneider, 2011-11-17 16:18:59]

lgtm

[fschneider, 2011-11-17 17:21:03]

On 2011/11/17 16:18:59, fschneider wrote:
> lgtm

I'll land it.