Fix dependency of loading the heap-number for a double-field store to be the mapcheck.

Fix dependency of loading the heap-number for a double-field store to be the mapcheck.

R=jkummerow@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16306

[Toon Verwaest, 2013-08-23 13:13:23]

PTAL

[Jakob Kummerow, 2013-08-23 13:27:28]

LGTM.

[Jakob Kummerow, 2013-08-23 15:41:03]

https://chromiumcodereview.appspot.com/22926027/diff/5001/src/hydrogen-escape...
File src/hydrogen-escape-analysis.cc (right):

https://chromiumcodereview.appspot.com/22926027/diff/5001/src/hydrogen-escape...
src/hydrogen-escape-analysis.cc:215: ASSERT(mapcheck->ActualValue() ==
allocate);
Looking at the line before (212), I don't think we need this ASSERT.

[Toon Verwaest, 2013-08-23 16:31:40]

Committed patchset #2 manually as r16306.

[Michael Starzinger, 2013-08-24 07:39:31]

The reason why this tanks performance is because it broke both write-barrier
removal (see HSToreNamedField::NeedsWriteBarrier) and map-check removal (see
HCheckMaps::HandleSideEffectDominator). It might be worth looking at those two
mechanisms before making such significant changes to the hydrogen graph.

[Toon Verwaest, 2013-08-24 10:02:34]

I presumed as much. Thanks for looking into it though.