Do not add values to HGraph in Lithium.

Do not add values to HGraph in Lithium.

Lithium uses indexes after the maximium value ID in the HGraph as indexes
of virtual registers and assumes that the maximum value ID does not change.

The IsStandardConstant and GetConstantXX functions could add constants to
HGraph, which aliased virtual registers with real values. This could confuse
the register allocator to think that a value in a virtual register is tagged
and to incorrectly set it in the pointer map.

BUG=298269
TEST=mjsunit/regress/regress-298269.js
R=verwaest@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=17599

[ulan, 2013-11-08 13:03:46]

Please take a look.

[Toon Verwaest, 2013-11-08 13:32:20]

lgtm with nit

https://chromiumcodereview.appspot.com/66693002/diff/1/src/lithium.cc
File src/lithium.cc (right):

https://chromiumcodereview.appspot.com/66693002/diff/1/src/lithium.cc#newcode426
src/lithium.cc:426: graph->DisallowAddingNewValues();
I'd swap the 2 lines above, just in the case someone decides to allocate HValues
in between those two lines.

[ulan, 2013-11-08 14:16:48]

Committed patchset #1 manually as r17599 (presubmit successful).