Implement support for Math.imul in Crankshaft.

Implement support for Math.imul in Crankshaft.

R=jkummerow@chromium.org
TEST=mjsunit/math-imul

Committed: http://code.google.com/p/v8/source/detail?r=14450

[Jakob Kummerow, 2013-04-26 08:38:25]

lgtm

[Michael Starzinger, 2013-04-26 08:52:45]

Committed patchset #1 manually as r14450 (presubmit successful).

[Sven Panne, 2013-04-29 06:36:00]

Small DBC how to improve this CL.

https://codereview.chromium.org/14471041/diff/1/src/math.js
File src/math.js (right):

https://codereview.chromium.org/14471041/diff/1/src/math.js#newcode220
src/math.js:220: return %NumberImul(x, y);
I think the right way to implement this would be renaming this to "_MathImul",
add kMathImul to INLINE_FUNCTION_LIST instead of RUNTIME_FUNCTION_LIST_ALWAYS,
and implement a HOptimizedGraphBuilder::GenerateMathImul.

As it is, I am relatively sure that we get some bailouts, though I haven't
tested it.

[Michael Starzinger, 2013-04-29 08:54:18]

Yes, as discussed offline that is an additional optimization that we can do to
get all the goodness even when Math.imul is not inlined and it avoids the
overhead of a runtime call in full codegen.