Improve GVN dependency tracking by adding parameters to certain flags.

Improve GVN dependency tracking by adding parameters to certain flags.

A set of GVN flags with parameters is represented by a zone-allocated
HEffectSet.

This changes allows global, context, and field loads and stores that
operate on different cells, slot indices, and field indices to become
independent.

[fschneider, 2011-03-16 15:43:28]

LGTM.

I'm curious about the performance improvements. 

However we should keep an eye on the increased allocation and compile time. If
this causes a big degradation, we should consider optimizing the underlying data
structures in gvn.

http://codereview.chromium.org/6690006/diff/1/src/hydrogen-instructions.h
File src/hydrogen-instructions.h (right):

http://codereview.chromium.org/6690006/diff/1/src/hydrogen-instructions.h#new...
src/hydrogen-instructions.h:2950: return (offset_ << 1) || (is_in_object_ ? 1 :
0);
Shouldn't be this bitwise-or "|"?

http://codereview.chromium.org/6690006/diff/1/src/hydrogen-instructions.h#new...
src/hydrogen-instructions.h:3123: return (offset_ << 1) || (is_in_object_ ? 1 :
0);
-> use "|" here as well.

http://codereview.chromium.org/6690006/diff/1/src/hydrogen.cc
File src/hydrogen.cc (right):

http://codereview.chromium.org/6690006/diff/1/src/hydrogen.cc#newcode1010
src/hydrogen.cc:1010: HEffectSet() : parameters_(0) {
Since Initialize() also initializes paramters_, there is no need to mention it
in the initializer list.

http://codereview.chromium.org/6690006/diff/1/src/hydrogen.cc#newcode1014
src/hydrogen.cc:1014: explicit HEffectSet(int flags) : parameters_(0) {
Same here.

http://codereview.chromium.org/6690006/diff/1/src/hydrogen.cc#newcode1039
src/hydrogen.cc:1039: int flag = i << 1;
You could move this line to after the continue.

http://codereview.chromium.org/6690006/diff/1/src/hydrogen.cc#newcode1102
src/hydrogen.cc:1102: if (parameters_.length() <= flag_index) {
I find (flag_index >= parameters_.length()) better.