Ensure constant truncation is only done when it is safe.

Ensure constant truncation is only done when it is safe.

BUG=
R=mstarzinger@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16766

[Michael Starzinger, 2013-09-17 12:10:13]

LGTM if comment is addressed.

https://codereview.chromium.org/23654041/diff/3001/src/hydrogen-instructions.cc
File src/hydrogen-instructions.cc (right):

https://codereview.chromium.org/23654041/diff/3001/src/hydrogen-instructions....
src/hydrogen-instructions.cc:2584: Zone* zone, HGraphBuilder* builder) {
I don't like passing around the HGraphBuilder into HInstructions. I see that
this would give static guarantees that no-one introduces call to this method
outside the graph builder, but it destroys decoupling please revert this part of
the change and just keep the fix in HConstant::CopyToTruncatedInt32.

[oliv, 2013-09-17 12:20:50]

Committed patchset #2 manually as r16766 (presubmit successful).