Ignore observed Double output in binary operations when all uses are truncating to Integer32

Ignore observed Double output in binary operations when all uses are truncating to Integer32

BUG=v8:2424
Committed: http://code.google.com/p/v8/source/detail?r=14381

[Jakob Kummerow, 2013-04-22 13:22:07]

PTAL.

[Sven Panne, 2013-04-22 13:52:29]

LGTM after a small refactoring.

https://codereview.chromium.org/14320021/diff/5001/src/hydrogen-instructions.cc
File src/hydrogen-instructions.cc (right):

https://codereview.chromium.org/14320021/diff/5001/src/hydrogen-instructions....
src/hydrogen-instructions.cc:2255: if
(observed_output_representation_.is_more_general_than(rep)) {
Simplifying this a bit and extracting a predicate makes this much more readable:

-----------------------------------------------
bool HBinaryoperation::IgnoreObservedOutputRepresentation(Representation rep) {
  return observed_output_representation_.IsDouble() &&
      rep.IsInteger32() &&
      !this->IsDiv() &&
      CheckUsesForFlag(kTruncatingToInt32);
}


In HBinaryOperation::RepresentationFromInputs:
...
  if (observed_output_representation_.is_more_general_than(rep) &&
      !IgnoreObservedOutputRepresentation(rep)) {
    rep = observed_output_representation_;
  }
...
-----------------------------------------------

[Jakob Kummerow, 2013-04-22 15:24:41]

As discussed offline, I additionally had to prevent Mul instructions from
ignoring their observed output type.

https://codereview.chromium.org/14320021/diff/5001/src/hydrogen-instructions.cc
File src/hydrogen-instructions.cc (right):

https://codereview.chromium.org/14320021/diff/5001/src/hydrogen-instructions....
src/hydrogen-instructions.cc:2255: if
(observed_output_representation_.is_more_general_than(rep)) {
On 2013/04/22 13:52:29, Sven Panne wrote:
> Simplifying this a bit and extracting a predicate makes this much more
readable:
> 
> -----------------------------------------------
> bool HBinaryoperation::IgnoreObservedOutputRepresentation(Representation rep)
{
>   return observed_output_representation_.IsDouble() &&
>       rep.IsInteger32() &&
>       !this->IsDiv() &&
>       CheckUsesForFlag(kTruncatingToInt32);
> }
> 
> 
> In HBinaryOperation::RepresentationFromInputs:
> ...
>   if (observed_output_representation_.is_more_general_than(rep) &&
>       !IgnoreObservedOutputRepresentation(rep)) {
>     rep = observed_output_representation_;
>   }
> ...
> -----------------------------------------------

Done.

[Jakob Kummerow, 2013-04-22 16:31:22]

Committed patchset #3 manually as r14381 (presubmit successful).