[DAGCombiner] Fix a regression in method SimplifyVBinOp accidentally introduced by r199135.

[Andrea Di Biagio]

Thanks Juergen for looking into this!

I will modify the test removing the usage of FileCheck and commit the change.

Andrea

On Wed, Jan 15, 2014 at 7:07 PM, Juergen Ributzka <juergen at apple.com> wrote:
> Hi Andrea,
>
> that was a big think-o on my side. Thanks for catching this.
>
> In your patch the test case only checks if the code compiles. In this case we don't really need the FileCheck.
> Otherwise the patch LGTM.
>
> Cheers,
> Juergen
>
> On Jan 15, 2014, at 4:50 AM, Andrea Di Biagio <andrea.dibiagio at gmail.com> wrote:
>
>> Hi,
>>
>> this patch fixes a bug introduced by revision 199135 in method
>> DAGCombiner::SimplifyVBinOp'.
>>
>> Revision 199135 tried to simplify part of the logic in method
>> DAGCombiner::SimplifyVBinOp' introducing calls to method
>> 'BuildVectorSDNode::isConstant().
>>
>> However, that revision wrongly changed the check performed by method
>> DAGCombiner::SimplifyVBinOp to identify dag nodes that can be folded.
>>
>> Before revision 199135, that method only tried to simplify vector
>> binary operations if both operands were build_vector of
>> Constant/ConstantFP/Undef only.
>>
>> After revision 199135, method 'SimplifyVBinOp' behaves differently; it
>> attempts to simplify vector binary operations even if only one of the
>> two operands is a constant.
>>
>> The regression was originally reported by Patrik Hägglund H.
>> I reduced the original test case provided by Patrik and adapted it to
>> the regression suite (see file
>> test/CodeGen/X86/vbinop-simplify-bug.ll).
>>
>> Please let me know if ok to submit.
>>
>> Thanks,
>> Andrea Di Biagio
>> SN Systems - Sony Computer Entertainment Group.
>> <patch-simplify-vbinop.diff>
>