[PATCH] [X86][AVX] Fix wrong lowering of VPERM2X128 nodes.

[Andrea Di Biagio]

In http://reviews.llvm.org/D8119#136324, @mkuper wrote:

> I may be missing something, but I don't see how this helps.
>  We'll still get a nonsense MaskLO if both Mask[0] and Mask[1] are SM_SentinelUndef, and SM_SentinelUndef happens to be INT_MIN.
>  Why not set MaskLO/MaskHI to 0 explicitly if both relevant Mask elements are undef?
>
> (I know this is purely theoretical, if you feel it unnecessarily complicates the code, feel free to ignore.)


Ok right. Now I think I understand what you meant before :-).
Sorry for the confusion..

Right, I can change the code so that we propagate index 0 if the resulting permute index is SM_SentinelUndef.


http://reviews.llvm.org/D8119

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