[PATCH] [DAGCombine] Don't generate atrocious shuffles for constant vectors

[Michael Kuperstein]

Thanks Sanjay, Andrea.

Sanjay, just removing the condition doesn't fix this example.
What do you think about committing the constant version first, and then looking at the rest?

Andrea, I'm not sure I understood. 
Do you prefer the logic to live only in getVectorShuffle() or be replicated both here and there? I'm not sure the first is sufficient. In any case, I'm not sure that would solve the issue Simon reported. That case also involves a bitcast that changes the number of vector elements, and  don't know if that's currently handled. I'll check.


http://reviews.llvm.org/D7093

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