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

[Andrea Di Biagio]

Hi Michael,

Most of the canonicalization rules performed by the dag combiner on shuffle nodes are the same rules implemented by method 'SelectionDAG::getVectorShuffle' in SelectionDAG.cpp.
If you add a new canonicalization rule in method getVectorShuffle, then you probably need to update method 'getVectorShuffle' as well. I guess, this would (hopefully) fix the problem with the missing constant folding reported by Simon.

I hope this helps!
Andrea


http://reviews.llvm.org/D7093

EMAIL PREFERENCES
  http://reviews.llvm.org/settings/panel/emailpreferences/