Chris Lattner 4e8137d678 Rename ValueRequiresCast to ShouldOptimizeCast, to better reflect ...

what it does.  Enhance it to return false to optimizing vector
sign extensions from vector comparisions, which is the idiom used
to get a splatted vector for a vector comparison.

Doing this breaks vector-casts.ll, add some compensating 
transformations to handle the important case they cover without
depending on this canonicalization.

This fixes rdar://7434900 a serious pessimization of vector compares.

llvm-svn: 95855

2010-02-11 06:26:33 +00:00

3.4 KiB

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