Chris Lattner a59eb7c09c 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
..
2010-02-11 01:31:01 +00:00
2010-02-08 23:27:46 +00:00