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Author SHA1 Message Date
Sanjay Patel ca92c36e01 [DAG] enhance computeKnownBits to handle SHL with vector splat constant 
Also, use APInt to avoid crashing on types larger than vNi64.

llvm-svn: 284874
 2016-10-21 20:16:27 +00:00
Sanjay Patel 81029f6a76 [DAG] fold negation of sign-bit 
0 - X --> 0, if the sub is NUW
0 - X --> 0, if X is 0 or the minimum signed value and the sub is NSW
0 - X --> X, if X is 0 or the minimum signed value

This is the DAG equivalent of:
https://reviews.llvm.org/rL284649

plus the fold for the NUW case which already existed in InstSimplify.

Note that we miss a vector fold because of a deficiency in the DAG version of
computeKnownBits().

llvm-svn: 284844
 2016-10-21 17:24:26 +00:00
Sanjay Patel 97de8a4c3a [x86] add tests for potential negation folds 
These are the backend equivalents for the tests added in r284627.
The patterns may emerge late, so we should have folds for these in the DAG too.

llvm-svn: 284842
 2016-10-21 16:56:29 +00:00