[PATCH] D34184: [InstCombine] Teach foldSelectICmpAndOr to recognize (select (icmp slt (trunc (X)), 0), Y, (or Y, C2))

[Craig Topper via Phabricator via llvm-commits]

craig.topper added a comment.

I think you're right. The 'icmp' and the 'or' pieces aren't checked for single use. In the existing code we do reuse the 'and'. In my new code i did make sure the trunc only had one use so that putting back an 'and' doesn't increase anything. So in the existing code we potentially create an 'or' and possibly a 'shift' and only delete a 'select'. And the really bad case we create an 'xor', an 'or', and a 'shift' while only removing a 'select'. This is kinda weird to handle because we don't always create a shift and don't always create an xor.


https://reviews.llvm.org/D34184