[PATCH] [X86][SSE] Generalised unpackl/unpckh shuffle matching
chandlerc at gmail.com
Tue Feb 17 17:01:04 PST 2015
I really disagree with the direction of this commit. I'm sorry I've not replied more promptly, but I would like us to go back and look at *why* we cannot canonicalize this problem away, and if we cannot, making isShuffleMaskEquivalent do the commuting itself. I have an idea of how to implement the latter, but I really don't understand what is breaking canonicalizing yet.
I'm probably just being dense (sorry), I do believe there may be a fundamental problem here, but I'm not seeing it yet. undef lanes *never* impact what is canonical in either direction. Is there some opposing canonicalization rules that we have pick between, and that forces some cases to be canonicalized the wrong way?
More information about the llvm-commits