[PATCH] D34904: [CGP] use subtract of cmps for result of memcmp expansion

[Sanjay Patel via Phabricator via llvm-commits]

spatel added a comment.

I almost forgot another hidden motivation that I need to mention in case we ever come back to the idea for x86 or other targets try to hack this: I was looking to use vector-length types in this expansion on x86 for 16-byte and larger memcmp. Because of existing DAG transforms, the x86 codegen would become a strange mix of scalar and vector code with the select-based IR in this expansion...and that would have required several steps to undo. Using subtract-of-cmps avoided that. :) 
See: https://bugs.llvm.org/show_bug.cgi?id=33329 for detailed analysis.


https://reviews.llvm.org/D34904