ComputeKnownBits: be a bit smarter about ADDs
authorFiona Glaser <escha@apple.com>
Fri, 10 Jul 2015 18:29:02 +0000 (18:29 +0000)
committerFiona Glaser <escha@apple.com>
Fri, 10 Jul 2015 18:29:02 +0000 (18:29 +0000)
commitb0a2d8c5a51ebf0944fe271dc742550979e6877c
tree6cacbd4b3187dddc8d3803ea55c08b095ab00e4b
parent02e89ace701217b8477b3262f726c00338cce5fe
ComputeKnownBits: be a bit smarter about ADDs

If our two inputs have known top-zero bit counts M and N, we trivially
know that the output cannot have any bits set in the top (min(M, N)-1)
bits, since nothing could carry past that point.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@241927 91177308-0d34-0410-b5e6-96231b3b80d8
lib/CodeGen/SelectionDAG/SelectionDAG.cpp
test/CodeGen/AArch64/aarch64-dynamic-stack-layout.ll
test/CodeGen/X86/win64_frame.ll