tree c83e477197ec616d7c7a1672a6b29231de23ba4e
parent 0558ccb3eeb309fcb340d8dd1409ced78c289d05
author Simon Pilgrim <llvm-dev@redking.me.uk> 1618491332 +0100
committer Copybara-Service <copybara-worker@google.com> 1618602978 -0700

[X86] combineCMP - fold cmpEQ/NE(TRUNC(X),0) -> cmpEQ/NE(X,0)

If we are truncating from a i32 source before comparing the result against zero, then see if we can directly compare the source value against zero.

If the upper (truncated) bits are known to be zero then we can compare against that, hopefully increasing the chances of us folding the compare into a EFLAG result of the source's operation.

Fixes PR49028.

Differential Revision: https://reviews.llvm.org/D100491

GitOrigin-RevId: 9d57a77b81265c650c75511115067588790d7ac0