[PATCH] D146121: [DAG] Move lshr narrowing from visitANDLike to SimplifyDemandedBits (WIP)

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n added inline comments.


================
Comment at: llvm/test/CodeGen/X86/h-register-addressing-64.ll:67
+; CHECK-NEXT:    andl $2040, %esi # imm = 0x7F8
+; CHECK-NEXT:    movzbl (%rdi,%rsi), %eax
 ; CHECK-NEXT:    retq
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I think this is okay here. We only get the right codegen by chance here and I don't think its something we can reasonably control during DAG isel.

I tried to improve this with D141653. Looked good for the tests but caused infinite loop in bootstrap build.

I think this (along with other `imm` level optimizations), need to be moved to a new pass (or function in isel) that runs at the very end.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D146121/new/

https://reviews.llvm.org/D146121