[all-commits] [llvm/llvm-project] 0f3bc0: [X86] Simplify part of the isel for X86ISD::FCMP/S...

[Craig Topper via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 0f3bc00a7d3cb223b4d5639723b8f71341c9df1e
      https://github.com/llvm/llvm-project/commit/0f3bc00a7d3cb223b4d5639723b8f71341c9df1e
  Author: Craig Topper <craig.topper at sifive.com>
  Date:   2021-06-25 (Fri, 25 Jun 2021)

  Changed paths:
    M llvm/lib/Target/X86/X86ISelDAGToDAG.cpp

  Log Message:
  -----------
  [X86] Simplify part of the isel for X86ISD::FCMP/STRICT_FCMP/STRICT_FCMPS.

We don't need to have the compare output a value and then copy it
to FPSW for use by FNSTSW. Instead we can just have the compare
output Glue and glue the FNSTSW to it. InstrEmitter effectively
performed this optimization when emitting the Machine IR. Doing
it directly simplifies the codes and reduces the work in
InstrEmitter. There's no change in the machine IR at the end of
isel before and after this change.