[PATCH] D50656: [X86] In EFLAGS copy pass, don't emit EXTRACT_SUBREG instructions since we're after peephole

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: chandlerc, rnk.

Normally the peephole pass converts EXTRACT_SUBREG to COPY instructions. But we're after peephole so we can't rely on it to clean these up.

To fix this, the eflags pass now emits a COPY with a subreg input.

I also noticed that in 32-bit mode we need to constrain the input to the copy to ensure the subreg is valid. Otherwise we'll fail verify-machineinstrs


https://reviews.llvm.org/D50656

Files:
  lib/Target/X86/X86FlagsCopyLowering.cpp
  test/CodeGen/X86/flags-copy-lowering.mir
  test/CodeGen/X86/pr38539.ll

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