[PATCH] D83708: Remove TwoAddressInstructinoPass::sink3AddrInstruction.

[James Y Knight via Phabricator via llvm-commits]

jyknight created this revision.
jyknight added reviewers: craig.topper, nickdesaulniers, void.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

This function has a bug which will incorrectly reschedule instructions
after an INLINEASM_BR (which can branch). (The bug may also allow
scheduling past a throwing-CALL, I'm not certain.)

I could fix that bug, but, as the removed FIXME noted, attempting to
move instructions _before_ converting to 3-addr, so as to avoid
needing to make the conversion in the first place is a better
idea. And, in fact, the code to do such reodering was added to this
pass in 2011, via the addition of the function rescheduleMIBelowKill

- only a few months after the FIXME was added. That reschedule code

does not contain the same bug.

The removal of this funciton is not a no-op: in some cases
sink3AddrInstruction would move an instruction after converting it to
3-addr form, when rescheduleMIBelowKill would not move before
converison.  However, this does not appear to be important: the
machine instruction scheduler can reorder the after-conversion
instructions, in any case.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D83708

Files:
  llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
  llvm/test/CodeGen/X86/callbr-asm-sink.ll
  llvm/test/CodeGen/X86/masked-iv-unsafe.ll
  llvm/test/CodeGen/X86/reverse_branches.ll
  llvm/test/CodeGen/X86/rotate-extract.ll
  llvm/test/CodeGen/X86/twoaddr-lea.ll
  llvm/test/CodeGen/X86/twoaddr-pass-sink.ll

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