[all-commits] [llvm/llvm-project] 095a0c: [CodeGen] precommit machine-latecleanup test

[Nick Desaulniers via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 095a0c67bb5705b2ebd91ecc039e73bbd6982cee
      https://github.com/llvm/llvm-project/commit/095a0c67bb5705b2ebd91ecc039e73bbd6982cee
  Author: Nick Desaulniers <ndesaulniers at google.com>
  Date:   2023-04-27 (Thu, 27 Apr 2023)

  Changed paths:
    A llvm/test/CodeGen/AArch64/machine-latecleanup-inlineasm.mir

  Log Message:
  -----------
  [CodeGen] precommit machine-latecleanup test

Demonstrates a hazard in machine-latecleanup.

Differential Revision: https://reviews.llvm.org/D149190


  Commit: 012ea747ed0275c499f69c82ac0f635f4c76f746
      https://github.com/llvm/llvm-project/commit/012ea747ed0275c499f69c82ac0f635f4c76f746
  Author: Nick Desaulniers <ndesaulniers at google.com>
  Date:   2023-04-27 (Thu, 27 Apr 2023)

  Changed paths:
    M llvm/lib/CodeGen/MachineLateInstrsCleanup.cpp
    M llvm/test/CodeGen/AArch64/machine-latecleanup-inlineasm.mir

  Log Message:
  -----------
  [CodeGen][MachineLastInstrsCleanup] fix INLINEASM_BR hazard

If the removable definition resides in an INLINEASM_BR target, the
reuseable candidate might not dominate the INLINEASM_BR.

   bb0:
      INLINEASM_BR &"" %bb.1
      renamable $x8 = MOVi64imm 29273397577910035
      B %bb.2
      ...
    bb1:
      renamable $x8 = MOVi64imm 29273397577910035
      renamable $x8 = ADDXri killed renamable $x8, 2048, 0
    bb2:

Removing the second mov is a hazard when the inline asm branches to bb1.

Skip such replacements when the to be removed instruction is in the
target of such an INLINEASM_BR instruction.

We could get more aggressive about this in the future, but for now
simply abort.

This is causing a boot failure on linux-4.19.y branches of the LTS Linux
kernel for ARCH=arm64 with CONFIG_RANDOMIZE_BASE=y (KASLR) and
CONFIG_UNMAP_KERNEL_AT_EL0=y (KPTI).

Link: https://reviews.llvm.org/D123394
Link: https://github.com/ClangBuiltLinux/linux/issues/1837

Thanks to @nathanchance for the report, and @ardb for debugging.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D149191


Compare: https://github.com/llvm/llvm-project/compare/d1c2034cce0d...012ea747ed02