[all-commits] [llvm/llvm-project] 2e47b9: [ARM] Honour -mno-movt in stack protector handling...

[Ard Biesheuvel via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2e47b93fd29ad6ef13a4134f3b0be3c42e91180c
      https://github.com/llvm/llvm-project/commit/2e47b93fd29ad6ef13a4134f3b0be3c42e91180c
  Author: Ard Biesheuvel <ardb at kernel.org>
  Date:   2024-10-09 (Wed, 09 Oct 2024)

  Changed paths:
    M llvm/lib/Target/ARM/Thumb2InstrInfo.cpp
    A llvm/test/CodeGen/ARM/stack-guard-nomovt.ll

  Log Message:
  -----------
  [ARM] Honour -mno-movt in stack protector handling (#109022)

When -mno-movt is passed to Clang, the ARM codegen correctly avoids
movt/movw pairs to take the address of __stack_chk_guard in the stack
protector code emitted into the function pro- and epilogues. However,
the Thumb2 codegen fails to do so, and happily emits movw/movt pairs
unless it is generating an ELF binary and the symbol might be in a
different DSO. Let's incorporate a check for useMovt() in the logic
here, so movt/movw are never emitted when -mno-movt is specified.

Suggestions welcome for how/where to add a test case for this.

Signed-off-by: Ard Biesheuvel <ardb at kernel.org>



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