[all-commits] [llvm/llvm-project] 1708de: [XRay][compiler-rt][x86_64] Preserve flags in x86_...

[Ricky Zhou via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 1708de1abd512696cec383fee9381c3b498014dc
      https://github.com/llvm/llvm-project/commit/1708de1abd512696cec383fee9381c3b498014dc
  Author: Ricky Zhou <ricky at rzhou.org>
  Date:   2024-05-27 (Mon, 27 May 2024)

  Changed paths:
    M compiler-rt/lib/xray/xray_trampoline_x86_64.S

  Log Message:
  -----------
  [XRay][compiler-rt][x86_64] Preserve flags in x86_64 trampolines. (#89452)

Previously, some xray trampolines would modify condition codes (before
saving/after restoring flags) due to stack alignment instructions, which
use add/sub.

I am not aware of issues that this causes in practice (outside of the
situation described in https://github.com/llvm/llvm-project/pull/89364,
which is only problematic due to a different bug). Nevertheless, it
seems nicer and less error-prone for xray instrumentation to be as
unobstrusive/preserve as much state as possible.



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