[all-commits] [llvm/llvm-project] ab3c0c: [AArch64][PAC] Do not execute AUT instructions spe...

[Anatoly Trosinenko via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ab3c0ca8351b0b40f57dfa97a21d913bbbda71c3
      https://github.com/llvm/llvm-project/commit/ab3c0ca8351b0b40f57dfa97a21d913bbbda71c3
  Author: Anatoly Trosinenko <atrosinenko at accesssoftek.com>
  Date:   2025-08-27 (Wed, 27 Aug 2025)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64InstrInfo.td
    M llvm/test/CodeGen/AArch64/ptrauth-intrinsic-auth-resign.ll

  Log Message:
  -----------
  [AArch64][PAC] Do not execute AUT instructions speculatively (#155372)

A generic authentication instruction may crash the process on failure.
Furthermore, it can be executed conditionally and/or its signing schema
can be chosen dynamically. For this reason, while it may be beneficial
to permit DCE to remove AUTx16x17 or AUTxMxN instructions unless their
results have any uses (at least fake ones, if we just want to check the
signature), AUT instructions are not safe to be executed speculatively.

As a quick fix for miscompilation possibility, this patch marks AUTxMxN
pseudo instruction as having unmodelled side effects.



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