[all-commits] [llvm/llvm-project] 26194d: [LFI][AArch64] Add PAC support for LFI (#207915)

[Zachary Yedidia via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 26194d4623650fd3f9b58cda34b318197613e702
      https://github.com/llvm/llvm-project/commit/26194d4623650fd3f9b58cda34b318197613e702
  Author: Zachary Yedidia <zyedidia at gmail.com>
  Date:   2026-07-15 (Wed, 15 Jul 2026)

  Changed paths:
    M llvm/docs/LFI.rst
    M llvm/include/llvm/MC/MCLFIRewriter.h
    M llvm/lib/MC/MCStreamer.cpp
    M llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
    M llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCLFIRewriter.cpp
    M llvm/lib/Target/AArch64/MCTargetDesc/AArch64MCLFIRewriter.h
    M llvm/test/MC/AArch64/LFI/guard-elim.s
    M llvm/test/MC/AArch64/LFI/mem-lr.s
    A llvm/test/MC/AArch64/LFI/pac-errors.s
    A llvm/test/MC/AArch64/LFI/pac.s
    M llvm/test/MC/AArch64/LFI/return.s

  Log Message:
  -----------
  [LFI][AArch64] Add PAC support for LFI (#207915)

This patch adds support for PAC instructions that sign `x30` by deferring
the LFI mask until the next control-flow instruction or label, allowing
an authentication instruction to run before the mask, which overwrites
the PAC signature bits in the top bits of the pointer. This relies on
FEAT_FPAC to provide a security benefit, which requires authentication
failure to cause a trap, rather than expecting the branch on an invalid
pointer to cause the trap.



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