[all-commits] [llvm/llvm-project] 613a2a: [AArch64][PAC] Protect the entire function if pac-...

[Anatoly Trosinenko via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 613a2a1359370bc5ab3fbf71b4e89ae4211467c7
      https://github.com/llvm/llvm-project/commit/613a2a1359370bc5ab3fbf71b4e89ae4211467c7
  Author: Anatoly Trosinenko <atrosinenko at accesssoftek.com>
  Date:   2025-07-09 (Wed, 09 Jul 2025)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64FrameLowering.cpp
    M llvm/lib/Target/AArch64/AArch64FrameLowering.h
    M llvm/test/CodeGen/AArch64/sign-return-address-cfi-negate-ra-state.ll
    M llvm/test/CodeGen/AArch64/sign-return-address-pauth-lr.ll
    M llvm/test/CodeGen/AArch64/sign-return-address-tailcall.ll
    M llvm/test/CodeGen/AArch64/sign-return-address.ll

  Log Message:
  -----------
  [AArch64][PAC] Protect the entire function if pac-ret+leaf is requested (#140895)

Normally, pac-ret hardening is emitted as part of function prologues and
epilogues, thus it is affected by the shrink-wrapping optimization.

As protecting LR when it is spilled to the stack is already handled by
regular -mbranch-protection=pac-ret option, it is reasonable to assume
that pac-ret+leaf option means the user wants to apply pac-ret hardening
to as much code as possible. For that reason, if pac-ret+leaf hardening
mode is requested, this patch moves the emission of PAUTH_PROLOGUE (or
PAUTH_EPILOGUE) pseudos from emitPrologue (emitEpilogue) methods of the
AArch64FrameLowering class to processFunctionBeforeFrameIndicesReplaced.
This change does not currently affect targets that emit WinCFI unwind
information.

This commit only affects where LR is signed and authenticated, but does
not otherwise prevents the shrink-wrapping optimization. Moreover,
without "+leaf" modifier PAUTH_(PROLOGUE|EPILOGUE) pseudos respect the
shrink-wrapping optimization just as any other prologue/epilogue code.



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