[PATCH] D112427: [ARM] Implement setjmp BTI placement for PACBTI-M

[Ties Stuij via Phabricator via llvm-commits]

stuij created this revision.
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This patch intends to guard indirect branches performed by longjmp
by inserting BTI instructions after calls to setjmp.

Calls with 'returns-twice' are lowered to a new pseudo-instruction
named t2CALL_BTI that is later expanded to a bundle of {tBL,t2BTI}.

We only perform this transformation when armlib is not in use.
That information is passed on by the module flags.

This patch is part of a series that adds support for the PACBTI-M extension of
the Armv8.1-M architecture, as detailed here:

https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/armv8-1-m-pointer-authentication-and-branch-target-identification-extension

The PACBTI-M specification can be found in the Armv8-M Architecture Reference
Manual:

https://developer.arm.com/documentation/ddi0553/latest

The following people contributed to this patch:

- Alexandros Lamprineas
- Ties Stuij


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D112427

Files:
  llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp
  llvm/lib/Target/ARM/ARMISelLowering.cpp
  llvm/lib/Target/ARM/ARMISelLowering.h
  llvm/lib/Target/ARM/ARMInstrThumb2.td
  llvm/test/CodeGen/ARM/setjmp-bti-basic.ll
  llvm/test/CodeGen/ARM/setjmp-bti-outliner.ll

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