[PATCH] D121707: [llvm][AArch64] Insert "bti j" after call to setjmp

[David Spickett via Phabricator via llvm-commits]

DavidSpickett created this revision.
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Some implementations of setjmp will end with a br instead of a ret.
This means that the next instruction after a call to setjmp must be
a "bti j" (j for jump) to make this work when branch target identification
is enabled.

The BTI extension was added in armv8.5-a but the bti instruction is in the
hint space. This means we can emit it for any architecture version as long
as branch target enforcement flags are passed.

The starting point for the hint number is 32 then call adds 2, jump adds 4.
Hence "hint #36" for a "bti j" (and "hint #34" for the "bti c" you see
at the start of functions).

The existing Arm command line option -mno-bti-at-return-twice has been
applied to AArch64 as well.

Support is added to SelectionDAG Isel and GlobalIsel. FastIsel will
defer to SelectionDAG.

Based on the change done for M profile Arm in https://reviews.llvm.org/D112427

This is for https://github.com/llvm/llvm-project/issues/48888


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D121707

Files:
  clang/docs/ClangCommandLineReference.rst
  clang/docs/ReleaseNotes.rst
  clang/include/clang/Driver/Options.td
  clang/lib/Driver/ToolChains/Arch/AArch64.cpp
  llvm/lib/Target/AArch64/AArch64.td
  llvm/lib/Target/AArch64/AArch64ExpandPseudoInsts.cpp
  llvm/lib/Target/AArch64/AArch64FastISel.cpp
  llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
  llvm/lib/Target/AArch64/AArch64ISelLowering.h
  llvm/lib/Target/AArch64/AArch64InstrInfo.td
  llvm/lib/Target/AArch64/AArch64Subtarget.h
  llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp
  llvm/test/CodeGen/AArch64/setjmp-bti-no-enforcement.ll
  llvm/test/CodeGen/AArch64/setjmp-bti-outliner.ll
  llvm/test/CodeGen/AArch64/setjmp-bti.ll

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