[PATCH] D112421: [clang][ARM] PACBTI-M frontend support

[Ties Stuij via Phabricator via cfe-commits]

stuij created this revision.
Herald added subscribers: dexonsmith, hiraditya, kristof.beyls.
Herald added a reviewer: aaron.ballman.
stuij requested review of this revision.
Herald added projects: clang, LLVM.
Herald added subscribers: llvm-commits, cfe-commits.

Handle branch protection option on the commandline as well as a function
attribute. One patch for both mechanisms, as they use the same underlying
parsing mechanism.

These are recorded in a set of LLVM IR module-level attributes like we do for
AArch64 PAC/BTI (see https://reviews.llvm.org/D85649):

- command-line options are "translated" to module-level LLVM IR attributes (metadata).

- functions have PAC/BTI specific attributes iff the __attribute__((target("branch-protection=...))) was used in the function declaration.

- command-line option -mbranch-protection to armclang targeting Arm,

following this grammar:

branch-protection ::= "-mbranch-protection=" <protection>
protection ::=  "none" | "standard" | "bti" [ "+" <pac-ret-clause> ]

  | <pac-ret-clause> [ "+" "bti"]

pac-ret-clause ::= "pac-ret" [ "+" <pac-ret-option> ]
pac-ret-option ::= "leaf" ["+" "b-key"] | "b-key" ["+" "leaf"]

b-key is simply a placeholder to make it consistent with AArch64's
version. In Arm, however, it triggers a warning informing that b-key is
unsupported and a-key will be selected instead.

- Handle _attribute_((target(("branch-protection=..."))) for AArch32 with the

same grammer as the commandline options.

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:

- Momchil Velikov
- Victor Campos
- Ties Stuij


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D112421

Files:
  clang/include/clang/Basic/DiagnosticDriverKinds.td
  clang/include/clang/Basic/DiagnosticGroups.td
  clang/include/clang/Basic/DiagnosticSemaKinds.td
  clang/lib/Basic/Targets/AArch64.cpp
  clang/lib/Basic/Targets/ARM.cpp
  clang/lib/Basic/Targets/ARM.h
  clang/lib/CodeGen/CodeGenModule.cpp
  clang/lib/CodeGen/TargetInfo.cpp
  clang/lib/Driver/ToolChains/Clang.cpp
  clang/lib/Sema/SemaDeclAttr.cpp
  clang/test/CodeGen/arm-branch-protection-attr-1.c
  clang/test/CodeGen/arm-branch-protection-attr-2.c
  clang/test/CodeGen/arm_neon_intrinsics.c
  clang/test/Driver/arm-security-options.c
  clang/test/Frontend/arm-invalid-branch-protection.c
  clang/test/Sema/aarch64-branch-protection-attr-err.c
  clang/test/Sema/arm-branch-protection-attr-err.c
  clang/test/Sema/branch-protection-attr-err.c
  llvm/include/llvm/Support/AArch64TargetParser.h
  llvm/include/llvm/Support/TargetParser.h
  llvm/lib/Support/AArch64TargetParser.cpp
  llvm/lib/Support/TargetParser.cpp

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