[all-commits] [llvm/llvm-project] ed27f1: __sys builtin support for AArch64 (#146456)

[Adam Glass via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: ed27f18e324de1441bb062c6b2ffd2be5875a952
      https://github.com/llvm/llvm-project/commit/ed27f18e324de1441bb062c6b2ffd2be5875a952
  Author: Adam Glass <adamglass at microsoft.com>
  Date:   2025-07-02 (Wed, 02 Jul 2025)

  Changed paths:
    M clang/include/clang/Basic/BuiltinsAArch64.def
    M clang/lib/CodeGen/TargetBuiltins/ARM.cpp
    M clang/lib/Headers/intrin.h
    M clang/lib/Sema/SemaARM.cpp
    A clang/test/CodeGen/arm64-microsoft-sys.c
    M clang/test/Sema/builtins-microsoft-arm64.c

  Log Message:
  -----------
  __sys builtin support for AArch64 (#146456)

Adds support for __sys Clang builtin for AArch64

__sys is a long existing MSVC intrinsic used to manage caches, tlbs, etc
by writing to system registers:
* It takes a macro-generated constant and uses it to form the AArch64 SYS instruction which is MSR with op0=1. The macro drops op0 and expects the implementation to hardcode it to 1 in the encoding.
* Volume use is in systems code (kernels, hypervisors, boot environments, firmware)
* Has an unused return value due to MSVC cut/paste error

Implementation:
* Clang builtin, sharing code with Read/WriteStatusReg
* Hardcodes the op0=1
* Explicitly returns 0
* Code-format change from clang-format
* Unittests included
* Not limited to MSVC-environment as its generally useful and neutral



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