[all-commits] [llvm/llvm-project] d0797e: Re-apply "[CMake][compiler-rt][AArch64] Avoid prep...

[Raul Tambre via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: d0797e62fa8a73ad75dcaca7c0e1a71c2001c855
      https://github.com/llvm/llvm-project/commit/d0797e62fa8a73ad75dcaca7c0e1a71c2001c855
  Author: Raul Tambre <raul at tambre.ee>
  Date:   2020-12-14 (Mon, 14 Dec 2020)

  Changed paths:
    M compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
    M compiler-rt/lib/builtins/CMakeLists.txt
    M compiler-rt/lib/builtins/aarch64/lse.S

  Log Message:
  -----------
  Re-apply "[CMake][compiler-rt][AArch64] Avoid preprocessing LSE builtins separately"

aa772fc85e0f526615c78b9c3979c2be945a754c (D92530) has landed fixing Apple builds.
Previous quick-fix d9697c2e6b153ac7dc40a69450d9b672f71b1029 (D93198) included in this commit.

Invoking the preprocessor ourselves is fragile and would require us to replicate CMake's handling of definitions, compiler flags, etc for proper compatibility.
In my toolchain builds this notably resulted in a bunch of warnings from unused flags as my CMAKE_C_FLAGS includes CPU-specific optimization options.
Notably this part was already duplicating the logic for VISIBILITY_HIDDEN define.

Instead, symlink the files and set the proper set of defines on each.
This should also be faster as we avoid invoking the compiler multiple times.

Fixes https://llvm.org/PR48494

Differential Revision: https://reviews.llvm.org/D93211