[PATCH] D102453: [CMake][ELF] Add -fno-semantic-interposition for GCC and Clang>=13

[Fangrui Song via Phabricator via llvm-commits]

MaskRay updated this revision to Diff 346597.
MaskRay retitled this revision from "[CMake][ELF] Add -fno-semantic-interposition for GCC" to "[CMake][ELF] Add -fno-semantic-interposition for GCC and Clang>=13".
MaskRay edited the summary of this revision.
MaskRay added a comment.

Enable for Clang >= 13


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D102453/new/

https://reviews.llvm.org/D102453

Files:
  llvm/cmake/modules/HandleLLVMOptions.cmake


Index: llvm/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -305,6 +305,17 @@
     # On Windows all code is PIC. MinGW warns if -fPIC is used.
   else()
     add_flag_or_print_warning("-fPIC" FPIC)
+    # Enable interprocedural optimizations for non-inline functions which would
+    # otherwise be disabled due to GCC -fPIC's default.
+    #
+    # Note: Clang allows IPO for -fPIC so this optimization is less effective.
+    # Older Clang may support -fno-semantic-interposition but it used local
+    # aliases to optimize global variables, which is incompatible with copy
+    # relocations due to -fno-pic.
+    if (CMAKE_COMPILER_IS_GNUCXX OR (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND
+        CMAKE_CXX_COMPILER_VERSION GREATER_EQUAL 13))
+      add_flag_if_supported("-fno-semantic-interposition" FNO_SEMANTIC_INTERPOSITION)
+    endif()
   endif()
   # GCC for MIPS can miscompile LLVM due to PR37701.
   if(CMAKE_COMPILER_IS_GNUCXX AND LLVM_NATIVE_ARCH STREQUAL "Mips" AND


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