extra/llvm12/add-fno-semantic-interposition.patch


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diff --git a/llvm/cmake/modules/HandleLLVMOptions.cmake b/llvm/cmake/modules/HandleLLVMOptions.cmake
--- a/llvm/cmake/modules/HandleLLVMOptions.cmake
+++ b/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