[CMake] Don't use -fno-semantic-interposition with Clang<=13

[MaskRay]

Summary

Clang 13 has a -fsanitize-coverage -fno-semantic-interposition bug (D117190)
which may lead to
relocation R_X86_64_PC32 cannot be used against symbol linker error
in -DLLVM_USE_SANITIZE_COVERAGE=ON build when a shared object is built (e.g.
-DLLVM_BUILD_LLVM_DYLIB=on).

For simplicity, just disallow Clang 13 entirely.

Note: GCC -fPIC performance benefits from -fno-semantic-interposition
dramatically. Clang benefits little. Using this option is more for a dogfood
purpose to test correctness of this option, because in the wild some important
packages like CPython uses this option.

[ljmf00]

Looks good. Isn't this supposed to stack with D117190? I often use the Phabricator related patches feature to stack patches and avoid merging them in the wrong order :)

[MaskRay]

In D117183#3241006, @ljmf00 wrote:

Looks good. Isn't this supposed to stack with D117190? I often use the Phabricator related patches feature to stack patches and avoid merging them in the wrong order :)

Technically yes. If we are sure that the issue will be fixed in 14.0.0 the dependency is not needed...

[MaskRay]

update description and comment

llvm/cmake/modules/HandleLLVMOptions.cmake

elseif( WIN32 OR CYGWIN)
     # 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: GCC<10.3 has a bug on SystemZ.
     #
     # 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.
+    # Clang 13 has a bug related to -fsanitize-coverage
+    # -fno-semantic-interposition (https://reviews.llvm.org/D117183).
     if ((CMAKE_COMPILER_IS_GNUCXX AND
          NOT (LLVM_NATIVE_ARCH STREQUAL "SystemZ" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 10.3))
-       OR (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND CMAKE_CXX_COMPILER_VERSION GREATER_EQUAL 13))
+       OR (CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND CMAKE_CXX_COMPILER_VERSION GREATER_EQUAL 14))
       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
          NOT Uppercase_CMAKE_BUILD_TYPE STREQUAL "DEBUG")
     add_flag_or_print_warning("-fno-shrink-wrap" FNO_SHRINK_WRAP)
   endif()