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

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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.

Differential Revision: https://reviews.llvm.org/D117183
This commit is contained in:
Fangrui Song 2022-01-13 15:38:02 -08:00
parent 5d5d4d94f0
commit 1661c8cfcd
1 changed files with 3 additions and 4 deletions
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7
llvm/cmake/modules/HandleLLVMOptions.cmake
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@ -315,12 +315,11 @@ if( LLVM_ENABLE_PIC )
# 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()