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CMake: Add autodetection for 32-bit x86 CRC assembly usage

This commit is contained in:
Lasse Collin 2024-06-20 23:25:42 +03:00
parent dbc14f213e
commit a3d6eb797c
1 changed files with 18 additions and 15 deletions
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33
CMakeLists.txt
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@ -8,20 +8,6 @@
# thus it's still slightly experimental. Testing this especially
# outside GNU/Linux and Windows would be great now.
#
# A few things are still missing compared to the Autotools-based build:
#
# - 32-bit x86 assembly code for CRC32 and CRC64 isn't used by default.
# Use the option -DXZ_ASM_I386=ON on the CMake command line to
# enable the assembly files. They are compatible with Linux, *BSDs,
# Cygwin, MinGW-w64, and Darwin. They are NOT compatible with MSVC.
#
# NOTE: The C code includes a generic version compatible with all
# processors and CLMUL version that requires a new enough processor
# with the PCLMULQDQ instruction. If the 32-bit x86 assembly files
# are used, the CLMUL version in the C code is NOT built. On modern
# processors with CLMUL support, the C code should be faster than
# the assembly code while on old processors the assembly code wins.
#
# About CMAKE_BUILD_TYPE:
#
# - CMake's standard choices are fine to use for production builds,
@ -243,7 +229,24 @@ add_compile_definitions(
# Support 32-bit x86 assembly files.
if(NOT MSVC)
option(XZ_ASM_I386 "Enable 32-bit x86 assembly code" OFF)
# It's simplest to ask the compiler for the architecture because we
# know that on supported platforms __i386__ is defined.
#
# Checking CMAKE_SYSTEM_PROCESSOR wouldn't be so simple or as reliable
# because it could indicate x86-64 even if building for 32-bit x86
# because one doesn't necessarily use a CMake toolchain file when
# building 32-bit executables on a 64-bit system. Also, the strings
# that identify 32-bit or 64-bit x86 aren't standardized in CMake.
if(MINGW OR CYGWIN OR CMAKE_SYSTEM_NAME MATCHES
"^FreeBSD$|^GNU$|^Linux$|^MirBSD$|^NetBSD$|^OpenBSD$")
check_symbol_exists("__i386__" "" ASM_I386_DEFAULT)
else()
set(ASM_I386_DEFAULT OFF)
endif()
option(XZ_ASM_I386 "Enable 32-bit x86 assembly code"
"${ASM_I386_DEFAULT}")
if(XZ_ASM_I386)
enable_language(ASM)
endif()