mirror of https://git.tukaani.org/xz.git
103 lines
4.1 KiB
CMake
103 lines
4.1 KiB
CMake
#
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# tuklib_integer.cmake - see tuklib_integer.m4 for description and comments
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#
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# Author: Lasse Collin
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#
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# This file has been put into the public domain.
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# You can do whatever you want with this file.
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#
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include("${CMAKE_CURRENT_LIST_DIR}/tuklib_common.cmake")
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include(TestBigEndian)
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include(CheckCSourceCompiles)
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include(CheckIncludeFile)
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include(CheckSymbolExists)
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function(tuklib_integer TARGET_OR_ALL)
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# Check for endianness. Unlike the Autoconf's AC_C_BIGENDIAN, this doesn't
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# support Apple universal binaries. The CMake module will leave the
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# variable unset so we can catch that situation here instead of continuing
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# as if we were little endian.
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test_big_endian(WORDS_BIGENDIAN)
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if(NOT DEFINED WORDS_BIGENDIAN)
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message(FATAL_ERROR "Cannot determine endianness")
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endif()
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tuklib_add_definition_if("${TARGET_OR_ALL}" WORDS_BIGENDIAN)
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# Look for a byteswapping method.
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check_c_source_compiles("
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int main(void)
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{
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__builtin_bswap16(1);
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__builtin_bswap32(1);
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__builtin_bswap64(1);
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return 0;
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}
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"
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HAVE___BUILTIN_BSWAPXX)
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if(HAVE___BUILTIN_BSWAPXX)
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tuklib_add_definitions("${TARGET_OR_ALL}" HAVE___BUILTIN_BSWAPXX)
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else()
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check_include_file(byteswap.h HAVE_BYTESWAP_H)
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if(HAVE_BYTESWAP_H)
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tuklib_add_definitions("${TARGET_OR_ALL}" HAVE_BYTESWAP_H)
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check_symbol_exists(bswap_16 byteswap.h HAVE_BSWAP_16)
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tuklib_add_definition_if("${TARGET_OR_ALL}" HAVE_BSWAP_16)
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check_symbol_exists(bswap_32 byteswap.h HAVE_BSWAP_32)
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tuklib_add_definition_if("${TARGET_OR_ALL}" HAVE_BSWAP_32)
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check_symbol_exists(bswap_64 byteswap.h HAVE_BSWAP_64)
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tuklib_add_definition_if("${TARGET_OR_ALL}" HAVE_BSWAP_64)
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else()
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check_include_file(sys/endian.h HAVE_SYS_ENDIAN_H)
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if(HAVE_SYS_ENDIAN_H)
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tuklib_add_definitions("${TARGET_OR_ALL}" HAVE_SYS_ENDIAN_H)
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else()
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check_include_file(sys/byteorder.h HAVE_SYS_BYTEORDER_H)
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tuklib_add_definition_if("${TARGET_OR_ALL}"
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HAVE_SYS_BYTEORDER_H)
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endif()
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endif()
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endif()
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# 16-bit and 32-bit unaligned access is fast on x86(-64),
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# big endian PowerPC, and usually on 32/64-bit ARM too.
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# There are others too and ARM could be a false match.
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#
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# Guess the default value for the option.
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# CMake's ability to give info about the target arch seems bad.
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# The the same arch can have different name depending on the OS.
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#
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# FIXME: The regex is based on guessing, not on factual information!
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#
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# NOTE: Compared to the Autoconf test, this lacks the GCC/Clang test
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# on ARM and always assumes that unaligned is fast on ARM.
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set(FAST_UNALIGNED_GUESS OFF)
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if(CMAKE_SYSTEM_PROCESSOR MATCHES
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"[Xx3456]86|^[Xx]64|^[Aa][Mm][Dd]64|^[Aa][Rr][Mm]|^aarch|^powerpc|^ppc")
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if(NOT WORDS_BIGENDIAN OR
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NOT CMAKE_SYSTEM_PROCESSOR MATCHES "^powerpc|^ppc")
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set(FAST_UNALIGNED_GUESS ON)
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endif()
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endif()
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option(TUKLIB_FAST_UNALIGNED_ACCESS
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"Enable if the system supports *fast* unaligned memory access \
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with 16-bit and 32-bit integers."
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"${FAST_UNALIGNED_GUESS}")
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tuklib_add_definition_if("${TARGET_OR_ALL}" TUKLIB_FAST_UNALIGNED_ACCESS)
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# Unsafe type punning:
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option(TUKLIB_USE_UNSAFE_TYPE_PUNNING
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"This introduces strict aliasing violations and \
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may result in broken code. However, this might improve performance \
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in some cases, especially with old compilers \
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(e.g. GCC 3 and early 4.x on x86, GCC < 6 on ARMv6 and ARMv7)."
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OFF)
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tuklib_add_definition_if("${TARGET_OR_ALL}" TUKLIB_USE_UNSAFE_TYPE_PUNNING)
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# Check for GCC/Clang __builtin_assume_aligned().
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check_c_source_compiles(
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"int main(void) { __builtin_assume_aligned(\"\", 1); return 0; }"
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HAVE___BUILTIN_ASSUME_ALIGNED)
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tuklib_add_definition_if("${TARGET_OR_ALL}" HAVE___BUILTIN_ASSUME_ALIGNED)
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endfunction()
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