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Diffstat (limited to 'cmake/tuklib_integer.cmake')
| -rw-r--r-- | cmake/tuklib_integer.cmake | 100 |
1 files changed, 100 insertions, 0 deletions
diff --git a/cmake/tuklib_integer.cmake b/cmake/tuklib_integer.cmake new file mode 100644 index 00000000..aeb7ff6f --- /dev/null +++ b/cmake/tuklib_integer.cmake @@ -0,0 +1,100 @@ +# +# tuklib_integer.cmake - see tuklib_integer.m4 for description and comments +# +# Author: Lasse Collin +# +# This file has been put into the public domain. +# You can do whatever you want with this file. +# + +include(${CMAKE_CURRENT_LIST_DIR}/tuklib_common.cmake) +include(TestBigEndian) +include(CheckCSourceCompiles) +include(CheckIncludeFile) +include(CheckSymbolExists) + +function(tuklib_integer TARGET_OR_ALL) + # Check for endianness. Unlike the Autoconf's AC_C_BIGENDIAN, this doesn't + # support Apple universal binaries. The CMake module will leave the + # variable unset so we can catch that situation here instead of continuing + # as if we were little endian. + test_big_endian(WORDS_BIGENDIAN) + if(NOT DEFINED WORDS_BIGENDIAN) + message(FATAL_ERROR "Cannot determine endianness") + endif() + tuklib_add_definition_if(${TARGET_OR_ALL} WORDS_BIGENDIAN) + + # Look for a byteswapping method. + check_c_source_compiles(" + int main(void) + { + __builtin_bswap16(1); + __builtin_bswap32(1); + __builtin_bswap64(1); + return 0; + } + " + HAVE___BUILTIN_BSWAPXX) + if(HAVE___BUILTIN_BSWAPXX) + tuklib_add_definitions(${TARGET_OR_ALL} HAVE___BUILTIN_BSWAPXX) + else() + check_include_file(byteswap.h HAVE_BYTESWAP_H) + if(HAVE_BYTESWAP_H) + tuklib_add_definitions(${TARGET_OR_ALL} HAVE_BYTESWAP_H) + check_symbol_exists(bswap_16 byteswap.h HAVE_BSWAP_16) + tuklib_add_definition_if(${TARGET_OR_ALL} HAVE_BSWAP_16) + check_symbol_exists(bswap_32 byteswap.h HAVE_BSWAP_32) + tuklib_add_definition_if(${TARGET_OR_ALL} HAVE_BSWAP_32) + check_symbol_exists(bswap_64 byteswap.h HAVE_BSWAP_64) + tuklib_add_definition_if(${TARGET_OR_ALL} HAVE_BSWAP_64) + else() + check_include_file(sys/endian.h HAVE_SYS_ENDIAN_H) + if(HAVE_SYS_ENDIAN_H) + tuklib_add_definitions(${TARGET_OR_ALL} HAVE_SYS_ENDIAN_H) + else() + check_include_file(sys/byteorder.h HAVE_SYS_BYTEORDER_H) + tuklib_add_definition_if(${TARGET_OR_ALL} HAVE_SYS_BYTEORDER_H) + endif() + endif() + endif() + + # 16-bit and 32-bit unaligned access is fast on x86(-64), + # big endian PowerPC, and usually on 32/64-bit ARM too. + # There are others too and ARM could be a false match. + # + # Guess the default value for the option. + # CMake's ability to give info about the target arch seems bad. + # The the same arch can have different name depending on the OS. + # + # FIXME: The regex is based on guessing, not on factual information! + # + # NOTE: Compared to the Autoconf test, this lacks the GCC/Clang test + # on ARM and always assumes that unaligned is fast on ARM. + set(FAST_UNALIGNED_GUESS OFF) + if(CMAKE_SYSTEM_PROCESSOR MATCHES + [Xx3456]86|^[Xx]64|^[Aa][Mm][Dd]64|^[Aa][Rr][Mm]|^aarch|^powerpc|^ppc) + if(NOT WORDS_BIGENDIAN OR + NOT CMAKE_SYSTEM_PROCESSOR MATCHES ^powerpc|^ppc) + set(FAST_UNALIGNED_GUESS ON) + endif() + endif() + option(TUKLIB_FAST_UNALIGNED_ACCESS + "Enable if the system supports *fast* unaligned memory access with 16-bit and 32-bit integers." + ${FAST_UNALIGNED_GUESS}) + tuklib_add_definition_if(${TARGET_OR_ALL} TUKLIB_FAST_UNALIGNED_ACCESS) + + # Unsafe type punning: + option(TUKLIB_USE_UNSAFE_TYPE_PUNNING + "This introduces strict aliasing violations and \ +may result in broken code. However, this might improve performance \ +in some cases, especially with old compilers \ +(e.g. GCC 3 and early 4.x on x86, GCC < 6 on ARMv6 and ARMv7)." + OFF) + tuklib_add_definition_if(${TARGET_OR_ALL} TUKLIB_USE_UNSAFE_TYPE_PUNNING) + + # Check for GCC/Clang __builtin_assume_aligned(). + check_c_source_compiles( + "int main(void) { __builtin_assume_aligned(\"\", 1); return 0; }" + HAVE___BUILTIN_ASSUME_ALIGNED) + tuklib_add_definition_if(${TARGET_OR_ALL} HAVE___BUILTIN_ASSUME_ALIGNED) +endfunction() |