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#
# 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()
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