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142 lines
5.6 KiB
CMake
142 lines
5.6 KiB
CMake
# SPDX-License-Identifier: 0BSD
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#############################################################################
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#
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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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#############################################################################
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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("${TARGET_OR_ALL}"
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HAVE_SYS_BYTEORDER_H)
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endif()
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endif()
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endif()
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# Guess that unaligned access is fast on these archs:
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# - 32/64-bit x86 / x86-64
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# - 32/64-bit big endian PowerPC
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# - 64-bit little endian PowerPC
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# - Some 32-bit ARM
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# - Some 64-bit ARM64 (AArch64)
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# - Some 32/64-bit RISC-V
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#
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# CMake doesn't provide a standardized/normalized list of processor arch
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# names. For example, x86-64 may be "x86_64" (Linux), "AMD64" (Windows),
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# or even "EM64T" (64-bit WinXP).
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set(FAST_UNALIGNED_GUESS OFF)
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string(TOLOWER "${CMAKE_SYSTEM_PROCESSOR}" PROCESSOR)
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# There is no ^ in the first regex branch to allow "i" at the beginning
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# so it can match "i386" to "i786", and "x86_64".
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if(PROCESSOR MATCHES "[x34567]86|^x64|^amd64|^em64t")
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set(FAST_UNALIGNED_GUESS ON)
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elseif(PROCESSOR MATCHES "^powerpc|^ppc")
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if(WORDS_BIGENDIAN OR PROCESSOR MATCHES "64")
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set(FAST_UNALIGNED_GUESS ON)
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endif()
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elseif(PROCESSOR MATCHES "^arm|^aarch64|^riscv")
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# On 32-bit and 64-bit ARM, GCC and Clang
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# #define __ARM_FEATURE_UNALIGNED if
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# unaligned access is supported.
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#
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# Exception: GCC at least up to 13.2.0
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# defines it even when using -mstrict-align
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# so in that case this autodetection goes wrong.
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# Most of the time -mstrict-align isn't used so it
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# shouldn't be a common problem in practice. See:
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# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111555
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#
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# RISC-V C API Specification says that if
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# __riscv_misaligned_fast is defined then
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# unaligned access is known to be fast.
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#
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# MSVC is handled as a special case: We assume that
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# 32/64-bit ARM supports fast unaligned access.
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# If MSVC gets RISC-V support then this will assume
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# fast unaligned access on RISC-V too.
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check_c_source_compiles("
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#if !defined(__ARM_FEATURE_UNALIGNED) \
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&& !defined(__riscv_misaligned_fast) \
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&& !defined(_MSC_VER)
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compile error
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#endif
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int main(void) { return 0; }
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"
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TUKLIB_FAST_UNALIGNED_DEFINED_BY_PREPROCESSOR)
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if(TUKLIB_FAST_UNALIGNED_DEFINED_BY_PREPROCESSOR)
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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, 32-bit, and 64-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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