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Diffstat (limited to 'm4/tuklib_integer.m4')
| -rw-r--r-- | m4/tuklib_integer.m4 | 131 |
1 files changed, 131 insertions, 0 deletions
diff --git a/m4/tuklib_integer.m4 b/m4/tuklib_integer.m4 new file mode 100644 index 0000000..9e10472 --- /dev/null +++ b/m4/tuklib_integer.m4 @@ -0,0 +1,131 @@ +# +# SYNOPSIS +# +# TUKLIB_INTEGER +# +# DESCRIPTION +# +# Checks for tuklib_integer.h: +# - Endianness +# - Does the compiler or the operating system provide byte swapping macros +# - Does the hardware support fast unaligned access to 16-bit +# and 32-bit integers +# +# COPYING +# +# Author: Lasse Collin +# +# This file has been put into the public domain. +# You can do whatever you want with this file. +# + +AC_DEFUN_ONCE([TUKLIB_INTEGER], [ +AC_REQUIRE([TUKLIB_COMMON]) +AC_REQUIRE([AC_C_BIGENDIAN]) + +AC_MSG_CHECKING([if __builtin_bswap16/32/64 are supported]) +AC_LINK_IFELSE([AC_LANG_PROGRAM([[]], + [[__builtin_bswap16(1); + __builtin_bswap32(1); + __builtin_bswap64(1);]])], +[ + AC_DEFINE([HAVE___BUILTIN_BSWAPXX], [1], + [Define to 1 if the GNU C extensions + __builtin_bswap16/32/64 are supported.]) + AC_MSG_RESULT([yes]) +], [ + AC_MSG_RESULT([no]) + + # Look for other byteswapping methods. + AC_CHECK_HEADERS([byteswap.h sys/endian.h sys/byteorder.h], [break]) + + # Even if we have byteswap.h we may lack the specific macros/functions. + if test x$ac_cv_header_byteswap_h = xyes ; then + m4_foreach([FUNC], [bswap_16,bswap_32,bswap_64], [ + AC_MSG_CHECKING([if FUNC is available]) + AC_LINK_IFELSE([AC_LANG_SOURCE([ +#include <byteswap.h> +int +main(void) +{ + FUNC[](42); + return 0; +} + ])], [ + AC_DEFINE(HAVE_[]m4_toupper(FUNC), [1], + [Define to 1 if] FUNC [is available.]) + AC_MSG_RESULT([yes]) + ], [AC_MSG_RESULT([no])]) + + ])dnl + fi +]) + +AC_MSG_CHECKING([if unaligned memory access should be used]) +AC_ARG_ENABLE([unaligned-access], AS_HELP_STRING([--enable-unaligned-access], + [Enable if the system supports *fast* unaligned memory access + with 16-bit, 32-bit, and 64-bit integers. By default, + this is enabled only on x86, x86_64, big endian PowerPC, + and some ARM systems.]), + [], [enable_unaligned_access=auto]) +if test "x$enable_unaligned_access" = xauto ; then + # TODO: There may be other architectures, on which unaligned access + # is OK. + case $host_cpu in + i?86|x86_64|powerpc|powerpc64) + enable_unaligned_access=yes + ;; + arm*|aarch64*) + # On 32-bit and 64-bit ARM, GCC and Clang + # #define __ARM_FEATURE_UNALIGNED if + # unaligned access is supported. + AC_COMPILE_IFELSE([AC_LANG_SOURCE([ +#ifndef __ARM_FEATURE_UNALIGNED +compile error +#endif +int main(void) { return 0; } +])], [enable_unaligned_access=yes], [enable_unaligned_access=no]) + ;; + *) + enable_unaligned_access=no + ;; + esac +fi +if test "x$enable_unaligned_access" = xyes ; then + AC_DEFINE([TUKLIB_FAST_UNALIGNED_ACCESS], [1], [Define to 1 if + the system supports fast unaligned access to 16-bit, + 32-bit, and 64-bit integers.]) + AC_MSG_RESULT([yes]) +else + AC_MSG_RESULT([no]) +fi + +AC_MSG_CHECKING([if unsafe type punning should be used]) +AC_ARG_ENABLE([unsafe-type-punning], + AS_HELP_STRING([--enable-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).]), + [], [enable_unsafe_type_punning=no]) +if test "x$enable_unsafe_type_punning" = xyes ; then + AC_DEFINE([TUKLIB_USE_UNSAFE_TYPE_PUNNING], [1], [Define to 1 to use + unsafe type punning, e.g. char *x = ...; *(int *)x = 123; + which violates strict aliasing rules and thus is + undefined behavior and might result in broken code.]) + AC_MSG_RESULT([yes]) +else + AC_MSG_RESULT([no]) +fi + +AC_MSG_CHECKING([if __builtin_assume_aligned is supported]) +AC_LINK_IFELSE([AC_LANG_PROGRAM([[]], [[__builtin_assume_aligned("", 1);]])], + [ + AC_DEFINE([HAVE___BUILTIN_ASSUME_ALIGNED], [1], + [Define to 1 if the GNU C extension + __builtin_assume_aligned is supported.]) + AC_MSG_RESULT([yes]) + ], [ + AC_MSG_RESULT([no]) + ]) +])dnl |