diff options
Diffstat (limited to 'm4/tuklib_integer.m4')
| -rw-r--r-- | m4/tuklib_integer.m4 | 46 |
1 files changed, 45 insertions, 1 deletions
diff --git a/m4/tuklib_integer.m4 b/m4/tuklib_integer.m4 index c3c59fe3..dcc83d92 100644 --- a/m4/tuklib_integer.m4 +++ b/m4/tuklib_integer.m4 @@ -45,11 +45,26 @@ main(void) ])dnl fi +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]) + ]) + 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 and 32-bit integers. By default, this is enabled - only on x86, x86_64, and big endian PowerPC.]), + only on x86, x86_64, big endian PowerPC, + and some ARM systems.]), [], [enable_unaligned_access=auto]) if test "x$enable_unaligned_access" = xauto ; then # TODO: There may be other architectures, on which unaligned access @@ -82,4 +97,33 @@ if test "x$enable_unaligned_access" = xyes ; then 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 |