mirror of https://git.tukaani.org/xz.git
132 lines
3.7 KiB
Plaintext
132 lines
3.7 KiB
Plaintext
#
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# SYNOPSIS
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#
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# TUKLIB_INTEGER
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#
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# DESCRIPTION
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#
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# Checks for tuklib_integer.h:
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# - Endianness
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# - Does the compiler or the operating system provide byte swapping macros
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# - Does the hardware support fast unaligned access to 16-bit
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# and 32-bit integers
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#
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# COPYING
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#
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# Author: Lasse Collin
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#
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# This file has been put into the public domain.
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# You can do whatever you want with this file.
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#
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AC_DEFUN_ONCE([TUKLIB_INTEGER], [
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AC_REQUIRE([TUKLIB_COMMON])
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AC_REQUIRE([AC_C_BIGENDIAN])
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AC_MSG_CHECKING([if __builtin_bswap16/32/64 are supported])
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AC_LINK_IFELSE([AC_LANG_PROGRAM([[]],
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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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[
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AC_DEFINE([HAVE___BUILTIN_BSWAPXX], [1],
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[Define to 1 if the GNU C extensions
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__builtin_bswap16/32/64 are supported.])
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AC_MSG_RESULT([yes])
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], [
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AC_MSG_RESULT([no])
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# Look for other byteswapping methods.
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AC_CHECK_HEADERS([byteswap.h sys/endian.h sys/byteorder.h], [break])
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# Even if we have byteswap.h we may lack the specific macros/functions.
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if test x$ac_cv_header_byteswap_h = xyes ; then
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m4_foreach([FUNC], [bswap_16,bswap_32,bswap_64], [
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AC_MSG_CHECKING([if FUNC is available])
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AC_LINK_IFELSE([AC_LANG_SOURCE([
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#include <byteswap.h>
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int
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main(void)
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{
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FUNC[](42);
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return 0;
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}
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])], [
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AC_DEFINE(HAVE_[]m4_toupper(FUNC), [1],
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[Define to 1 if] FUNC [is available.])
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AC_MSG_RESULT([yes])
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], [AC_MSG_RESULT([no])])
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])dnl
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fi
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])
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AC_MSG_CHECKING([if unaligned memory access should be used])
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AC_ARG_ENABLE([unaligned-access], AS_HELP_STRING([--enable-unaligned-access],
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[Enable if the system supports *fast* unaligned memory access
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with 16-bit and 32-bit integers. By default, this is enabled
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only on x86, x86_64, big endian PowerPC,
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and some ARM systems.]),
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[], [enable_unaligned_access=auto])
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if test "x$enable_unaligned_access" = xauto ; then
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# TODO: There may be other architectures, on which unaligned access
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# is OK.
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case $host_cpu in
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i?86|x86_64|powerpc|powerpc64)
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enable_unaligned_access=yes
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;;
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arm*|aarch64*)
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# On 32-bit and 64-bit ARM, GCC and Clang
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# #define __ARM_FEATURE_UNALIGNED if
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# unaligned access is supported.
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AC_COMPILE_IFELSE([AC_LANG_SOURCE([
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#ifndef __ARM_FEATURE_UNALIGNED
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compile error
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#endif
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int main(void) { return 0; }
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])], [enable_unaligned_access=yes], [enable_unaligned_access=no])
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;;
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*)
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enable_unaligned_access=no
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;;
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esac
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fi
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if test "x$enable_unaligned_access" = xyes ; then
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AC_DEFINE([TUKLIB_FAST_UNALIGNED_ACCESS], [1], [Define to 1 if
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the system supports fast unaligned access to 16-bit and
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32-bit integers.])
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AC_MSG_RESULT([yes])
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else
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AC_MSG_RESULT([no])
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fi
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AC_MSG_CHECKING([if unsafe type punning should be used])
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AC_ARG_ENABLE([unsafe-type-punning],
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AS_HELP_STRING([--enable-unsafe-type-punning],
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[This introduces strict aliasing violations and may result
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in broken code. However, this might improve performance in
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some cases, especially with old compilers (e.g.
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GCC 3 and early 4.x on x86, GCC < 6 on ARMv6 and ARMv7).]),
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[], [enable_unsafe_type_punning=no])
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if test "x$enable_unsafe_type_punning" = xyes ; then
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AC_DEFINE([TUKLIB_USE_UNSAFE_TYPE_PUNNING], [1], [Define to 1 to use
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unsafe type punning, e.g. char *x = ...; *(int *)x = 123;
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which violates strict aliasing rules and thus is
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undefined behavior and might result in broken code.])
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AC_MSG_RESULT([yes])
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else
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AC_MSG_RESULT([no])
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fi
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AC_MSG_CHECKING([if __builtin_assume_aligned is supported])
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AC_LINK_IFELSE([AC_LANG_PROGRAM([[]], [[__builtin_assume_aligned("", 1);]])],
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[
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AC_DEFINE([HAVE___BUILTIN_ASSUME_ALIGNED], [1],
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[Define to 1 if the GNU C extension
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__builtin_assume_aligned is supported.])
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AC_MSG_RESULT([yes])
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], [
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AC_MSG_RESULT([no])
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])
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])dnl
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