external/public-domain/xz/dist/m4/tuklib_integer.m4

   1 #
   2 # SYNOPSIS
   3 #
   4 #   TUKLIB_INTEGER
   5 #
   6 # DESCRIPTION
   7 #
   8 #   Checks for tuklib_integer.h:
   9 #     - Endianness
  10 #     - Does operating system provide byte swapping macros
  11 #     - Does the hardware support fast unaligned access to 16-bit
  12 #       and 32-bit integers
  13 #
  14 # COPYING
  15 #
  16 #   Author: Lasse Collin
  17 #
  18 #   This file has been put into the public domain.
  19 #   You can do whatever you want with this file.
  20 #
  21
  22 AC_DEFUN_ONCE([TUKLIB_INTEGER], [
  23 AC_REQUIRE([TUKLIB_COMMON])
  24 AC_REQUIRE([AC_C_BIGENDIAN])
  25 AC_CHECK_HEADERS([byteswap.h sys/endian.h sys/byteorder.h], [break])
  26
  27 # Even if we have byteswap.h, we may lack the specific macros/functions.
  28 if test x$ac_cv_header_byteswap_h = xyes ; then
  29         m4_foreach([FUNC], [bswap_16,bswap_32,bswap_64], [
  30                 AC_MSG_CHECKING([if FUNC is available])
  31                 AC_LINK_IFELSE([AC_LANG_SOURCE([
  32 #include <byteswap.h>
  33 int
  34 main(void)
  35 {
  36         FUNC[](42);
  37         return 0;
  38 }
  39                 ])], [
  40                         AC_DEFINE(HAVE_[]m4_toupper(FUNC), [1],
  41                                         [Define to 1 if] FUNC [is available.])
  42                         AC_MSG_RESULT([yes])
  43                 ], [AC_MSG_RESULT([no])])
  44
  45         ])dnl
  46 fi
  47
  48 AC_MSG_CHECKING([if unaligned memory access should be used])
  49 AC_ARG_ENABLE([unaligned-access], AC_HELP_STRING([--enable-unaligned-access],
  50                 [Enable if the system supports *fast* unaligned memory access
  51                 with 16-bit and 32-bit integers. By default, this is enabled
  52                 only on x86, x86_64, and big endian PowerPC.]),
  53         [], [enable_unaligned_access=auto])
  54 if test "x$enable_unaligned_access" = xauto ; then
  55         # TODO: There may be other architectures, on which unaligned access
  56         # is OK.
  57         case $host_cpu in
  58                 i?86|x86_64|powerpc|powerpc64)
  59                         enable_unaligned_access=yes
  60                         ;;
  61                 *)
  62                         enable_unaligned_access=no
  63                         ;;
  64         esac
  65 fi
  66 if test "x$enable_unaligned_access" = xyes ; then
  67         AC_DEFINE([TUKLIB_FAST_UNALIGNED_ACCESS], [1], [Define to 1 if
  68                 the system supports fast unaligned access to 16-bit and
  69                 32-bit integers.])
  70         AC_MSG_RESULT([yes])
  71 else
  72         AC_MSG_RESULT([no])
  73 fi
  74 ])dnl