m4/builtin-expect.m4

   1 # builtin-expect.m4
   2 # serial 1
   3 dnl Copyright 2016-2024 Free Software Foundation, Inc.
   4 dnl This file is free software; the Free Software Foundation
   5 dnl gives unlimited permission to copy and/or distribute it,
   6 dnl with or without modifications, as long as this notice is preserved.
   7
   8 dnl Check for __builtin_expect.
   9
  10 dnl Written by Paul Eggert.
  11
  12 AC_DEFUN([gl___BUILTIN_EXPECT],
  13 [
  14   AC_CACHE_CHECK([for __builtin_expect],
  15     [gl_cv___builtin_expect],
  16     [AC_LINK_IFELSE(
  17        [AC_LANG_SOURCE([[
  18          int
  19          main (int argc, char **argv)
  20          {
  21            argc = __builtin_expect (argc, 100);
  22            return argv[argc != 100][0];
  23          }]])],
  24        [gl_cv___builtin_expect=yes],
  25        [AC_LINK_IFELSE(
  26           [AC_LANG_SOURCE([[
  27              #include <builtins.h>
  28              int
  29              main (int argc, char **argv)
  30              {
  31                argc = __builtin_expect (argc, 100);
  32                return argv[argc != 100][0];
  33              }]])],
  34           [gl_cv___builtin_expect="in <builtins.h>"],
  35           [gl_cv___builtin_expect=no])])])
  36   if test "$gl_cv___builtin_expect" = yes; then
  37     AC_DEFINE([HAVE___BUILTIN_EXPECT], [1])
  38   elif test "$gl_cv___builtin_expect" = "in <builtins.h>"; then
  39     AC_DEFINE([HAVE___BUILTIN_EXPECT], [2])
  40   fi
  41   AH_VERBATIM([HAVE___BUILTIN_EXPECT],
  42     [/* Define to 1 if the compiler supports __builtin_expect,
  43    and to 2 if <builtins.h> does.  */
  44 #undef HAVE___BUILTIN_EXPECT
  45 #ifndef HAVE___BUILTIN_EXPECT
  46 # define __builtin_expect(e, c) (e)
  47 #elif HAVE___BUILTIN_EXPECT == 2
  48 # include <builtins.h>
  49 #endif
  50     ])
  51 ])