m4/labels-as-values.m4

   1 dnl check for gcc's "labels as values" feature
   2 AC_DEFUN([AC_C_LABELS_AS_VALUES],
   3 [AC_CACHE_CHECK([labels as values], ac_cv_labels_as_values,
   4 [AC_TRY_COMPILE([
   5 int foo(int);
   6 int foo(i)
   7 int i; {
   8 static void *label[] = { &&l1, &&l2 };
   9 goto *label[i];
  10 l1: return 1;
  11 l2: return 2;
  12 }
  13 ],
  14 [int i;],
  15 ac_cv_labels_as_values=yes,
  16 ac_cv_labels_as_values=no)])
  17 if test "$ac_cv_labels_as_values" = yes; then
  18 AC_DEFINE([HAVE_LABELS_AS_VALUES], [],
  19           [Define if compiler supports gcc's "labels as values" (aka computed goto)
  20            feature, used to speed up instruction dispatch in the interpreter.])
  21 fi
  22 ])