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-rw-r--r--m4/ac_have_builtin_expect.m414
1 files changed, 14 insertions, 0 deletions
diff --git a/m4/ac_have_builtin_expect.m4 b/m4/ac_have_builtin_expect.m4
new file mode 100644
index 000000000000..e91b6fd987ed
--- /dev/null
+++ b/m4/ac_have_builtin_expect.m4
@@ -0,0 +1,14 @@
+AC_DEFUN([AX_C___BUILTIN_EXPECT], [
+  AC_MSG_CHECKING(for __builtin_expect)
+  AC_CACHE_VAL(ac_cv___builtin_expect, [
+    AC_TRY_COMPILE(
+      [int foo(void) { if (__builtin_expect(0, 0)) return 1; return 0; }],
+      [],
+      ac_cv___builtin_expect=yes,
+      ac_cv___builtin_expect=no
+    )])
+  if test "$ac_cv___builtin_expect" = "yes"; then
+    AC_DEFINE(HAVE___BUILTIN_EXPECT, 1, [define if your compiler has __builtin_expect])
+  fi
+  AC_MSG_RESULT($ac_cv___builtin_expect)
+])