[1/3] configure.in: check that compiler supports __builtin_expect()

Commit Message

Yevgeny Kliteynik July 22, 2012, 10:46 a.m. UTC

Signed-off-by: Yevgeny Kliteynik <[e-mail]>
---
 configure.in | 11 +++++++++++
 1 file changed, 11 insertions(+)

Patch

diff --git a/configure.in b/configure.in
index b2d07bc..0a56da6 100644
--- a/configure.in
+++ b/configure.in
@@ -56,6 +56,17 @@  AC_HEADER_TIME
 AC_STRUCT_TM
 AC_C_VOLATILE

+dnl See if we have __builtin_expect
+AC_MSG_CHECKING([if the compiler supports __builtin_expect])
+AC_TRY_COMPILE(, [ return __builtin_expect(1, 1) ? 1 : 0],
+		 [ have_builtin_expect=yes
+		   AC_MSG_RESULT([yes]) ],
+		 [ have_builtin_expect=no
+		   AC_MSG_RESULT([no])  ])
+if test "x_$have_builtin_expect" = "x_yes" ; then
+	AC_DEFINE([HAVE_BUILTIN_EXPECT], [1], [Define to 1 if the compiler supports __builtin_expect.])
+fi
+
 dnl We use --version-script with ld if possible
 AC_CACHE_CHECK(whether ld accepts --version-script, ac_cv_version_script,
 if test -n "`$LD --help < /dev/null 2>/dev/null | grep version-script`"; then