vppinfra: add CLIB_ASSUME() macro
This macro privides a way to tell compiler that it is safe to assume
that specified expression is true so it can optimize code accordingly.
i.e.
CLIB_ASSUME (n < 3);
while (n)
{
/* ... */
}
Will tell compiler that n is never going to be >= 3 so instead of
creating loop it will just unroll loop 2 times.
Type: improvement
Change-Id: I718a9b95ff7980d7ac68eb9a88357a4ab6eee74a
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vppinfra/clib.h b/src/vppinfra/clib.h
index 81b59e2..52e7217 100644
--- a/src/vppinfra/clib.h
+++ b/src/vppinfra/clib.h
@@ -124,6 +124,13 @@
#define PREDICT_FALSE(x) __builtin_expect((x),0)
#define PREDICT_TRUE(x) __builtin_expect((x),1)
#define COMPILE_TIME_CONST(x) __builtin_constant_p (x)
+#define CLIB_ASSUME(x) \
+ do \
+ { \
+ if (!(x)) \
+ __builtin_unreachable (); \
+ } \
+ while (0)
/*
* Compiler barrier