vppinfra: add clear_lowest_set_bit() function, use BMI2 if available

Type: improvement
Change-Id: I973cacd0cade0ca98e6261c1fb026a5eb38b44d3
Signed-off-by: Damjan Marion <damarion@cisco.com>

diff --git a/src/vppinfra/clib.h b/src/vppinfra/clib.h
index 22377c6..05af8fe 100644 (file)
--- a/src/vppinfra/clib.h
+++ b/src/vppinfra/clib.h
@@ -158,6 +158,16 @@
 #endif
 
 #if defined (count_leading_zeros)
+always_inline uword
+clear_lowest_set_bit (uword x)
+{
+#ifdef __BMI2__
+  return _blsr_u64 (x);
+#else
+  return x ^ (1ULL << count_trailing_zeros (x));
+#endif
+}
+
 always_inline uword
 min_log2 (uword x)
 {