From: Damjan Marion <damarion@cisco.com>
Date: Sun, 25 Apr 2021 08:58:07 +0000 (+0200)
Subject: vppinfra: add clear_lowest_set_bit() function, use BMI2 if available
X-Git-Tag: v21.10-rc0~198
X-Git-Url: https://gerrit.fd.io/r/gitweb?a=commitdiff_plain;h=e21a0b26042f615fdbe8d2c6b29612c212079d52;p=vpp.git

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 22377c61440..05af8fe7168 100644
--- 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)
 {