gallium/util: add util_last_bit64

This will be needed by radeonsi.

Reviewed-by: Ilia Mirkin <[email protected]>

1 files changed, 19 insertions, 0 deletions

diff --git a/src/gallium/auxiliary/util/u_math.h b/src/gallium/auxiliary/util/u_math.h
index 58070a9dafa..3b4040f0ee2 100644
--- a/src/gallium/auxiliary/util/u_math.h
+++ b/src/gallium/auxiliary/util/u_math.h
@@ -425,6 +425,25 @@ util_last_bit(unsigned u)
 }
 
 /**
+ * Find last bit set in a word.  The least significant bit is 1.
+ * Return 0 if no bits are set.
+ */
+static INLINE unsigned
+util_last_bit64(uint64_t u)
+{
+#if defined(HAVE___BUILTIN_CLZLL)
+   return u == 0 ? 0 : 64 - __builtin_clzll(u);
+#else
+   unsigned r = 0;
+   while (u) {
+       r++;
+       u >>= 1;
+   }
+   return r;
+#endif
+}
+
+/**
  * Find last bit in a word that does not match the sign bit. The least
  * significant bit is 1.
  * Return 0 if no bits are set.