util: Move util_is_power_of_two to bitscan.h and rename to util_is_power_of_two_or_zero

The new name make the zero-input behavior more obvious.  The next
patch adds a new function with different zero-input behavior.

Signed-off-by: Ian Romanick <[email protected]>
Suggested-by: Matt Turner <[email protected]>
Reviewed-by: Alejandro Piñeiro <[email protected]>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/util/bitscan.h b/src/util/bitscan.h
index 611e8120596..2d4e46ec0f1 100644
--- a/src/util/bitscan.h
+++ b/src/util/bitscan.h
@@ -31,6 +31,7 @@
 
 #include <assert.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <string.h>
 
 #if defined(_MSC_VER)
@@ -107,6 +108,17 @@ u_bit_scan64(uint64_t *mask)
    return i;
 }
 
+/* Determine if an unsigned value is a power of two.
+ *
+ * \note
+ * Zero is treated as a power of two.
+ */
+static inline bool
+util_is_power_of_two_or_zero(unsigned v)
+{
+   return (v & (v - 1)) == 0;
+}
+
 /* For looping over a bitmask when you want to loop over consecutive bits
  * manually, for example:
  *