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]>

2 files changed, 14 insertions, 2 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:
  *
diff --git a/src/util/u_vector.c b/src/util/u_vector.c
index 0de492ccf9a..bec6e5bbc30 100644
--- a/src/util/u_vector.c
+++ b/src/util/u_vector.c
@@ -37,8 +37,8 @@
 int
 u_vector_init(struct u_vector *vector, uint32_t element_size, uint32_t size)
 {
-   assert(util_is_power_of_two(size));
-   assert(element_size < size && util_is_power_of_two(element_size));
+   assert(util_is_power_of_two_or_zero(size));
+   assert(element_size < size && util_is_power_of_two_or_zero(element_size));
 
    vector->head = 0;
    vector->tail = 0;