util: Helper to create sets and hashes with pointer keys

[mesa.git] / src / util / bitscan.h

diff --git a/src/util/bitscan.h b/src/util/bitscan.h
index 7a605e0370fe6f2b42374ca32f47fa073cd1295c..dc89ac93f28b08eed85d54d2aba4484609bc5d50 100644 (file)
--- a/src/util/bitscan.h
+++ b/src/util/bitscan.h
@@ -31,12 +31,17 @@
 
 #include <assert.h>
 #include <stdint.h>
+#include <stdbool.h>
 #include <string.h>
 
 #if defined(_MSC_VER)
 #include <intrin.h>
 #endif
 
+#if defined(__POPCNT__)
+#include <popcntintrin.h>
+#endif
+
 #include "c99_compat.h"
 
 #ifdef __cplusplus
@@ -107,6 +112,52 @@ 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;
+}
+
+/* Determine if an uint64_t value is a power of two.
+ *
+ * \note
+ * Zero is treated as a power of two.
+ */
+static inline bool
+util_is_power_of_two_or_zero64(uint64_t v)
+{
+   return (v & (v - 1)) == 0;
+}
+
+/* Determine if an unsigned value is a power of two.
+ *
+ * \note
+ * Zero is \b not treated as a power of two.
+ */
+static inline bool
+util_is_power_of_two_nonzero(unsigned v)
+{
+   /* __POPCNT__ is different from HAVE___BUILTIN_POPCOUNT.  The latter
+    * indicates the existence of the __builtin_popcount function.  The former
+    * indicates that _mm_popcnt_u32 exists and is a native instruction.
+    *
+    * The other alternative is to use SSE 4.2 compile-time flags.  This has
+    * two drawbacks.  First, there is currently no build infrastructure for
+    * SSE 4.2 (only 4.1), so that would have to be added.  Second, some AMD
+    * CPUs support POPCNT but not SSE 4.2 (e.g., Barcelona).
+    */
+#ifdef __POPCNT__
+   return _mm_popcnt_u32(v) == 1;
+#else
+   return v != 0 && (v & (v - 1)) == 0;
+#endif
+}
+
 /* For looping over a bitmask when you want to loop over consecutive bits
  * manually, for example:
  *
@@ -136,7 +187,7 @@ u_bit_scan_consecutive_range(unsigned *mask, int *start, int *count)
 static inline void
 u_bit_scan_consecutive_range64(uint64_t *mask, int *start, int *count)
 {
-   if (*mask == ~0llu) {
+   if (*mask == ~0ull) {
       *start = 0;
       *count = 64;
       *mask = 0;