1 files changed, 25 insertions, 4 deletions
diff --git a/src/gallium/auxiliary/util/u_math.h b/src/gallium/auxiliary/util/u_math.h
index b7fc0586f3..b76592d1ec 100644
--- a/src/gallium/auxiliary/util/u_math.h
+++ b/src/gallium/auxiliary/util/u_math.h
@@ -499,11 +499,15 @@ util_bitcount(unsigned n)
 #if defined(PIPE_CC_GCC)
    return __builtin_popcount(n);
 #else
-   /* XXX there are more clever ways of doing this */
+   /* K&R classic bitcount.
+    *
+    * For each iteration, clear the LSB from the bitfield.
+    * Requires only one iteration per set bit, instead of
+    * one iteration per bit less than highest set bit.
+    */
    unsigned bits = 0;
-   while (n) {
-      bits += (n & 1);
-      n = n >> 1;
+   for (bits; n; bits++) {
+      n &= n - 1;
    }
    return bits;
 #endif
@@ -511,6 +515,23 @@ util_bitcount(unsigned n)
 
 
 /**
+ * Reverse byte order of a 32 bit word.
+ */
+static INLINE uint32_t
+util_bswap32(uint32_t n)
+{
+#if defined(PIPE_CC_GCC) && (PIPE_CC_GCC_VERSION >= 403)
+   return __builtin_bswap32(n);
+#else
+   return (n >> 24) |
+          ((n >> 8) & 0x0000ff00) |
+          ((n << 8) & 0x00ff0000) |
+          (n << 24);
+#endif
+}
+
+
+/**
  * Clamp X to [MIN, MAX].
  * This is a macro to allow float, int, uint, etc. types.
  */