mesa/main: Add function to find next higher power of two.

[mesa.git] / src / mesa / main / imports.h

diff --git a/src/mesa/main/imports.h b/src/mesa/main/imports.h
index b01fe5b0ab98d55f551b5be93d56114c3bab58c2..81cb396b2bb8fe41443080f8915b0f11744b3e05 100644 (file)
--- a/src/mesa/main/imports.h
+++ b/src/mesa/main/imports.h
@@ -405,6 +405,52 @@ _mesa_is_pow_two(int x)
    return !(x & (x - 1));
 }
 
+/**
+ * Round given integer to next higer power of two
+ * If X is zero result is undefined.
+ *
+ * Source for the fallback implementation is
+ * Sean Eron Anderson's webpage "Bit Twiddling Hacks"
+ * http://graphics.stanford.edu/~seander/bithacks.html
+ */
+static INLINE int32_t
+_mesa_next_pow_two_32(uint32_t x)
+{
+#ifdef __GNUC__
+       return 1 << (__builtin_clz(x) ^ 31);
+#else
+       x--;
+       x |= x >> 1;
+       x |= x >> 2;
+       x |= x >> 4;
+       x |= x >> 8;
+       x |= x >> 16;
+       x++;
+       return x;
+#endif
+}
+
+static INLINE int64_t
+_mesa_next_pow_two_64(uint64_t x)
+{
+#ifdef __GNUC__
+       if (sizeof(x) == sizeof(long))
+               return 1 << (__builtin_clzl(x) ^ 63);
+       else
+               return 1 << (__builtin_clzll(x) ^ 63);
+#else
+       x--;
+       x |= x >> 1;
+       x |= x >> 2;
+       x |= x >> 4;
+       x |= x >> 8;
+       x |= x >> 16;
+       x |= x >> 32;
+       x++;
+       return x;
+#endif
+}
+
 
 /***
  *** UNCLAMPED_FLOAT_TO_UBYTE: clamp float to [0,1] and map to ubyte in [0,255]