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-rw-r--r--mesalib/src/mesa/main/teximage.c35
1 files changed, 11 insertions, 24 deletions
diff --git a/mesalib/src/mesa/main/teximage.c b/mesalib/src/mesa/main/teximage.c
index cf8a1d486..fa9783892 100644
--- a/mesalib/src/mesa/main/teximage.c
+++ b/mesalib/src/mesa/main/teximage.c
@@ -81,31 +81,18 @@ _mesa_free_texmemory(void *m)
/*
- * Compute floor(log_base_2(n)).
- * If n < 0 return -1.
+ * Returns the floor form of binary logarithm for a 32-bit integer.
*/
-static int
-logbase2( int n )
-{
- GLint i = 1;
- GLint log2 = 0;
-
- if (n < 0)
- return -1;
-
- if (n == 0)
- return 0;
-
- while ( n > i ) {
- i *= 2;
- log2++;
- }
- if (i != n) {
- return log2 - 1;
- }
- else {
- return log2;
- }
+static GLuint
+logbase2(GLuint n)
+{
+ GLuint pos = 0;
+ if (n >= 1<<16) { n >>= 16; pos += 16; }
+ if (n >= 1<< 8) { n >>= 8; pos += 8; }
+ if (n >= 1<< 4) { n >>= 4; pos += 4; }
+ if (n >= 1<< 2) { n >>= 2; pos += 2; }
+ if (n >= 1<< 1) { pos += 1; }
+ return pos;
}