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-rw-r--r--mesalib/src/mesa/main/imports.h21
1 files changed, 21 insertions, 0 deletions
diff --git a/mesalib/src/mesa/main/imports.h b/mesalib/src/mesa/main/imports.h
index ce7baabe2..3fa1db02a 100644
--- a/mesalib/src/mesa/main/imports.h
+++ b/mesalib/src/mesa/main/imports.h
@@ -486,6 +486,27 @@ _mesa_next_pow_two_64(uint64_t x)
}
+/*
+ * Returns the floor form of binary logarithm for a 32-bit integer.
+ */
+static INLINE GLuint
+_mesa_logbase2(GLuint n)
+{
+#if defined(__GNUC__) && \
+ ((__GNUC__ == 3 && __GNUC_MINOR__ >= 4) || __GNUC__ >= 4)
+ return (31 - __builtin_clz(n | 1));
+#else
+ 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;
+#endif
+}
+
+
/**
* Return 1 if this is a little endian machine, 0 if big endian.
*/