Mesa (gallium-0.2): util: Optimise log2().

[Keith Whitwell]

Module: Mesa
Branch: gallium-0.2
Commit: 0d8637451b7bf1aac164dba6d269d1a665160ea3
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=0d8637451b7bf1aac164dba6d269d1a665160ea3

Author: Michal Krol <michal at tungstengraphics.com>
Date:   Wed Nov 12 19:02:41 2008 +0100

util: Optimise log2().

---

 src/gallium/auxiliary/util/u_math.h |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/src/gallium/auxiliary/util/u_math.h b/src/gallium/auxiliary/util/u_math.h
index c7bbebc..aee69ab 100644
--- a/src/gallium/auxiliary/util/u_math.h
+++ b/src/gallium/auxiliary/util/u_math.h
@@ -163,7 +163,8 @@ static INLINE float logf( float f )
 
 static INLINE double log2( double x )
 {
-   return log( x ) / log( 2.0 );
+   const double invln2 = 1.442695041;
+   return log( x ) * invln2;
 }
 
 #else