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log2_frac optimization from Simon Hosie back in Aug 2011.

--- a/celt/cwrs.c

+++ b/celt/cwrs.c

@@ -48,8 +48,9 @@

   l=EC_ILOG(val);

   if(val&(val-1)){

     /*This is (val>>l-16), but guaranteed to round up, even if adding a bias

-       before the shift would cause overflow (e.g., for 0xFFFFxxxx).*/

-    if(l>16)val=(val>>(l-16))+(((val&((1<<(l-16))-1))+(1<<(l-16))-1)>>(l-16));

+       before the shift would cause overflow (e.g., for 0xFFFFxxxx).

+       Doesn't work for val=0, but that case fails the test above.*/

+    if(l>16)val=((val-1)>>(l-16))+1;

     else val<<=16-l;

     l=(l-1)<<frac;

     /*Note that we always need one iteration, since the rounding up above means