cvs commit: src/sys/sys systm.h
joerg at britannica.bec.de
Wed Feb 14 12:49:38 UTC 2007
On Wed, Feb 14, 2007 at 05:21:23AM +0000, Colin Percival wrote:
> Optimize bitcount32 by replacing 6 logical operations with 2. The key
> observation here is that it doesn't matter what garbage accumulates in
> bits which we're going to end up masking away anyway, as long as the
> garbage doesn't overflow into bits which we care about.
- The version I found uses 0x3f in the last mask.
- You might want to use __builtin_popcount for those GCC versions, which
- I found the table version to be faster on Intel, at least in the hot
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