On 4/26/13 3:57 PM, Jeff Davis wrote:
The second patch adds the configure-time check for the right compilation flags, and uses them when compiling checksum.c. I called the new variable CFLAGS_EXTRA, for lack of a better idea, so feel free to come up with a new name. It doesn't check for, or use, -msse4.1, but that can be specified by the user by configuring with CFLAGS_EXTRA="-msse4.1".
Thank you, that is the last piece I was looking at but couldn't nail down on my own. With that I should be able to duplicate both the slicing by 8 CRC speedup Ants sent over (which also expected some optimization changes) and trying something FNV based this weekend.
I think I need to do two baselines: master without checksums, and master with extra optimizations but still without checksums. It may be the case that using better compile time optimizations gives a general speedup that's worth considering regardless. The optimizations seem to have a very significant impact on the checksum feature, but I'd like to quantify how they change the code a little bit before even getting into that.
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