Andreas Radke wrote:
http://bbs.archlinux.org/viewtopic.php?pid=243370#p243370
"-mtune=cpu-type Tune to cpu-type everything applicable about the generated code, except for the ABI and the set of available instructions."
can somebody explain that a bit more? so mtune=nocona would not enable SSE3 instructions like i expected?
Andy
What -mtune will do is to optimize runtime code to run better in a specific flavor of -march. Meaning, that it will use generic x86_64 instruction set with no SSE3 enabled but more extensively use advantages and work around disadvantages in yourr CPU variant. Such as multi-scalarity and things. -mtune normally doesn't optimize enough to notice any difference, if I were you I wouldn't go as far as to rebuild most of the repo just for the sake of a highly questionable speedup. Generally the -m<instruction set> or -m<arch specifics> give more optimization because they also will go and use extra instructions. Then again, they make the variety of possible CPUs smaller. :) Cheers, -L