performance - How can I get my CPU's branch target buffer(BTB) size? -


it's useful when execute routine when loops > btb_size, eg,

from

int n = 0; (int = 0; < loops; i++)     n++;

to 

int n = 0; int loops = loops / 2; for(int = 0; < loops; i+=2)     n += 2;

can reduce branch misses.

btb ref:http://www-ee.eng.hawaii.edu/~tep/ee461/notes/ilp/buffer.html doesn't tell how btb size.

any modern compiler worth salt should optimise code int n = loops;, in more complex example, compiler take care of such optimisation; see llvm's auto-vectorisation, instance, handles many kinds of loop unrolling. rather trying optimise code, find appropriate compiler flags compiler hard work.


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