https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88760
--- Comment #39 from Jiu Fu Guo <guojiufu at gcc dot gnu.org> --- For small loop (1-2 stmts), in forms of GIMPLE and RTL, it would be around 5-10 instructions: 2-4 insns per stmt, ~4 insns for idx. With current unroller, here is a statistic on spec2017. Using --param max-unrolled-insns=12, there are ~3000 small loops could be unrolled totally, and ~40 of these small loops are located in hot-functions. Using --param max-unrolled-insns=16, there are ~11000 small loops could be unrolled totally, and ~230 of these small loops are located in hot-functions. Using --param max-unrolled-insns=20, there are ~15000 small loops could be unrolled totally, and ~570 of these small loops are located in hot-functions. Using --param max-unrolled-insns=24, there are ~18000 small loops could be unrolled totally, and ~680 of these small loops are located in hot-functions. if max-unrolled-insns<16, just few small loops are unrolled for hot-functions; it may be not very valuable.
