https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92448
--- Comment #2 from rguenther at suse dot de <rguenther at suse dot de> --- On November 11, 2019 10:20:10 AM GMT+01:00, crazylht at gmail dot com <gcc-bugzi...@gcc.gnu.org> wrote: >https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92448 > >--- Comment #1 from Hongtao.liu <crazylht at gmail dot com> --- >Also with TARGET_AVX128_OPTIMAL plus -mprefer-vector-width=256, 256-bit >vectorization may be not generated since TARGET_AVX128_OPTIMAL will >change >vec_cost. > >-------------------------------------------- >/* Return cost of vector operation in MODE given that scalar version >has > COST. */ > >static int >ix86_vec_cost (machine_mode mode, int cost) >{ > if (!VECTOR_MODE_P (mode)) > return cost; > > if (GET_MODE_BITSIZE (mode) == 128 > && TARGET_SSE_SPLIT_REGS) > return cost * 2; > if (GET_MODE_BITSIZE (mode) > 128 > && TARGET_AVX128_OPTIMAL) > return cost * GET_MODE_BITSIZE (mode) / 128; > return cost; >} >----------------------------------------- But this is because 128 optimal really means 256 bit ops are split into two 128 bit ones. The tuning is possibly poorly named. Richard.
