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;
}
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