> Currently unaligned YMM and ZMM load and store costs are cheaper than
> aligned which causes the vectorizer to purposely mis-align accesses
> by adding an alignment prologue. It looks like the unaligned costs
> were simply left untouched from znver3 where they equate the aligned
> costs when tweaking aligned costs for znver4. The following makes
> the unaligned costs equal to the aligned costs.
>
> This avoids the miscompile seen in PR115843 but it's of course not
> a real fix for the issue uncovered there. But it makes it qualify
> as a regression fix.
>
> Bootstrap & regtest running on x86_64-unknown-linux-gnu.
>
> OK for trunk and affected branches? It also affects the gcc11 branch
Looks good to me. I think it was my omission. I should remmeber that
the costs are there multiple times.
Maybe wait for SPEC tester before backporting to branches?
Honza
> where znver4 support/costs are new for 11.5 and thus it affects the
> release candidate. The alternative option is to revert the zen4
> backports or leave the costs broken.
>
> Thanks,
> Richard.
>
> PR tree-optimization/115843
> * config/i386/x86-tune-costs.h (znver4_cost): Update unaligned
> load and store cost from the aligned costs.
> ---
> gcc/config/i386/x86-tune-costs.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/gcc/config/i386/x86-tune-costs.h
> b/gcc/config/i386/x86-tune-costs.h
> index a933794ed50..2ac75c35aee 100644
> --- a/gcc/config/i386/x86-tune-costs.h
> +++ b/gcc/config/i386/x86-tune-costs.h
> @@ -1924,8 +1924,8 @@ struct processor_costs znver4_cost = {
> in 32bit, 64bit, 128bit, 256bit and
> 512bit */
> {8, 8, 8, 12, 12}, /* cost of storing SSE register
> in 32bit, 64bit, 128bit, 256bit and
> 512bit */
> - {6, 6, 6, 6, 6}, /* cost of unaligned loads. */
> - {8, 8, 8, 8, 8}, /* cost of unaligned stores. */
> + {6, 6, 10, 10, 12}, /* cost of unaligned loads. */
> + {8, 8, 8, 12, 12}, /* cost of unaligned stores. */
> 2, 2, 2, /* cost of moving XMM,YMM,ZMM
> register. */
> 6, /* cost of moving SSE register to
> integer. */
> --
> 2.35.3
