On Mon, Mar 31, 2025 at 9:36 AM Kyrylo Tkachov <ktkac...@nvidia.com> wrote:
>
> Ping.
Can you reference the patch please? I'll note your mails have the tendency to
end up in my spam folder (which is auto-purged after some time). Probably
a setup issue at nvidias side.
Richard.
> Thanks,
> Kyrill
>
> > On 24 Mar 2025, at 14:28, Kyrylo Tkachov <ktkac...@nvidia.com> wrote:
> >
> > Hi all,
> >
> > In this testcase GCC tries to expand a VNx4BI vector:
> > vector(4) <signed-boolean:4> _40;
> > _39 = (<signed-boolean:4>) _24;
> > _40 = {_39, _39, _39, _39};
> >
> > This ends up in a scalarised sequence of bitfield insert operations.
> > This is despite the fact that AArch64 provides a vec_duplicate pattern
> > specifically for vec_duplicate into VNx4BI.
> >
> > The store_constructor code is overly conservative when trying vec_duplicate
> > as it sees a requested VNx4BImode and an element mode of QImode, which I
> > guess
> > is the storage mode of BImode objects.
> >
> > The vec_duplicate expander in aarch64-sve.md explicitly allows QImode
> > element
> > modes so it should be safe to use it. This patch extends that mode check
> > to allow such expanders.
> >
> > The testcase is heavily auto-reduced from a real application but in itself
> > is
> > nonsensical, but it does demonstrate the current problematic codegen.
> >
> > This the testcase goes from:
> > pfalse p15.b
> > str p15, [sp, #6, mul vl]
> > mov w0, 0
> > ldr w2, [sp, 12]
> > bfi w2, w0, 0, 4
> > uxtw x2, w2
> > bfi w2, w0, 4, 4
> > uxtw x2, w2
> > bfi w2, w0, 8, 4
> > uxtw x2, w2
> > bfi w2, w0, 12, 4
> > str w2, [sp, 12]
> > ldr p15, [sp, #6, mul vl]
> >
> > into:
> > whilelo p15.s, wzr, wzr
> >
> > The whilelo could be optimised away into a pfalse of course, but the
> > important
> > part is that the bfis are gone.
> >
> > Bootstrapped and tested on aarch64-none-linux-gnu.
> >
> > Given this a regression from GCC 13 is this ok for trunk now?
> > Thanks,
> > Kyrill
> >
> > Signed-off-by: Kyrylo Tkachov <ktkac...@nvidia.com>
> >
> > gcc/
> >
> > PR middle-end/119442
> > * expr.cc (store_constructor): Also allow element modes explicitly
> > accepted by target vec_duplicate pattern.
> >
> > gcc/testsuite/
> >
> > PR middle-end/119442
> > * gcc.target/aarch64/vls_sve_vec_dup_1.c: New test.
> >
> > <0001-PR-middle-end-119442-expr.cc-Fix-vec_duplicate-into-.patch>
>
