[Patch][GCC][middle-end] - Lower store and load neon builtins to gimple

[Richard Biener]

On Wed, 20 Oct 2021, Andre Vieira (lists) wrote:

> On 27/09/2021 12:54, Richard Biener via Gcc-patches wrote:
> > On Mon, 27 Sep 2021, Jirui Wu wrote:
> >
> >> Hi all,
> >>
> >> I now use the type based on the specification of the intrinsic
> >> instead of type based on formal argument.
> >>
> >> I use signed Int vector types because the outputs of the neon builtins
> >> that I am lowering is always signed. In addition, fcode and stmt
> >> does not have information on whether the result is signed.
> >>
> >> Because I am replacing the stmt with new_stmt,
> >> a VIEW_CONVERT_EXPR cast is already in the code if needed.
> >> As a result, the result assembly code is correct.
> >>
> >> Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
> >>
> >> Ok for master? If OK can it be committed for me, I have no commit rights.
> > +           tree temp_lhs = gimple_call_lhs (stmt);
> > +           aarch64_simd_type_info simd_type
> > +             = aarch64_simd_types[mem_type];
> > +           tree elt_ptr_type = build_pointer_type (simd_type.eltype);
> > +           tree zero = build_zero_cst (elt_ptr_type);
> > +           gimple_seq stmts = NULL;
> > +           tree base = gimple_convert (&stmts, elt_ptr_type,
> > +                                       args[0]);
> > +           new_stmt = gimple_build_assign (temp_lhs,
> > +                                    fold_build2 (MEM_REF,
> > +                                    TREE_TYPE (temp_lhs),
> > +                                    base,
> > +                                    zero));
> >
> > this now uses the alignment info as on the LHS of the call by using
> > TREE_TYPE (temp_lhs) as type of the MEM_REF.  So for example
> >
> >   typedef int foo __attribute__((vector_size(N),aligned(256)));
> >
> >   foo tem = ld1 (ptr);
> >
> > will now access *ptr as if it were aligned to 256 bytes.  But I'm sure
> > the ld1 intrinsic documents the required alignment (either it's the
> > natural alignment of the vector type loaded or element alignment?).
> >
> > For element alignment you'd do sth like
> >
> >    tree access_type = build_aligned_type (vector_type, TYPE_ALIGN
> > (TREE_TYPE (vector_type)));
> >
> > for example.
> >
> > Richard.
> Hi,
> 
> I'm taking over this patch from Jirui.
> 
> I've decided to use the vector type stored in aarch64_simd_type_info, since
> that should always have the correct alignment.
> 
> To be fair though, I do wonder whether this is actually needed as is right
> now, since the way we cast the inputs and outputs of these __builtins in
> arm_neon.h prevents these issues I think, but it is more future proof. Also
> you could argue people could use the __builtins directly, though I'd think
> that would be at their own risk.
> 
> Is this OK?

Yes, this variant looks OK.

> Kind regards,
> Andre
>