On Mon, Dec 2, 2019 at 5:30 PM Richard Sandiford
<richard.sandif...@arm.com> wrote:
>
> [finally getting back to this]
>
> Richard Biener <richard.guent...@gmail.com> writes:
> > On Fri, Nov 8, 2019 at 10:40 AM Richard Sandiford
> > <richard.sandif...@arm.com> wrote:
> >>
> >> If SVE code is written for a specific vector length, it might load from
> >> or store to fixed-sized objects. This needs to work even without
> >> -msve-vector-bits=N (which should never be needed for correctness).
> >>
> >> There's no way of handling a direct poly-int sized reference to a
> >> fixed-size register; it would have to go via memory. And in that
> >> case it's more efficient to mark the fixed-size object as
> >> addressable from the outset, like we do for array references
> >> with non-constant indices.
> >>
> >> Tested on aarch64-linux-gnu and x86_64-linux-gnu. OK to install?
> >
> > Hmm, shouldn't you somehow avoid walking subtrees again like
> > the array-ref cases? Do "intermediate" types really matter here?
> > Thus if you have BIT_FIELDREF <VIEW_CONVERT <type-with-poly-size,
> > fixed-size-decl>,
> > select first element > do you really need it addressable?
> >
> > It seems to me you want to check it only on the actual reference type.
>
> Yeah, I guess it was overly general. I don't think it can happen
> for anything other than the MEM_REF/TARGET_MEM_REF itself.
>
> How about this version? Tested as before.
OK.
Thanks,
Richard.
> Richard
>
>
> 2019-12-02 Richard Sandiford <richard.sandif...@arm.com>
>
> gcc/
> * cfgexpand.c (discover_nonconstant_array_refs_r): If an access
> with POLY_INT_CST size is made to a fixed-size object, force the
> object to live in memory.
>
> gcc/testsuite/
> * gcc.target/aarch64/sve/acle/general/deref_1.c: New test.
>
> Index: gcc/cfgexpand.c
> ===================================================================
> --- gcc/cfgexpand.c 2019-11-13 08:42:44.901373255 +0000
> +++ gcc/cfgexpand.c 2019-12-02 16:27:45.157295080 +0000
> @@ -6133,6 +6133,21 @@ discover_nonconstant_array_refs_r (tree
>
> *walk_subtrees = 0;
> }
> + /* References of size POLY_INT_CST to a fixed-size object must go
> + through memory. It's more efficient to force that here than
> + to create temporary slots on the fly. */
> + else if ((TREE_CODE (t) == MEM_REF || TREE_CODE (t) == TARGET_MEM_REF)
> + && TYPE_SIZE (TREE_TYPE (t))
> + && POLY_INT_CST_P (TYPE_SIZE (TREE_TYPE (t))))
> + {
> + tree base = get_base_address (t);
> + if (base
> + && DECL_P (base)
> + && DECL_MODE (base) != BLKmode
> + && GET_MODE_SIZE (DECL_MODE (base)).is_constant ())
> + TREE_ADDRESSABLE (base) = 1;
> + *walk_subtrees = 0;
> + }
>
> return NULL_TREE;
> }
> Index: gcc/testsuite/gcc.target/aarch64/sve/acle/general/deref_1.c
> ===================================================================
> --- /dev/null 2019-09-17 11:41:18.176664108 +0100
> +++ gcc/testsuite/gcc.target/aarch64/sve/acle/general/deref_1.c 2019-12-02
> 16:27:45.165295026 +0000
> @@ -0,0 +1,25 @@
> +/* { dg-options "-O2" } */
> +
> +#include <arm_sve.h>
> +
> +uint64_t
> +f1 (int32_t *x, int32_t *y)
> +{
> + union { uint64_t x; char c[8]; } u;
> + svbool_t pg = svptrue_b32 ();
> + *(svbool_t *)&u.c[0] = svcmpeq (pg, svld1 (pg, x), 0);
> + *(svbool_t *)&u.c[4] = svcmpeq (pg, svld1 (pg, y), 1);
> + return u.x;
> +}
> +
> +typedef unsigned int v4si __attribute__((vector_size(16)));
> +
> +/* The aliasing is somewhat dubious here, but it must compile. */
> +
> +v4si
> +f2 (void)
> +{
> + v4si res;
> + *(svuint32_t *) &res = svindex_u32 (0, 1);
> + return res;
> +}
