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.
Richard.
> Richard
>
>
> 2019-11-08 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 2019-10-01 09:55:35.062089236 +0100
> +++ gcc/cfgexpand.c 2019-11-08 09:39:13.105130902 +0000
> @@ -6106,6 +6106,20 @@ discover_nonconstant_array_refs_r (tree
> {
> tree t = *tp;
>
> + /* 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. */
> + if (TYPE_SIZE (TREE_TYPE (t))
> + && POLY_INT_CST_P (TYPE_SIZE (TREE_TYPE (t))))
> + {
> + t = get_base_address (t);
> + if (t
> + && DECL_P (t)
> + && DECL_MODE (t) != BLKmode
> + && GET_MODE_BITSIZE (DECL_MODE (t)).is_constant ())
> + TREE_ADDRESSABLE (t) = 1;
> + }
> +
> if (IS_TYPE_OR_DECL_P (t))
> *walk_subtrees = 0;
> else if (TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
> 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 2019-11-08
> 09:39:13.105130902 +0000
> @@ -0,0 +1,13 @@
> +/* { dg-options "-O2" } */
> +
> +#include <arm_sve.h>
> +
> +uint64_t
> +f (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;
> +}
