On Fri, 22 Jan 2021, Jakub Jelinek wrote:
> Hi!
>
> As discussed in the PR, the problem here is that the routines changed in
> this patch sign extend the difference of index and low_bound from the
> precision of the index, so e.g. when index is unsigned int and contains
> value -2U, we treat it as index -2 rather than 0x00000000fffffffeU on 64-bit
> arches.
> On the other hand, get_inner_reference which is used during expansion, does:
> if (! integer_zerop (low_bound))
> index = fold_build2 (MINUS_EXPR, TREE_TYPE (index),
> index, low_bound);
>
> offset = size_binop (PLUS_EXPR, offset,
> size_binop (MULT_EXPR,
> fold_convert (sizetype, index),
> unit_size));
> which effectively requires that either low_bound is constant 0 and then
> index in ARRAY_REFs can be arbitrary type which is then sign or zero
> extended to sizetype, or low_bound is something else and then index and
> low_bound must have compatible types and it is still converted afterwards to
> sizetype and from there then a few lines later:
> expr.c- if (poly_int_tree_p (offset))
> expr.c- {
> expr.c: poly_offset_int tem = wi::sext (wi::to_poly_offset (offset),
> expr.c- TYPE_PRECISION (sizetype));
> The following patch makes those routines match what get_inner_reference is
> doing.
>
> Bootstrapped/regtested on x86_64-linux (as usually, including Ada) and
> i686-linux, ok for trunk?
OK for trunk.
Thanks,
Richard.
> 2021-01-22 Jakub Jelinek <ja...@redhat.com>
>
> PR tree-optimization/98255
> * tree-dfa.c (get_ref_base_and_extent): For ARRAY_REFs, sign
> extend index - low_bound from sizetype's precision rather than index
> precision.
> (get_addr_base_and_unit_offset_1): Likewise.
> * tree-ssa-sccvn.c (ao_ref_init_from_vn_reference): Likewise.
> * gimple-fold.c (fold_const_aggregate_ref_1): Likewise.
>
> * gcc.dg/pr98255.c: New test.
>
> --- gcc/tree-dfa.c.jj 2021-01-04 10:25:37.220252089 +0100
> +++ gcc/tree-dfa.c 2021-01-21 16:43:33.302962080 +0100
> @@ -503,7 +503,7 @@ get_ref_base_and_extent (tree exp, poly_
> poly_offset_int woffset
> = wi::sext (wi::to_poly_offset (index)
> - wi::to_poly_offset (low_bound),
> - TYPE_PRECISION (TREE_TYPE (index)));
> + TYPE_PRECISION (sizetype));
> woffset *= wi::to_offset (unit_size);
> woffset <<= LOG2_BITS_PER_UNIT;
> bit_offset += woffset;
> @@ -564,7 +564,7 @@ get_ref_base_and_extent (tree exp, poly_
> {
> poly_offset_int woffset
> = wi::sext (omin - lbound,
> - TYPE_PRECISION (TREE_TYPE (index)));
> + TYPE_PRECISION (sizetype));
> woffset *= wi::to_offset (unit_size);
> woffset <<= LOG2_BITS_PER_UNIT;
> bit_offset += woffset;
> @@ -822,7 +822,7 @@ get_addr_base_and_unit_offset_1 (tree ex
> poly_offset_int woffset
> = wi::sext (wi::to_poly_offset (index)
> - wi::to_poly_offset (low_bound),
> - TYPE_PRECISION (TREE_TYPE (index)));
> + TYPE_PRECISION (sizetype));
> woffset *= wi::to_offset (unit_size);
> byte_offset += woffset.force_shwi ();
> }
> --- gcc/tree-ssa-sccvn.c.jj 2021-01-13 11:22:30.807345423 +0100
> +++ gcc/tree-ssa-sccvn.c 2021-01-21 16:46:52.780699466 +0100
> @@ -1108,7 +1108,7 @@ ao_ref_init_from_vn_reference (ao_ref *r
> poly_offset_int woffset
> = wi::sext (wi::to_poly_offset (op->op0)
> - wi::to_poly_offset (op->op1),
> - TYPE_PRECISION (TREE_TYPE (op->op0)));
> + TYPE_PRECISION (sizetype));
> woffset *= wi::to_offset (op->op2) * vn_ref_op_align_unit (op);
> woffset <<= LOG2_BITS_PER_UNIT;
> offset += woffset;
> --- gcc/gimple-fold.c.jj 2021-01-05 09:17:24.754566798 +0100
> +++ gcc/gimple-fold.c 2021-01-21 16:45:58.960309941 +0100
> @@ -8007,7 +8007,7 @@ fold_const_aggregate_ref_1 (tree t, tree
> poly_offset_int woffset
> = wi::sext (wi::to_poly_offset (idx)
> - wi::to_poly_offset (low_bound),
> - TYPE_PRECISION (TREE_TYPE (idx)));
> + TYPE_PRECISION (sizetype));
> woffset *= tree_to_uhwi (unit_size);
> woffset *= BITS_PER_UNIT;
> if (woffset.to_shwi (&offset))
> --- gcc/testsuite/gcc.dg/pr98255.c.jj 2021-01-21 16:54:39.258416413 +0100
> +++ gcc/testsuite/gcc.dg/pr98255.c 2021-01-21 16:54:11.531730111 +0100
> @@ -0,0 +1,49 @@
> +/* PR tree-optimization/98255 */
> +/* { dg-do run } */
> +/* { dg-options "-Os" } */
> +/* { dg-additional-options "-fPIC" { target fpic } } */
> +
> +struct A { volatile unsigned b; unsigned c; };
> +int d, *e, h, k, l;
> +static struct A f;
> +long g;
> +static unsigned i = -2U;
> +volatile int j;
> +
> +long
> +foo (void)
> +{
> + char n[4][4][3]
> + = { { {9, 2, 8}, {9, 2, 8}, {9, 2, 8}, {9} }, { {8} }, { {8} }, { {2} }
> };
> + while (d)
> + {
> + for (; f.c < 4; f.c++)
> + {
> + *e = 0;
> + h = n[f.c + 4][0][d];
> + }
> + while (g)
> + return n[0][3][i];
> + while (1)
> + {
> + if (k)
> + {
> + j = 0;
> + if (j)
> + continue;
> + }
> + if (l)
> + break;
> + }
> + }
> + return 0;
> +}
> +
> +int
> +main ()
> +{
> + asm volatile ("" : "+g" (d), "+g" (g), "+g" (f.c));
> + asm volatile ("" : "+g" (e), "+g" (k), "+g" (l));
> + foo ();
> + return 0;
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
