on ARRAY_REFs sign-extend offsets only from sizetype's precision [PR98255]
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. 2021-01-22 Jakub Jelinek <jakub@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.
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@ -8007,7 +8007,7 @@ fold_const_aggregate_ref_1 (tree t, tree (*valueize) (tree))
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poly_offset_int woffset
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= wi::sext (wi::to_poly_offset (idx)
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- wi::to_poly_offset (low_bound),
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TYPE_PRECISION (TREE_TYPE (idx)));
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TYPE_PRECISION (sizetype));
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woffset *= tree_to_uhwi (unit_size);
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woffset *= BITS_PER_UNIT;
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if (woffset.to_shwi (&offset))
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@ -0,0 +1,49 @@
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/* PR tree-optimization/98255 */
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/* { dg-do run } */
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/* { dg-options "-Os" } */
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/* { dg-additional-options "-fPIC" { target fpic } } */
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struct A { volatile unsigned b; unsigned c; };
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int d, *e, h, k, l;
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static struct A f;
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long g;
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static unsigned i = -2U;
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volatile int j;
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long
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foo (void)
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{
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char n[4][4][3]
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= { { {9, 2, 8}, {9, 2, 8}, {9, 2, 8}, {9} }, { {8} }, { {8} }, { {2} } };
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while (d)
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{
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for (; f.c < 4; f.c++)
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{
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*e = 0;
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h = n[f.c + 4][0][d];
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}
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while (g)
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return n[0][3][i];
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while (1)
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{
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if (k)
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{
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j = 0;
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if (j)
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continue;
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}
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if (l)
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break;
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}
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}
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return 0;
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}
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int
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main ()
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{
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asm volatile ("" : "+g" (d), "+g" (g), "+g" (f.c));
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asm volatile ("" : "+g" (e), "+g" (k), "+g" (l));
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foo ();
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return 0;
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}
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@ -503,7 +503,7 @@ get_ref_base_and_extent (tree exp, poly_int64_pod *poffset,
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poly_offset_int woffset
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= wi::sext (wi::to_poly_offset (index)
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- wi::to_poly_offset (low_bound),
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TYPE_PRECISION (TREE_TYPE (index)));
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TYPE_PRECISION (sizetype));
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woffset *= wi::to_offset (unit_size);
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woffset <<= LOG2_BITS_PER_UNIT;
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bit_offset += woffset;
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@ -564,7 +564,7 @@ get_ref_base_and_extent (tree exp, poly_int64_pod *poffset,
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{
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poly_offset_int woffset
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= wi::sext (omin - lbound,
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TYPE_PRECISION (TREE_TYPE (index)));
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TYPE_PRECISION (sizetype));
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woffset *= wi::to_offset (unit_size);
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woffset <<= LOG2_BITS_PER_UNIT;
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bit_offset += woffset;
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@ -822,7 +822,7 @@ get_addr_base_and_unit_offset_1 (tree exp, poly_int64_pod *poffset,
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poly_offset_int woffset
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= wi::sext (wi::to_poly_offset (index)
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- wi::to_poly_offset (low_bound),
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TYPE_PRECISION (TREE_TYPE (index)));
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TYPE_PRECISION (sizetype));
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woffset *= wi::to_offset (unit_size);
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byte_offset += woffset.force_shwi ();
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}
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@ -1108,7 +1108,7 @@ ao_ref_init_from_vn_reference (ao_ref *ref,
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poly_offset_int woffset
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= wi::sext (wi::to_poly_offset (op->op0)
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- wi::to_poly_offset (op->op1),
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TYPE_PRECISION (TREE_TYPE (op->op0)));
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TYPE_PRECISION (sizetype));
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woffset *= wi::to_offset (op->op2) * vn_ref_op_align_unit (op);
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woffset <<= LOG2_BITS_PER_UNIT;
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offset += woffset;
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