https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98255
--- Comment #14 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:e287a2a11d7958e5d9f7c6172e59cc83495e393a commit r11-6852-ge287a2a11d7958e5d9f7c6172e59cc83495e393a Author: Jakub Jelinek <ja...@redhat.com> Date: Fri Jan 22 11:42:03 2021 +0100 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 <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.
