https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93767
--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-9 branch has been updated by Richard Sandiford <rsand...@gcc.gnu.org>: https://gcc.gnu.org/g:f9be6e10c96b75307878472567cb0712812a8ab7 commit r9-8272-gf9be6e10c96b75307878472567cb0712812a8ab7 Author: Richard Sandiford <richard.sandif...@arm.com> Date: Tue Feb 18 18:06:32 2020 +0000 vect: Fix offset calculation for -ve strides [PR93767] This PR is a regression caused by r256644, which added support for alias checks involving variable strides. One of the changes in that commit was to split the access size out of the segment length. The PR shows that I hadn't done that correctly for the handling of negative strides in vect_compile_time_alias. The old code was: const_length_a = (-wi::to_poly_wide (segment_length_a)).force_uhwi (); offset_a = (offset_a + vect_get_scalar_dr_size (a)) - const_length_a; where vect_get_scalar_dr_size (a) was cancelling out the subtraction of the access size inherent in "- const_length_a". Taking the access size out of the segment length meant that the addition was no longer needed/correct. 2020-02-24 Richard Sandiford <richard.sandif...@arm.com> gcc/ Backport from mainline 2020-02-19 Richard Sandiford <richard.sandif...@arm.com> PR tree-optimization/93767 * tree-vect-data-refs.c (vect_compile_time_alias): Remove the access-size bias from the offset calculations for negative strides. gcc/testsuite/ Backport from mainline 2020-02-19 Richard Sandiford <richard.sandif...@arm.com> PR tree-optimization/93767 * gcc.dg/vect/pr93767.c: New test.
