From f91aa3e6cb808f8dfc6b45fa135f7583a7549161 Mon Sep 17 00:00:00 2001 From: Richard Sandiford Date: Tue, 18 Feb 2020 18:06:32 +0000 Subject: [PATCH] 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. 2020-02-19 Richard Sandiford gcc/ 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/ PR tree-optimization/93767 * gcc.dg/vect/pr93767.c: New test. --- gcc/ChangeLog | 6 ++++++ gcc/testsuite/ChangeLog | 5 +++++ gcc/testsuite/gcc.dg/vect/pr93767.c | 13 +++++++++++++ gcc/tree-vect-data-refs.c | 4 ++-- 4 files changed, 26 insertions(+), 2 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/vect/pr93767.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 6cd941a5ff8..757d05a2f29 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,9 @@ +2020-02-19 Richard Sandiford + + 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. + 2020-02-19 Bernd Edlinger * collect2.c (c_file, o_file): Make const again. diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index df79951b6cc..2d88138cbb6 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,8 @@ +2020-02-19 Richard Sandiford + + PR tree-optimization/93767 + * gcc.dg/vect/pr93767.c: New test. + 2020-02-19 Martin Jambor PR tree-optimization/93776 diff --git a/gcc/testsuite/gcc.dg/vect/pr93767.c b/gcc/testsuite/gcc.dg/vect/pr93767.c new file mode 100644 index 00000000000..5f95d7bd35b --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/pr93767.c @@ -0,0 +1,13 @@ +int +main () +{ + int a[10], b; + for (b = 6; b >= 3; b--) + { + a[b] = 1; + a[b + 2] = a[3]; + } + if (a[5] != 1) + __builtin_abort (); + return 0; +} diff --git a/gcc/tree-vect-data-refs.c b/gcc/tree-vect-data-refs.c index 554ef892254..0192aa64636 100644 --- a/gcc/tree-vect-data-refs.c +++ b/gcc/tree-vect-data-refs.c @@ -3261,14 +3261,14 @@ vect_compile_time_alias (dr_vec_info *a, dr_vec_info *b, if (tree_int_cst_compare (DR_STEP (a->dr), size_zero_node) < 0) { const_length_a = (-wi::to_poly_wide (segment_length_a)).force_uhwi (); - offset_a = (offset_a + access_size_a) - const_length_a; + offset_a -= const_length_a; } else const_length_a = tree_to_poly_uint64 (segment_length_a); if (tree_int_cst_compare (DR_STEP (b->dr), size_zero_node) < 0) { const_length_b = (-wi::to_poly_wide (segment_length_b)).force_uhwi (); - offset_b = (offset_b + access_size_b) - const_length_b; + offset_b -= const_length_b; } else const_length_b = tree_to_poly_uint64 (segment_length_b); -- 2.30.2