create_intersect_range_checks checks whether two access ranges a and b are alias-free using something equivalent to:
end_a <= start_b || end_b <= start_a It has two ways of doing this: a "vanilla" way that calculates the exact exclusive end pointers, and another way that uses the last inclusive aligned pointers (and changes the comparisons accordingly). The comment for the latter is: /* Calculate the minimum alignment shared by all four pointers, then arrange for this alignment to be subtracted from the exclusive maximum values to get inclusive maximum values. This "- min_align" is cumulative with a "+ access_size" in the calculation of the maximum values. In the best (and common) case, the two cancel each other out, leaving us with an inclusive bound based only on seg_len. In the worst case we're simply adding a smaller number than before. The problem is that the associated code implicitly assumed that the access size was a multiple of the pointer alignment, and so the alignment could be carried over to the exclusive end pointer. The testcase started failing after g:9fa5b473b5b8e289b6542 because that commit improved the alignment information for the accesses. Tested on aarch64-linux-gnu & x86_64-linux-gnu. OK for trunk and backports? Richard gcc/ PR tree-optimization/115192 * tree-data-ref.cc (create_intersect_range_checks): Take the alignment of the access sizes into account. gcc/testsuite/ PR tree-optimization/115192 * gcc.dg/vect/pr115192.c: New test. --- gcc/testsuite/gcc.dg/vect/pr115192.c | 28 ++++++++++++++++++++++++++++ gcc/tree-data-ref.cc | 5 ++++- 2 files changed, 32 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gcc.dg/vect/pr115192.c diff --git a/gcc/testsuite/gcc.dg/vect/pr115192.c b/gcc/testsuite/gcc.dg/vect/pr115192.c new file mode 100644 index 00000000000..923d377c1bb --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/pr115192.c @@ -0,0 +1,28 @@ +#include "tree-vect.h" + +int data[4 * 16 * 16] __attribute__((aligned(16))); + +__attribute__((noipa)) void +foo (__SIZE_TYPE__ n) +{ + for (__SIZE_TYPE__ i = 1; i < n; ++i) + { + data[i * n * 4] = data[(i - 1) * n * 4] + 1; + data[i * n * 4 + 1] = data[(i - 1) * n * 4 + 1] + 2; + } +} + +int +main () +{ + check_vect (); + + data[0] = 10; + data[1] = 20; + + foo (3); + + if (data[24] != 12 || data[25] != 24) + __builtin_abort (); + return 0; +} diff --git a/gcc/tree-data-ref.cc b/gcc/tree-data-ref.cc index db15ddb43de..7c4049faf34 100644 --- a/gcc/tree-data-ref.cc +++ b/gcc/tree-data-ref.cc @@ -73,6 +73,7 @@ along with GCC; see the file COPYING3. If not see */ +#define INCLUDE_ALGORITHM #include "config.h" #include "system.h" #include "coretypes.h" @@ -2640,7 +2641,9 @@ create_intersect_range_checks (class loop *loop, tree *cond_expr, Because the maximum values are inclusive, there is an alias if the maximum value of one segment is equal to the minimum value of the other. */ - min_align = MIN (dr_a.align, dr_b.align); + min_align = std::min (dr_a.align, dr_b.align); + min_align = std::min (min_align, known_alignment (dr_a.access_size)); + min_align = std::min (min_align, known_alignment (dr_b.access_size)); cmp_code = LT_EXPR; } -- 2.25.1