[Bug tree-optimization/102564] New: Missed loop vectorization with reduction and ptr load/store inside loop

[david.bolvansky at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102564

            Bug ID: 102564
           Summary: Missed loop vectorization with reduction and ptr
                    load/store inside loop
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: david.bolvansky at gmail dot com
  Target Milestone: ---

void test1(int *p, int *t, int N) {
    for (int i = 0; i != N; i++) *t += p[i];
}

void test2(int *p, int *t, int N) {
    if (N > 1024) // hint, N is not small
        for (int i = 0; i != N; i++) *t += p[i];
}

void test3(int *p, int *t, int N) {
    if (N > 1024) { // hint, N is not small
        int s = 0;
        for (int i = 0; i != N; i++) s += p[i];
        *t += s;
    }
}

test3 is successfully vectorized with LLVM, GCC, ICC. Sadly, only ICC can catch
test1 and test2.

https://godbolt.org/z/PzoYd4eEK