[Bug tree-optimization/120817] [13/14/15/16 regression] Wrong code when compiled with -O1 -ftree-loop-vectorize for AArch64 target

[tnfchris at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120817

Tamar Christina <tnfchris at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|aarch64-linux-gnu           |aarch64-*
              Build|x86_64-linux-gnu            |
               Host|x86_64-linux-gnu            |
   Last reconfirmed|                            |2025-06-25
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED

--- Comment #8 from Tamar Christina <tnfchris at gcc dot gnu.org> ---
C testcase

typedef struct {
    int _M_current;
} __normal_iterator;

typedef struct {
    char _M_elems[5];
} array_5;

__normal_iterator __trans_tmp_1 = {0};

array_5 copySourceIntoTarget() {
    array_5 target;
    char* target_it = target._M_elems;

    while (__trans_tmp_1._M_current != 0) {
        *target_it = 0;
        __trans_tmp_1._M_current++;
        target_it++;
    }

    return target;
}

compiled with -mcpu=neoverse-n2 -O1 -ftree-loop-vectorize

The cost model for Neoverse-N2 is needed to get it to generate an Adv.SIMD main
loop and an SVE trailing loop.