[Bug tree-optimization/94092] New: Code size and performance degradations after -ftree-loop-distribute-patterns was enabled at -O[2s]+

["bina2374 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94092

            Bug ID: 94092
           Summary: Code size and performance degradations after
                    -ftree-loop-distribute-patterns was enabled at -O[2s]+
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bina2374 at gmail dot com
  Target Milestone: ---
            Target: riscv64-unknown-elf

Since https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88440,
loop-distribute-patterns was enabled at -O[2s]+. We understand that this patch
is helpful in some cases, but not for all.
In the original bugzilla, the loop count is known, and the performance and code
size are all improved finally. However, if loop count is unknown, the results
may become worse.

void init_array(int N, int *array) {
  int i;
  for (i = 0; i < N; i++)
    array[i] = 0;
}

init_array:
        mv      a2,a0
        mv      a0,a1
        ble     a2,zero,.L1
        slli    a2,a2,2
        li      a1,0
        tail    memset
.L1:
        ret

For coremark, this is not only harmful to performance, but also code size.
Therefore, I suggest that we have to discuss how to resolve the case of unknown
loop count.