[Bug tree-optimization/114145] New: Missed optimization of loop deletion

["652023330028 at smail dot nju.edu.cn" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114145

            Bug ID: 114145
           Summary: Missed optimization of loop deletion
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: 652023330028 at smail dot nju.edu.cn
  Target Milestone: ---

Hello, we noticed that in the code below, looping is not necessary, but gcc
seems to have missed this optimization.

https://godbolt.org/z/sYqzh8M3c
int a, b;
void func(int c){
    for(int i=0;i<700;i++){
        b=c;
        c=a;
    }
}

GCC -O3:
func(int):
        mov     edx, DWORD PTR a[rip]
        mov     eax, 700
        jmp     .L2
.L3:
        sub     eax, 3
        mov     edi, edx
.L2:
        cmp     eax, 1
        jne     .L3
        mov     DWORD PTR b[rip], edi
        ret

Expected code (Clang):
func(int):                               # @func(int)
        mov     eax, dword ptr [rip + a]
        mov     dword ptr [rip + b], eax
        ret

Thank you very much for your time and effort! We look forward to hearing from
you.