[Bug tree-optimization/108353] New: Dead Code Elimination Regression at -O2 (trunk vs. 12.2.0)

[yann at ywg dot ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108353

            Bug ID: 108353
           Summary: Dead Code Elimination Regression at -O2 (trunk vs.
                    12.2.0)
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: yann at ywg dot ch
  Target Milestone: ---

Created attachment 54228
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54228&action=edit
presented code as file

cat case.c #99
enum { a } b();
int d;
int e;
int f;
void foo();
void bar49_(void);
void(c)();
static short g(int h, int i) {
  int j = 2874288693, k = 1;
  if (h)
    for (; j; j = j + 9) {
      f = 0;
      for (; f <= 1; c())
        k = 90;
    }
  i = k;
  for (; e; ++e) {
    if (i)
      continue;
    foo();
    i = b();
  }
  return 4;
}
int l() {
  bar49_();
  return 1;
}
int main() { d = d || g(d, l()); }

`gcc-cb93c5f8008b95743b741d6f1842f9be50c6985c (trunk) -O2` can not eliminate
`foo` but `gcc-releases/gcc-12.2.0 -O2` can.

`gcc-cb93c5f8008b95743b741d6f1842f9be50c6985c (trunk) -O2 -S -o /dev/stdout
case.c`
--------- OUTPUT ---------
main:
.LFB2:
        .cfi_startproc
        movl    d(%rip), %eax
        testl   %eax, %eax
        je      .L20
        movl    $1, d(%rip)
        xorl    %eax, %eax
        ret
.L20:
        pushq   %rbx
        .cfi_def_cfa_offset 16
        .cfi_offset 3, -16
        call    bar49_
        cmpl    $0, d(%rip)
        jne     .L12
        movl    $1, %eax
.L9:
        cmpl    $0, e(%rip)
        je      .L5
.L7:
        addl    $1, e(%rip)
        je      .L5
.L11:
        testl   %eax, %eax
        jne     .L7
        call    foo
        xorl    %eax, %eax
        call    b
        addl    $1, e(%rip)
        jne     .L11
.L5:
        movl    $1, d(%rip)
        xorl    %eax, %eax
        popq    %rbx
        .cfi_remember_state
        .cfi_def_cfa_offset 8
        ret
.L12:
        .cfi_restore_state
        movl    $1112290355, %ebx
        .p2align 4,,10
        .p2align 3
.L6:
        movl    $0, f(%rip)
        .p2align 4,,10
        .p2align 3
.L8:
        xorl    %eax, %eax
        call    c
        cmpl    $1, f(%rip)
        jle     .L8
        subl    $1, %ebx
        jne     .L6
        movl    $90, %eax
        jmp     .L9
---------- END OUTPUT ---------


`gcc-releases/gcc-12.2.0 -O2 -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB2:
        .cfi_startproc
        movl    d(%rip), %eax
        testl   %eax, %eax
        je      .L19
        movl    $1, d(%rip)
        xorl    %eax, %eax
        ret
.L19:
        pushq   %rbx
        .cfi_def_cfa_offset 16
        .cfi_offset 3, -16
        call    bar49_
        cmpl    $0, d(%rip)
        je      .L11
        movl    $1112290355, %ebx
        .p2align 4,,10
        .p2align 3
.L7:
        movl    $0, f(%rip)
        .p2align 4,,10
        .p2align 3
.L10:
        xorl    %eax, %eax
        call    c
        cmpl    $1, f(%rip)
        jle     .L10
        subl    $1, %ebx
        jne     .L7
.L11:
        cmpl    $0, e(%rip)
        je      .L6
        movl    $0, e(%rip)
.L6:
        movl    $1, d(%rip)
        xorl    %eax, %eax
        popq    %rbx
        .cfi_def_cfa_offset 8
        ret
---------- END OUTPUT ---------


Bisects to:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=af96500eea72c674a5686b35c66202ef2bd9688f