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From: "theodort at inf dot ethz.ch" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/112542] New: [14 Regression] Dead Code
 Elimination Regression since r14-4280-gc3c6f30496d
Date: Wed, 15 Nov 2023 09:42:59 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D112542

            Bug ID: 112542
           Summary: [14 Regression] Dead Code Elimination Regression since
                    r14-4280-gc3c6f30496d
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: theodort at inf dot ethz.ch
  Target Milestone: ---

https://godbolt.org/z/3vj8x1bPK

Given the following code:

void foo(void);
static short b =3D -1;
static int c, e;
static int *f =3D &c;
static char g;
static char(a)(char h, int i) {
    if (!(((i) >=3D -1) && ((i) <=3D 0))) {
        __builtin_unreachable();
    }
    return h || i ? h : h < 0;
}
static void(d)(unsigned h) {
    if (!(((h) >=3D 0) && ((h) <=3D 4095017279))) {
        foo();
    }
}
int main() {
    *f =3D b =3D=3D 0;
    g =3D a(c, c);
    d(g);
    d(4095017279);
    if (e) b =3D 0;
    a(0, b);
}

gcc-trunk -O3 does not eliminate the call to foo:

main:
        xorl    %eax, %eax
        cmpw    $0, b(%rip)
        sete    %al
        movl    %eax, c(%rip)
        jne     .L4
        pushq   %rax
        call    foo
        xorl    %eax, %eax
        popq    %rdx
        ret
.L4:
        xorl    %eax, %eax
        ret

gcc-13.2.0 -O3 eliminates the call to foo:

main:
        xorl    %eax, %eax
        cmpw    $0, b(%rip)
        sete    %al
        movl    %eax, c(%rip)
        xorl    %eax, %eax
        ret

Bisects to r14-4280-gc3c6f30496d=