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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/110173] New: [14 Regression] Missed Dead Code
 Elimination when using __builtin_unreachable since r14-569-g21e2ef2dc25
Date: Thu, 08 Jun 2023 14:07:02 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110173

            Bug ID: 110173
           Summary: [14 Regression] Missed Dead Code Elimination when
                    using __builtin_unreachable since r14-569-g21e2ef2dc25
           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/ssja5dKdY


void foo(void);
static int e, f, n, *g, **h =3D &g;
static short m;
void __assert_fail() __attribute__((__noreturn__));
static short(a)(short b) { return b; }
static short(c)(short d) {
    if (!(((d) >=3D 1) && ((d) <=3D 1))) {
        __builtin_unreachable();
    }
    return 0;
}
static int *j();
static void k(int *l, char) {
    *l =3D 0;
    if (g =3D=3D &e || g =3D=3D 0 || g =3D=3D &f);
    else {
        foo();
        __assert_fail();
    }
    c(f < 5);
}
static void i() { *h =3D j(); }
static int *j(unsigned o) {
    char p;
    if (g =3D=3D &f || g =3D=3D 0);
    else
        __assert_fail();
    p =3D m > (a(1) && o);
    k(&n, p);
    if (g =3D=3D 0);
    else
        __assert_fail();
    return 0;
}
int main() { i(); }


gcc-trunk -Os -S:=20

main:
        movq    g(%rip), %rax
        testq   %rax, %rax
        je      .L2
        cmpq    $f, %rax
        je      .L2
.L3:
        pushq   %rsi
        xorl    %eax, %eax
        call    __assert_fail
.L2:
        xorl    %ecx, %ecx
        movl    %ecx, n(%rip)
        testq   %rax, %rax
        jne     .L3
        xorl    %edx, %edx
        movq    %rdx, g(%rip)
        ret


main:
        pushq   %rsi
        movq    g(%rip), %rax
        cmpq    $f, %rax
        je      .L2
        testq   %rax, %rax
        jne     .L13
.L2:
        xorl    %ecx, %ecx
        movl    %ecx, n(%rip)
        cmpq    $f, %rax
        je      .L3
        testq   %rax, %rax
        je      .L11
        call    foo
.L13:
        xorl    %eax, %eax
        call    __assert_fail
.L3:
        testq   %rax, %rax
        jne     .L13
.L11:
        xorl    %eax, %eax
        movq    %rax, g(%rip)
        xorl    %eax, %eax
        popq    %rdx
        ret


Bisects to r14-569-g21e2ef2dc25=