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From: "scherrer.sv at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/110873] New: [14 Regression] Dead Code
 Elimination Regression at -O2 since r14-376-g47a76439911
Date: Wed, 02 Aug 2023 12:34:39 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: tree-optimization
X-Bugzilla-Version: 14.0
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X-Bugzilla-Severity: normal
X-Bugzilla-Who: scherrer.sv at gmail dot com
X-Bugzilla-Status: UNCONFIRMED
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110873

            Bug ID: 110873
           Summary: [14 Regression] Dead Code Elimination Regression at
                    -O2 since r14-376-g47a76439911
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: scherrer.sv at gmail dot com
  Target Milestone: ---

static int b;
static short c;
static char d;
static int *e =3D &b;
void foo(void);=20=20
void bar110_(void);
static char(a)(char f, char g) { return f + g; }
int main() {
    *e =3D 3;
    unsigned char h;
    c =3D 0;
i:
    if (!b)
        foo();
    h =3D -25;
    for (; h >=3D 7; h =3D a(h, 6))
        for (; d; d--)
            ;
    if (!(h >=3D 5))
        bar110_();
    if (c)
        goto i;
}
-----------------------------------------------------------------------
gcc-68c3aa7510b (trunk) -O2 cannot eliminate the call to foo but
gcc-releases/gcc-13.1.0 -O2 can
-----------------------------------------------------------------------
gcc-68c3aa7510b2f45f44379ecd77e97c88780a84ed -O2 case.c -S -o case.s
--------- OUTPUT ---------
main:
.LFB1:
        .cfi_startproc
        movl    $3, b(%rip)
        xorl    %esi, %esi
        movw    %si, c(%rip)
.L11:
        cmpb    $0, d(%rip)
        je      .L13
        movb    $0, d(%rip)
.L13:
        cmpw    $0, c(%rip)
        je      .L15
        movl    b(%rip), %eax
        testl   %eax, %eax
        jne     .L11
        subq    $8, %rsp
        .cfi_def_cfa_offset 16
.L6:
        call    foo
.L2:
        cmpb    $0, d(%rip)
        je      .L4
        movb    $0, d(%rip)
.L4:
        cmpw    $0, c(%rip)
        je      .L5
        movl    b(%rip), %ecx
        testl   %ecx, %ecx
        jne     .L2
        jmp     .L6
.L15:
        .cfi_def_cfa_offset 8
        xorl    %eax, %eax
        ret
.L5:
        .cfi_def_cfa_offset 16
        xorl    %eax, %eax
        popq    %rdx
        .cfi_def_cfa_offset 8
        ret
---------- END OUTPUT ---------

-----------------------------------------------------------------------
gcc-2b98cc24d6af0432a74f6dad1c722ce21c1f7458 -O2 case.c -S -o case.s
--------- OUTPUT ---------
main:
.LFB1:
        .cfi_startproc
        movl    $3, b(%rip)
        xorl    %eax, %eax
        cmpb    $0, d(%rip)
        movw    %ax, c(%rip)
        je      .L3
        movb    $0, d(%rip)
.L3:
        xorl    %eax, %eax
        ret
---------- END OUTPUT ---------

-----------------------------------------------------------------------
Bisects to r14-376-g47a76439911=