[Bug tree-optimization/110414] New: [14 Regression] Dead Code Elimination Regression since r14-1127-g9e2017ae6ac

[Bug tree-optimization/110414] New: [14 Regression] Dead Code Elimination Regression since r14-1127-g9e2017ae6ac

[theodort at inf dot ethz.ch]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110414

            Bug ID: 110414
           Summary: [14 Regression] Dead Code Elimination Regression
                    since  r14-1127-g9e2017ae6ac
           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/5E795dPvY

Given the following code:

void foo(void);
static int a, b, e, l, m, n;
static int *c = &a, *j;
static int **d = &c;
static int ***f;
void __assert_fail(char *, char *, int, char *) __attribute__((__noreturn__));
static void g(char) {
    if (c == &b || c == &a)
        ;
    else
        __assert_fail("", "", 3, __PRETTY_FUNCTION__);
}
static void h();
static int *i();
static short k() {
    j = i();
    h();
    **f = &e;
    if (c == &b || c == &a || c == 0)
        __assert_fail("", "", 6, __PRETTY_FUNCTION__);
    return 0;
}
static void h() {
    if (l) {
        for (; l; l = l - 8) *d = &m;
        if (c == &a)
            ;
        else
            __assert_fail("", "", 9, __PRETTY_FUNCTION__);
    }
    if (c == &b || c == &a || c == 0)
        ;
    else {
        foo();
        __assert_fail("", "", 8, __PRETTY_FUNCTION__);
    }
}
static int *i() {
    if (c == &b || c == &a)
        ;
    else {
        __builtin_unreachable();
        __assert_fail("", "", 6, __PRETTY_FUNCTION__);
    }
    return &n;
}
int main() { g(a && k()); }

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

main:
        pushq   %rcx
        cmpl    $0, a(%rip)
        je      .L2
        movl    l(%rip), %edx
        testl   %edx, %edx
        je      .L3
        movl    %edx, %eax
        movl    $__PRETTY_FUNCTION__.1, %ecx
        movq    $m, c(%rip)
        shrl    $3, %eax
        imull   $-8, %eax, %eax
        addl    %edx, %eax
        movl    $9, %edx
        movl    %eax, l(%rip)
        jmp     .L7
.L3:
        movq    c(%rip), %rax
        cmpq    $a, %rax
        sete    %dl
        cmpq    $b, %rax
        sete    %cl
        orb     %cl, %dl
        jne     .L4
        testq   %rax, %rax
        je      .L4
        call    foo
        movl    $__PRETTY_FUNCTION__.1, %ecx
        movl    $8, %edx
.L7:
        movl    $.LC0, %esi
        movq    %rsi, %rdi
        call    __assert_fail
.L4:
        movl    $__PRETTY_FUNCTION__.2, %ecx
        movl    $6, %edx
        jmp     .L7
.L2:
        movq    c(%rip), %rax
        cmpq    $a, %rax
        je      .L5
        cmpq    $b, %rax
        je      .L5
        movl    $__PRETTY_FUNCTION__.0, %ecx
        movl    $3, %edx
        jmp     .L7
.L5:
        xorl    %eax, %eax
        popq    %rdx
        ret

gcc-13.1.0 -Os eliminates the call to foo:

main:
        pushq   %rcx
        movq    c(%rip), %rdx
        cmpq    $a, %rdx
        sete    %al
        cmpq    $b, %rdx
        sete    %dl
        orl     %edx, %eax
        cmpl    $0, a(%rip)
        je      .L2
        movl    l(%rip), %edx
        testl   %edx, %edx
        je      .L3
        movl    %edx, %eax
        movl    $__PRETTY_FUNCTION__.1, %ecx
        movq    $m, c(%rip)
        shrl    $3, %eax
        imull   $-8, %eax, %eax
        addl    %edx, %eax
        movl    $9, %edx
        movl    %eax, l(%rip)
        jmp     .L7
.L2:
        testb   %al, %al
        jne     .L5
        movl    $__PRETTY_FUNCTION__.0, %ecx
        movl    $3, %edx
.L7:
        movl    $.LC0, %esi
        movq    %rsi, %rdi
        call    __assert_fail
.L3:
        movl    $__PRETTY_FUNCTION__.2, %ecx
        movl    $6, %edx
        jmp     .L7
.L5:
        xorl    %eax, %eax
        popq    %rdx
        ret

Bisects to r14-1127-g9e2017ae6ac

[Bug tree-optimization/110414] [14 Regression] Dead Code Elimination Regression since r14-1127-g9e2017ae6ac

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110414

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |14.0
             Blocks|                            |109849
           Keywords|                            |missed-optimization


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109849
[Bug 109849] suboptimal code for vector walking loop

[Bug tree-optimization/110414] [14 Regression] Dead Code Elimination Regression since r14-1127-g9e2017ae6ac

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110414

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-06-27

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
DOM3 removes the call in GCC 13 and the cause looks pretty similar to PR110413,
we lose a __builtin_unreachable () early.

[Bug tree-optimization/110414] [14 Regression] Dead Code Elimination Regression since r14-1127-g9e2017ae6ac

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110414

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |law at gcc dot gnu.org
           Priority|P3                          |P2

[Bug tree-optimization/110414] [14/15 Regression] Dead Code Elimination Regression since r14-1127-g9e2017ae6ac

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110414

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|14.0                        |14.2

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 14.1 is being released, retargeting bugs to GCC 14.2.