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From: "hiraditya at msn dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/109442] New: Dead local copy of std::vector
 not removed from function
Date: Thu, 06 Apr 2023 19:00:54 +0000
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X-Bugzilla-Component: tree-optimization
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109442

            Bug ID: 109442
           Summary: Dead local copy of std::vector not removed from
                    function
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hiraditya at msn dot com
  Target Milestone: ---

T vat1(std::vector<T> v1) {
    auto v =3D v1;
    return 10;
}

g++ -O3 -std=3Dc++20 -fno-exceptions

vat1(std::vector<int, std::allocator<int> >):
        mov     rax, QWORD PTR [rdi+8]
        sub     rax, QWORD PTR [rdi]
        je      .L11
        push    rbp
        mov     rbp, rax
        movabs  rax, 9223372036854775804
        push    rbx
        sub     rsp, 8
        cmp     rax, rbp
        jb      .L15
        mov     rbx, rdi
        mov     rdi, rbp
        call    operator new(unsigned long)
        mov     rsi, QWORD PTR [rbx]
        mov     rdx, QWORD PTR [rbx+8]
        mov     rdi, rax
        sub     rdx, rsi
        cmp     rdx, 4
        jle     .L16
        call    memmove
        mov     rdi, rax
.L6:
        mov     rsi, rbp
        call    operator delete(void*, unsigned long)
        add     rsp, 8
        mov     eax, 10
        pop     rbx
        pop     rbp
        ret
.L11:
        mov     eax, 10
        ret
.L15:
        call    std::__throw_bad_array_new_length()
.L16:
        jne     .L6
        mov     eax, DWORD PTR [rsi]
        mov     DWORD PTR [rdi], eax
        jmp     .L6=