[Bug c++/46188] New: -fipa-cp removes destructor call

["jens.maurer at gmx dot net" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46188

           Summary: -fipa-cp removes destructor call
           Product: gcc
           Version: 4.5.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jens.maurer@gmx.net


Created attachment 22164
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=22164
source file to reproduce the bug

In the attached source code, the destructor calls for B::char_array when
destroying "c2" at the end of function "f" are removed by the optimizer when
compiling with -fipa-cp .

I have removed .cfi notes in the assembly quoted below, for conciseness.

bad compile:

$ g++  -S playground.cxx -fverbose-asm -O2

yields (note that no operator delete[] is called on B::char_array):

    159 .LEHB0:
    160         call    g(C const&, C&) #
    161 .LEHE0:
    162         movq    24(%rsp), %rdi  # c2.b_array.data, D.2822
    163         testq   %rdi, %rdi      # D.2822
    164         je      .L15    #,
    165         call    operator delete[](void*)        #
    166 .L15:
    167         movq    16(%rsp), %rdi  # c2.s.adr, D.2837
    168         testq   %rdi, %rdi      # D.2837
    169         je      .L14    #,
    170         call    operator delete[](void*)        #
    171 .L14:
    172         addq    $48, %rsp       #,
    175         popq    %rbx    #
    177         ret


good compile:

$ g++  -S playground.cxx -fverbose-asm -O2 -fno-ipa-cp

    165         call    g(C const&, C&) #
    166 .LEHE0:
    167         movq    8(%rsp), %rbx   # c2.b_array.data, p
    168         testq   %rbx, %rbx      # p
    169         je      .L15    #,
    170         movq    16(%rsp), %r12  # c2.b_array.size, D.2808
    171         testq   %r12, %r12      # D.2808
    172         je      .L16    #,
    173         xorl    %ebp, %ebp      # i
    174         jmp     .L20    #
    175         .p2align 4,,10
    176         .p2align 3
    177 .L25:
    178         addq    $24, %rbx       #, p
    179 .L20:
    180         movq    (%rbx), %rdi    # p->char_array.data, D.2820
    181         testq   %rdi, %rdi      # D.2820
    182         je      .L18    #,
    183         call    operator delete[](void*)        #
    184 .L18:
    185         addq    $1, %rbp        #, i
    186         cmpq    %rbp, %r12      # i, D.2808
    187         ja      .L25    #,
    188         movq    8(%rsp), %rbx   # c2.b_array.data, p
    189 .L16:
    190         testq   %rbx, %rbx      # p
    191         je      .L15    #,
    192         movq    %rbx, %rdi      # p,
    193         call    operator delete[](void*)        #
    194 .L15:
    195         movq    (%rsp), %rdi    # c2.s.adr, D.2824
    196         testq   %rdi, %rdi      # D.2824
    197         je      .L14    #,
    198         call    operator delete[](void*)        #
    199 .L14:
    200         addq    $32, %rsp       #,
    203         popq    %rbx    #
    205         popq    %rbp    #
    207         popq    %r12    #
    209         ret


Removing any one of the seemingly unrelated lines marked ##1, ##2, ##3 will
produce correct compiler output.  Also, messing with the Array::destruct
function (e.g. use "data + i" instead of "p", use the constants for start/end
directly instead of passing via parameters) will remove the problem.