[Bug c++/65143] [C++11] missing devirtualization for virtual base in "final" classes

["maltsevm at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65143

Mikhail Maltsev <maltsevm at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |maltsevm at gmail dot com

--- Comment #3 from Mikhail Maltsev <maltsevm at gmail dot com> ---
This optimization is still missing in current trunk:

$ cat ./test.cc
struct A
{
    int j;
};

struct B : public virtual A
{
};

struct C final : public B
{
    int get();
};

int C::get()
{
    return A::j;
}

$ /opt/gcc-5.0.0/bin/g++ -O -std=c++11 -c -S ./test.cc -o test_gcc.s && cat
./test_gcc.s
        .file   "test.cc"
        .text
        .align 2
        .globl  _ZN1C3getEv
        .type   _ZN1C3getEv, @function
_ZN1C3getEv:
.LFB0:
        .cfi_startproc
        movq    (%rdi), %rax
        movq    -24(%rax), %rax
        movl    (%rdi,%rax), %eax
        ret
        .cfi_endproc
.LFE0:
        .size   _ZN1C3getEv, .-_ZN1C3getEv
        .ident  "GCC: (GNU) 5.0.0 20150315 (experimental)"
        .section        .note.GNU-stack,"",@progbits

(Note: optimization flags like -O3 and -fdevirtualize-speculatively don't
affect this behavior; neither method calls nor data member accesses get
devirtualized)

$ clang++ -O -std=c++11 -c -S ./test.cc -o test_clang.s && cat ./test_clang.s 
        .text
        .file   "./test.cc"
        .globl  _ZN1C3getEv
        .align  16, 0x90
        .type   _ZN1C3getEv,@function
_ZN1C3getEv:                            # @_ZN1C3getEv
        .cfi_startproc
# BB#0:                                 # %entry
        movl    8(%rdi), %eax
        retq
.Ltmp0:
        .size   _ZN1C3getEv, .Ltmp0-_ZN1C3getEv
        .cfi_endproc


        .ident  "clang version 3.7.0 (trunk 228487)"
        .section        ".note.GNU-stack","",@progbits

So, I can confirm it in sense "reproduce" (I don't have a right to change the
status of PR)