[Bug c++/127685] [17 Regression] Constant member-function pointer table loads optimized to null since r17-4752

[slyfox at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=127685

Sergei Trofimovich <slyfox at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |slyfox at gcc dot gnu.org

--- Comment #8 from Sergei Trofimovich <slyfox at gcc dot gnu.org> ---
I got re2 test failure. The reduced example is similar:

$ cat /tmp/a.cc                                                                
                     struct C {
  bool m0(bool){return false;}
  bool m1(bool){return false;}

  bool bug(bool);
};

__attribute__((noipa))
bool C::bug(bool b){
  static bool (C::*A[])(bool) = {
      &C::m0,
      &C::m1,
  };
  int index = 1 * b;
  return (this->*A[index])(b);
}

int main() {
  C o;
  o.bug(false);
}

$ g++ -O1 /tmp/a.cc -o a -Wall && ./a
Segmentation fault         (core dumped) ./a

Looks the same?

(gdb) disassemble _ZN1C3bugEb
Dump of assembler code for function _ZN1C3bugEb:
   0x000000000000112a <+0>:     push   %rbp
   0x000000000000112b <+1>:     mov    %rsp,%rbp
   0x000000000000112e <+4>:     movzbl %sil,%esi
   0x0000000000001132 <+8>:     mov    $0x0,%eax
   0x0000000000001137 <+13>:    call   *%rax
   0x0000000000001139 <+15>:    pop    %rbp
   0x000000000000113a <+16>:    ret
End of assembler dump.