[Bug c++/61531] New: Optimizer completely removes some bitset code

[Ulrich.Windl at rz dot uni-regensburg.de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61531

            Bug ID: 61531
           Summary: Optimizer completely removes some bitset code
           Product: gcc
           Version: 4.3.4
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: Ulrich.Windl at rz dot uni-regensburg.de

I wrote a simple test code for <bitset> that the default optimization complete
removes. Only -O0 keept the code. However the default code should output. Thus
I consider the optimization bad. Preprocessed input will follow, but here is
the basic test:
---
~/src/C++/bitsettest> cat bstest.cc
#include        <iostream>
#include        <bitset>

int     main(int argc, char *argv[])
{
        std::bitset<32> b;

#if 0
        std::cout << "size " << b.size() << std::endl;
#endif
        b.set(2);
        if (b.test(2))
                std::cout << "set 2" << std::endl;
        if (b[3])
                std::cout << "set 3" << std::endl;
        return 0;
}
~/src/C++/bitsettest> make
g++   -Wall -Wextra -Wshadow -pipe -O2 -g --save-temps    -c -o bstest.o
bstest.cc
g++: warning: -pipe ignored because -save-temps specified
bstest.cc:4: warning: unused parameter ‘argc’
bstest.cc:4: warning: unused parameter ‘argv’
g++  -o bstest bstest.o
~/src/C++/bitsettest>

(gdb) disassemble /m main
Dump of assembler code for function main(int, char**):
4       int     main(int argc, char *argv[])
   0x00000000004008b0 <+0>:     sub    $0x8,%rsp

5       {
6               std::bitset<32> b;
7
8       #if 0
9               std::cout << "size " << b.size() << std::endl;
10      #endif
11              b.set(2);
12              if (b.test(2))
13                      std::cout << "set 2" << std::endl;
14              if (b[3])
15                      std::cout << "set 3" << std::endl;
16              return 0;
17      }
   0x00000000004008d2 <+34>:    xor    %eax,%eax
   0x00000000004008d4 <+36>:    add    $0x8,%rsp
   0x00000000004008d8 <+40>:    retq

End of assembler dump.
---