[Bug tree-optimization/80680] New: dead code elimination fails to remove unreferenced function

[zmahler at openmailbox dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80680

            Bug ID: 80680
           Summary: dead code elimination fails to remove unreferenced
                    function
           Product: gcc
           Version: 6.3.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zmahler at openmailbox dot org
  Target Milestone: ---

With the following code, gcc will produce code for yes() even though it is not
referenced anymore after optimization.
Less problematic but probably related is that the call to no() is surprisingly
not inlined,
and the size of the code in the optimized away branch seems to have an
influence on that.

#include <stdio.h>

static inline void yes(void) { puts("yes"); }
static inline void no(void) { puts("no"); }

static inline void test(int v)
{
        if (v & 1) {
                printf("%d%d%d%d%d%d%d%d%d%d", 1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
        }
        (v ? yes : no)();
}

int main(void) { test(0); }

0000000000400430 <main>:
  400430:       48 83 ec 08             sub    rsp,0x8
  400434:       e8 07 01 00 00          call   400540 <no>
  400439:       31 c0                   xor    eax,eax
  40043b:       48 83 c4 08             add    rsp,0x8
  40043f:       c3                      ret    

0000000000400540 <no>:
  400540:       bf e4 05 40 00          mov    edi,0x4005e4
  400545:       e9 d6 fe ff ff          jmp    400420 <puts@plt>
  40054a:       66 0f 1f 44 00 00       nop    WORD PTR [rax+rax*1+0x0]

0000000000400550 <yes>:
  400550:       bf e7 05 40 00          mov    edi,0x4005e7
  400555:       e9 c6 fe ff ff          jmp    400420 <puts@plt>
  40055a:       66 0f 1f 44 00 00       nop    WORD PTR [rax+rax*1+0x0]

$ gcc --version
gcc (SUSE Linux) 6.3.1 20170202 [gcc-6-branch revision 245119]