1  /* PR c/71924 - missing -Wreturn-local-addr returning alloca result
       2     Test derived from gcc.c-torture/execute/20071108-1.c.  It shows
       3     a false positive at -Os caused by the jump threading/vrp1 pass.
       4     { dg-do compile }
       5     { dg-options "-Os -fdump-tree-optimized" } */
       6  
       7  struct S
       8  {
       9    int i;
      10  };
      11  
      12  void* f (void);
      13  
      14  __attribute__ ((noinline))
      15  struct S* g (int i)
      16  {
      17    struct S *p = f (), q;
      18  
      19    if (p == 0)
      20      p = &q;
      21  
      22    p->i = i;
      23  
      24    if (p == &q)
      25      p = 0;
      26  
      27    /* With -Os the warning pass sees:
      28  
      29         ...
      30         <bb 4>
      31         # p_1 = PHI <&q(2), p_5(3)>
      32         p_1->i = i_6(D);
      33         if (&q == p_1)
      34           goto <bb 6>; [14.90%]
      35         else
      36           goto <bb 5>; [85.10%]
      37  
      38         <bb 5>
      39  
      40         <bb 6>
      41         # p_2 = PHI <0B(4), p_1(5)>
      42         q ={v} {CLOBBER};
      43         return p_2;
      44       }
      45  
      46       which leads to:  */
      47    return p;         /* { dg-bogus "may return address of local variable" "" { xfail *-*-* } } */
      48  
      49    /* Whereas as -O2 the pass sees:
      50  
      51         <bb 2>
      52         p_5 = f ();
      53         if (p_5 == 0B)
      54           goto <bb 4>; [30.00%]
      55         else
      56           goto <bb 3>; [70.00%]
      57  
      58         <bb 3>
      59         # p_2 = PHI <0B(5), p_5(4)>
      60         q ={v} {CLOBBER};
      61         return p_2;
      62  
      63         <bb 4>
      64         p_5->i = i_6(D);
      65         goto <bb 3>; [100.00%]
      66  
      67         <bb 5>
      68         q.i = i_6(D);
      69         goto <bb 3>; [100.00%]
      70       }
      71  
      72       and no warning.  */
      73  }