[Bug middle-end/26198] New: Unfolded comparison after cfg_cleanup

[rguenth at gcc dot gnu dot org]

struct A
{
  int* x[2];
  A() { for (int** p=x; p<x+2; ++p) *p = 0; }
};

struct B
{
  char c;
  A a0, a1, a2, a3, *p;

  B() {}
  B(const B& b) : c(), a0(b.a0), p(b.p) {}
  ~B() { delete p; }
};

inline void foo(const B& b) { new B(b); }

void bar()
{
  foo(B());
  foo(B());
}

After cfg_cleanup after loop header copying we end up with unfolded

  &D.2114.a0D.2019.xD.1986[2] > &D.2114.a0D.2019.xD.1986[0]

because in fold_binary where we handle this kind of stuff we have

              if (!offset0 || !offset1
                  || TREE_TYPE (offset0) == TREE_TYPE (offset1))
                {
...

and unfortunately the constants 2 and 0 have distinct types:

(gdb) call debug_tree(offset0)
 <integer_cst 0x4026e888 type <integer_type 0x402474ac> constant invariant 8>
(gdb) call debug_tree(offset1)
 <integer_cst 0x4018d180 type <integer_type 0x4019f000 unsigned int> constant
invariant 0>


-- 
           Summary: Unfolded comparison after cfg_cleanup
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: rguenth at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26198