Re: Teach same_types_for_tbaa to structurally compare arrays, pointers and vectors

[Jan Hubicka <hubicka@ucw.cz>]

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> 
> Please also see if there are testcases that do anything meaningful
> and FAIL after instead of
> 
>   /* Do access-path based disambiguation.  */
>   if (ref1 && ref2
>       && (handled_component_p (ref1) || handled_component_p (ref2)))
> 
> doing
> 
>   /* Do access-path based disambiguation.  */
>   if (ref1 && ref2
>       && (handled_component_p (ref1) && handled_component_p (ref2)))
> 
On tramp3d we get quite few matches which are attached. If ref1 is
MEM_REF and ref2 has non-trivial access path then it seems we need:
 1) ref1 and ref2 to conflict (ref1 is a record or alias set 0)
 2) basetype2 to contain ref1 (so it conflicts too)
 3) if ref1 is a record than the access path may go into a type
    contained as field of ref1 but via path not containing ref1 itself.

I tried to construct testcase:

truct foo {int val;} *fooptr;
struct bar {struct foo foo; int val2;} *barptr;
int test()
{ 
  struct foo foo={0};
  barptr->val2 = 1;
  *fooptr=foo;
  return barptr->val2;
}

but we do not optimize it. I.e. optimized dump has:

test ()
{
  struct bar * barptr.0_1;
  struct foo * fooptr.1_2;
  int _6;

  <bb 2> [local count: 1073741824]:
  barptr.0_1 = barptr;
  barptr.0_1->val2 = 1;
  fooptr.1_2 = fooptr;
  MEM[(struct foo *)fooptr.1_2] = 0;
  _6 = barptr.0_1->val2;
  return _6;
}

I see no reason why we should not constant propagate the return value.

Honza

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