Re: Make nonoverlapping_component_refs_since_match_p work with non-trivial MEM_REFs and TMRs

[Richard Biener <rguenther at suse dot de>]

On Thu, 11 Jul 2019, Jan Hubicka wrote:

> > > On Thu, 11 Jul 2019, Jan Hubicka wrote:
> > > 
> > > > Hi,
> > > > this patch makes nonoverlapping_component_refs_since_match_p to accept
> > > > paths with non-trivial MEM_REFs and TMRs assuming that they have same
> > > > semantics.
> > > 
> > > Hmm.  We'll never get any TARGET_MEM_REFs wrapped with
> > > handled-components so I wonder if it makes sense to handle it in
> > > nonoverlapping_component_refs_since_match_p at all.
> > 
> > OK, that makes my life easier. Here is updated patch.
> Hi,
> the patch finished testing on x86_64-linux so here is with Changelog and
> testcase. OK?

OK.

Richard.

> 
> 
> 	* tree-ssa-alias.c (same_tmr_indexing_p): Break out from ...
> 	(indirect_refs_may_alias_p): ... here.
> 	(nonoverlapping_component_refs_since_match_p): Support also non-trivial
> 	mem refs in the access paths.
> Index: testsuite/gcc.dg/tree-ssa/alias-access-path-9.c
> ===================================================================
> --- testsuite/gcc.dg/tree-ssa/alias-access-path-9.c	(nonexistent)
> +++ testsuite/gcc.dg/tree-ssa/alias-access-path-9.c	(working copy)
> @@ -0,0 +1,44 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-fre1" } */
> +
> +/* This testcase tests nonoverlapping_component_refs_since_match_p in presence
> +   of non-trivial mem-refs.  */
> +struct a {int a,b;};
> +struct b {struct a a[10];};
> +struct c {int c; struct b b;} c, *cptr;
> +
> +void
> +set_a(struct a *a, int p)
> +{
> +  a->a=p;
> +}
> +void
> +set_b(struct a *a, int p)
> +{
> +  a->b=p;
> +}
> +int
> +get_a(struct a *a)
> +{
> +  return a->a;
> +}
> +
> +int
> +test(int i, int j)
> +{
> +  struct b *bptr = &c.b;
> +  set_a (&bptr->a[i], 123);
> +  set_b (&bptr->a[j], 124);
> +  return get_a (&bptr->a[i]);
> +}
> +
> +int
> +test2(int i, int j)
> +{
> +  struct b *bptr = &cptr->b;
> +  set_a (&bptr->a[i], 125);
> +  set_b (&bptr->a[j], 126);
> +  return get_a (&bptr->a[i]);
> +}
> +/* { dg-final { scan-tree-dump-times "return 123" 1 "fre1"} } */
> +/* { dg-final { scan-tree-dump-times "return 125" 1 "fre1"} } */
> Index: tree-ssa-alias.c
> ===================================================================
> --- tree-ssa-alias.c	(revision 273322)
> +++ tree-ssa-alias.c	(working copy)
> @@ -1265,20 +1265,6 @@ nonoverlapping_component_refs_since_matc
>          component_refs1.safe_push (ref1);
>        ref1 = TREE_OPERAND (ref1, 0);
>      }
> -  if (TREE_CODE (ref1) == MEM_REF && ref1 != match1)
> -    {
> -      if (!integer_zerop (TREE_OPERAND (ref1, 1)))
> -	{
> -	  ++alias_stats.nonoverlapping_component_refs_since_match_p_may_alias;
> -	  return -1;
> -	}
> -    }
> -  /* TODO: Handle TARGET_MEM_REF later.  */
> -  if (TREE_CODE (ref1) == TARGET_MEM_REF && ref1 != match1)
> -    {
> -      ++alias_stats.nonoverlapping_component_refs_since_match_p_may_alias;
> -      return -1;
> -    }
>  
>    /* Create the stack of handled components for REF2.  */
>    while (handled_component_p (ref2) && ref2 != match2)
> @@ -1290,20 +1276,31 @@ nonoverlapping_component_refs_since_matc
>          component_refs2.safe_push (ref2);
>        ref2 = TREE_OPERAND (ref2, 0);
>      }
> -  if (TREE_CODE (ref2) == MEM_REF && ref2 != match2)
> -    {
> -      if (!integer_zerop (TREE_OPERAND (ref2, 1)))
> -	{
> -	  ++alias_stats.nonoverlapping_component_refs_since_match_p_may_alias;
> -	  return -1;
> -	}
> -    }
> -  if (TREE_CODE (ref2) == TARGET_MEM_REF && ref2 != match2)
> +
> +  bool mem_ref1 = TREE_CODE (ref1) == MEM_REF && ref1 != match1;
> +  bool mem_ref2 = TREE_CODE (ref2) == MEM_REF && ref2 != match2;
> +
> +  /* If only one of access paths starts with MEM_REF check that offset is 0
> +     so the addresses stays the same after stripping it.
> +     TODO: In this case we may walk the other access path until we get same
> +     offset.
> +
> +     If both starts with MEM_REF, offset has to be same.  */
> +  if ((mem_ref1 && !mem_ref2 && !integer_zerop (TREE_OPERAND (ref1, 1)))
> +      || (mem_ref2 && !mem_ref1 && !integer_zerop (TREE_OPERAND (ref2, 1)))
> +      || (mem_ref1 && mem_ref2
> +	  && !tree_int_cst_equal (TREE_OPERAND (ref1, 1),
> +				  TREE_OPERAND (ref2, 1))))
>      {
>        ++alias_stats.nonoverlapping_component_refs_since_match_p_may_alias;
>        return -1;
>      }
>  
> +  /* TARGET_MEM_REF are never wrapped in handled components, so we do not need
> +     to handle them here at all.  */
> +  gcc_checking_assert (TREE_CODE (ref1) != TARGET_MEM_REF
> +		       && TREE_CODE (ref2) != TARGET_MEM_REF);
> +
>    /* Pop the stacks in parallel and examine the COMPONENT_REFs of the same
>       rank.  This is sufficient because we start from the same DECL and you
>       cannot reference several fields at a time with COMPONENT_REFs (unlike
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany;
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah; HRB 21284 (AG Nürnberg)