[PATCH] Fix SCCVN aggregate copy code some more

[PATCH] Fix SCCVN aggregate copy code some more

[Richard Guenther]

When adjusting the C++ FE code generation for base type copies
I noticed the XFAILs on g++.dg/tree-ssa/pr41186.C and investigated
things a bit.  We can fix the testcase easily iff the frontend
emits the MEM_REF variants, thus the following patch.

Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.

Richard.

2011-08-11  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-sccvn.c (vn_reference_lookup_3): Avoid redundant
	lookups, make looking through aggregate copies stronger.

Index: gcc/tree-ssa-sccvn.c
===================================================================
*** gcc/tree-ssa-sccvn.c	(revision 177649)
--- gcc/tree-ssa-sccvn.c	(working copy)
*************** vn_reference_lookup_3 (ao_ref *ref, tree
*** 1351,1367 ****
      {
        VEC (vn_reference_op_s, heap) *tem;
        tree lhs = gimple_assign_lhs (def_stmt);
        /* Avoid re-allocation overhead.  */
        VEC_truncate (vn_reference_op_s, lhs_ops, 0);
        copy_reference_ops_from_ref (lhs, &lhs_ops);
        tem = lhs_ops;
!       lhs_ops = valueize_refs (lhs_ops);
        gcc_assert (lhs_ops == tem);
!       lhs_ref_ok = ao_ref_init_from_vn_reference (&lhs_ref, get_alias_set (lhs),
! 						  TREE_TYPE (lhs), lhs_ops);
!       if (lhs_ref_ok
! 	  && !refs_may_alias_p_1 (ref, &lhs_ref, true))
! 	return NULL;
      }
  
    base = ao_ref_base (ref);
--- 1351,1377 ----
      {
        VEC (vn_reference_op_s, heap) *tem;
        tree lhs = gimple_assign_lhs (def_stmt);
+       bool valueized_anything = false;
        /* Avoid re-allocation overhead.  */
        VEC_truncate (vn_reference_op_s, lhs_ops, 0);
        copy_reference_ops_from_ref (lhs, &lhs_ops);
        tem = lhs_ops;
!       lhs_ops = valueize_refs_1 (lhs_ops, &valueized_anything);
        gcc_assert (lhs_ops == tem);
!       if (valueized_anything)
! 	{
! 	  lhs_ref_ok = ao_ref_init_from_vn_reference (&lhs_ref,
! 						      get_alias_set (lhs),
! 						      TREE_TYPE (lhs), lhs_ops);
! 	  if (lhs_ref_ok
! 	      && !refs_may_alias_p_1 (ref, &lhs_ref, true))
! 	    return NULL;
! 	}
!       else
! 	{
! 	  ao_ref_init (&lhs_ref, lhs);
! 	  lhs_ref_ok = true;
! 	}
      }
  
    base = ao_ref_base (ref);
*************** vn_reference_lookup_3 (ao_ref *ref, tree
*** 1469,1474 ****
--- 1479,1498 ----
  	  j--;
  	}
  
+       /* ???  The innermost op should always be a MEM_REF and we already
+          checked that the assignment to the lhs kills vr.  Thus for
+ 	 aggregate copies using char[] types the vn_reference_op_eq
+ 	 may fail when comparing types for compatibility.  But we really
+ 	 don't care here - further lookups with the rewritten operands
+ 	 will simply fail if we messed up types too badly.  */
+       if (j == 0 && i == 0
+ 	  && VEC_index (vn_reference_op_s, lhs_ops, 0)->opcode == MEM_REF
+ 	  && VEC_index (vn_reference_op_s, vr->operands, i)->opcode == MEM_REF
+ 	  && tree_int_cst_equal
+ 	       (VEC_index (vn_reference_op_s, lhs_ops, 0)->op0,
+ 		VEC_index (vn_reference_op_s, vr->operands, i)->op0))
+ 	i--, j--;
+ 
        /* i now points to the first additional op.
  	 ???  LHS may not be completely contained in VR, one or more
  	 VIEW_CONVERT_EXPRs could be in its way.  We could at least
Index: gcc/testsuite/g++.dg/tree-ssa/pr41186.C
===================================================================
*** gcc/testsuite/g++.dg/tree-ssa/pr41186.C	(revision 177649)
--- gcc/testsuite/g++.dg/tree-ssa/pr41186.C	(working copy)
***************
*** 1,5 ****
  /* { dg-do compile } */
! /* { dg-options "-O -fdump-tree-fre1-details" } */
  
  struct Foo {
    Foo() {};
--- 1,5 ----
  /* { dg-do compile } */
! /* { dg-options "-O -fno-tree-sra -fdump-tree-fre1-details" } */
  
  struct Foo {
    Foo() {};
*************** int main()
*** 30,35 ****
  }
  
  /* { dg-final { scan-tree-dump "Replaced b1.b with 1" "fre1" } } */
! /* { dg-final { scan-tree-dump "Replaced b1.i with 0" "fre1" { xfail *-*-* } } } */
! /* { dg-final { scan-tree-dump "Replaced b1.f with 1" "fre1" { xfail *-*-* } } } */
  /* { dg-final { cleanup-tree-dump "fre1" } } */
--- 30,35 ----
  }
  
  /* { dg-final { scan-tree-dump "Replaced b1.b with 1" "fre1" } } */
! /* { dg-final { scan-tree-dump "Replaced b1.D.\[0-9\]*.i with 0" "fre1" } } */
! /* { dg-final { scan-tree-dump "Replaced b1.D.\[0-9\]*.f with 1" "fre1" } } */
  /* { dg-final { cleanup-tree-dump "fre1" } } */

Re: [PATCH] Fix SCCVN aggregate copy code some more

[H.J. Lu]

On Thu, Aug 11, 2011 at 8:31 AM, Richard Guenther <rguenther@suse.de> wrote:
>
> When adjusting the C++ FE code generation for base type copies
> I noticed the XFAILs on g++.dg/tree-ssa/pr41186.C and investigated
> things a bit.  We can fix the testcase easily iff the frontend
> emits the MEM_REF variants, thus the following patch.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk.
>
> Richard.
>
> 2011-08-11  Richard Guenther  <rguenther@suse.de>
>
>         * tree-ssa-sccvn.c (vn_reference_lookup_3): Avoid redundant
>         lookups, make looking through aggregate copies stronger.
>

This caused:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54498

-- 
H.J.