[PATCH] Handle OBJ_TYPE_REF in FRE

[Jan Hubicka]

> 
> The following patch handles CSEing OBJ_TYPE_REF which was omitted
> because it is a GENERIC expression even on GIMPLE (for whatever

Why it is generic? It is part of gimple grammar :)

> reason...).  Rather than changing this now the following patch
> simply treats it properly as such.

Thanks for working on this! Will this do code motion, too?
I think you may want to compare the ODR type of obj_type_ref_class
otherwise two otherwise equivalent OBJ_TYPE_REFs may lead to different
optimizations later.  I suppose we can have code of form

if (test)
  OBJ_TYPE_REF1
  ...
else
  OBJ_TYPE_REF2
  ..
where each invoke method of different class type but would otherwise
match as equivalent for tree-ssa-sccvn becuase we ignore pointed-to types.

so doing

OBJ_TYPE_REF1
if (test)
  ...
else
  ...

may lead to wrong code.

Or do you just substitute the operands of OBJ_TYPE_REF? 
> 
> Bootstrap & regtest running on x86_64-unknown-linux-gnu.
> 
> Note that this does not (yet) substitute OBJ_TYPE_REFs in calls
> with SSA names that have the same value - not sure if that would
> be desired generally (does the devirt machinery cope with that?).

This should work fine.
> 
> Thanks,
> Richard.
> 
> 2015-12-03  Richard Biener  <rguenther@suse.de>
> 
> 	PR tree-optimization/64812
> 	* tree-ssa-sccvn.c (vn_get_stmt_kind): Handle OBJ_TYPE_REF.
> 	(vn_nary_length_from_stmt): Likewise.
> 	(init_vn_nary_op_from_stmt): Likewise.
> 	* gimple-match-head.c (maybe_build_generic_op): Likewise.
> 	* gimple-pretty-print.c (dump_unary_rhs): Likewise.
> 
> 	* g++.dg/tree-ssa/ssa-fre-1.C: New testcase.
> 
> Index: gcc/tree-ssa-sccvn.c
> ===================================================================
> *** gcc/tree-ssa-sccvn.c	(revision 231221)
> --- gcc/tree-ssa-sccvn.c	(working copy)
> *************** vn_get_stmt_kind (gimple *stmt)
> *** 460,465 ****
> --- 460,467 ----
>   			  ? VN_CONSTANT : VN_REFERENCE);
>   		else if (code == CONSTRUCTOR)
>   		  return VN_NARY;
> + 		else if (code == OBJ_TYPE_REF)
> + 		  return VN_NARY;
>   		return VN_NONE;
>   	      }
>   	  default:
> *************** vn_nary_length_from_stmt (gimple *stmt)
> *** 2479,2484 ****
> --- 2481,2487 ----
>         return 1;
>   
>       case BIT_FIELD_REF:
> +     case OBJ_TYPE_REF:
>         return 3;
>   
>       case CONSTRUCTOR:
> *************** init_vn_nary_op_from_stmt (vn_nary_op_t
> *** 2508,2513 ****
> --- 2511,2517 ----
>         break;
>   
>       case BIT_FIELD_REF:
> +     case OBJ_TYPE_REF:
>         vno->length = 3;
>         vno->op[0] = TREE_OPERAND (gimple_assign_rhs1 (stmt), 0);
>         vno->op[1] = TREE_OPERAND (gimple_assign_rhs1 (stmt), 1);
> Index: gcc/gimple-match-head.c
> ===================================================================
> *** gcc/gimple-match-head.c	(revision 231221)
> --- gcc/gimple-match-head.c	(working copy)
> *************** maybe_build_generic_op (enum tree_code c
> *** 243,248 ****
> --- 243,249 ----
>         *op0 = build1 (code, type, *op0);
>         break;
>       case BIT_FIELD_REF:
> +     case OBJ_TYPE_REF:
>         *op0 = build3 (code, type, *op0, op1, op2);
>         break;
>       default:;
> Index: gcc/gimple-pretty-print.c
> ===================================================================
> *** gcc/gimple-pretty-print.c	(revision 231221)
> --- gcc/gimple-pretty-print.c	(working copy)
> *************** dump_unary_rhs (pretty_printer *buffer,
> *** 302,308 ****
>   	  || TREE_CODE_CLASS (rhs_code) == tcc_reference
>   	  || rhs_code == SSA_NAME
>   	  || rhs_code == ADDR_EXPR
> ! 	  || rhs_code == CONSTRUCTOR)
>   	{
>   	  dump_generic_node (buffer, rhs, spc, flags, false);
>   	  break;
> --- 302,309 ----
>   	  || TREE_CODE_CLASS (rhs_code) == tcc_reference
>   	  || rhs_code == SSA_NAME
>   	  || rhs_code == ADDR_EXPR
> ! 	  || rhs_code == CONSTRUCTOR
> ! 	  || rhs_code == OBJ_TYPE_REF)
>   	{
>   	  dump_generic_node (buffer, rhs, spc, flags, false);
>   	  break;
> Index: gcc/testsuite/g++.dg/tree-ssa/ssa-fre-1.C
> ===================================================================
> *** gcc/testsuite/g++.dg/tree-ssa/ssa-fre-1.C	(revision 0)
> --- gcc/testsuite/g++.dg/tree-ssa/ssa-fre-1.C	(working copy)
> ***************
> *** 0 ****
> --- 1,44 ----
> + /* { dg-do compile } */
> + /* { dg-options "-O2 -fdump-tree-fre2" } */
> + 
> + template <class T> class A
> + {
> +   T *p;
> + 
> + public:
> +   A (T *p1) : p (p1) { p->acquire (); }
> + };
> + 
> + class B
> + {
> + public:
> +     virtual void acquire ();
> + };
> + class D : public B
> + {
> + };
> + class F : B
> + {
> +   int mrContext;
> + };
> + class WindowListenerMultiplexer : F, public D
> + {
> +   void acquire () { acquire (); }
> + };
> + class C
> + {
> +   void createPeer () throw ();
> +   WindowListenerMultiplexer maWindowListeners;
> + };
> + class FmXGridPeer
> + {
> + public:
> +     void addWindowListener (A<D>);
> + } a;
> + void
> + C::createPeer () throw ()
> + {
> +   a.addWindowListener (&maWindowListeners);
> + }
> + 
> + /* { dg-final { scan-tree-dump-times "= OBJ_TYPE_REF" 1 "fre2" } } */