re PR c++/8781 (Pessimization of C++ (functional) code)

2009-04-04  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/8781
	PR tree-optimization/37892
	* tree-ssa-sccvn.h (vn_reference_fold_indirect): Declare.
	* tree-ssa-sccvn.c (vn_reference_fold_indirect): New function.
	(valueize_refs): Call it for *& valueizations.
	(shared_reference_ops_from_ref): Rename to ...
	(valueize_shared_reference_ops_from_ref): ... this and valueize.
	(shared_reference_ops_from_call): Rename to ...
	(valueize_shared_reference_ops_from_call): ... this and valueize.
	(vn_reference_lookup): Update.
	(visit_reference_op_call): Likewise.
	* tree-ssa-pre.c (phi_translate_1): Fold *&.
	(eliminate): Value-replace the call address in call statements.

	* g++.dg/tree-ssa/pr8781.C: New testcase.
	* gcc.dg/tree-ssa/ssa-pre-25.c: Likewise.

From-SVN: r145533

7 files changed, 196 insertions, 35 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 18fb789..69fbfd5 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,21 @@
 2009-04-04  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/8781
+	PR tree-optimization/37892
+	* tree-ssa-sccvn.h (vn_reference_fold_indirect): Declare.
+	* tree-ssa-sccvn.c (vn_reference_fold_indirect): New function.
+	(valueize_refs): Call it for *& valueizations.
+	(shared_reference_ops_from_ref): Rename to ...
+	(valueize_shared_reference_ops_from_ref): ... this and valueize.
+	(shared_reference_ops_from_call): Rename to ...
+	(valueize_shared_reference_ops_from_call): ... this and valueize.
+	(vn_reference_lookup): Update.
+	(visit_reference_op_call): Likewise.
+	* tree-ssa-pre.c (phi_translate_1): Fold *&.
+	(eliminate): Value-replace the call address in call statements.
+
+2009-04-04  Richard Guenther  <rguenther@suse.de>
+
 	PR tree-optimization/39636
 	* tree-ssa-forwprop.c
 	(forward_propagate_addr_into_variable_array_index): Check for
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 3e322f5..8289452 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,12 @@
 2009-04-04  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/8781
+	PR tree-optimization/37892
+	* g++.dg/tree-ssa/pr8781.C: New testcase.
+	* gcc.dg/tree-ssa/ssa-pre-25.c: Likewise.
+
+2009-04-04  Richard Guenther  <rguenther@suse.de>
+
 	PR tree-optimization/39636
 	* gcc.c-torture/compile/pr39636.c: New testcase.
 
diff --git a/gcc/testsuite/g++.dg/tree-ssa/pr8781.C b/gcc/testsuite/g++.dg/tree-ssa/pr8781.C
new file mode 100644
index 0000000..a9d279a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tree-ssa/pr8781.C
@@ -0,0 +1,28 @@
+/* { dg-do compile } */
+/* { dg-options "-O -fdump-tree-fre-details" } */
+
+int f();
+
+template<typename predicate>
+class noop_t {
+    const predicate &pred;
+public:
+    explicit noop_t(const predicate &p) : pred(p) {}
+
+    int operator()() const { return pred(); }
+};
+
+template<typename predicate>
+inline noop_t<predicate> noop(const predicate pred) {
+    return noop_t<predicate>(pred);
+}
+
+int x()
+{
+  return (noop(noop(noop(noop(noop(noop(noop(noop(noop(f)))))))))());
+}
+
+/* We should optimize this to a direct call.  */
+
+/* { dg-final { scan-tree-dump "Replacing call target with f" "fre" } } */
+/* { dg-final { cleanup-tree-dump "fre" } } */
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-25.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-25.c
new file mode 100644
index 0000000..32b0682
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-pre-25.c
@@ -0,0 +1,23 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-pre-stats" } */
+
+struct X { int i; };
+
+int foo (int x)
+{
+  struct X a;
+  struct X b;
+  struct X *p;
+  a.i = 1;
+  b.i = 2;
+  if (x)
+    p = &a;
+  else
+    p = &b;
+  return p->i;
+}
+
+/* We should eliminate the load from p for a PHI node with values 1 and 2.  */
+
+/* { dg-final { scan-tree-dump "Eliminated: 1" "pre" } } */
+/* { dg-final { cleanup-tree-dump "pre" } } */
diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index c1cbe0c..ed326e4 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -1563,11 +1563,12 @@ phi_translate_1 (pre_expr expr, bitmap_set_t set1, bitmap_set_t set2,
 	tree newvuse = vuse;
 	VEC (vn_reference_op_s, heap) *newoperands = NULL;
 	bool changed = false;
-	unsigned int i;
+	unsigned int i, j;
 	vn_reference_op_t operand;
 	vn_reference_t newref;
 
-	for (i = 0; VEC_iterate (vn_reference_op_s, operands, i, operand); i++)
+	for (i = 0, j = 0;
+	     VEC_iterate (vn_reference_op_s, operands, i, operand); i++, j++)
 	  {
 	    pre_expr opresult;
 	    pre_expr leader;
@@ -1642,7 +1643,13 @@ phi_translate_1 (pre_expr expr, bitmap_set_t set1, bitmap_set_t set2,
 	    newop.op0 = op0;
 	    newop.op1 = op1;
 	    newop.op2 = op2;
-	    VEC_replace (vn_reference_op_s, newoperands, i, &newop);
+	    VEC_replace (vn_reference_op_s, newoperands, j, &newop);
+	    /* If it transforms from an SSA_NAME to an address, fold with
+	       a preceding indirect reference.  */
+	    if (j > 0 && op0 && TREE_CODE (op0) == ADDR_EXPR
+		&& VEC_index (vn_reference_op_s,
+			      newoperands, j - 1)->opcode == INDIRECT_REF)
+	      vn_reference_fold_indirect (&newoperands, &j);
 	  }
 	if (i != VEC_length (vn_reference_op_s, operands))
 	  {
@@ -4098,6 +4105,29 @@ eliminate (void)
 		  todo = TODO_cleanup_cfg;
 		}
 	    }
+	  /* Visit indirect calls and turn them into direct calls if
+	     possible.  */
+	  if (gimple_code (stmt) == GIMPLE_CALL
+	      && TREE_CODE (gimple_call_fn (stmt)) == SSA_NAME)
+	    {
+	      tree fn = VN_INFO (gimple_call_fn (stmt))->valnum;
+	      if (TREE_CODE (fn) == ADDR_EXPR
+		  && TREE_CODE (TREE_OPERAND (fn, 0)) == FUNCTION_DECL)
+		{
+		  if (dump_file && (dump_flags & TDF_DETAILS))
+		    {
+		      fprintf (dump_file, "Replacing call target with ");
+		      print_generic_expr (dump_file, fn, 0);
+		      fprintf (dump_file, " in ");
+		      print_gimple_stmt (dump_file, stmt, 0, 0);
+		    }
+
+		  gimple_call_set_fn (stmt, fn);
+		  update_stmt (stmt);
+		  if (maybe_clean_or_replace_eh_stmt (stmt, stmt))
+		    gimple_purge_dead_eh_edges (b);
+		}
+	    }
 	}
     }
 
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c
index 8abc306..729787b 100644
--- a/gcc/tree-ssa-sccvn.c
+++ b/gcc/tree-ssa-sccvn.c
@@ -744,36 +744,52 @@ create_reference_ops_from_call (gimple call)
   return result;
 }
 
-static VEC(vn_reference_op_s, heap) *shared_lookup_references;
-
-/* Create a vector of vn_reference_op_s structures from REF, a
-   REFERENCE_CLASS_P tree.  The vector is shared among all callers of
-   this function.  */
-
-static VEC(vn_reference_op_s, heap) *
-shared_reference_ops_from_ref (tree ref)
+/* Fold *& at position *I_P in a vn_reference_op_s vector *OPS.  Updates
+   *I_P to point to the last element of the replacement.  */
+void
+vn_reference_fold_indirect (VEC (vn_reference_op_s, heap) **ops,
+			    unsigned int *i_p)
 {
-  if (!ref)
-    return NULL;
-  VEC_truncate (vn_reference_op_s, shared_lookup_references, 0);
-  copy_reference_ops_from_ref (ref, &shared_lookup_references);
-  return shared_lookup_references;
-}
+  VEC(vn_reference_op_s, heap) *mem = NULL;
+  vn_reference_op_t op;
+  unsigned int i = *i_p;
+  unsigned int j;
 
-/* Create a vector of vn_reference_op_s structures from CALL, a
-   call statement.  The vector is shared among all callers of
-   this function.  */
+  /* Get ops for the addressed object.  */
+  op = VEC_index (vn_reference_op_s, *ops, i);
+  copy_reference_ops_from_ref (TREE_OPERAND (op->op0, 0), &mem);
 
-static VEC(vn_reference_op_s, heap) *
-shared_reference_ops_from_call (gimple call)
-{
-  if (!call)
-    return NULL;
-  VEC_truncate (vn_reference_op_s, shared_lookup_references, 0);
-  copy_reference_ops_from_call (call, &shared_lookup_references);
-  return shared_lookup_references;
-}
+  /* Do the replacement - we should have at least one op in mem now.  */
+  if (VEC_length (vn_reference_op_s, mem) == 1)
+    {
+      VEC_replace (vn_reference_op_s, *ops, i - 1,
+		   VEC_index (vn_reference_op_s, mem, 0));
+      VEC_ordered_remove (vn_reference_op_s, *ops, i);
+      i--;
+    }
+  else if (VEC_length (vn_reference_op_s, mem) == 2)
+    {
+      VEC_replace (vn_reference_op_s, *ops, i - 1,
+		   VEC_index (vn_reference_op_s, mem, 0));
+      VEC_replace (vn_reference_op_s, *ops, i,
+		   VEC_index (vn_reference_op_s, mem, 1));
+    }
+  else if (VEC_length (vn_reference_op_s, mem) > 2)
+    {
+      VEC_replace (vn_reference_op_s, *ops, i - 1,
+		   VEC_index (vn_reference_op_s, mem, 0));
+      VEC_replace (vn_reference_op_s, *ops, i,
+		   VEC_index (vn_reference_op_s, mem, 1));
+      /* ???  There is no VEC_splice.  */
+      for (j = 2; VEC_iterate (vn_reference_op_s, mem, j, op); j++)
+	VEC_safe_insert (vn_reference_op_s, heap, *ops, ++i, op);
+    }
+  else
+    gcc_unreachable ();
 
+  VEC_free (vn_reference_op_s, heap, mem);
+  *i_p = i;
+}
 
 /* Transform any SSA_NAME's in a vector of vn_reference_op_s
    structures into their value numbers.  This is done in-place, and
@@ -783,7 +799,7 @@ static VEC (vn_reference_op_s, heap) *
 valueize_refs (VEC (vn_reference_op_s, heap) *orig)
 {
   vn_reference_op_t vro;
-  int i;
+  unsigned int i;
 
   for (i = 0; VEC_iterate (vn_reference_op_s, orig, i, vro); i++)
     {
@@ -795,15 +811,54 @@ valueize_refs (VEC (vn_reference_op_s, heap) *orig)
 	     the opcode.  */
 	  if (TREE_CODE (vro->op0) != SSA_NAME && vro->opcode == SSA_NAME)
 	    vro->opcode = TREE_CODE (vro->op0);
+	  /* If it transforms from an SSA_NAME to an address, fold with
+	     a preceding indirect reference.  */
+	  if (i > 0 && TREE_CODE (vro->op0) == ADDR_EXPR
+	      && VEC_index (vn_reference_op_s,
+			    orig, i - 1)->opcode == INDIRECT_REF)
+	    vn_reference_fold_indirect (&orig, &i);
 	}
-      /* TODO: Do we want to valueize op2 and op1 of
-	 ARRAY_REF/COMPONENT_REF for Ada */
-      
+      if (vro->op1 && TREE_CODE (vro->op1) == SSA_NAME)
+	vro->op1 = SSA_VAL (vro->op1);
+      if (vro->op2 && TREE_CODE (vro->op2) == SSA_NAME)
+	vro->op2 = SSA_VAL (vro->op2);
     }
 
   return orig;
 }
 
+static VEC(vn_reference_op_s, heap) *shared_lookup_references;
+
+/* Create a vector of vn_reference_op_s structures from REF, a
+   REFERENCE_CLASS_P tree.  The vector is shared among all callers of
+   this function.  */
+
+static VEC(vn_reference_op_s, heap) *
+valueize_shared_reference_ops_from_ref (tree ref)
+{
+  if (!ref)
+    return NULL;
+  VEC_truncate (vn_reference_op_s, shared_lookup_references, 0);
+  copy_reference_ops_from_ref (ref, &shared_lookup_references);
+  shared_lookup_references = valueize_refs (shared_lookup_references);
+  return shared_lookup_references;
+}
+
+/* Create a vector of vn_reference_op_s structures from CALL, a
+   call statement.  The vector is shared among all callers of
+   this function.  */
+
+static VEC(vn_reference_op_s, heap) *
+valueize_shared_reference_ops_from_call (gimple call)
+{
+  if (!call)
+    return NULL;
+  VEC_truncate (vn_reference_op_s, shared_lookup_references, 0);
+  copy_reference_ops_from_call (call, &shared_lookup_references);
+  shared_lookup_references = valueize_refs (shared_lookup_references);
+  return shared_lookup_references;
+}
+
 /* Lookup a SCCVN reference operation VR in the current hash table.
    Returns the resulting value number if it exists in the hash table,
    NULL_TREE otherwise.  VNRESULT will be filled in with the actual
@@ -914,7 +969,7 @@ vn_reference_lookup (tree op, tree vuse, bool maywalk,
     *vnresult = NULL;
 
   vr1.vuse = vuse ? SSA_VAL (vuse) : NULL_TREE;
-  vr1.operands = valueize_refs (shared_reference_ops_from_ref (op));
+  vr1.operands = valueize_shared_reference_ops_from_ref (op);
   vr1.hashcode = vn_reference_compute_hash (&vr1);
 
   if (maywalk
@@ -1585,7 +1640,7 @@ visit_reference_op_call (tree lhs, gimple stmt)
   tree vuse = gimple_vuse (stmt);
 
   vr1.vuse = vuse ? SSA_VAL (vuse) : NULL_TREE;
-  vr1.operands = valueize_refs (shared_reference_ops_from_call (stmt));
+  vr1.operands = valueize_shared_reference_ops_from_call (stmt);
   vr1.hashcode = vn_reference_compute_hash (&vr1);
   result = vn_reference_lookup_1 (&vr1, NULL);
   if (result)
diff --git a/gcc/tree-ssa-sccvn.h b/gcc/tree-ssa-sccvn.h
index 644bc12..c8171c2 100644
--- a/gcc/tree-ssa-sccvn.h
+++ b/gcc/tree-ssa-sccvn.h
@@ -173,6 +173,8 @@ vn_nary_op_t vn_nary_op_insert_stmt (gimple, tree);
 vn_nary_op_t vn_nary_op_insert_pieces (unsigned int, enum tree_code,
 				       tree, tree, tree, tree,
 				       tree, tree, unsigned int);
+void vn_reference_fold_indirect (VEC (vn_reference_op_s, heap) **,
+				 unsigned int *);
 void copy_reference_ops_from_ref (tree, VEC(vn_reference_op_s, heap) **);
 void copy_reference_ops_from_call (gimple, VEC(vn_reference_op_s, heap) **);
 tree get_ref_from_reference_ops (VEC(vn_reference_op_s, heap) *ops);