Use CLEANUP_POINT_EXPR for auto-destructing temporaries.

Author: ibuclaw

gcc/d/ChangeLog

@@ -1,3 +1,27 @@
+2017-12-19  Iain Buclaw  <[email protected]>
+
+	* d-codegen.cc (build_target_expr): Update signature.
+	(force_target_expr): New function.
+	(build_address): Use force_target_expr to store temporary.
+	(d_build_call): Likewise.
+	* d-lang.cc (d_gimplify_expr): Likewise.
+	* d-tree.h (language_function): Update type for vars_in_scope from
+	vec<VarDeclaration*> to vec<tree>.
+	(force_target_expr): Declare.
+	* decl.cc (DeclVisitor::visit(VarDeclaration)): Put vars with scope
+	destructors into a TARGET_EXPR, setting its cleanup.
+	(declare_local_var): Don't push vars with scope destructors into the
+	function binding level.
+	* expr.cc (ExprVisitor::visit(DeclarationExp)): Don't handle scope
+	destructors.
+	(ExprVisitor::visit(CallExp)): Handle calling constructors using
+	temporary objects.
+	(build_dtor_list): Remove function.
+	(build_expr_dtor): Put result into a CLEANUP_POINT_EXPR if any new
+	temporaries needing destruction were added to scope.
+	(build_return_dtor): Likewise.
+	* toir.cc (add_stmt): Set CLEANUP_POINT_EXPR type as void.
+
 2017-12-19  Iain Buclaw  <[email protected]>
 
 	* d-attribs.c (attr_noreturn_exclusions): New array.

gcc/d/d-codegen.cc

@@ -545,21 +545,20 @@ stabilize_expr (tree *valuep)
     }
 }
 
-/* Return a TARGET_EXPR using EXP to initialize a new temporary.  */
+/* Return a TARGET_EXPR, initializing the DECL with EXP.  */
 
 tree
-build_target_expr (tree exp)
+build_target_expr (tree decl, tree exp)
 {
-  tree type = TREE_TYPE (exp);
-  tree slot = create_temporary_var (type);
-  tree result = build4 (TARGET_EXPR, type, slot, exp, NULL_TREE, NULL_TREE);
+  tree type = TREE_TYPE (decl);
+  tree result = build4 (TARGET_EXPR, type, decl, exp, NULL_TREE, NULL_TREE);
 
   if (EXPR_HAS_LOCATION (exp))
     SET_EXPR_LOCATION (result, EXPR_LOCATION (exp));
 
-  /* If slot must always reside in memory.  */
+  /* If decl must always reside in memory.  */
   if (TREE_ADDRESSABLE (type))
-    d_mark_addressable (slot);
+    d_mark_addressable (decl);
 
   /* Always set TREE_SIDE_EFFECTS so that expand_expr does not ignore the
      TARGET_EXPR.  If there really turn out to be no side effects, then the
@@ -569,6 +568,16 @@ build_target_expr (tree exp)
   return result;
 }
 
+/* Like the above function, but initializes a new temporary.  */
+
+tree
+force_target_expr (tree exp)
+{
+  tree decl = create_temporary_var (TREE_TYPE (exp));
+
+  return build_target_expr (decl, exp);
+}
+
 /* Returns the address of the expression EXP.  */
 
 tree
@@ -606,7 +615,7 @@ build_address (tree exp)
   /* Some expression lowering may request an address of a compile-time constant.
      Make sure it is assigned to a location we can reference.  */
   if (CONSTANT_CLASS_P (exp) && TREE_CODE (exp) != STRING_CST)
-    exp = build_target_expr (exp);
+    exp = force_target_expr (exp);
 
   d_mark_addressable (exp);
   exp = build_fold_addr_expr_with_type_loc (input_location, exp, ptrtype);
@@ -2004,7 +2013,7 @@ d_build_call (TypeFunction *tf, tree callable, tree object,
       && TREE_ADDRESSABLE (TREE_TYPE (result)))
     {
       CALL_EXPR_RETURN_SLOT_OPT (result) = true;
-      result = build_target_expr (result);
+      result = force_target_expr (result);
     }
 
   return compound_expr (saved_args, result);

gcc/d/d-lang.cc

@@ -851,7 +851,7 @@ d_gimplify_expr (tree *expr_p, gimple_seq *pre_p,
       /* Constructors are not lvalues, so make them one.  */
       if (TREE_CODE (op0) == CONSTRUCTOR)
 	{
-	  TREE_OPERAND (*expr_p, 0) = build_target_expr (op0);
+	  TREE_OPERAND (*expr_p, 0) = force_target_expr (op0);
 	  ret = GS_OK;
 	}
       break;

gcc/d/d-tree.h

@@ -233,7 +233,7 @@ struct GTY(()) language_function
   vec<tree, va_gc> *stmt_list;
 
   /* Variables that are in scope that will need destruction later.  */
-  vec<VarDeclaration *> GTY((skip)) vars_in_scope;
+  vec<tree, va_gc> *vars_in_scope;
 
   /* Table of all used or defined labels in the function.  */
   hash_map<Statement *, d_label_entry> *labels;
@@ -502,7 +502,8 @@ extern void extract_from_method_call (tree, tree &, tree &);
 extern tree build_vindex_ref (tree, tree, size_t);
 extern tree d_save_expr (tree);
 extern tree stabilize_expr (tree *);
-extern tree build_target_expr (tree);
+extern tree build_target_expr (tree, tree);
+extern tree force_target_expr (tree);
 extern tree build_address (tree);
 extern tree d_mark_addressable (tree);
 extern tree d_mark_used (tree);

gcc/d/decl.cc

@@ -627,6 +627,22 @@ class DeclVisitor : public Visitor
 		ExpInitializer *vinit = d->_init->isExpInitializer ();
 		Expression *ie = initializerToExpression (vinit);
 		tree exp = build_expr (ie);
+
+		/* Maybe put variable on list of things needing destruction.  */
+		if (d->needsScopeDtor ())
+		  {
+		    /* Its a temporary, add the corresponding cleanup.  */
+		    tree decl = get_symbol_decl (d);
+		    vec_safe_push (d_function_chain->vars_in_scope, decl);
+
+		    if (TREE_CODE (exp) == INIT_EXPR
+			|| TREE_CODE (exp) == MODIFY_EXPR)
+		      exp = TREE_OPERAND (exp, 1);
+
+		    exp = build_target_expr (decl, exp);
+		    TARGET_EXPR_CLEANUP (exp) = build_expr (d->edtor);
+		  }
+
 		add_stmt (exp);
 	      }
 	    else if (d->size (d->loc) != 0)
@@ -1295,7 +1311,12 @@ declare_local_var (VarDeclaration *var)
 
   gcc_assert (!TREE_STATIC (decl));
 
-  d_pushdecl (decl);
+  /* If this is a variable used for automatic scope dtor, don't add it to the
+     current binding level, as its really a temporary used in a TARGET_EXPR.
+     See build_decl_tree visitor for VarDeclaration.  */
+  if (!var->needsScopeDtor ())
+    d_pushdecl (decl);
+
   DECL_CONTEXT (decl) = current_function_decl;
 
   /* Compiler generated symbols.  */

gcc/d/expr.cc

@@ -1695,6 +1695,7 @@ class ExprVisitor : public Visitor
 
     tree callee = NULL_TREE;
     tree object = NULL_TREE;
+    tree cleanup = NULL_TREE;
     TypeFunction *tf = NULL;
 
     /* Calls to delegates can sometimes look like this.  */
@@ -1732,6 +1733,19 @@ class ExprVisitor : public Visitor
 	      {
 		tree thisexp = build_expr (dve->e1);
 
+		/* When constructing temporaries, if the constructor throws,
+		   then the object is destructed even though it is not a fully
+		   constructed object yet.  And so this call will need to be
+		   moved inside the TARGET_EXPR_INITIAL slot.  */
+		if (fd->isCtorDeclaration ()
+		    && TREE_CODE (thisexp) == COMPOUND_EXPR
+		    && TREE_CODE (TREE_OPERAND (thisexp, 0)) == TARGET_EXPR
+		    && TARGET_EXPR_CLEANUP (TREE_OPERAND (thisexp, 0)))
+		  {
+		    cleanup = TREE_OPERAND (thisexp, 0);
+		    thisexp = TREE_OPERAND (thisexp, 1);
+		  }
+
 		/* Want reference to 'this' object.  */
 		if (!POINTER_TYPE_P (TREE_TYPE (thisexp)))
 		  thisexp = build_address (thisexp);
@@ -1820,6 +1834,20 @@ class ExprVisitor : public Visitor
     if (e->type->isTypeBasic ())
       exp = d_convert (build_ctype (e->type), exp);
 
+    /* If this call was found to be a constructor for a temporary with a
+       cleanup, then move the call inside the TARGET_EXPR.  The original
+       initializer is turned into an assignment, to keep its side effect.  */
+    if (cleanup != NULL_TREE)
+      {
+	tree init = TARGET_EXPR_INITIAL (cleanup);
+	tree slot = TARGET_EXPR_SLOT (cleanup);
+	d_mark_addressable (slot);
+	init = build_assign (INIT_EXPR, slot, init);
+
+	TARGET_EXPR_INITIAL (cleanup) = compound_expr (init, exp);
+	exp = cleanup;
+      }
+
     this->result_ = exp;
   }
 
@@ -2013,22 +2041,9 @@ class ExprVisitor : public Visitor
        can cause an empty STMT_LIST here.  This can causes problems
        during gimplification.  */
     if (TREE_CODE (result) == STATEMENT_LIST && !STATEMENT_LIST_HEAD (result))
-      this->result_ = build_empty_stmt (input_location);
-    else
-      this->result_ = result;
-
-    /* Maybe put variable on list of things needing destruction.  */
-    VarDeclaration *vd = e->declaration->isVarDeclaration ();
-    if (vd != NULL)
-      {
-	if (!vd->isStatic () && !(vd->storage_class & STCmanifest)
-	    && !(vd->storage_class & (STCextern | STCtls | STCgshared)))
-	  {
-	    if (vd->needsScopeDtor ())
-	      d_function_chain->vars_in_scope.safe_push (vd);
-	  }
-      }
+      result = build_empty_stmt (input_location);
 
+    this->result_ = result;
   }
 
   /* Build a typeid expression.  Returns an instance of class TypeInfo
@@ -3039,86 +3054,20 @@ build_expr (Expression *e, bool const_p)
   return expr;
 }
 
-/* Build an expression that calls the destructors on all the variables
-   going out of the scope between STARTI and ENDI. All destructors are
-   executed in reverse order.  */
-
-static tree
-build_dtor_list (size_t starti, size_t endi)
-{
-  tree dtors = NULL_TREE;
-
-  for (size_t i = starti; i != endi; ++i)
-    {
-      VarDeclaration *vd = d_function_chain->vars_in_scope[i];
-      if (vd)
-	{
-	  d_function_chain->vars_in_scope[i] = NULL;
-	  tree t = build_expr (vd->edtor);
-	  dtors = compound_expr (t, dtors);
-	}
-    }
-
-  return dtors;
-}
-
 /* Same as build_expr, but also calls destructors on any temporaries.  */
 
 tree
 build_expr_dtor (Expression *e)
 {
   /* Codegen can be improved by determining if no exceptions can be thrown
      between the ctor and dtor, and eliminating the ctor and dtor.  */
-  size_t starti = d_function_chain->vars_in_scope.length ();
+  size_t saved_vars = vec_safe_length (d_function_chain->vars_in_scope);
   tree result = build_expr (e);
-  size_t endi = d_function_chain->vars_in_scope.length ();
 
-  tree dtors = build_dtor_list (starti, endi);
-
-  if (dtors != NULL_TREE)
+  if (saved_vars != vec_safe_length (d_function_chain->vars_in_scope))
     {
-      /* Split comma expressions, so that only the result is maybe saved.  */
-      tree expr = stabilize_expr (&result);
-
-      /* When constructing temporaries, if the constructor throws, then
-	 we don't want to run the destructor on the incomplete object.  */
-      CallExp *ce = (e->op == TOKcall) ? ((CallExp *) e) : NULL;
-      if (ce != NULL && ce->e1->op == TOKdotvar
-	  && ((DotVarExp *) ce->e1)->var->isCtorDeclaration ())
-	{
-	  /* Extract the object from the ctor call, as it will be the same
-	     value as the returned result, just maybe without the side effects.
-	     Rewriting: ctor (&e1) => (ctor (&e1), e1)  */
-	  expr = compound_expr (expr, result);
-
-	  if (INDIRECT_REF_P (result))
-	    result = build_deref (CALL_EXPR_ARG (TREE_OPERAND (result, 0), 0));
-	  else
-	    result = CALL_EXPR_ARG (result, 0);
-
-	  return compound_expr (compound_expr (expr, dtors), result);
-	}
-
-      /* Extract the LHS from the assignment expression.
-	 Rewriting: (e1 = e2) => ((e1 = e2), e1)  */
-      if (TREE_CODE (result) == INIT_EXPR || TREE_CODE (result) == MODIFY_EXPR)
-	{
-	  expr = compound_expr (expr, result);
-	  result = TREE_OPERAND (result, 0);
-	}
-
-      /* If the result has side-effects, save the entire expression.  */
-      if (TREE_SIDE_EFFECTS (result))
-	{
-	  /* Wrap expr and dtors in a try/finally expression.  */
-	  result = d_save_expr (result);
-	  expr = build2 (TRY_FINALLY_EXPR, void_type_node,
-			compound_expr (expr, result), dtors);
-	}
-      else
-	expr = compound_expr (expr, dtors);
-
-      return compound_expr (expr, result);
+      result = fold_build_cleanup_point_expr (TREE_TYPE (result), result);
+      vec_safe_truncate (d_function_chain->vars_in_scope, saved_vars);
     }
 
   return result;
@@ -3129,13 +3078,11 @@ build_expr_dtor (Expression *e)
 tree
 build_return_dtor (Expression *e, Type *type, TypeFunction *tf)
 {
-  size_t starti = d_function_chain->vars_in_scope.length ();
+  size_t saved_vars = vec_safe_length (d_function_chain->vars_in_scope);
   tree result = build_expr (e);
-  size_t endi = d_function_chain->vars_in_scope.length ();
 
   /* Convert for initialising the DECL_RESULT.  */
   result = convert_expr (result, e->type, type);
-  tree dtors = build_dtor_list (starti, endi);
 
   /* If we are returning a reference, take the address.  */
   if (tf->isref)
@@ -3149,9 +3096,12 @@ build_return_dtor (Expression *e, Type *type, TypeFunction *tf)
   result = build_assign (INIT_EXPR, decl, result);
   result = compound_expr (expr, return_expr (result));
 
-  /* Nest the return expression inside the try/finally expression.  */
-  if (dtors != NULL_TREE)
-    return build2 (TRY_FINALLY_EXPR, void_type_node, result, dtors);
+  /* May nest the return expression inside the try/finally expression.  */
+  if (saved_vars != vec_safe_length (d_function_chain->vars_in_scope))
+    {
+      result = fold_build_cleanup_point_expr (TREE_TYPE (result), result);
+      vec_safe_truncate (d_function_chain->vars_in_scope, saved_vars);
+    }
 
   return result;
 }

gcc/d/toir.cc

@@ -205,6 +205,11 @@ add_stmt (tree t)
     }
   else
     {
+      /* Force the type to be void so we don't need to create a temporary
+	 variable to hold the inner expression.  */
+      if (TREE_CODE (t) == CLEANUP_POINT_EXPR)
+	TREE_TYPE (t) = void_type_node;
+
       /* Append the expression to the statement list.
 	 Make sure it has a proper location.  */
       if (EXPR_P (t) && !EXPR_HAS_LOCATION (t))

gcc/testsuite/gdc.test/runnable/test14903.d

@@ -75,7 +75,7 @@ void dtorsTest() {
         assert(0);
     } catch (Exception) {}
     assert(counter == 1);
-    //assert(StructWithDtor.numDtor == 1); // XGDC
+    assert(StructWithDtor.numDtor == 1);
 
     // TODO: test exception chaining with throwing dtors
 }