[Ada] Fix discrepancy in annotated vs computed sizes

[Eric Botcazou <ebotcazou at adacore dot com>]

This fixes the discrepancy present in annotated vs computed sizes for objects 
either directly subject to an alignment clause or of a type itself subject to 
an alignment clause.  In the former case, the annotated size can be wrong 
whereas the computed size can be wrong in the latter case.

Tested on x86_64-suse-linux, applied on the mainline.


2017-12-14  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/gigi.h (pad_type_has_rm_size): Declare.
	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Variable>: Do notbuild
	a padding type for the alignment before validating the size.
	Flip conditional construct and add a comment.
	* gcc-interface/trans.c (Attribute_to_gnu) <Attr_Size>: Make sure to
	apply the exception for padded objects to the type of the object.
	* gcc-interface/utils.c (hash_pad_type): New static function.
	(lookup_and_insert_pad_type): Rename into...
	(canonicalize_pad_type): ...this.  Call hash_pad_type, do only one
	lookup with insertion and always return the canonical type.
	(maybe_pad_type): Adjust to above changes.  Set debug type later.
	(pad_type_has_rm_size): New predicate.
	(set_reverse_storage_order_on_pad_type): Adjust to above changes.


2017-12-14  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/alignment11.adb: New test.
	* gnat.dg/alignment12.adb: Likewise.

-- 
Eric Botcazou

Index: gcc-interface/decl.c
===================================================================
--- gcc-interface/decl.c	(revision 255622)
+++ gcc-interface/decl.c	(working copy)
@@ -713,48 +713,20 @@ gnat_to_gnu_entity (Entity_Id gnat_entit
 	  }
 
 	/* If an alignment is specified, use it if valid.  Note that exceptions
-	   are objects but don't have an alignment.  We must do this before we
-	   validate the size, since the alignment can affect the size.  */
-	if (kind != E_Exception && Known_Alignment (gnat_entity))
-	  {
-	    gcc_assert (Present (Alignment (gnat_entity)));
-
-	    align = validate_alignment (Alignment (gnat_entity), gnat_entity,
-					TYPE_ALIGN (gnu_type));
-
-	    /* No point in changing the type if there is an address clause
-	       as the final type of the object will be a reference type.  */
-	    if (Present (Address_Clause (gnat_entity)))
-	      align = 0;
-	    else
-	      {
-		tree orig_type = gnu_type;
-
-		gnu_type
-		  = maybe_pad_type (gnu_type, NULL_TREE, align, gnat_entity,
-				    false, false, definition, true);
-
-		/* If a padding record was made, declare it now since it will
-		   never be declared otherwise.  This is necessary to ensure
-		   that its subtrees are properly marked.  */
-		if (gnu_type != orig_type && !DECL_P (TYPE_NAME (gnu_type)))
-		  create_type_decl (TYPE_NAME (gnu_type), gnu_type, true,
-				    debug_info_p, gnat_entity);
-	      }
-	  }
-
-	/* If we are defining the object, see if it has a Size and validate it
-	   if so.  If we are not defining the object and a Size clause applies,
-	   simply retrieve the value.  We don't want to ignore the clause and
-	   it is expected to have been validated already.  Then get the new
-	   type, if any.  */
-	if (definition)
-	  gnu_size = validate_size (Esize (gnat_entity), gnu_type,
-				    gnat_entity, VAR_DECL, false,
-				    Has_Size_Clause (gnat_entity));
-	else if (Has_Size_Clause (gnat_entity))
-	  gnu_size = UI_To_gnu (Esize (gnat_entity), bitsizetype);
+	   are objects but don't have an alignment and there is also no point in
+	   setting it for an address clause, since the final type of the object
+	   will be a reference type.  */
+	if (Known_Alignment (gnat_entity)
+	    && kind != E_Exception
+	    && No (Address_Clause (gnat_entity)))
+	  align = validate_alignment (Alignment (gnat_entity), gnat_entity,
+				      TYPE_ALIGN (gnu_type));
 
+	/* Likewise, if a size is specified, use it if valid.  */
+	if (Known_Esize (gnat_entity) && No (Address_Clause (gnat_entity)))
+	  gnu_size
+	    = validate_size (Esize (gnat_entity), gnu_type, gnat_entity,
+			     VAR_DECL, false, Has_Size_Clause (gnat_entity));
 	if (gnu_size)
 	  {
 	    gnu_type
@@ -4580,15 +4552,15 @@ gnat_to_gnu_entity (Entity_Id gnat_entit
 	  gnu_type = change_qualified_type (gnu_type, quals);
 	}
 
-      if (!gnu_decl)
-	gnu_decl = create_type_decl (gnu_entity_name, gnu_type,
-				     artificial_p, debug_info_p,
-				     gnat_entity);
-      else
+      /* If we already made a decl, just set the type, otherwise create it.  */
+      if (gnu_decl)
 	{
 	  TREE_TYPE (gnu_decl) = gnu_type;
 	  TYPE_STUB_DECL (gnu_type) = gnu_decl;
 	}
+      else
+	gnu_decl = create_type_decl (gnu_entity_name, gnu_type, artificial_p,
+				     debug_info_p, gnat_entity);
     }
 
   /* If we got a type that is not dummy, back-annotate the alignment of the
Index: gcc-interface/gigi.h
===================================================================
--- gcc-interface/gigi.h	(revision 255622)
+++ gcc-interface/gigi.h	(working copy)
@@ -151,6 +151,9 @@ extern tree maybe_pad_type (tree type, t
 			    bool is_user_type, bool definition,
 			    bool set_rm_size);
 
+/* Return true if padded TYPE was built with an RM size.  */
+extern bool pad_type_has_rm_size (tree type);
+
 /* Return a copy of the padded TYPE but with reverse storage order.  */
 extern tree set_reverse_storage_order_on_pad_type (tree type);
 
Index: gcc-interface/trans.c
===================================================================
--- gcc-interface/trans.c	(revision 255622)
+++ gcc-interface/trans.c	(working copy)
@@ -1850,7 +1850,8 @@ Attribute_to_gnu (Node_Id gnat_node, tre
 	 This is in keeping with the object case of gnat_to_gnu_entity.  */
       else if ((TREE_CODE (gnu_prefix) != TYPE_DECL
 		&& !(TYPE_IS_PADDING_P (gnu_type)
-		     && TREE_CODE (gnu_expr) == COMPONENT_REF))
+		     && TREE_CODE (gnu_expr) == COMPONENT_REF
+		     && pad_type_has_rm_size (gnu_type)))
 	       || attribute == Attr_Object_Size
 	       || attribute == Attr_Max_Size_In_Storage_Elements)
 	{
Index: gcc-interface/utils.c
===================================================================
--- gcc-interface/utils.c	(revision 255622)
+++ gcc-interface/utils.c	(working copy)
@@ -1224,14 +1224,12 @@ pad_type_hasher::equal (pad_type_hash *t
     && TYPE_REVERSE_STORAGE_ORDER (type1) == TYPE_REVERSE_STORAGE_ORDER (type2);
 }
 
-/* Look up the padded TYPE in the hash table and return its canonical version
-   if it exists; otherwise, insert it into the hash table.  */
+/* Compute the hash value for the padded TYPE.  */
 
-static tree
-lookup_and_insert_pad_type (tree type)
+static hashval_t
+hash_pad_type (tree type)
 {
   hashval_t hashcode;
-  struct pad_type_hash in, *h;
 
   hashcode
     = iterative_hash_object (TYPE_HASH (TREE_TYPE (TYPE_FIELDS (type))), 0);
@@ -1239,17 +1237,31 @@ lookup_and_insert_pad_type (tree type)
   hashcode = iterative_hash_hashval_t (TYPE_ALIGN (type), hashcode);
   hashcode = iterative_hash_expr (TYPE_ADA_SIZE (type), hashcode);
 
+  return hashcode;
+}
+
+/* Look up the padded TYPE in the hash table and return its canonical version
+   if it exists; otherwise, insert it into the hash table.  */
+
+static tree
+canonicalize_pad_type (tree type)
+{
+  const hashval_t hashcode = hash_pad_type (type);
+  struct pad_type_hash in, *h, **slot;
+
   in.hash = hashcode;
   in.type = type;
-  h = pad_type_hash_table->find_with_hash (&in, hashcode);
-  if (h)
-    return h->type;
+  slot = pad_type_hash_table->find_slot_with_hash (&in, hashcode, INSERT);
+  h = *slot;
+  if (!h)
+    {
+      h = ggc_alloc<pad_type_hash> ();
+      h->hash = hashcode;
+      h->type = type;
+      *slot = h;
+    }
 
-  h = ggc_alloc<pad_type_hash> ();
-  h->hash = hashcode;
-  h->type = type;
-  *pad_type_hash_table->find_slot_with_hash (h, hashcode, INSERT) = h;
-  return NULL_TREE;
+  return h->type;
 }
 
 /* Ensure that TYPE has SIZE and ALIGN.  Make and return a new padded type
@@ -1380,28 +1392,29 @@ maybe_pad_type (tree type, tree size, un
   /* We will output additional debug info manually below.  */
   finish_record_type (record, field, 1, false);
 
-  if (gnat_encodings == DWARF_GNAT_ENCODINGS_MINIMAL)
-    SET_TYPE_DEBUG_TYPE (record, type);
-
   /* Set the RM size if requested.  */
   if (set_rm_size)
     {
-      tree canonical_pad_type;
-
       SET_TYPE_ADA_SIZE (record, size ? size : orig_size);
 
       /* If the padded type is complete and has constant size, we canonicalize
 	 it by means of the hash table.  This is consistent with the language
 	 semantics and ensures that gigi and the middle-end have a common view
 	 of these padded types.  */
-      if (TREE_CONSTANT (TYPE_SIZE (record))
-	  && (canonical_pad_type = lookup_and_insert_pad_type (record)))
+      if (TREE_CONSTANT (TYPE_SIZE (record)))
 	{
-	  record = canonical_pad_type;
-	  goto built;
+	  tree canonical = canonicalize_pad_type (record);
+	  if (canonical != record)
+	    {
+	      record = canonical;
+	      goto built;
+	    }
 	}
     }
 
+  if (gnat_encodings == DWARF_GNAT_ENCODINGS_MINIMAL)
+    SET_TYPE_DEBUG_TYPE (record, type);
+
   /* Unless debugging information isn't being written for the input type,
      write a record that shows what we are a subtype of and also make a
      variable that indicates our size, if still variable.  */
@@ -1520,13 +1533,31 @@ built:
   return record;
 }
 
+/* Return true if padded TYPE was built with an RM size.  */
+
+bool
+pad_type_has_rm_size (tree type)
+{
+  /* This is required for the lookup.  */
+  if (!TREE_CONSTANT (TYPE_SIZE (type)))
+    return false;
+
+  const hashval_t hashcode = hash_pad_type (type);
+  struct pad_type_hash in, *h;
+
+  in.hash = hashcode;
+  in.type = type;
+  h = pad_type_hash_table->find_with_hash (&in, hashcode);
+
+  /* The types built with an RM size are the canonicalized ones.  */
+  return h && h->type == type;
+}
+
 /* Return a copy of the padded TYPE but with reverse storage order.  */
 
 tree
 set_reverse_storage_order_on_pad_type (tree type)
 {
-  tree field, canonical_pad_type;
-
   if (flag_checking)
     {
       /* If the inner type is not scalar then the function does nothing.  */
@@ -1538,13 +1569,12 @@ set_reverse_storage_order_on_pad_type (t
   /* This is required for the canonicalization.  */
   gcc_assert (TREE_CONSTANT (TYPE_SIZE (type)));
 
-  field = copy_node (TYPE_FIELDS (type));
+  tree field = copy_node (TYPE_FIELDS (type));
   type = copy_type (type);
   DECL_CONTEXT (field) = type;
   TYPE_FIELDS (type) = field;
   TYPE_REVERSE_STORAGE_ORDER (type) = 1;
-  canonical_pad_type = lookup_and_insert_pad_type (type);
-  return canonical_pad_type ? canonical_pad_type : type;
+  return canonicalize_pad_type (type);
 }
 
 /* Relate the alias sets of GNU_NEW_TYPE and GNU_OLD_TYPE according to OP.

-- { dg-do run }
-- { dg-options "-gnatws" }

procedure Alignment11 is

  type Arr is array (1 .. 3) of Character;
  for Arr'Alignment use 4;

  A : Arr;

begin
  if A'Size /= 32 then
    raise Program_Error;
  end if;
end;

-- { dg-do run }
-- { dg-options "-gnatws" }

procedure Alignment12 is

  type Rec is record
    I : Integer;
  end record;

  R : Rec;
  for R'Alignment use 8;

begin
  if R'Size /= 32 then
    raise Program_Error;
  end if;
end;