Re: [PATCH] Fix TYPE_TYPELESS_STORAGE handling (PR middle-end/80423)

[Richard Biener <rguenther at suse dot de>]

On April 18, 2017 5:14:30 PM GMT+02:00, Jakub Jelinek <jakub@redhat.com> wrote:
>Hi!
>
>As mentioned in the PR, we now use TYPE_TYPELESS_STORAGE flag on
>ARRAY_TYPEs to denote types that need the special C++ alias handling.
>The problem is how is that created, we just use build_array_type and
>set TYPE_TYPELESS_STORAGE on the result, but build_array_type uses type
>caching, so we might modify that way some other array type.
>If all the array type creation goes through build_cplus_array_type,
>that
>wouldn't be a problem, as that flag is dependent just on the element
>type, but that is not the case, c-family as well as the middle-end has
>lots of spots that also create array types.  So in the end whether
>one gets TYPE_TYPELESS_STORAGE flag or not is quite random, depends on
>GC etc.
>
>The following patch attempts to resolve this, by making the type
>hashing
>take that flag into account.  Bootstrapped/regtested on x86_64-linux
>and
>i686-linux, ok for trunk?

When changing the C++ function I thought that calling build_array_type was wrong and it should instead do the same it does in the other places, use its raw creation routine and then the canonical type register stuff.  But I was hesitant to change this at this point.

I'm on FTO today so can't experiment with that before torrow.

Richard.

>2017-04-18  Jakub Jelinek  <jakub@redhat.com>
>
>	PR middle-end/80423
>	* tree.h (build_array_type_1): New prototype.
>	* tree.c (type_cache_hasher::equal): Also compare
>	TYPE_TYPELESS_STORAGE flag for ARRAY_TYPEs.
>	(build_array_type_1): No longer static.  Add typeless_storage
>	argument, set TYPE_TYPELESS_STORAGE to it, if shared also
>	hash it, and pass to recursive call.
>	(build_array_type, build_nonshared_array_type): Adjust
>	build_array_type_1 callers.
>c-family/
>	* c-common.c (complete_array_type): Preserve TYPE_TYPELESS_STORAGE.
>cp/
>	* tree.c (build_cplus_array_type): Call build_array_type_1
>	with the intended TYPE_TYPELESS_STORAGE flag value, instead
>	of calling build_array_type and modifying TYPE_TYPELESS_STORAGE
>	on the shared type.
>testsuite/
>	* g++.dg/other/pr80423.C: New test.
>
>--- gcc/tree.h.jj	2017-04-12 13:22:23.000000000 +0200
>+++ gcc/tree.h	2017-04-18 12:38:02.981708334 +0200
>@@ -4068,6 +4068,7 @@ extern tree build_truth_vector_type (uns
> extern tree build_same_sized_truth_vector_type (tree vectype);
> extern tree build_opaque_vector_type (tree innertype, int nunits);
> extern tree build_index_type (tree);
>+extern tree build_array_type_1 (tree, tree, bool, bool);
> extern tree build_array_type (tree, tree);
> extern tree build_nonshared_array_type (tree, tree);
> extern tree build_array_type_nelts (tree, unsigned HOST_WIDE_INT);
>--- gcc/tree.c.jj	2017-04-07 11:46:46.000000000 +0200
>+++ gcc/tree.c	2017-04-18 12:37:38.765024350 +0200
>@@ -7073,7 +7073,9 @@ type_cache_hasher::equal (type_hash *a,
>         break;
>       return 0;
>     case ARRAY_TYPE:
>-      return TYPE_DOMAIN (a->type) == TYPE_DOMAIN (b->type);
>+      return (TYPE_TYPELESS_STORAGE (a->type)
>+	      == TYPE_TYPELESS_STORAGE (b->type)
>+	      && TYPE_DOMAIN (a->type) == TYPE_DOMAIN (b->type));
> 
>     case RECORD_TYPE:
>     case UNION_TYPE:
>@@ -8352,8 +8354,9 @@ subrange_type_for_debug_p (const_tree ty
> and number of elements specified by the range of values of INDEX_TYPE.
>If SHARED is true, reuse such a type that has already been constructed.
> */
> 
>-static tree
>-build_array_type_1 (tree elt_type, tree index_type, bool shared)
>+tree
>+build_array_type_1 (tree elt_type, tree index_type, bool shared,
>+		    bool typeless_storage)
> {
>   tree t;
> 
>@@ -8367,6 +8370,7 @@ build_array_type_1 (tree elt_type, tree
>   TREE_TYPE (t) = elt_type;
>   TYPE_DOMAIN (t) = index_type;
>   TYPE_ADDR_SPACE (t) = TYPE_ADDR_SPACE (elt_type);
>+  TYPE_TYPELESS_STORAGE (t) = typeless_storage;
>   layout_type (t);
> 
>   /* If the element type is incomplete at this point we get marked for
>@@ -8381,6 +8385,7 @@ build_array_type_1 (tree elt_type, tree
>       hstate.add_object (TYPE_HASH (elt_type));
>       if (index_type)
> 	hstate.add_object (TYPE_HASH (index_type));
>+      hstate.add_flag (typeless_storage);
>       t = type_hash_canon (hstate.end (), t);
>     }
> 
>@@ -8396,7 +8401,7 @@ build_array_type_1 (tree elt_type, tree
> 	  = build_array_type_1 (TYPE_CANONICAL (elt_type),
> 				index_type
> 				? TYPE_CANONICAL (index_type) : NULL_TREE,
>-				shared);
>+				shared, typeless_storage);
>     }
> 
>   return t;
>@@ -8407,7 +8412,7 @@ build_array_type_1 (tree elt_type, tree
> tree
> build_array_type (tree elt_type, tree index_type)
> {
>-  return build_array_type_1 (elt_type, index_type, true);
>+  return build_array_type_1 (elt_type, index_type, true, false);
> }
> 
> /* Wrapper around build_array_type_1 with SHARED set to false.  */
>@@ -8415,7 +8420,7 @@ build_array_type (tree elt_type, tree in
> tree
> build_nonshared_array_type (tree elt_type, tree index_type)
> {
>-  return build_array_type_1 (elt_type, index_type, false);
>+  return build_array_type_1 (elt_type, index_type, false, false);
> }
> 
> /* Return a representation of ELT_TYPE[NELTS], using indices of type
>--- gcc/c-family/c-common.c.jj	2017-04-10 22:26:55.000000000 +0200
>+++ gcc/c-family/c-common.c	2017-04-18 14:43:53.448092585 +0200
>@@ -6397,7 +6397,6 @@ complete_array_type (tree *ptype, tree i
> {
>   tree maxindex, type, main_type, elt, unqual_elt;
>   int failure = 0, quals;
>-  hashval_t hashcode = 0;
>   bool overflow_p = false;
> 
>   maxindex = size_zero_node;
>@@ -6491,13 +6490,15 @@ complete_array_type (tree *ptype, tree i
>   TYPE_DOMAIN (main_type)
>     = build_range_type (TREE_TYPE (maxindex),
> 			build_int_cst (TREE_TYPE (maxindex), 0), maxindex);
>+  TYPE_TYPELESS_STORAGE (main_type) = TYPE_TYPELESS_STORAGE (type);
>   layout_type (main_type);
> 
>   /* Make sure we have the canonical MAIN_TYPE. */
>-  hashcode = iterative_hash_object (TYPE_HASH (unqual_elt), hashcode);
>-  hashcode = iterative_hash_object (TYPE_HASH (TYPE_DOMAIN
>(main_type)),
>-				    hashcode);
>-  main_type = type_hash_canon (hashcode, main_type);
>+  inchash::hash hstate;
>+  hstate.add_object (TYPE_HASH (unqual_elt));
>+  hstate.add_object (TYPE_HASH (TYPE_DOMAIN (main_type)));
>+  hstate.add_flag (TYPE_TYPELESS_STORAGE (main_type));
>+  main_type = type_hash_canon (hstate.end (), main_type);
> 
>   /* Fix the canonical type.  */
>   if (TYPE_STRUCTURAL_EQUALITY_P (TREE_TYPE (main_type))
>@@ -6507,8 +6508,9 @@ complete_array_type (tree *ptype, tree i
> 	   || (TYPE_CANONICAL (TYPE_DOMAIN (main_type))
> 	       != TYPE_DOMAIN (main_type)))
>     TYPE_CANONICAL (main_type)
>-      = build_array_type (TYPE_CANONICAL (TREE_TYPE (main_type)),
>-			  TYPE_CANONICAL (TYPE_DOMAIN (main_type)));
>+      = build_array_type_1 (TYPE_CANONICAL (TREE_TYPE (main_type)),
>+			    TYPE_CANONICAL (TYPE_DOMAIN (main_type)),
>+			    true, TYPE_TYPELESS_STORAGE (main_type));
>   else
>     TYPE_CANONICAL (main_type) = main_type;
> 
>--- gcc/cp/tree.c.jj	2017-04-18 09:11:54.000000000 +0200
>+++ gcc/cp/tree.c	2017-04-18 14:42:28.911225896 +0200
>@@ -949,14 +949,14 @@ build_cplus_array_type (tree elt_type, t
>     }
>   else
>     {
>-      t = build_array_type (elt_type, index_type);
>-      if (elt_type == unsigned_char_type_node
>-	  || elt_type == signed_char_type_node
>-	  || elt_type == char_type_node
>-	  || (TREE_CODE (elt_type) == ENUMERAL_TYPE
>-	      && TYPE_CONTEXT (elt_type) == std_node
>-	      && !strcmp ("byte", TYPE_NAME_STRING (elt_type))))
>-	TYPE_TYPELESS_STORAGE (t) = 1;
>+      bool typeless_storage
>+	= (elt_type == unsigned_char_type_node
>+	   || elt_type == signed_char_type_node
>+	   || elt_type == char_type_node
>+	   || (TREE_CODE (elt_type) == ENUMERAL_TYPE
>+	       && TYPE_CONTEXT (elt_type) == std_node
>+	       && !strcmp ("byte", TYPE_NAME_STRING (elt_type))));
>+      t = build_array_type_1 (elt_type, index_type, true,
>typeless_storage);
>     }
> 
>   /* Now check whether we already have this array variant.  */
>--- gcc/testsuite/g++.dg/other/pr80423.C.jj	2017-04-18
>14:48:21.098510615 +0200
>+++ gcc/testsuite/g++.dg/other/pr80423.C	2017-04-18 14:49:02.049964200
>+0200
>@@ -0,0 +1,11 @@
>+// PR middle-end/80423
>+// { dg-do compile { target c++11 } }
>+
>+typedef unsigned char uint8_t;                                        
>                                                                       
>+struct A {                                                            
>                                                                       
>+  template <int N> A(unsigned char (&)[N]);                           
>                                                                       
>+};                                                                    
>                                                                       
>+void fn1(A) {                                                         
>                                                                       
>+  uint8_t a[]{0};                                                     
>                                                                       
>+  fn1(a);                                                             
>                                                                       
>+}                                                                     
>                                                                       
>
>	Jakub