Re: C++ PATCH for c++/50800 (ICE with may_alias and templates)

[Jason Merrill <jason at redhat dot com>]

On 04/23/2015 01:45 PM, H.J. Lu wrote:
> On Thu, Apr 23, 2015 at 8:52 AM, Jason Merrill <jason@redhat.com> wrote:
> > We try to strip attributes that aren't reflected in mangling from template
> > arguments, but were failing to do that in this case.  Fixed by making
> > strip_typedefs strip such attributes as well.
> >
> > Tested x86_64-pc-linux-gnu, applying to trunk.
>
> This caused:
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65865

This turned out to be because of a thinko in apply_identity_attributes; 
we weren't actually applying the identity attributes.  Fixed thus.


commit e286f8f59bd1a82ecf9edc37ecf1f45ae8726c11
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Apr 23 15:40:50 2015 -0400

    	PR c++/50800
    	* tree.c (strip_typedefs): Add remove_attributes parm.
    	(strip_typedefs_expr): Likewise.
    	(apply_identity_attributes): New subroutine of strip_typedefs.
    	* pt.c (canonicalize_type_argument): Let strip_typedefs handle attrs.
    	(convert_nontype_argument, unify): Likewise.
    	* cp-tree.h: Adjust.

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 2a904a5..df03d1a 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6066,8 +6066,8 @@ extern bool class_tmpl_impl_spec_p		(const_tree);
 extern int zero_init_p				(const_tree);
 extern bool check_abi_tag_redeclaration		(const_tree, const_tree, const_tree);
 extern bool check_abi_tag_args			(tree, tree);
-extern tree strip_typedefs			(tree);
-extern tree strip_typedefs_expr			(tree);
+extern tree strip_typedefs			(tree, bool * = NULL);
+extern tree strip_typedefs_expr			(tree, bool * = NULL);
 extern tree copy_binfo				(tree, tree, tree,
 						 tree *, int);
 extern int member_p				(const_tree);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index f9a5c3b..ea0d3bc 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -6493,20 +6493,14 @@ template_template_parm_bindings_ok_p (tree tparms, tree targs)
 static tree
 canonicalize_type_argument (tree arg, tsubst_flags_t complain)
 {
-  tree mv;
   if (!arg || arg == error_mark_node || arg == TYPE_CANONICAL (arg))
     return arg;
-  mv = TYPE_MAIN_VARIANT (arg);
-  arg = strip_typedefs (arg);
-  if (TYPE_ALIGN (arg) != TYPE_ALIGN (mv)
-      || TYPE_ATTRIBUTES (arg) != TYPE_ATTRIBUTES (mv))
-    {
-      if (complain & tf_warning)
-	warning (0, "ignoring attributes on template argument %qT", arg);
-      arg = build_aligned_type (arg, TYPE_ALIGN (mv));
-      arg = cp_build_type_attribute_variant (arg, TYPE_ATTRIBUTES (mv));
-    }
-  return arg;
+  bool removed_attributes = false;
+  tree canon = strip_typedefs (arg, &removed_attributes);
+  if (removed_attributes
+      && (complain & tf_warning))
+    warning (0, "ignoring attributes on template argument %qT", arg);
+  return canon;
 }
 
 /* Convert the indicated template ARG as necessary to match the
@@ -6743,7 +6737,10 @@ convert_template_argument (tree parm,
 	   argument specification is valid.  */
 	val = convert_nontype_argument (t, orig_arg, complain);
       else
-	val = strip_typedefs_expr (orig_arg);
+	{
+	  bool removed_attr = false;
+	  val = strip_typedefs_expr (orig_arg, &removed_attr);
+	}
 
       if (val == NULL_TREE)
 	val = error_mark_node;
@@ -18202,7 +18199,10 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict,
 	  && !TEMPLATE_PARM_PARAMETER_PACK (parm))
 	return unify_parameter_pack_mismatch (explain_p, parm, arg);
 
-      arg = strip_typedefs_expr (arg);
+      {
+	bool removed_attr = false;
+	arg = strip_typedefs_expr (arg, &removed_attr);
+      }
       TREE_VEC_ELT (INNERMOST_TEMPLATE_ARGS (targs), idx) = arg;
       return unify_success (explain_p);
 
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 9a4779f..d00f0d7 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -55,6 +55,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimple-expr.h"
 #include "gimplify.h"
 #include "wide-int.h"
+#include "attribs.h"
 
 static tree bot_manip (tree *, int *, void *);
 static tree bot_replace (tree *, int *, void *);
@@ -1175,6 +1176,52 @@ cv_unqualified (tree type)
   return cp_build_qualified_type (type, quals);
 }
 
+/* Subroutine of strip_typedefs.  We want to apply to RESULT the attributes
+   from ATTRIBS that affect type identity, and no others.  If any are not
+   applied, set *remove_attributes to true.  */
+
+static tree
+apply_identity_attributes (tree result, tree attribs, bool *remove_attributes)
+{
+  tree first_ident = NULL_TREE;
+  tree new_attribs = NULL_TREE;
+  tree *p = &new_attribs;
+
+  for (tree a = attribs; a; a = TREE_CHAIN (a))
+    {
+      const attribute_spec *as
+	= lookup_attribute_spec (get_attribute_name (a));
+      if (as && as->affects_type_identity)
+	{
+	  if (!first_ident)
+	    first_ident = a;
+	  else if (first_ident == error_mark_node)
+	    {
+	      *p = tree_cons (TREE_PURPOSE (a), TREE_VALUE (a), NULL_TREE);
+	      p = &TREE_CHAIN (*p);
+	    }
+	}
+      else if (first_ident)
+	{
+	  for (tree a2 = first_ident; a2; a2 = TREE_CHAIN (a2))
+	    {
+	      *p = tree_cons (TREE_PURPOSE (a2), TREE_VALUE (a2), NULL_TREE);
+	      p = &TREE_CHAIN (*p);
+	    }
+	  first_ident = error_mark_node;
+	}
+    }
+  if (first_ident != error_mark_node)
+    new_attribs = first_ident;
+
+  if (first_ident == attribs)
+    /* All attributes affected type identity.  */;
+  else
+    *remove_attributes = true;
+
+  return cp_build_type_attribute_variant (result, new_attribs);
+}
+
 /* Builds a qualified variant of T that is not a typedef variant.
    E.g. consider the following declarations:
      typedef const int ConstInt;
@@ -1193,10 +1240,14 @@ cv_unqualified (tree type)
     * If T is a type that needs structural equality
       its TYPE_CANONICAL (T) will be NULL.
     * TYPE_CANONICAL (T) desn't carry type attributes
-      and loses template parameter names.   */
+      and loses template parameter names.
+
+   If REMOVE_ATTRIBUTES is non-null, also strip attributes that don't
+   affect type identity, and set the referent to true if any were
+   stripped.  */
 
 tree
-strip_typedefs (tree t)
+strip_typedefs (tree t, bool *remove_attributes)
 {
   tree result = NULL, type = NULL, t0 = NULL;
 
@@ -1210,7 +1261,7 @@ strip_typedefs (tree t)
       for (; t; t = TREE_CHAIN (t))
 	{
 	  gcc_assert (!TREE_PURPOSE (t));
-	  tree elt = strip_typedefs (TREE_VALUE (t));
+	  tree elt = strip_typedefs (TREE_VALUE (t), remove_attributes);
 	  if (elt != TREE_VALUE (t))
 	    changed = true;
 	  vec_safe_push (vec, elt);
@@ -1235,28 +1286,28 @@ strip_typedefs (tree t)
   switch (TREE_CODE (t))
     {
     case POINTER_TYPE:
-      type = strip_typedefs (TREE_TYPE (t));
+      type = strip_typedefs (TREE_TYPE (t), remove_attributes);
       result = build_pointer_type (type);
       break;
     case REFERENCE_TYPE:
-      type = strip_typedefs (TREE_TYPE (t));
+      type = strip_typedefs (TREE_TYPE (t), remove_attributes);
       result = cp_build_reference_type (type, TYPE_REF_IS_RVALUE (t));
       break;
     case OFFSET_TYPE:
-      t0 = strip_typedefs (TYPE_OFFSET_BASETYPE (t));
-      type = strip_typedefs (TREE_TYPE (t));
+      t0 = strip_typedefs (TYPE_OFFSET_BASETYPE (t), remove_attributes);
+      type = strip_typedefs (TREE_TYPE (t), remove_attributes);
       result = build_offset_type (t0, type);
       break;
     case RECORD_TYPE:
       if (TYPE_PTRMEMFUNC_P (t))
 	{
-	  t0 = strip_typedefs (TYPE_PTRMEMFUNC_FN_TYPE (t));
+	  t0 = strip_typedefs (TYPE_PTRMEMFUNC_FN_TYPE (t), remove_attributes);
 	  result = build_ptrmemfunc_type (t0);
 	}
       break;
     case ARRAY_TYPE:
-      type = strip_typedefs (TREE_TYPE (t));
-      t0  = strip_typedefs (TYPE_DOMAIN (t));;
+      type = strip_typedefs (TREE_TYPE (t), remove_attributes);
+      t0  = strip_typedefs (TYPE_DOMAIN (t), remove_attributes);
       result = build_cplus_array_type (type, t0);
       break;
     case FUNCTION_TYPE:
@@ -1269,7 +1320,8 @@ strip_typedefs (tree t)
 	  {
 	    if (arg_node == void_list_node)
 	      break;
-	    arg_type = strip_typedefs (TREE_VALUE (arg_node));
+	    arg_type = strip_typedefs (TREE_VALUE (arg_node),
+				       remove_attributes);
 	    gcc_assert (arg_type);
 
 	    arg_types =
@@ -1284,7 +1336,7 @@ strip_typedefs (tree t)
 	if (arg_node)
 	  arg_types = chainon (arg_types, void_list_node);
 
-	type = strip_typedefs (TREE_TYPE (t));
+	type = strip_typedefs (TREE_TYPE (t), remove_attributes);
 	if (TREE_CODE (t) == METHOD_TYPE)
 	  {
 	    tree class_type = TREE_TYPE (TREE_VALUE (arg_types));
@@ -1325,9 +1377,9 @@ strip_typedefs (tree t)
 		tree arg = TREE_VEC_ELT (args, i);
 		tree strip_arg;
 		if (TYPE_P (arg))
-		  strip_arg = strip_typedefs (arg);
+		  strip_arg = strip_typedefs (arg, remove_attributes);
 		else
-		  strip_arg = strip_typedefs_expr (arg);
+		  strip_arg = strip_typedefs_expr (arg, remove_attributes);
 		TREE_VEC_ELT (new_args, i) = strip_arg;
 		if (strip_arg != arg)
 		  changed = true;
@@ -1343,12 +1395,14 @@ strip_typedefs (tree t)
 	    else
 	      ggc_free (new_args);
 	  }
-	result = make_typename_type (strip_typedefs (TYPE_CONTEXT (t)),
+	result = make_typename_type (strip_typedefs (TYPE_CONTEXT (t),
+						     remove_attributes),
 				     fullname, typename_type, tf_none);
       }
       break;
     case DECLTYPE_TYPE:
-      result = strip_typedefs_expr (DECLTYPE_TYPE_EXPR (t));
+      result = strip_typedefs_expr (DECLTYPE_TYPE_EXPR (t),
+				    remove_attributes);
       if (result == DECLTYPE_TYPE_EXPR (t))
 	return t;
       else
@@ -1367,14 +1421,25 @@ strip_typedefs (tree t)
       || TYPE_ALIGN (t) != TYPE_ALIGN (result))
     {
       gcc_assert (TYPE_USER_ALIGN (t));
-      if (TYPE_ALIGN (t) == TYPE_ALIGN (result))
-	result = build_variant_type_copy (result);
+      if (remove_attributes)
+	*remove_attributes = true;
       else
-	result = build_aligned_type (result, TYPE_ALIGN (t));
-      TYPE_USER_ALIGN (result) = true;
+	{
+	  if (TYPE_ALIGN (t) == TYPE_ALIGN (result))
+	    result = build_variant_type_copy (result);
+	  else
+	    result = build_aligned_type (result, TYPE_ALIGN (t));
+	  TYPE_USER_ALIGN (result) = true;
+	}
     }
   if (TYPE_ATTRIBUTES (t))
-    result = cp_build_type_attribute_variant (result, TYPE_ATTRIBUTES (t));
+    {
+      if (remove_attributes)
+	result = apply_identity_attributes (result, TYPE_ATTRIBUTES (t),
+					    remove_attributes);
+      else
+	result = cp_build_type_attribute_variant (result, TYPE_ATTRIBUTES (t));
+    }
   return cp_build_qualified_type (result, cp_type_quals (t));
 }
 
@@ -1389,7 +1454,7 @@ strip_typedefs (tree t)
    sizeof(TT) is replaced by sizeof(T).  */
 
 tree
-strip_typedefs_expr (tree t)
+strip_typedefs_expr (tree t, bool *remove_attributes)
 {
   unsigned i,n;
   tree r, type, *ops;
@@ -1404,7 +1469,7 @@ strip_typedefs_expr (tree t)
   /* Some expressions have type operands, so let's handle types here rather
      than check TYPE_P in multiple places below.  */
   if (TYPE_P (t))
-    return strip_typedefs (t);
+    return strip_typedefs (t, remove_attributes);
 
   code = TREE_CODE (t);
   switch (code)
@@ -1418,8 +1483,8 @@ strip_typedefs_expr (tree t)
 
     case TRAIT_EXPR:
       {
-	tree type1 = strip_typedefs (TRAIT_EXPR_TYPE1 (t));
-	tree type2 = strip_typedefs (TRAIT_EXPR_TYPE2 (t));
+	tree type1 = strip_typedefs (TRAIT_EXPR_TYPE1 (t), remove_attributes);
+	tree type2 = strip_typedefs (TRAIT_EXPR_TYPE2 (t), remove_attributes);
 	if (type1 == TRAIT_EXPR_TYPE1 (t)
 	    && type2 == TRAIT_EXPR_TYPE2 (t))
 	  return t;
@@ -1436,7 +1501,7 @@ strip_typedefs_expr (tree t)
 	tree it;
 	for (it = t; it; it = TREE_CHAIN (it))
 	  {
-	    tree val = strip_typedefs_expr (TREE_VALUE (t));
+	    tree val = strip_typedefs_expr (TREE_VALUE (t), remove_attributes);
 	    vec_safe_push (vec, val);
 	    if (val != TREE_VALUE (t))
 	      changed = true;
@@ -1462,7 +1527,8 @@ strip_typedefs_expr (tree t)
 	vec_safe_reserve (vec, n);
 	for (i = 0; i < n; ++i)
 	  {
-	    tree op = strip_typedefs_expr (TREE_VEC_ELT (t, i));
+	    tree op = strip_typedefs_expr (TREE_VEC_ELT (t, i),
+					   remove_attributes);
 	    vec->quick_push (op);
 	    if (op != TREE_VEC_ELT (t, i))
 	      changed = true;
@@ -1487,17 +1553,18 @@ strip_typedefs_expr (tree t)
 	vec<constructor_elt, va_gc> *vec
 	  = vec_safe_copy (CONSTRUCTOR_ELTS (t));
 	n = CONSTRUCTOR_NELTS (t);
-	type = strip_typedefs (TREE_TYPE (t));
+	type = strip_typedefs (TREE_TYPE (t), remove_attributes);
 	for (i = 0; i < n; ++i)
 	  {
 	    constructor_elt *e = &(*vec)[i];
-	    tree op = strip_typedefs_expr (e->value);
+	    tree op = strip_typedefs_expr (e->value, remove_attributes);
 	    if (op != e->value)
 	      {
 		changed = true;
 		e->value = op;
 	      }
-	    gcc_checking_assert (e->index == strip_typedefs_expr (e->index));
+	    gcc_checking_assert
+	      (e->index == strip_typedefs_expr (e->index, remove_attributes));
 	  }
 
 	if (!changed && type == TREE_TYPE (t))
@@ -1538,12 +1605,12 @@ strip_typedefs_expr (tree t)
     case REINTERPRET_CAST_EXPR:
     case CAST_EXPR:
     case NEW_EXPR:
-      type = strip_typedefs (type);
+      type = strip_typedefs (type, remove_attributes);
       /* fallthrough */
 
     default:
       for (i = 0; i < n; ++i)
-	ops[i] = strip_typedefs_expr (TREE_OPERAND (t, i));
+	ops[i] = strip_typedefs_expr (TREE_OPERAND (t, i), remove_attributes);
       break;
     }
 
diff --git a/gcc/testsuite/g++.dg/abi/mangle40.C b/gcc/testsuite/g++.dg/abi/mangle40.C
index 2b8300b..a7032a0 100644
--- a/gcc/testsuite/g++.dg/abi/mangle40.C
+++ b/gcc/testsuite/g++.dg/abi/mangle40.C
@@ -24,5 +24,5 @@ void f (T t) { }		// { dg-warning "mangled name" }
 
 int main()
 {
-  f (A<__m128>::t);
+  f (A<__v4sf>::t);
 }
diff --git a/gcc/testsuite/g++.dg/ext/alias-mangle.C b/gcc/testsuite/g++.dg/ext/alias-mangle.C
index a7706e9..d804c1a 100644
--- a/gcc/testsuite/g++.dg/ext/alias-mangle.C
+++ b/gcc/testsuite/g++.dg/ext/alias-mangle.C
@@ -8,4 +8,4 @@ template<typename> struct A
   A();
 };
 
-A<X> a;
+A<X> a;	       // { dg-warning "ignoring attributes on template argument" }
diff --git a/gcc/testsuite/g++.dg/ext/attrib50.C b/gcc/testsuite/g++.dg/ext/attrib50.C
new file mode 100644
index 0000000..9ff9918
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/attrib50.C
@@ -0,0 +1,11 @@
+// PR c++/50800
+
+template <typename T> struct B;
+template <typename T> struct B<T &> {
+  typedef T type;
+};
+struct A {
+  typedef int TA __attribute__((__may_alias__));
+};
+void d() { B<int &> b; }
+int main() { B<A::TA &> b; }	// { dg-warning "attributes" }