c: Remove dead code related to type compatibility across TUs.

Code to detect struct/unions across the same TU is not needed
anymore. Code for determining compatibility of tagged types is
preserved as it will be used for C2X. Some errors in the unused
code are fixed.

Bootstrapped with no regressions for x86_64-pc-linux-gnu.

gcc/c/
	* c-decl.cc (set_type_context): Remove.
	(pop_scope, diagnose_mismatched_decls, pushdecl):
	Remove dead code.
	* c-typeck.cc (comptypes_internal): Remove dead code.
	(same_translation_unit_p): Remove.
	(tagged_types_tu_compatible_p): Some fixes.

2 files changed, 27 insertions, 79 deletions

diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index b5b491c..94ce760 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -1155,16 +1155,6 @@ update_label_decls (struct c_scope *scope)
     }
 }
 
-/* Set the TYPE_CONTEXT of all of TYPE's variants to CONTEXT.  */
-
-static void
-set_type_context (tree type, tree context)
-{
-  for (type = TYPE_MAIN_VARIANT (type); type;
-       type = TYPE_NEXT_VARIANT (type))
-    TYPE_CONTEXT (type) = context;
-}
-
 /* Exit a scope.  Restore the state of the identifier-decl mappings
    that were in effect when this scope was entered.  Return a BLOCK
    node containing all the DECLs in this scope that are of interest
@@ -1253,7 +1243,6 @@ pop_scope (void)
 	case ENUMERAL_TYPE:
 	case UNION_TYPE:
 	case RECORD_TYPE:
-	  set_type_context (p, context);
 
 	  /* Types may not have tag-names, in which case the type
 	     appears in the bindings list with b->id NULL.  */
@@ -1364,12 +1353,7 @@ pop_scope (void)
 	     the TRANSLATION_UNIT_DECL.  This makes same_translation_unit_p
 	     work.  */
 	  if (scope == file_scope)
-	    {
 	      DECL_CONTEXT (p) = context;
-	      if (TREE_CODE (p) == TYPE_DECL
-		  && TREE_TYPE (p) != error_mark_node)
-		set_type_context (TREE_TYPE (p), context);
-	    }
 
 	  gcc_fallthrough ();
 	  /* Parameters go in DECL_ARGUMENTS, not BLOCK_VARS, and have
@@ -2318,21 +2302,18 @@ diagnose_mismatched_decls (tree newdecl, tree olddecl,
 	{
 	  if (DECL_INITIAL (olddecl))
 	    {
-	      /* If both decls are in the same TU and the new declaration
-		 isn't overriding an extern inline reject the new decl.
-		 In c99, no overriding is allowed in the same translation
-		 unit.  */
-	      if ((!DECL_EXTERN_INLINE (olddecl)
-		   || DECL_EXTERN_INLINE (newdecl)
-		   || (!flag_gnu89_inline
-		       && (!DECL_DECLARED_INLINE_P (olddecl)
-			   || !lookup_attribute ("gnu_inline",
-						 DECL_ATTRIBUTES (olddecl)))
-		       && (!DECL_DECLARED_INLINE_P (newdecl)
-			   || !lookup_attribute ("gnu_inline",
-						 DECL_ATTRIBUTES (newdecl))))
-		  )
-		  && same_translation_unit_p (newdecl, olddecl))
+	      /* If the new declaration isn't overriding an extern inline
+		 reject the new decl. In c99, no overriding is allowed
+		 in the same translation unit.  */
+	      if (!DECL_EXTERN_INLINE (olddecl)
+		  || DECL_EXTERN_INLINE (newdecl)
+		  || (!flag_gnu89_inline
+		      && (!DECL_DECLARED_INLINE_P (olddecl)
+			  || !lookup_attribute ("gnu_inline",
+						DECL_ATTRIBUTES (olddecl)))
+		      && (!DECL_DECLARED_INLINE_P (newdecl)
+			  || !lookup_attribute ("gnu_inline",
+						DECL_ATTRIBUTES (newdecl)))))
 		{
 		  auto_diagnostic_group d;
 		  error ("redefinition of %q+D", newdecl);
@@ -3372,18 +3353,11 @@ pushdecl (tree x)
 	 type to the composite of all the types of that declaration.
 	 After the consistency checks, it will be reset to the
 	 composite of the visible types only.  */
-      if (b && (TREE_PUBLIC (x) || same_translation_unit_p (x, b->decl))
-	  && b->u.type)
+      if (b && b->u.type)
 	TREE_TYPE (b->decl) = b->u.type;
 
-      /* The point of the same_translation_unit_p check here is,
-	 we want to detect a duplicate decl for a construct like
-	 foo() { extern bar(); } ... static bar();  but not if
-	 they are in different translation units.  In any case,
-	 the static does not go in the externals scope.  */
-      if (b
-	  && (TREE_PUBLIC (x) || same_translation_unit_p (x, b->decl))
-	  && duplicate_decls (x, b->decl))
+      /* the static does not go in the externals scope.  */
+      if (b && duplicate_decls (x, b->decl))
 	{
 	  tree thistype;
 	  if (vistype)
diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index 191a90f..22e240a 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -1259,7 +1259,7 @@ comptypes_internal (const_tree type1, const_tree type2, bool *enum_and_int_p,
     case ENUMERAL_TYPE:
     case RECORD_TYPE:
     case UNION_TYPE:
-      if (val != 1 && !same_translation_unit_p (t1, t2))
+      if (val != 1 && false)
 	{
 	  tree a1 = TYPE_ATTRIBUTES (t1);
 	  tree a2 = TYPE_ATTRIBUTES (t2);
@@ -1268,11 +1268,11 @@ comptypes_internal (const_tree type1, const_tree type2, bool *enum_and_int_p,
 	      && ! attribute_list_contained (a2, a1))
 	    break;
 
-	  if (attrval != 2)
-	    return tagged_types_tu_compatible_p (t1, t2, enum_and_int_p,
-						 different_types_p);
 	  val = tagged_types_tu_compatible_p (t1, t2, enum_and_int_p,
 					      different_types_p);
+
+	  if (attrval != 2)
+	    return val;
 	}
       break;
 
@@ -1347,40 +1347,7 @@ comp_target_types (location_t location, tree ttl, tree ttr)
 
 /* Subroutines of `comptypes'.  */
 
-/* Determine whether two trees derive from the same translation unit.
-   If the CONTEXT chain ends in a null, that tree's context is still
-   being parsed, so if two trees have context chains ending in null,
-   they're in the same translation unit.  */
-
-bool
-same_translation_unit_p (const_tree t1, const_tree t2)
-{
-  while (t1 && TREE_CODE (t1) != TRANSLATION_UNIT_DECL)
-    switch (TREE_CODE_CLASS (TREE_CODE (t1)))
-      {
-      case tcc_declaration:
-	t1 = DECL_CONTEXT (t1); break;
-      case tcc_type:
-	t1 = TYPE_CONTEXT (t1); break;
-      case tcc_exceptional:
-	t1 = BLOCK_SUPERCONTEXT (t1); break;  /* assume block */
-      default: gcc_unreachable ();
-      }
 
-  while (t2 && TREE_CODE (t2) != TRANSLATION_UNIT_DECL)
-    switch (TREE_CODE_CLASS (TREE_CODE (t2)))
-      {
-      case tcc_declaration:
-	t2 = DECL_CONTEXT (t2); break;
-      case tcc_type:
-	t2 = TYPE_CONTEXT (t2); break;
-      case tcc_exceptional:
-	t2 = BLOCK_SUPERCONTEXT (t2); break;  /* assume block */
-      default: gcc_unreachable ();
-      }
-
-  return t1 == t2;
-}
 
 /* Allocate the seen two types, assuming that they are compatible. */
 
@@ -1531,6 +1498,7 @@ tagged_types_tu_compatible_p (const_tree t1, const_tree t2,
     case UNION_TYPE:
       {
 	struct tagged_tu_seen_cache *tu = alloc_tagged_tu_seen_cache (t1, t2);
+
 	if (list_length (TYPE_FIELDS (t1)) != list_length (TYPE_FIELDS (t2)))
 	  {
 	    tu->val = 0;
@@ -1609,7 +1577,7 @@ tagged_types_tu_compatible_p (const_tree t1, const_tree t2,
 		return 0;
 	      }
 	  }
-	tu->val = needs_warning ? 2 : 10;
+	tu->val = needs_warning ? 2 : 1;
 	return tu->val;
       }
 
@@ -1617,6 +1585,12 @@ tagged_types_tu_compatible_p (const_tree t1, const_tree t2,
       {
 	struct tagged_tu_seen_cache *tu = alloc_tagged_tu_seen_cache (t1, t2);
 
+	if (list_length (TYPE_FIELDS (t1)) != list_length (TYPE_FIELDS (t2)))
+	  {
+	    tu->val = 0;
+	    return 0;
+	  }
+
 	for (s1 = TYPE_FIELDS (t1), s2 = TYPE_FIELDS (t2);
 	     s1 && s2;
 	     s1 = DECL_CHAIN (s1), s2 = DECL_CHAIN (s2))