re PR rtl-optimization/54870 (gfortran.dg/array_constructor_4.f90 FAILs)

	PR rtl-optimization/54870
	* tree.h (TREE_ADDRESSABLE): Document special usage on SSA_NAME.
	* cfgexpand.c (update_alias_info_with_stack_vars ): Set it on the
	SSA_NAME pointer that points to a partition if there is at least
	one variable with it set in the partition.
	* dse.c (local_variable_can_escape): New predicate.
	(can_escape): Call it.
	* gimplify.c (mark_addressable): If this is a partitioned decl, also
	mark the SSA_NAME pointer that points to a partition.

From-SVN: r192517

gcc/cfgexpand.c

@@ -635,6 +635,8 @@ update_alias_info_with_stack_vars (void)
 					   (void *)(size_t) uid)) = part;
 	  *((tree *) pointer_map_insert (cfun->gimple_df->decls_to_pointers,
 					 decl)) = name;
+	  if (TREE_ADDRESSABLE (decl))
+	    TREE_ADDRESSABLE (name) = 1;
 	}
 
       /* Make the SSA name point to all partition members.  */

gcc/dse.c

@@ -989,7 +989,32 @@ delete_dead_store_insn (insn_info_t insn_info)
   insn_info->wild_read = false;
 }
 
-/* Check if EXPR can possibly escape the current function scope.  */
+/* Return whether DECL, a local variable, can possibly escape the current
+   function scope.  */
+
+static bool
+local_variable_can_escape (tree decl)
+{
+  if (TREE_ADDRESSABLE (decl))
+    return true;
+
+  /* If this is a partitioned variable, we need to consider all the variables
+     in the partition.  This is necessary because a store into one of them can
+     be replaced with a store into another and this may not change the outcome
+     of the escape analysis.  */
+  if (cfun->gimple_df->decls_to_pointers != NULL)
+    {
+      void *namep
+	= pointer_map_contains (cfun->gimple_df->decls_to_pointers, decl);
+      if (namep)
+	return TREE_ADDRESSABLE (*(tree *)namep);
+    }
+
+  return false;
+}
+
+/* Return whether EXPR can possibly escape the current function scope.  */
+
 static bool
 can_escape (tree expr)
 {
@@ -998,7 +1023,11 @@ can_escape (tree expr)
     return true;
   base = get_base_address (expr);
   if (DECL_P (base)
-      && !may_be_aliased (base))
+      && !may_be_aliased (base)
+      && !(TREE_CODE (base) == VAR_DECL
+	   && !DECL_EXTERNAL (base)
+	   && !TREE_STATIC (base)
+	   && local_variable_can_escape (base)))
     return false;
   return true;
 }

gcc/gimplify.c

@@ -116,6 +116,19 @@ mark_addressable (tree x)
       && TREE_CODE (x) != RESULT_DECL)
     return;
   TREE_ADDRESSABLE (x) = 1;
+
+  /* Also mark the artificial SSA_NAME that points to the partition of X.  */
+  if (TREE_CODE (x) == VAR_DECL
+      && !DECL_EXTERNAL (x)
+      && !TREE_STATIC (x)
+      && cfun->gimple_df != NULL
+      && cfun->gimple_df->decls_to_pointers != NULL)
+    {
+      void *namep
+	= pointer_map_contains (cfun->gimple_df->decls_to_pointers, x); 
+      if (namep)
+	TREE_ADDRESSABLE (*(tree *)namep) = 1;
+    }
 }
 
 /* Return a hash value for a formal temporary table entry.  */

gcc/tree.h

@@ -484,9 +484,10 @@ struct GTY(()) tree_base {
 
        TREE_ADDRESSABLE in
            VAR_DECL, PARM_DECL, RESULT_DECL, FUNCTION_DECL, LABEL_DECL
+           SSA_NAME
            all types
            CONSTRUCTOR, IDENTIFIER_NODE
-           STMT_EXPR, it means we want the result of the enclosed expression
+           STMT_EXPR
 
        CALL_EXPR_TAILCALL in
            CALL_EXPR
@@ -1085,15 +1086,18 @@ extern void omp_clause_range_check_failed (const_tree, const char *, int,
 /* In VAR_DECL, PARM_DECL and RESULT_DECL nodes, nonzero means address
    of this is needed.  So it cannot be in a register.
    In a FUNCTION_DECL it has no meaning.
-   In CONSTRUCTOR nodes, it means object constructed must be in memory.
    In LABEL_DECL nodes, it means a goto for this label has been seen
    from a place outside all binding contours that restore stack levels.
+   In an artificial SSA_NAME that points to a stack partition with at least
+   two variables, it means that at least one variable has TREE_ADDRESSABLE.
    In ..._TYPE nodes, it means that objects of this type must be fully
    addressable.  This means that pieces of this object cannot go into
    register parameters, for example.  If this a function type, this
    means that the value must be returned in memory.
+   In CONSTRUCTOR nodes, it means object constructed must be in memory.
    In IDENTIFIER_NODEs, this means that some extern decl for this name
-   had its address taken.  That matters for inline functions.  */
+   had its address taken.  That matters for inline functions.
+   In a STMT_EXPR, it means we want the result of the enclosed expression.  */
 #define TREE_ADDRESSABLE(NODE) ((NODE)->base.addressable_flag)
 
 /* Set on a CALL_EXPR if the call is in a tail position, ie. just before the