Index: dump-parse-tree.c
===================================================================
--- dump-parse-tree.c	(Revision 278025)
+++ dump-parse-tree.c	(Arbeitskopie)
@@ -57,6 +57,15 @@ static void show_attr (symbol_attribute *, const c
 /* Allow dumping of an expression in the debugger.  */
 void gfc_debug_expr (gfc_expr *);
 
+void debug (gfc_namespace *ns)
+{
+  FILE *tmp = dumpfile;
+  dumpfile = stderr;
+  show_namespace (ns);
+  fputc ('\n', dumpfile);
+  dumpfile = tmp;
+}
+
 void debug (symbol_attribute *attr)
 {
   FILE *tmp = dumpfile;
@@ -1889,6 +1898,9 @@ show_code_node (int level, gfc_code *c)
       break;
 
     case EXEC_INIT_ASSIGN:
+      fputs ("INIT_", dumpfile);
+      /* Fallthrough */
+
     case EXEC_ASSIGN:
       fputs ("ASSIGN ", dumpfile);
       show_expr (c->expr1);
Index: frontend-passes.c
===================================================================
--- frontend-passes.c	(Revision 278025)
+++ frontend-passes.c	(Arbeitskopie)
@@ -57,6 +57,7 @@ static int call_external_blas (gfc_code **, int *,
 static int matmul_temp_args (gfc_code **, int *,void *data);
 static int index_interchange (gfc_code **, int*, void *);
 static bool is_fe_temp (gfc_expr *e);
+static void replace_intent_in (gfc_namespace *);
 
 #ifdef CHECKING_P
 static void check_locus (gfc_namespace *);
@@ -1467,6 +1468,7 @@ optimize_namespace (gfc_namespace *ns)
 
   if (flag_frontend_optimize)
     {
+      replace_intent_in (ns);
       gfc_code_walker (&ns->code, simplify_io_impl_do, dummy_expr_callback, NULL);
       gfc_code_walker (&ns->code, convert_do_while, dummy_expr_callback, NULL);
       gfc_code_walker (&ns->code, convert_elseif, dummy_expr_callback, NULL);
@@ -5503,3 +5505,132 @@ gfc_check_externals (gfc_namespace *ns)
 
   gfc_errors_to_warnings (false);
 }
+
+/*  For scalar INTENT(IN) variables or for variables where we know
+    their value is not changed, we can replace them by an auxiliary
+    variable whose value is set on procedure entry.  */
+
+typedef struct sym_replacement
+{
+  gfc_symbol *original;
+  gfc_symtree *replacement_symtree;
+  bool referenced;
+
+} sym_replace;
+
+/* Callback function - replace expression if possible, and set
+   sr->referenced if this was done (so we know we need to generate
+   the assignment statement).  */
+
+static int
+replace_symbol_in_expr (gfc_expr **e, int *walk_subtrees ATTRIBUTE_UNUSED,
+			void *data)
+{
+  gfc_expr *expr = *e;
+  sym_replacement *sr;
+
+  if (expr->expr_type != EXPR_VARIABLE || expr->symtree == NULL)
+    return 0;
+
+  sr = (sym_replacement *) data;
+
+  if (expr->symtree->n.sym == sr->original)
+    {
+      expr->symtree = sr->replacement_symtree;
+      sr->referenced = true;
+    }
+
+  return 0;
+}
+
+/* Replace INTENT(IN) scalar variables by assigning their values to
+   temporary variables.  We really only want to use this for the
+   simplest cases, all the fancy stuff is excluded.  */
+
+static void
+replace_intent_in (gfc_namespace *ns)
+{
+  gfc_formal_arglist *f;
+  gfc_namespace *ns_c;
+
+  if (ns == NULL || ns->proc_name == NULL || gfc_elemental (ns->proc_name)
+      || ns->proc_name->attr.entry_master)
+    return;
+
+  for (f = ns->proc_name->formal; f; f = f->next)
+    {
+      if (f->sym == NULL || f->sym->attr.dimension || f->sym->attr.allocatable
+	  || f->sym->attr.optional || f->sym->attr.pointer
+	  || f->sym->attr.codimension || f->sym->attr.value
+	  || f->sym->attr.proc_pointer || f->sym->attr.target
+	  || f->sym->attr.asynchronous
+	  || f->sym->ts.type == BT_CHARACTER || f->sym->ts.type == BT_DERIVED
+	  || f->sym->ts.type == BT_CLASS)
+	continue;
+
+      /* TODO: It could also be possible to check if the variable can
+	 actually not be changed by appearing in a variable
+	 definition context or by being passed as an argument to a
+	 procedure where it could be changed.  */
+
+      if (f->sym->attr.intent == INTENT_IN)
+	{
+	  gfc_symtree *symtree;
+	  gfc_symbol *replacement;
+	  sym_replace sr;
+
+	  char name[GFC_MAX_SYMBOL_LEN + 1];
+	  snprintf (name, GFC_MAX_SYMBOL_LEN, "__dummy_%d_%s", var_num++,
+		    f->sym->name);
+
+	  if (gfc_get_sym_tree (name, ns, &symtree, false) != 0)
+	    gcc_unreachable ();
+
+	  replacement = symtree->n.sym;
+	  replacement->ts = f->sym->ts;
+	  replacement->attr.flavor = FL_VARIABLE;
+	  replacement->attr.fe_temp = 1;
+	  replacement->attr.referenced = 1;
+	  replacement->declared_at = f->sym->declared_at;
+	  gfc_commit_symbol (replacement);
+
+	  sr.original = f->sym;
+	  sr.replacement_symtree = symtree;
+	  sr.referenced = false;
+
+	  gfc_code_walker (&ns->code, gfc_dummy_code_callback,
+			   replace_symbol_in_expr, (void *) &sr);
+
+	  for (ns_c = ns->contained; ns_c != NULL; ns_c = ns_c->sibling)
+	    gfc_code_walker (&ns_c->code, gfc_dummy_code_callback,
+			     replace_symbol_in_expr, (void *) &sr);
+
+	  if (sr.referenced)
+	    {
+	      gfc_code *n;
+	      gfc_symtree *formal_symtree;
+	      gfc_code **c;
+
+	      /* Generate statement __tmp_42_foo = foo .   */
+	      n = XCNEW (gfc_code);
+	      n->op = EXEC_ASSIGN;
+	      n->expr1 = gfc_lval_expr_from_sym (replacement);
+	      n->expr1->where = f->sym->declared_at;
+	      formal_symtree = gfc_find_symtree (ns->sym_root, f->sym->name);
+	      n->expr2 = gfc_get_variable_expr (formal_symtree);
+	      n->expr2->where = f->sym->declared_at;
+	      n->loc = f->sym->declared_at;
+
+	      /* Put this statement after the initialization
+		 assignment statements.  */
+	      
+	      for (c = &ns->code; *c != NULL && (*c)->op == EXEC_INIT_ASSIGN;
+		   c = &(*c)->next)
+		;
+
+	      n->next = (*c);
+	      (*c) = n;
+	    }
+	}
+    }
+}