1 files changed, 113 insertions, 0 deletions
diff --git a/gcc/c-semantics.c b/gcc/c-semantics.c
index 2e0d537..eea9f92 100644
--- a/gcc/c-semantics.c
+++ b/gcc/c-semantics.c
@@ -36,6 +36,119 @@ Boston, MA 02111-1307, USA.  */
 #include "output.h"
 #include "timevar.h"
 
+static tree prune_unused_decls PARAMS ((tree *, int *, void *));
+
+/* Create an empty statement tree rooted at T.  */
+
+void
+begin_stmt_tree (t)
+     tree *t;
+{
+  /* We create a trivial EXPR_STMT so that last_tree is never NULL in
+     what follows.  We remove the extraneous statement in
+     finish_stmt_tree.  */
+  *t = build_nt (EXPR_STMT, void_zero_node);
+  last_tree = *t;
+  last_expr_type = NULL_TREE;
+}
+
+/* T is a statement.  Add it to the statement-tree.  */
+
+void
+add_stmt (t)
+     tree t;
+{
+  /* Add T to the statement-tree.  */
+  TREE_CHAIN (last_tree) = t;
+  last_tree = t;
+  /* When we expand a statement-tree, we must know whether or not the
+     statements are full-expresions.  We record that fact here.  */
+  STMT_IS_FULL_EXPR_P (last_tree) = stmts_are_full_exprs_p ();
+}
+
+/* Remove declarations of internal variables that are not used from a
+   stmt tree.  To qualify, the variable must have a name and must have
+   a zero DECL_SOURCE_LINE.  We tried to remove all variables for
+   which TREE_USED was false, but it turns out that there's tons of
+   variables for which TREE_USED is false but that are still in fact
+   used.  */
+
+static tree
+prune_unused_decls (tp, walk_subtrees, data)
+     tree *tp;
+     int *walk_subtrees ATTRIBUTE_UNUSED;
+     void *data ATTRIBUTE_UNUSED;
+{
+  tree t = *tp;
+
+  if (t == NULL_TREE)
+    {
+      *walk_subtrees = 0;
+      return NULL_TREE;
+    }
+
+  if (TREE_CODE (t) == DECL_STMT)
+    {
+      tree d = DECL_STMT_DECL (t);
+      if (!TREE_USED (d) && DECL_NAME (d) && DECL_SOURCE_LINE (d) == 0)
+	{
+	  *tp = TREE_CHAIN (t);
+	  /* Recurse on the new value of tp, otherwise we will skip
+	     the next statement.  */
+	  return prune_unused_decls (tp, walk_subtrees, data);
+	}
+    }
+  else if (TREE_CODE (t) == SCOPE_STMT)
+    {
+      /* Remove all unused decls from the BLOCK of this SCOPE_STMT.  */
+      tree block = SCOPE_STMT_BLOCK (t);
+
+      if (block)
+	{
+	  tree *vp;
+
+	  for (vp = &BLOCK_VARS (block); *vp; )
+	    {
+	      tree v = *vp;
+	      if (! TREE_USED (v) && DECL_NAME (v) && DECL_SOURCE_LINE (v) == 0)
+		*vp = TREE_CHAIN (v);  /* drop */
+	      else
+		vp = &TREE_CHAIN (v);  /* advance */
+	    }
+	  /* If there are now no variables, the entire BLOCK can be dropped.
+	     (This causes SCOPE_NULLIFIED_P (t) to be true.)  */
+	  if (BLOCK_VARS (block) == NULL_TREE)
+	    SCOPE_STMT_BLOCK (t) = NULL_TREE;
+	}
+    }
+  return NULL_TREE;
+}
+
+/* Finish the statement tree rooted at T.  */
+
+void
+finish_stmt_tree (t)
+     tree *t;
+{
+  tree stmt;
+  
+  /* Remove the fake extra statement added in begin_stmt_tree.  */
+  stmt = TREE_CHAIN (*t);
+  *t = stmt;
+  last_tree = NULL_TREE;
+
+  /* Remove unused decls from the stmt tree.  */
+  walk_stmt_tree (t, prune_unused_decls, NULL);
+
+  if (cfun)
+    {
+      /* The line-number recorded in the outermost statement in a function
+	 is the line number of the end of the function.  */
+      STMT_LINENO (stmt) = lineno;
+      STMT_LINENO_FOR_FN_P (stmt) = 1;
+    }
+}
+
 /* Build a generic statement based on the given type of node and
    arguments. Similar to `build_nt', except that we set
    TREE_COMPLEXITY to be the current line number.  */