added tail_optimize code

optimize.c

@@ -2,6 +2,7 @@
 
 
 #include <dcw.h>
+#include <string.h>
 #include "struct.h"
 
 
@@ -9,10 +10,19 @@ BOOL opt;		/* opt     == perform optimizations    */
 BOOL verbose;		/* verbose == be verbose - diagnostics */
 
 
+/*
+/^#ifdef HASPROTOS
+!/endif$
+stat %
+*/
+
+
 #ifdef HASPROTOS
-static void optimize_decln( declnlist );
+static void optimize_decln( decln );
+static BOOL tail_optimize( decln );
 #else
 static void optimize_decln();
+static BOOL tail_optimize();
 #endif
 
 
@@ -35,7 +45,7 @@ void optimize( d ) declnlist d;
 }
 
 
-static void optimize_decln( d ) declnlist d;	/* JUST THE FIRST */
+static void optimize_decln( d ) decln d;
 {
 	int		t, e, ne;
 	shapelist	s;
@@ -61,7 +71,8 @@ static void optimize_decln( d ) declnlist d;	/* JUST THE FIRST */
 	d->TagField	= ne>1 || ( ne>0 && t>2);
 	d->Union	= ne>1;
 	d->UseNull	= ne>0 && firstempty;
-	d->PutLoop	= TRUE;
+
+	d->PutLoop	= tail_optimize( d );
 
 	if( verbose )
 	{
@@ -88,3 +99,41 @@ static void optimize_decln( d ) declnlist d;	/* JUST THE FIRST */
 	ASSERT( implies(d->Union,d->TagField),
 		("optimizer error: type %s has Union&!TagField\n",d->name) );
 }
+
+
+/*
+	Given a data decln, check if a tail recursion optimization is possible.
+	This is when the last print item of any shape is a number corresponding
+	to a field that is the same type as the decln itself.
+
+	Return TRUE if the optimization is possible.
+ */
+
+static BOOL tail_optimize( d ) decln d;
+{
+	shapelist	s;
+	printlist	pl;
+	param		p;
+	int		n;
+
+	for( s = d->shapes; s != NULL; s = s->next )
+	{
+		if( s->pl != NULL )
+		{
+			/* find the last print item */
+
+			for( pl = s->pl; pl->next != NULL; pl = pl->next );
+
+			if( pl->item->tag == printitem_is_num )
+			{
+				p = findnthparam( pl->item->num, s->params,
+						  s->name, d->name );
+				if( streq( p->type, d->name ) )
+				{
+					return TRUE;
+				}
+			}
+		}
+	}
+	return FALSE;
+}