gcc: add support for recursion

c-print-for-loop/main.c

@@ -5,6 +5,7 @@ void _start(void)
 {
 	asm ("law 04000");
 	asm ("dac 209");
+	asm ("law 03000");
 	asm ("dac 208");
 
 	int c;

c-test-recursion/Makefile

@@ -0,0 +1 @@
+include ../common/common.mk

c-test-recursion/main.c

@@ -0,0 +1,30 @@
+static void putc();
+
+static void foo(int);
+
+void _start(void)
+{
+	/* TODO: handle sp/fp init better -- separate crt0.S? */
+	asm ("law 03000");
+	asm ("dac 209");
+	asm ("law 04000");
+	asm ("dac 208");
+
+	foo(20);
+
+	asm ("hlt");
+	__builtin_unreachable();
+}
+
+static void putc() {
+	asm ("lio %0" :  : "r"(027) : "io");
+	asm ("tyo");
+}
+
+static void foo(int n)
+{
+	if (n != 0) {
+		putc();
+		foo(n - 1);
+	}
+}