Add original unix v6

source/fort/rt/r4.s

@@ -0,0 +1,65 @@
+/
+/
+
+/ r4 -- short integer arithmetic
+
+.globl	iad2
+.globl	isb2
+.globl	imp2
+.globl	idv2
+.globl	i2i4
+.globl	i1i4
+.globl	i4i2
+.globl	i4i1
+.globl	ing2
+.globl	rval2
+.globl	rval1
+.globl	l2l1
+
+iad2:
+	add	(sp)+,(sp)
+	jmp	*(r4)+
+
+isb2:
+	sub	(sp)+,(sp)
+	jmp	*(r4)+
+
+imp2:
+	mov	(sp)+,r1
+	mul	(sp)+,r1
+	mov	r1,-(sp)
+	jmp	*(r4)+
+
+idv2:
+	mov	2(sp),r1
+	sxt	r0
+	div	(sp)+,r0
+	mov	r0,(sp)
+	jmp	*(r4)+
+
+i4i2:
+i4i1:
+	tst	(sp)+
+	jmp	*(r4)+
+
+i2i4:
+i1i4:
+	tst	(sp)
+	sxt	-(sp)
+	jmp	*(r4)+
+
+ing2:
+	neg	(sp)
+	jmp	*(r4)+
+
+rval2:
+	mov	*(r4)+,-(sp)
+	jmp	*(r4)+
+
+rval1:
+	movb	*(r4)+,r0
+	mov	r0,-(sp)
+
+l2l1:
+	jmp	*(r4)+
+