Index: sys/arch/shark/isa/isa_irq.S
===================================================================
RCS file: /cvsroot/src/sys/arch/shark/isa/isa_irq.S,v
retrieving revision 1.16
diff -u -p -r1.16 isa_irq.S
--- sys/arch/shark/isa/isa_irq.S	2 Dec 2013 18:36:11 -0000	1.16
+++ sys/arch/shark/isa/isa_irq.S	30 Jan 2018 19:20:35 -0000
@@ -182,13 +182,14 @@ ASENTRY_NP(irq_entry)
 	 * This would benefit from a special ffs type routine
 	 */
 
-	mov	r9, #(NIPL - 1)
+	mov	r9, #NIPL
 	ldr	r5, .Lspl_masks
 
 .Lfind_highest_ipl:
+	subs	r9, r9, 1
+	blt	.Lwtf
 	ldr	r2, [r5, r9, lsl #2]
 	tst	r8, r2
-	subeq	r9, r9, #1
 	beq	.Lfind_highest_ipl
 
 	/* r9 = SPL level of highest priority interrupt */
@@ -291,6 +292,15 @@ nextirq:
 	/* NOT REACHED */
 	b	. - 8
 
+.Lwtf:
+	adr	r0, .Lwtf_panicmsg
+	mov	r1, r8
+	bl	_C_LABEL(panic)
+	/* NOTREACHED */
+.Lwtf_panicmsg:
+	.asciz	"WTF? r8=0x%08x""
+	.balign	4
+
 .Lcurrent_mask:
 	.word	_C_LABEL(current_mask)	/* irq's that are usable */