diff --git a/mach/mips/libem/compareul.s b/mach/mips/libem/compareul.s
new file mode 100644
index 000000000..dccd92234
--- /dev/null
+++ b/mach/mips/libem/compareul.s
@@ -0,0 +1,39 @@
+#
+.sect .text; .sect .rom; .sect .data; .sect .bss
+
+/*
+ * 64-big unsigned tristate comparison.
+ * Inputs:
+ *    r2r3: left
+ *    r4r5: right
+ * Outputs;
+ *    r2: result
+ */
+
+.sect .text
+.define .compareul
+.compareul:
+	/* Compare high words. */
+
+	sltu at, r3, r5			! if r3<r5, then 1
+	subu at, zero, at		! if r3<r5, then -1
+	bne at, zero, exit
+	nop
+
+	sltu at, r5, r3			! if r3>r5, then 1
+	bne at, zero, exit
+	nop
+
+	/* High words are equal --- compare low words. */
+
+	sltu at, r2, r4			! if r2<r4, then 1
+	subu at, zero, at		! if r2<r4, then -1
+	bne at, zero, exit
+	nop
+
+	sltu at, r4, r2			! if r2>r4, then 1
+exit:
+	mov r2, at
+	jr ra
+	nop
+
diff --git a/mach/mips/mcg/table b/mach/mips/mcg/table
index 321eaea5d..955e09ace 100644
--- a/mach/mips/mcg/table
+++ b/mach/mips/mcg/table
@@ -35,7 +35,7 @@ REGISTERS
 	r22 named("r22")                              int;
 	r23 named("r23")                              int;
 
-	r4r5    named("r4", "r5")   aliases(r4,  r5)  long volatile;
+	r4r5    named("r4", "r5")   aliases(r4,  r5)  long volatilei lret1;
 	r6r7    named("r6", "r7")   aliases(r6,  r7)  long volatile;
 	r8r9    named("r8", "r9")   aliases(r8,  r9)  long volatile;
 	r10r11  named("r10", "r11") aliases(r10, r11) long volatile;
@@ -490,6 +490,11 @@ PATTERNS
         emit "1:"
         cost 20;
 
+    out:(iret)reg = COMPAREUL.I(left:(lret)reg, right:(lret1)reg)
+        emit "jal .compareul"
+        emit "nop"
+        cost 30;
+
     out:(int)reg = COMPAREF.I(left:(float)reg, right:(float)reg)
         with preserved(%left), preserved(%right)
         emit "c.lt.s 0, %left, %right"