test/codegen: improve arithmetic tests

This CL fixes several typos and adds two more cases
to arithmetic test.

Change-Id: I086560162ea351e2166866e444e2317da36c1729
Reviewed-on: https://go-review.googlesource.com/c/145210
Run-TryBot: Ben Shi <powerman1st@163.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

test/codegen/arithmetic.go

@@ -324,10 +324,10 @@ func MULA(a, b, c uint32) (uint32, uint32, uint32) {
 	// arm:`MULA`,-`MUL\s`
 	// arm64:`MADDW`,-`MULW`
 	r0 := a*b + c
-	// arm:`MULA`-`MUL\s`
+	// arm:`MULA`,-`MUL\s`
 	// arm64:`MADDW`,-`MULW`
 	r1 := c*79 + a
-	// arm:`ADD`,-`MULA`-`MUL\s`
+	// arm:`ADD`,-`MULA`,-`MUL\s`
 	// arm64:`ADD`,-`MADD`,-`MULW`
 	r2 := b*64 + c
 	return r0, r1, r2
@@ -335,12 +335,14 @@ func MULA(a, b, c uint32) (uint32, uint32, uint32) {
 
 func MULS(a, b, c uint32) (uint32, uint32, uint32) {
 	// arm/7:`MULS`,-`MUL\s`
+	// arm/6:`SUB`,`MUL\s`,-`MULS`
 	// arm64:`MSUBW`,-`MULW`
 	r0 := c - a*b
-	// arm/7:`MULS`-`MUL\s`
+	// arm/7:`MULS`,-`MUL\s`
+	// arm/6:`SUB`,`MUL\s`,-`MULS`
 	// arm64:`MSUBW`,-`MULW`
 	r1 := a - c*79
-	// arm/7:`SUB`,-`MULS`-`MUL\s`
+	// arm/7:`SUB`,-`MULS`,-`MUL\s`
 	// arm64:`SUB`,-`MSUBW`,-`MULW`
 	r2 := c - b*64
 	return r0, r1, r2