cmd/internal/obj/mips: add MADD/MSUB

This CL implements MADD&MSUB, which are mips32r2 instructions.

Change-Id: I06fe51573569baf3b71536336b34b95ccd24750b
Reviewed-on: https://go-review.googlesource.com/c/go/+/167680
Run-TryBot: Ben Shi <powerman1st@163.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/asm/internal/arch/mips.go

@@ -38,7 +38,8 @@ func IsMIPSMUL(op obj.As) bool {
 	switch op {
 	case mips.AMUL, mips.AMULU, mips.AMULV, mips.AMULVU,
 		mips.ADIV, mips.ADIVU, mips.ADIVV, mips.ADIVVU,
-		mips.AREM, mips.AREMU, mips.AREMV, mips.AREMVU:
+		mips.AREM, mips.AREMU, mips.AREMV, mips.AREMVU,
+		mips.AMADD, mips.AMSUB:
 		return true
 	}
 	return false

src/cmd/asm/internal/asm/testdata/mips.s

@@ -424,7 +424,15 @@ label4:
 	CALL	foo(SB)
 	RET	foo(SB)
 
+	// unary operation
 	NEGW	R1, R2 // 00011023
+	CLZ	R1, R2 // 70221020
+	CLO	R1, R2 // 70221021
+
+	// to (Hi, Lo)
+	MADD	R2, R1 // 70220000
+	MSUB	R2, R1 // 70220004
+	MUL	R2, R1 // 00220018
 
 	// END
 	//

src/cmd/internal/obj/mips/a.out.go

@@ -319,6 +319,7 @@ const (
 	ALL
 	ALLV
 	ALUI
+	AMADD
 	AMOVB
 	AMOVBU
 	AMOVD
@@ -334,6 +335,7 @@ const (
 	AMOVWF
 	AMOVWL
 	AMOVWR
+	AMSUB
 	AMUL
 	AMULD
 	AMULF

src/cmd/internal/obj/mips/anames.go

@@ -46,6 +46,7 @@ var Anames = []string{
 	"LL",
 	"LLV",
 	"LUI",
+	"MADD",
 	"MOVB",
 	"MOVBU",
 	"MOVD",
@@ -61,6 +62,7 @@ var Anames = []string{
 	"MOVWF",
 	"MOVWL",
 	"MOVWR",
+	"MSUB",
 	"MUL",
 	"MULD",
 	"MULF",

src/cmd/internal/obj/mips/asm0.go

@@ -959,6 +959,8 @@ func buildop(ctxt *obj.Link) {
 			opset(ADIVU, r0)
 			opset(AMULU, r0)
 			opset(ADIV, r0)
+			opset(AMADD, r0)
+			opset(AMSUB, r0)
 
 		case AMULV:
 			opset(ADIVV, r0)
@@ -1785,6 +1787,10 @@ func (c *ctxt0) oprrr(a obj.As) uint32 {
 		return SP(3, 4) | OP(4, 1)
 	case ACLZ:
 		return SP(3, 4) | OP(4, 0)
+	case AMADD:
+		return SP(3, 4) | OP(0, 0)
+	case AMSUB:
+		return SP(3, 4) | OP(0, 4)
 	}
 
 	if a < 0 {