cmd/internal/obj/loong64: add {V,XV}MUL{B/H/W/V} and {V,XV}MUH{B/H/W/V}[U] instructions support

Go asm syntax:
	 VMUL{B/H/W/V}		VK, VJ, VD
	 VMUH{B/H/W/V}[U]	VK, VJ, VD
	XVMUL{B/H/W/V}		XK, XJ, XD
	XVMUH{B/H/W/V}[U]	XK, XJ, XD

Equivalent platform assembler syntax:
	 vmul.{b/h/w/d}		vd, vj, vk
	 vmuh.{b/h/w/d}[u]	vd, vj, vk
	xvmul.{b/h/w/d}		xd, xj, xk
	xvmuh.{b/h/w/d}[u]	xd, xj, xk

Change-Id: I2f15a5b4b6303a0f82cb85114477f58e1b5fd950
Reviewed-on: https://go-review.googlesource.com/c/go/+/636375
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: abner chenc <chenguoqi@loongson.cn>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: abner chenc <chenguoqi@loongson.cn>

src/cmd/asm/internal/asm/testdata/loong64enc1.s

@@ -775,3 +775,29 @@ lable2:
 	XVILVHH		X3, X2, X1	// 418c1c75
 	XVILVHW		X3, X2, X1	// 410c1d75
 	XVILVHV		X3, X2, X1	// 418c1d75
+
+	// [X]VMUL{B/H/W/V} and [X]VMUH{B/H/W/V}[U] instructions
+	VMULB		V1, V2, V3	// 43048470
+	VMULH		V1, V2, V3	// 43848470
+	VMULW		V1, V2, V3	// 43048570
+	VMULV		V1, V2, V3	// 43848570
+	VMUHB		V1, V2, V3	// 43048670
+	VMUHH		V1, V2, V3	// 43848670
+	VMUHW		V1, V2, V3	// 43048770
+	VMUHV		V1, V2, V3	// 43848770
+	VMUHBU		V1, V2, V3	// 43048870
+	VMUHHU		V1, V2, V3	// 43848870
+	VMUHWU		V1, V2, V3	// 43048970
+	VMUHVU		V1, V2, V3	// 43848970
+	XVMULB		X3, X2, X1	// 410c8474
+	XVMULH		X3, X2, X1	// 418c8474
+	XVMULW		X3, X2, X1	// 410c8574
+	XVMULV		X3, X2, X1	// 418c8574
+	XVMUHB		X3, X2, X1	// 410c8674
+	XVMUHH		X3, X2, X1	// 418c8674
+	XVMUHW		X3, X2, X1	// 410c8774
+	XVMUHV		X3, X2, X1	// 418c8774
+	XVMUHBU		X3, X2, X1	// 410c8874
+	XVMUHHU		X3, X2, X1	// 418c8874
+	XVMUHWU		X3, X2, X1	// 410c8974
+	XVMUHVU		X3, X2, X1	// 418c8974

src/cmd/internal/obj/loong64/a.out.go

@@ -876,6 +876,32 @@ const (
 	AXVILVHW
 	AXVILVHV
 
+	// LSX and LASX integer mul instructions
+	AVMULB
+	AVMULH
+	AVMULW
+	AVMULV
+	AVMUHB
+	AVMUHH
+	AVMUHW
+	AVMUHV
+	AVMUHBU
+	AVMUHHU
+	AVMUHWU
+	AVMUHVU
+	AXVMULB
+	AXVMULH
+	AXVMULW
+	AXVMULV
+	AXVMUHB
+	AXVMUHH
+	AXVMUHW
+	AXVMUHV
+	AXVMUHBU
+	AXVMUHHU
+	AXVMUHWU
+	AXVMUHVU
+
 	ALAST
 
 	// aliases

src/cmd/internal/obj/loong64/anames.go

@@ -381,5 +381,29 @@ var Anames = []string{
 	"XVILVHH",
 	"XVILVHW",
 	"XVILVHV",
+	"VMULB",
+	"VMULH",
+	"VMULW",
+	"VMULV",
+	"VMUHB",
+	"VMUHH",
+	"VMUHW",
+	"VMUHV",
+	"VMUHBU",
+	"VMUHHU",
+	"VMUHWU",
+	"VMUHVU",
+	"XVMULB",
+	"XVMULH",
+	"XVMULW",
+	"XVMULV",
+	"XVMUHB",
+	"XVMUHH",
+	"XVMUHW",
+	"XVMUHV",
+	"XVMUHBU",
+	"XVMUHHU",
+	"XVMUHWU",
+	"XVMUHVU",
 	"LAST",
 }

src/cmd/internal/obj/loong64/asm.go

@@ -1555,6 +1555,18 @@ func buildop(ctxt *obj.Link) {
 			opset(AVILVHH, r0)
 			opset(AVILVHW, r0)
 			opset(AVILVHV, r0)
+			opset(AVMULB, r0)
+			opset(AVMULH, r0)
+			opset(AVMULW, r0)
+			opset(AVMULV, r0)
+			opset(AVMUHB, r0)
+			opset(AVMUHH, r0)
+			opset(AVMUHW, r0)
+			opset(AVMUHV, r0)
+			opset(AVMUHBU, r0)
+			opset(AVMUHHU, r0)
+			opset(AVMUHWU, r0)
+			opset(AVMUHVU, r0)
 
 		case AXVSEQB:
 			opset(AXVSEQH, r0)
@@ -1568,6 +1580,18 @@ func buildop(ctxt *obj.Link) {
 			opset(AXVILVHH, r0)
 			opset(AXVILVHW, r0)
 			opset(AXVILVHV, r0)
+			opset(AXVMULB, r0)
+			opset(AXVMULH, r0)
+			opset(AXVMULW, r0)
+			opset(AXVMULV, r0)
+			opset(AXVMUHB, r0)
+			opset(AXVMUHH, r0)
+			opset(AXVMUHW, r0)
+			opset(AXVMUHV, r0)
+			opset(AXVMUHBU, r0)
+			opset(AXVMUHHU, r0)
+			opset(AXVMUHWU, r0)
+			opset(AXVMUHVU, r0)
 
 		case AVANDB:
 			opset(AVORB, r0)
@@ -2986,6 +3010,54 @@ func (c *ctxt0) oprrr(a obj.As) uint32 {
 		return 0xea3a << 15 // xvilvh.w
 	case AXVILVHV:
 		return 0xea3b << 15 // xvilvh.d
+	case AVMULB:
+		return 0xe108 << 15 // vmul.b
+	case AVMULH:
+		return 0xe109 << 15 // vmul.h
+	case AVMULW:
+		return 0xe10a << 15 // vmul.w
+	case AVMULV:
+		return 0xe10b << 15 // vmul.d
+	case AVMUHB:
+		return 0xe10c << 15 // vmuh.b
+	case AVMUHH:
+		return 0xe10d << 15 // vmuh.h
+	case AVMUHW:
+		return 0xe10e << 15 // vmuh.w
+	case AVMUHV:
+		return 0xe10f << 15 // vmuh.d
+	case AVMUHBU:
+		return 0xe110 << 15 // vmuh.bu
+	case AVMUHHU:
+		return 0xe111 << 15 // vmuh.hu
+	case AVMUHWU:
+		return 0xe112 << 15 // vmuh.wu
+	case AVMUHVU:
+		return 0xe113 << 15 // vmuh.du
+	case AXVMULB:
+		return 0xe908 << 15 // xvmul.b
+	case AXVMULH:
+		return 0xe909 << 15 // xvmul.h
+	case AXVMULW:
+		return 0xe90a << 15 // xvmul.w
+	case AXVMULV:
+		return 0xe90b << 15 // xvmul.d
+	case AXVMUHB:
+		return 0xe90c << 15 // xvmuh.b
+	case AXVMUHH:
+		return 0xe90d << 15 // xvmuh.h
+	case AXVMUHW:
+		return 0xe90e << 15 // xvmuh.w
+	case AXVMUHV:
+		return 0xe90f << 15 // xvmuh.d
+	case AXVMUHBU:
+		return 0xe910 << 15 // xvmuh.bu
+	case AXVMUHHU:
+		return 0xe911 << 15 // xvmuh.hu
+	case AXVMUHWU:
+		return 0xe912 << 15 // xvmuh.wu
+	case AXVMUHVU:
+		return 0xe913 << 15 // xvmuh.du
 	}
 
 	if a < 0 {