cmd/internal/obj/loong64: add {V,XV}NEG{B/H/W/V} instructions support

Go asm syntax:
	 VNEG{B/H/W/V}		VJ, VD
	XVNEG{B/H/W/V}		XJ, XD

Equivalent platform assembler syntax:
	 vneg.{b/h/w/d}		vd, vj
	xvneg.{b/h/w/d}		xd, xj

Change-Id: Ie0a82a434b0ffbcb77425a65b96eff56e030028c
Reviewed-on: https://go-review.googlesource.com/c/go/+/635935
Reviewed-by: abner chenc <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Reviewed-by: David Chase <[email protected]>

Author: sophie-zhao

Diff for: src/cmd/asm/internal/asm/testdata/loong64enc1.s

@@ -849,3 +849,13 @@ lable2:
 	XVFRECIPD	X2, X1		// 41f89c76
 	XVFRSQRTF	X2, X1		// 41049d76
 	XVFRSQRTD	X2, X1		// 41089d76
+
+	// [X]VNEG{B/H/W/V} instructions
+	VNEGB		V1, V2		// 22309c72
+	VNEGH		V1, V2		// 22349c72
+	VNEGW		V1, V2		// 22389c72
+	VNEGV		V1, V2		// 223c9c72
+	XVNEGB		X2, X1		// 41309c76
+	XVNEGH		X2, X1		// 41349c76
+	XVNEGW		X2, X1		// 41389c76
+	XVNEGV		X2, X1		// 413c9c76

Diff for: src/cmd/internal/obj/loong64/a.out.go

@@ -950,6 +950,16 @@ const (
 	AXVFRSQRTF
 	AXVFRSQRTD
 
+	// LSX and LASX integer neg instructions
+	AVNEGB
+	AVNEGH
+	AVNEGW
+	AVNEGV
+	AXVNEGB
+	AXVNEGH
+	AXVNEGW
+	AXVNEGV
+
 	ALAST
 
 	// aliases

Diff for: src/cmd/internal/obj/loong64/anames.go

@@ -1659,6 +1659,10 @@ func buildop(ctxt *obj.Link) {
 			opset(AVFRECIPD, r0)
 			opset(AVFRSQRTF, r0)
 			opset(AVFRSQRTD, r0)
+			opset(AVNEGB, r0)
+			opset(AVNEGH, r0)
+			opset(AVNEGW, r0)
+			opset(AVNEGV, r0)
 
 		case AXVPCNTB:
 			opset(AXVPCNTH, r0)
@@ -1670,6 +1674,10 @@ func buildop(ctxt *obj.Link) {
 			opset(AXVFRECIPD, r0)
 			opset(AXVFRSQRTF, r0)
 			opset(AXVFRSQRTD, r0)
+			opset(AXVNEGB, r0)
+			opset(AXVNEGH, r0)
+			opset(AXVNEGW, r0)
+			opset(AXVNEGV, r0)
 
 		case AVADDB:
 			opset(AVADDH, r0)
@@ -3366,6 +3374,22 @@ func (c *ctxt0) oprr(a obj.As) uint32 {
 		return 0x1da741 << 10 // xvfrsqrt.s
 	case AXVFRSQRTD:
 		return 0x1da742 << 10 // xvfrsqrt.d
+	case AVNEGB:
+		return 0x1ca70c << 10 // vneg.b
+	case AVNEGH:
+		return 0x1ca70d << 10 // vneg.h
+	case AVNEGW:
+		return 0x1ca70e << 10 // vneg.w
+	case AVNEGV:
+		return 0x1ca70f << 10 // vneg.d
+	case AXVNEGB:
+		return 0x1da70c << 10 // xvneg.b
+	case AXVNEGH:
+		return 0x1da70d << 10 // xvneg.h
+	case AXVNEGW:
+		return 0x1da70e << 10 // xvneg.w
+	case AXVNEGV:
+		return 0x1da70f << 10 // xvneg.d
 	}
 
 	c.ctxt.Diag("bad rr opcode %v", a)