cmd/asm: add rotr/drotr for mips64

This CL encodes:

ROTR rd, rt, sa
ROTRV rd, rt, rs

=> ROTR (SCON|REG), (REG,)? REG

DROTR rd, rt, sa
DROTR32 rd, rt, sa
DROTRV rd, rt, rs

=> ROTRV (SCON|REG), (REG,)? REG

Note: ROTRV will handle const over 32
Ref: The MIPS64® Instruction Set Reference Manual Revision 6.05
Change-Id: Ibe69f999b83eb43843d088cf1ac5a13c995269a5
Reviewed-on: https://go-review.googlesource.com/c/go/+/280114
Trust: Meng Zhuo <mzh@golangcn.org>
Run-TryBot: Meng Zhuo <mzh@golangcn.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>

src/cmd/asm/internal/asm/testdata/mips64.s

@@ -407,6 +407,8 @@ label4:
 	SRLV	R27, R6, R17	// 03668816
 	SRA	R11, R19, R20	// 0173a007
 	SRAV	R20, R19, R19	// 02939817
+	ROTR	R19, R18, R20	// 0272a046
+	ROTRV	R9, R13, R16	// 012d8056
 
 //	LSHW rreg ',' rreg
 //	{
@@ -418,6 +420,8 @@ label4:
 	SRLV	R27, R6   	// 03663016
 	SRA	R11, R19	// 01739807
 	SRAV	R20, R19	// 02939817
+	ROTR	R20, R19	// 02939846
+	ROTRV	R16, R9		// 02094856
 
 //	LSHW imm ',' sreg ',' rreg
 //	{
@@ -429,6 +433,8 @@ label4:
 	SRLV	$31, R6, R17	// 00068ffa
 	SRA	$8, R8, R19	// 00089a03
 	SRAV	$19, R8, R7	// 00083cfb
+	ROTR	$12, R8, R3	// 00281b02
+	ROTRV	$8, R22, R22	// 0036b23a
 
 //	LSHW imm ',' rreg
 //	{
@@ -440,6 +446,8 @@ label4:
 	SRLV	$31, R17	// 00118ffa
 	SRA	$3, R12		// 000c60c3
 	SRAV	$12, R3		// 00031b3b
+	ROTR	$12, R8		// 00284302
+	ROTRV	$63, R22	// 0036b7fe
 
 
 //	LAND/LXOR/LNOR/LOR rreg ',' rreg

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

@@ -390,6 +390,8 @@ const (
 	AREM
 	AREMU
 	ARFE
+	AROTR
+	AROTRV
 	ASC
 	ASCV
 	ASGT

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

@@ -78,6 +78,8 @@ var Anames = []string{
 	"REM",
 	"REMU",
 	"RFE",
+	"ROTR",
+	"ROTRV",
 	"SC",
 	"SCV",
 	"SGT",

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

@@ -1022,10 +1022,12 @@ func buildop(ctxt *obj.Link) {
 		case ASLL:
 			opset(ASRL, r0)
 			opset(ASRA, r0)
+			opset(AROTR, r0)
 
 		case ASLLV:
 			opset(ASRAV, r0)
 			opset(ASRLV, r0)
+			opset(AROTRV, r0)
 
 		case ASUB:
 			opset(ASUBU, r0)
@@ -1732,12 +1734,16 @@ func (c *ctxt0) oprrr(a obj.As) uint32 {
 		return OP(0, 6)
 	case ASRA:
 		return OP(0, 7)
+	case AROTR:
+		return OP(8, 6)
 	case ASLLV:
 		return OP(2, 4)
 	case ASRLV:
 		return OP(2, 6)
 	case ASRAV:
 		return OP(2, 7)
+	case AROTRV:
+		return OP(10, 6)
 	case AADDV:
 		return OP(5, 4)
 	case AADDVU:
@@ -1916,6 +1922,8 @@ func (c *ctxt0) opirr(a obj.As) uint32 {
 		return OP(0, 2)
 	case ASRA:
 		return OP(0, 3)
+	case AROTR:
+		return OP(0, 2) | 1<<21
 	case AADDV:
 		return SP(3, 0)
 	case AADDVU:
@@ -2028,12 +2036,16 @@ func (c *ctxt0) opirr(a obj.As) uint32 {
 		return OP(7, 2)
 	case ASRAV:
 		return OP(7, 3)
+	case AROTRV:
+		return OP(7, 2) | 1<<21
 	case -ASLLV:
 		return OP(7, 4)
 	case -ASRLV:
 		return OP(7, 6)
 	case -ASRAV:
 		return OP(7, 7)
+	case -AROTRV:
+		return OP(7, 6) | 1<<21
 
 	case ATEQ:
 		return OP(6, 4)
@@ -2061,7 +2073,8 @@ func vshift(a obj.As) bool {
 	switch a {
 	case ASLLV,
 		ASRLV,
-		ASRAV:
+		ASRAV,
+		AROTRV:
 		return true
 	}
 	return false