cmd/asm: add RDTIME{L,H}.W, RDTIME.D support for loong64

Instruction formats: rdtime rd, rj

The RDTIME family of instructions are used to read constant frequency timer
information, the stable counter value is written into the general register
rd, and the counter id information is written into the general register rj.
(Note: both of its register operands are outputs).

Ref: https://loongson.github.io/LoongArch-Documentation/LoongArch-Vol1-EN.html

Change-Id: Ida5bbb28316ef70b5f616dac3e6fa6f2e77875b5
Reviewed-on: https://go-review.googlesource.com/c/go/+/421655
Reviewed-by: xiaodong liu <[email protected]>
Reviewed-by: WANG Xuerui <[email protected]>
Reviewed-by: Wayne Zuo <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
Run-TryBot: Wayne Zuo <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Meidan Li <[email protected]>

Author: abner-chenc

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

@@ -44,6 +44,17 @@ func IsLoong64MUL(op obj.As) bool {
 	return false
 }
 
+// IsLoong64RDTIME reports whether the op (as defined by an loong64.A*
+// constant) is one of the RDTIMELW/RDTIMEHW/RDTIMED instructions that
+// require special handling.
+func IsLoong64RDTIME(op obj.As) bool {
+	switch op {
+	case loong64.ARDTIMELW, loong64.ARDTIMEHW, loong64.ARDTIMED:
+		return true
+	}
+	return false
+}
+
 func loong64RegisterNumber(name string, n int16) (int16, bool) {
 	switch name {
 	case "F":

src/cmd/asm/internal/asm/asm.go

@@ -642,6 +642,18 @@ func (p *Parser) asmInstruction(op obj.As, cond string, a []obj.Addr) {
 				prog.Reg = p.getRegister(prog, op, &a[1])
 				break
 			}
+
+			if arch.IsLoong64RDTIME(op) {
+				// The Loong64 RDTIME family of instructions is a bit special,
+				// in that both its register operands are outputs
+				prog.To = a[0]
+				if a[1].Type != obj.TYPE_REG {
+					p.errorf("invalid addressing modes for 2nd operand to %s instruction, must be register", op)
+					return
+				}
+				prog.RegTo2 = a[1].Reg
+				break
+			}
 		}
 		prog.From = a[0]
 		prog.To = a[1]

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

@@ -218,3 +218,7 @@ lable2:
 	CMPGEF	F4, R5			// a090130c
 	CMPGED	F4, R5			// a090230c
 	CMPEQD	F4, R5			// a010220c
+
+	RDTIMELW R4, R0			// 80600000
+	RDTIMEHW R4, R0			// 80640000
+	RDTIMED  R4, R5			// 85680000

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

@@ -391,6 +391,11 @@ const (
 	AMOVVF
 	AMOVVD
 
+	// 2.2.10. Other Miscellaneous Instructions
+	ARDTIMELW
+	ARDTIMEHW
+	ARDTIMED
+
 	ALAST
 
 	// aliases