cmd/internal/obj,cmd/asm: add vector registers to riscv64 assembler

This adds V0 through V31 as vector registers, which are available on CPUs
that support the V extension.

Change-Id: Ibffee3f9a2cf1d062638715b3744431d72d451ce
Reviewed-on: https://go-review.googlesource.com/c/go/+/595404
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Mark Ryan <markdryan@rivosinc.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: 鹏程汪 <wangpengcheng.pp@bytedance.com>

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

@@ -586,6 +586,10 @@ func archRISCV64(shared bool) *Arch {
 		name := fmt.Sprintf("F%d", i-riscv.REG_F0)
 		register[name] = int16(i)
 	}
+	for i := riscv.REG_V0; i <= riscv.REG_V31; i++ {
+		name := fmt.Sprintf("V%d", i-riscv.REG_V0)
+		register[name] = int16(i)
+	}
 
 	// General registers with ABI names.
 	register["ZERO"] = riscv.REG_ZERO

src/cmd/internal/obj/riscv/cpu.go

@@ -72,7 +72,7 @@ const (
 	REG_X30
 	REG_X31
 
-	// FP register numberings.
+	// Floating Point register numberings.
 	REG_F0
 	REG_F1
 	REG_F2
@@ -106,6 +106,40 @@ const (
 	REG_F30
 	REG_F31
 
+	// Vector register numberings.
+	REG_V0
+	REG_V1
+	REG_V2
+	REG_V3
+	REG_V4
+	REG_V5
+	REG_V6
+	REG_V7
+	REG_V8
+	REG_V9
+	REG_V10
+	REG_V11
+	REG_V12
+	REG_V13
+	REG_V14
+	REG_V15
+	REG_V16
+	REG_V17
+	REG_V18
+	REG_V19
+	REG_V20
+	REG_V21
+	REG_V22
+	REG_V23
+	REG_V24
+	REG_V25
+	REG_V26
+	REG_V27
+	REG_V28
+	REG_V29
+	REG_V30
+	REG_V31
+
 	// This marks the end of the register numbering.
 	REG_END
 

src/cmd/internal/obj/riscv/list.go

@@ -28,6 +28,8 @@ func RegName(r int) string {
 		return fmt.Sprintf("X%d", r-REG_X0)
 	case REG_F0 <= r && r <= REG_F31:
 		return fmt.Sprintf("F%d", r-REG_F0)
+	case REG_V0 <= r && r <= REG_V31:
+		return fmt.Sprintf("V%d", r-REG_V0)
 	default:
 		return fmt.Sprintf("Rgok(%d)", r-obj.RBaseRISCV)
 	}

src/cmd/internal/obj/riscv/obj.go

@@ -1030,6 +1030,11 @@ func regF(r uint32) uint32 {
 	return regVal(r, REG_F0, REG_F31)
 }
 
+// regV returns a vector register.
+func regV(r uint32) uint32 {
+	return regVal(r, REG_V0, REG_V31)
+}
+
 // regAddr extracts a register from an Addr.
 func regAddr(a obj.Addr, min, max uint32) uint32 {
 	if a.Type != obj.TYPE_REG {
@@ -1112,6 +1117,11 @@ func wantFloatReg(ctxt *obj.Link, ins *instruction, pos string, r uint32) {
 	wantReg(ctxt, ins, pos, "float", r, REG_F0, REG_F31)
 }
 
+// wantVectorReg checks that r is a vector register.
+func wantVectorReg(ctxt *obj.Link, ins *instruction, pos string, r uint32) {
+	wantReg(ctxt, ins, pos, "vector", r, REG_V0, REG_V31)
+}
+
 // wantEvenOffset checks that the offset is a multiple of two.
 func wantEvenOffset(ctxt *obj.Link, ins *instruction, offset int64) {
 	if err := immEven(offset); err != nil {