risc-v: add support for 64-bit RISC-V CPUs

src/runtime/volatile/register.go

@@ -1,6 +1,6 @@
 package volatile
 
-// This file defines Register{8,16,32} types, which are convenience types for
+// This file defines Register{8,16,32,64} types, which are convenience types for
 // volatile register accesses.
 
 // Special types that causes loads/stores to be volatile (necessary for
@@ -190,3 +190,65 @@ func (r *Register32) HasBits(value uint32) bool {
 func (r *Register32) ReplaceBits(value uint32, mask uint32, pos uint8) {
 	StoreUint32(&r.Reg, LoadUint32(&r.Reg)&^(mask<<pos)|value<<pos)
 }
+
+type Register64 struct {
+	Reg uint64
+}
+
+// Get returns the value in the register. It is the volatile equivalent of:
+//
+//     *r.Reg
+//
+//go:inline
+func (r *Register64) Get() uint64 {
+	return LoadUint64(&r.Reg)
+}
+
+// Set updates the register value. It is the volatile equivalent of:
+//
+//     *r.Reg = value
+//
+//go:inline
+func (r *Register64) Set(value uint64) {
+	StoreUint64(&r.Reg, value)
+}
+
+// SetBits reads the register, sets the given bits, and writes it back. It is
+// the volatile equivalent of:
+//
+//     r.Reg |= value
+//
+//go:inline
+func (r *Register64) SetBits(value uint64) {
+	StoreUint64(&r.Reg, LoadUint64(&r.Reg)|value)
+}
+
+// ClearBits reads the register, clears the given bits, and writes it back. It
+// is the volatile equivalent of:
+//
+//     r.Reg &^= value
+//
+//go:inline
+func (r *Register64) ClearBits(value uint64) {
+	StoreUint64(&r.Reg, LoadUint64(&r.Reg)&^value)
+}
+
+// HasBits reads the register and then checks to see if the passed bits are set. It
+// is the volatile equivalent of:
+//
+//     (*r.Reg & value) > 0
+//
+//go:inline
+func (r *Register64) HasBits(value uint64) bool {
+	return (r.Get() & value) > 0
+}
+
+// ReplaceBits is a helper to simplify setting multiple bits high and/or low at
+// once. It is the volatile equivalent of:
+//
+//     r.Reg = (r.Reg & ^(mask << pos)) | value << pos
+//
+// go:inline
+func (r *Register64) ReplaceBits(value uint64, mask uint64, pos uint8) {
+	StoreUint64(&r.Reg, LoadUint64(&r.Reg)&^(mask<<pos)|value<<pos)
+}

src/runtime/volatile/volatile.go

@@ -24,6 +24,9 @@ func LoadUint16(addr *uint16) (val uint16)
 // LoadUint32 loads the volatile value *addr.
 func LoadUint32(addr *uint32) (val uint32)
 
+// LoadUint64 loads the volatile value *addr.
+func LoadUint64(addr *uint64) (val uint64)
+
 // StoreUint8 stores val to the volatile value *addr.
 func StoreUint8(addr *uint8, val uint8)
 
@@ -32,3 +35,6 @@ func StoreUint16(addr *uint16, val uint16)
 
 // StoreUint32 stores val to the volatile value *addr.
 func StoreUint32(addr *uint32, val uint32)
+
+// StoreUint64 stores val to the volatile value *addr.
+func StoreUint64(addr *uint64, val uint64)