Improved x64 encoder

src/build/arch/x64/Store.go

@@ -7,40 +7,10 @@ import (
 )
 
 // StoreNumber stores a number into the memory address included in the given register.
-func StoreNumber(code []byte, register cpu.Register, offset byte, byteCount byte, number int) []byte {
-	if byteCount == 2 {
-		code = append(code, 0x66)
-	}
+func StoreNumber(code []byte, register cpu.Register, offset byte, numBytes byte, number int) []byte {
+	code = store(code, 0xC6, 0xC7, register, offset, numBytes, 0b000)
 
-	opCode := byte(0xC7)
-
-	if byteCount == 1 {
-		opCode = 0xC6
-	}
-
-	mod := AddressMemory
-
-	if offset != 0 || register == RBP || register == R13 {
-		mod = AddressMemoryOffset8
-	}
-
-	is64Bit := byte(0)
-
-	if byteCount == 8 {
-		is64Bit = 1
-	}
-
-	code = encode(code, is64Bit, mod, 0b000, byte(register), opCode)
-
-	if register == RSP || register == R12 {
-		code = append(code, SIB(0b00, 0b100, 0b100))
-	}
-
-	if mod == AddressMemoryOffset8 {
-		code = append(code, offset)
-	}
-
-	switch byteCount {
+	switch numBytes {
 	case 8, 4:
 		return binary.LittleEndian.AppendUint32(code, uint32(number))
 
@@ -50,3 +20,39 @@ func StoreNumber(code []byte, register cpu.Register, offset byte, byteCount byte
 
 	return append(code, byte(number))
 }
+
+// StoreRegister stores the contents of the `source` register into the memory address included in the given register.
+func StoreRegister(code []byte, register cpu.Register, offset byte, numBytes byte, source cpu.Register) []byte {
+	return store(code, 0x88, 0x89, register, offset, numBytes, source)
+}
+
+// store encodes a write to memory.
+func store(code []byte, opCode8 byte, opCode32 byte, register cpu.Register, offset byte, numBytes byte, source cpu.Register) []byte {
+	if numBytes == 2 {
+		code = append(code, 0x66)
+	}
+
+	opCode := opCode32
+
+	if numBytes == 1 {
+		opCode = opCode8
+	}
+
+	mod := AddressMemory
+
+	if offset != 0 || register == RBP || register == R13 {
+		mod = AddressMemoryOffset8
+	}
+
+	code = encode(code, mod, source, register, numBytes, opCode)
+
+	if register == RSP || register == R12 {
+		code = append(code, SIB(0b00, 0b100, 0b100))
+	}
+
+	if mod == AddressMemoryOffset8 {
+		code = append(code, offset)
+	}
+
+	return code
+}