Added generic types to sizeof

src/register/RegisterNumber.go

@@ -16,7 +16,7 @@ func (f *Machine) RegisterNumber(mnemonic asm.Mnemonic, a cpu.Register, b int) {
 	}
 
 	// If the number only needs 32 bits, we can encode the instruction.
-	if sizeof.Signed(int64(b)) <= 4 {
+	if sizeof.Signed(b) <= 4 {
 		f.Assembler.RegisterNumber(mnemonic, a, b)
 		f.postInstruction()
 		return