Removed unnecessary instructions

src/build/register/RegisterNumber.go

@@ -11,7 +11,22 @@ func (f *Machine) RegisterNumber(mnemonic asm.Mnemonic, a cpu.Register, b int) {
 		f.SaveRegister(a)
 	}
 
-	if sizeof.Signed(int64(b)) == 8 {
+	// The `MOVE` operation is very flexible and works with any type of immediate number.
+	if mnemonic == asm.MOVE {
+		f.Assembler.RegisterNumber(mnemonic, a, b)
+		f.UseRegister(a)
+		f.postInstruction()
+		return
+	}
+
+	// If the number only needs 32 bits, we can encode the instruction.
+	if sizeof.Signed(int64(b)) <= 4 {
+		f.Assembler.RegisterNumber(mnemonic, a, b)
+		f.postInstruction()
+		return
+	}
+
+	// If the number needs 64 bits, we need to use a temporary register.
 	tmp := f.NewRegister()
 	f.Assembler.RegisterNumber(asm.MOVE, tmp, b)
 	f.UseRegister(tmp)
@@ -19,12 +34,4 @@ func (f *Machine) RegisterNumber(mnemonic asm.Mnemonic, a cpu.Register, b int) {
 	f.Assembler.RegisterRegister(mnemonic, a, tmp)
 	f.postInstruction()
 	f.FreeRegister(tmp)
-	} else {
-		f.Assembler.RegisterNumber(mnemonic, a, b)
-		f.postInstruction()
-	}
-
-	if mnemonic == asm.MOVE {
-		f.UseRegister(a)
-	}
 }