Fixed missing register move in if statements

src/core/CompileIf.go

@@ -9,6 +9,10 @@ import (
 
 // CompileIf compiles a branch instruction.
 func (f *Function) CompileIf(branch *ast.If) error {
+	for _, register := range f.CPU.Input {
+		f.SaveRegister(register)
+	}
+
 	f.count.branch++
 
 	var (