diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java
index 6d76854..e111f4c 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java
@@ -31,7 +31,7 @@ protected static void printIRTree(List<IRNode> irNodeList) {
             }
             return "    "+irNode.toString();
         }).reduce((a, b) -> a + "\n" + b);
-        logger.info("IR Tree:" + "\n"+prettyFormatText.get());
+        prettyFormatText.ifPresent(logger::debug);
     }
 
     public static void main(String[] args) throws IOException {
@@ -70,7 +70,7 @@ public static void main(String[] args) throws IOException {
         var assembler = new CymbolAssembler();
         assembler.visit(codeBuffer);
         saveToEp18Res(assembler.getAsmInfo());
-        logger.info("\n%s".formatted(assembler.getAsmInfo()));
+        logger.debug("\n%s".formatted(assembler.getAsmInfo()));
     }
 
     protected static void saveToEp18Res(String buffer) {
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/expr/arith/BinExpr.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/expr/arith/BinExpr.java
index cbe2859..da0e494 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/expr/arith/BinExpr.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/expr/arith/BinExpr.java
@@ -2,6 +2,7 @@
 
 import org.teachfx.antlr4.ep20.ir.IRVisitor;
 import org.teachfx.antlr4.ep20.ir.expr.Expr;
+import org.teachfx.antlr4.ep20.ir.expr.Operand;
 import org.teachfx.antlr4.ep20.ir.expr.VarSlot;
 import org.teachfx.antlr4.ep20.symtab.type.OperatorType;
 
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/BasicBlock.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/BasicBlock.java
index fe034a7..87d3a10 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/BasicBlock.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/BasicBlock.java
@@ -21,11 +21,13 @@ public class BasicBlock<I extends IRNode> implements Comparable<BasicBlock<I>>,
     // Generate codes
     public List<Loc<I>> codes;
     public Kind kind;
+
     // For data flow analysis
     public Set<Operand> def;
     public Set<Operand> liveUse;
     public Set<Operand> liveIn;
     public Set<Operand> liveOut;
+
     protected Label label;
 
     public BasicBlock(Kind kind, List<Loc<I>> codes,Label label,int ord) {