diff --git a/ep20/pom.xml b/ep20/pom.xml
index ea5232e..290daff 100644
--- a/ep20/pom.xml
+++ b/ep20/pom.xml
@@ -20,12 +20,6 @@
     </properties>
     <!-- 运行测试 -->
     <dependencies>
-        <dependency>
-            <groupId>org.jgrapht</groupId>
-            <artifactId>jgrapht-core</artifactId>
-            <version>1.5.2</version>
-            <scope>compile</scope>
-        </dependency>
         <dependency>
             <groupId>org.jetbrains</groupId>
             <artifactId>annotations</artifactId>
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 001e206..dab69c9 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java
@@ -7,16 +7,12 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.teachfx.antlr4.ep20.ast.ASTNode;
-import org.teachfx.antlr4.ep20.driver.Phase;
 import org.teachfx.antlr4.ep20.ir.IRNode;
-import org.teachfx.antlr4.ep20.ir.Prog;
 import org.teachfx.antlr4.ep20.ir.stmt.Label;
 import org.teachfx.antlr4.ep20.parser.CymbolLexer;
 import org.teachfx.antlr4.ep20.parser.CymbolParser;
 import org.teachfx.antlr4.ep20.pass.ast.CymbolASTBuilder;
 //import org.teachfx.antlr4.ep20.pass.ir.CymbolIRBuilder;
-import org.teachfx.antlr4.ep20.pass.cfg.BasicBlock;
-import org.teachfx.antlr4.ep20.pass.cfg.ControlFlowAnalysis;
 import org.teachfx.antlr4.ep20.pass.codegen.CymbolAssembler;
 import org.teachfx.antlr4.ep20.pass.ir.CymbolIRBuilder;
 import org.teachfx.antlr4.ep20.pass.symtab.LocalDefine;
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/Prog.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/Prog.java
index eea0d20..db430dd 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/Prog.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/Prog.java
@@ -1,13 +1,12 @@
 package org.teachfx.antlr4.ep20.ir;
 
-import lombok.extern.log4j.Log4j2;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.teachfx.antlr4.ep20.ir.stmt.CJMP;
 import org.teachfx.antlr4.ep20.ir.stmt.FuncEntryLabel;
 import org.teachfx.antlr4.ep20.ir.stmt.JMP;
 import org.teachfx.antlr4.ep20.ir.stmt.Label;
-import org.teachfx.antlr4.ep20.pass.cfg.BasicBlock;
+import org.teachfx.antlr4.ep20.pass.cfg.LinearIRBlock;
 
 import java.util.ArrayList;
 import java.util.LinkedList;
@@ -16,7 +15,7 @@
 
 
 public class Prog extends IRNode {
-    public List<BasicBlock> blockList;
+    public List<LinearIRBlock> blockList;
     protected static Logger logger = LogManager.getLogger(Prog.class);
     public List<IRNode> instrs = new ArrayList<>();
 
@@ -30,23 +29,23 @@ public <S,E> S accept(IRVisitor<S,E> visitor){
         return visitor.visit(this);
     }
 
-    public void addBlock(BasicBlock basicBlock) {
-        blockList.add(basicBlock);
+    public void addBlock(LinearIRBlock linearIRBlock) {
+        blockList.add(linearIRBlock);
     }
 
-    private void linearInstrsImpl(BasicBlock basicBlock) {
-        if (!basicBlock.getStmts().isEmpty()) {
-            if (!basicBlock.getJmpRefMap().isEmpty()){
-                instrs.add(new Label(basicBlock.toString(),null));
+    private void linearInstrsImpl(LinearIRBlock linearIRBlock) {
+        if (!linearIRBlock.getStmts().isEmpty()) {
+            if (!linearIRBlock.getJmpRefMap().isEmpty()){
+                instrs.add(new Label(linearIRBlock.toString(),null));
             }
-            instrs.addAll(basicBlock.getStmts());
+            instrs.addAll(linearIRBlock.getStmts());
         } else {
-            if (basicBlock.getSuccessors().isEmpty()) {
+            if (linearIRBlock.getSuccessors().isEmpty()) {
                 return;
             }
 
-            var nextBlock = basicBlock.getSuccessors().get(0);
-            for (var ref : basicBlock.getJmpRefMap()){
+            var nextBlock = linearIRBlock.getSuccessors().get(0);
+            for (var ref : linearIRBlock.getJmpRefMap()){
                 if (ref instanceof JMP jmp) {
                     jmp.next = nextBlock;
                 } else if (ref instanceof CJMP cjmp) {
@@ -56,7 +55,7 @@ private void linearInstrsImpl(BasicBlock basicBlock) {
 
         }
 
-        for(var successor : basicBlock.getSuccessors()){
+        for(var successor : linearIRBlock.getSuccessors()){
             linearInstrsImpl(successor);
         }
     }
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/stmt/CJMP.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/stmt/CJMP.java
index b282597..f3ae75f 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/stmt/CJMP.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/stmt/CJMP.java
@@ -1,17 +1,17 @@
 package org.teachfx.antlr4.ep20.ir.stmt;
 
-import org.teachfx.antlr4.ep20.pass.cfg.BasicBlock;
+import org.teachfx.antlr4.ep20.pass.cfg.LinearIRBlock;
 import org.teachfx.antlr4.ep20.ir.IRVisitor;
 import org.teachfx.antlr4.ep20.ir.expr.VarSlot;
 
 public class CJMP extends Stmt {
     public VarSlot cond;
 
-    private BasicBlock thenBlock;
-    private BasicBlock elseBlock;
+    private LinearIRBlock thenBlock;
+    private LinearIRBlock elseBlock;
 
 
-    public CJMP(VarSlot cond, BasicBlock thenLabel, BasicBlock elseLabel) {
+    public CJMP(VarSlot cond, LinearIRBlock thenLabel, LinearIRBlock elseLabel) {
         this.cond = cond;
         this.thenBlock = thenLabel;
         this.elseBlock = elseLabel;
@@ -34,21 +34,21 @@ public String toString() {
         return "jmpIf %s,%s,%s".formatted(cond,thenBlock,elseBlock);
     }
 
-    public void setElseBlock(BasicBlock elseBlock) {
+    public void setElseBlock(LinearIRBlock elseBlock) {
         this.elseBlock = elseBlock;
         elseBlock.refJMP(this);
     }
 
-    public void setThenBlock(BasicBlock thenBlock) {
+    public void setThenBlock(LinearIRBlock thenBlock) {
         this.thenBlock = thenBlock;
         thenBlock.refJMP(this);
     }
 
-    public BasicBlock getElseBlock() {
+    public LinearIRBlock getElseBlock() {
         return elseBlock;
     }
 
-    public BasicBlock getThenBlock() {
+    public LinearIRBlock getThenBlock() {
         return thenBlock;
     }
 }
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/stmt/JMP.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/stmt/JMP.java
index ea89a39..839b015 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/stmt/JMP.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/ir/stmt/JMP.java
@@ -1,6 +1,6 @@
 package org.teachfx.antlr4.ep20.ir.stmt;
 
-import org.teachfx.antlr4.ep20.pass.cfg.BasicBlock;
+import org.teachfx.antlr4.ep20.pass.cfg.LinearIRBlock;
 import org.teachfx.antlr4.ep20.ir.IRVisitor;
 
 public class JMP extends Stmt
@@ -10,12 +10,12 @@ public <S, E> S accept(IRVisitor<S, E> visitor) {
         return visitor.visit(this);
     }
 
-    public JMP(BasicBlock block)
+    public JMP(LinearIRBlock block)
     {
         this.next = block;
         block.refJMP(this);
     }
-    public BasicBlock next;
+    public LinearIRBlock next;
 
     @Override
     public StmtType getStmtType() {
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 555b34b..fd7944c 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
@@ -1,140 +1,62 @@
 package org.teachfx.antlr4.ep20.pass.cfg;
 
+import org.jetbrains.annotations.NotNull;
 import org.teachfx.antlr4.ep20.ir.IRNode;
-import org.teachfx.antlr4.ep20.ir.stmt.CJMP;
-import org.teachfx.antlr4.ep20.ir.stmt.JMP;
-import org.teachfx.antlr4.ep20.ir.stmt.ReturnVal;
-import org.teachfx.antlr4.ep20.ir.stmt.Stmt;
-import org.teachfx.antlr4.ep20.symtab.scope.Scope;
+import org.teachfx.antlr4.ep20.ir.stmt.Label;
+import org.teachfx.antlr4.ep20.utils.Kind;
 
-import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
+import java.util.Optional;
 
-public class BasicBlock {
+public class BasicBlock<I extends IRNode> implements Iterable<Loc<I>> {
 
-    public enum Kind {
-        /// No jump instruction
-        CONTINUOUS,
-        /// Conditional instruction
-        END_BY_CJMP,
-        /// Unconditional jump instruction
-        END_BY_JMP,
-        /// Return instruction
-        END_BY_RETURN
-    }
-
-    public Kind kind = Kind.CONTINUOUS;
-    private static int LABEL_SEQ = 1;
-    private ArrayList<IRNode> stmts;
-
-    private List<BasicBlock> successors;
-
-    private List<BasicBlock> predecessors;
-
-    protected Scope scope = null;
-
-    private List<IRNode> jmpRefMap = new ArrayList<>();
-
-    private int ord = 0;
-
-    public BasicBlock() {
-        stmts = new ArrayList<>();
-        successors = new ArrayList<>();
-        predecessors = new ArrayList<>();
-        ord = LABEL_SEQ++;
-    }
+    // Generate codes
+    public List<Loc<I>> codes;
 
-    public void addStmt(IRNode stmt) {
-        stmts.add(stmt);
-        updateKindByLastInstr(stmt);
-    }
+    public int id;
 
-    private void updateKindByLastInstr(IRNode stmt) {
-        if (stmt instanceof CJMP) {
-            kind = Kind.END_BY_CJMP;
-        } else if (stmt instanceof JMP) {
-            kind = Kind.END_BY_JMP;
-        } else if (stmt instanceof ReturnVal) {
-            kind = Kind.END_BY_RETURN;
-        } else {
-            kind = Kind.CONTINUOUS;
-        }
-    }
-    public static boolean isBasicBlock(Stmt stmt) {
-        return !(stmt instanceof CJMP) && !(stmt instanceof JMP);
-    }
+    protected Optional<Label> label;
 
-    public List<IRNode> getStmts() {
-        return stmts;
-    }
-
-    public void setStmts(ArrayList<IRNode> stmts) {
-        this.stmts = stmts;
-        var lastInstr = stmts.get(stmts.size() - 1);
-        updateKindByLastInstr(lastInstr);
-    }
-
-    public List<BasicBlock> getSuccessors() {
-        return successors;
-    }
-
-    public void setSuccessors(List<BasicBlock> successors) {
-        this.successors = successors;
-    }
-
-    public List<BasicBlock> getPredecessors() {
-        return predecessors;
-    }
-
-    public void setPredecessors(List<BasicBlock> predecessors) {
-        this.predecessors = predecessors;
-    }
-
-    public static void setLink(BasicBlock current,BasicBlock next) {
-        current.successors.add(next);
-        next.predecessors.add(current);
-    }
-
-    public void setLink(BasicBlock next) {
-        BasicBlock.setLink(this,next);
-    }
-
-    public Scope getScope() {
-        return scope;
-    }
-
-    public void setScope(Scope scope) {
-        this.scope = scope;
-    }
+    public Kind kind;
 
+    @NotNull
     @Override
-    public String toString() {
-        return "L"+ord;
+    public Iterator<Loc<I>> iterator() {
+        return codes.iterator();
     }
+    public Iterator<Loc<I>> backwardIterator() {
+        return new Iterator<Loc<I>>() {
+            private int index = codes.size() - 1;
+            @Override
+            public boolean hasNext() {
+                return index != -1;
+            }
 
-    public List<IRNode> getJmpRefMap() {
-        return jmpRefMap;
+            @Override
+            public Loc<I> next() {
+                var loc = codes.get(index);
+                index--;
+                return loc;
+            }
+        };
     }
 
-    public void setJmpRefMap(List<IRNode> jmpRefMap) {
-        this.jmpRefMap = jmpRefMap;
+    public BasicBlock(Kind kind, int id, List<Loc<I>> codes, Optional<Label> label) {
+        this.codes = codes;
+        this.label = label;
+        this.id = id;
+        this.kind = kind;
     }
 
-    public int getOrd() {
-        return ord;
+    public int getId() {
+        return id;
     }
 
-
-    public void refJMP(IRNode node) {
-        jmpRefMap.add(node);
+    // Generate isEmpty
+    public boolean isEmpty() {
+        return codes.isEmpty();
     }
 
-    @Override
-    public boolean equals(Object obj) {
-        return toString().equalsIgnoreCase(obj.toString());
-    }
 
-    public IRNode getLastInstr() {
-        return stmts.get(stmts.size() - 1);
-    }
-}
+}
\ No newline at end of file
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/CFG.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/CFG.java
index 7b814a2..b276dd0 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/CFG.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/CFG.java
@@ -1,4 +1,36 @@
 package org.teachfx.antlr4.ep20.pass.cfg;
+
+import org.apache.commons.lang3.tuple.Pair;
+import org.teachfx.antlr4.ep20.ir.IRNode;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+import java.util.TreeSet;
+
 public class CFG {
+    public final List<IRNode> nodes;
+
+    public final List<Pair<Integer,Integer>> edges;
+
+    private List<Pair<Set<Integer>, Set<Integer>>> links;
+
+    public CFG(List<IRNode> nodes, List<Pair<Integer, Integer>> edges) {
+        // Generate init
+        this.nodes = nodes;
+        this.edges = edges;
+
+        links = new ArrayList<>();
+        for (var i = 0;i < nodes.size();i++) {
+            links.add(Pair.of(new TreeSet<>(), new TreeSet<>()));
+        }
+
+        for (var edge : edges) {
+             var u = edge.getLeft();
+             var v = edge.getRight();
+             links.get(u).getRight().add(v);
+             links.get(v).getLeft().add(u);
 
+        }
+    }
 }
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/LinearIRBlock.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/LinearIRBlock.java
new file mode 100644
index 0000000..4a035c6
--- /dev/null
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/LinearIRBlock.java
@@ -0,0 +1,130 @@
+package org.teachfx.antlr4.ep20.pass.cfg;
+
+import org.teachfx.antlr4.ep20.ir.IRNode;
+import org.teachfx.antlr4.ep20.ir.stmt.CJMP;
+import org.teachfx.antlr4.ep20.ir.stmt.JMP;
+import org.teachfx.antlr4.ep20.ir.stmt.ReturnVal;
+import org.teachfx.antlr4.ep20.ir.stmt.Stmt;
+import org.teachfx.antlr4.ep20.symtab.scope.Scope;
+import org.teachfx.antlr4.ep20.utils.Kind;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class LinearIRBlock {
+
+    public Kind kind = Kind.CONTINUOUS;
+    private static int LABEL_SEQ = 1;
+    private ArrayList<IRNode> stmts;
+
+    private List<LinearIRBlock> successors;
+
+    private List<LinearIRBlock> predecessors;
+
+    protected Scope scope = null;
+
+    private List<IRNode> jmpRefMap = new ArrayList<>();
+
+    private int ord = 0;
+
+    public LinearIRBlock() {
+        stmts = new ArrayList<>();
+        successors = new ArrayList<>();
+        predecessors = new ArrayList<>();
+        ord = LABEL_SEQ++;
+    }
+
+    public void addStmt(IRNode stmt) {
+        stmts.add(stmt);
+        updateKindByLastInstr(stmt);
+    }
+
+    private void updateKindByLastInstr(IRNode stmt) {
+        if (stmt instanceof CJMP) {
+            kind = Kind.END_BY_CJMP;
+        } else if (stmt instanceof JMP) {
+            kind = Kind.END_BY_JMP;
+        } else if (stmt instanceof ReturnVal) {
+            kind = Kind.END_BY_RETURN;
+        } else {
+            kind = Kind.CONTINUOUS;
+        }
+    }
+    public static boolean isBasicBlock(Stmt stmt) {
+        return !(stmt instanceof CJMP) && !(stmt instanceof JMP);
+    }
+
+    public List<IRNode> getStmts() {
+        return stmts;
+    }
+
+    public void setStmts(ArrayList<IRNode> stmts) {
+        this.stmts = stmts;
+        var lastInstr = stmts.get(stmts.size() - 1);
+        updateKindByLastInstr(lastInstr);
+    }
+
+    public List<LinearIRBlock> getSuccessors() {
+        return successors;
+    }
+
+    public void setSuccessors(List<LinearIRBlock> successors) {
+        this.successors = successors;
+    }
+
+    public List<LinearIRBlock> getPredecessors() {
+        return predecessors;
+    }
+
+    public void setPredecessors(List<LinearIRBlock> predecessors) {
+        this.predecessors = predecessors;
+    }
+
+    public static void setLink(LinearIRBlock current, LinearIRBlock next) {
+        current.successors.add(next);
+        next.predecessors.add(current);
+    }
+
+    public void setLink(LinearIRBlock next) {
+        LinearIRBlock.setLink(this,next);
+    }
+
+    public Scope getScope() {
+        return scope;
+    }
+
+    public void setScope(Scope scope) {
+        this.scope = scope;
+    }
+
+    @Override
+    public String toString() {
+        return "L"+ord;
+    }
+
+    public List<IRNode> getJmpRefMap() {
+        return jmpRefMap;
+    }
+
+    public void setJmpRefMap(List<IRNode> jmpRefMap) {
+        this.jmpRefMap = jmpRefMap;
+    }
+
+    public int getOrd() {
+        return ord;
+    }
+
+
+    public void refJMP(IRNode node) {
+        jmpRefMap.add(node);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        return toString().equalsIgnoreCase(obj.toString());
+    }
+
+    public IRNode getLastInstr() {
+        return stmts.get(stmts.size() - 1);
+    }
+}
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/Loc.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/Loc.java
new file mode 100644
index 0000000..be54d21
--- /dev/null
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/Loc.java
@@ -0,0 +1,18 @@
+package org.teachfx.antlr4.ep20.pass.cfg;
+
+import org.teachfx.antlr4.ep20.ir.IRNode;
+import org.teachfx.antlr4.ep20.ir.expr.Operand;
+
+import java.util.Set;
+
+public class Loc <I extends IRNode> {
+    // arrange properties
+    public final I instr;
+    public Loc(I instr) {
+        this.instr = instr;
+    }
+
+    public Set<Operand> liveIn;
+
+    public Set<Operand> liveOut;
+}
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/ir/CymbolIRBuilder.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/ir/CymbolIRBuilder.java
index 89f3684..483a05e 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/ir/CymbolIRBuilder.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/ir/CymbolIRBuilder.java
@@ -11,7 +11,7 @@
 import org.teachfx.antlr4.ep20.ast.stmt.*;
 import org.teachfx.antlr4.ep20.ast.type.TypeNode;
 import org.teachfx.antlr4.ep20.ir.expr.Operand;
-import org.teachfx.antlr4.ep20.pass.cfg.BasicBlock;
+import org.teachfx.antlr4.ep20.pass.cfg.LinearIRBlock;
 import org.teachfx.antlr4.ep20.ir.IRNode;
 import org.teachfx.antlr4.ep20.ir.Prog;
 import org.teachfx.antlr4.ep20.ir.expr.CallFunc;
@@ -33,10 +33,10 @@ public class CymbolIRBuilder implements ASTVisitor<Void, VarSlot> {
     private static final Logger logger = LogManager.getLogger(CymbolIRBuilder.class);
     public Prog prog = null;
 
-    private BasicBlock currentBlock = null;
-    private BasicBlock exitBlock = null;
-    private Stack<BasicBlock> breakStack;
-    private Stack<BasicBlock> continueStack;
+    private LinearIRBlock currentBlock = null;
+    private LinearIRBlock exitBlock = null;
+    private Stack<LinearIRBlock> breakStack;
+    private Stack<LinearIRBlock> continueStack;
     private Stack<VarSlot> evalExprStack;
 
     private ASTNode curNode = null;
@@ -77,7 +77,7 @@ public Void visit(FuncDeclNode funcDeclNode) {
         evalExprStack = new Stack<>();
         getCurrentBlock().addStmt(entryLabel);
 
-        var exitBlock = new BasicBlock();
+        var exitBlock = new LinearIRBlock();
         var exitEntry = new ReturnVal(null,methodSymbol);
 
         setExitHook(exitEntry,methodSymbol);
@@ -224,9 +224,9 @@ public Void visit(ReturnStmtNode returnStmtNode) {
     @Override
     public Void visit(WhileStmtNode whileStmtNode) {
         curNode = whileStmtNode;
-        var condBlock = new BasicBlock();
-        var doBlock = new BasicBlock();
-        var endBlock = new BasicBlock();
+        var condBlock = new LinearIRBlock();
+        var doBlock = new LinearIRBlock();
+        var endBlock = new LinearIRBlock();
 
         jump(condBlock);
 
@@ -257,15 +257,15 @@ public Void visit(IfStmtNode ifStmtNode) {
 
         ifStmtNode.getCondExpr().accept(this);
         var cond = peekEvalOperand();
-        var thenBlock = new BasicBlock();
-        var endBlock = new BasicBlock();
+        var thenBlock = new LinearIRBlock();
+        var endBlock = new LinearIRBlock();
 
         if (ifStmtNode.getElseBlock().isEmpty()) {
             jumpIf(cond,thenBlock,endBlock);
             setCurrentBlock(thenBlock);
             ifStmtNode.getThenBlock().accept(this);
         }else {
-            var elseBlock = new BasicBlock();
+            var elseBlock = new LinearIRBlock();
             jumpIf(cond,thenBlock,elseBlock);
             setCurrentBlock(thenBlock);
             ifStmtNode.getThenBlock().accept(this);
@@ -306,7 +306,7 @@ public Void visit(ContinueStmtNode continueStmtNode) {
     }
 
     public void forkNewBlock() {
-        currentBlock = new BasicBlock();
+        currentBlock = new LinearIRBlock();
         breakStack = new Stack<>();
         continueStack = new Stack<>();
     }
@@ -314,11 +314,11 @@ public void clearBlock() {
         currentBlock = null;
     }
 
-    protected BasicBlock getCurrentBlock() {
+    protected LinearIRBlock getCurrentBlock() {
         return currentBlock;
     }
 
-    public void setCurrentBlock(BasicBlock nextBlock) {
+    public void setCurrentBlock(LinearIRBlock nextBlock) {
         currentBlock.setLink(nextBlock);
         currentBlock = nextBlock;
     }
@@ -358,14 +358,14 @@ protected void setExitHook(ReturnVal returnVal,MethodSymbol methodSymbol) {
         }
     }
 
-    public void jump(BasicBlock block) {
+    public void jump(LinearIRBlock block) {
         addInstr(new JMP(block));
     }
-    public void jumpIf(VarSlot cond,BasicBlock thenBlock,BasicBlock elseBlock) {
+    public void jumpIf(VarSlot cond, LinearIRBlock thenBlock, LinearIRBlock elseBlock) {
         addInstr(new CJMP(cond,thenBlock,elseBlock));
     }
-    public void pushBreakStack(BasicBlock basicBlock) {
-        breakStack.push(basicBlock);
+    public void pushBreakStack(LinearIRBlock linearIRBlock) {
+        breakStack.push(linearIRBlock);
     }
 
     public void popBreakStack() {
@@ -373,8 +373,8 @@ public void popBreakStack() {
     }
 
 
-    public void pushContinueStack(BasicBlock basicBlock) {
-        continueStack.push(basicBlock);
+    public void pushContinueStack(LinearIRBlock linearIRBlock) {
+        continueStack.push(linearIRBlock);
     }
 
 
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/utils/Kind.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/utils/Kind.java
new file mode 100644
index 0000000..af02c7b
--- /dev/null
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/utils/Kind.java
@@ -0,0 +1,12 @@
+package org.teachfx.antlr4.ep20.utils;
+
+public enum Kind {
+    /// No jump instruction
+    CONTINUOUS,
+    /// Conditional instruction
+    END_BY_CJMP,
+    /// Unconditional jump instruction
+    END_BY_JMP,
+    /// Return instruction
+    END_BY_RETURN
+}
diff --git a/pom.xml b/pom.xml
index 6584ee4..3e87f4d 100644
--- a/pom.xml
+++ b/pom.xml
@@ -24,6 +24,11 @@
 
     <!-- 添加依赖项 -->
     <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>3.12.0</version>
+        </dependency>
         <!-- Log4j2核心库 -->
         <dependency>
             <groupId>org.apache.logging.log4j</groupId>