diff --git a/ep18/src/main/resources/t.vm b/ep18/src/main/resources/t.vm
index 05eefb6..6d17873 100644
--- a/ep18/src/main/resources/t.vm
+++ b/ep18/src/main/resources/t.vm
@@ -2,42 +2,43 @@
     load 0
     iconst 1
     isub
-    br L2
-L2:
+    br L1
+L1:
     ret
 .def main: args=0 ,locals=1
     iconst 10
     store 0
-    br L5
-L5:
+    br L4
+L4:
     load 0
     iconst 0
     igt
-    brf L7
-L6:
+    brf L6
+L5:
     load 0
     iconst 5
     igt
-    brf L9
-L8:
+    brf L8
+L7:
     load 0
     print
     load 0
     iconst 7
     ieq
-    brf L9
-L10:
-    iconst 7
-    br L4
+    brf L10
 L9:
+    iconst 7
+    br L3
+L10:
+L8:
     sconst "break"
     print
     load 0
     call dec1()
     store 0
-    br L5
-L7:
-    iconst 0
     br L4
-L4:
+L6:
+    iconst 0
+    br L3
+L3:
     halt
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 d590d27..0caba73 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/Compiler.java
@@ -49,12 +49,12 @@ public static void main(String[] args) throws IOException {
 
         astRoot.accept(irBuilder);
 
-        var cfg = irBuilder.getCFG();
+        var cfg = irBuilder.getCFG(irBuilder.prog.blockList);
         logger.info("CFG:\n" + cfg.toString());
 
         var assembler = new CymbolAssembler();
         irBuilder.prog.accept(assembler);
-//        saveToEp18Res(assembler.getAsmInfo());
+        saveToEp18Res(assembler.getAsmInfo());
         logger.info("\n%s".formatted(assembler.getAsmInfo()));
     }
 
diff --git a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/CFGBuilder.java b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/CFGBuilder.java
index 8fdc151..8ca3a6e 100644
--- a/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/CFGBuilder.java
+++ b/ep20/src/main/java/org/teachfx/antlr4/ep20/pass/cfg/CFGBuilder.java
@@ -3,8 +3,7 @@
 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.*;
 
 public class CFGBuilder {
     private CFG<IRNode> cfg;
@@ -19,10 +18,26 @@ public CFGBuilder(List<LinearIRBlock> blockList){
         cfg = new CFG<>(basicBlocks, edges);
     }
 
+    private static final Set<String> cachedEdgeLinks = new HashSet<>();
+
     private void build(LinearIRBlock block){
+
         basicBlocks.add(BasicBlock.buildFromLinearBlock(block));
+        block.getJumpEntries().ifPresent(entries -> {
+            for(var dest : entries){
+                var key = "%d-%d".formatted(block.getOrd(), dest);
+                if (!cachedEdgeLinks.contains(key)) {
+                    edges.add(Pair.of(block.getOrd(), dest));
+                    cachedEdgeLinks.add("%d-%d".formatted(block.getOrd(), dest));
+                }
+            }
+        });
         for(var successor : block.getSuccessors()){
-            edges.add(Pair.of(block.getOrd(), successor.getOrd()));
+            var key = "%d-%d".formatted(block.getOrd(), successor.getOrd());
+            if (!cachedEdgeLinks.contains(key)) {
+                cachedEdgeLinks.add(key);
+                edges.add(Pair.of(block.getOrd(), successor.getOrd()));
+            }
             build(successor);
         }
     }
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
index e9766a9..07b198f 100644
--- 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
@@ -5,8 +5,7 @@
 import org.teachfx.antlr4.ep20.symtab.scope.Scope;
 import org.teachfx.antlr4.ep20.utils.Kind;
 
-import java.util.ArrayList;
-import java.util.List;
+import java.util.*;
 
 public class LinearIRBlock {
 
@@ -153,5 +152,27 @@ public Label getLabel() {
         return new Label(toString(),scope);
     }
 
+    public Optional<TreeSet<Integer>> getJumpEntries() {
+        var entries = new TreeSet<Integer>();
+        switch (kind) {
+            case END_BY_CJMP -> {
+                CJMP cjmp = (CJMP) getStmts().getLast();
+                var tid = cjmp.getThenBlock().getOrd();
+                var eid = cjmp.getElseBlock().getOrd();
+                entries.add(tid);
+                entries.add(eid);
+                return Optional.of(entries);
+            }
+            case END_BY_JMP -> {
+                JMP cjmp = (JMP) getStmts().getLast();
+                var tid = cjmp.next.getOrd();
+                entries.add(tid);
+                return Optional.of(entries);
+            }
+            default -> {
+                return Optional.empty();
+            }
+        }
+    }
 
 }
\ No newline at end of file
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 808df74..052f576 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
@@ -27,6 +27,7 @@
 import org.teachfx.antlr4.ep20.symtab.symbol.MethodSymbol;
 import org.teachfx.antlr4.ep20.symtab.symbol.VariableSymbol;
 
+import java.util.List;
 import java.util.Optional;
 import java.util.Stack;
 
@@ -421,12 +422,12 @@ protected VarSlot peekEvalOperand() {
         return evalExprStack.peek();
     }
 
-    public CFG<IRNode> getCFG() {
-        for (var func : prog.blockList){
+    public CFG<IRNode> getCFG(List<LinearIRBlock> blocks) {
+        for (var func : blocks){
             insertBlockLabel(func);
         }
 
-        var cfgBuilder = new CFGBuilder(prog.blockList);
+        var cfgBuilder = new CFGBuilder(blocks);
         return cfgBuilder.getCFG();
     }
 
diff --git a/ep21/README.md b/ep21/README.md
index 693485f..26cd529 100644
--- a/ep21/README.md
+++ b/ep21/README.md
@@ -21,22 +21,75 @@ graph LR
 ## DONE
 
 ```mermaid
-graph TD;
-    A[基本块1] --> B[基本块2]  
-    B --> C[基本块3]  
-    C -->|条件跳转| D[基本块6]  
-    C -->|否则| E[基本块4]  
-    E -->|条件跳转| F[基本块7]  
-    F --> B  
-    E -->|否则| G[基本块5]  
-    G -->|条件跳转| F  
-    G -->|否则| H[基本块8]  
-    H --> I[基本块9]  
-    D --> I  
-    subgraph dec1  
-    A  
-    end  
-    subgraph main  
-        B --> C --> D --> E --> F --> G --> H --> I  
-    end
+graph TD
+subgraph L0
+Q0["t0 = @0;"]
+Q1["t1 =  1 ;"]
+Q2["t0 SUB t1;"]
+Q3["jmp L1;"]
+end
+subgraph L1
+Q4["ret;"]
+end
+subgraph L2
+Q5["t0 =  10 ;"]
+Q6["@0 = t0;"]
+Q7["jmp L4;"]
+end
+subgraph L4
+Q8["t0 = @0;"]
+Q9["t1 =  0 ;"]
+Q10["t0 GT t1;"]
+Q11["jmpIf t0,L5,L6;"]
+end
+subgraph L5
+Q12["t0 = @0;"]
+Q13["t1 =  5 ;"]
+Q14["t0 GT t1;"]
+Q15["jmpIf t0,L7,L8;"]
+end
+subgraph L7
+Q16["t0 = @0;"]
+Q17["call print(args:1);"]
+Q18["t0 = @0;"]
+Q19["t1 =  7 ;"]
+Q20["t0 EQ t1;"]
+Q21["jmpIf t0,L9,L10;"]
+end
+subgraph L9
+Q22["t0 =  7 ;"]
+Q23["jmp L3;"]
+end
+subgraph L10
+end
+subgraph L8
+Q24["t0 =  'break' ;"]
+Q25["call print(args:1);"]
+Q26["t0 = @0;"]
+Q27["call dec1(args:1);"]
+Q28["@0 = t0;"]
+Q29["jmp L4;"]
+end
+subgraph L6
+Q30["t0 =  0 ;"]
+Q31["jmp L3;"]
+end
+subgraph L3
+Q32["halt;"]
+end
+
+L0 --> L1
+L2 --> L4
+L4 --> L5
+L4 --> L6
+L5 --> L7
+L5 --> L8
+L7 --> L9
+L7 --> L10
+L9 --> L3
+L9 --> L10
+L10 --> L8
+L8 --> L4
+L8 --> L6
+L6 --> L3
 ```