diff --git a/notes/8.md b/notes/8.md
index c82b0b1..4096325 100644
--- a/notes/8.md
+++ b/notes/8.md
@@ -49,4 +49,19 @@ But Constant folding can be dangerous on cross-compilation (in precision).
 
 ### Dead Code Elimination
 
-## Global Optimization
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+## Global Optimization
+
+It is not actually global but in control graph.
+
+In Basic Block, there are a few instructions (4-8). So only local optimization, it is not quite optimizable. There are many cases where the optimization can be performed through the entire CFG.
+
+## Dataflow Analysis
+
+* Local Dataflow Analysis
+* Global Dataflow Analysis
+
+Analysis of Reaching Definition
+
+Effect of an Instruction
+
+`IN[b]` and `OUT[b]`
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