# Control Flow Analysis

Dominator

for a given CFG **a node `x` dominates a node `y`** if every path from the Entry block to `y` contains `x`.

* Each BB dominates itself
* If `x dom y` and `y dom z` then `x dom z`
* If `x dom z` and `y dom z` then either `x dom y` or `y dom x`

Dominator Tree
* initial node is a root
* `x dom y` means that "`y` is a child of `x`"


Natural Loops

How to Find Natural Loop?: Introduction Backedge

Important concepts in a loop
* Header and Loop BB
* Back Edges
* Exit Edges
* Preheader (Preloop)

Loop-Invariant Computation