Add descriptions of the new node types in Chapter 5.

Add references to Cliff's thesis.

1 files changed, 29 insertions, 1 deletions

diff --git a/chapter05/README.md b/chapter05/README.md
index a5c6f52f..bea9545b 100644
--- a/chapter05/README.md
+++ b/chapter05/README.md
@@ -34,13 +34,28 @@ Following new nodes are introduced in this chapter:
 | Node Name | Type    | Chapter | Description                                                          | Inputs                                                                                         | Value                                                         |
 |-----------|---------|---------|----------------------------------------------------------------------|------------------------------------------------------------------------------------------------|---------------------------------------------------------------|
 | If        | Control | 5       | Represents an `if` condition, sub type of `MultiNode`                | A control node and a data predicate node                                                       | A tuple of two values, one for true branch, another for false |
-| Region    | Control | 5       | Represents a merge point from multiple control flow                  | An input for each control flow that is merging                                                 | None                                                          |
+| Region    | Control | 5       | Represents a merge point from multiple control flow                  | An input for each control flow that is merging                                                 | Merged control                                                |
 | Phi       | Data    | 5       | Represents the phi function that picks a value based on control flow | A region control node, and multiple data nodes that provide values from multiple control flows | Result is the extracted value depending on control flow taken | 
 | Stop      | Control | 5       | Represents termination of the program                                | One or more Return nodes                                                                       | None                                                          |
 
+## `If` Nodes
+
+`If` node takes in both control and data (predicate expression) and routes the control token to one of the two control flows, represented by the `Proj` nodes.
+
+## `Phi` Nodes
+
+The `Phi` reads in both data and control, and outputs a data value. The control input to the `Phi` points to a `Region` node. The data inputs to the `Phi` are one each for the control inputs to that `Region`.
+The result computed by a `Phi` depends both on the data and the matching control input. At most one control input to the `Region` can be active at a time. The `Phi` passes through the data value from the matching input [[1]](#1).
+
+## `Region` Nodes
+
+`Region` nodes were originally introduced to replace Basic Blocks in the IR [[3]](#3). However, we do not assign a `Region` to every node in the graph; we insert a `Region` node at a merge point where it takes control from each predecessor control edge, and produces 
+a merged control as output. Data flows via `Phi` nodes at these merge points.
+
 ## Parsing of `If` statement
 
 When we parse an `if` statement, the control flow splits at that point. We must track the names being updated in each part of the `if` statement, and then merge them at the end.
+The implementation follows the description in [[2]](#2).
 
 This involves following:
 
@@ -92,3 +107,16 @@ Below is the graph after we created a `Region` node and merged the two definitio
 * Observe that the duplicate `ScopeNode` has been discarded.
 * `a` is now bound to the `Phi` node.
 * The `Phi` node's inputs are the `Region` node and the `Add` node from the `True` branch, and `Sub` node from the `False` branch.
+
+## References
+<a id="1">[1]</a>
+Click, C. (1995).
+Combining Analyses, Combining Optimizations, 132.
+
+<a id="2">[2]</a>
+Click, C. (1995).
+Combining Analyses, Combining Optimizations, 102-103.
+
+<a id="2">[3]</a>
+Click, C. (1995).
+Combining Analyses, Combining Optimizations, 129.
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