Backport changes in Chapter 5 to previous chapters and update Chapter5 documentation (#34)

* Backport changes from chapter 5 to older chapters (#30)

* Fix wrong indent

* Backport to chapter 4

* Backport to chapter 3

* Backport to chapter 2

* Backport to chapter 1

* Add if statement to comment (#32)

* Update visuals for chapters 1,2 & 3.
Reenable drawing of edges from constants to Start for these chapters.

* Update visuals for chapters 4.
Revise text to explain the labeling of edges in graphs and that we omit edge from Constant to Start nodes from chapter 4.

* Add code snippets for if statement parsing and the duplication and merging of ScopeNodes.
Explain how scopeNodes are duplicated and merged.

* Add constant check to minus node (#31)

* Fix closing root block with } (#33)

* Backport fix closing root block with } to chapter 4 and 3 (#35)

* Show use-def edge from Phi to Region as dotted edge.
Add example of Phi peephole.
Update visuals.
Add more examples.

* Fix visuals in chapter 1 and README in chapter 4.

* Remove subheading

* Adjust spaces

---------

Co-authored-by: XmiliaH <45106915+XmiliaH@users.noreply.github.com>

1 files changed, 15 insertions, 12 deletions

diff --git a/chapter04/README.md b/chapter04/README.md
index 2700a6a9..350b08b5 100644
--- a/chapter04/README.md
+++ b/chapter04/README.md
@@ -15,12 +15,12 @@ Here is the [complete language grammar](docs/04-grammar.md) for this chapter.
 In this chapter we add some new nodes and revise some existing nodes.
 Following are revised or new nodes
 
-| Node Name | Type             | Description                                    | Inputs                         | Value                                                                   |
-|-----------|------------------|------------------------------------------------|--------------------------------|-------------------------------------------------------------------------|
-| MultiNode | Abstract class   | A node that has a tuple result                 |                                | A tuple                                                                 |
-| Start     | Control          | Start of function, now a MultiNode             | An input argument named `arg`. | A tuple with a ctrl token and an `arg` data node                        |
-| Proj      | ?                | Projection nodes extract values from MultiNode | A MultiNode and index          | Result is the extracted value from the input MultiNode at offset index  | 
-| Bool      | Data             | Represents results of a comparison operator    | Two data nodes                 | Result a comparison, represented as integer value where 1=true, 0=false |
+| Node Name | Type           | Description                                    | Inputs                | Value                                                                      |
+|-----------|----------------|------------------------------------------------|-----------------------|----------------------------------------------------------------------------|
+| MultiNode | Abstract class | A node that has a tuple result                 |                       | A tuple                                                                    |
+| Start     | Control        | Start of function, now a MultiNode             |                       | A tuple with a ctrl token and an `arg` data node                           |
+| Proj      | ?              | Projection nodes extract values from MultiNode | A MultiNode and index | Result is the extracted value from the input MultiNode at offset index     | 
+| Bool      | Data           | Represents results of a comparison operator    | Two data nodes        | Result is a comparison, represented as integer value where 1=true, 0=false |
 
 Below is our list of Nodes from [Chapter 3](../chapter03/README.md):
 
@@ -116,13 +116,18 @@ In previous chapters, we had a hard coded control input edge from Start to
 Return. In this chapter we no longer have such a hard-wired edge.  Instead, we
 track the current in-scope control node via the name `$ctrl`.  This means that
 when we need to create an edge to the predecessor control node, we simply
-lookup this name in the current scope.
+look up this name in the current scope.
 
-This introduces the idea that the control flow subgraph is a Petri net model [[1]](#1).
+This introduces the idea that the control flow subgraph is a Petri net model.[^1]
 The control token moves virtually from node to node as execution proceeds.  The
 initial control token is in Start, it then moves via the Proj node to Return.
 In later chapters we will see how the token moves across branches.
 
+## Note Regarding Visualizations
+
+From this chapter onwards we omit the edges from Constants to Start node, mainly to reduce
+clutter and help draw reader's attention to the more important aspects of the graph.
+
 ## More Peephole Optimizations
 
 Now that we have non-constant integer values, we do additional optimizations, rearranging algebraic 
@@ -246,7 +251,5 @@ The reason this is done is that we know `m` is the new replacement and is alive,
 but since it is not yet part of the graph up the tree, it has no users yet.
 By adding a bogus user we prevent it being mistaken for dead and being killed.
 
-## References
-<a id="1">[1]</a>
-Click, C. (1995).
-Combining Analyses, Combining Optimizations, 131.
+[^1]: Click, C. (1995).
+   Combining Analyses, Combining Optimizations, 131.