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-rw-r--r--docs/chapter09/09-grammar.md98
-rw-r--r--docs/chapter09/09-graph1.gv67
-rw-r--r--docs/chapter09/09-graph1.svg222
-rw-r--r--docs/chapter09/09-graph2.gv63
-rw-r--r--docs/chapter09/09-graph2.svg196
-rw-r--r--docs/chapter09/09-graph3.gv37
-rw-r--r--docs/chapter09/09-graph3.svg109
-rw-r--r--docs/chapter09/09-graph4.gv29
-rw-r--r--docs/chapter09/09-graph4.svg67
-rw-r--r--docs/chapter09/09-graph5.gv63
-rw-r--r--docs/chapter09/09-graph5.svg210
-rw-r--r--docs/chapter09/09-graph6.gv60
-rw-r--r--docs/chapter09/09-graph6.svg184
-rw-r--r--docs/chapter09/Makefile12
-rw-r--r--docs/chapter09/README.md275
15 files changed, 1692 insertions, 0 deletions
diff --git a/docs/chapter09/09-grammar.md b/docs/chapter09/09-grammar.md
new file mode 100644
index 00000000..4c61bfd7
--- /dev/null
+++ b/docs/chapter09/09-grammar.md
@@ -0,0 +1,98 @@
+# Grammar for Chapter 8
+
+```antlrv4
+grammar SimpleLanguage;
+
+program
+ : statement+ EOF
+ ;
+
+statement
+ : returnStatement
+ | declStatement
+ | blockStatment
+ | expressionStatement
+ | ifStatement
+ | whileStatement
+ | breakStatement
+ | continueStatment
+ | metaStatement
+ ;
+
+whileStatement
+ : 'while' '(' expression ')' statement
+ ;
+
+breakStatement
+ : 'break' ';'
+ ;
+
+continueStatement
+ : 'continue' ';'
+ ;
+
+ifStatement
+ : 'if' '(' expression ')' statement ('else' statement)?
+ ;
+
+metaStatement
+ : '#showGraph' ';'
+ ;
+
+expressionStatement
+ : IDENTIFIER '=' expression ';'
+ ;
+
+blockStatement
+ : '{' statement+ '}'
+ ;
+
+declStatement
+ : 'int' IDENTIFIER '=' expression ';'
+ ;
+
+returnStatement
+ : 'return' expression ';'
+ ;
+
+expression
+ : comparisonExpression
+ ;
+
+comparisonExpression
+ : additiveExpression (('==' | '!='| '>'| '<'| '>='| '<=') additiveExpression)*
+ ;
+
+additiveExpression
+ : multiplicativeExpression (('+' | '-') multiplicativeExpression)*
+ ;
+
+multiplicativeExpression
+ : unaryExpression (('*' | '/') unaryExpression)*
+ ;
+
+unaryExpression
+ : ('-') unaryExpression
+ | primaryExpression
+ ;
+
+primaryExpression
+ : IDENTIFIER
+ | INTEGER_LITERAL
+ | 'true'
+ | 'false'
+ | '(' expression ')'
+ ;
+
+INTEGER_LITERAL
+ : [1-9][0-9]*
+ | [0]
+ ;
+
+IDENTIFIER
+ : NON_DIGIT (NON_DIGIT | DIGIT)*
+ ;
+
+NON_DIGIT: [a-zA-Z_];
+DEC_DIGIT: [0-9];
+```
diff --git a/docs/chapter09/09-graph1.gv b/docs/chapter09/09-graph1.gv
new file mode 100644
index 00000000..e6d1851a
--- /dev/null
+++ b/docs/chapter09/09-graph1.gv
@@ -0,0 +1,67 @@
+digraph chapter08 {
+/*
+int x = arg + arg;
+if(arg < 10) {
+ return arg + arg;
+}
+else {
+ x = x + 1;
+}
+return x;
+
+*/
+ rankdir=BT;
+ ordering="in";
+ concentrate="true";
+ compound="true";
+ subgraph cluster_Nodes {
+ Start2 [ shape=plaintext label=<
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
+ <TR><TD BGCOLOR="yellow">Start</TD></TR>
+ <TR><TD>
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+ <TR><TD PORT="p0" BGCOLOR="yellow">$ctrl</TD><TD PORT="p1">arg</TD></TR>
+ </TABLE>
+ </TD></TR>
+ </TABLE>>
+ ];
+ Stop3 [ shape=box style=filled fillcolor=yellow label="Stop" ];
+ Con_7 [ label="2" ];
+ Mul8 [ label="*" ];
+ Con_9 [ label="10" ];
+ LT10 [ label="<" ];
+ If11 [ shape=plaintext label=<
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
+ <TR><TD BGCOLOR="yellow">If</TD></TR>
+ <TR><TD>
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+ <TR><TD PORT="p0" BGCOLOR="yellow">True</TD><TD PORT="p1" BGCOLOR="yellow">False</TD></TR>
+ </TABLE>
+ </TD></TR>
+ </TABLE>>
+ ];
+ Con_16 [ label="2" ];
+ Mul17 [ label="*" ];
+ Return18 [ shape=box style=filled fillcolor=yellow label="Return" ];
+ Con_20 [ label="1" ];
+ Add21 [ label="+" ];
+ Return24 [ shape=box style=filled fillcolor=yellow label="Return" ];
+ }
+ edge [ fontname=Helvetica, fontsize=8 ];
+ Stop3 -> Return18[taillabel=0 color=red];
+ Stop3 -> Return24[taillabel=1 color=red];
+ Mul8 -> Start2:p1[taillabel=1];
+ Mul8 -> Con_7[taillabel=2];
+ LT10 -> Start2:p1[taillabel=1];
+ LT10 -> Con_9[taillabel=2];
+ If11 -> Start2:p0[taillabel=0 color=red];
+ If11 -> LT10[taillabel=1];
+ Mul17 -> Start2:p1[taillabel=1];
+ Mul17 -> Con_16[taillabel=2];
+ Return18 -> If11:p0[taillabel=0 color=red];
+ Return18 -> Mul17[taillabel=1];
+ Add21 -> Mul8[taillabel=1];
+ Add21 -> Con_20[taillabel=2];
+ Return24 -> If11:p1[taillabel=0 color=red];
+ Return24 -> Add21[taillabel=1];
+}
diff --git a/docs/chapter09/09-graph1.svg b/docs/chapter09/09-graph1.svg
new file mode 100644
index 00000000..fce8d53c
--- /dev/null
+++ b/docs/chapter09/09-graph1.svg
@@ -0,0 +1,222 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
+ "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<!-- Generated by graphviz version 2.43.0 (0)
+ -->
+<!-- Title: chapter08 Pages: 1 -->
+<svg width="350pt" height="420pt"
+ viewBox="0.00 0.00 350.00 420.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+<g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 416)">
+<title>chapter08</title>
+<polygon fill="white" stroke="transparent" points="-4,4 -4,-416 346,-416 346,4 -4,4"/>
+<g id="clust1" class="cluster">
+<title>cluster_Nodes</title>
+<polygon fill="none" stroke="black" points="8,-8 8,-404 334,-404 334,-8 8,-8"/>
+</g>
+<!-- Start2 -->
+<g id="node1" class="node">
+<title>Start2</title>
+<polygon fill="yellow" stroke="transparent" points="56,-367 56,-392 137,-392 137,-367 56,-367"/>
+<polygon fill="none" stroke="black" points="56,-367 56,-392 137,-392 137,-367 56,-367"/>
+<text text-anchor="start" x="78" y="-375.8" font-family="Times,serif" font-size="14.00">Start</text>
+<polygon fill="none" stroke="black" points="56,-336 56,-367 137,-367 137,-336 56,-336"/>
+<polygon fill="yellow" stroke="transparent" points="61,-341 61,-362 101,-362 101,-341 61,-341"/>
+<polygon fill="none" stroke="black" points="61,-341 61,-362 101,-362 101,-341 61,-341"/>
+<text text-anchor="start" x="64" y="-347.8" font-family="Times,serif" font-size="14.00">$ctrl</text>
+<polygon fill="none" stroke="black" points="101,-341 101,-362 132,-362 132,-341 101,-341"/>
+<text text-anchor="start" x="104" y="-347.8" font-family="Times,serif" font-size="14.00">arg</text>
+</g>
+<!-- Stop3 -->
+<g id="node2" class="node">
+<title>Stop3</title>
+<polygon fill="yellow" stroke="black" points="175,-52 121,-52 121,-16 175,-16 175,-52"/>
+<text text-anchor="middle" x="148" y="-30.3" font-family="Times,serif" font-size="14.00">Stop</text>
+</g>
+<!-- Return18 -->
+<g id="node10" class="node">
+<title>Return18</title>
+<polygon fill="yellow" stroke="black" points="139,-124 73,-124 73,-88 139,-88 139,-124"/>
+<text text-anchor="middle" x="106" y="-102.3" font-family="Times,serif" font-size="14.00">Return</text>
+</g>
+<!-- Stop3&#45;&gt;Return18 -->
+<g id="edge1" class="edge">
+<title>Stop3&#45;&gt;Return18</title>
+<path fill="none" stroke="red" d="M137.62,-52.3C132.74,-60.44 126.81,-70.31 121.42,-79.3"/>
+<polygon fill="red" stroke="red" points="118.41,-77.52 116.26,-87.9 124.41,-81.12 118.41,-77.52"/>
+<text text-anchor="middle" x="134.62" y="-54.9" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- Return24 -->
+<g id="node13" class="node">
+<title>Return24</title>
+<polygon fill="yellow" stroke="black" points="223,-124 157,-124 157,-88 223,-88 223,-124"/>
+<text text-anchor="middle" x="190" y="-102.3" font-family="Times,serif" font-size="14.00">Return</text>
+</g>
+<!-- Stop3&#45;&gt;Return24 -->
+<g id="edge2" class="edge">
+<title>Stop3&#45;&gt;Return24</title>
+<path fill="none" stroke="red" d="M158.38,-52.3C163.26,-60.44 169.19,-70.31 174.58,-79.3"/>
+<polygon fill="red" stroke="red" points="171.59,-81.12 179.74,-87.9 177.59,-77.52 171.59,-81.12"/>
+<text text-anchor="middle" x="155.38" y="-54.9" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Con_7 -->
+<g id="node3" class="node">
+<title>Con_7</title>
+<ellipse fill="none" stroke="black" cx="262" cy="-364" rx="27" ry="18"/>
+<text text-anchor="middle" x="262" y="-360.3" font-family="Times,serif" font-size="14.00">2</text>
+</g>
+<!-- Mul8 -->
+<g id="node4" class="node">
+<title>Mul8</title>
+<ellipse fill="none" stroke="black" cx="227" cy="-278" rx="27" ry="18"/>
+<text text-anchor="middle" x="227" y="-274.3" font-family="Times,serif" font-size="14.00">*</text>
+</g>
+<!-- Mul8&#45;&gt;Start2 -->
+<g id="edge3" class="edge">
+<title>Mul8&#45;&gt;Start2:p1</title>
+<path fill="none" stroke="black" d="M208.6,-291.54C193.58,-301.96 172,-317.39 154,-332 147.74,-337.08 146.05,-343.45 142.33,-347.37"/>
+<polygon fill="black" stroke="black" points="141.05,-344.11 133,-351 143.59,-350.64 141.05,-344.11"/>
+<text text-anchor="middle" x="205.6" y="-294.14" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Mul8&#45;&gt;Con_7 -->
+<g id="edge4" class="edge">
+<title>Mul8&#45;&gt;Con_7</title>
+<path fill="none" stroke="black" d="M233.91,-295.6C238.85,-307.45 245.59,-323.62 251.23,-337.15"/>
+<polygon fill="black" stroke="black" points="248.02,-338.55 255.1,-346.44 254.48,-335.86 248.02,-338.55"/>
+<text text-anchor="middle" x="230.91" y="-298.2" font-family="Helvetica,sans-Serif" font-size="8.00">2</text>
+</g>
+<!-- Con_9 -->
+<g id="node5" class="node">
+<title>Con_9</title>
+<ellipse fill="none" stroke="black" cx="190" cy="-364" rx="27" ry="18"/>
+<text text-anchor="middle" x="190" y="-360.3" font-family="Times,serif" font-size="14.00">10</text>
+</g>
+<!-- LT10 -->
+<g id="node6" class="node">
+<title>LT10</title>
+<ellipse fill="none" stroke="black" cx="155" cy="-278" rx="27" ry="18"/>
+<text text-anchor="middle" x="155" y="-274.3" font-family="Times,serif" font-size="14.00">&lt;</text>
+</g>
+<!-- LT10&#45;&gt;Start2 -->
+<g id="edge5" class="edge">
+<title>LT10&#45;&gt;Start2:p1</title>
+<path fill="none" stroke="black" d="M139.98,-293.02C131.35,-302.35 121.57,-315.51 118.21,-329.88"/>
+<polygon fill="black" stroke="black" points="114.71,-329.65 117,-340 121.66,-330.49 114.71,-329.65"/>
+<text text-anchor="middle" x="136.98" y="-295.62" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- LT10&#45;&gt;Con_9 -->
+<g id="edge6" class="edge">
+<title>LT10&#45;&gt;Con_9</title>
+<path fill="none" stroke="black" d="M161.91,-295.6C166.85,-307.45 173.59,-323.62 179.23,-337.15"/>
+<polygon fill="black" stroke="black" points="176.02,-338.55 183.1,-346.44 182.48,-335.86 176.02,-338.55"/>
+<text text-anchor="middle" x="158.91" y="-298.2" font-family="Helvetica,sans-Serif" font-size="8.00">2</text>
+</g>
+<!-- If11 -->
+<g id="node7" class="node">
+<title>If11</title>
+<polygon fill="yellow" stroke="transparent" points="102,-195 102,-220 196,-220 196,-195 102,-195"/>
+<polygon fill="none" stroke="black" points="102,-195 102,-220 196,-220 196,-195 102,-195"/>
+<text text-anchor="start" x="143.5" y="-203.8" font-family="Times,serif" font-size="14.00">If</text>
+<polygon fill="none" stroke="black" points="102,-164 102,-195 196,-195 196,-164 102,-164"/>
+<polygon fill="yellow" stroke="transparent" points="107,-169 107,-190 147,-190 147,-169 107,-169"/>
+<polygon fill="none" stroke="black" points="107,-169 107,-190 147,-190 147,-169 107,-169"/>
+<text text-anchor="start" x="110" y="-175.8" font-family="Times,serif" font-size="14.00">True</text>
+<polygon fill="yellow" stroke="transparent" points="147,-169 147,-190 191,-190 191,-169 147,-169"/>
+<polygon fill="none" stroke="black" points="147,-169 147,-190 191,-190 191,-169 147,-169"/>
+<text text-anchor="start" x="150" y="-175.8" font-family="Times,serif" font-size="14.00">False</text>
+</g>
+<!-- If11&#45;&gt;Start2 -->
+<g id="edge7" class="edge">
+<title>If11&#45;&gt;Start2:p0</title>
+<path fill="none" stroke="red" d="M133.74,-224.23C117.53,-257.6 93.05,-308.62 84.28,-330.23"/>
+<polygon fill="red" stroke="red" points="80.86,-329.41 81,-340 87.5,-331.63 80.86,-329.41"/>
+<text text-anchor="middle" x="130.74" y="-226.83" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- If11&#45;&gt;LT10 -->
+<g id="edge8" class="edge">
+<title>If11&#45;&gt;LT10</title>
+<path fill="none" stroke="black" d="M151.23,-224.28C151.83,-232.58 152.46,-241.48 153.04,-249.56"/>
+<polygon fill="black" stroke="black" points="149.55,-249.87 153.76,-259.6 156.54,-249.37 149.55,-249.87"/>
+<text text-anchor="middle" x="148.23" y="-226.88" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Con_16 -->
+<g id="node8" class="node">
+<title>Con_16</title>
+<ellipse fill="none" stroke="black" cx="43" cy="-278" rx="27" ry="18"/>
+<text text-anchor="middle" x="43" y="-274.3" font-family="Times,serif" font-size="14.00">2</text>
+</g>
+<!-- Mul17 -->
+<g id="node9" class="node">
+<title>Mul17</title>
+<ellipse fill="none" stroke="black" cx="49" cy="-192" rx="27" ry="18"/>
+<text text-anchor="middle" x="49" y="-188.3" font-family="Times,serif" font-size="14.00">*</text>
+</g>
+<!-- Mul17&#45;&gt;Start2 -->
+<g id="edge9" class="edge">
+<title>Mul17&#45;&gt;Start2:p1</title>
+<path fill="none" stroke="black" d="M58.46,-208.9C75.17,-237.54 108.83,-297.79 115.74,-329.91"/>
+<polygon fill="black" stroke="black" points="112.29,-330.51 117,-340 119.24,-329.64 112.29,-330.51"/>
+<text text-anchor="middle" x="55.46" y="-211.5" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Mul17&#45;&gt;Con_16 -->
+<g id="edge10" class="edge">
+<title>Mul17&#45;&gt;Con_16</title>
+<path fill="none" stroke="black" d="M47.79,-210C46.98,-221.31 45.9,-236.42 44.97,-249.43"/>
+<polygon fill="black" stroke="black" points="41.45,-249.51 44.23,-259.74 48.44,-250.01 41.45,-249.51"/>
+<text text-anchor="middle" x="44.79" y="-212.6" font-family="Helvetica,sans-Serif" font-size="8.00">2</text>
+</g>
+<!-- Return18&#45;&gt;If11 -->
+<g id="edge11" class="edge">
+<title>Return18&#45;&gt;If11:p0</title>
+<path fill="none" stroke="red" d="M115.27,-124.08C119.67,-133.41 124.35,-145.54 126.19,-157.76"/>
+<polygon fill="red" stroke="red" points="122.72,-158.31 127,-168 129.7,-157.76 122.72,-158.31"/>
+<text text-anchor="middle" x="112.27" y="-126.68" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- Return18&#45;&gt;Mul17 -->
+<g id="edge12" class="edge">
+<title>Return18&#45;&gt;Mul17</title>
+<path fill="none" stroke="black" d="M94.19,-124.4C85.84,-136.7 74.55,-153.35 65.34,-166.92"/>
+<polygon fill="black" stroke="black" points="62.36,-165.08 59.64,-175.32 68.15,-169.01 62.36,-165.08"/>
+<text text-anchor="middle" x="91.19" y="-127" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Con_20 -->
+<g id="node11" class="node">
+<title>Con_20</title>
+<ellipse fill="none" stroke="black" cx="299" cy="-278" rx="27" ry="18"/>
+<text text-anchor="middle" x="299" y="-274.3" font-family="Times,serif" font-size="14.00">1</text>
+</g>
+<!-- Add21 -->
+<g id="node12" class="node">
+<title>Add21</title>
+<ellipse fill="none" stroke="black" cx="249" cy="-192" rx="27" ry="18"/>
+<text text-anchor="middle" x="249" y="-188.3" font-family="Times,serif" font-size="14.00">+</text>
+</g>
+<!-- Add21&#45;&gt;Mul8 -->
+<g id="edge13" class="edge">
+<title>Add21&#45;&gt;Mul8</title>
+<path fill="none" stroke="black" d="M244.55,-210C241.54,-221.5 237.49,-236.93 234.05,-250.08"/>
+<polygon fill="black" stroke="black" points="230.59,-249.47 231.45,-260.03 237.36,-251.24 230.59,-249.47"/>
+<text text-anchor="middle" x="241.55" y="-212.6" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Add21&#45;&gt;Con_20 -->
+<g id="edge14" class="edge">
+<title>Add21&#45;&gt;Con_20</title>
+<path fill="none" stroke="black" d="M258.64,-209.2C265.9,-221.4 275.99,-238.34 284.26,-252.24"/>
+<polygon fill="black" stroke="black" points="281.27,-254.05 289.39,-260.85 287.28,-250.47 281.27,-254.05"/>
+<text text-anchor="middle" x="255.64" y="-211.8" font-family="Helvetica,sans-Serif" font-size="8.00">2</text>
+</g>
+<!-- Return24&#45;&gt;If11 -->
+<g id="edge15" class="edge">
+<title>Return24&#45;&gt;If11:p1</title>
+<path fill="none" stroke="red" d="M180.73,-124.08C176.33,-133.41 171.65,-145.54 169.81,-157.76"/>
+<polygon fill="red" stroke="red" points="166.3,-157.76 169,-168 173.28,-158.31 166.3,-157.76"/>
+<text text-anchor="middle" x="177.73" y="-126.68" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- Return24&#45;&gt;Add21 -->
+<g id="edge16" class="edge">
+<title>Return24&#45;&gt;Add21</title>
+<path fill="none" stroke="black" d="M202.22,-124.4C210.86,-136.7 222.55,-153.35 232.09,-166.92"/>
+<polygon fill="black" stroke="black" points="229.37,-169.15 237.98,-175.32 235.1,-165.12 229.37,-169.15"/>
+<text text-anchor="middle" x="199.22" y="-127" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+</g>
+</svg>
diff --git a/docs/chapter09/09-graph2.gv b/docs/chapter09/09-graph2.gv
new file mode 100644
index 00000000..1a1f7a29
--- /dev/null
+++ b/docs/chapter09/09-graph2.gv
@@ -0,0 +1,63 @@
+digraph chapter09 {
+/*
+int x = arg + arg;
+if(arg < 10) {
+ return arg + arg;
+}
+else {
+ x = x + 1;
+}
+return x;
+
+*/
+ rankdir=BT;
+ ordering="in";
+ concentrate="true";
+ compound="true";
+ subgraph cluster_Nodes {
+ Start2 [ shape=plaintext label=<
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
+ <TR><TD BGCOLOR="yellow">Start</TD></TR>
+ <TR><TD>
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+ <TR><TD PORT="p0" BGCOLOR="yellow">$ctrl</TD><TD PORT="p1">arg</TD></TR>
+ </TABLE>
+ </TD></TR>
+ </TABLE>>
+ ];
+ Stop3 [ shape=box style=filled fillcolor=yellow label="Stop" ];
+ Con_7 [ label="#2" ];
+ Mul8 [ label="*" ];
+ LT9 [ label="<" ];
+ Con_10 [ label="#10" ];
+ If11 [ shape=plaintext label=<
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
+ <TR><TD BGCOLOR="yellow">If</TD></TR>
+ <TR><TD>
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+ <TR><TD PORT="p0" BGCOLOR="yellow">True</TD><TD PORT="p1" BGCOLOR="yellow">False</TD></TR>
+ </TABLE>
+ </TD></TR>
+ </TABLE>>
+ ];
+ Return18 [ shape=box style=filled fillcolor=yellow label="Return" ];
+ Add20 [ label="+" ];
+ Con_21 [ label="#1" ];
+ Return24 [ shape=box style=filled fillcolor=yellow label="Return" ];
+ }
+ edge [ fontname=Helvetica, fontsize=8 ];
+ Stop3 -> Return18[taillabel=0 color=red];
+ Stop3 -> Return24[taillabel=1 color=red];
+ Mul8 -> Start2:p1[taillabel=1];
+ Mul8 -> Con_7[taillabel=2];
+ LT9 -> Start2:p1[taillabel=1];
+ LT9 -> Con_10[taillabel=2];
+ If11 -> Start2:p0[taillabel=0 color=red];
+ If11 -> LT9[taillabel=1];
+ Return18 -> If11:p0[taillabel=0 color=red];
+ Return18 -> Mul8[taillabel=1];
+ Add20 -> Mul8[taillabel=1];
+ Add20 -> Con_21[taillabel=2];
+ Return24 -> If11:p1[taillabel=0 color=red];
+ Return24 -> Add20[taillabel=1];
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+<g id="clust1" class="cluster">
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+<!-- Start2 -->
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+<text text-anchor="middle" x="234" y="-360.3" font-family="Times,serif" font-size="14.00">#10</text>
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+<!-- LT9&#45;&gt;Con_10 -->
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+<title>LT9&#45;&gt;Con_10</title>
+<path fill="none" stroke="black" d="M178.47,-294.41C188.66,-307 203.24,-325 214.9,-339.41"/>
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+<!-- Return18&#45;&gt;Mul8 -->
+<g id="edge10" class="edge">
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+<g id="edge11" class="edge">
+<title>Add20&#45;&gt;Mul8</title>
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diff --git a/docs/chapter09/09-graph3.gv b/docs/chapter09/09-graph3.gv
new file mode 100644
index 00000000..37bb1c53
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+++ b/docs/chapter09/09-graph3.gv
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+<text text-anchor="middle" x="40.69" y="-126.82" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- Return9&#45;&gt;Sub8 -->
+<g id="edge9" class="edge">
+<title>Return9&#45;&gt;Sub8</title>
+<path fill="none" stroke="black" d="M57.73,-124.3C58.5,-132.02 59.43,-141.29 60.29,-149.89"/>
+<polygon fill="black" stroke="black" points="56.81,-150.29 61.29,-159.9 63.78,-149.6 56.81,-150.29"/>
+<text text-anchor="middle" x="54.73" y="-126.9" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+</g>
+</svg>
diff --git a/docs/chapter09/09-graph4.gv b/docs/chapter09/09-graph4.gv
new file mode 100644
index 00000000..8886f73a
--- /dev/null
+++ b/docs/chapter09/09-graph4.gv
@@ -0,0 +1,29 @@
+digraph chapter09 {
+/*
+return arg*arg-arg*arg;
+
+*/
+ rankdir=BT;
+ ordering="in";
+ concentrate="true";
+ compound="true";
+ subgraph cluster_Nodes {
+ Start2 [ shape=plaintext label=<
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
+ <TR><TD BGCOLOR="yellow">Start</TD></TR>
+ <TR><TD>
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+ <TR><TD PORT="p0" BGCOLOR="yellow">$ctrl</TD></TR>
+ </TABLE>
+ </TD></TR>
+ </TABLE>>
+ ];
+ Stop3 [ shape=box style=filled fillcolor=yellow label="Stop" ];
+ Con_9 [ label="#0" ];
+ Return10 [ shape=box style=filled fillcolor=yellow label="Return" ];
+ }
+ edge [ fontname=Helvetica, fontsize=8 ];
+ Stop3 -> Return10[taillabel=0 color=red];
+ Return10 -> Start2:p0[taillabel=0 color=red];
+ Return10 -> Con_9[taillabel=1];
+}
diff --git a/docs/chapter09/09-graph4.svg b/docs/chapter09/09-graph4.svg
new file mode 100644
index 00000000..4eef5414
--- /dev/null
+++ b/docs/chapter09/09-graph4.svg
@@ -0,0 +1,67 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
+ "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<!-- Generated by graphviz version 2.43.0 (0)
+ -->
+<!-- Title: chapter09 Pages: 1 -->
+<svg width="178pt" height="248pt"
+ viewBox="0.00 0.00 178.00 248.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+<g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 244)">
+<title>chapter09</title>
+<polygon fill="white" stroke="transparent" points="-4,4 -4,-244 174,-244 174,4 -4,4"/>
+<g id="clust1" class="cluster">
+<title>cluster_Nodes</title>
+<polygon fill="none" stroke="black" points="8,-8 8,-232 162,-232 162,-8 8,-8"/>
+</g>
+<!-- Start2 -->
+<g id="node1" class="node">
+<title>Start2</title>
+<polygon fill="yellow" stroke="transparent" points="24,-195 24,-220 74,-220 74,-195 24,-195"/>
+<polygon fill="none" stroke="black" points="24,-195 24,-220 74,-220 74,-195 24,-195"/>
+<text text-anchor="start" x="30.5" y="-203.8" font-family="Times,serif" font-size="14.00">Start</text>
+<polygon fill="none" stroke="black" points="24,-164 24,-195 74,-195 74,-164 24,-164"/>
+<polygon fill="yellow" stroke="transparent" points="29,-169 29,-190 69,-190 69,-169 29,-169"/>
+<polygon fill="none" stroke="black" points="29,-169 29,-190 69,-190 69,-169 29,-169"/>
+<text text-anchor="start" x="32" y="-175.8" font-family="Times,serif" font-size="14.00">$ctrl</text>
+</g>
+<!-- Stop3 -->
+<g id="node2" class="node">
+<title>Stop3</title>
+<polygon fill="yellow" stroke="black" points="112,-52 58,-52 58,-16 112,-16 112,-52"/>
+<text text-anchor="middle" x="85" y="-30.3" font-family="Times,serif" font-size="14.00">Stop</text>
+</g>
+<!-- Return10 -->
+<g id="node4" class="node">
+<title>Return10</title>
+<polygon fill="yellow" stroke="black" points="118,-124 52,-124 52,-88 118,-88 118,-124"/>
+<text text-anchor="middle" x="85" y="-102.3" font-family="Times,serif" font-size="14.00">Return</text>
+</g>
+<!-- Stop3&#45;&gt;Return10 -->
+<g id="edge1" class="edge">
+<title>Stop3&#45;&gt;Return10</title>
+<path fill="none" stroke="red" d="M85,-52.3C85,-60.02 85,-69.29 85,-77.89"/>
+<polygon fill="red" stroke="red" points="81.5,-77.9 85,-87.9 88.5,-77.9 81.5,-77.9"/>
+<text text-anchor="middle" x="82" y="-54.9" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- Con_9 -->
+<g id="node3" class="node">
+<title>Con_9</title>
+<ellipse fill="none" stroke="black" cx="127" cy="-192" rx="27" ry="18"/>
+<text text-anchor="middle" x="127" y="-188.3" font-family="Times,serif" font-size="14.00">#0</text>
+</g>
+<!-- Return10&#45;&gt;Start2 -->
+<g id="edge2" class="edge">
+<title>Return10&#45;&gt;Start2:p0</title>
+<path fill="none" stroke="red" d="M68.26,-124.13C60.77,-133.26 52.99,-145.23 50.13,-158.06"/>
+<polygon fill="red" stroke="red" points="46.66,-157.67 49,-168 53.61,-158.46 46.66,-157.67"/>
+<text text-anchor="middle" x="65.26" y="-126.73" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- Return10&#45;&gt;Con_9 -->
+<g id="edge3" class="edge">
+<title>Return10&#45;&gt;Con_9</title>
+<path fill="none" stroke="black" d="M93.7,-124.4C99.66,-136.31 107.65,-152.3 114.31,-165.62"/>
+<polygon fill="black" stroke="black" points="111.28,-167.38 118.88,-174.76 117.54,-164.25 111.28,-167.38"/>
+<text text-anchor="middle" x="90.7" y="-127" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+</g>
+</svg>
diff --git a/docs/chapter09/09-graph5.gv b/docs/chapter09/09-graph5.gv
new file mode 100644
index 00000000..72274239
--- /dev/null
+++ b/docs/chapter09/09-graph5.gv
@@ -0,0 +1,63 @@
+digraph chapter09 {
+/*
+int step = 1;
+while (arg < 10) {
+ arg = arg + step + 1;
+}
+return arg;
+
+*/
+ rankdir=BT;
+ ordering="in";
+ concentrate="true";
+ compound="true";
+ subgraph cluster_Nodes {
+ Start2 [ shape=plaintext label=<
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
+ <TR><TD BGCOLOR="yellow">Start</TD></TR>
+ <TR><TD>
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+ <TR><TD PORT="p0" BGCOLOR="yellow">$ctrl</TD><TD PORT="p1">arg</TD></TR>
+ </TABLE>
+ </TD></TR>
+ </TABLE>>
+ ];
+ Stop3 [ shape=box style=filled fillcolor=yellow label="Stop" ];
+ Con_6 [ label="#1" ];
+ Loop7 [ shape=box style=filled fillcolor=yellow label="Loop" ];
+ Phi_arg9 [ style=filled fillcolor=lightyellow label="&phi;_arg" ];
+ LT10 [ label="<" ];
+ Con_11 [ label="#10" ];
+ If12 [ shape=plaintext label=<
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
+ <TR><TD BGCOLOR="yellow">If</TD></TR>
+ <TR><TD>
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+ <TR><TD PORT="p0" BGCOLOR="yellow">True</TD><TD PORT="p1" BGCOLOR="yellow">False</TD></TR>
+ </TABLE>
+ </TD></TR>
+ </TABLE>>
+ ];
+ Add16 [ label="+" ];
+ Add18 [ label="+" ];
+ Return21 [ shape=box style=filled fillcolor=yellow label="Return" ];
+ { rank=same; Loop7;Phi_arg9;}
+ }
+ edge [ fontname=Helvetica, fontsize=8 ];
+ Stop3 -> Return21[taillabel=0 color=red];
+ Loop7 -> Start2:p0[taillabel=1 color=red];
+ Loop7 -> If12:p0[taillabel=2 color=red constraint=false];
+ Phi_arg9 -> Loop7 [style=dotted taillabel=0];
+ Phi_arg9 -> Start2:p1[taillabel=1];
+ Phi_arg9 -> Add18[taillabel=2 constraint=false];
+ LT10 -> Phi_arg9[taillabel=1];
+ LT10 -> Con_11[taillabel=2];
+ If12 -> Loop7[taillabel=0 color=red];
+ If12 -> LT10[taillabel=1];
+ Add16 -> Con_6[taillabel=1];
+ Add16 -> Phi_arg9[taillabel=2];
+ Add18 -> Add16[taillabel=1];
+ Add18 -> Con_6[taillabel=2];
+ Return21 -> If12:p1[taillabel=0 color=red];
+ Return21 -> Phi_arg9[taillabel=1];
+}
diff --git a/docs/chapter09/09-graph5.svg b/docs/chapter09/09-graph5.svg
new file mode 100644
index 00000000..9d0698db
--- /dev/null
+++ b/docs/chapter09/09-graph5.svg
@@ -0,0 +1,210 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN"
+ "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
+<!-- Generated by graphviz version 2.43.0 (0)
+ -->
+<!-- Title: chapter09 Pages: 1 -->
+<svg width="338pt" height="492pt"
+ viewBox="0.00 0.00 338.00 492.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+<g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 488)">
+<title>chapter09</title>
+<polygon fill="white" stroke="transparent" points="-4,4 -4,-488 334,-488 334,4 -4,4"/>
+<g id="clust1" class="cluster">
+<title>cluster_Nodes</title>
+<polygon fill="none" stroke="black" points="8,-8 8,-476 322,-476 322,-8 8,-8"/>
+</g>
+<!-- Start2 -->
+<g id="node1" class="node">
+<title>Start2</title>
+<polygon fill="yellow" stroke="transparent" points="153,-439 153,-464 234,-464 234,-439 153,-439"/>
+<polygon fill="none" stroke="black" points="153,-439 153,-464 234,-464 234,-439 153,-439"/>
+<text text-anchor="start" x="175" y="-447.8" font-family="Times,serif" font-size="14.00">Start</text>
+<polygon fill="none" stroke="black" points="153,-408 153,-439 234,-439 234,-408 153,-408"/>
+<polygon fill="yellow" stroke="transparent" points="158,-413 158,-434 198,-434 198,-413 158,-413"/>
+<polygon fill="none" stroke="black" points="158,-413 158,-434 198,-434 198,-413 158,-413"/>
+<text text-anchor="start" x="161" y="-419.8" font-family="Times,serif" font-size="14.00">$ctrl</text>
+<polygon fill="none" stroke="black" points="198,-413 198,-434 229,-434 229,-413 198,-413"/>
+<text text-anchor="start" x="201" y="-419.8" font-family="Times,serif" font-size="14.00">arg</text>
+</g>
+<!-- Stop3 -->
+<g id="node2" class="node">
+<title>Stop3</title>
+<polygon fill="yellow" stroke="black" points="271,-52 217,-52 217,-16 271,-16 271,-52"/>
+<text text-anchor="middle" x="244" y="-30.3" font-family="Times,serif" font-size="14.00">Stop</text>
+</g>
+<!-- Return21 -->
+<g id="node11" class="node">
+<title>Return21</title>
+<polygon fill="yellow" stroke="black" points="277,-124 211,-124 211,-88 277,-88 277,-124"/>
+<text text-anchor="middle" x="244" y="-102.3" font-family="Times,serif" font-size="14.00">Return</text>
+</g>
+<!-- Stop3&#45;&gt;Return21 -->
+<g id="edge1" class="edge">
+<title>Stop3&#45;&gt;Return21</title>
+<path fill="none" stroke="red" d="M244,-52.3C244,-60.02 244,-69.29 244,-77.89"/>
+<polygon fill="red" stroke="red" points="240.5,-77.9 244,-87.9 247.5,-77.9 240.5,-77.9"/>
+<text text-anchor="middle" x="241" y="-54.9" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- Con_6 -->
+<g id="node3" class="node">
+<title>Con_6</title>
+<ellipse fill="none" stroke="black" cx="43" cy="-350" rx="27" ry="18"/>
+<text text-anchor="middle" x="43" y="-346.3" font-family="Times,serif" font-size="14.00">#1</text>
+</g>
+<!-- Loop7 -->
+<g id="node4" class="node">
+<title>Loop7</title>
+<polygon fill="yellow" stroke="black" points="142,-368 88,-368 88,-332 142,-332 142,-368"/>
+<text text-anchor="middle" x="115" y="-346.3" font-family="Times,serif" font-size="14.00">Loop</text>
+</g>
+<!-- Loop7&#45;&gt;Start2 -->
+<g id="edge2" class="edge">
+<title>Loop7&#45;&gt;Start2:p0</title>
+<path fill="none" stroke="red" d="M117.35,-368.06C120.75,-386.19 128.75,-413.28 146.69,-420.93"/>
+<polygon fill="red" stroke="red" points="146.51,-424.46 157,-423 147.89,-417.6 146.51,-424.46"/>
+<text text-anchor="middle" x="114.35" y="-370.66" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- If12 -->
+<g id="node8" class="node">
+<title>If12</title>
+<polygon fill="yellow" stroke="transparent" points="147,-195 147,-220 241,-220 241,-195 147,-195"/>
+<polygon fill="none" stroke="black" points="147,-195 147,-220 241,-220 241,-195 147,-195"/>
+<text text-anchor="start" x="188.5" y="-203.8" font-family="Times,serif" font-size="14.00">If</text>
+<polygon fill="none" stroke="black" points="147,-164 147,-195 241,-195 241,-164 147,-164"/>
+<polygon fill="yellow" stroke="transparent" points="152,-169 152,-190 192,-190 192,-169 152,-169"/>
+<polygon fill="none" stroke="black" points="152,-169 152,-190 192,-190 192,-169 152,-169"/>
+<text text-anchor="start" x="155" y="-175.8" font-family="Times,serif" font-size="14.00">True</text>
+<polygon fill="yellow" stroke="transparent" points="192,-169 192,-190 236,-190 236,-169 192,-169"/>
+<polygon fill="none" stroke="black" points="192,-169 192,-190 236,-190 236,-169 192,-169"/>
+<text text-anchor="start" x="195" y="-175.8" font-family="Times,serif" font-size="14.00">False</text>
+</g>
+<!-- Loop7&#45;&gt;If12 -->
+<g id="edge3" class="edge">
+<title>Loop7&#45;&gt;If12:p0</title>
+<path fill="none" stroke="red" d="M142.11,-336.15C145.11,-334.74 148.12,-333.34 151,-332 186,-315.76 209.13,-328.45 230,-296 238.66,-282.54 239,-273.23 230,-260 205.55,-224.03 163.45,-259.97 139,-224 125.26,-203.78 121.98,-186.54 139,-169 146.02,-161.76 158.99,-157.07 166.4,-159.61"/>
+<polygon fill="red" stroke="red" points="163.54,-161.62 172,-168 169.36,-157.74 163.54,-161.62"/>
+<text text-anchor="middle" x="145.11" y="-329.75" font-family="Helvetica,sans-Serif" font-size="8.00">2</text>
+</g>
+<!-- Phi_arg9 -->
+<g id="node5" class="node">
+<title>Phi_arg9</title>
+<ellipse fill="lightyellow" stroke="black" cx="277" cy="-350" rx="37.09" ry="18"/>
+<text text-anchor="middle" x="277" y="-346.3" font-family="Times,serif" font-size="14.00">φ_arg</text>
+</g>
+<!-- Phi_arg9&#45;&gt;Start2 -->
+<g id="edge5" class="edge">
+<title>Phi_arg9&#45;&gt;Start2:p1</title>
+<path fill="none" stroke="black" d="M273.71,-368.06C269.21,-386.44 259.37,-414.03 239.96,-421.23"/>
+<polygon fill="black" stroke="black" points="239.23,-417.81 230,-423 240.46,-424.7 239.23,-417.81"/>
+<text text-anchor="middle" x="270.71" y="-370.66" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Phi_arg9&#45;&gt;Loop7 -->
+<g id="edge4" class="edge">
+<title>Phi_arg9&#45;&gt;Loop7</title>
+<path fill="none" stroke="black" stroke-dasharray="1,5" d="M258.53,-334.01C248.46,-326.34 235.34,-317.98 222,-314 195.59,-306.13 186,-304.88 160,-314 152.86,-316.5 146.01,-320.67 139.91,-325.3"/>
+<polygon fill="black" stroke="black" points="137.55,-322.71 132.08,-331.78 142.01,-328.1 137.55,-322.71"/>
+<text text-anchor="middle" x="255.53" y="-327.61" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- Add18 -->
+<g id="node10" class="node">
+<title>Add18</title>
+<ellipse fill="none" stroke="black" cx="66" cy="-192" rx="27" ry="18"/>
+<text text-anchor="middle" x="66" y="-188.3" font-family="Times,serif" font-size="14.00">+</text>
+</g>
+<!-- Phi_arg9&#45;&gt;Add18 -->
+<g id="edge6" class="edge">
+<title>Phi_arg9&#45;&gt;Add18</title>
+<path fill="none" stroke="black" d="M249.01,-337.87C243.12,-335.75 236.9,-333.68 231,-332 153.36,-309.94 104.1,-358.47 53,-296 35.4,-274.49 43.72,-241.53 53.12,-218.71"/>
+<polygon fill="black" stroke="black" points="56.43,-219.88 57.28,-209.32 50.03,-217.04 56.43,-219.88"/>
+<text text-anchor="middle" x="246.01" y="-331.47" font-family="Helvetica,sans-Serif" font-size="8.00">2</text>
+</g>
+<!-- LT10 -->
+<g id="node6" class="node">
+<title>LT10</title>
+<ellipse fill="none" stroke="black" cx="194" cy="-278" rx="27" ry="18"/>
+<text text-anchor="middle" x="194" y="-274.3" font-family="Times,serif" font-size="14.00">&lt;</text>
+</g>
+<!-- LT10&#45;&gt;Phi_arg9 -->
+<g id="edge7" class="edge">
+<title>LT10&#45;&gt;Phi_arg9</title>
+<path fill="none" stroke="black" d="M210.4,-292.83C222.06,-302.66 237.95,-316.07 251.29,-327.31"/>
+<polygon fill="black" stroke="black" points="249.3,-330.22 259.2,-333.99 253.81,-324.86 249.3,-330.22"/>
+<text text-anchor="middle" x="207.4" y="-295.43" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Con_11 -->
+<g id="node7" class="node">
+<title>Con_11</title>
+<ellipse fill="none" stroke="black" cx="191" cy="-350" rx="30.59" ry="18"/>
+<text text-anchor="middle" x="191" y="-346.3" font-family="Times,serif" font-size="14.00">#10</text>
+</g>
+<!-- LT10&#45;&gt;Con_11 -->
+<g id="edge8" class="edge">
+<title>LT10&#45;&gt;Con_11</title>
+<path fill="none" stroke="black" d="M193.26,-296.3C192.93,-304.02 192.53,-313.29 192.16,-321.89"/>
+<polygon fill="black" stroke="black" points="188.66,-321.75 191.73,-331.9 195.66,-322.05 188.66,-321.75"/>
+<text text-anchor="middle" x="190.26" y="-298.9" font-family="Helvetica,sans-Serif" font-size="8.00">2</text>
+</g>
+<!-- If12&#45;&gt;Loop7 -->
+<g id="edge9" class="edge">
+<title>If12&#45;&gt;Loop7</title>
+<path fill="none" stroke="red" d="M176.87,-224.21C170.8,-235.44 164,-248.24 158,-260 147.34,-280.9 135.81,-304.85 127.37,-322.64"/>
+<polygon fill="red" stroke="red" points="124.14,-321.29 123.03,-331.83 130.46,-324.29 124.14,-321.29"/>
+<text text-anchor="middle" x="173.87" y="-226.81" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- If12&#45;&gt;LT10 -->
+<g id="edge10" class="edge">
+<title>If12&#45;&gt;LT10</title>
+<path fill="none" stroke="black" d="M194,-224.28C194,-232.58 194,-241.48 194,-249.56"/>
+<polygon fill="black" stroke="black" points="190.5,-249.6 194,-259.6 197.5,-249.6 190.5,-249.6"/>
+<text text-anchor="middle" x="191" y="-226.88" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Add16 -->
+<g id="node9" class="node">
+<title>Add16</title>
+<ellipse fill="none" stroke="black" cx="89" cy="-278" rx="27" ry="18"/>
+<text text-anchor="middle" x="89" y="-274.3" font-family="Times,serif" font-size="14.00">+</text>
+</g>
+<!-- Add16&#45;&gt;Con_6 -->
+<g id="edge11" class="edge">
+<title>Add16&#45;&gt;Con_6</title>
+<path fill="none" stroke="black" d="M78.56,-294.88C72.8,-303.66 65.52,-314.74 59.04,-324.58"/>
+<polygon fill="black" stroke="black" points="55.96,-322.9 53.4,-333.18 61.81,-326.74 55.96,-322.9"/>
+<text text-anchor="middle" x="75.56" y="-297.48" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Add16&#45;&gt;Phi_arg9 -->
+<g id="edge12" class="edge">
+<title>Add16&#45;&gt;Phi_arg9</title>
+<path fill="none" stroke="black" d="M112.05,-287.58C143.64,-299.35 200.8,-320.63 238.83,-334.79"/>
+<polygon fill="black" stroke="black" points="237.94,-338.19 248.54,-338.4 240.39,-331.63 237.94,-338.19"/>
+<text text-anchor="middle" x="115.05" y="-290.18" font-family="Helvetica,sans-Serif" font-size="8.00">2</text>
+</g>
+<!-- Add18&#45;&gt;Con_6 -->
+<g id="edge14" class="edge">
+<title>Add18&#45;&gt;Con_6</title>
+<path fill="none" stroke="black" d="M62.31,-210.01C59.48,-223.51 55.62,-242.9 53,-260 49.85,-280.62 47.25,-304.07 45.5,-321.72"/>
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+<!-- Add18&#45;&gt;Add16 -->
+<g id="edge13" class="edge">
+<title>Add18&#45;&gt;Add16</title>
+<path fill="none" stroke="black" d="M70.65,-210C73.8,-221.5 78.03,-236.93 81.63,-250.08"/>
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+<!-- Return21&#45;&gt;If12 -->
+<g id="edge15" class="edge">
+<title>Return21&#45;&gt;If12:p1</title>
+<path fill="none" stroke="red" d="M230.4,-124.06C224.14,-133.27 217.55,-145.31 215.05,-157.87"/>
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diff --git a/docs/chapter09/09-graph6.gv b/docs/chapter09/09-graph6.gv
new file mode 100644
index 00000000..56dc6ada
--- /dev/null
+++ b/docs/chapter09/09-graph6.gv
@@ -0,0 +1,60 @@
+digraph chapter09 {
+/*
+int step = 1;
+while (arg < 10) {
+ arg = arg + step + 1;
+}
+return arg;
+
+*/
+ rankdir=BT;
+ ordering="in";
+ concentrate="true";
+ compound="true";
+ subgraph cluster_Nodes {
+ Start2 [ shape=plaintext label=<
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
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+ <TR><TD>
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+ <TR><TD PORT="p0" BGCOLOR="yellow">$ctrl</TD><TD PORT="p1">arg</TD></TR>
+ </TABLE>
+ </TD></TR>
+ </TABLE>>
+ ];
+ Stop3 [ shape=box style=filled fillcolor=yellow label="Stop" ];
+ Loop7 [ shape=box style=filled fillcolor=yellow label="Loop" ];
+ Phi_arg9 [ style=filled fillcolor=lightyellow label="&phi;_arg" ];
+ LT10 [ label="<" ];
+ Con_11 [ label="#10" ];
+ If12 [ shape=plaintext label=<
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0" CELLPADDING="4">
+ <TR><TD BGCOLOR="yellow">If</TD></TR>
+ <TR><TD>
+ <TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+ <TR><TD PORT="p0" BGCOLOR="yellow">True</TD><TD PORT="p1" BGCOLOR="yellow">False</TD></TR>
+ </TABLE>
+ </TD></TR>
+ </TABLE>>
+ ];
+ Return21 [ shape=box style=filled fillcolor=yellow label="Return" ];
+ Con_24 [ label="#2" ];
+ Add25 [ label="+" ];
+ { rank=same; Loop7;Phi_arg9;}
+ }
+ edge [ fontname=Helvetica, fontsize=8 ];
+ Stop3 -> Return21[taillabel=0 color=red];
+ Loop7 -> Start2:p0[taillabel=1 color=red];
+ Loop7 -> If12:p0[taillabel=2 color=red constraint=false];
+ Phi_arg9 -> Loop7 [style=dotted taillabel=0];
+ Phi_arg9 -> Start2:p1[taillabel=1];
+ Phi_arg9 -> Add25[taillabel=2 constraint=false];
+ LT10 -> Phi_arg9[taillabel=1];
+ LT10 -> Con_11[taillabel=2];
+ If12 -> Loop7[taillabel=0 color=red];
+ If12 -> LT10[taillabel=1];
+ Return21 -> If12:p1[taillabel=0 color=red];
+ Return21 -> Phi_arg9[taillabel=1];
+ Add25 -> Phi_arg9[taillabel=1];
+ Add25 -> Con_24[taillabel=2];
+}
diff --git a/docs/chapter09/09-graph6.svg b/docs/chapter09/09-graph6.svg
new file mode 100644
index 00000000..36c70099
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+++ b/docs/chapter09/09-graph6.svg
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+ "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
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+<!-- Title: chapter09 Pages: 1 -->
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+<polygon fill="white" stroke="transparent" points="-4,4 -4,-488 334,-488 334,4 -4,4"/>
+<g id="clust1" class="cluster">
+<title>cluster_Nodes</title>
+<polygon fill="none" stroke="black" points="8,-8 8,-476 322,-476 322,-8 8,-8"/>
+</g>
+<!-- Start2 -->
+<g id="node1" class="node">
+<title>Start2</title>
+<polygon fill="yellow" stroke="transparent" points="149,-439 149,-464 230,-464 230,-439 149,-439"/>
+<polygon fill="none" stroke="black" points="149,-439 149,-464 230,-464 230,-439 149,-439"/>
+<text text-anchor="start" x="171" y="-447.8" font-family="Times,serif" font-size="14.00">Start</text>
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+<text text-anchor="start" x="157" y="-419.8" font-family="Times,serif" font-size="14.00">$ctrl</text>
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+<text text-anchor="start" x="197" y="-419.8" font-family="Times,serif" font-size="14.00">arg</text>
+</g>
+<!-- Stop3 -->
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+<title>Stop3</title>
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+<text text-anchor="middle" x="130" y="-30.3" font-family="Times,serif" font-size="14.00">Stop</text>
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+<!-- Return21 -->
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+<text text-anchor="middle" x="130" y="-102.3" font-family="Times,serif" font-size="14.00">Return</text>
+</g>
+<!-- Stop3&#45;&gt;Return21 -->
+<g id="edge1" class="edge">
+<title>Stop3&#45;&gt;Return21</title>
+<path fill="none" stroke="red" d="M130,-52.3C130,-60.02 130,-69.29 130,-77.89"/>
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+<text text-anchor="middle" x="127" y="-54.9" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
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+<!-- Loop7 -->
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+<title>Loop7</title>
+<polygon fill="yellow" stroke="black" points="314,-368 260,-368 260,-332 314,-332 314,-368"/>
+<text text-anchor="middle" x="287" y="-346.3" font-family="Times,serif" font-size="14.00">Loop</text>
+</g>
+<!-- Loop7&#45;&gt;Start2 -->
+<g id="edge2" class="edge">
+<title>Loop7&#45;&gt;Start2:p0</title>
+<path fill="none" stroke="red" d="M259.93,-364.13C234.34,-376.71 197.56,-395.24 181.73,-405.41"/>
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+<text text-anchor="middle" x="256.93" y="-357.73" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
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+<polygon fill="none" stroke="black" points="36,-195 36,-220 130,-220 130,-195 36,-195"/>
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+<text text-anchor="start" x="44" y="-175.8" font-family="Times,serif" font-size="14.00">True</text>
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+<polygon fill="none" stroke="black" points="81,-169 81,-190 125,-190 125,-169 81,-169"/>
+<text text-anchor="start" x="84" y="-175.8" font-family="Times,serif" font-size="14.00">False</text>
+</g>
+<!-- Loop7&#45;&gt;If12 -->
+<g id="edge3" class="edge">
+<title>Loop7&#45;&gt;If12:p0</title>
+<path fill="none" stroke="red" d="M259.79,-335.23C256.86,-334.03 253.9,-332.92 251,-332 163.26,-304.1 109.06,-364.01 47,-296 22.33,-268.96 18.57,-203.69 31.46,-184.44"/>
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+<text text-anchor="middle" x="256.79" y="-328.83" font-family="Helvetica,sans-Serif" font-size="8.00">2</text>
+</g>
+<!-- Phi_arg9 -->
+<g id="node4" class="node">
+<title>Phi_arg9</title>
+<ellipse fill="lightyellow" stroke="black" cx="133" cy="-350" rx="37.09" ry="18"/>
+<text text-anchor="middle" x="133" y="-346.3" font-family="Times,serif" font-size="14.00">φ_arg</text>
+</g>
+<!-- Phi_arg9&#45;&gt;Start2 -->
+<g id="edge5" class="edge">
+<title>Phi_arg9&#45;&gt;Start2:p1</title>
+<path fill="none" stroke="black" d="M162.55,-360.93C181.21,-369 202.84,-382.27 208.56,-401.87"/>
+<polygon fill="black" stroke="black" points="205.12,-402.59 210,-412 212.05,-401.61 205.12,-402.59"/>
+<text text-anchor="middle" x="159.55" y="-363.53" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Phi_arg9&#45;&gt;Loop7 -->
+<g id="edge4" class="edge">
+<title>Phi_arg9&#45;&gt;Loop7</title>
+<path fill="none" stroke="black" stroke-dasharray="1,5" d="M151.47,-334.01C161.54,-326.34 174.66,-317.98 188,-314 211,-307.14 219.35,-306.06 242,-314 249.14,-316.5 255.99,-320.67 262.09,-325.3"/>
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+</g>
+<!-- Add25 -->
+<g id="node10" class="node">
+<title>Add25</title>
+<ellipse fill="none" stroke="black" cx="209" cy="-278" rx="27" ry="18"/>
+<text text-anchor="middle" x="209" y="-274.3" font-family="Times,serif" font-size="14.00">+</text>
+</g>
+<!-- LT10 -->
+<g id="node5" class="node">
+<title>LT10</title>
+<ellipse fill="none" stroke="black" cx="83" cy="-278" rx="27" ry="18"/>
+<text text-anchor="middle" x="83" y="-274.3" font-family="Times,serif" font-size="14.00">&lt;</text>
+</g>
+<!-- LT10&#45;&gt;Phi_arg9 -->
+<g id="edge7" class="edge">
+<title>LT10&#45;&gt;Phi_arg9</title>
+<path fill="none" stroke="black" d="M94.1,-294.54C100.33,-303.26 108.25,-314.35 115.31,-324.24"/>
+<polygon fill="black" stroke="black" points="112.58,-326.43 121.24,-332.53 118.27,-322.36 112.58,-326.43"/>
+<text text-anchor="middle" x="91.1" y="-297.14" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Con_11 -->
+<g id="node6" class="node">
+<title>Con_11</title>
+<ellipse fill="none" stroke="black" cx="47" cy="-350" rx="30.59" ry="18"/>
+<text text-anchor="middle" x="47" y="-346.3" font-family="Times,serif" font-size="14.00">#10</text>
+</g>
+<!-- LT10&#45;&gt;Con_11 -->
+<g id="edge8" class="edge">
+<title>LT10&#45;&gt;Con_11</title>
+<path fill="none" stroke="black" d="M74.65,-295.24C70.35,-303.6 65.01,-313.98 60.17,-323.39"/>
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+<text text-anchor="middle" x="71.65" y="-297.84" font-family="Helvetica,sans-Serif" font-size="8.00">2</text>
+</g>
+<!-- If12&#45;&gt;Loop7 -->
+<g id="edge9" class="edge">
+<title>If12&#45;&gt;Loop7</title>
+<path fill="none" stroke="red" d="M138.19,-204.98C172.47,-214.83 215.47,-231.87 245,-260 262.62,-276.78 273.63,-302.43 279.94,-321.89"/>
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+<text text-anchor="middle" x="141.19" y="-198.58" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- If12&#45;&gt;LT10 -->
+<g id="edge10" class="edge">
+<title>If12&#45;&gt;LT10</title>
+<path fill="none" stroke="black" d="M83,-224.28C83,-232.58 83,-241.48 83,-249.56"/>
+<polygon fill="black" stroke="black" points="79.5,-249.6 83,-259.6 86.5,-249.6 79.5,-249.6"/>
+<text text-anchor="middle" x="80" y="-226.88" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Return21&#45;&gt;Phi_arg9 -->
+<g id="edge12" class="edge">
+<title>Return21&#45;&gt;Phi_arg9</title>
+<path fill="none" stroke="black" d="M137.07,-124.33C140.84,-134.53 145.09,-147.78 147,-160 155.96,-217.25 145.96,-285.18 138.86,-322"/>
+<polygon fill="black" stroke="black" points="135.39,-321.46 136.86,-331.95 142.26,-322.84 135.39,-321.46"/>
+<text text-anchor="middle" x="134.07" y="-126.93" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Return21&#45;&gt;If12 -->
+<g id="edge11" class="edge">
+<title>Return21&#45;&gt;If12:p1</title>
+<path fill="none" stroke="red" d="M117.92,-124C112.25,-133.3 106.24,-145.44 103.95,-157.94"/>
+<polygon fill="red" stroke="red" points="100.46,-157.71 103,-168 107.43,-158.38 100.46,-157.71"/>
+<text text-anchor="middle" x="114.92" y="-126.6" font-family="Helvetica,sans-Serif" font-size="8.00">0</text>
+</g>
+<!-- Con_24 -->
+<g id="node9" class="node">
+<title>Con_24</title>
+<ellipse fill="none" stroke="black" cx="215" cy="-350" rx="27" ry="18"/>
+<text text-anchor="middle" x="215" y="-346.3" font-family="Times,serif" font-size="14.00">#2</text>
+</g>
+<!-- Add25&#45;&gt;Phi_arg9 -->
+<g id="edge13" class="edge">
+<title>Add25&#45;&gt;Phi_arg9</title>
+<path fill="none" stroke="black" d="M185.95,-300.23C176.82,-308.64 166.31,-318.32 157.07,-326.83"/>
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+<text text-anchor="middle" x="190.62" y="-295.77" font-family="Helvetica,sans-Serif" font-size="8.00">1</text>
+</g>
+<!-- Add25&#45;&gt;Con_24 -->
+<g id="edge14" class="edge">
+<title>Add25&#45;&gt;Con_24</title>
+<path fill="none" stroke="black" d="M210.48,-296.3C211.14,-304.02 211.94,-313.29 212.68,-321.89"/>
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+</svg>
diff --git a/docs/chapter09/Makefile b/docs/chapter09/Makefile
new file mode 100644
index 00000000..12659b8f
--- /dev/null
+++ b/docs/chapter09/Makefile
@@ -0,0 +1,12 @@
+GV := $(wildcard *.gv)
+SVG := $(patsubst %.gv,%.svg,$(GV))
+
+.PHONY: all
+all: $(SVG)
+
+%.svg: %.gv
+ dot -Tsvg $< > $@
+
+.PHONY: clean
+clean:
+ @rm -f $(SVG)
diff --git a/docs/chapter09/README.md b/docs/chapter09/README.md
new file mode 100644
index 00000000..85ebd168
--- /dev/null
+++ b/docs/chapter09/README.md
@@ -0,0 +1,275 @@
+# Chapter 9: Global Value Numbering and Iterative Peepholes
+
+In this chapter:
+
+* We add Global Value Numbering (Common Subexpression Elimination)
+* We add a post-parse iterate-peepholes-to-fixed-point optimization
+
+No language changes in this chapter, just adding optimizations.
+
+You can also read [this chapter](https://github.com/SeaOfNodes/Simple/tree/linear-chapter09) in a linear Git revision history on the [linear](https://github.com/SeaOfNodes/Simple/tree/linear) branch and [compare](https://github.com/SeaOfNodes/Simple/compare/linear-chapter08...linear-chapter09) it to the previous chapter.
+
+## Engineering Peepholes
+
+The goal for Ch 9 is to "finish out" the Peepholes. Not that no more peeps will
+appear, on the contrary lots will - but this is the infrastructure to organize
+them, engineer them safe and sane; to apply them until a fixed point is reached.
+
+Really the goal here is to be fearless about adding a new peephole; if you got
+it wrong you'll assert pretty fast. If you got it right, that new peep will
+just run alongside all the others and they will all mutually benefit each other.
+
+
+## Global Value Numbering
+
+Global Value Numbering works via a classic hash table, hashing on a Node's
+opcode and inputs. If two Nodes do the same function on the same inputs, they
+get the same result - and can be shared.
+
+* We add a global static hash table `GVN` in Node.
+* We add a `Node.equals` call. Two Nodes are equals if they have the same
+ opcode - same Java class - on the same inputs.
+* We add a `hashCode` on the Node opcode (proxy: Node string name) and inputs.
+* `ConstantNode` and a few others need some extra custom bits here: the
+ constant 17 is not the same as 99, but both are the same `ConstantNode` class
+ and label. The `eq` and `hash` calls check (or hash) these extra bits.
+
+Since we edit the graph a lot, Nodes can have their inputs change which changes
+their hash which means they can't be found in the GVN table. E.g. we swap out
+the `Add` for a `Con` in:
+
+ (Mul (Add 4 8) x) // Fold the constant
+ (Mul 12 x) // The `Mul` changes hash and inputs
+
+The fix for this is to require Nodes NOT be in the `GVN` table when their edges
+modify; they need some sort of "edge lock". If "edges are locked", we need to
+remove the Node from `GVN` first, before modifying the edges.
+
+* We use the `_hash` field as both a cached hash code and as the edge lock. If
+ zero the Node is unlocked and NOT in `GVN`. If non-zero, the Node is
+ "edge-locked" and IS in `GVN`.
+* The `hashCode` function uses the cached hash if available and disallows an
+ accidental zero hash.
+* We add a `unlock()` call to remove a Node from `GVN` before any edge is
+ changed. This is inserted in front of all calls which hack Node edges. All
+ edge modify code paths already ensure the Node is re-peepholed, and during
+ this revisit the Node will get re-inserted in the `GVN` table.
+
+This new `GVN` table is used in `peepholeOpt()` (and `peephole()`) to look for common
+subexpressions on every peephole'd Node. If the Node has a zero hash, we look
+for a hit against some previous identical Node. If found, we use the prior
+Node and dead-code-eliminate this one. If not found, we insert this Node
+into `GVN` as the "golden instance". If a Node already has a non-zero hash
+we know it IS the "golden instance" and do not need to look in `GVN`.
+
+This entire optimization takes about a dozen lines in `iter()`, plus the common
+shared `equals` and `hashCode` (about 50 more lines counting comments).
+
+One of our invariants is that Types monotonically increase while running
+peepholes. GVN can break this briefly: of the two equivalent Nodes one has
+already had its `_type` lifted but not the other. Depending on which of the
+two Nodes is kept, we might choose the Node with the "lower" `_type`. This is
+"lower" in the Type lattice sense. Both types must be correct, and a
+`compute()` call on both nodes must produce the same Type, which must be equal
+to the JOIN. A fix is to compute a JOIN (not a MEET) over the two Nodes' types.
+
+
+## Post-Parse Iterative Peepholes
+
+The post-Parse `IterPeeps` iterates the peepholes to a fixed point - so
+no more peepholes apply. This should be linear because peepholes rarely
+(never?) increase code size. The graph should monotonically reduce in some
+dimension, which is usually size. It might also reduce in e.g. number of
+MulNodes or Load/Store nodes, swapping out more "expensive" Nodes for cheaper
+ones.
+
+The theoretical overall worklist is mindless just grabbing the next thing and
+doing it. If the graph changes, put the neighbors on the worklist. Lather,
+Rinse, Repeat until the worklist runs dry.
+
+The main issues we have to deal with:
+
+* Nodes have uses; replacing some set of Nodes with another requires more graph
+ reworking. Not rocket science, but it can be fiddly. Its helpful to have a
+ small set of graph munging utilities, and the strong invariant that the graph
+ is stable and correct between peepholes. In our case `Node.subsume` does
+ most of the munging, building on our prior stable Node utilities.
+
+* Changing a Node also changes the graph "neighborhood". The neigbors need to
+ be checked to see if THEY can also peephole, and so on. After any peephole
+ or graph update we put a Nodes uses and defs on the worklist.
+
+* Our strong invariant is that for all Nodes, either they are on the worklist
+ OR no peephole applies. This invariant is easy to check, although expensive.
+ Basically the normal "iterate peepholes to a fixed point" is linear, and this
+ check is linear at each peephole step... so quadratic overall. Its a useful
+ assert, but one we can disable once the overall algorithm is stable - and
+ then turn it back on again when some new set of peepholes is misbehaving.
+ The code for this is turned on in `IterPeeps.iterate` as `assert
+ progressOnList(stop);`
+
+
+## Distant Neighbors
+
+For some peepholes the "neighborhood" is farther away than just the immediate
+uses or defs, and for these we need a longer range plan. E.g. some peephole
+inspects "this -> A -> B -> C" and will swap itself for "D"; however it fails
+some test at "B". Should "B" ever update we want to revisit "this" and recheck
+his peepholes. So we will need to record a dependence of "this" in "B".
+Updating "B" throws the dependent list ("this") onto the "todo" list.
+
+An example of a distant neighbor check is in `AddNode`, where we check for
+stacked constants: `(Add (Add x 2) 1)` and we'd like `(Add x 3)` instead.
+Suppose we're doing this check and we find instead `(Add (Phi (Add x 2) self)
+1)` The check naturally bails out at the `Phi` since its not an `Add`, but the
+`(Phi y self)` only has one unique input, and will itself peephole to `y`
+eventually. When it does, our stacked `Add` peephole can apply. So the
+failing Add peephole calls `phi.addDep(Add)` and registers a dependency on the
+`Phi`. If the `Phi` indeed later optimizes, we add its depencencies (e.g. the
+`Add`) back on our `IterPeeps` worklist and retry the stacked Add peephole.
+
+The general rule is:
+* **If a peephole pattern inspects a remote node, it must go on the dependency list!**
+* `node.in(1).in(2)` becomes `node.in(1).in(2).addDep(node)`
+
+
+In this chapter we trigger on following patterns
+
+* Some peeps interact with `Phi` inputs; this can be direct or indirect,
+ e.g. `(Add Add( (Phi x) 2 ) 1)`. The peep can progress if all of the `Phi`'s
+ inputs are `Constant`'s. Thus, we make the node a dependent on the `Phi`'s
+ input. We also make the node a dependent of the `Phi`'s region. See
+ `Node.allCons()` and `PhiNode.allCons()`.
+* The pattern `(Add (Add x 1) 2)` adds the outer `Add` as dependency of `x`
+ because `x` becoming a constant would enable progress. See
+ `AddNode.idealize()`
+* When computing a `Phi`'s type, if we observe that the associated region's
+ corresponding control is live, we add the `Phi` as a dependent of the
+ region's control input, because if that control goes dead, it would allow the
+ `Phi` to undergo peephole. See `PhiNode.compute()` and
+ `PhiNode.singleUniqueInput()`.
+
+Changes:
+
+* We add a `ArrayList<Node> _deps` field to Node; initially null.
+* Some peepholes (see above) add dependencies if they fail a remote check, by calling
+ `distant.addDep(this)`. The `addDep` call creates `_deps` and
+ filters for various kinds of duplicate adds.
+* The `IterPeeps` loop, when it finds a change, also moves all the
+ dependents onto the worklist.
+
+
+## Other Concerns
+
+There are more issues we will want to deal with in a later Chapter:
+
+* Blindly running peepholes in any order has some drawbacks:
+
+ - Dead and dying stuff might get peepholes done... and then die. Wasted work.
+ - Dead infinite loops often lead to infinite peephole cycles... if only we
+ would get around to working on the "base" of the dead loop it would fold
+ up.
+ - Some peepholes naturally reduce the graph directly; while some keeps its
+ size the same but reduce other things (e.g. swapping a Mul-by-2 with a
+ Shift), and we might end up with a few which try to grow the graph briefly
+ before collapsing.
+
+* All this means is there's some benefit to running peepholes that reduce the
+ graph directly (e.g. Dead Code Eliminate), before running peeps that reduce
+ other things, before running all other peeps. This implies a sorted
+ worklist, but the count of unique orders is really limited - a radix sort is
+ all that is needed. We'll have to break up the peepholes into some
+ categories like
+ - "strictly reducing" vs
+ - "same Nodes but swapping e.g. `Mul` for `Shift`, vs
+ - getting more freedom (edge bypass), vs
+ - "grow now because shrink later" (inlining lands in this camp).
+
+* Also there's a benefit to not always grabbing from either end of the list -
+ many peep patterns might go quadratic if approached from one end or another,
+ because they modify something then push it back onto the list where it
+ immediately gets pulled again. I.e., you end up spinning in a loop repeating
+ the same peeps while slowly migrating a e.g. left-spine add-tree into a
+ right-spine add-tree. A psuedo-random pull uses randomization to defeat bad
+ peep patterns.
+
+* Why isn't `IterPeeps` just passing over all of the Nodes once or twice,
+ instead of using a worklist with the `addDeps` mechanism? We could even
+ visit them in a defs-before-uses order (e.g. Reverse Post Order).
+
+ In the absense of loops exactly one such pass will find all local peepholes,
+ and indeed the Parser already does this. However, this will fail to find
+ opportunities at loops and farther remote cases - and to get those peepholes
+ around loops will require another visit. It is easy to construct a case
+ requiring O(N) passes, each of cost O(N) and the algorithm quickly goes
+ quadratic.
+
+ The `addDeps` solution avoids this quadratic cost, in exchange for some more
+ costs in writing peepholes.
+
+
+# Examples
+
+## Common SubExpressions via GVN
+
+### Example 1
+
+Here is a small example that illustrates how GVN enables finding common sub-expressions.
+
+```java
+int x = arg + arg;
+if(arg < 10) {
+ return arg + arg;
+}
+else {
+ x = x + 1;
+}
+return x;
+```
+
+Prior to GVN, this would result in following graph. Note that the `arg+arg` is translated to `arg*2`.
+
+![Graph1](./09-graph1.svg)
+
+Adding GVN, we get below. Note how the `arg*2` expression is now reused rather than appearing twice.
+
+![Graph2](./09-graph2.svg)
+
+### Example 2
+
+Being able to reuse common expressions, enables additional optimizations. Here is a simple example:
+
+```java
+return arg*arg-arg*arg;
+```
+
+Without GVN the peepholes cannot see that both sides of the subtraction have the same value.
+
+![Graph3](./09-graph3.svg)
+
+With GVN, the peepholes can do a better job:
+
+![Graph4](./09-graph4.svg)
+
+## Post Parse Iterative Optimizations
+
+The worklist based post parse optimization enables certain optimizations that are not available
+during parsing. For example:
+
+```java
+int step = 1;
+while (arg < 10) {
+ arg = arg + step + 1;
+}
+return arg;
+```
+
+While parsing the `while` loop it is not yet known that `step` is a constant and will not change. Therefore,
+without the post parse optimization we get following:
+
+![Graph5](./09-graph5.svg)
+
+Enabling the post parse worklist based optimization yields below. Notice that now the graph shows `arg+2` inside the
+loop body:
+
+![Graph6](./09-graph6.svg)