Add a diagram of the compiler phases.

2 files changed, 298 insertions, 1 deletions

diff --git a/README.md b/README.md
index f10efc5..653c43b 100644
--- a/README.md
+++ b/README.md
@@ -25,7 +25,11 @@ The cute scheme compiler (like most compilers) consists of a number of
 phases that gradually transform a program from scheme code through
 numerous intermediate representations. The csc compiler has 3 such
 intermediate representations, not counting bytecode itself. These two
-languages are creatively called IR1, IR2, and IR3.
+languages are creatively called IR1, IR2, and IR3. Fig. 1 shows the
+phases of code generation.
+
+![Code generation goes through several intermediate phases, named IR1,
+IR2, and IR3.](design.svg)
 
 ### IR1
 
diff --git a/design.svg b/design.svg
new file mode 100644
index 0000000..d901be2
--- /dev/null
+++ b/design.svg
@@ -0,0 +1,293 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!-- Created with Inkscape (http://www.inkscape.org/) -->
+
+<svg
+   width="1.7300283in"
+   height="2.7169535in"
+   viewBox="0 0 43.942721 69.01062"
+   version="1.1"
+   id="svg5"
+   inkscape:version="1.1.2 (0a00cf5339, 2022-02-04)"
+   sodipodi:docname="design.svg"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:svg="http://www.w3.org/2000/svg">
+  <sodipodi:namedview
+     id="namedview7"
+     pagecolor="#ffffff"
+     bordercolor="#666666"
+     borderopacity="1.0"
+     inkscape:pageshadow="2"
+     inkscape:pageopacity="0.0"
+     inkscape:pagecheckerboard="0"
+     inkscape:document-units="mm"
+     showgrid="true"
+     inkscape:snap-grids="true"
+     inkscape:zoom="0.77771465"
+     inkscape:cx="275.8081"
+     inkscape:cy="380.60232"
+     inkscape:window-width="1873"
+     inkscape:window-height="2098"
+     inkscape:window-x="30"
+     inkscape:window-y="30"
+     inkscape:window-maximized="1"
+     inkscape:current-layer="layer1"
+     units="in"
+     width="6.12164in"
+     fit-margin-top="0"
+     fit-margin-left="0"
+     fit-margin-right="0"
+     fit-margin-bottom="0">
+    <inkscape:grid
+       type="xygrid"
+       id="grid5198"
+       originx="-47.514151"
+       originy="-47.51414" />
+  </sodipodi:namedview>
+  <defs
+     id="defs2">
+    <marker
+       style="overflow:visible"
+       id="Arrow1Lend"
+       refX="0"
+       refY="0"
+       orient="auto"
+       inkscape:stockid="Arrow1Lend"
+       inkscape:isstock="true">
+      <path
+         transform="matrix(-0.8,0,0,-0.8,-10,0)"
+         style="fill:context-stroke;fill-rule:evenodd;stroke:context-stroke;stroke-width:1pt"
+         d="M 0,0 5,-5 -12.5,0 5,5 Z"
+         id="path9927" />
+    </marker>
+    <marker
+       style="overflow:visible"
+       id="DotL"
+       refX="0"
+       refY="0"
+       orient="auto"
+       inkscape:stockid="DotL"
+       inkscape:isstock="true">
+      <path
+         transform="matrix(0.8,0,0,0.8,5.92,0.8)"
+         style="fill:context-stroke;fill-rule:evenodd;stroke:context-stroke;stroke-width:1pt"
+         d="m -2.5,-1 c 0,2.76 -2.24,5 -5,5 -2.76,0 -5,-2.24 -5,-5 0,-2.76 2.24,-5 5,-5 2.76,0 5,2.24 5,5 z"
+         id="path9985" />
+    </marker>
+    <marker
+       style="overflow:visible"
+       id="Arrow1Send"
+       refX="0"
+       refY="0"
+       orient="auto"
+       inkscape:stockid="Arrow1Send"
+       inkscape:isstock="true">
+      <path
+         transform="matrix(-0.2,0,0,-0.2,-1.2,0)"
+         style="fill:context-stroke;fill-rule:evenodd;stroke:context-stroke;stroke-width:1pt"
+         d="M 0,0 5,-5 -12.5,0 5,5 Z"
+         id="path9939" />
+    </marker>
+    <marker
+       style="overflow:visible"
+       id="marker10202"
+       refX="0"
+       refY="0"
+       orient="auto"
+       inkscape:stockid="Arrow1Lstart"
+       inkscape:isstock="true">
+      <path
+         transform="matrix(0.8,0,0,0.8,10,0)"
+         style="fill:context-stroke;fill-rule:evenodd;stroke:context-stroke;stroke-width:1pt"
+         d="M 0,0 5,-5 -12.5,0 5,5 Z"
+         id="path10200" />
+    </marker>
+    <marker
+       style="overflow:visible"
+       id="Arrow2Lend"
+       refX="0"
+       refY="0"
+       orient="auto"
+       inkscape:stockid="Arrow2Lend"
+       inkscape:isstock="true">
+      <path
+         transform="matrix(-1.1,0,0,-1.1,-1.1,0)"
+         d="M 8.7185878,4.0337352 -2.2072895,0.01601326 8.7185884,-4.0017078 c -1.7454984,2.3720609 -1.7354408,5.6174519 -6e-7,8.035443 z"
+         style="fill:context-stroke;fill-rule:evenodd;stroke:context-stroke;stroke-width:0.625;stroke-linejoin:round"
+         id="path9945" />
+    </marker>
+    <marker
+       style="overflow:visible"
+       id="Arrow1Lstart"
+       refX="0"
+       refY="0"
+       orient="auto"
+       inkscape:stockid="Arrow1Lstart"
+       inkscape:isstock="true">
+      <path
+         transform="matrix(0.8,0,0,0.8,10,0)"
+         style="fill:context-stroke;fill-rule:evenodd;stroke:context-stroke;stroke-width:1pt"
+         d="M 0,0 5,-5 -12.5,0 5,5 Z"
+         id="path9924" />
+    </marker>
+  </defs>
+  <g
+     inkscape:label="Layer 1"
+     inkscape:groupmode="layer"
+     id="layer1"
+     transform="translate(-47.514141,-47.514141)">
+    <rect
+       style="fill:#610089;fill-opacity:0.181042;fill-rule:evenodd;stroke:#000000;stroke-width:0.221719;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"
+       id="rect1098"
+       width="26.918482"
+       height="7.4773545"
+       x="47.625"
+       y="47.625" />
+    <text
+       xml:space="preserve"
+       style="font-style:normal;font-weight:normal;font-size:2.99093px;line-height:1.25;font-family:sans-serif;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.0747733"
+       x="50.931828"
+       y="52.610332"
+       id="text3016"><tspan
+         sodipodi:role="line"
+         id="tspan3014"
+         style="stroke-width:0.0747733"
+         x="50.931828"
+         y="52.610332">Scheme code</tspan></text>
+    <rect
+       style="fill:#008100;fill-opacity:0.181042;stroke:#000000;stroke-width:0.168392;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"
+       id="rect5196"
+       width="10.468298"
+       height="7.477356"
+       x="55.102356"
+       y="62.579704" />
+    <text
+       xml:space="preserve"
+       style="font-style:normal;font-weight:normal;font-size:2.99093px;line-height:1.25;font-family:sans-serif;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.0747733"
+       x="58.068321"
+       y="67.442688"
+       id="text7815"><tspan
+         sodipodi:role="line"
+         id="tspan7813"
+         style="stroke-width:0.0747733"
+         x="58.068321"
+         y="67.442688">IR1</tspan></text>
+    <path
+       style="fill:none;stroke:#000000;stroke-width:0.216195;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1;marker-end:url(#Arrow2Lend)"
+       d="m 61.08424,55.102355 v 7.477357"
+       id="path9922"
+       sodipodi:nodetypes="cc" />
+    <text
+       xml:space="preserve"
+       style="font-style:normal;font-weight:normal;font-size:2.99093px;line-height:1.25;font-family:sans-serif;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.0747733"
+       x="62.250111"
+       y="59.408424"
+       id="text12824"><tspan
+         sodipodi:role="line"
+         id="tspan12822"
+         style="stroke-width:0.0747733"
+         x="62.250111"
+         y="59.408424">Macro expander</tspan></text>
+    <path
+       style="fill:none;stroke:#000000;stroke-width:0.216195;stroke-linecap:butt;stroke-linejoin:miter;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1;marker-end:url(#Arrow2Lend)"
+       d="m 61.08424,70.057066 c 0,8.972825 0,8.972825 0,8.972825"
+       id="path13599" />
+    <rect
+       style="fill:#008100;fill-opacity:0.181042;stroke:#000000;stroke-width:0.216195;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"
+       id="rect13711"
+       width="10.468298"
+       height="7.477355"
+       x="55.102356"
+       y="79.029892" />
+    <text
+       xml:space="preserve"
+       style="font-style:normal;font-weight:normal;font-size:2.99093px;line-height:1.25;font-family:sans-serif;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.0747733"
+       x="57.943123"
+       y="83.74025"
+       id="text16509"><tspan
+         sodipodi:role="line"
+         id="tspan16507"
+         style="stroke-width:0.0747733"
+         x="57.943123"
+         y="83.74025">IR2</tspan></text>
+    <text
+       xml:space="preserve"
+       style="font-style:normal;font-weight:normal;font-size:2.99093px;line-height:1.25;font-family:sans-serif;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.0747733"
+       x="62.754745"
+       y="75.154015"
+       id="text20971"><tspan
+         sodipodi:role="line"
+         id="tspan20969"
+         style="stroke-width:0.0747733"
+         x="62.754745"
+         y="75.154015">CPS conversion</tspan></text>
+    <path
+       style="fill:#008100;fill-opacity:0.181042;stroke:#000000;stroke-width:0.216195;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1;marker-end:url(#Arrow2Lend)"
+       d="m 61.08424,86.507247 c 0,8.972828 0,8.972828 0,8.972828"
+       id="path25182" />
+    <rect
+       style="fill:#008100;fill-opacity:0.181042;stroke:#000000;stroke-width:0.216195;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"
+       id="rect25206"
+       width="10.468298"
+       height="7.477355"
+       x="55.102356"
+       y="95.480072" />
+    <text
+       xml:space="preserve"
+       style="font-style:normal;font-weight:normal;font-size:2.99093px;line-height:1.25;font-family:sans-serif;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.0747733"
+       x="57.837982"
+       y="100.01888"
+       id="text27806"><tspan
+         sodipodi:role="line"
+         id="tspan27804"
+         style="stroke-width:0.0747733"
+         x="57.837982"
+         y="100.01888">IR3</tspan></text>
+    <text
+       xml:space="preserve"
+       style="font-style:normal;font-weight:normal;font-size:2.99093px;line-height:1.25;font-family:sans-serif;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.0747733"
+       x="63.228497"
+       y="91.630066"
+       id="text32058"><tspan
+         sodipodi:role="line"
+         id="tspan32056"
+         style="stroke-width:0.0747733"
+         x="63.228497"
+         y="91.630066">Closure conversion</tspan></text>
+    <rect
+       style="fill:#9e0000;fill-opacity:0.181042;stroke:#000000;stroke-width:0.216195;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1"
+       id="rect32522"
+       width="23.927536"
+       height="5.981884"
+       x="49.120472"
+       y="110.43478" />
+    <text
+       xml:space="preserve"
+       style="font-style:normal;font-weight:normal;font-size:2.99093px;line-height:1.25;font-family:sans-serif;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.0747733"
+       x="54.230087"
+       y="114.60877"
+       id="text34462"><tspan
+         sodipodi:role="line"
+         id="tspan34460"
+         style="stroke-width:0.0747733"
+         x="54.230087"
+         y="114.60877">Bytecode</tspan></text>
+    <path
+       style="fill:#9e0000;fill-opacity:0.181042;stroke:#000000;stroke-width:0.216195;stroke-miterlimit:4;stroke-dasharray:none;stroke-opacity:1;marker-end:url(#Arrow2Lend)"
+       d="m 61.08424,102.95743 v 7.47736"
+       id="path36125"
+       sodipodi:nodetypes="cc" />
+    <text
+       xml:space="preserve"
+       style="font-style:normal;font-weight:normal;font-size:2.99093px;line-height:1.25;font-family:sans-serif;fill:#000000;fill-opacity:1;stroke:none;stroke-width:0.0747733"
+       x="62.319099"
+       y="107.33462"
+       id="text39894"><tspan
+         sodipodi:role="line"
+         id="tspan39892"
+         style="stroke-width:0.0747733"
+         x="62.319099"
+         y="107.33462">Code generation</tspan></text>
+  </g>
+</svg>