Add the tiger source code bundle from the book site

Signed-off-by: jmug <u.g.a.mariano@gmail.com>

tiger/chap9/flowgraph.sml

@@ -0,0 +1,23 @@
+structure Flow =
+struct
+    datatype flowgraph = FGRAPH of {control: Graph.graph,
+				    def: Temp.temp list Graph.Table.table,
+				    use: Temp.temp list Graph.Table.table,
+				    ismove: bool Graph.Table.table}
+
+  (* Note:  any "use" within the block is assumed to be BEFORE a "def" 
+        of the same variable.  If there is a def(x) followed by use(x)
+       in the same block, do not mention the use in this data structure,
+       mention only the def.
+
+     More generally:
+       If there are any nonzero number of defs, mention def(x).
+       If there are any nonzero number of uses BEFORE THE FIRST DEF,
+           mention use(x).
+
+     For any node in the graph,  
+           Graph.Table.look(def,node) = SOME(def-list)
+           Graph.Table.look(use,node) = SOME(use-list)
+   *)
+
+end