From 61a8732d85323ce42cc6287e06b1707a4a6f7560 Mon Sep 17 00:00:00 2001
From: Guannan Wei <kiss.kraks@gmail.com>
Date: Thu, 1 Jun 2017 15:57:23 -0600
Subject: [PATCH] Add live variables analysis

---
 live-var.rkt | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 live-var.rkt

diff --git a/live-var.rkt b/live-var.rkt
new file mode 100644
index 0000000..7982f8f
--- /dev/null
+++ b/live-var.rkt
@@ -0,0 +1,97 @@
+#lang racket
+
+;; Live Variables Analysis
+;; A variable is live at a program point if its
+;; current value may be read during the remaining
+;; execution of program.
+
+(require "ast.rkt")
+(require "parser.rkt")
+(require "cfg.rkt")
+(require "dfa.rkt")
+
+(require rackunit)
+
+(define live-variables-analysis
+  (Analysis
+   ; direction
+   'backward
+   ; init
+   (λ (cfg n) (set))
+   ; entry fact
+   (λ (fun cfg entry) (set))
+   ; exit fact
+   (λ (fun cfg exit) (set))
+   ; gen
+   (λ (cfg n)
+     (match n
+       [(Node (Assign id e) _) (get-vars e)]
+       [(Node (Equal l r) _)
+        (set-union (get-vars l) (get-vars r))]
+       [(Node (Greater l r) _)
+        (set-union (get-vars l) (get-vars r))]
+       [(Node (App f args) _)
+        (apply set-union (map get-vars args))]
+       [(Node (Output e) _)
+        (get-vars e)]
+       [(Node (Return e) _)
+        (get-vars e)]
+       [else (set)]))
+   ; kill
+   (λ (cfg n)
+     (match n
+       [(Node (Assign id e) _) (set id)]
+       [else (set)]))
+   ; meet
+   set-union))
+
+(define live-variables
+  (chaotic-iteration live-variables-analysis))
+
+(module+ test
+  (define test-fun
+    (parse-function
+     '{test {}
+            {var x y z}
+            {{:= y 4}
+             {:= x 2}
+             {if {== x y}
+                 {:= z y}
+                 {:= z {* y y}}}
+             {:= x z}}}))
+
+  (define result (live-variables test-fun))
+  (define result-IN (car result))
+  (define result-OUT (cdr result))
+  (check-equal? (make-immutable-hash (hash->list result-IN))
+                (hash
+                 (Node (Assign 'x 2) 2)
+                 (set 'y)
+                 (Node (Assign 'z 'y) 3)
+                 (set 'y)
+                 (Node (Assign 'z (Mult 'y 'y)) 4)
+                 (set 'y)
+                 (Node (Equal 'x 'y) 5)
+                 (set 'x 'y)
+                 (Node (Assign 'x 'z) 7)
+                 (set 'z)
+                 (Node (Assign 'y 4) 1)
+                 (set)
+                 (Node (NoOp) 6)
+                 (set 'z)))
+  (check-equal? (make-immutable-hash (hash->list result-OUT))
+                (hash
+                 (Node (Assign 'x 2) 2)
+                 (set 'x 'y)
+                 (Node (Assign 'z 'y) 3)
+                 (set 'z)
+                 (Node (Assign 'z (Mult 'y 'y)) 4)
+                 (set 'z)
+                 (Node (Equal 'x 'y) 5)
+                 (set 'y)
+                 (Node (Assign 'x 'z) 7)
+                 (set)
+                 (Node (Assign 'y 4) 1)
+                 (set 'y)
+                 (Node (NoOp) 6)
+                 (set 'z))))
\ No newline at end of file