From 10f01e82bbb29e88b9e86026ef1ff4e165d7f47b Mon Sep 17 00:00:00 2001
From: Justin Ethier <justin.ethier@gmail.com>
Date: Thu, 31 May 2018 13:34:51 -0400
Subject: [PATCH] WIP

---
 find-direct-rec-calls.scm | 27 +++++++++++++++++++++++++--
 1 file changed, 25 insertions(+), 2 deletions(-)

diff --git a/find-direct-rec-calls.scm b/find-direct-rec-calls.scm
index 9b843add..eaff6e62 100644
--- a/find-direct-rec-calls.scm
+++ b/find-direct-rec-calls.scm
@@ -1,3 +1,7 @@
+;; Instead of just porting this to cps-optmizations should consider
+;; creating a new subdirectory under scheme/cyclone/cps-optimizations and starting to place
+;; things like this there as new libraries, to isolate them, improve testability, and help
+;; make optimizations easiser to maintain
 (import
   (scheme base)
   (scheme cyclone ast)
@@ -8,10 +12,25 @@
 )
 
   (define (find-direct-recursive-calls exp)
+    (define (check-args args)
+      (define (check exp)
+        (cond
+          ((quote? exp) #t)
+          ((const? exp) #t)
+          ((ref? exp) #t)
+          ((app? exp)
+           (and 
+             ;; Very conservative right now
+             (member (car exp) '(car cdr))
+             (check-args (cdr exp))))
+          (else #f)))
+      (every check args))
+
     (define (scan exp def-sym)
       (write `(scan ,def-sym ,exp)) (newline)
       (cond
        ((ast:lambda? exp)
+        ;; Reject if there are nested functions
         #f)
        ((quote? exp) exp)
        ((const? exp) exp)
@@ -20,12 +39,16 @@
        ((define? exp) #f)
        ((set!? exp) #f)
        ((if? exp)       
-        (scan (if->condition exp) def-sym)
+        (scan (if->condition exp) def-sym) ;; OK to check??
         (scan (if->then exp) def-sym)
         (scan (if->else exp) def-sym))
        ((app? exp)
         (when (equal? (car exp) def-sym)
-          (write `(possible direct recursive call ,exp)))
+          (if (check-args (cddr exp)) ;; Skip func and continuation
+            (write `(direct recursive call ,exp))
+            (write `(not a direct recursive call ,exp))
+         )
+        )
        )
        (else #f)))
     (for-each