- fixed how stack overflow check is performed (now using unsigned

arithmetic to compare the stack pointer with the redline).
- disabled stack overflow check elimination due to a bug in the
  logic that assumes primitive calls are not recursive.

scheme/ikarus.compiler.altcogen.ss

@@ -276,11 +276,11 @@
       [(funcall rator arg*)       #t]
       [(jmpcall label rator arg*) #t]
       [(mvcall rator k)           #t] 
+      [(primcall op arg*)     #t] ;;; (ormap A arg*)] PUNT!!! FIXME!
       [(bind lhs* rhs* body)  (or (ormap NonTail rhs*) (NonTail body))]
       [(fix lhs* rhs* body)   (NonTail body)]
       [(conditional e0 e1 e2) (or (NonTail e0) (NonTail e1) (NonTail e2))]
       [(seq e0 e1)            (or (NonTail e0) (NonTail e1))]
-      [(primcall op arg*)     (ormap A arg*)]
       [(forcall op arg*)      (ormap NonTail arg*)]
       [(known x t v) (NonTail x)]
       [else (error who "invalid expr" x)]))

scheme/pass-specify-rep-primops.ss

@@ -2339,7 +2339,7 @@
   [(E) 
    (make-shortcut 
      (make-conditional 
-       (make-primcall '< 
+       (make-primcall 'u< 
          (list esp (make-primcall 'mref
                      (list pcr (make-constant pcb-frame-redline)))))
        (make-primcall 'interrupt '())