bug#38486: hang

So I hacked modules/cps/optimize.scm to display the optimization phases.

Here is what I got up to the point where guile hangs.
It looks like it's hanging in specialize-numbers.

running eliminate-dead-code
running prune-top-level-scopes
running simplify
running contify
running inline-constructors
running elide-values
running prune-bailouts
running peel-loops
running eliminate-common-subexpressions
running type-fold
running resolve-self-references
running eliminate-dead-code
running simplify
running specialize-numbers

The patch:
--- module/language/cps/optimize.scm-orig    2020-03-21 
14:16:17.313452995 -0700
+++ module/language/cps/optimize.scm    2020-03-21 14:18:32.264770889 -0700
@@ -73,7 +73,10 @@
      (maybe-verify program)
      (set! program
        (if (kw-arg-ref opts kw default)
-          (maybe-verify (pass program))
+          (begin
+            (display "running ") (display (quote pass)) (newline)
+            (force-output (current-output-port))
+            (maybe-verify (pass program)))
            program))
      ...
      (maybe-verify program)))