From 80f2726310c26f2efb64a8460352df19361130b0 Mon Sep 17 00:00:00 2001
From: Andy Wingo <wingo@pobox.com>
Date: Thu, 29 Oct 2015 14:50:59 +0000
Subject: [PATCH] Better f64 unboxing for loop vars that might flow to $ktail

* module/language/cps/specialize-numbers.scm (compute-specializable-f64-vars):
  Tweak to allow f64 values to flow directly to return sites.
---
 module/language/cps/specialize-numbers.scm | 20 +++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/module/language/cps/specialize-numbers.scm b/module/language/cps/specialize-numbers.scm
index 6d61f5b35..9aa803533 100644
--- a/module/language/cps/specialize-numbers.scm
+++ b/module/language/cps/specialize-numbers.scm
@@ -178,14 +178,20 @@
           (match exp
             (($ $primcall 'scm->f64 (var))
              (intset-add f64-uses var))
-            (($ $values (var))
+            (($ $values vars)
              (match (intmap-ref cps k)
-               (($ $kargs (_) (def))
-                (if (intset-ref f64-defs def)
-                    (intset-add f64-uses var)
-                    f64-uses))
-               ;; Could be $ktail.
-               (_ f64-uses)))
+               (($ $kargs _ defs)
+                (fold (lambda (var def f64-uses)
+                        (if (intset-ref f64-defs def)
+                            (intset-add f64-uses var)
+                            f64-uses))
+                      f64-uses vars defs))
+               (($ $ktail)
+                ;; Assume return is rare and that any f64-valued def can
+                ;; be reboxed when leaving the procedure.
+                (fold (lambda (var f64-uses)
+                        (intset-add f64-uses var))
+                      f64-uses vars))))
             (_ f64-uses)))
          (_ f64-uses)))
      body empty-intset))