From b682791b365d8ac84746ffa03b7d5f79b1a0b9a0 Mon Sep 17 00:00:00 2001
From: Chris Hanson <org/chris-hanson/cph>
Date: Mon, 22 Feb 1993 22:38:41 +0000
Subject: [PATCH] Handle case where REGISTER-LIVE-LENGTH of a register is zero.
  This can happen when a register is assigned but not referenced; ideally it
 would be best not to generate code like this but in at least one case it is
 hard to avoid.

---
 v7/src/compiler/rtlopt/ralloc.scm | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/v7/src/compiler/rtlopt/ralloc.scm b/v7/src/compiler/rtlopt/ralloc.scm
index e60218a8a..1f042a7f1 100644
--- a/v7/src/compiler/rtlopt/ralloc.scm
+++ b/v7/src/compiler/rtlopt/ralloc.scm
@@ -1,8 +1,8 @@
 #| -*-Scheme-*-
 
-$Header: /Users/cph/tmp/foo/mit-scheme/mit-scheme/v7/src/compiler/rtlopt/ralloc.scm,v 1.16 1988/09/07 06:25:33 cph Rel $
+$Id: ralloc.scm,v 1.17 1993/02/22 22:38:41 cph Exp $
 
-Copyright (c) 1988 Massachusetts Institute of Technology
+Copyright (c) 1988-93 Massachusetts Institute of Technology
 
 This material was developed by the Scheme project at the Massachusetts
 Institute of Technology, Department of Electrical Engineering and
@@ -130,8 +130,10 @@ MIT in each case. |#
 	next-allocation))))
 
 (define (allocate<? x y)
-  (< (/ (register-n-refs x) (register-live-length x))
-     (/ (register-n-refs y) (register-live-length y))))
+  (and (not (= (register-live-length x) 0))
+       (or (= (register-live-length y) 0)
+	   (< (/ (register-n-refs x) (register-live-length x))
+	      (/ (register-n-refs y) (register-live-length y))))))
 
 (define (mark-births! live rtl register->renumber)
   (if (rtl:assign? rtl)
-- 
2.25.1