From: Matt Birkholz <matt@birkholz.chandler.az.us>
Date: Wed, 7 Mar 2012 21:28:05 +0000 (-0700)
Subject: svm: Save a byte encoding (ea:stack-ref 0).
X-Git-Tag: release-9.2.0~276
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=9e637d1f9d27be47d9c9fffe4539f955d86b394f;p=mit-scheme.git

svm: Save a byte encoding (ea:stack-ref 0).
---

diff --git a/src/compiler/machines/svm/machine.scm b/src/compiler/machines/svm/machine.scm
index 146070529..976d1054b 100644
--- a/src/compiler/machines/svm/machine.scm
+++ b/src/compiler/machines/svm/machine.scm
@@ -222,7 +222,10 @@ USA.
   (ea:pre-decrement rref:stack-pointer 'WORD))
 
 (define (ea:stack-ref index)
-  (ea:offset rref:stack-pointer index 'WORD))
+  (guarantee-non-negative-fixnum index 'ea:stack-ref)
+  (if (zero? index)
+      (ea:indirect rref:stack-pointer)
+      (ea:offset rref:stack-pointer index 'WORD)))
 
 (define (ea:alloc-word)
   (ea:post-increment rref:free-pointer 'WORD))