From: Taylor R Campbell <campbell@mumble.net>
Date: Sun, 17 Oct 2010 02:01:19 +0000 (+0000)
Subject: Back out i386 rewriting rule to optimize OBJECT->FIXNUM operands.
X-Git-Tag: 20101212-Gtk~34
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=6741e538324f2ecea5d6ebeb28792f0e223c7e9f;p=mit-scheme.git

Back out i386 rewriting rule to optimize OBJECT->FIXNUM operands.

This causes conpar.scm, for example, to be miscompiled.
---

diff --git a/src/compiler/machines/i386/rulrew.scm b/src/compiler/machines/i386/rulrew.scm
index 1b2dc8d23..21acaaf54 100644
--- a/src/compiler/machines/i386/rulrew.scm
+++ b/src/compiler/machines/i386/rulrew.scm
@@ -150,6 +150,11 @@ USA.
   (QUALIFIER (rtl:constant-fixnum? source))
   (rtl:make-object->fixnum source))
 
+#|
+
+These are tempting, but there is a lapopt rule that makes
+OBJECT->FIXNUM not, after all, independent of the tag.
+
 (define-rule rewriting
   (OBJECT->FIXNUM (REGISTER (? source register-known-value)))
   (QUALIFIER (rtl:cons-non-pointer? source))
@@ -160,6 +165,8 @@ USA.
   (QUALIFIER (rtl:object->datum? source))
   (rtl:make-object->fixnum (rtl:object->datum-expression source)))
 
+|#
+
 (define-rule rewriting
   (FIXNUM-2-ARGS MULTIPLY-FIXNUM
 		 (REGISTER (? operand-1 register-known-value))
@@ -176,7 +183,7 @@ USA.
   (QUALIFIER
    (and (rtl:constant-fixnum-test operand-2 (lambda (n) n true))))
   (rtl:make-fixnum-2-args 'MULTIPLY-FIXNUM operand-1 operand-2 overflow?))
-
+
 (define-rule rewriting
   (FIXNUM-2-ARGS (? operator)
 		 (? operand-1)