From: Paul Khuong <pvk@pvk.ca>
Date: Wed, 22 May 2013 03:43:03 +0000 (-0400)
Subject: Simplify (- (- x)) for rationals
X-Git-Url: http://repo.macrolet.net/gitweb/?a=commitdiff_plain;h=11dc847696f9c5441c409ce5b7fdf77cf27746c5;p=sbcl.git

Simplify (- (- x)) for rationals

 The transform is trivial enough to execute without a real pattern
 matching framework, but we're close to the limit.
---

diff --git a/src/compiler/srctran.lisp b/src/compiler/srctran.lisp
index 0d22154..ff0a51c 100644
--- a/src/compiler/srctran.lisp
+++ b/src/compiler/srctran.lisp
@@ -3344,6 +3344,11 @@
   "convert (* x 0) to 0"
   0)
 
+(deftransform %negate ((x) (rational))
+  "Eliminate %negate/%negate of rationals"
+  (splice-fun-args x '%negate 1)
+  '(the rational x))
+
 ;;; Return T if in an arithmetic op including lvars X and Y, the
 ;;; result type is not affected by the type of X. That is, Y is at
 ;;; least as contagious as X.