From d53524208963df290a72327ff4118c1851bd9a61 Mon Sep 17 00:00:00 2001
From: Alex Smith <ais523@bham.ac.uk>
Date: Thu, 2 Sep 2010 23:35:24 +0100
Subject: [PATCH] Optimiser bugfix: loss of precision in bitshifts

---
 src/idiotism.oil | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/idiotism.oil b/src/idiotism.oil
index 68f76c6..ee21e5b 100644
--- a/src/idiotism.oil
+++ b/src/idiotism.oil
@@ -293,13 +293,16 @@
 [combinellshift]
 ((_1 << #{1}2) << #{1}3)->(_1 << #{x2+x3}0)
 [combinelrshift]
-((_1 << #{1}2) >> #{x>x2}3)->(_1 >> #{x3-x2}0)
-((_1 << #{1}2) >> #{x==x2}3)->(_1)
-((_1 << #{1}2) >> #{x<x2}3)->(_1 << #{x2-x3}0)
+((.{65535LU>>x2 >= c}1 << #{1}2) >> #{x>x2}3)->(.1 >> #{x3-x2}0)
+((.{65535LU>>x2 >= c}1 << #{1}2) >> #{x==x2}3)->(.1)
+((.{65535LU>>x2 >= c}1 << #{1}2) >> #{x<x2}3)->(.1 << #{x2-x3}0)
+((:{4294967295LU>>x2 >= c}1 << #{1}2) >> #{x>x2}3)->(:1 >> #{x3-x2}0)
+((:{4294967295LU>>x2 >= c}1 << #{1}2) >> #{x==x2}3)->(:1)
+((:{4294967295LU>>x2 >= c}1 << #{1}2) >> #{x<x2}3)->(:1 << #{x2-x3}0)
 [combinerlshift]
-((_1 >> #{1}2) << #{x>x2}3)->(_1 << #{x3-x2}0)
-((_1 >> #{1}2) << #{x==x2}3)->(_1)
-((_1 >> #{1}2) << #{x<x2}3)->(_1 >> #{x2-x3}0)
+((_{!(((1LU<<x2)-1)&c)}1 >> #{1}2) << #{x>x2}3)->(_1 << #{x3-x2}0)
+((_{!(((1LU<<x2)-1)&c)}1 >> #{1}2) << #{x==x2}3)->(_1)
+((_{!(((1LU<<x2)-1)&c)}1 >> #{1}2) << #{x<x2}3)->(_1 >> #{x2-x3}0)
 [combinerrshift]
 ((_1 >> #{1}2) >> #{1}3)->(_1 >> #{x2+x3}0)
 [nullshift]
-- 
2.43.0