[commit: integer-gmp] master: Add another gcdInteger rule (4b780b9)

Repository : ssh://darcs.haskell.org//srv/darcs/packages/integer-gmp

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/4b780b93beac863b7945d7e050ffa6cdaf256eb7

>---------------------------------------------------------------

commit 4b780b93beac863b7945d7e050ffa6cdaf256eb7
Author: Ian Lynagh <[email protected]>
Date:   Fri Jul 13 20:04:51 2012 +0100

    Add another gcdInteger rule
    
    This one is better when the result is converted to an Int

>---------------------------------------------------------------

 GHC/Integer/Type.lhs |   11 ++++++++---
 1 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/GHC/Integer/Type.lhs b/GHC/Integer/Type.lhs
index a402f37..b9d9c3c 100644
--- a/GHC/Integer/Type.lhs
+++ b/GHC/Integer/Type.lhs
@@ -283,9 +283,14 @@ lcmInteger a b =      if a `eqInteger` S# 0# then S# 0#
         ab = absInteger b
 
 -- This rule needs to use absInteger so that it works correctly when
--- the result is minBound :: Int
-{-# RULES "gcdInteger/Int" forall a b.
-    gcdInteger (smallInteger a) (smallInteger b) = absInteger (smallInteger (gcdInt a b))
+-- the result is minBound :: Int. But that isn't necessary when the
+-- result is converted to an Int.
+{-# RULES
+"gcdInteger/Int" forall a b.
+    gcdInteger (smallInteger a) (smallInteger b)
+        = absInteger (smallInteger (gcdInt a b))
+"integerToInt/gcdInteger/Int" forall a b.
+    integerToInt (gcdInteger (smallInteger a) (smallInteger b)) = gcdInt a b
   #-}
 gcdInt :: Int# -> Int# -> Int#
 gcdInt 0# y  = absInt y