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$ cat Reduce3.hs 
module Reduce3
  where

foo = 1 + 2
$ cat Reduce4.hs 
module Reduce4
  where

foo = 3
$ ghc -c -O2 -fforce-recomp -ddump-simpl Reduce3.hs 

==================== Tidy Core ====================
Reduce3.lvl :: GHC.Num.Integer
[GlobalId]
[NoCafRefs]
Reduce3.lvl = GHC.Num.S# 1

Reduce3.lvl1 :: GHC.Num.Integer
[GlobalId]
[NoCafRefs]
Reduce3.lvl1 = GHC.Num.S# 2

Reduce3.foo :: GHC.Num.Integer
[GlobalId]
[Str: DmdType]
Reduce3.foo = GHC.Num.plusInteger Reduce3.lvl Reduce3.lvl1



==================== Tidy Core Rules ====================


$ ghc -c -O2 -fforce-recomp -ddump-simpl Reduce4.hs 

==================== Tidy Core ====================
Reduce4.foo :: GHC.Num.Integer
[GlobalId]
[NoCafRefs
 Str: DmdType]
Reduce4.foo = GHC.Num.S# 3




==================== Tidy Core Rules ====================

It would be nice if GHC could do the addition at compile time (since, after all, the result will always be the same) instead of at runtime.

Trac metadata

Trac field	Value
Version	6.8.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system	Unknown
Architecture	Unknown