CORE notes break optimisation
I think at some point we decided that Core notes shouldn't affect optimisation. Here is a case where they do:
module Foo where
foo :: Int -> Int
{-# INLINE [1] foo #-}
foo x = x+1
{-# RULES "foo/foo" forall x. foo (foo x) = x #-}
module Bar where
import Foo
bar :: Int -> Int -> Int
bar x y = foo ({-# CORE "note" #-} x `seq` foo y)
When compiled with -O2, the rule doesn't fire with the note but does fire without it. This is the Core with the note:
Bar.bar =
\ (x_aaw :: GHC.Types.Int) (y_aax :: GHC.Types.Int) ->
Foo.foo
(__core_note "note"
(case x_aaw of _ { GHC.Types.I# _ -> Foo.foo y_aax }))
For the rule to fire, GHC must move the seq to the outside but because of the note, it doesn't.
Trac metadata
Trac field | Value |
---|---|
Version | 7.1 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |