[GHC] #14815: -XStrict prevents code inlining.

[GHC]

#14815: -XStrict prevents code inlining.
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           Reporter:  danilo2        |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  high           |         Milestone:
          Component:  Compiler       |           Version:  8.2.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
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 Hi, let's consider the following code:

 {{{

 {-# LANGUAGE Strict #-}  -- Comment/uncommenting this
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}

 module K where

 import Control.Monad.Trans
 import qualified Control.Monad.State.Strict as S
 import Control.Monad.Primitive

 newtype StateT s m a = StateT (S.StateT s m a) -- S is
 Control.Monad.State.Strict
   deriving (Functor, Applicative, Monad, MonadTrans)

 instance PrimMonad m => PrimMonad (StateT s m) where
   type PrimState (StateT s m) = PrimState m
   primitive ~a = lift (primitive a) ; {-# INLINE primitive #-}
 }}}

 If compiled with `-XStrict` this code is not inlined properly and it badly
 affects the performance. While discussing it on Haskell IRC `lyxia` helped
 very much with discovering the CORE differences. The lazy version has
 couple of things which the strict version is missing in form of
 `[InlPrag=INLINE (sat-args=0)]` on toplevel identifiers.

 Core: https://gist.github.com/Lysxia/34684c9ca9fe4772ea38a5065414f542

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14815>
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