[Git][ghc/ghc][master] Make IOEnv monad one-shot (#18202)

[Marge Bot]

 Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
8a51b2ab by Sylvain Henry at 2020-08-13T21:09:15-04:00
Make IOEnv monad one-shot (#18202)

On CI (x86_64-linux-deb9-hadrian, compile_time/bytes_allocated):

    T10421     -1.8%    (threshold: +/- 1%)
    T10421a    -1.7%    (threshold: +/- 1%)
    T12150     -4.9%    (threshold: +/- 2%)
    T12227     -1.6     (threshold: +/- 1%)
    T12425     -1.5%    (threshold: +/- 1%)
    T12545     -3.8%    (threshold: +/- 1%)
    T12707     -3.0%    (threshold: +/- 1%)
    T13035     -3.0%    (threshold: +/- 1%)
    T14683     -10.3%   (threshold: +/- 2%)
    T3064      -6.9%    (threshold: +/- 2%)
    T4801      -4.3%    (threshold: +/- 2%)
    T5030      -2.6%    (threshold: +/- 2%)
    T5321FD    -3.6%    (threshold: +/- 2%)
    T5321Fun   -4.6%    (threshold: +/- 2%)
    T5631      -19.7%   (threshold: +/- 2%)
    T5642      -13.0%   (threshold: +/- 2%)
    T783       -2.7     (threshold: +/- 2%)
    T9020      -11.1    (threshold: +/- 2%)
    T9961      -3.4%    (threshold: +/- 2%)

    T1969 (compile_time/bytes_allocated)  -2.2%  (threshold: +/-1%)
    T1969 (compile_time/max_bytes_used)   +24.4% (threshold: +/-20%)

Additionally on other CIs:

    haddock.Cabal                  -10.0%   (threshold: +/- 5%)
    haddock.compiler               -9.5%    (threshold: +/- 5%)
    haddock.base (max bytes used)  +24.6%   (threshold: +/- 15%)
    T10370 (max bytes used, i386)  +18.4%   (threshold: +/- 15%)

Metric Decrease:
    T10421
    T10421a
    T12150
    T12227
    T12425
    T12545
    T12707
    T13035
    T14683
    T3064
    T4801
    T5030
    T5321FD
    T5321Fun
    T5631
    T5642
    T783
    T9020
    T9961
    haddock.Cabal
    haddock.compiler
Metric Decrease 'compile_time/bytes allocated':
    T1969
Metric Increase 'compile_time/max_bytes_used':
    T1969
    T10370
    haddock.base

- - - - -


1 changed file:

- compiler/GHC/Data/IOEnv.hs


Changes:

=====================================
compiler/GHC/Data/IOEnv.hs
=====================================
@@ -1,6 +1,7 @@
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DerivingVia #-}
+{-# LANGUAGE PatternSynonyms #-}
 --
 -- (c) The University of Glasgow 2002-2006
 --
@@ -48,16 +49,25 @@ import Control.Monad.Trans.Reader
 import Control.Monad.Catch (MonadCatch, MonadMask, MonadThrow)
 import GHC.Utils.Monad
 import Control.Applicative (Alternative(..))
+import GHC.Exts( oneShot )
 
 ----------------------------------------------------------------------
 -- Defining the monad type
 ----------------------------------------------------------------------
 
 
-newtype IOEnv env a = IOEnv (env -> IO a)
+newtype IOEnv env a = IOEnv' (env -> IO a)
   deriving (Functor)
   deriving (MonadThrow, MonadCatch, MonadMask, MonadIO) via (ReaderT env IO)
 
+-- See Note [The one-shot state monad trick] in GHC.Utils.Monad
+pattern IOEnv :: forall env a. (env -> IO a) -> IOEnv env a
+pattern IOEnv m <- IOEnv' m
+  where
+    IOEnv m = IOEnv' (oneShot m)
+
+{-# COMPLETE IOEnv #-}
+
 unIOEnv :: IOEnv env a -> (env -> IO a)
 unIOEnv (IOEnv m) = m
 



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/8a51b2ab7433c06bddca9699b0dfd8ab1d11879b

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/8a51b2ab7433c06bddca9699b0dfd8ab1d11879b
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