[commit: ghc] master: Get eqTypeRep to inline (8529fbb)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/8529fbba309cd692bbbb0386321515d05a6ed256/ghc

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commit 8529fbba309cd692bbbb0386321515d05a6ed256
Author: David Feuer <david.feuer at gmail.com>
Date:   Thu Feb 15 03:48:51 2018 -0500

    Get eqTypeRep to inline
    
    GHC didn't inline `eqTypeRep`, presumably because it ended up
    being too big. This was unfortunate because it produces a
    `Maybe`, which will almost always be scrutinized immediately.
    
    Split `eqTypeRep` into a worker and a tiny wrapper, and mark the
    wrapper `INLINABLE`. This change actually seems to reduce Core size,
    at least in a small test.
    
    Reviewers: hvr, bgamari, mpickering
    
    Reviewed By: mpickering
    
    Subscribers: mpickering, rwbarton, thomie, carter
    
    GHC Trac Issues: #14790
    
    Differential Revision: https://phabricator.haskell.org/D4405


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8529fbba309cd692bbbb0386321515d05a6ed256
 libraries/base/Data/Typeable/Internal.hs | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/libraries/base/Data/Typeable/Internal.hs b/libraries/base/Data/Typeable/Internal.hs
index a01a9ff..6c52cc5 100644
--- a/libraries/base/Data/Typeable/Internal.hs
+++ b/libraries/base/Data/Typeable/Internal.hs
@@ -564,9 +564,17 @@ typeRepTyCon (TrFun {})               = typeRepTyCon $ typeRep @(->)
 eqTypeRep :: forall k1 k2 (a :: k1) (b :: k2).
              TypeRep a -> TypeRep b -> Maybe (a :~~: b)
 eqTypeRep a b
-  | typeRepFingerprint a == typeRepFingerprint b = Just (unsafeCoerce HRefl)
-  | otherwise                                    = Nothing
-
+  | sameTypeRep a b = Just (unsafeCoerce# HRefl)
+  | otherwise       = Nothing
+-- We want GHC to inline eqTypeRep to get rid of the Maybe
+-- in the usual case that it is scrutinized immediately. We
+-- split eqTypeRep into a worker and wrapper because otherwise
+-- it's much larger than anything we'd want to inline.
+{-# INLINABLE eqTypeRep #-}
+
+sameTypeRep :: forall k1 k2 (a :: k1) (b :: k2).
+               TypeRep a -> TypeRep b -> Bool
+sameTypeRep a b = typeRepFingerprint a == typeRepFingerprint b
 
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