[commit: ghc] wip/nomeata-T2110: In CoreSubst, optimize Coercible values aggressively (9ce3aae)

[git at git.haskell.org]

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

On branch  : wip/nomeata-T2110
Link       : http://ghc.haskell.org/trac/ghc/changeset/9ce3aaed80324b473865397cffdabe215858e1c4/ghc

>---------------------------------------------------------------

commit 9ce3aaed80324b473865397cffdabe215858e1c4
Author: Joachim Breitner <mail at joachim-breitner.de>
Date:   Fri Jan 24 13:34:50 2014 +0000

    In CoreSubst, optimize Coercible values aggressively
    
    just like boxed type equalities.


>---------------------------------------------------------------

9ce3aaed80324b473865397cffdabe215858e1c4
 compiler/coreSyn/CoreSubst.lhs |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler/coreSyn/CoreSubst.lhs b/compiler/coreSyn/CoreSubst.lhs
index 3b39320..3dedbc8 100644
--- a/compiler/coreSyn/CoreSubst.lhs
+++ b/compiler/coreSyn/CoreSubst.lhs
@@ -61,7 +61,7 @@ import Coercion hiding ( substTy, substCo, extendTvSubst, substTyVarBndr, substC
 
 import TyCon       ( tyConArity )
 import DataCon
-import PrelNames   ( eqBoxDataConKey )
+import PrelNames   ( eqBoxDataConKey, coercibleDataConKey )
 import OptCoercion ( optCoercion )
 import PprCore     ( pprCoreBindings, pprRules )
 import Module	   ( Module )
@@ -1039,7 +1039,7 @@ maybe_substitute subst b r
     trivial | exprIsTrivial r = True
             | (Var fun, args) <- collectArgs r
             , Just dc <- isDataConWorkId_maybe fun
-            , dc `hasKey` eqBoxDataConKey
+            , dc `hasKey` eqBoxDataConKey || dc `hasKey` coercibleDataConKey
             , all exprIsTrivial args = True -- See Note [Optimise coercion boxes agressively]
             | otherwise = False