[project @ 2001-09-26 15:12:33 by simonpj]

[ghc-hetmet.git] / ghc / compiler / typecheck / TcInstDcls.lhs

diff --git a/ghc/compiler/typecheck/TcInstDcls.lhs b/ghc/compiler/typecheck/TcInstDcls.lhs
index 540c92e..aef778a 100644 (file)
--- a/ghc/compiler/typecheck/TcInstDcls.lhs
+++ b/ghc/compiler/typecheck/TcInstDcls.lhs
@@ -58,7 +58,7 @@ import FunDeps                ( checkInstFDs )
 import Generics                ( validGenericInstanceType )
 import Module          ( Module, foldModuleEnv )
 import Name            ( getSrcLoc )
-import NameSet         ( unitNameSet, nameSetToList )
+import NameSet         ( unitNameSet, emptyNameSet, nameSetToList )
 import PrelInfo                ( eRROR_ID )
 import TyCon           ( TyCon )
 import Subst           ( mkTopTyVarSubst, substTheta )
@@ -610,11 +610,16 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id,
         dict_constr   = classDataCon clas
        scs_and_meths = map instToId (sc_dicts ++ meth_insts)
        this_dict_id  = instToId this_dict
-       inlines       = unitNameSet (idName dfun_id)
+       inlines       | null dfun_arg_dicts = emptyNameSet
+                     | otherwise           = unitNameSet (idName dfun_id)
                -- Always inline the dfun; this is an experimental decision
                -- because it makes a big performance difference sometimes.
                -- Often it means we can do the method selection, and then
                -- inline the method as well.  Marcin's idea; see comments below.
+               --
+               -- BUT: don't inline it if it's a constant dictionary;
+               -- we'll get all the benefit without inlining, and we get
+               -- a **lot** of code duplication if we inline it
 
        dict_rhs
          | null scs_and_meths
@@ -646,7 +651,7 @@ tcInstDecl2 (InstInfo { iDFunId = dfun_id,
          = AbsBinds
                 zonked_inst_tyvars
                 (map instToId dfun_arg_dicts)
-                [(inst_tyvars', dfun_id, this_dict_id)] 
+                [(inst_tyvars', local_dfun_id, this_dict_id)] 
                 inlines
                 (lie_binds1    `AndMonoBinds` 
                  lie_binds2    `AndMonoBinds`