Use UniqDSet for finding free names in the Linker

This is not necessary for determinism, but it's a choice
between making this deterministic and using `nonDetEltsUFM`
and a comment explaining that it doesn't matter.

Test Plan: ./validate

Reviewers: austin, hvr, bgamari, simonmar

Reviewed By: simonmar

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2295

GHC Trac Issues: #4012

2 files changed, 10 insertions, 8 deletions

diff --git a/compiler/ghci/ByteCodeAsm.hs b/compiler/ghci/ByteCodeAsm.hs
index f765a7d2f4..817e379003 100644
--- a/compiler/ghci/ByteCodeAsm.hs
+++ b/compiler/ghci/ByteCodeAsm.hs
@@ -34,6 +34,7 @@ import Outputable
 import Platform
 import Util
 import Unique
+import UniqDSet
 
 -- From iserv
 import SizedSeq
@@ -65,14 +66,14 @@ import qualified Data.Map as Map
 
 -- | Finds external references.  Remember to remove the names
 -- defined by this group of BCOs themselves
-bcoFreeNames :: UnlinkedBCO -> NameSet
+bcoFreeNames :: UnlinkedBCO -> UniqDSet Name
 bcoFreeNames bco
-  = bco_refs bco `minusNameSet` mkNameSet [unlinkedBCOName bco]
+  = bco_refs bco `uniqDSetMinusUniqSet` mkNameSet [unlinkedBCOName bco]
   where
     bco_refs (UnlinkedBCO _ _ _ _ nonptrs ptrs)
-        = unionNameSets (
-             mkNameSet [ n | BCOPtrName n <- ssElts ptrs ] :
-             mkNameSet [ n | BCONPtrItbl n <- ssElts nonptrs ] :
+        = unionManyUniqDSets (
+             mkUniqDSet [ n | BCOPtrName n <- ssElts ptrs ] :
+             mkUniqDSet [ n | BCONPtrItbl n <- ssElts nonptrs ] :
              map bco_refs [ bco | BCOPtrBCO bco <- ssElts ptrs ]
           )
 
diff --git a/compiler/ghci/Linker.hs b/compiler/ghci/Linker.hs
index 5042136ce3..0f15ea2877 100644
--- a/compiler/ghci/Linker.hs
+++ b/compiler/ghci/Linker.hs
@@ -37,7 +37,6 @@ import Finder
 import HscTypes
 import Name
 import NameEnv
-import NameSet
 import UniqFM
 import Module
 import ListSetOps
@@ -50,6 +49,7 @@ import ErrUtils
 import SrcLoc
 import qualified Maybes
 import UniqSet
+import UniqDSet
 import FastString
 import Platform
 import SysTools
@@ -504,7 +504,7 @@ linkExpr hsc_env span root_ul_bco
    ; return (pls, fhv)
    }}}
    where
-     free_names = nameSetElems (bcoFreeNames root_ul_bco)
+     free_names = uniqDSetToList (bcoFreeNames root_ul_bco)
 
      needed_mods :: [Module]
      needed_mods = [ nameModule n | n <- free_names,
@@ -730,7 +730,8 @@ linkDecls hsc_env span cbc@CompiledByteCode{..} = do
                    , itbl_env    = ie }
     return (pls2, ())
   where
-    free_names =  concatMap (nameSetElems . bcoFreeNames) bc_bcos
+    free_names = uniqDSetToList $
+      foldr (unionUniqDSets . bcoFreeNames) emptyUniqDSet bc_bcos
 
     needed_mods :: [Module]
     needed_mods = [ nameModule n | n <- free_names,