Remove "use mask" from StgAlt syntax

Reviewers: austin, bgamari, simonpj

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1933

3 files changed, 8 insertions, 16 deletions

diff --git a/compiler/stgSyn/CoreToStg.hs b/compiler/stgSyn/CoreToStg.hs
index 414571cbf8..c275f4d4f3 100644
--- a/compiler/stgSyn/CoreToStg.hs
+++ b/compiler/stgSyn/CoreToStg.hs
@@ -413,18 +413,14 @@ coreToStgExpr (Case scrut bndr _ alts) = do
         -- where a nullary tuple is mapped to (State# World#)
         ASSERT( null binders )
         do { (rhs2, rhs_fvs, rhs_escs) <- coreToStgExpr rhs
-           ; return ((DEFAULT, [], [], rhs2), rhs_fvs, rhs_escs) }
+           ; return ((DEFAULT, [], rhs2), rhs_fvs, rhs_escs) }
       | otherwise
       = let     -- Remove type variables
             binders' = filterStgBinders binders
         in
         extendVarEnvLne [(b, LambdaBound) | b <- binders'] $ do
         (rhs2, rhs_fvs, rhs_escs) <- coreToStgExpr rhs
-        let
-                -- Records whether each param is used in the RHS
-            good_use_mask = [ b `elementOfFVInfo` rhs_fvs | b <- binders' ]
-
-        return ( (con, binders', good_use_mask, rhs2),
+        return ( (con, binders', rhs2),
                  binders' `minusFVBinders` rhs_fvs,
                  rhs_escs `delVarSetList` binders' )
                 -- ToDo: remove the delVarSet;
diff --git a/compiler/stgSyn/StgLint.hs b/compiler/stgSyn/StgLint.hs
index df3c4e57df..dd206d9e39 100644
--- a/compiler/stgSyn/StgLint.hs
+++ b/compiler/stgSyn/StgLint.hs
@@ -223,15 +223,15 @@ lintStgAlts alts scrut_ty = do
           -- We can't check that the alternatives have the
           -- same type, because they don't, with unsafeCoerce#
 
-lintAlt :: Type -> (AltCon, [Id], [Bool], StgExpr) -> LintM (Maybe Type)
-lintAlt _ (DEFAULT, _, _, rhs)
+lintAlt :: Type -> (AltCon, [Id], StgExpr) -> LintM (Maybe Type)
+lintAlt _ (DEFAULT, _, rhs)
  = lintStgExpr rhs
 
-lintAlt scrut_ty (LitAlt lit, _, _, rhs) = do
+lintAlt scrut_ty (LitAlt lit, _, rhs) = do
    checkTys (literalType lit) scrut_ty (mkAltMsg1 scrut_ty)
    lintStgExpr rhs
 
-lintAlt scrut_ty (DataAlt con, args, _, rhs) = do
+lintAlt scrut_ty (DataAlt con, args, rhs) = do
     case splitTyConApp_maybe scrut_ty of
       Just (tycon, tys_applied) | isAlgTyCon tycon &&
                                   not (isNewTyCon tycon) -> do
diff --git a/compiler/stgSyn/StgSyn.hs b/compiler/stgSyn/StgSyn.hs
index 1fc84125f9..4145d9e974 100644
--- a/compiler/stgSyn/StgSyn.hs
+++ b/compiler/stgSyn/StgSyn.hs
@@ -469,7 +469,7 @@ rhsHasCafRefs (StgRhsCon _ _ args)
   = any stgArgHasCafRefs args
 
 altHasCafRefs :: GenStgAlt bndr Id -> Bool
-altHasCafRefs (_, _, _, rhs) = exprHasCafRefs rhs
+altHasCafRefs (_, _, rhs) = exprHasCafRefs rhs
 
 stgArgHasCafRefs :: GenStgArg Id -> Bool
 stgArgHasCafRefs (StgVarArg id)
@@ -533,10 +533,6 @@ rather than from the scrutinee type.
 type GenStgAlt bndr occ
   = (AltCon,            -- alts: data constructor,
      [bndr],            -- constructor's parameters,
-     [Bool],            -- "use mask", same length as
-                        -- parameters; a True in a
-                        -- param's position if it is
-                        -- used in the ...
      GenStgExpr bndr occ)       -- ...right-hand side.
 
 data AltType
@@ -743,7 +739,7 @@ pprStgExpr (StgCase expr bndr alt_type alts)
 
 pprStgAlt :: (OutputableBndr bndr, Outputable occ, Ord occ)
           => GenStgAlt bndr occ -> SDoc
-pprStgAlt (con, params, _use_mask, expr)
+pprStgAlt (con, params, expr)
   = hang (hsep [ppr con, sep (map (pprBndr CaseBind) params), text "->"])
          4 (ppr expr <> semi)