Add non-recursive let-bindings for types

[ghc-hetmet.git] / compiler / simplCore / Simplify.lhs

diff --git a/compiler/simplCore/Simplify.lhs b/compiler/simplCore/Simplify.lhs
index 249dae2..ada2e8f 100644 (file)
--- a/compiler/simplCore/Simplify.lhs
+++ b/compiler/simplCore/Simplify.lhs
@@ -864,14 +864,7 @@ simplLam :: SimplEnv -> [InId] -> InExpr -> SimplCont
 
 simplLam env [] body cont = simplExprF env body cont
 
-        -- Type-beta reduction
-simplLam env (bndr:bndrs) body (ApplyTo _ (Type ty_arg) arg_se cont)
-  = ASSERT( isTyVar bndr )
-    do  { tick (BetaReduction bndr)
-        ; ty_arg' <- simplType (arg_se `setInScope` env) ty_arg
-        ; simplLam (extendTvSubst env bndr ty_arg') bndrs body cont }
-
-        -- Ordinary beta reduction
+        -- Beta reduction
 simplLam env (bndr:bndrs) body (ApplyTo _ arg arg_se cont)
   = do  { tick (BetaReduction bndr)
         ; simplNonRecE env bndr (arg, arg_se) (bndrs, body) cont }
@@ -904,9 +897,11 @@ simplNonRecE :: SimplEnv
 -- Why?  Because of the binder-occ-info-zapping done before
 --       the call to simplLam in simplExprF (Lam ...)
 
-       -- First deal with type lets: let a = Type ty in b
+       -- First deal with type applications and type lets
+       --   (/\a. e) (Type ty)   and   (let a = Type ty in e)
 simplNonRecE env bndr (Type ty_arg, rhs_se) (bndrs, body) cont
-  = do { ty_arg' <- simplType (rhs_se `setInScope` env) ty_arg
+  = ASSERT( isTyVar bndr )
+    do { ty_arg' <- simplType (rhs_se `setInScope` env) ty_arg
        ; simplLam (extendTvSubst env bndr ty_arg') bndrs body cont }
 
 simplNonRecE env bndr (rhs, rhs_se) (bndrs, body) cont
@@ -1265,15 +1260,18 @@ inlined.
 
 Note [no-case-of-case]
 ~~~~~~~~~~~~~~~~~~~~~~
-There is a time we *don't* want to do that, namely when
--fno-case-of-case is on.  This happens in the first simplifier pass,
-and enhances full laziness.  Here's the bad case:
-        f = \ y -> ...(case x of I# v -> ...(case x of ...) ... )
-If we eliminate the inner case, we trap it inside the I# v -> arm,
-which might prevent some full laziness happening.  I've seen this
-in action in spectral/cichelli/Prog.hs:
-         [(m,n) | m <- [1..max], n <- [1..max]]
-Hence the check for NoCaseOfCase.
+We *used* to suppress the binder-swap in case expressoins when 
+-fno-case-of-case is on.  Old remarks:
+    "This happens in the first simplifier pass,
+    and enhances full laziness.  Here's the bad case:
+            f = \ y -> ...(case x of I# v -> ...(case x of ...) ... )
+    If we eliminate the inner case, we trap it inside the I# v -> arm,
+    which might prevent some full laziness happening.  I've seen this
+    in action in spectral/cichelli/Prog.hs:
+             [(m,n) | m <- [1..max], n <- [1..max]]
+    Hence the check for NoCaseOfCase."
+However, now the full-laziness pass itself reverses the binder-swap, so this
+check is no longer necessary.
 
 Note [Suppressing the case binder-swap]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1495,9 +1493,9 @@ simplCaseBinder env0 scrut0 case_bndr0 alts
 
 
     improve_case_bndr env scrut case_bndr
-        | switchIsOn (getSwitchChecker env) NoCaseOfCase
-                -- See Note [no-case-of-case]
-        = (env, case_bndr)
+        -- See Note [no-case-of-case]
+       --  | switchIsOn (getSwitchChecker env) NoCaseOfCase
+       --  = (env, case_bndr)
 
         | otherwise     -- Failed try; see Note [Suppressing the case binder-swap]
                         --     not (isEvaldUnfolding (idUnfolding v))