Comments

diff --git a/compiler/simplCore/Simplify.lhs b/compiler/simplCore/Simplify.lhs
index efd1b78..376c7b9 100644 (file)
--- a/compiler/simplCore/Simplify.lhs
+++ b/compiler/simplCore/Simplify.lhs
@@ -1123,18 +1123,10 @@ in action in spectral/cichelli/Prog.hs:
         [(m,n) | m <- [1..max], n <- [1..max]]
 Hence the check for NoCaseOfCase.
 
         [(m,n) | m <- [1..max], n <- [1..max]]
 Hence the check for NoCaseOfCase.
 

-Note [Case of cast]
-~~~~~~~~~~~~~~~~~~~
-Consider       case (v `cast` co) of x { I# ->
-               ... (case (v `cast` co) of {...}) ...
-We'd like to eliminate the inner case.  We can get this neatly by 
-arranging that inside the outer case we add the unfolding
-       v |-> x `cast` (sym co)
-to v.  Then we should inline v at the inner case, cancel the casts, and away we go
-       
-Note 2
-~~~~~~
-There is another situation when we don't want to do it.  If we have
+Note [Suppressing the case binder-swap]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+There is another situation when it might make sense to suppress the
+case-expression binde-swap. If we have

 
     case x of w1 { DEFAULT -> case x of w2 { A -> e1; B -> e2 }
                   ...other cases .... }
 
     case x of w1 { DEFAULT -> case x of w2 { A -> e1; B -> e2 }
                   ...other cases .... }

@@ -1196,6 +1188,15 @@ The point is that we bring into the envt a binding
 after the outer case, and that makes (a,b) alive.  At least we do unless
 the case binder is guaranteed dead.
 
 after the outer case, and that makes (a,b) alive.  At least we do unless
 the case binder is guaranteed dead.
 

+Note [Case of cast]
+~~~~~~~~~~~~~~~~~~~
+Consider       case (v `cast` co) of x { I# ->
+               ... (case (v `cast` co) of {...}) ...
+We'd like to eliminate the inner case.  We can get this neatly by 
+arranging that inside the outer case we add the unfolding
+       v |-> x `cast` (sym co)
+to v.  Then we should inline v at the inner case, cancel the casts, and away we go
+       

 \begin{code}
 simplCaseBinder :: SimplEnv -> OutExpr -> InId -> SimplM (SimplEnv, OutId)
 simplCaseBinder env scrut case_bndr
 \begin{code}
 simplCaseBinder :: SimplEnv -> OutExpr -> InId -> SimplM (SimplEnv, OutId)
 simplCaseBinder env scrut case_bndr