Add a note about primop wrappers (cf Trac #1509)

[ghc-hetmet.git] / compiler / basicTypes / Id.lhs

diff --git a/compiler/basicTypes/Id.lhs b/compiler/basicTypes/Id.lhs
index e2e991a..7ae75da 100644 (file)
--- a/compiler/basicTypes/Id.lhs
+++ b/compiler/basicTypes/Id.lhs
@@ -5,6 +5,13 @@
 \section[Id]{@Ids@: Value and constructor identifiers}
 
 \begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
+-- for details
+
 module Id (
        Id, DictId,
 
@@ -282,7 +289,7 @@ isDictId id = isDictTy (idType id)
 -- them at the CorePrep stage. 
 -- EXCEPT: unboxed tuples, which definitely have no binding
 hasNoBinding id = case globalIdDetails id of
-                       PrimOpId _       -> True
+                       PrimOpId _       -> True        -- See Note [Primop wrappers]
                        FCallId _        -> True
                        DataConWorkId dc -> isUnboxedTupleCon dc
                        other            -> False
@@ -309,6 +316,21 @@ idIsFrom :: Module -> Id -> Bool
 idIsFrom mod id = nameIsLocalOrFrom mod (idName id)
 \end{code}
 
+Note [Primop wrappers]
+~~~~~~~~~~~~~~~~~~~~~~
+Currently hasNoBinding claims that PrimOpIds don't have a curried
+function definition.  But actually they do, in GHC.PrimopWrappers,
+which is auto-generated from prelude/primops.txt.pp.  So actually, hasNoBinding
+could return 'False' for PrimOpIds.
+
+But we'd need to add something in CoreToStg to swizzle any unsaturated
+applications of GHC.Prim.plusInt# to GHC.PrimopWrappers.plusInt#.
+
+Nota Bene: GHC.PrimopWrappers is needed *regardless*, because it's
+used by GHCi, which does not implement primops direct at all.
+
+
+
 \begin{code}
 isDeadBinder :: Id -> Bool
 isDeadBinder bndr | isId bndr = isDeadOcc (idOccInfo bndr)