-- η abstraction
--------------------------------
eta, etatop :: Transform
+-- Don't apply to expressions that are applied, since that would cause
+-- us to apply to our own result indefinitely.
+eta (AppFirst:_) expr = return expr
+-- Also don't apply to arguments, since this can cause loops with
+-- funextract. This isn't the proper solution, but due to an
+-- implementation bug in notappargs, this is how it used to work so far.
+eta (AppSecond:_) expr = return expr
eta c expr | is_fun expr && not (is_lam expr) = do
let arg_ty = (fst . Type.splitFunTy . CoreUtils.exprType) expr
id <- Trans.lift $ mkInternalVar "param" arg_ty
change (Lam id (App expr (Var id)))
-- Leave all other expressions unchanged
eta c e = return e
-etatop = notappargs ("eta", eta)
+etatop = everywhere ("eta", eta)
--------------------------------
-- β-reduction
-- all structure defined by the user. Currently this includes all functions
-- that were created by funextract, since we would get loops otherwise.
--
+-- Only functions that are actually completely applied and bound by a
+-- variable in a let expression are inlined. These are the expressions
+-- that will eventually generate instantiations of trivial components.
+-- By not inlining any other reference, we also prevent looping problems
+-- with funextract and inlinedict.
+--
-- Note that "defined by the compiler" isn't completely watertight, since GHC
-- doesn't seem to set all those names as "system names", we apply some
-- guessing here.
inlinetoplevel, inlinetopleveltop :: Transform
--- HACK: Don't inline == and /=. The default (derived) implementation
--- for /= uses the polymorphic version of ==, which gets a dictionary
--- for Eq passed in, which contains a reference to itself, resulting in
--- an infinite loop in transformation. Not inlining == is really a hack,
--- but for now it keeps things working with the most common symptom of
--- this problem.
-inlinetoplevel c expr@(Var f) | Name.getOccString f `elem` ["==", "/="] = return expr
--- Any system name is candidate for inlining. Never inline user-defined
--- functions, to preserve structure.
-inlinetoplevel c expr@(Var f) | not $ isUserDefined f = do
- body_maybe <- needsInline f
- case body_maybe of
- Just body -> do
- -- Regenerate all uniques in the to-be-inlined expression
- body_uniqued <- Trans.lift $ genUniques body
- -- And replace the variable reference with the unique'd body.
- change body_uniqued
- -- No need to inline
- Nothing -> return expr
-
+inlinetoplevel (LetBinding:_) expr =
+ case collectArgs expr of
+ -- Any system name is candidate for inlining. Never inline
+ -- user-defined functions, to preserve structure.
+ (Var f, args) | not $ isUserDefined f -> do
+ body_maybe <- needsInline f
+ case body_maybe of
+ Just body -> do
+ -- Regenerate all uniques in the to-be-inlined expression
+ body_uniqued <- Trans.lift $ genUniques body
+ -- And replace the variable reference with the unique'd body.
+ change (mkApps body_uniqued args)
+ -- No need to inline
+ Nothing -> return expr
+ -- This is not an application of a binder, leave it unchanged.
+ _ -> return expr
-- Leave all other expressions unchanged
inlinetoplevel c expr = return expr
--------------------------------
-- Dictionary inlining
--------------------------------
--- Inline all top level dictionaries, so we can use them to resolve
--- class methods based on the dictionary passed.
-inlinedict c expr@(Var f) | Id.isDictId f = do
- body_maybe <- Trans.lift $ getGlobalBind f
+-- Inline all top level dictionaries, that are in a position where
+-- classopresolution can actually resolve them. This makes this
+-- transformation look similar to classoperesolution below, but we'll
+-- keep them separated for clarity. By not inlining other dictionaries,
+-- we prevent expression sizes exploding when huge type level integer
+-- dictionaries are inlined which can never be expanded (in casts, for
+-- example).
+inlinedict c expr@(App (App (Var sel) ty) (Var dict)) | not is_builtin && is_classop = do
+ body_maybe <- Trans.lift $ getGlobalBind dict
case body_maybe of
+ -- No body available (no source available, or a local variable /
+ -- argument)
Nothing -> return expr
- Just body -> change body
+ Just body -> change (App (App (Var sel) ty) body)
+ where
+ -- Is this a builtin function / method?
+ is_builtin = elem (Name.getOccString sel) builtinIds
+ -- Are we dealing with a class operation selector?
+ is_classop = Maybe.isJust (Id.isClassOpId_maybe sel)
-- Leave all other expressions unchanged
inlinedict c expr = return expr
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