+--------------------------------
+-- Top level function inlining
+--------------------------------
+-- This transformation inlines top level bindings that have been generated by
+-- the compiler and are really simple. Really simple currently means that the
+-- normalized form only contains a single binding, which catches most of the
+-- cases where a top level function is created that simply calls a type class
+-- method with a type and dictionary argument, e.g.
+-- fromInteger = GHC.Num.fromInteger (SizedWord D8) $dNum
+-- which is later called using simply
+-- fromInteger (smallInteger 10)
+-- By inlining such calls to simple, compiler generated functions, we prevent
+-- huge amounts of trivial components in the VHDL output, which the user never
+-- wanted. We never inline user-defined functions, since we want to preserve
+-- all structure defined by the user. Currently this includes all functions
+-- that were created by funextract, since we would get loops otherwise.
+--
+-- 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
+-- Any system name is candidate for inlining. Never inline user-defined
+-- functions, to preserve structure.
+inlinetoplevel 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
+
+
+-- Leave all other expressions unchanged
+inlinetoplevel expr = return expr
+inlinetopleveltop = everywhere ("inlinetoplevel", inlinetoplevel)
+
+-- | Does the given binder need to be inlined? If so, return the body to
+-- be used for inlining.
+needsInline :: CoreBndr -> TransformMonad (Maybe CoreExpr)
+needsInline f = do
+ body_maybe <- Trans.lift $ getGlobalBind f
+ case body_maybe of
+ -- No body available?
+ Nothing -> return Nothing
+ Just body -> case CoreSyn.collectArgs body of
+ -- The body is some (top level) binder applied to 0 or more
+ -- arguments. That should be simple enough to inline.
+ (Var f, args) -> return $ Just body
+ -- Body is more complicated, try normalizing it
+ _ -> do
+ norm_maybe <- Trans.lift $ getNormalized_maybe f
+ case norm_maybe of
+ -- Noth normalizeable
+ Nothing -> return Nothing
+ Just norm -> case splitNormalized norm of
+ -- The function has just a single binding, so that's simple
+ -- enough to inline.
+ (args, [bind], res) -> return $ Just norm
+ -- More complicated function, don't inline
+ _ -> return Nothing
+
+--------------------------------
+-- Dictionary inlining
+--------------------------------
+-- Inline all top level dictionaries, so we can use them to resolve
+-- class methods based on the dictionary passed.
+inlinedict expr@(Var f) | Id.isDictId f = do
+ body_maybe <- Trans.lift $ getGlobalBind f
+ case body_maybe of
+ Nothing -> return expr
+ Just body -> change body
+
+-- Leave all other expressions unchanged
+inlinedict expr = return expr
+inlinedicttop = everywhere ("inlinedict", inlinedict)
+
+--------------------------------
+-- ClassOp resolution
+--------------------------------
+-- Resolves any class operation to the actual operation whenever
+-- possible. Class methods (as well as parent dictionary selectors) are
+-- special "functions" that take a type and a dictionary and evaluate to
+-- the corresponding method. A dictionary is nothing more than a
+-- special dataconstructor applied to the type the dictionary is for,
+-- each of the superclasses and all of the class method definitions for
+-- that particular type. Since dictionaries all always inlined (top
+-- levels dictionaries are inlined by inlinedict, local dictionaries are
+-- inlined by inlinenonrep), we will eventually have something like:
+--
+-- baz
+-- @ CLasH.HardwareTypes.Bit
+-- (D:Baz @ CLasH.HardwareTypes.Bit bitbaz)
+--
+-- Here, baz is the method selector for the baz method, while
+-- D:Baz is the dictionary constructor for the Baz and bitbaz is the baz
+-- method defined in the Baz Bit instance declaration.
+--
+-- To resolve this, we can look at the ClassOp IdInfo from the baz Id,
+-- which contains the Class it is defined for. From the Class, we can
+-- get a list of all selectors (both parent class selectors as well as
+-- method selectors). Since the arguments to D:Baz (after the type
+-- argument) correspond exactly to this list, we then look up baz in
+-- that list and replace the entire expression by the corresponding
+-- argument to D:Baz.
+--
+-- We don't resolve methods that have a builtin translation (such as
+-- ==), since the actual implementation is not always (easily)
+-- translateable. For example, when deriving ==, GHC generates code
+-- using $con2tag functions to translate a datacon to an int and compare
+-- that with GHC.Prim.==# . Better to avoid that for now.
+classopresolution, classopresolutiontop :: Transform
+classopresolution expr@(App (App (Var sel) ty) dict) | not is_builtin =
+ case Id.isClassOpId_maybe sel of
+ -- Not a class op selector
+ Nothing -> return expr
+ Just cls -> case collectArgs dict of
+ (_, []) -> return expr -- Dict is not an application (e.g., not inlined yet)
+ (Var dictdc, (ty':selectors)) | not (Maybe.isJust (Id.isDataConId_maybe dictdc)) -> return expr -- Dictionary is not a datacon yet (but e.g., a top level binder)
+ | tyargs_neq ty ty' -> error $ "Applying class selector to dictionary without matching type?\n" ++ pprString expr
+ | otherwise ->
+ let selector_ids = Class.classSelIds cls in
+ -- Find the selector used in the class' list of selectors
+ case List.elemIndex sel selector_ids of
+ Nothing -> error $ "Selector not found in class' selector list? This should not happen!\nExpression: " ++ pprString expr ++ "\nClass: " ++ show cls ++ "\nSelectors: " ++ show selector_ids
+ -- Get the corresponding argument from the dictionary
+ Just n -> change (selectors!!n)
+ (_, _) -> return expr -- Not applying a variable? Don't touch
+ where
+ -- Compare two type arguments, returning True if they are _not_
+ -- equal
+ tyargs_neq (Type ty1) (Type ty2) = not $ Type.coreEqType ty1 ty2
+ tyargs_neq _ _ = True
+ -- Is this a builtin function / method?
+ is_builtin = elem (Name.getOccString sel) builtinIds
+
+-- Leave all other expressions unchanged
+classopresolution expr = return expr
+-- Perform this transform everywhere
+classopresolutiontop = everywhere ("classopresolution", classopresolution)
+
projects / matthijs / master-project / cλash.git / blobdiff