import CLasH.Utils.Core.BinderTools
import CLasH.Utils.Pretty
---------------------------------
--- Start of transformations
---------------------------------
-
---------------------------------
--- η expansion
---------------------------------
--- Make sure all parameters to the normalized functions are named by top
--- level lambda expressions. For this we apply η expansion to the
--- function body (possibly enclosed in some lambda abstractions) while
--- it has a function type. Eventually this will result in a function
--- body consisting of a bunch of nested lambdas containing a
--- non-function value (e.g., a complete application).
-eta :: Transform
-eta c expr | is_fun expr && not (is_lam expr) && all (== LambdaBody) c = 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
+----------------------------------------------------------------
+-- Cleanup transformations
+----------------------------------------------------------------
--------------------------------
-- β-reduction
beta c expr = return expr
--------------------------------
--- Application propagation
+-- Unused let binding removal
--------------------------------
-appprop :: Transform
--- Propagate the application into the let
-appprop c (App (Let binds expr) arg) = change $ Let binds (App expr arg)
--- Propagate the application into each of the alternatives
-appprop c (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
- where
- alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
- ty' = CoreUtils.applyTypeToArg ty arg
+letremoveunused :: Transform
+letremoveunused c expr@(Let (NonRec b bound) res) = do
+ let used = expr_uses_binders [b] res
+ if used
+ then return expr
+ else change res
+letremoveunused c expr@(Let (Rec binds) res) = do
+ -- Filter out all unused binds.
+ let binds' = filter dobind binds
+ -- Only set the changed flag if binds got removed
+ changeif (length binds' /= length binds) (Let (Rec binds') res)
+ where
+ bound_exprs = map snd binds
+ -- For each bind check if the bind is used by res or any of the bound
+ -- expressions
+ dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
-- Leave all other expressions unchanged
-appprop c expr = return expr
+letremoveunused c expr = return expr
--------------------------------
--- Case of known constructor simplification
+-- empty let removal
--------------------------------
--- If a case expressions scrutinizes a datacon application, we can
--- determine which alternative to use and remove the case alltogether.
--- We replace it with a let expression the binds every binder in the
--- alternative bound to the corresponding argument of the datacon. We do
--- this instead of substituting the binders, to prevent duplication of
--- work and preserve sharing wherever appropriate.
-knowncase :: Transform
-knowncase context expr@(Case scrut@(App _ _) bndr ty alts) | not bndr_used = do
- case collectArgs scrut of
- (Var f, args) -> case Id.isDataConId_maybe f of
- -- Not a dataconstructor? Don't change anything (probably a
- -- function, then)
- Nothing -> return expr
- Just dc -> do
- let (altcon, bndrs, res) = case List.find (\(altcon, bndrs, res) -> altcon == (DataAlt dc)) alts of
- Just alt -> alt -- Return the alternative found
- Nothing -> head alts -- If the datacon is not present, the first must be the default alternative
- -- Double check if we have either the correct alternative, or
- -- the default.
- if altcon /= (DataAlt dc) && altcon /= DEFAULT then error ("Normalize.knowncase: Invalid core, datacon not found in alternatives and DEFAULT alternative is not first? " ++ pprString expr) else return ()
- -- Find out how many arguments to drop (type variables and
- -- predicates like dictionaries).
- let (tvs, preds, _, _) = DataCon.dataConSig dc
- let count = length tvs + length preds
- -- Create a let expression that binds each of the binders in
- -- this alternative to the corresponding argument of the data
- -- constructor.
- let binds = zip bndrs (drop count args)
- change $ Let (Rec binds) res
- _ -> return expr -- Scrutinee is not an application of a var
- where
- is_used (_, _, expr) = expr_uses_binders [bndr] expr
- bndr_used = or $ map is_used alts
-
+-- Remove empty (recursive) lets
+letremove :: Transform
+letremove c (Let (Rec []) res) = change res
-- Leave all other expressions unchanged
-knowncase c expr = return expr
+letremove c expr = return expr
+
+--------------------------------
+-- Simple let binding removal
+--------------------------------
+-- Remove a = b bindings from let expressions everywhere
+letremovesimple :: Transform
+letremovesimple = inlinebind (\(b, e) -> Trans.lift $ is_local_var e)
--------------------------------
-- Cast propagation
-- Leave all other expressions unchanged
castsimpl c expr = return expr
---------------------------------
--- Return value simplification
---------------------------------
--- Ensure the return value of a function follows proper normal form. eta
--- expansion ensures the body starts with lambda abstractions, this
--- transformation ensures that the lambda abstractions always contain a
--- recursive let and that, when the return value is representable, the
--- let contains a local variable reference in its body.
-retvalsimpl c expr | all (== LambdaBody) c && not (is_lam expr) && not (is_let expr) = do
- local_var <- Trans.lift $ is_local_var expr
- repr <- isRepr expr
- if not local_var && repr
- then do
- id <- Trans.lift $ mkBinderFor expr "res"
- change $ Let (Rec [(id, expr)]) (Var id)
- else
- return expr
-
-retvalsimpl c expr@(Let (Rec binds) body) | all (== LambdaBody) c = do
- -- Don't extract values that are already a local variable, to prevent
- -- loops with ourselves.
- local_var <- Trans.lift $ is_local_var body
- -- Don't extract values that are not representable, to prevent loops with
- -- inlinenonrep
- repr <- isRepr body
- if not local_var && repr
- then do
- id <- Trans.lift $ mkBinderFor body "res"
- change $ Let (Rec ((id, body):binds)) (Var id)
- else
- return expr
-
-
--- Leave all other expressions unchanged
-retvalsimpl c expr = return expr
-
---------------------------------
--- let derecursification
---------------------------------
-letrec :: Transform
-letrec c expr@(Let (NonRec bndr val) res) =
- change $ Let (Rec [(bndr, val)]) res
-
--- Leave all other expressions unchanged
-letrec c expr = return expr
-
---------------------------------
--- let flattening
---------------------------------
--- Takes a let that binds another let, and turns that into two nested lets.
--- e.g., from:
--- let b = (let b' = expr' in res') in res
--- to:
--- let b' = expr' in (let b = res' in res)
-letflat :: Transform
--- Turn a nonrec let that binds a let into two nested lets.
-letflat c (Let (NonRec b (Let binds res')) res) =
- change $ Let binds (Let (NonRec b res') res)
-letflat c (Let (Rec binds) expr) = do
- -- Flatten each binding.
- binds' <- Utils.concatM $ Monad.mapM flatbind binds
- -- Return the new let. We don't use change here, since possibly nothing has
- -- changed. If anything has changed, flatbind has already flagged that
- -- change.
- return $ Let (Rec binds') expr
- where
- -- Turns a binding of a let into a multiple bindings, or any other binding
- -- into a list with just that binding
- flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
- flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
- flatbind (b, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')]
- flatbind (b, expr) = return [(b, expr)]
--- Leave all other expressions unchanged
-letflat c expr = return expr
-
---------------------------------
--- empty let removal
---------------------------------
--- Remove empty (recursive) lets
-letremove :: Transform
-letremove c (Let (Rec []) res) = change res
--- Leave all other expressions unchanged
-letremove c expr = return expr
-
---------------------------------
--- Simple let binding removal
---------------------------------
--- Remove a = b bindings from let expressions everywhere
-letremovesimple :: Transform
-letremovesimple = inlinebind (\(b, e) -> Trans.lift $ is_local_var e)
-
---------------------------------
--- Unused let binding removal
---------------------------------
-letremoveunused :: Transform
-letremoveunused c expr@(Let (NonRec b bound) res) = do
- let used = expr_uses_binders [b] res
- if used
- then return expr
- else change res
-letremoveunused c expr@(Let (Rec binds) res) = do
- -- Filter out all unused binds.
- let binds' = filter dobind binds
- -- Only set the changed flag if binds got removed
- changeif (length binds' /= length binds) (Let (Rec binds') res)
- where
- bound_exprs = map snd binds
- -- For each bind check if the bind is used by res or any of the bound
- -- expressions
- dobind (bndr, _) = any (expr_uses_binders [bndr]) (res:bound_exprs)
--- Leave all other expressions unchanged
-letremoveunused c expr = return expr
-
-{-
---------------------------------
--- Identical let binding merging
---------------------------------
--- Merge two bindings in a let if they are identical
--- TODO: We would very much like to use GHC's CSE module for this, but that
--- doesn't track if something changed or not, so we can't use it properly.
-letmerge :: Transform
-letmerge c expr@(Let _ _) = do
- let (binds, res) = flattenLets expr
- binds' <- domerge binds
- return $ mkNonRecLets binds' res
- where
- domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
- domerge [] = return []
- domerge (e:es) = do
- es' <- mapM (mergebinds e) es
- es'' <- domerge es'
- return (e:es'')
-
- -- Uses the second bind to simplify the second bind, if applicable.
- mergebinds :: (CoreBndr, CoreExpr) -> (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
- mergebinds (b1, e1) (b2, e2)
- -- Identical expressions? Replace the second binding with a reference to
- -- the first binder.
- | CoreUtils.cheapEqExpr e1 e2 = change $ (b2, Var b1)
- -- Different expressions? Don't change
- | otherwise = return (b2, e2)
--- Leave all other expressions unchanged
-letmerge c expr = return expr
--}
-
---------------------------------
--- Non-representable binding inlining
---------------------------------
--- Remove a = B bindings, with B of a non-representable type, from let
--- expressions everywhere. This means that any value that we can't generate a
--- signal for, will be inlined and hopefully turned into something we can
--- represent.
---
--- This is a tricky function, which is prone to create loops in the
--- transformations. To fix this, we make sure that no transformation will
--- create a new let binding with a non-representable type. These other
--- transformations will just not work on those function-typed values at first,
--- but the other transformations (in particular β-reduction) should make sure
--- that the type of those values eventually becomes representable.
-inlinenonrep :: Transform
-inlinenonrep = inlinebind ((Monad.liftM not) . isRepr . snd)
-
--------------------------------
-- Top level function inlining
--------------------------------
-- More complicated function, don't inline
_ -> return Nothing
+
+----------------------------------------------------------------
+-- Program structure transformations
+----------------------------------------------------------------
+
--------------------------------
--- Dictionary inlining
+-- η expansion
--------------------------------
--- 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 (App (App (Var sel) ty) body)
+-- Make sure all parameters to the normalized functions are named by top
+-- level lambda expressions. For this we apply η expansion to the
+-- function body (possibly enclosed in some lambda abstractions) while
+-- it has a function type. Eventually this will result in a function
+-- body consisting of a bunch of nested lambdas containing a
+-- non-function value (e.g., a complete application).
+eta :: Transform
+eta c expr | is_fun expr && not (is_lam expr) && all (== LambdaBody) c = 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
+
+--------------------------------
+-- Application propagation
+--------------------------------
+-- Move applications into let and case expressions.
+appprop :: Transform
+-- Propagate the application into the let
+appprop c (App (Let binds expr) arg) = change $ Let binds (App expr arg)
+-- Propagate the application into each of the alternatives
+appprop c (App (Case scrut b ty alts) arg) = change $ Case scrut b ty' alts'
+ where
+ alts' = map (\(con, bndrs, expr) -> (con, bndrs, (App expr arg))) alts
+ ty' = CoreUtils.applyTypeToArg ty arg
+-- Leave all other expressions unchanged
+appprop c expr = return expr
+
+--------------------------------
+-- Let recursification
+--------------------------------
+-- Make all lets recursive, so other transformations don't need to
+-- handle non-recursive lets
+letrec :: Transform
+letrec c expr@(Let (NonRec bndr val) res) =
+ change $ Let (Rec [(bndr, val)]) res
+
+-- Leave all other expressions unchanged
+letrec c expr = return expr
+
+--------------------------------
+-- let flattening
+--------------------------------
+-- Takes a let that binds another let, and turns that into two nested lets.
+-- e.g., from:
+-- let b = (let b' = expr' in res') in res
+-- to:
+-- let b' = expr' in (let b = res' in res)
+letflat :: Transform
+-- Turn a nonrec let that binds a let into two nested lets.
+letflat c (Let (NonRec b (Let binds res')) res) =
+ change $ Let binds (Let (NonRec b res') res)
+letflat c (Let (Rec binds) expr) = do
+ -- Flatten each binding.
+ binds' <- Utils.concatM $ Monad.mapM flatbind binds
+ -- Return the new let. We don't use change here, since possibly nothing has
+ -- changed. If anything has changed, flatbind has already flagged that
+ -- change.
+ return $ Let (Rec binds') expr
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)
+ -- Turns a binding of a let into a multiple bindings, or any other binding
+ -- into a list with just that binding
+ flatbind :: (CoreBndr, CoreExpr) -> TransformMonad [(CoreBndr, CoreExpr)]
+ flatbind (b, Let (Rec binds) expr) = change ((b, expr):binds)
+ flatbind (b, Let (NonRec b' expr') expr) = change [(b, expr), (b', expr')]
+ flatbind (b, expr) = return [(b, expr)]
+-- Leave all other expressions unchanged
+letflat c expr = return expr
+
+--------------------------------
+-- Return value simplification
+--------------------------------
+-- Ensure the return value of a function follows proper normal form. eta
+-- expansion ensures the body starts with lambda abstractions, this
+-- transformation ensures that the lambda abstractions always contain a
+-- recursive let and that, when the return value is representable, the
+-- let contains a local variable reference in its body.
+
+-- Extract the return value from the body of the top level lambdas (of
+-- which ther could be zero), unless it is a let expression (in which
+-- case the next clause applies).
+retvalsimpl c expr | all (== LambdaBody) c && not (is_lam expr) && not (is_let expr) = do
+ local_var <- Trans.lift $ is_local_var expr
+ repr <- isRepr expr
+ if not local_var && repr
+ then do
+ id <- Trans.lift $ mkBinderFor expr "res"
+ change $ Let (Rec [(id, expr)]) (Var id)
+ else
+ return expr
+-- Extract the return value from the body of a let expression, which is
+-- itself the body of the top level lambdas (of which there could be
+-- zero).
+retvalsimpl c expr@(Let (Rec binds) body) | all (== LambdaBody) c = do
+ -- Don't extract values that are already a local variable, to prevent
+ -- loops with ourselves.
+ local_var <- Trans.lift $ is_local_var body
+ -- Don't extract values that are not representable, to prevent loops with
+ -- inlinenonrep
+ repr <- isRepr body
+ if not local_var && repr
+ then do
+ id <- Trans.lift $ mkBinderFor body "res"
+ change $ Let (Rec ((id, body):binds)) (Var id)
+ else
+ return expr
+-- Leave all other expressions unchanged
+retvalsimpl c expr = return expr
+--------------------------------
+-- Representable arguments simplification
+--------------------------------
+-- Make sure that all arguments of a representable type are simple variables.
+appsimpl :: Transform
+-- Simplify all representable arguments. Do this by introducing a new Let
+-- that binds the argument and passing the new binder in the application.
+appsimpl c expr@(App f arg) = do
+ -- Check runtime representability
+ repr <- isRepr arg
+ local_var <- Trans.lift $ is_local_var arg
+ if repr && not local_var
+ then do -- Extract representable arguments
+ id <- Trans.lift $ mkBinderFor arg "arg"
+ change $ Let (NonRec id arg) (App f (Var id))
+ else -- Leave non-representable arguments unchanged
+ return expr
-- Leave all other expressions unchanged
-inlinedict c expr = return expr
+appsimpl c expr = return expr
+
+----------------------------------------------------------------
+-- Built-in function transformations
+----------------------------------------------------------------
--------------------------------
--- ClassOp resolution
+-- Function-typed argument extraction
--------------------------------
--- 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 :: Transform
-classopresolution c 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 $ "Normalize.classopresolution: 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 $ "Normalize.classopresolution: 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
+-- This transform takes any function-typed argument that cannot be propagated
+-- (because the function that is applied to it is a builtin function), and
+-- puts it in a brand new top level binder. This allows us to for example
+-- apply map to a lambda expression This will not conflict with inlinenonrep,
+-- since that only inlines local let bindings, not top level bindings.
+funextract :: Transform
+funextract c expr@(App _ _) | is_var fexpr = do
+ body_maybe <- Trans.lift $ getGlobalBind f
+ case body_maybe of
+ -- We don't have a function body for f, so we can perform this transform.
+ Nothing -> do
+ -- Find the new arguments
+ args' <- mapM doarg args
+ -- And update the arguments. We use return instead of changed, so the
+ -- changed flag doesn't get set if none of the args got changed.
+ return $ MkCore.mkCoreApps fexpr args'
+ -- We have a function body for f, leave this application to funprop
+ Just _ -> return expr
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
+ -- Find the function called and the arguments
+ (fexpr, args) = collectArgs expr
+ Var f = fexpr
+ -- Change any arguments that have a function type, but are not simple yet
+ -- (ie, a variable or application). This means to create a new function
+ -- for map (\f -> ...) b, but not for map (foo a) b.
+ --
+ -- We could use is_applicable here instead of is_fun, but I think
+ -- arguments to functions could only have forall typing when existential
+ -- typing is enabled. Not sure, though.
+ doarg arg | not (is_simple arg) && is_fun arg = do
+ -- Create a new top level binding that binds the argument. Its body will
+ -- be extended with lambda expressions, to take any free variables used
+ -- by the argument expression.
+ let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
+ let body = MkCore.mkCoreLams free_vars arg
+ id <- Trans.lift $ mkBinderFor body "fun"
+ Trans.lift $ addGlobalBind id body
+ -- Replace the argument with a reference to the new function, applied to
+ -- all vars it uses.
+ change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
+ -- Leave all other arguments untouched
+ doarg arg = return arg
-- Leave all other expressions unchanged
-classopresolution c expr = return expr
+funextract c expr = return expr
+
+
+
+
+----------------------------------------------------------------
+-- Case normalization transformations
+----------------------------------------------------------------
--------------------------------
-- Scrutinee simplification
--------------------------------
+-- Make sure the scrutinee of a case expression is a local variable
+-- reference.
scrutsimpl :: Transform
-- Don't touch scrutinees that are already simple
scrutsimpl c expr@(Case (Var _) _ _ _) = return expr
scrutbndrremove c expr = return expr
--------------------------------
--- Case binder wildening
+-- Case normalization
--------------------------------
+-- Turn a case expression with any number of alternatives with any
+-- number of non-wild binders into as set of case and let expressions,
+-- all of which are in normal form (e.g., a bunch of extractor case
+-- expressions to extract all fields from the scrutinee, a number of let
+-- bindings to bind each alternative and a single selector case to
+-- select the right value.
casesimpl :: Transform
-- This is already a selector case (or, if x does not appear in bndrs, a very
-- simple case statement that will be removed by caseremove below). Just leave
caseremove c expr = return expr
--------------------------------
--- Argument extraction
+-- Case of known constructor simplification
--------------------------------
--- Make sure that all arguments of a representable type are simple variables.
-appsimpl :: Transform
--- Simplify all representable arguments. Do this by introducing a new Let
--- that binds the argument and passing the new binder in the application.
-appsimpl c expr@(App f arg) = do
- -- Check runtime representability
- repr <- isRepr arg
- local_var <- Trans.lift $ is_local_var arg
- if repr && not local_var
- then do -- Extract representable arguments
- id <- Trans.lift $ mkBinderFor arg "arg"
- change $ Let (NonRec id arg) (App f (Var id))
- else -- Leave non-representable arguments unchanged
- return expr
+-- If a case expressions scrutinizes a datacon application, we can
+-- determine which alternative to use and remove the case alltogether.
+-- We replace it with a let expression the binds every binder in the
+-- alternative bound to the corresponding argument of the datacon. We do
+-- this instead of substituting the binders, to prevent duplication of
+-- work and preserve sharing wherever appropriate.
+knowncase :: Transform
+knowncase context expr@(Case scrut@(App _ _) bndr ty alts) | not bndr_used = do
+ case collectArgs scrut of
+ (Var f, args) -> case Id.isDataConId_maybe f of
+ -- Not a dataconstructor? Don't change anything (probably a
+ -- function, then)
+ Nothing -> return expr
+ Just dc -> do
+ let (altcon, bndrs, res) = case List.find (\(altcon, bndrs, res) -> altcon == (DataAlt dc)) alts of
+ Just alt -> alt -- Return the alternative found
+ Nothing -> head alts -- If the datacon is not present, the first must be the default alternative
+ -- Double check if we have either the correct alternative, or
+ -- the default.
+ if altcon /= (DataAlt dc) && altcon /= DEFAULT then error ("Normalize.knowncase: Invalid core, datacon not found in alternatives and DEFAULT alternative is not first? " ++ pprString expr) else return ()
+ -- Find out how many arguments to drop (type variables and
+ -- predicates like dictionaries).
+ let (tvs, preds, _, _) = DataCon.dataConSig dc
+ let count = length tvs + length preds
+ -- Create a let expression that binds each of the binders in
+ -- this alternative to the corresponding argument of the data
+ -- constructor.
+ let binds = zip bndrs (drop count args)
+ change $ Let (Rec binds) res
+ _ -> return expr -- Scrutinee is not an application of a var
+ where
+ is_used (_, _, expr) = expr_uses_binders [bndr] expr
+ bndr_used = or $ map is_used alts
+
-- Leave all other expressions unchanged
-appsimpl c expr = return expr
+knowncase c expr = return expr
+
+
+
+
+----------------------------------------------------------------
+-- Unrepresentable value removal transformations
+----------------------------------------------------------------
+
+--------------------------------
+-- Non-representable binding inlining
+--------------------------------
+-- Remove a = B bindings, with B of a non-representable type, from let
+-- expressions everywhere. This means that any value that we can't generate a
+-- signal for, will be inlined and hopefully turned into something we can
+-- represent.
+--
+-- This is a tricky function, which is prone to create loops in the
+-- transformations. To fix this, we make sure that no transformation will
+-- create a new let binding with a non-representable type. These other
+-- transformations will just not work on those function-typed values at first,
+-- but the other transformations (in particular β-reduction) should make sure
+-- that the type of those values eventually becomes representable.
+inlinenonrep :: Transform
+inlinenonrep = inlinebind ((Monad.liftM not) . isRepr . snd)
--------------------------------
--- Function-typed argument propagation
+-- Function specialization
--------------------------------
--- Remove all applications to function-typed arguments, by duplication the
--- function called with the function-typed parameter replaced by the free
+-- Remove all applications to non-representable arguments, by duplicating the
+-- function called with the non-representable parameter replaced by the free
-- variables of the argument passed in.
argprop :: Transform
-- Transform any application of a named function (i.e., skip applications of
-- Leave all other expressions unchanged
inlinenonrepresult c expr = return expr
+--------------------------------
+-- 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 :: Transform
+classopresolution c 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 $ "Normalize.classopresolution: 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 $ "Normalize.classopresolution: 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 c expr = return expr
--------------------------------
--- Function-typed argument extraction
+-- Dictionary inlining
--------------------------------
--- This transform takes any function-typed argument that cannot be propagated
--- (because the function that is applied to it is a builtin function), and
--- puts it in a brand new top level binder. This allows us to for example
--- apply map to a lambda expression This will not conflict with inlinenonrep,
--- since that only inlines local let bindings, not top level bindings.
-funextract :: Transform
-funextract c expr@(App _ _) | is_var fexpr = 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
- -- We don't have a function body for f, so we can perform this transform.
- Nothing -> do
- -- Find the new arguments
- args' <- mapM doarg args
- -- And update the arguments. We use return instead of changed, so the
- -- changed flag doesn't get set if none of the args got changed.
- return $ MkCore.mkCoreApps fexpr args'
- -- We have a function body for f, leave this application to funprop
- Just _ -> return expr
+ -- No body available (no source available, or a local variable /
+ -- argument)
+ Nothing -> return expr
+ Just body -> change (App (App (Var sel) ty) body)
where
- -- Find the function called and the arguments
- (fexpr, args) = collectArgs expr
- Var f = fexpr
- -- Change any arguments that have a function type, but are not simple yet
- -- (ie, a variable or application). This means to create a new function
- -- for map (\f -> ...) b, but not for map (foo a) b.
- --
- -- We could use is_applicable here instead of is_fun, but I think
- -- arguments to functions could only have forall typing when existential
- -- typing is enabled. Not sure, though.
- doarg arg | not (is_simple arg) && is_fun arg = do
- -- Create a new top level binding that binds the argument. Its body will
- -- be extended with lambda expressions, to take any free variables used
- -- by the argument expression.
- let free_vars = VarSet.varSetElems $ CoreFVs.exprFreeVars arg
- let body = MkCore.mkCoreLams free_vars arg
- id <- Trans.lift $ mkBinderFor body "fun"
- Trans.lift $ addGlobalBind id body
- -- Replace the argument with a reference to the new function, applied to
- -- all vars it uses.
- change $ MkCore.mkCoreApps (Var id) (map Var free_vars)
- -- Leave all other arguments untouched
- doarg arg = return arg
+ -- 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
-funextract c expr = return expr
+inlinedict c expr = return expr
+
+
+{-
+--------------------------------
+-- Identical let binding merging
+--------------------------------
+-- Merge two bindings in a let if they are identical
+-- TODO: We would very much like to use GHC's CSE module for this, but that
+-- doesn't track if something changed or not, so we can't use it properly.
+letmerge :: Transform
+letmerge c expr@(Let _ _) = do
+ let (binds, res) = flattenLets expr
+ binds' <- domerge binds
+ return $ mkNonRecLets binds' res
+ where
+ domerge :: [(CoreBndr, CoreExpr)] -> TransformMonad [(CoreBndr, CoreExpr)]
+ domerge [] = return []
+ domerge (e:es) = do
+ es' <- mapM (mergebinds e) es
+ es'' <- domerge es'
+ return (e:es'')
+
+ -- Uses the second bind to simplify the second bind, if applicable.
+ mergebinds :: (CoreBndr, CoreExpr) -> (CoreBndr, CoreExpr) -> TransformMonad (CoreBndr, CoreExpr)
+ mergebinds (b1, e1) (b2, e2)
+ -- Identical expressions? Replace the second binding with a reference to
+ -- the first binder.
+ | CoreUtils.cheapEqExpr e1 e2 = change $ (b2, Var b1)
+ -- Different expressions? Don't change
+ | otherwise = return (b2, e2)
+-- Leave all other expressions unchanged
+letmerge c expr = return expr
+-}
--------------------------------
-- End of transformations
projects / matthijs / master-project / cλash.git / commitdiff