From: Max Bolingbroke Date: Thu, 31 Jul 2008 05:29:41 +0000 (+0000) Subject: Document CoreSyn and expand its API X-Git-Tag: 2008-09-12~261 X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=c168c43449a92bd1c4588d41807d963d491b8588 Document CoreSyn and expand its API --- diff --git a/compiler/coreSyn/CoreSyn.lhs b/compiler/coreSyn/CoreSyn.lhs index ea22eb5..e259591 100644 --- a/compiler/coreSyn/CoreSyn.lhs +++ b/compiler/coreSyn/CoreSyn.lhs @@ -3,46 +3,65 @@ % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998 % -CoreSyn: A data type for the Haskell compiler midsection - \begin{code} + +-- | CoreSyn holds all the main data types for use by for the Glasgow Haskell Compiler midsection module CoreSyn ( + -- * Main data types Expr(..), Alt, Bind(..), AltCon(..), Arg, Note(..), CoreExpr, CoreAlt, CoreBind, CoreArg, CoreBndr, TaggedExpr, TaggedAlt, TaggedBind, TaggedArg, TaggedBndr(..), - mkLets, mkLams, - mkApps, mkTyApps, mkValApps, mkVarApps, - mkLit, mkIntLitInt, mkIntLit, - mkConApp, mkCast, + -- ** 'Expr' construction + mkLets, mkLams, + mkApps, mkTyApps, mkVarApps, + + mkIntLit, mkIntLitInt, + mkWordLit, mkWordLitWord, + mkCharLit, mkStringLit, + mkFloatLit, mkFloatLitFloat, + mkDoubleLit, mkDoubleLitDouble, + + mkConApp, mkTyBind, varToCoreExpr, varsToCoreExprs, - isTyVar, isId, cmpAltCon, cmpAlt, ltAlt, + isTyVar, isId, cmpAltCon, cmpAlt, ltAlt, + + -- ** Simple 'Expr' access functions and predicates bindersOf, bindersOfBinds, rhssOfBind, rhssOfAlts, collectBinders, collectTyBinders, collectValBinders, collectTyAndValBinders, - collectArgs, coreExprCc, - mkTyBind, flattenBinds, + collectArgs, coreExprCc, flattenBinds, isValArg, isTypeArg, valArgCount, valBndrCount, isRuntimeArg, isRuntimeVar, - -- Unfoldings + -- * Unfolding data types Unfolding(..), UnfoldingGuidance(..), -- Both abstract everywhere but in CoreUnfold.lhs + + -- ** Constructing 'Unfolding's noUnfolding, evaldUnfolding, mkOtherCon, + + -- ** Predicates and deconstruction on 'Unfolding' unfoldingTemplate, maybeUnfoldingTemplate, otherCons, isValueUnfolding, isEvaldUnfolding, isCheapUnfolding, isCompulsoryUnfolding, hasUnfolding, hasSomeUnfolding, neverUnfold, - -- Seq stuff + -- * Strictness seqExpr, seqExprs, seqUnfolding, - -- Annotated expressions - AnnExpr, AnnExpr'(..), AnnBind(..), AnnAlt, + -- * Annotated expression data types + AnnExpr, AnnExpr'(..), AnnBind(..), AnnAlt, + + -- ** Operations on annotations deAnnotate, deAnnotate', deAnnAlt, collectAnnBndrs, - -- Core rules + -- * Core rule data types CoreRule(..), -- CoreSubst, CoreTidy, CoreFVs, PprCore only - RuleName, seqRules, ruleArity, - isBuiltinRule, ruleName, isLocalRule, ruleIdName, setRuleIdName + RuleName, + + -- ** Operations on 'CoreRule's + seqRules, ruleArity, ruleName, ruleIdName, ruleActivation_maybe, + setRuleIdName, + isBuiltinRule, isLocalRule ) where #include "HsVersions.h" @@ -60,7 +79,9 @@ import FastString import Outputable import Util -infixl 4 `mkApps`, `mkValApps`, `mkTyApps`, `mkVarApps` +import Data.Word + +infixl 4 `mkApps`, `mkTyApps`, `mkVarApps` -- Left associative, so that we can say (f `mkTyApps` xs `mkVarApps` ys) \end{code} @@ -75,79 +96,166 @@ These data types are the heart of the compiler \begin{code} infixl 8 `App` -- App brackets to the left -data Expr b -- "b" for the type of binders, - = Var Id - | Lit Literal - | App (Expr b) (Arg b) -- See Note [CoreSyn let/app invariant] - | Lam b (Expr b) - | Let (Bind b) (Expr b) -- See [CoreSyn let/app invariant], - -- and [CoreSyn letrec invariant] - | Case (Expr b) b Type [Alt b] -- Binder gets bound to value of scrutinee - -- See Note [CoreSyn case invariants] - | Cast (Expr b) Coercion - | Note Note (Expr b) - | Type Type -- This should only show up at the top - -- level of an Arg - -type Arg b = Expr b -- Can be a Type - -type Alt b = (AltCon, [b], Expr b) -- (DEFAULT, [], rhs) is the default alternative - -data AltCon = DataAlt DataCon -- Invariant: the DataCon is always from - -- a *data* type, and never from a *newtype* - | LitAlt Literal - | DEFAULT +-- | This is the data type that represents GHCs core intermediate language. Currently +-- GHC uses System FC for this purpose, +-- which is closely related to the simpler and better known System F . +-- +-- We get from Haskell source to this Core language in a number of stages: +-- +-- 1. The source code is parsed into an abstract syntax tree, which is represented +-- by the data type 'HsExpr.HsExpr' with the names being 'RdrName.RdrNames' +-- +-- 2. This syntax tree is /renamed/, which attaches a 'Unique.Unique' to every 'RdrName.RdrName' +-- (yielding a 'Name.Name') to disambiguate identifiers which are lexically identical. +-- For example, this program: +-- +-- @ +-- f x = let f x = x + 1 +-- in f (x - 2) +-- @ +-- +-- Would be renamed by having 'Unique's attached so it looked something like this: +-- +-- @ +-- f_1 x_2 = let f_3 x_4 = x_4 + 1 +-- in f_3 (x_2 - 2) +-- @ +-- +-- 3. The resulting syntax tree undergoes type checking (which also deals with instantiating +-- type class arguments) to yield a 'HsExpr.HsExpr' type that has 'Id.Id' as it's names. +-- +-- 4. Finally the syntax tree is /desugared/ from the expressive 'HsExpr.HsExpr' type into +-- this 'Expr' type, which has far fewer constructors and hence is easier to perform +-- optimization, analysis and code generation on. +-- +-- The type parameter @b@ is for the type of binders in the expression tree. +data Expr b + = Var Id -- ^ Variables + | Lit Literal -- ^ Primitive literals + | App (Expr b) (Arg b) -- ^ Applications: note that the argument may be a 'Type'. + -- + -- See "CoreSyn#let_app_invariant" for another invariant + | Lam b (Expr b) -- ^ Lambda abstraction + | Let (Bind b) (Expr b) -- ^ Recursive and non recursive @let@s. Operationally + -- this corresponds to allocating a thunk for the things + -- bound and then executing the sub-expression. + -- + -- #top_level_invariant# + -- #letrec_invariant# + -- + -- The right hand sides of all top-level and recursive @let@s + -- /must/ be of lifted type (see "Type#type_classification" for + -- the meaning of /lifted/ vs. /unlifted/). + -- + -- #let_app_invariant# + -- The right hand side of of a non-recursive 'Let' _and_ the argument of an 'App', + -- /may/ be of unlifted type, but only if the expression + -- is ok-for-speculation. This means that the let can be floated around + -- without difficulty. For example, this is OK: + -- + -- > y::Int# = x +# 1# + -- + -- But this is not, as it may affect termination if the expression is floated out: + -- + -- > y::Int# = fac 4# + -- + -- In this situation you should use @case@ rather than a @let@. The function + -- 'CoreUtils.needsCaseBinding' can help you determine which to generate, or + -- alternatively use 'MkCore.mkCoreLet' rather than this constructor directly, + -- which will generate a @case@ if necessary + -- + -- #type_let# + -- We allow a /non-recursive/ let to bind a type variable, thus: + -- + -- > Let (NonRec tv (Type ty)) body + -- + -- This can be very convenient for postponing type substitutions until + -- the next run of the simplifier. + -- + -- At the moment, the rest of the compiler only deals with type-let + -- in a Let expression, rather than at top level. We may want to revist + -- this choice. + | Case (Expr b) b Type [Alt b] -- ^ Case split. Operationally this corresponds to evaluating + -- the scrutinee (expression examined) to weak head normal form + -- and then examining at most one level of resulting constructor (i.e. you + -- cannot do nested pattern matching directly with this). + -- + -- The binder gets bound to the value of the scrutinee, + -- and the 'Type' must be that of all the case alternatives + -- + -- #case_invariants# + -- This is one of the more complicated elements of the Core language, and comes + -- with a number of restrictions: + -- + -- The 'DEFAULT' case alternative must be first in the list, if it occurs at all. + -- + -- The remaining cases are in order of increasing + -- tag (for 'DataAlts') or + -- lit (for 'LitAlts'). + -- This makes finding the relevant constructor easy, and makes comparison easier too. + -- + -- The list of alternatives must be exhaustive. An /exhaustive/ case + -- does not necessarily mention all constructors: + -- + -- @ + -- data Foo = Red | Green | Blue + -- + -- ... case x of + -- Red -> True + -- other -> f (case x of + -- Green -> ... + -- Blue -> ... ) ... + -- @ + -- + -- The inner case does not need a @Red@ alternative, because @x@ can't be @Red@ at + -- that program point. + | Cast (Expr b) Coercion -- ^ Cast an expression to a particular type. This is used to implement @newtype@s + -- (a @newtype@ constructor or destructor just becomes a 'Cast' in Core) and GADTs. + | Note Note (Expr b) -- ^ Notes. These allow general information to be + -- added to expressions in the syntax tree + | Type Type -- ^ A type: this should only show up at the top + -- level of an Arg + +-- | Type synonym for expressions that occur in function argument positions. +-- Only 'Arg' should contain a 'Type' at top level, general 'Expr' should not +type Arg b = Expr b + +-- | A case split alternative. Consists of the constructor leading to the alternative, +-- the variables bound from the constructor, and the expression to be executed given that binding. +-- The default alternative is @(DEFAULT, [], rhs)@ +type Alt b = (AltCon, [b], Expr b) + +-- | A case alternative constructor (i.e. pattern match) +data AltCon = DataAlt DataCon -- ^ A plain data constructor: @case e of { Foo x -> ... }@. + -- Invariant: the 'DataCon' is always from a @data@ type, and never from a @newtype@ + | LitAlt Literal -- ^ A literal: @case e of { 1 -> ... }@ + | DEFAULT -- ^ Trivial alternative: @case e of { _ -> ... }@ deriving (Eq, Ord) - +-- | Binding, used for top level bindings in a module and local bindings in a @let@. data Bind b = NonRec b (Expr b) - | Rec [(b, (Expr b))] + | Rec [(b, (Expr b))] \end{code} -------------------------- CoreSyn INVARIANTS --------------------------- Note [CoreSyn top-level invariant] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -* The RHSs of all top-level lets must be of LIFTED type. +See #toplevel_invariant# Note [CoreSyn letrec invariant] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -* The RHS of a letrec must be of LIFTED type. +See #letrec_invariant# Note [CoreSyn let/app invariant] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -* The RHS of a non-recursive let, *and* the argument of an App, - may be of UNLIFTED type, but only if the expression - is ok-for-speculation. This means that the let can be floated around - without difficulty. e.g. - y::Int# = x +# 1# ok - y::Int# = fac 4# not ok [use case instead] -This is intially enforced by DsUtils.mkDsLet and mkDsApp +See #let_app_invariant# + +This is intially enforced by DsUtils.mkCoreLet and mkCoreApp Note [CoreSyn case invariants] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Invariant: The DEFAULT case must be *first*, if it occurs at all - -Invariant: The remaining cases are in order of increasing - tag (for DataAlts) - lit (for LitAlts) - This makes finding the relevant constructor easy, - and makes comparison easier too - -Invariant: The list of alternatives is ALWAYS EXHAUSTIVE, - meaning that it covers all cases that can occur - - An "exhaustive" case does not necessarily mention all constructors: - data Foo = Red | Green | Blue - - ...case x of - Red -> True - other -> f (case x of - Green -> ... - Blue -> ... ) - The inner case does not need a Red alternative, because x can't be Red at - that program point. - +See #case_invariants# Note [CoreSyn let goal] ~~~~~~~~~~~~~~~~~~~~~~~ @@ -158,23 +266,18 @@ Note [CoreSyn let goal] Note [Type let] ~~~~~~~~~~~~~~~ -We allow a *non-recursive* let to bind a type variable, thus - Let (NonRec tv (Type ty)) body -This can be very convenient for postponing type substitutions until -the next run of the simplifier. - -At the moment, the rest of the compiler only deals with type-let -in a Let expression, rather than at top level. We may want to revist -this choice. +See #type_let# \begin{code} + +-- | Allows attaching extra information to points in expressions rather than e.g. identifiers. data Note - = SCC CostCentre + = SCC CostCentre -- ^ A cost centre annotation for profiling - | InlineMe -- Instructs simplifer to treat the enclosed expression + | InlineMe -- ^ Instructs the core simplifer to treat the enclosed expression -- as very small, and inline it at its call sites - | CoreNote String -- A generic core annotation, propagated but not used by GHC + | CoreNote String -- ^ A generic core annotation, propagated but not used by GHC -- NOTE: we also treat expressions wrapped in InlineMe as -- 'cheap' and 'dupable' (in the sense of exprIsCheap, exprIsDupable) @@ -197,58 +300,62 @@ data Note The CoreRule type and its friends are dealt with mainly in CoreRules, but CoreFVs, Subst, PprCore, CoreTidy also inspect the representation. -A Rule is - - "local" if the function it is a rule for is defined in the - same module as the rule itself. - - "orphan" if nothing on the LHS is defined in the same module - as the rule itself - \begin{code} +-- | A 'CoreRule' is: +-- +-- * \"Local\" if the function it is a rule for is defined in the +-- same module as the rule itself. +-- +-- * \"Orphan\" if nothing on the LHS is defined in the same module +-- as the rule itself data CoreRule = Rule { - ru_name :: RuleName, - ru_act :: Activation, -- When the rule is active + ru_name :: RuleName, -- ^ Name of the rule, for communication with the user + ru_act :: Activation, -- ^ When the rule is active -- Rough-matching stuff -- see comments with InstEnv.Instance( is_cls, is_rough ) - ru_fn :: Name, -- Name of the Id at the head of this rule - ru_rough :: [Maybe Name], -- Name at the head of each argument + ru_fn :: Name, -- ^ Name of the 'Id.Id' at the head of this rule + ru_rough :: [Maybe Name], -- ^ Name at the head of each argument to the left hand side -- Proper-matching stuff -- see comments with InstEnv.Instance( is_tvs, is_tys ) - ru_bndrs :: [CoreBndr], -- Forall'd variables - ru_args :: [CoreExpr], -- LHS args + ru_bndrs :: [CoreBndr], -- ^ Variables quantified over + ru_args :: [CoreExpr], -- ^ Left hand side arguments -- And the right-hand side - ru_rhs :: CoreExpr, + ru_rhs :: CoreExpr, -- ^ Right hand side of the rule -- Locality - ru_local :: Bool -- The fn at the head of the rule is + ru_local :: Bool -- ^ @True@ iff the fn at the head of the rule is -- defined in the same module as the rule - -- and is not an implicit Id (like a record sel - -- class op, or data con) + -- and is not an implicit 'Id' (like a record selector, + -- class operation, or data constructor) + -- NB: ru_local is *not* used to decide orphan-hood -- c.g. MkIface.coreRuleToIfaceRule } - | BuiltinRule { -- Built-in rules are used for constant folding - ru_name :: RuleName, -- and suchlike. It has no free variables. - ru_fn :: Name, -- Name of the Id at - -- the head of this rule - ru_nargs :: Int, -- Number of args that ru_try expects, - -- including type args - ru_try :: [CoreExpr] -> Maybe CoreExpr } - -- This function does the rewrite. It given too many - -- arguments, it simply discards them; the returned CoreExpr - -- is just the rewrite of ru_fn applied to the first ru_nargs args + -- | Built-in rules are used for constant folding + -- and suchlike. They have no free variables. + | BuiltinRule { + ru_name :: RuleName, -- ^ As above + ru_fn :: Name, -- ^ As above + ru_nargs :: Int, -- ^ Number of arguments that 'ru_try' expects, + -- including type arguments + ru_try :: [CoreExpr] -> Maybe CoreExpr + -- ^ This function does the rewrite. It given too many + -- arguments, it simply discards them; the returned 'CoreExpr' + -- is just the rewrite of 'ru_fn' applied to the first 'ru_nargs' args + } -- See Note [Extra args in rule matching] in Rules.lhs isBuiltinRule :: CoreRule -> Bool isBuiltinRule (BuiltinRule {}) = True isBuiltinRule _ = False +-- | The number of arguments the 'ru_fn' must be applied +-- to before the rule can match on it ruleArity :: CoreRule -> Int ruleArity (BuiltinRule {ru_nargs = n}) = n ruleArity (Rule {ru_args = args}) = length args @@ -256,12 +363,18 @@ ruleArity (Rule {ru_args = args}) = length args ruleName :: CoreRule -> RuleName ruleName = ru_name +ruleActivation_maybe :: CoreRule -> Maybe Activation +ruleActivation_maybe (BuiltinRule { }) = Nothing +ruleActivation_maybe (Rule { ru_act = act }) = Just act + +-- | The 'Name' of the 'Id.Id' at the head of the rule left hand side ruleIdName :: CoreRule -> Name ruleIdName = ru_fn isLocalRule :: CoreRule -> Bool isLocalRule = ru_local +-- | Set the 'Name' of the 'Id.Id' at the head of the rule left hand side setRuleIdName :: Name -> CoreRule -> CoreRule setRuleIdName nm ru = ru { ru_fn = nm } \end{code} @@ -273,35 +386,50 @@ setRuleIdName nm ru = ru { ru_fn = nm } %* * %************************************************************************ -The @Unfolding@ type is declared here to avoid numerous loops, but it -should be abstract everywhere except in CoreUnfold.lhs +The @Unfolding@ type is declared here to avoid numerous loops \begin{code} +-- | Records the /unfolding/ of an identifier, which is approximately the form the +-- identifier would have if we substituted its definition in for the identifier. +-- This type should be treated as abstract everywhere except in "CoreUnfold" data Unfolding - = NoUnfolding + = NoUnfolding -- ^ We have no information about the unfolding - | OtherCon [AltCon] -- It ain't one of these - -- (OtherCon xs) also indicates that something has been evaluated + | OtherCon [AltCon] -- ^ It ain't one of these constructors. + -- @OtherCon xs@ also indicates that something has been evaluated -- and hence there's no point in re-evaluating it. - -- OtherCon [] is used even for non-data-type values + -- @OtherCon []@ is used even for non-data-type values -- to indicated evaluated-ness. Notably: - -- data C = C !(Int -> Int) - -- case x of { C f -> ... } - -- Here, f gets an OtherCon [] unfolding. + -- + -- > data C = C !(Int -> Int) + -- > case x of { C f -> ... } + -- + -- Here, @f@ gets an @OtherCon []@ unfolding. - | CompulsoryUnfolding CoreExpr -- There is no "original" definition, + | CompulsoryUnfolding CoreExpr -- ^ There is /no original definition/, -- so you'd better unfold. - | CoreUnfolding -- An unfolding with redundant cached information - CoreExpr -- Template; binder-info is correct - Bool -- True <=> top level binding - Bool -- exprIsHNF template (cached); it is ok to discard a `seq` on - -- this variable - Bool -- True <=> doesn't waste (much) work to expand inside an inlining - -- Basically it's exprIsCheap - UnfoldingGuidance -- Tells about the *size* of the template. - - + | CoreUnfolding + CoreExpr + Bool + Bool + Bool + UnfoldingGuidance + -- ^ An unfolding with redundant cached information. Parameters: + -- + -- 1) Template used to perform unfolding; binder-info is correct + -- + -- 2) Is this a top level binding? + -- + -- 3) 'exprIsHNF' template (cached); it is ok to discard a 'seq' on + -- this variable + -- + -- 4) Does this waste only a little work if we expand it inside an inlining? + -- Basically this is a cached version of 'exprIsCheap' + -- + -- 5) Tells us about the /size/ of the unfolding template + +-- | When unfolding should take place data UnfoldingGuidance = UnfoldNever | UnfoldIfGoodArgs Int -- and "n" value args @@ -317,7 +445,11 @@ data UnfoldingGuidance -- a context (case (thing args) of ...), -- (where there are the right number of arguments.) -noUnfolding, evaldUnfolding :: Unfolding +noUnfolding :: Unfolding +-- ^ There is no known 'Unfolding' +evaldUnfolding :: Unfolding +-- ^ This unfolding marks the associated thing as being evaluated + noUnfolding = NoUnfolding evaldUnfolding = OtherCon [] @@ -335,48 +467,61 @@ seqGuidance _ = () \end{code} \begin{code} +-- | Retrieves the template of an unfolding: panics if none is known unfoldingTemplate :: Unfolding -> CoreExpr unfoldingTemplate (CoreUnfolding expr _ _ _ _) = expr unfoldingTemplate (CompulsoryUnfolding expr) = expr unfoldingTemplate _ = panic "getUnfoldingTemplate" +-- | Retrieves the template of an unfolding if possible maybeUnfoldingTemplate :: Unfolding -> Maybe CoreExpr maybeUnfoldingTemplate (CoreUnfolding expr _ _ _ _) = Just expr maybeUnfoldingTemplate (CompulsoryUnfolding expr) = Just expr maybeUnfoldingTemplate _ = Nothing +-- | The constructors that the unfolding could never be: +-- returns @[]@ if no information is available otherCons :: Unfolding -> [AltCon] otherCons (OtherCon cons) = cons otherCons _ = [] +-- | Determines if it is certainly the case that the unfolding will +-- yield a value (something in HNF): returns @False@ if unsure isValueUnfolding :: Unfolding -> Bool - -- Returns False for OtherCon isValueUnfolding (CoreUnfolding _ _ is_evald _ _) = is_evald isValueUnfolding _ = False +-- | Determines if it possibly the case that the unfolding will +-- yield a value. Unlike 'isValueUnfolding' it returns @True@ +-- for 'OtherCon' isEvaldUnfolding :: Unfolding -> Bool - -- Returns True for OtherCon isEvaldUnfolding (OtherCon _) = True isEvaldUnfolding (CoreUnfolding _ _ is_evald _ _) = is_evald isEvaldUnfolding _ = False +-- | Is the thing we will unfold into certainly cheap? isCheapUnfolding :: Unfolding -> Bool isCheapUnfolding (CoreUnfolding _ _ _ is_cheap _) = is_cheap isCheapUnfolding _ = False +-- | Must this unfolding happen for the code to be executable? isCompulsoryUnfolding :: Unfolding -> Bool isCompulsoryUnfolding (CompulsoryUnfolding _) = True isCompulsoryUnfolding _ = False +-- | Do we have an available or compulsory unfolding? hasUnfolding :: Unfolding -> Bool hasUnfolding (CoreUnfolding _ _ _ _ _) = True hasUnfolding (CompulsoryUnfolding _) = True hasUnfolding _ = False +-- | Only returns False if there is no unfolding information available at all hasSomeUnfolding :: Unfolding -> Bool hasSomeUnfolding NoUnfolding = False hasSomeUnfolding _ = True +-- | Similar to @not . hasUnfolding@, but also returns @True@ +-- if it has an unfolding that says it should never occur neverUnfold :: Unfolding -> Bool neverUnfold NoUnfolding = True neverUnfold (OtherCon _) = True @@ -412,7 +557,7 @@ ltAlt :: Alt b -> Alt b -> Bool ltAlt a1 a2 = (a1 `cmpAlt` a2) == LT cmpAltCon :: AltCon -> AltCon -> Ordering --- Compares AltCons within a single list of alternatives +-- ^ Compares 'AltCon's within a single list of alternatives cmpAltCon DEFAULT DEFAULT = EQ cmpAltCon DEFAULT _ = LT @@ -426,26 +571,34 @@ cmpAltCon con1 con2 = WARN( True, text "Comparing incomparable AltCons" <+> LT \end{code} - %************************************************************************ %* * \subsection{Useful synonyms} %* * %************************************************************************ -The common case - \begin{code} +-- | The common case for the type of binders and variables when +-- we are manipulating the Core language within GHC type CoreBndr = Var +-- | Expressions where binders are 'CoreBndr's type CoreExpr = Expr CoreBndr +-- | Argument expressions where binders are 'CoreBndr's type CoreArg = Arg CoreBndr +-- | Binding groups where binders are 'CoreBndr's type CoreBind = Bind CoreBndr +-- | Case alternatives where binders are 'CoreBndr's type CoreAlt = Alt CoreBndr \end{code} -Binders are ``tagged'' with a \tr{t}: +%************************************************************************ +%* * +\subsection{Tagging} +%* * +%************************************************************************ \begin{code} +-- | Binders are /tagged/ with a t data TaggedBndr t = TB CoreBndr t -- TB for "tagged binder" type TaggedBind t = Bind (TaggedBndr t) @@ -468,41 +621,96 @@ instance Outputable b => OutputableBndr (TaggedBndr b) where %************************************************************************ \begin{code} +-- | Apply a list of argument expressions to a function expression in a nested fashion. Prefer to +-- use 'CoreUtils.mkCoreApps' if possible mkApps :: Expr b -> [Arg b] -> Expr b +-- | Apply a list of type argument expressions to a function expression in a nested fashion mkTyApps :: Expr b -> [Type] -> Expr b -mkValApps :: Expr b -> [Expr b] -> Expr b +-- | Apply a list of type or value variables to a function expression in a nested fashion mkVarApps :: Expr b -> [Var] -> Expr b +-- | Apply a list of argument expressions to a data constructor in a nested fashion. Prefer to +-- use 'MkCore.mkCoreConApps' if possible +mkConApp :: DataCon -> [Arg b] -> Expr b mkApps f args = foldl App f args mkTyApps f args = foldl (\ e a -> App e (Type a)) f args -mkValApps f args = foldl (\ e a -> App e a) f args mkVarApps f vars = foldl (\ e a -> App e (varToCoreExpr a)) f vars +mkConApp con args = mkApps (Var (dataConWorkId con)) args + -mkLit :: Literal -> Expr b +-- | Create a machine integer literal expression of type @Int#@ from an @Integer@. +-- If you want an expression of type @Int@ use 'MkCore.mkIntExpr' mkIntLit :: Integer -> Expr b +-- | Create a machine integer literal expression of type @Int#@ from an @Int@. +-- If you want an expression of type @Int@ use 'MkCore.mkIntExpr' mkIntLitInt :: Int -> Expr b -mkConApp :: DataCon -> [Arg b] -> Expr b + +mkIntLit n = Lit (mkMachInt n) +mkIntLitInt n = Lit (mkMachInt (toInteger n)) + +-- | Create a machine word literal expression of type @Word#@ from an @Integer@. +-- If you want an expression of type @Word@ use 'MkCore.mkWordExpr' +mkWordLit :: Integer -> Expr b +-- | Create a machine word literal expression of type @Word#@ from a @Word@. +-- If you want an expression of type @Word@ use 'MkCore.mkWordExpr' +mkWordLitWord :: Word -> Expr b + +mkWordLit w = Lit (mkMachWord w) +mkWordLitWord w = Lit (mkMachWord (toInteger w)) + +-- | Create a machine character literal expression of type @Char#@. +-- If you want an expression of type @Char@ use 'MkCore.mkCharExpr' +mkCharLit :: Char -> Expr b +-- | Create a machine string literal expression of type @Addr#@. +-- If you want an expression of type @String@ use 'MkCore.mkStringExpr' +mkStringLit :: String -> Expr b + +mkCharLit c = Lit (mkMachChar c) +mkStringLit s = Lit (mkMachString s) + +-- | Create a machine single precision literal expression of type @Float#@ from a @Rational@. +-- If you want an expression of type @Float@ use 'MkCore.mkFloatExpr' +mkFloatLit :: Rational -> Expr b +-- | Create a machine single precision literal expression of type @Float#@ from a @Float@. +-- If you want an expression of type @Float@ use 'MkCore.mkFloatExpr' +mkFloatLitFloat :: Float -> Expr b + +mkFloatLit f = Lit (mkMachFloat f) +mkFloatLitFloat f = Lit (mkMachFloat (toRational f)) + +-- | Create a machine double precision literal expression of type @Double#@ from a @Rational@. +-- If you want an expression of type @Double@ use 'MkCore.mkDoubleExpr' +mkDoubleLit :: Rational -> Expr b +-- | Create a machine double precision literal expression of type @Double#@ from a @Double@. +-- If you want an expression of type @Double@ use 'MkCore.mkDoubleExpr' +mkDoubleLitDouble :: Double -> Expr b + +mkDoubleLit d = Lit (mkMachDouble d) +mkDoubleLitDouble d = Lit (mkMachDouble (toRational d)) + +-- | Bind all supplied binding groups over an expression in a nested let expression. Prefer to +-- use 'CoreUtils.mkCoreLets' if possible mkLets :: [Bind b] -> Expr b -> Expr b +-- | Bind all supplied binders over an expression in a nested lambda expression. Prefer to +-- use 'CoreUtils.mkCoreLams' if possible mkLams :: [b] -> Expr b -> Expr b -mkLit lit = Lit lit -mkConApp con args = mkApps (Var (dataConWorkId con)) args - mkLams binders body = foldr Lam body binders mkLets binds body = foldr Let body binds -mkIntLit n = Lit (mkMachInt n) -mkIntLitInt n = Lit (mkMachInt (toInteger n)) +-- | Create a binding group where a type variable is bound to a type. Per "CoreSyn#type_let", +-- this can only be used to bind something in a non-recursive @let@ expression +mkTyBind :: TyVar -> Type -> CoreBind +mkTyBind tv ty = NonRec tv (Type ty) + +-- | Convert a binder into either a 'Var' or 'Type' 'Expr' appropriately varToCoreExpr :: CoreBndr -> Expr b varToCoreExpr v | isId v = Var v | otherwise = Type (mkTyVarTy v) varsToCoreExprs :: [CoreBndr] -> [Expr b] varsToCoreExprs vs = map varToCoreExpr vs - -mkCast :: Expr b -> Coercion -> Expr b -mkCast e co = Cast e co \end{code} @@ -513,15 +721,12 @@ mkCast e co = Cast e co %************************************************************************ \begin{code} -mkTyBind :: TyVar -> Type -> CoreBind -mkTyBind tv ty = NonRec tv (Type ty) - -- Note [Type let] - -- A non-recursive let can bind a type variable - +-- | Extract every variable by this group bindersOf :: Bind b -> [b] bindersOf (NonRec binder _) = [binder] bindersOf (Rec pairs) = [binder | (binder, _) <- pairs] +-- | 'bindersOf' applied to a list of binding groups bindersOfBinds :: [Bind b] -> [b] bindersOfBinds binds = foldr ((++) . bindersOf) [] binds @@ -532,22 +737,25 @@ rhssOfBind (Rec pairs) = [rhs | (_,rhs) <- pairs] rhssOfAlts :: [Alt b] -> [Expr b] rhssOfAlts alts = [e | (_,_,e) <- alts] -flattenBinds :: [Bind b] -> [(b, Expr b)] -- Get all the lhs/rhs pairs +-- | Collapse all the bindings in the supplied groups into a single +-- list of lhs/rhs pairs suitable for binding in a 'Rec' binding group +flattenBinds :: [Bind b] -> [(b, Expr b)] flattenBinds (NonRec b r : binds) = (b,r) : flattenBinds binds flattenBinds (Rec prs1 : binds) = prs1 ++ flattenBinds binds flattenBinds [] = [] \end{code} -We often want to strip off leading lambdas before getting down to -business. @collectBinders@ is your friend. - -We expect (by convention) type-, and value- lambdas in that -order. - \begin{code} +-- | We often want to strip off leading lambdas before getting down to +-- business. This function is your friend. collectBinders :: Expr b -> ([b], Expr b) +-- | Collect as many type bindings as possible from the front of a nested lambda collectTyBinders :: CoreExpr -> ([TyVar], CoreExpr) +-- | Collect as many value bindings as possible from the front of a nested lambda collectValBinders :: CoreExpr -> ([Id], CoreExpr) +-- | Collect type binders from the front of the lambda first, +-- then follow up by collecting as many value bindings as possible +-- from the resulting stripped expression collectTyAndValBinders :: CoreExpr -> ([TyVar], [Id], CoreExpr) collectBinders expr @@ -575,11 +783,9 @@ collectValBinders expr go ids body = (reverse ids, body) \end{code} - -@collectArgs@ takes an application expression, returning the function -and the arguments to which it is applied. - \begin{code} +-- | Takes a nested application expression and returns the the function +-- being applied and the arguments to which it is applied collectArgs :: Expr b -> (Expr b, [Arg b]) collectArgs expr = go expr [] @@ -588,10 +794,9 @@ collectArgs expr go e as = (e, as) \end{code} -coreExprCc gets the cost centre enclosing an expression, if any. -It looks inside lambdas because (scc "foo" \x.e) = \x.scc "foo" e - \begin{code} +-- | Gets the cost centre enclosing an expression, if any. +-- It looks inside lambdas because @(scc \"foo\" \\x.e) = \\x. scc \"foo\" e@ coreExprCc :: Expr b -> CostCentre coreExprCc (Note (SCC cc) _) = cc coreExprCc (Note _ e) = coreExprCc e @@ -599,8 +804,6 @@ coreExprCc (Lam _ e) = coreExprCc e coreExprCc _ = noCostCentre \end{code} - - %************************************************************************ %* * \subsection{Predicates} @@ -613,23 +816,29 @@ i.e. if type applications are actual lambdas because types are kept around at runtime. Similarly isRuntimeArg. \begin{code} +-- | Will this variable exist at runtime? isRuntimeVar :: Var -> Bool isRuntimeVar = isId +-- | Will this argument expression exist at runtime? isRuntimeArg :: CoreExpr -> Bool isRuntimeArg = isValArg +-- | Returns @False@ iff the expression is a 'Type' expression at its top level isValArg :: Expr b -> Bool isValArg (Type _) = False isValArg _ = True +-- | Returns @True@ iff the expression is a 'Type' expression at its top level isTypeArg :: Expr b -> Bool isTypeArg (Type _) = True isTypeArg _ = False +-- | The number of binders that bind values rather than types valBndrCount :: [CoreBndr] -> Int valBndrCount = count isId +-- | The number of argument expressions that are values rather than types at their top level valArgCount :: [Arg b] -> Int valArgCount = count isValArg \end{code} @@ -687,17 +896,17 @@ seqRules (Rule { ru_bndrs = bndrs, ru_args = args, ru_rhs = rhs } : rules) seqRules (BuiltinRule {} : rules) = seqRules rules \end{code} - - %************************************************************************ %* * -\subsection{Annotated core; annotation at every node in the tree} +\subsection{Annotated core} %* * %************************************************************************ \begin{code} +-- | Annotated core: allows annotation at every node in the tree type AnnExpr bndr annot = (annot, AnnExpr' bndr annot) +-- | A clone of the 'Expr' type but allowing annotation at every tree node data AnnExpr' bndr annot = AnnVar Id | AnnLit Literal @@ -709,8 +918,10 @@ data AnnExpr' bndr annot | AnnNote Note (AnnExpr bndr annot) | AnnType Type +-- | A clone of the 'Alt' type but allowing annotation at every tree node type AnnAlt bndr annot = (AltCon, [bndr], AnnExpr bndr annot) +-- | A clone of the 'Bind' type but allowing annotation at every tree node data AnnBind bndr annot = AnnNonRec bndr (AnnExpr bndr annot) | AnnRec [(bndr, AnnExpr bndr annot)] @@ -743,6 +954,7 @@ deAnnAlt (con,args,rhs) = (con,args,deAnnotate rhs) \end{code} \begin{code} +-- | As 'collectBinders' but for 'AnnExpr' rather than 'Expr' collectAnnBndrs :: AnnExpr bndr annot -> ([bndr], AnnExpr bndr annot) collectAnnBndrs e = collect [] e