% (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"
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}
\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 <http://research.microsoft.com/~simonpj/papers/ext-f/> for this purpose,
+-- which is closely related to the simpler and better known System F <http://en.wikipedia.org/wiki/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]
~~~~~~~~~~~~~~~~~~~~~~~
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)
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
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}
%* *
%************************************************************************
-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
-- 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 []
\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
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
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)
%************************************************************************
\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}
%************************************************************************
\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
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
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 []
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
coreExprCc _ = noCostCentre
\end{code}
-
-
%************************************************************************
%* *
\subsection{Predicates}
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}
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
| 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)]
\end{code}
\begin{code}
+-- | As 'collectBinders' but for 'AnnExpr' rather than 'Expr'
collectAnnBndrs :: AnnExpr bndr annot -> ([bndr], AnnExpr bndr annot)
collectAnnBndrs e
= collect [] e
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