ghc-8.2.2: The GHC API

IdInfo

Synopsis

# The IdDetails type

data IdDetails #

Identifier Details

The IdDetails of an Id give stable, and necessary, information about the Id.

Constructors

 VanillaId RecSelId The Id for a record selector Fields DataConWorkId DataCon The Id is for a data constructor worker DataConWrapId DataCon The Id is for a data constructor wrapper ClassOpId Class The Id is a superclass selector, or class operation of a class PrimOpId PrimOp The Id is for a primitive operator FCallId ForeignCall The Id is for a foreign call. Type will be simple: no type families, newtypes, etc TickBoxOpId TickBoxOp The Id is for a HPC tick box (both traditional and binary) DFunId Bool A dictionary function. Bool = True = the class has only one method, so may be implemented with a newtype, so it might be bad to be strict on this dictionary CoVarId A coercion variable This only covers un-lifted coercions, of type (t1 ~ t2), not their lifted variants JoinId JoinArity An Id for a join point taking n arguments Note [Join points] in CoreSyn

Instances

 # Methods

Just a synonym for CoVarId. Written separately so it can be exported in the hs-boot file.

Check if an IdDetails says CoVarId.

type JoinArity = Int #

The number of arguments that a join point takes. Unlike the arity of a function, this is a purely syntactic property and is fixed when the join point is created (or converted from a value). Both type and value arguments are counted.

data RecSelParent #

Recursive Selector Parent

Constructors

 RecSelData TyCon RecSelPatSyn PatSyn

Instances

 # Methods # Methods

# The IdInfo type

data IdInfo #

Identifier Information

An IdInfo gives optional information about an Id. If present it never lies, but it may not be present, in which case there is always a conservative assumption which can be made.

Two Ids may have different info even though they have the same Unique (and are hence the same Id); for example, one might lack the properties attached to the other.

Most of the IdInfo gives information about the value, or definition, of the Id, independent of its usage. Exceptions to this are demandInfo, occInfo, oneShotInfo and callArityInfo.

Performance note: when we update IdInfo, we have to reallocate this entire record, so it is a good idea not to let this data structure get too big.

Basic IdInfo that carries no useful information whatsoever

More informative IdInfo we can use when we know the Id has no CAF references

## The OneShotInfo type

data OneShotInfo #

If the Id is a lambda-bound variable then it may have lambda-bound variable info. Sometimes we know whether the lambda binding this variable is a "one-shot" lambda; that is, whether it is applied at most once.

This information may be useful in optimisation, as computations may safely be floated inside such a lambda without risk of duplicating work.

Constructors

 NoOneShotInfo No information OneShotLam The lambda is applied at most once.

Instances

 # Methods # Methods

Info about a lambda-bound variable, if the Id is one

It is always safe to assume that an Id has no lambda-bound variable information

## Zapping various forms of Info

This is used to remove information on lambda binders that we have setup as part of a lambda group, assuming they will be applied all at once, but turn out to be part of an unsaturated lambda as in e.g:

(\x1. \x2. e) arg1

Zap info that depends on free variables

Remove all demand info on the IdInfo

Remove usage (but not strictness) info on the IdInfo

Remove usage environment info from the strictness signature on the IdInfo

## The ArityInfo type

type ArityInfo = Arity #

Arity Information

An ArityInfo of n tells us that partial application of this Id to up to n-1 value arguments does essentially no work.

That is not necessarily the same as saying that it has n leading lambdas, because coerces may get in the way.

The arity might increase later in the compilation process, if an extra lambda floats up to the binding site.

It is always safe to assume that an Id has an arity of 0

Id arity

How this is called. n = all calls have at least n arguments

## Demand and strictness Info

ID demand information

setDemandInfo :: IdInfo -> Demand -> IdInfo infixl 1 #

## Unfolding Info

The Ids unfolding

## The InlinePragInfo type

Inline Pragma Information

Tells when the inlining is active. When it is active the thing may be inlined, depending on how big it is.

If there was an INLINE pragma, then as a separate matter, the RHS will have been made to look small with a Core inline Note

The default InlinePragInfo is AlwaysActive, so the info serves entirely as a way to inhibit inlining until we want it

Any inline pragma atached to the Id

## The OccInfo type

data OccInfo #

identifier Occurrence Information

Constructors

 ManyOccs There are many occurrences, or unknown occurrences Fieldsocc_tail :: !TailCallInfo IAmDead Marks unused variables. Sometimes useful for lambda and case-bound variables. OneOcc Occurs exactly once (per branch), not inside a rule Fields IAmALoopBreaker This identifier breaks a loop of mutually recursive functions. The field marks whether it is only a loop breaker due to a reference in a rule Fieldsocc_rules_only :: !RulesOnly occ_tail :: !TailCallInfo

Instances

 # Methods(==) :: OccInfo -> OccInfo -> Bool #(/=) :: OccInfo -> OccInfo -> Bool # # Methodsppr :: OccInfo -> SDoc #

How the Id occurs in the program

setOccInfo :: IdInfo -> OccInfo -> IdInfo infixl 1 #

type InsideLam = Bool #

Inside Lambda

data TailCallInfo #

Constructors

 AlwaysTailCalled JoinArity NoTailCallInfo

Instances

 # Methods # Methods

## The RuleInfo type

data RuleInfo #

Rule Information

Records the specializations of this Id that we know about in the form of rewrite CoreRules that target them

Constructors

 RuleInfo [CoreRule] DVarSet

Assume that no specilizations exist: always safe

Retrieve the locally-defined free variables of both the left and right hand sides of the specialization rules

Change the name of the function the rule is keyed on on all of the CoreRules

Specialisations of the Ids function which exist See Note [Specialisations and RULES in IdInfo]

setRuleInfo :: IdInfo -> RuleInfo -> IdInfo infixl 1 #

## The CAFInfo type

data CafInfo #

Constant applicative form Information

Records whether an Id makes Constant Applicative Form references

Constructors

 MayHaveCafRefs Indicates that the Id is for either:A function or static constructor that refers to one or more CAFs, orA real live CAF NoCafRefs A function or static constructor that refers to no CAFs.

Instances

 # Methods(==) :: CafInfo -> CafInfo -> Bool #(/=) :: CafInfo -> CafInfo -> Bool # # Methods(<) :: CafInfo -> CafInfo -> Bool #(<=) :: CafInfo -> CafInfo -> Bool #(>) :: CafInfo -> CafInfo -> Bool #(>=) :: CafInfo -> CafInfo -> Bool # # Methodsppr :: CafInfo -> SDoc #

Id CAF info

setCafInfo :: IdInfo -> CafInfo -> IdInfo infixl 1 #

## Tick-box Info

data TickBoxOp #

Tick box for Hpc-style coverage

Constructors

 TickBox Module !TickBoxId

Instances

 # Methods

type TickBoxId = Int #

## Levity info

data LevityInfo #

Instances

 # Methods # Methods

when applied, will this Id ever have a levity-polymorphic type?

setNeverLevPoly :: HasDebugCallStack => IdInfo -> Type -> IdInfo infixl 1 #

Marks an IdInfo describing an Id that is never levity polymorphic (even when applied). The Type is only there for checking that it's really never levity polymorphic