IdInfo

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.

The IdInfo gives information about the value, or definition, of the Id. It does not contain information about the Id's usage, except for demandInfo and lbvarInfo.

vanillaIdInfo :: IdInfo

Basic IdInfo that carries no useful information whatsoever

noCafIdInfo :: IdInfo

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

seqIdInfo :: IdInfo -> ()

Just evaluate the IdInfo to WHNF

megaSeqIdInfo :: IdInfo -> ()

Evaluate all the fields of the IdInfo that are generally demanded by the compiler

Zapping various forms of Info

zapLamInfo :: IdInfo -> Maybe IdInfo

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

zapDemandInfo :: IdInfo -> Maybe IdInfo

Remove demand info on the IdInfo if it is present, otherwise return Nothing

zapFragileInfo :: IdInfo -> Maybe IdInfo

Zap info that depends on free variables

The ArityInfo type

type ArityInfo = Arity

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.

unknownArity :: Arity

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

arityInfo :: IdInfo -> ArityInfo

Id arity

setArityInfo :: IdInfo -> ArityInfo -> IdInfo

ppArityInfo :: Int -> SDoc

Demand and strictness Info

newStrictnessInfo :: IdInfo -> Maybe StrictSig

Id strictness information. Reason for Maybe: the DmdAnal phase needs to know whether this is the first visit, so it can assign botSig. Other customers want topSig. So Nothing is good.

setNewStrictnessInfo :: IdInfo -> Maybe StrictSig -> IdInfo

newDemandInfo :: IdInfo -> Maybe Demand

Id demand information. Similarly we want to know if there's no known demand yet, for when we are looking for CPR info

setNewDemandInfo :: IdInfo -> Maybe Demand -> IdInfo

pprNewStrictness :: Maybe StrictSig -> SDoc

setAllStrictnessInfo :: IdInfo -> Maybe StrictSig -> IdInfo

Set old and new strictness information together

The WorkerInfo type

data WorkerInfo

If this Id has a worker then we store a reference to it. Worker functions are generated by the worker/wrapper pass, using information information from strictness analysis.

Constructors

NoWorker	No known worker function
HasWorker Id Arity	The `Arity` is the arity of the wrapper at the moment of the worker/wrapper split, which may be different from the current `Id` Aritiy

workerExists :: WorkerInfo -> Bool

wrapperArity :: WorkerInfo -> Arity

The Arity of the worker function at the time of the split if it exists, or a panic otherwise

workerId :: WorkerInfo -> Id

The Id of the worker function if it exists, or a panic otherwise

workerInfo :: IdInfo -> WorkerInfo

Pointer to worker function. Within one module this is irrelevant; the inlining of a worker is handled via the Unfolding. However, when the module is imported by others, the WorkerInfo is used only to indicate the form of the RHS, so that interface files don't actually need to contain the RHS; it can be derived from the strictness info

setWorkerInfo :: IdInfo -> WorkerInfo -> IdInfo

ppWorkerInfo :: WorkerInfo -> SDoc

Unfolding Info

unfoldingInfo :: IdInfo -> Unfolding

The Ids unfolding

setUnfoldingInfo :: IdInfo -> Unfolding -> IdInfo

setUnfoldingInfoLazily :: IdInfo -> Unfolding -> IdInfo

The InlinePragInfo type

type InlinePragInfo = Activation

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

inlinePragInfo :: IdInfo -> InlinePragInfo

Any inline pragma atached to the Id

setInlinePragInfo :: IdInfo -> InlinePragInfo -> IdInfo

The OccInfo type

data OccInfo

Identifier occurrence information

Constructors

NoOccInfo	There are many occurrences, or unknown occurences
IAmDead	Marks unused variables. Sometimes useful for lambda and case-bound variables.
OneOcc !InsideLam !OneBranch !InterestingCxt	Occurs exactly once, not inside a rule
IAmALoopBreaker !RulesOnly	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

Instances

Show OccInfo

Outputable OccInfo

isFragileOcc :: OccInfo -> Bool

isDeadOcc :: OccInfo -> Bool

isLoopBreaker :: OccInfo -> Bool

occInfo :: IdInfo -> OccInfo

How the Id occurs in the program

setOccInfo :: IdInfo -> OccInfo -> IdInfo

type InsideLam = Bool

type OneBranch = Bool

notInsideLam :: InsideLam

notOneBranch :: OneBranch

The SpecInfo type

data SpecInfo

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

Constructors

SpecInfo [CoreRule] VarSet

isEmptySpecInfo :: SpecInfo -> Bool

specInfoFreeVars :: SpecInfo -> VarSet

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

specInfoRules :: SpecInfo -> [CoreRule]

seqSpecInfo :: SpecInfo -> ()

setSpecInfoHead :: Name -> SpecInfo -> SpecInfo

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

specInfo :: IdInfo -> SpecInfo

Specialisations of the Ids function which exist

setSpecInfo :: IdInfo -> SpecInfo -> IdInfo

The CAFInfo type

data CafInfo

Records whether an Id makes Constant Applicative Form references

Constructors

MayHaveCafRefs

Indicates that the Id is for either:

1. A function or static constructor that refers to one or more CAFs, or

2. A real live CAF

NoCafRefs A function or static constructor that refers to no CAFs.

ppCafInfo :: CafInfo -> SDoc

mayHaveCafRefs :: CafInfo -> Bool

cafInfo :: IdInfo -> CafInfo

Id CAF info

setCafInfo :: IdInfo -> CafInfo -> IdInfo

The LBVarInfo type

data LBVarInfo

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