GHC.Cmm.Switch

Documentation

data SwitchTargets

A value of type SwitchTargets contains the alternatives for a CmmSwitch value, and knows whether the value is signed, the possible range, an optional default value and a map from values to jump labels.

Instances

Show SwitchTargets

Defined in GHC.Cmm.Switch

Methods

showsPrec :: Int -> SwitchTargets -> ShowS

show :: SwitchTargets -> String

showList :: [SwitchTargets] -> ShowS

Eq SwitchTargets

Defined in GHC.Cmm.Switch

Methods

(==) :: SwitchTargets -> SwitchTargets -> Bool

(/=) :: SwitchTargets -> SwitchTargets -> Bool

mkSwitchTargets :: Bool -> (Integer, Integer) -> Maybe Label -> Map Integer Label -> SwitchTargets

The smart constructor mkSwitchTargets normalises the map a bit: * No entries outside the range * No entries equal to the default * No default if all elements have explicit values

switchTargetsCases :: SwitchTargets -> [(Integer, Label)]

Returns the list of non-default branches of the SwitchTargets value

switchTargetsDefault :: SwitchTargets -> Maybe Label

Return the default label of the SwitchTargets value

switchTargetsRange :: SwitchTargets -> (Integer, Integer)

Return the range of the SwitchTargets value

switchTargetsSigned :: SwitchTargets -> Bool

Return whether this is used for a signed value

mapSwitchTargets :: (Label -> Label) -> SwitchTargets -> SwitchTargets

Changes all labels mentioned in the SwitchTargets value

switchTargetsToTable :: SwitchTargets -> (Int, [Maybe Label])

switchTargetsToTable creates a dense jump table, usable for code generation.

Also returns an offset to add to the value; the list is 0-based on the result of that addition.

The conversion from Integer to Int is a bit of a wart, as the actual scrutinee might be an unsigned word, but it just works, due to wrap-around arithmetic (as verified by the CmmSwitchTest test case).

switchTargetsFallThrough :: SwitchTargets -> ([(NonEmpty Integer, Label)], Maybe Label)

Groups cases with equal targets, suitable for pretty-printing to a c-like switch statement with fall-through semantics.

switchTargetsToList :: SwitchTargets -> [Label]

The list of all labels occurring in the SwitchTargets value.

eqSwitchTargetWith :: (Label -> Label -> Bool) -> SwitchTargets -> SwitchTargets -> Bool

Custom equality helper, needed for GHC.Cmm.CommonBlockElim

data SwitchPlan

A SwitchPlan abstractly describes how a Switch statement ought to be implemented. See Note [createSwitchPlan]

Constructors

Unconditionally Label

IfEqual Integer Label SwitchPlan

IfLT Bool Integer SwitchPlan SwitchPlan

JumpTable SwitchTargets

Instances

Show SwitchPlan

Defined in GHC.Cmm.Switch

Methods

showsPrec :: Int -> SwitchPlan -> ShowS

show :: SwitchPlan -> String

showList :: [SwitchPlan] -> ShowS

backendHasNativeSwitch :: Backend -> Bool

The back end targets a technology that implements switch natively. (For example, LLVM or C.) Therefore it is not necessary for GHC to ccompile a Cmm Switch form into a decision tree with jump tables at the leaves.

createSwitchPlan :: SwitchTargets -> SwitchPlan

This function creates a SwitchPlan from a SwitchTargets value, breaking it down into smaller pieces suitable for code generation.