ghc-8.2.1: The GHC API

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Utils for calculating general worst, bound, squeese and free, functions.

as per: "A Generalized Algorithm for Graph-Coloring Register Allocation" Michael Smith, Normal Ramsey, Glenn Holloway. PLDI 2004

These general versions are not used in GHC proper because they are too slow. Instead, hand written optimised versions are provided for each architecture in MachRegs*.hs

This code is here because we can test the architecture specific code against it.



data Reg Source #

A register of some class


Reg RegClass Int 
RegSub RegSub Reg 


Eq Reg Source # 


(==) :: Reg -> Reg -> Bool #

(/=) :: Reg -> Reg -> Bool #

Show Reg Source # 


showsPrec :: Int -> Reg -> ShowS #

show :: Reg -> String #

showList :: [Reg] -> ShowS #

Uniquable Reg Source #

so we can put regs in UniqSets


getUnique :: Reg -> Unique Source #

data RegSub Source #

A subcomponent of another register



worst :: (RegClass -> UniqSet Reg) -> (Reg -> UniqSet Reg) -> Int -> RegClass -> RegClass -> Int Source #

Worst case displacement

a node N of classN has some number of neighbors, all of which are from classC.

(worst neighbors classN classC) is the maximum number of potential colors for N that can be lost by coloring its neighbors.

This should be hand coded/cached for each particular architecture, because the compute time is very long..

bound :: (RegClass -> UniqSet Reg) -> (Reg -> UniqSet Reg) -> RegClass -> [RegClass] -> Int Source #

For a node N of classN and neighbors of classesC (bound classN classesC) is the maximum number of potential colors for N that can be lost by coloring its neighbors.

squeese :: (RegClass -> UniqSet Reg) -> (Reg -> UniqSet Reg) -> RegClass -> [(Int, RegClass)] -> Int Source #

The total squeese on a particular node with a list of neighbors.

A version of this should be constructed for each particular architecture, possibly including uses of bound, so that alised registers don't get counted twice, as per the paper.