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 RegClass
- data Reg
- data RegSub
- worst :: (RegClass -> UniqSet Reg) -> (Reg -> UniqSet Reg) -> Int -> RegClass -> RegClass -> Int
- bound :: (RegClass -> UniqSet Reg) -> (Reg -> UniqSet Reg) -> RegClass -> [RegClass] -> Int
- squeese :: (RegClass -> UniqSet Reg) -> (Reg -> UniqSet Reg) -> RegClass -> [(Int, RegClass)] -> Int

# Documentation

A register of some class

A subcomponent of another register

worst :: (RegClass -> UniqSet Reg) -> (Reg -> UniqSet Reg) -> Int -> RegClass -> RegClass -> IntSource

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.

bound :: (RegClass -> UniqSet Reg) -> (Reg -> UniqSet Reg) -> RegClass -> [RegClass] -> IntSource

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)] -> IntSource

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.