-- This module is based on the "linearscan" package by John Wiegley.
-- It is meant to present a similar interface.
-- http://github.com/jwiegley/linearscan
signature RegAlloc where

import RegAlloc.Types

-- | Transform a list of basic blocks, containing variable references, into an
-- equivalent list where each reference has been associated with a register
-- allocation. Artificial save and restore instructions may be inserted into
-- those blocks to indicate spilling and reloading of variables.
-- In order to call this function, the caller must provide records that
-- functionally characterize these blocks and their operations according to an
-- abstract API. This is done so that any program graph conforming to the API
-- may be used, and no particular representation is required.
-- A tuple is return where the first value is a textual dump that describes
-- the complete allocation state. If this value is never forced, that data is
-- not collected.
-- The second value is the resulting list of allocated blocks. If allocation
-- is found to be impossible -- for example if there are not enough registers
-- -- a 'Left' value is returned, with a list of strings describing the error
-- and its possible context. This is usually when the textual dump should be
-- provided, if one's user has selected verbose error output, for example.
allocate :: (Functor m, Applicative m, Monad m)
         => Int        -- ^ Maximum number of registers to use
         -> BlockInfo m blk1 blk2 op1 op2
                      -- ^ Characterization of blocks
         -> OpInfo m op1 op2
                      -- ^ Characterization of operations
         -> UseVerifier
                      -- ^ Whether to use the runtime verifier
         -> [blk1]     -- ^ A topologically sorted list of blocks
         -> m (String, Either [String] [blk2])
                      -- ^ Status dump and allocated blocks, or error w/ context