Changelog for hoopl-

Changelog for hoopl package Dec 2015

This release includes only non-functional changes. Aug 2015 Apr 2015 Dec 2014 Mar 2014 Mar 2014

Lots of API changes; mainly a new API for working with Blocks

Summary of refactorings:

Other changes:

Summary of API changes:




Interface changes

The type of AGraph is now abstract. It is now recommended to create AGraphs with just three functions:

<*>          concatenation
|*><*|       splicing at a closed point
addBlocks    add C/C blocks out of line

There are new utility functions in modules Util and XUtil, all exported by Compiler.Hoopl. Here's a selection:

-- | A utility function so that a transfer function for a first
-- node can be given just a fact; we handle the lookup.  This
-- function is planned to be made obsolete by changes in the dataflow
-- interface.
firstXfer :: Edges n => (n C O -> f -> f) -> (n C O -> FactBase f -> f)
firstXfer xfer n fb = xfer n $ fromJust $ lookupFact fb $ entryLabel n

-- | This utility function handles a common case in which a transfer function
-- produces a single fact out of a last node, which is then distributed
-- over the outgoing edges.
distributeXfer :: Edges n => (n O C -> f -> f) -> (n O C -> f -> FactBase f)
distributeXfer xfer n f = mkFactBase [ (l, xfer n f) | l <- successors n ]

-- | This utility function handles a common case in which a transfer function
-- for a last node takes the incoming fact unchanged and simply distributes
-- that fact over the outgoing edges.
distributeFact :: Edges n => n O C -> f -> FactBase f

-- | Function 'graphMapBlocks' enables a change of representation of blocks,
-- nodes, or both.  It lifts a polymorphic block transform into a polymorphic
-- graph transform.  When the block representation stabilizes, a similar
-- function should be provided for blocks.
graphMapBlocks :: forall block n block' n' e x .
                  (forall e x . block n e x -> block' n' e x)
               -> (Graph' block n e x -> Graph' block' n' e x)

postorder_dfs :: Edges (block n) => Graph' block n O x -> [block n C C]

There are quite a few other variations related to depth-first traversal.

There is a new module Compiler.Hoopl.Pointed, which uses GADTs to enable you to add a Top or Bot element to a lattice, or both, all using the same type. (Types WithBot and WithTop in XUtil, exported by Compiler.Hoopl, do similar jobs, but I think they are inferior. Your opinion is solicited.)

I added a function showGraph to print Graphs. Right now it requires a polymorphic node-showing function as argument. When we change the Block representation we may get enough static type information that we can simply have an instance declaration for

instance (Show n C O, Show n O O, Show n O C) => Show (Graph n e x)

At present, I don't see how to achieve such a declaration.

John added new functions debugFwdJoins and debugBwdJoins to extend passes with debugging information.

We added primed versions of the analyzeAndRewrite functions, which operate on Graph, not Body. Recommended, at least for first-timers.

Not all maps keyed by Label are FactBases, so there is now a new set of names of functions to manipulate LabelMaps that do not contain dataflow facts.

Implementation changes

Split pass and rewrite-function combinators into Compiler.Hoopl.Combinators.

Changed order of blocks for forward and backward analysis. These changes have not been tested, because we don't have a true regression suite yet.

Graph and Body types now have more polymorphic variants Graph' and Body'.

Lots of experiments with zippers.

Changes ahead

ForwardTransfer will become an abstract type, and clients will have two ways to create ForwardTransfers: as now, with a single, polymorphic transfer function; or with a triple of monomorphic transfer functions. The implementation will use monomorphic functions, which will enable more useful combinators on passes, including adding more debugging information and enabling us to combine passes.

Perhaps we should provide splicing and addBlocks on Graph?

Change of block representation to have three monomorphic unit constructors and one polymorphic concatenation constructor.

Graph body to be represented by a finite map; add functions to check for duplicate labels.