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bf196b8be9
Branches: main, 10.04 Update the TODO and WORK_IN_PROGRESS files. Don't give the impression that we might support user-defined operators at some point in the future; this is not likely to happen. compiler/notes/todo: Remove some things that have now been implemented from the todo list. Remove user-defined operators from the wishlist. compiler/notes/work_in_progress.html: Remove the Java backend and lco from the list of work-in-progress. doc/transition_guide.texi: Don't give the impression that Mercury might support user-defined operators.
374 lines
9.2 KiB
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374 lines
9.2 KiB
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<html>
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<head>
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<title>To Do List</title>
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</head>
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<body bgcolor="#ffffff" text="#000000">
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<hr>
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<!--======================-->
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<h1> TODO LIST </h1>
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<hr>
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<!--======================-->
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<p>
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For more information on any of these issues, contact
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mercury@csse.unimelb.edu.au.
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<p>
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<h2> mode analysis </h2>
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<p>
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<ul>
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<li> fix various bugs in mode inference:
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need to fix it to work properly in the presence of functions;
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also need to change normalise_inst so that it handles complicated
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insts such as `list_skel(any)'.
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<li> extend the mode system to allow known aliasing.
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This is needed to make partially instantiated modes and unique modes work.
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[supported on the "alias" branch, but there were some serious
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performance problems... has not been merged back into the main
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branch]
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</ul>
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<h2> determinism analysis </h2>
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<p>
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<ul>
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<li> add functionality for promise exclusive declarations:
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<ul>
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<li> add error checking and type checking as for assertions
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<li> include declaration information in the module_info
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<li> take into account mutual exclusivity from promise_exclusive
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and promise_exclusive_exhaustive declarations during switch
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detection
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<li> take into account exhaustiveness from promise_exhaustive and
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promise_exclusive_exhaustive declarations during
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determinism analysis
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</ul>
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</ul>
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<h2> unique modes </h2>
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<ul>
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<li> handle nested unique modes
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<li> we will probably need to extend unique modes a bit,
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in as-yet-unknown ways; need more experience here
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</ul>
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<h2> module system </h2>
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<ul>
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<li> check that the interface for a module is type-correct
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independently of any declarations or imports in the implementation
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section
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<li> there are some problems with nested modules (see the language
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reference manual)
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</ul>
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<h2> C interface </h2>
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<ul>
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<li> exporting things for manipulating Mercury types from C
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<li> need to deal with memory management issues
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</ul>
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<h2> code generation </h2>
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<ul>
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<li> take advantage of unique modes to do compile-time garbage collection
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and structure reuse.
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</ul>
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<h2> back-ends </h2>
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<h3> low-level (LLDS) back-end </h3>
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<ul>
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<li> support accurate garbage collection
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</ul>
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<h3> high-level C back-end </h3>
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<ul>
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<li> finish off support for accurate garbage collection;
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see the comments in compiler/ml_elim_nested.m
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<li> see also the comments in compiler/ml_code_gen.m
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</ul>
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<h2> native code back-end </h2>
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<ul>
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<li> support on platforms other than Linux/x86.
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<li> commit GCC tail-call improvements to GCC CVS repository
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<li> support `--gc accurate'
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<li> support `--gc none'
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</ul>
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<h3> .NET back-end </h3>
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<ul>
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<li> finish off standard library implementation
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<li> see also the TODO list in compiler/mlds_to_il.m
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</ul>
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<h2> debugger </h2>
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<ul>
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<li> support back-ends other than LLDS
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<li> allow interactive queries to refer to values generated by
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the program being debugged
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<li> trace semidet unifications
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</ul>
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<hr>
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<!--======================-->
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<h1> WISH LIST </h1>
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<h2> type-system </h2>
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<ul>
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<li> allow construct.construct/3 to work for existential types
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<li> remove limitation that higher-order terms are monomorphic.
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i.e. allow universal quantifiers at the top level of
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higher-order types, e.g. <samp>:- pred foo(all [T] pred(T)).</samp>.
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<li> constructor classes
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<li> allow a module exporting an abstract type to specify that other modules
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should not be allowed to test two values of that type for equality (similar
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to Ada's limited private types). This would be useful for e.g. sets
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represented as unordered lists with possible duplicates.
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[this is a subset of the functionality of type classes]
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<li> subtypes?
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<li> optimisation of type representation and manipulation (possibly
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profiler guided)
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<li> fold/unfolding of types
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</ul>
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<h2> mode analysis </h2>
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<ul>
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<li> split construct/deconstruct unifications into their atomic
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"micro-unification" pieces when necessary.
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(When is it necessary?)
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<li> extend polymorphic modes,
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e.g. to handle uniqueness polymorphism (some research issues?)
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<li> handle abstract insts in the same way abstract types are handled
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(a research issue - is this possible at all?)
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<li> implement `willbe(Inst)' insts, for parallelism
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<li> mode segments & high-level transformation of circularly moded programs.
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</ul>
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<h2> determinism analysis: </h2>
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<ul>
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<li> propagate information about bindings from the condition of an if-then-else
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to the else so that
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<pre>
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(if X = [] then .... else X = [A|As], ...)
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</pre>
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is considered det.
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<li> turn chains of if-then-elses into switchs where possible.
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[done by fjh, but not committed; zs not convinced that
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this is a good idea]
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</ul>
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<h2> higher-order preds: </h2>
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<ul>
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<li> implement single-use higher-order predicate modes.
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Single-use higher-order predicates would be allowed to bind curried
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arguments, and to have unique modes for curried arguments.
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<li> allow taking the address of a predicate with multiple modes
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[we do allow this in case where the mode can be determined from
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the inst of the high-order arguments]
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<li> improve support for higher-order programming, eg. by providing
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operators in the standard library which do things like:
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<ul>
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<li>compose functions
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<li>take a predicate with one output argument and treat it like a function.
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ie. <tt>:- func (pred(T)) = T.</tt>
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</ul>
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</ul>
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<h2> module system: </h2>
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<ul>
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<li> produce warnings for implementation imports that are not needed
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<li> produce warnings for imports that are in the wrong place
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(in the interface instead of the implementation, and vice versa)
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[vice versa done by stayl]
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</ul>
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<h2> source-level transformations </h2>
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<ul>
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<li> more work on module system, separate compilation, and the multiple
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specialisation problem
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<li> transform non-tail-recursive predicates into tail-recursive form
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using accumulators. (This is already done, but not enabled by
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default since it can make some programs run much more slowly.
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More work is needed to only enable this optimization in cases
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when it will improve performance rather than pessimize it.)
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<li> improvements to deforestation / partial deduction
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</ul>
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<h2> code generation: </h2>
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<ul>
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<li> allow floating point fields of structures without boxing
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(need multi-word fields)
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<li> stack allocation of structures
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</ul>
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<h2> LLDS back-end: </h2>
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<ul>
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<li> use floating point registers
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<li> inter-procedural register allocation
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<li> other specializations, e.g. if argument is known to be bound to
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f(X,Y), then just pass X and Y in registers
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<li> reduce the overhead of higher-order predicate calls (avoid copying
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the real registers into the fake_reg array and back)
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<li> trim stack frames before making recursive calls, to minimize stack usage
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(this would probably be a pessimization much of the time - zs)
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and to minimize unnecessary garbage retention.
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<li> target C--
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</ul>
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<h2> native code back-end </h2>
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<ul>
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<li> consider supporting exception handling in a manner
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that is compatible with C++ and Java
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<li> inline more of the standard library primitives that are
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currently implemented in C
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</ul>
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<h2> garbage collection <h2>
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<ul>
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<li> implement liveness-accurate GC
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<li> implement incremental GC
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<li> implement generational GC
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<li> implement parallel GC
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<li> implement real-time GC
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</ul>
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<h2> compilation speed </h2>
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<ul>
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<li> improve efficiency of the expansion of equivalence types (currently O(N^2))
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(e.g. this is particularly bad when compiling live_vars.m).
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<li> improve efficiency of the module import handling (currently O(N^2))
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<li> use "store" rather than "map" for the major compiler data structures
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</ul>
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<h2> better diagnostics </h2>
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<ul>
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<li> optional warning for any implicit quantifiers whose scope is not
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the entire clause (the "John Lloyd" option :-).
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<li> give a better error message for the use of if-then without else.
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<li> give a better error message for the use of `<=' instead of `=<'
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(but how?)
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<li> give a better error message for type errors involving higher-order pred
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constants (requested by Bart Demoen)
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<li> give better error messages for syntax errors in lambda expressions
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</ul>
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<h2> general </h2>
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<ul>
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<li> coroutining and parallel versions of Mercury
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<li> implement streams (need coroutining at least)
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<li> implement a very fast turn-around bytecode compiler/interpreter/debugger,
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similar to Gofer
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[not-so-fast bytecode compiler done, but bytecode interpreter
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not implemented]
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<li> support for easier formal specification translation (eg a Z library,
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or Z to Mercury).
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<li> implement a source visualisation tool
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<li> distributed Mercury
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<li> improved development environment
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<li> additional software engineering tools
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<ul>
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<li> coverage analysis
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<li> automatic testing
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</ul>
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<li> literate Mercury
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<li> implement a GUI library (eg Hugs - Fudgets)
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<li> profiling guided optimisations
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<ul>
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<li> use profiling information to direct linker for optimal
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code placement (Alpha has a tool for this).
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</ul>
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<li> use of attribute grammar technology
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(including visit sequence optimization)
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to implement code with circular modes
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</ul>
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<hr>
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<!--======================-->
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Last update was $Date: 2010-07-13 05:48:04 $ by $Author: juliensf $@cs.mu.oz.au. <br>
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</body>
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</html>
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