-Problems:
+$Id: TODO,v 1.2 1995/08/28 13:29:07 adams Exp $
+Problems:
-[] Stackopt is requitres too much storage. Investigate.
+[] Stackopt is requires too much storage. Investigate.
-[] Indexify should be dropped. For large programs, fully 32% of the
+[DONE] Indexify should be dropped. For large programs, fully 32% of the
program (measured in pairs) is %vector-index expressions after
cleanup/4 (closconv/2 leaves it at about 25%).
+
+[] Teach dataflow about coerce-to-compiled-procedure
+
+[] Reorganize coerce to keep the expressions small and unconditional
+until much later. Perhaps the right thing is to treat
+coerce-to-compiled-procedure more like &+, expanding the in-line test
+late. An alternative is to have an assembly hook which creates a
+trampoline or closure which can be overwritten later with the correct
+value.
+
+[] Investigate replacing %stack-closure-ref by a STACK-REF special
+form. This would save 10 pairs per stack reference.
+
+[] Why is the new code not more than 12% faster than the old code?
+
+[] Move split earlier, to after applicat.
+
+[] Make split introduce closures with no code pointer as tuples.
+
+[] Make dataflow realize that is does not have enough heap space
+earlier. Keep track of the number of nodes allocated thus far. From
+this we can calculate the minimum space for the fully connected graph
+and give up if that much is not free after every GC.
+
+[] Dataflow might benefit from a class heirarchy for the nodes, rather
+than having to test a wierd combination of the form, name and type
+slots.
+
+[] Figure out a way to get some debugging information (even just an
+expression) into the `local' continuations. Getting an environment is
+harder but worth-while.
+
+[] Fix lamlift, split and friends to maintain alpha-conversion wrt
+extra stubs.
+
+[] Fix rtlgen to make internal procedures again. Bite the bullet.
+Prescan the whole program to see if a letrec label is used in a
+%make-trivial-closure.
+
+[] RTLGEN.
+
+RTLGEN should be rewritten in the following way to generate better
+code. (in an experiment ASSQ is 20% faster when done this way).
+
+ . generate call graph
+ . partition graph into DAGS by removing call edges. Prefer removing
+ edges that break loops, and then to procedures/continuations that
+ we already know require in interrupt check.
+ . Decide which procedures should have an interrupt check.
+ . if a procedure is called from only one DAG, and does not have an
+ interrupt check (e.g. by declaration) it may be implemented as a
+ label, with pseudo-register arguments. (perhaps this should be
+ decided before compat?)
+ . generate code for each DAG
+ - generate code for a node before any of its children. This is
+ required so that we have the preservation information available.
+ - collect allocation & stack statistics from children which do not
+ have their own heap/stack/interrupt checks.
+ . We now have the information to insert interrupt checks at the
+ decided places.
+
+ . at the same time fix the problem that is causing r#x13 to be copied
+ at every procedure entry.
+
+
+[] Incorporate RTL instruction scheduling
+
+
+Missing functionality
+
+[] Implement checked primitive procedures. This requires a preserving
+call to arbitrary primitives and debugging info for preservations.
+
+
+Implementation strategies
+
+[] Make all variables in the source code be represented by structures
+to allow instant lookup. Requires strict alpha conversion.
+
+
+Extra functionality
+
+[] Debugging information may be able to use the environment model for
+subproblems (deeper stack frames) in certain circumstances. Internal
+procedures that do not escape and are only called as subproblems
+(except for calling* themselves) from a fixed set of locations may be
+able to augment available information from these stack frames. (What
+we must guarantee is that the instance of the subproblem stack frame
+must the the same as the instance of the internal procedure's parent
+frame).
+
+[] Debugging information can be used to get values for
+(sub)expressions that have already been computed. For this to be
+useful we should remove expressions whose value is available as a
+binding (to avoid duplication, presumably frequent when the user has
+used LET to bind the value).
+
+[IN PROGRESS] Loop unrolling at KMP level.
+
+[] Declaration for controlling the generation of interrupt checks,
+heap checks and stack checks. Declaration also for ensuring that a
+procedure can be breakpointed?
+
+[] Declaration for more live debugging information, at the expense of
+performance. This can be implemented by bogus references to the user
+level bindings. Two logical places to do this: before lamlift/1 might
+cause extra closures to be generated, but gets all the bindings.
+After lamlift/1 might cause extra stack references, but doesnt
+generate closures and might miss those bindings. Unless done
+carefully this might cause lots of identity continuations.
+
+
+[] Condition tree improvements. Some kind of CSE on conditions to
+make up for RTL's lack of boolean `registers'. An open-coder for MEMQ
+in predicate position might be helpful.
+
+[] Make SF integrate more procedures as
+ (access <name> system-global-environment)
+Include anything from R4RS that we can improve.
+
+[] Make the unsyntaxer hide all the `spurrious' accesses introduced
+above. There should be a flag which when set, elides the access
+provided that the <name> would not be captured.
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