[MLton-devel] nucleic benchmark times

[Suresh Jagannathan]

> Here's what I think the interesting questions are.
>
> 1. Can we modify B to correctly implement SML semantics?  From gcc's
> perspective, compiling with B, which has a jo to an error after each
> arithmetic instruction, should produce identical performance to a
> hypothetical variant that has a jo to a handler, if only we could tell
> gcc where to go.  I know that we've thought about how to do this
> several times before, but in light of the numbers, I think it's worth
> thinking about again.  Maybe we could jo somewhere that looks at the C
> stack + some globals that we stash and figures out where to go?
>
> 2. Can we provide gcc aliasing information?  I ask this because I
> doubt that gcc is figuring out much, if any, of what we know.  If so,
> and it is already doing so well, imagine how much more improvement
> there is to be had by combining gcc's optimizer with our aliasing
> info.
>3. Can we hook into a gcc machine-independent IL?  A yes here would
presumably help with (1) and (2), give us good performance, and help a
lot with portability (and performance there too).  Although messy, I
view tying ourselves to gcc's IL a much more palatable alternative
than C--, MLRISC, ....

As you imply (1) and (2) are orthogonal, and any improvements made to
improve C's aliasing information would help in both an implementation 
that detects overflow or one that doesn't.  The critical issue in my opinion
is (1) -- both B and C don't conform to SML semantics, while A does, but
is significantly slower.    It seems that if a variant of A that captures most
of the performance of native using various optimization and code-generation
tricks could be constructed, we'd be in the best position to leverage further
improvements in aliasing info, machine-independent IL's etc.

Re. Reppy and MacQueen -- I'm neutral about having a larger meeting, although
quite positive about you giving a talk at UC.  I think three hours to discuss 
anything of substance is too short, but it's too long to exchange 
pleasantries.   On the other hand, if you gave a talk, you'd probably be 
better able to focus the discussion a bit better when you meet with them
individually.


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