[MLton] C-- backend

John Dias dias@eecs.harvard.edu
Tue, 4 Jul 2006 01:23:47 -0400 (EDT)

An excellent point. You can see the (non-final) design in section 11.2, 
and Cmm_CreateThread is even implemented. The big missing piece is the 
limitcheck. If you want to see an example from the qc-- test suite, you 
can take a look at the pair of files qc--/test2/src/factmain.c and 

On Mon, 3 Jul 2006, Matthew Fluet wrote:

> O.k., but the C-- spec (Section 8.3) doesn't give any specifics on how to 
> start a new stack going.
>> Well, to be more precise, qc-- supports multiple stacks, but it does not 
>> yet detect overflow.
>> -j
>> On Mon, 3 Jul 2006, Matthew Fluet wrote:
>>>> I was recently told that a C-- backend for MLton exists, but the newest
>>>> information I could find was from March of 2005.
>>> That is the most recent info in the mailing list.  I made a couple more 
>>> modifications to the backend in Summer 2005, when one of Norman Ramsey's 
>>> summer undergrad students was thinking about more efficient 
>>> representations of span data.
>>>> Targetting C-- would be pretty handy for us, because some of the 
>>>> optimizations involve weak continuations.  However, the last thing I read 
>>>> on the backend said that it still hasn't implemented callcc (among other 
>>>> features), so that might make things more difficult.
>>> Correct; the qc-- compiler doesn't currently support multiple stacks. 
>>> Since, to use C-- effectively, we aren't using the same trampoline as is 
>>> used in the C backend, there needs to be a C-- stack for every ML stack.
>>> A grad student was working on getting C-- and qc-- to support multiple 
>>> stacks, but I don't believe that they have been fully integrated yet.  And 
>>> they certainly haven't been pushed into the C-- backend.
>>>> I wanted to know what the current state of the C-- backend is, and 
>>>> if/where we could get the source code.
>>> The state is pretty much what was documented in the March 2005 emails. 
>>> (Modulo some bugs fixed in the qc-- compiler.)  It is still very 
>>> experimental, but you're welcome to check it out.  It is available in SVN 
>>> at:
>>>  svn://mlton.org/svnroot/mlton/branches/on-20050420-cmm-branch
>>> IIRC, in order to compile with qc-- using the C-- backend, you'll need to 
>>> copy the lib/qc-- files from the qc-- install directory to build/lib/self 
>>> in the mlton build.
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