Proposal: provide cas and barriers symbols even without -threaded

[Carter Schonwald]

I guess I should find the time to finish the CAS primop work I volunteered
to do then. Ill look into in a few days.

On Friday, July 19, 2013, Simon Marlow wrote:

> On 18/07/13 14:17, Ryan Newton wrote:
>
>> The "atomic-primops" library depends on symbols such as
>> store_load_barrier and "cas", which are defined in SMP.h.  Thus the
>> result is that if the program is linked WITHOUT "-threaded", the user
>> gets a linker error about undefined symbols.
>>
>> The specific place it's used is in the 'foreign "C"' bits of this .cmm
>> code:
>>
>> https://github.com/rrnewton/**haskell-lockfree-queue/blob/**
>> 87e63b21b2a6c375e93c30b98c28c1**d04f88781c/AtomicPrimops/**
>> cbits/primops.cmm<https://github.com/rrnewton/haskell-lockfree-queue/blob/87e63b21b2a6c375e93c30b98c28c1d04f88781c/AtomicPrimops/cbits/primops.cmm>
>>
>> I'm trying to explore hacks that will enable me to pull in those
>> functions during compile time, without duplicating a whole bunch of code
>> from the RTS.  But it's a fragile business.
>>
>> It seems to me that some of these routines have general utility.  In
>> future versions of GHC, could we consider linking in those routines
>> irrespective of "-threaded"?
>>
>
> We should make the non-THREADED versions EXTERN_INLINE too, so that there
> will be (empty) functions to call in rts/Inlines.c.  Want to submit a patch?
>
> A better solution would be to make them into primops.  You don't really
> want to be calling out to a C function to implement a memory barrier. We
> have this for write_barrier(), but none of the others so far.  Of couse
> that's a larger change.
>
> Cheers,
>         Simon
>
>
>
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