Bulat Ziganshin wrote:
Hello Thorkil,
Wednesday, March 29, 2006, 2:15:05 AM, you wrote:
Thorkil, i can't understand why you can't just use FFI to import
functions you required? why you need to patch the PrimOps list?
As I wrote earlier, using FFI is also a candidate for getting access to
additional GMP functions. However, presently, I am not aware of a method of
doing this that does not involve some potentially significant additional
overhead. After all, Haskell Integers are not directly supported in C, so
some sort of marshalling and/or intricate access to internal GHC Haskell
structures would seem to be required.
primitives work with just the same internal structures. i thinl that
only real advantage of adding primop instead of adding FFI import is
that PrimOps.cmm contains already implemented wrappers for calling GMP
functions while for FFI you should implement them from scratch
And primops can be constant folded (probably not important in this case,
though).
Also, because GMP operations need to allocate on the heap, special
considerations apply in a multithreaded setting. You can't call
allocation routines from a foreign call in general without either having
a Capability (allocateLocal()), or taking the storage manager lock
(allocate()). The primops have direct access to the current Capability,
so they can just call allocateLocal() and don't need any locking operations.
Cheers,
Simon
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