On 2014-01-13 at 21:57:03 +0100, Simon Marlow wrote: > On 13/01/14 13:25, g...@git.haskell.org wrote: >> Repository : ssh://g...@git.haskell.org/integer-gmp >> >> On branch : master >> Link : >> http://ghc.haskell.org/trac/ghc/changeset/7bdcadda7e884edffb1427f0685493f3a2e5c5fa/integer-gmp >> >>> --------------------------------------------------------------- >> >> commit 7bdcadda7e884edffb1427f0685493f3a2e5c5fa >> Author: Herbert Valerio Riedel <h...@gnu.org> >> Date: Thu Jan 9 00:19:31 2014 +0100 >> >> Allocate initial 1-limb mpz_t on the Stack and introduce MPZ# type >> >> We now allocate a 1-limb mpz_t on the stack instead of doing a more >> expensive heap-allocation (especially if the heap-allocated copy becomes >> garbage right away); this addresses #8647. > > While this is quite cool (turning some J# back into S#), I don't > understand why you've done it this way. Couldn't it be done in the > Haskell layer rather than modifying the primops? The ByteArray# has > already been allocated by GMP, so you don't lose anything by returning > it to Haskell and checking the size there. Then all the > DUMMY_BYTEARRAY stuff would go away.
Actually there isn't always a ByteArray# allocated; the patch got rid of all mpz_init() calls for the result-mpz_t (which would have allocated 1-limb ByteArray#s); Now instead, the single word-sized limb that would have been heap-allocated via mpz_init() before calling the actual GMP operation, is allocated on the stack instead, and only if the GMP routines need to grow the passed in mpz_t's an actual ByteArray# is allocated. That's why I needed a way to return either a single stack-allocated limb (hence the word#), *or* an heap-allocated 'ByteArray#', which lead to the MPZ# 3-tuple. Greetings, hvr _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://www.haskell.org/mailman/listinfo/ghc-devs
