how to write a ghc primop that acts on an unevaluated argument?
Hey All, as part of trying to get some fixups for how prefetch works into 7.10, i'm adding a "prefetchValue" primop that prefetchs the memory location of a lifted heap value namely several operations of the following form primop PrefetchValueOp1 "prefetchValue1#" GenPrimOp a -> State# s -> State# s with strictness = { \ _arity -> mkClosedStrictSig [botDmd, topDmd] topRes } I'd like some feedback on the strictness information design by someone who's familiar with how that piece of GHC. the idea being that prefetchValue is lazy in its polymorphic argument (it doesn't force it, it just does a prefetch on the heap location, which may or may not be evaluated). https://phabricator.haskell.org/D350 is the code in question. And i *believe* i'm testing for being lazy in that argument correctly. thoughts? many thanks! -Carter
Maybe test for laziness in the argument by just putting something in that goes boom when forced, e.g. 'undefined'? On Sun, Nov 23, 2014 at 2:04 PM, Carter Schonwald < carter.schonwald@gmail.com> wrote:
Hey All, as part of trying to get some fixups for how prefetch works into 7.10, i'm adding a "prefetchValue" primop that prefetchs the memory location of a lifted heap value
namely
several operations of the following form
primop PrefetchValueOp1 "prefetchValue1#" GenPrimOp a -> State# s -> State# s with strictness = { \ _arity -> mkClosedStrictSig [botDmd, topDmd] topRes }
I'd like some feedback on the strictness information design by someone who's familiar with how that piece of GHC. the idea being that prefetchValue is lazy in its polymorphic argument (it doesn't force it, it just does a prefetch on the heap location, which may or may not be evaluated).
https://phabricator.haskell.org/D350
is the code in question. And i *believe* i'm testing for being lazy in that argument correctly.
thoughts?
many thanks! -Carter
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yup, i have that!
wrapFetch prefetchValue0# (error "this shouldn't get evaluated")
in the test suite!
in contrast
wrapFetch prefetchValue0# $! (error "this shouldn't get evaluated")
does explode
shall I add a "should fail" test with the latter? (it doesn't seem
worthwhile)
On Sun, Nov 23, 2014 at 3:53 PM, Edward Kmett
Maybe test for laziness in the argument by just putting something in that goes boom when forced, e.g. 'undefined'?
On Sun, Nov 23, 2014 at 2:04 PM, Carter Schonwald < carter.schonwald@gmail.com> wrote:
Hey All, as part of trying to get some fixups for how prefetch works into 7.10, i'm adding a "prefetchValue" primop that prefetchs the memory location of a lifted heap value
namely
several operations of the following form
primop PrefetchValueOp1 "prefetchValue1#" GenPrimOp a -> State# s -> State# s with strictness = { \ _arity -> mkClosedStrictSig [botDmd, topDmd] topRes }
I'd like some feedback on the strictness information design by someone who's familiar with how that piece of GHC. the idea being that prefetchValue is lazy in its polymorphic argument (it doesn't force it, it just does a prefetch on the heap location, which may or may not be evaluated).
https://phabricator.haskell.org/D350
is the code in question. And i *believe* i'm testing for being lazy in that argument correctly.
thoughts?
many thanks! -Carter
_______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://www.haskell.org/mailman/listinfo/ghc-devs
participants (2)
-
Carter Schonwald -
Edward Kmett