Disclaimer: I am not an expert. But I happened to have been looking at this code just yesterday, so I’ll try to answer to check my understanding. :)
Fundamentally, a PAP is not fully-saturated, so the number of arguments in its payload may be smaller than the information contained in the function’s bitmap. scavenge_large_bitmap calls walk_large_bitmap, which uses the bitmap as a “ruler” to guide the traversal, lining up each element in the payload to information in the bitmap. But the traversal only actually walks a payload of the specified size, so if there’s less information in the payload than there is information in the bitmap, the traversal will just terminate early. > On Feb 14, 2020, at 09:30, Ömer Sinan Ağacan <omeraga...@gmail.com> wrote: > > Right, I think that's the problem. We then pass the same "size" to > scavenge_large_bitmap as the size of the bitmap. So we assume size of the > bitmap > is pap->n_args. > > So the call stack is > > - scavenge_PAP, calls scavenge_PAP_payload with pap->n_args as "size" > - scavenge_PAP_payload, calls scavenge_large_bitmap with "size" (== > pap->n_args) > as the bitmap's size > > Is this expected? > > Ömer _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
