Simon M, is the intention of ByteOff and WordOff that they should be able
to represent negative quantities as well? If so we might need to split it
into ByteOff (still an Int) and ByteIndex (a Word) to have a type for
indexing into arrays.
On Thu, Aug 7, 2014 at 1:16 PM, Edward Z. Yang
If it's strictly just in the codegen (and not affecting user code), seems fine to me.
Edward
Excerpts from Johan Tibell's message of 2014-08-07 12:10:37 +0100:
Inside GHC we mostly use Int instead of Word, even when we want to represent non-negative values, such as sizes of things or indices into things. This is now causing some grief in https://ghc.haskell.org/trac/ghc/ticket/9416, where an allocation boundary case test fails with a segfault because a n < m Int comparison overflows.
I tried to fix the issue by changing the type of maxInlineAllocSize, which is used on one side of the above comparison, to Word. However, that unravels a bunch of other issues, such as wordsToBytes, ByteOff, etc are all Int-valued quantities.
I could perhaps work around these problems by judicious use of fromIntegral in StgCmmPrim, but I'm a bit unhappy about it because it 1) makes the code uglier and 2) needs to be done in quite a few places.
How much work would it be to try to switch the codegen to use Word for most of these quantities instead?
-- Johan