Improving the Int/Word story inside GHC

Johan Tibell johan.tibell at
Thu Aug 7 15:01:42 UTC 2014

On Thu, Aug 7, 2014 at 4:36 PM, Simon Marlow <marlowsd at> wrote:
> I think doing the comparison with Integer is the right fix.  Relying on Word
> being big enough for these things is technically wrong because we might be
> cross-compiling from a smaller word size.

That sounds like an easier fix and I will try that. Unfortunately
working with Integers means lots of our convenience functions, such as
wordsToBytes, go out the window, as the all work on Byte/WordOff.
Here's an example that now gets more annoying:

    shouldInlinePrimOp dflags NewArrayOp [(CmmLit (CmmInt n _)), init]
      | wordsToBytes dflags (fromInteger n) <= maxInlineAllocSize dflags =

Most of our array primops are likely* still wrong, as the code that
generates them uses Int everywhere. Still also sounds like a problem
for cross-compiling.

* In some cases we might be lucky and the Int is never introspected
any we just look at the bits (i.e. pretend it's a Word) when we
generate code.

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