[project @ 2001-12-07 11:34:48 by sewardj]
Change the story on shifting primops: SllOp, SrlOp, ISllOp, ISraOp, ISrlOp. In the old primop story, these were implemented by C macros which checked that the shift amount did not exceed the word size, and if so returns a suitable value (0 or -1). This gives consistent, defined behaviour for any shift amount. However, these checks were not implemented on the NCG route, an inconsistency. New story: these primops do NOT check their args; they just do the shift. Shift values >= word size give undefined results. To reflect this, their Haskell names have been prefixed with 'unchecked'. The checks are now done on the Bits instances in the Prelude. This means all code generation routes are consistently checked, and hopefully the simplifier will remove the checks for literal shift amounts. I have tried to fix up the implementation for 64-bit platforms too, but not having one to hand, I don't know if it will work as-is.