Hi Simon,

I have been inspecting what gcc generates and found that in all the functions I checked which used the thread status in a switch, none of them generated jump tables, rather, long chains of cmp's.

I predict this is because there are overlapping cases (or even a fall-through in one I saw, which looked accidental...).

On Tue, Jul 22, 2014 at 5:32 AM, Simon Marlow <marlowsd@gmail.com> wrote:

On 19/07/2014 06:00, Kyle Van Berendonck wrote:

I found these:
https://github.com/ghc/ghc/blob/5f3c5384df59717ca8013c5df8d1f65692867825/includes/rts/Constants.h#L194

They go only 0-14, so there's some long chains of branches and stuff in
hot paths that could be cleaned up into single &-masked branches by
changing these into a set of flags.

GHC will generate a table jump for a large dense case, if that's what you're worried about.

Cheers,
Simon