Thread status constants

[Kyle Van Berendonck]

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 at gmail.com> wrote:

> On 19/07/2014 06:00, Kyle Van Berendonck wrote:
>
>> I found these:
>> https://github.com/ghc/ghc/blob/5f3c5384df59717ca8013c5df8d1f6
>> 5692867825/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
>
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