On Friday, 14 October 2016 at 11:53:55 UTC, Andrei Alexandrescu wrote:
On 10/14/2016 07:51 AM, Johan Engelen wrote:
On Friday, 14 October 2016 at 11:17:55 UTC, Andrei Alexandrescu wrote:
On 10/14/2016 05:24 AM, Johan Engelen wrote:
I like "hints".


How many other hints are out there? -- Andrei

Things that come to mind:
- this value is probably X  (bool, int, pointer)

These would be all covered by __builtin_expect or similar.

For LLVM, not (yet?) for pointers (there is not builtin for the is_likely template that I posted).

- this type is probably Y
- this function is likely hot/cold (UDA)
- this data is likely to be accessed soon (_could_ lead to a prefetch) - this member field is hot/cold (iirc, Class members may be re-ordered)
(UDA)

Any of these present in existing implementations?

I only know about LLVM/LDC.
- type is probably Y: No. It can be used for devirtualization (similar to the fptr optimization), and I have implemented it in LDC using profiling data (it's not in master).
- function hotness: No, but trivially added.
- data prefetching: Yes.
- member field hotness + reordering: No, but it is easy to imagine how to implement it.

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