On Tuesday, 18 August 2015 at 21:55:26 UTC, Walter Bright wrote:
On 8/18/2015 2:33 PM, deadalnix wrote:
There is none. There is a ton of 0.5% one that adds up to the
30% difference.
I regard a simple pattern that nets 0.5% as quite a worthwhile
win. That's only 60 of those to make up the difference.
If you've got any that you know of that would net 0.5% for dmd,
lay it on me!
If I'd were to bet on what would impact DMD perfs the most,
I'd go for SRAO, and
a inliner in the middle end that works bottom up :
- Explore the call graph to-down optimizing functions along
the way
- Backtrack bottom-up and check for inlining opportunities.
- Rerun optimizations on the function inlining was done in.
That's how the inliner already works. The data flow analysis
optimizer also runs repeatedly as each optimization exposes
more possibilities. The register allocator also runs repeatedly.
My understanding is that the inliner is in the front end. This
definitively do not work the way I describe it here.
(I am unfamiliar with the term SRAO. Google comes up with
nothing for it.)
That is because I made a typo, sorry.
It stand for 'scalar replacement of aggregate' aka SROA (not
SRAO).
You can find literature on the subject.
It require a fair amount of tweaking and probably need a way
for the backends to
provide a cost heuristic for various functions,
A cost heuristic is already used for the inliner (it's in the
front end, in 'inline.d'). A cost heuristic is also used for
the register allocator.
I'm not sure how this can be made to work the way I describe it
in the frontend.
