[fpc-devel] Question on updating FPC packages
florian at freepascal.org
Wed Oct 30 23:02:25 CET 2019
Am 29.10.19 um 14:06 schrieb Marco van de Voort:
> Op 2019-10-27 om 10:46 schreef Florian Klämpfl:
>> Am 27.10.19 um 10:27 schrieb Michael Van Canneyt:
>>> If you genuinely believe that micro-optimization changes can make a
>>> Submit patches.
>> As said: I am against applying them. Why? They clutter code and after
>> all, they make assumptions about the current target which not might be
>> always valid. And time testing them is much better spent in improving
>> the compiler and then all code benefits. Another point: for example
>> explicit inline increases normally code size (not always but often),
>> so it is against the use of -Os. Applying inline manually on umpteen
>> subroutines makes no sense. Better improve auto inlining.
> Auto inlining is also no panacea. It only works with heuristics, and
> is thus only as good as a formula of the heuristic.
Yes. And manually adding inline is only as good as the knowledge of the
user doing so. If somebody implements it right (I did not, I used the
easiest approach and used an existing function to estimate the
complexity of a subroutine). The compiler can just count the number of
the generate instructions or even calculate the length of the procedure
and then decide to keep the node tree for inlining.
> Changing calling conventions, vectorizing, loops all complicates that,
> and it will never be perfect, and a change here will lead to a problem
> there etc.
> If you know a routine can evaluate to one instruction in most cases, I
> don't see anything wrong with just marking it as such.
The compiler knows this as well as the compiler generated the code. Why
should I guess if the compiler knows?
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