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From: Jonathan Wakely <jwakely.gcc@gmail.com>
Date: Fri, 13 May 2022 19:16:00 +0100
Message-ID: <CAH6eHdSAr4xWwDmH_Byq-8my0GpgA3bsPiF=K5M8oyrRPvXwuw@mail.gmail.com>
Subject: Re: compile time of code using long tuples
To: "Foelsche, Peter" <Peter_Foelsche@mentor.com>
Cc: gcc-help <gcc-help@gcc.gnu.org>
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On Fri, 13 May 2022, 19:13 Foelsche, Peter, <Peter_Foelsche@mentor.com>
wrote:

> I'm the author of some software which dumps out C++ code to be compiled
> with g++.
> This code sometimes contains many different and many long tuples. I
> deduced that long tuples cause rather long compile times.
> I already wrote some compression, which collects identical entries in such
> a tuple and moves them into an array.
> But this compression reduces (run-time) performance.
> I already wrote different tuple implementations, and one of the compiles
> much faster than the regular provided std::tuple.
> What could be the criterium for such a tuple implementation, which makes
> g++ take more or less compile time assuming the same code using this tuple?
>

Identical object layout on all targets, meaning size, alignment, base-class
order, etc. It needs to be ABI-compatible.