From: Segher Boessenkool <segher@kernel.crashing.org>
To: Dmitry Mikushin <dmitry@kernelgen.org>
Cc: David Edelsohn <dje.gcc@gmail.com>, Jeffrey Law <law@redhat.com>,
Qing Zhao <QING.ZHAO@oracle.com>, GCC <gcc@gcc.gnu.org>
Subject: Re: Does gcc automatically lower optimization level for very large routines?
Date: Fri, 20 Dec 2019 22:52:00 -0000 [thread overview]
Message-ID: <20191220225203.GI3152@gate.crashing.org> (raw)
In-Reply-To: <CAJoDaPYu8Wwb4PPSMQf4NMT9yog_tLzi2-cnmYHhxFCfs+x5pw@mail.gmail.com>
On Fri, Dec 20, 2019 at 02:57:57AM +0100, Dmitry Mikushin wrote:
> Trying to plan memory consumption ahead-of-work contradicts with the nature
> of the graph traversal. Estimation may work very well for something simple
> like linear or log-linear behavior.
Almost everything we do is (almost) linear.
> But many compiler algorithms are known
> to be polynomial or exponential
Many? There are a few (register allocation is a well-known example),
but anything more than almost linear is quite easy to make blow up. It
is also not super hard in most cases to make things linear, it just
needs careful attention.
> (or even worse in case of bugs).
Well, sure, if there is a bug *anything* can go wrong ;-)
Segher
next prev parent reply other threads:[~2019-12-20 22:52 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-19 16:37 Qing Zhao
2019-12-19 22:51 ` Dmitry Mikushin
2019-12-19 23:07 ` Qing Zhao
2019-12-20 0:41 ` Jeff Law
2019-12-20 1:32 ` David Edelsohn
2019-12-20 1:58 ` Dmitry Mikushin
2019-12-20 22:52 ` Segher Boessenkool [this message]
2019-12-20 23:00 ` Dmitry Mikushin
2019-12-20 11:13 ` Richard Biener
2019-12-20 16:05 ` Qing Zhao
2019-12-20 16:22 ` Jonathan Wakely
2020-01-01 5:25 ` Andi Kleen
2020-01-01 15:20 ` Segher Boessenkool
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