From: Alexandre Oliva <aoliva@redhat.com>
To: Bernd Schmidt <bernds@codesourcery.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: introduce --param max-vartrack-expr-depth
Date: Wed, 01 Jun 2011 20:09:00 -0000 [thread overview]
Message-ID: <oraae1xqpx.fsf@livre.localdomain> (raw)
In-Reply-To: <or7h96zw44.fsf@livre.localdomain> (Alexandre Oliva's message of "Tue, 31 May 2011 13:13:31 -0300")
On May 31, 2011, Alexandre Oliva <aoliva@redhat.com> wrote:
> On May 30, 2011, Bernd Schmidt <bernds@codesourcery.com> wrote:
>> On 05/30/2011 12:35 PM, Alexandre Oliva wrote:
>>> One of my patches for PR 48866 regressed guality/asm-1.c on
>>> x86_64-linux-gnu because what used to be a single complex debug value
>>> expression became a chain of debug temps holding simpler expressions,
>>> and this chain exceeded the default recursion depth in resolving
>>> location expressions.
>> What's the worst that can happen if you remove the limit altogether?
> Exponential behavior comes to mind.
It's unusual, but debug/pr41264-1.c exhibits it, given INT_MAX for the
param, even though under such a (lack of) limit bootstrap doesn't go
slower or faster, after restoring depth 5 for the reverse_op() use. As
Jakub pointed out, that one probably shouldn't be affected by the
parameter, as depth 5 is exactly what we want for the kind of expression
we're looking for. With unlimited depth for that one, not even
libiberty/md5.c compiles successfully, exhausting memory on a box with
some 40GB of total VM (8+32).
So I guess I'll stick with what I checked in, but keep a patch handy to
bump the limit a little bit up and revert to 5 in reverse_op.
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Compiler Engineer
next prev parent reply other threads:[~2011-06-01 20:09 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-30 12:24 Alexandre Oliva
2011-05-30 12:30 ` Jakub Jelinek
2011-05-30 12:39 ` Bernd Schmidt
2011-05-31 17:47 ` Alexandre Oliva
2011-05-31 18:16 ` Jakub Jelinek
2011-06-01 20:09 ` Alexandre Oliva [this message]
2011-06-01 22:29 ` Alexandre Oliva
2011-06-02 8:47 ` Jakub Jelinek
2011-06-02 10:07 ` Bernd Schmidt
2011-06-03 1:42 ` Alexandre Oliva
2011-07-20 20:48 ` Michael Eager
2011-07-20 20:55 ` Jakub Jelinek
2011-07-20 21:00 ` Michael Eager
2011-07-20 21:04 ` Jakub Jelinek
2011-07-21 0:10 ` Michael Eager
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