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From: Tristan Gingold <gingold@adacore.com>
To: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: [patch] dwarf2out: Drop the size + performance overhead of DW_AT_sibling
Date: Wed, 12 Oct 2011 14:59:00 -0000	[thread overview]
Message-ID: <75BB5328-587F-4704-82EB-C1F8936CF8F2@adacore.com> (raw)
In-Reply-To: <20111012135008.GA24037@host1.jankratochvil.net>


On Oct 12, 2011, at 3:50 PM, Jan Kratochvil wrote:

> Hi,
> 
> dropping the optional DWARF attribute DW_AT_sibling has only advantages and no
> disadvantages:
> 
> For files with .gdb_index GDB initial scan does not use DW_AT_sibling at all.
> For files without .gdb_index GDB initial scan has 1.79% time _improvement_.
> For .debug files it brings 3.49% size decrease (7.84% for rpm compressed files).
> 
> I guess DW_AT_sibling had real performance gains on CPUs with 1x (=no) clock
> multipliers.  Nowadays mostly only the data size transferred over FSB matters.
> 
> I do not think there would be any DWARF consumers compatibility problems as
> DW_AT_sibling has always been optional but I admit I have tested only GDB.

I fear that this may degrade performance of other debuggers.  What about adding a command line option ?

Tristan.

  reply	other threads:[~2011-10-12 14:07 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-10-12 14:18 Jan Kratochvil
2011-10-12 14:59 ` Tristan Gingold [this message]
2011-10-12 15:28   ` Jan Kratochvil
2011-10-13 21:16     ` Jan Kratochvil
2011-10-14  9:36       ` Tristan Gingold
2011-10-14 14:18         ` Tom Tromey
2011-10-17  9:44           ` Tristan Gingold
2011-10-17 13:42             ` Tom Tromey
2011-10-18  8:39               ` Tristan Gingold
2011-10-18  9:03                 ` [patch#2] " Jan Kratochvil
2011-10-18  9:04                   ` Jakub Jelinek
2011-10-20 15:13                     ` Jan Kratochvil

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