From: Chris Lattner <sabre@nondot.org>
To: Andrew Haley <aph@redhat.com>
Cc: Zack Weinberg <zack@codesourcery.com>, <Richard.Earnshaw@arm.com>,
Jim Wilson <wilson@specifixinc.com>, <gcc-patches@gcc.gnu.org>
Subject: Re: avoid unnecessary register saves for setjmp
Date: Thu, 27 Nov 2003 09:43:00 -0000 [thread overview]
Message-ID: <Pine.LNX.4.44.0311270320300.28662-100000@nondot.org> (raw)
In-Reply-To: <16325.49560.414002.838896@cuddles.cambridge.redhat.com>
On Thu, 27 Nov 2003, Andrew Haley wrote:
> > Not at all. For example, somewhat confusingly, the LLVM->C backend
> > actually turns "stack unwinding" operations into setjmp/longjmp
> > calls. This is basically equivalent to SJLJ exception handling,
> > with all of it's problems, but the point is that you don't _NEED_
> > to include an unwinder.
>
> Well, okay: the front end has turned sjlj into exceptions, and the
> back end has turned it all back again.
It _can_ turn it all back again. SJLJ is a horribly inefficient way to
implement exceptions in a C++ type of world (lots of dtors to run, catch
blocks, exception specs to check, etc). For C it's probably fine.
> We get the advantage of better analysis in the middle. No problem
> there; I am only referring to user-visible changes.
As far as user visible changes, the biggest problem is the change in ABI.
-Chris
--
http://llvm.cs.uiuc.edu/
http://www.nondot.org/~sabre/Projects/
next prev parent reply other threads:[~2003-11-27 9:21 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-11-27 9:19 Chris Lattner
2003-11-27 9:21 ` Andrew Haley
2003-11-27 9:22 ` Chris Lattner
2003-11-27 9:39 ` Andrew Haley
2003-11-27 9:43 ` Chris Lattner [this message]
2003-11-27 10:14 ` Zack Weinberg
2003-11-27 10:15 ` Chris Lattner
2003-11-27 11:01 ` Zack Weinberg
2003-11-27 20:28 ` Chris Lattner
2003-11-27 20:51 ` Gabriel Dos Reis
2003-11-27 15:41 ` Jan Vroonhof
2003-11-27 16:23 ` Jan Vroonhof
2003-11-27 10:31 ` Andrew Haley
2003-11-27 10:53 ` Zack Weinberg
[not found] <5cad8ef043da68f2a3332f00bd6a186a3fc6195b@mail.esmertec.com>
2003-11-27 20:44 ` Chris Lattner
-- strict thread matches above, loose matches on Subject: below --
2003-11-22 4:13 Richard Kenner
2003-12-01 3:29 ` Jim Wilson
2003-11-21 5:54 Jim Wilson
2003-11-21 18:39 ` Daniel Jacobowitz
2003-11-22 0:22 ` Jim Wilson
2003-11-22 3:57 ` Daniel Jacobowitz
2003-11-22 9:06 ` Jim Wilson
2003-11-22 14:37 ` Richard Earnshaw
2003-11-22 16:33 ` Daniel Jacobowitz
2003-11-27 9:11 ` Zack Weinberg
2003-11-27 17:11 ` Andrew Pinski
2003-11-27 18:23 ` Zack Weinberg
2003-11-28 5:15 ` Geert Bosch
2003-11-28 11:14 ` Richard Earnshaw
2003-11-28 14:02 ` Richard Earnshaw
2003-11-21 20:14 ` Geoff Keating
2003-11-22 0:20 ` Jim Wilson
2003-11-30 9:23 ` Jim Wilson
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