From: Jason Merrill <jason@cygnus.com>
To: jfc@mit.edu (John Carr), egcs@cygnus.com
Subject: Re: increase in object code size
Date: Tue, 23 Sep 1997 18:32:00 -0000 [thread overview]
Message-ID: <u9zpp38pkw.fsf@yorick.cygnus.com> (raw)
In-Reply-To: <199709231845.OAA14441.cygnus.egcs@biohazard-cafe.MIT.EDU>
>>>>> John Carr <jfc@mit.edu> writes:
> The first optimization which comes to mind: an exception table entry
> which does not apply to an instruction which can throw an exception
> should be eliminated. In GNU C and C++ (and, I think, GNU Ada) only
> function calls throw exceptions. That means there needs to be at most
> one table entry per function call.
True. In general, the current output is precise at the cost of size. It
could be shrunk at the cost of precision. This is one case. Another would
be pretending that all the prologue stuff happened at the PC after the
prologue, so you only need one advance PC instruction.
> The second (x86 only): if a function does not have any exception
> handlers and it has a frame pointer the unwinder does not need an
> exception table. The return PC is at a known offset from the frame
> pointer.
But how do you restore the saved registers? That's what the unwind info is
for.
Jason
next prev parent reply other threads:[~1997-09-23 18:32 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
1997-09-23 7:21 Thomas Koenig
1997-09-23 9:32 ` Joe Buck
1997-09-23 10:03 ` John Carr
1997-09-23 10:16 ` Joe Buck
[not found] ` <199709231716.KAA13154.cygnus.egcs@atrus.synopsys.com>
1997-09-23 10:34 ` Jason Merrill
1997-09-23 10:38 ` Joe Buck
1997-09-23 10:56 ` Thomas Koenig
1997-09-24 1:58 ` Jakub Jelinek
[not found] ` <199709231755.TAA00725.cygnus.egcs@mvmap66.ciw.uni-karlsruhe.de>
1997-09-23 11:23 ` Jason Merrill
1997-09-24 2:33 ` Torbjorn Lindgren
1997-09-23 11:45 ` John Carr
1997-09-23 17:03 ` Richard Henderson
1997-09-23 17:16 ` Joe Buck
1997-09-28 14:43 ` Joern Rennecke
[not found] ` <199709240001.RAA05779.cygnus.egcs@dot.cygnus.com>
1997-09-23 18:25 ` Jason Merrill
1997-09-23 22:08 ` Richard Henderson
1997-09-23 22:46 ` Jason Merrill
1997-09-23 22:56 ` David S. Miller
1997-09-24 0:11 ` Richard Henderson
[not found] ` <199709231845.OAA14441.cygnus.egcs@biohazard-cafe.MIT.EDU>
1997-09-23 18:32 ` Jason Merrill [this message]
1997-09-24 3:12 ` code size/ linux -fno-strength-reduce Mark Phillips
1997-09-29 7:08 ` Horst von Brand
[not found] <199709231643.KAA27118@harmony.village.org>
1997-09-23 10:05 ` increase in object code size Thomas Koenig
[not found] <199709232337.TAA00381@pincoya.inf.utfsm.cl>
1997-09-23 18:21 ` Jason Merrill
1997-09-24 7:13 ` Horst von Brand
1997-09-23 19:09 Mike Stump
1997-09-23 21:29 ` Joe Buck
1997-09-24 9:46 Mike Stump
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