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Re: gcc 3.0.1 & C++ ABI issues
- To: Nathan Sidwell <nathan at codesourcery dot com>
- Subject: Re: gcc 3.0.1 & C++ ABI issues
- From: Mark Mitchell <mark at codesourcery dot com>
- Date: Mon, 06 Aug 2001 11:20:24 -0700
- cc: "gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>, "jason at redhat dot com" <jason at redhat dot com>
--On Monday, August 06, 2001 07:10:44 PM +0100 Nathan Sidwell
> Note: The patch disables RVO for empty classes with non-trival copy-ctor.
> We lose an optimization (for a rather rare case, I guess), and gain
> correct code. To get RVO back the real fix is to teach MODIFY_EXPR and
> INIT_EXPR about empty classes in the common backend, I think. But
> we're time constrained here.
Correct code is clearly more important. So, the patch is OK, but you
should XFAIL the testcase, and enter a PR about it. Since the RVO is
new (on the 3.1 branch) there's no regression here relative to any
released version of GCC.
> This is somewhat stronger that we do right now isn't it?
Yes. Ideally, the RVO would work on the CFG -- although we should
see whether or not that will really buy us much in the way of
additional performance before bothering.
Mark Mitchell email@example.com
CodeSourcery, LLC http://www.codesourcery.com