This is the mail archive of the gcc@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]

Re: gcc 3.0.1 & C++ ABI issues




--On Monday, August 06, 2001 07:10:44 PM +0100 Nathan Sidwell 
<nathan@codesourcery.com> wrote:
> 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                mark@codesourcery.com
CodeSourcery, LLC            http://www.codesourcery.com


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]