From: Jason Merrill <jason@redhat.com>
To: Nathan Sidwell <nathan@codesourcery.com>
Cc: Mark Mitchell <mark@codesourcery.com>,
Gabriel Dos Reis <gdr@codesourcery.com>,
Richard Henderson <rth@redhat.com>,
"gcc@gcc.gnu.org" <gcc@gcc.gnu.org>
Subject: Re: [tree-ssa] Simplifying TARGET_EXPR
Date: Mon, 22 Jul 2002 13:10:00 -0000 [thread overview]
Message-ID: <wvl65z7g89o.fsf@prospero.cambridge.redhat.com> (raw)
In-Reply-To: <3D3C1231.2F39DDC@codesourcery.com> (Nathan Sidwell's message of "Mon, 22 Jul 2002 15:09:53 +0100")
>>>>> "Nathan" == Nathan Sidwell <nathan@codesourcery.com> writes:
> Mark Mitchell wrote:
>> Maybe I'm developing an unhealthy paranoia. On the one hand,
>> optimizing away more copy constructors is like optimizing away
>> more copies between scalars, and I'm all for having -O2 do more
>> of that! On the other, copy constructor elision is observable
>> behavior in the program, and it's going to make it hard to do
>> debug, profile, and otherwise analyze your program if the number
>> of copy constructor calls changes when you optimize.
> I disagree. Alias analysis makes optimized broken programs hard
> to debug, I don't see why temporary elision is any different..
> Maybe have the elision separately disablable at -O2, but I think
> it should be permissable.
I agree. Copy constructor calls are small change in debuggability of
optimized code.
Of course, we've never tried to optimize away more copy constructors after
inlining, so this is all theoretical...
Jason
next prev parent reply other threads:[~2002-07-22 14:18 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-20 18:54 Jason Merrill
2002-07-21 0:41 ` Richard Henderson
2002-07-26 14:51 ` PATCH " Jason Merrill
2002-07-21 17:32 ` [tree-ssa] " Mark Mitchell
2002-07-21 18:04 ` Gabriel Dos Reis
2002-07-21 18:14 ` Mark Mitchell
2002-07-21 20:39 ` Gabriel Dos Reis
2002-07-22 8:32 ` Michael Matz
2002-07-22 12:02 ` Gabriel Dos Reis
2002-07-24 3:22 ` Mark Mitchell
2002-07-22 12:33 ` Nathan Sidwell
2002-07-22 12:53 ` Gabriel Dos Reis
2002-07-22 13:10 ` Jason Merrill [this message]
2002-07-21 22:35 ` Jason Merrill
-- strict thread matches above, loose matches on Subject: below --
2002-07-16 9:52 Jason Merrill
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