APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

[Kevin McBride]

Everyone,

Please take notice that I am appealing my bug (number 23605) to the
steering committee of GCC on the basis that it is a legimate
bug/enhancement in need of a through research.  I believe that Andrew
Pinski is trying to keep the research from occuring by means of marking
the bug as invalid.

I am hoping that the steering committee will order a through research on
the bug.  There are times when it might be best to have things like
memset() inlined by the compiler itself, as outlined in my latest
comment to the bug.

- KJM


-------- Original Message --------
Subject: [Bug target/23605] memset() Optimization on x86-32 bit
Date: 28 Aug 2005 22:21:15 -0000
From: pinskia at gcc dot gnu dot org <gcc-bugzilla@gcc.gnu.org>
Reply-To: gcc-bugzilla@gcc.gnu.org
To: kevin@planetsaphire.com
References: <20050828200424.23605.kevin@planetsaphire.com>


------- Additional Comments From pinskia at gcc dot gnu dot org
2005-08-28 22:21 -------
First it is not our bug your distro installs i686 versions, go bug them
instead.
Second glibc not using SSE is its bug and not ours, report it to them
instead.

-- 
            What    |Removed                     |Added
----------------------------------------------------------------------------
              Status|UNCONFIRMED                 |RESOLVED
          Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23605

------- You are receiving this mail because: -------
You reported the bug, or are watching the reporter.

Re: APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

[Daniel Berlin]

On Sun, 2005-08-28 at 18:48 -0400, Kevin McBride wrote:
> Everyone,
> 
> Please take notice that I am appealing my bug (number 23605) to the
> steering committee of GCC on the basis that it is a legimate
> bug/enhancement in need of a through research. 


The Steering committee really doesn't get involved in bug reports.

Your only recourse is public shaming.
Sorry.

Re: APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

[Ian Lance Taylor]

Kevin McBride <kevin@planetsaphire.com> writes:

> Please take notice that I am appealing my bug (number 23605) to the
> steering committee of GCC on the basis that it is a legimate
> bug/enhancement in need of a through research.  I believe that Andrew
> Pinski is trying to keep the research from occuring by means of marking
> the bug as invalid.
> 
> I am hoping that the steering committee will order a through research on
> the bug.  There are times when it might be best to have things like
> memset() inlined by the compiler itself, as outlined in my latest
> comment to the bug.

I'm sure we all look forward to receiving orders from the steering
committee.

As pinskia noted, later, in the PR, you want the
-minline-all-stringops option, which is documented.


In the meantime, I think there may be a bug here, in that memset is
open coded for the i386 at -O0.  That doesn't make sense to me; e.g.,
it prevents setting a breakpoing on memset.  This happens in this
conditional in ix86_expand_clrmem:

  if ((!optimize || optimize_size)
      && (count == 0
	  || ((count & 0x03)
	      && (!optimize_size || (count & 0x03) + (count >> 2) > 7))))
    /* do cld; stos */

This conditional dates back to here:

Tue Jan 11 16:26:47 MET 2000  Jan Hubicka <jh@suse.cz>

	...
	(cld pattern): New.
	(movstrsi, clrstr, cmpstr, strlen expander): Emit cld instruction
	(movstrsi_1, clrstrsi_1, cmpstrsi_1, strlensi_1,
	cmpstrsi_nz_1 insn): Do not output cld instruction

Any thoughts on this?

Ian

Re: APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

[Richard Henderson]

On Sun, Aug 28, 2005 at 04:29:56PM -0700, Ian Lance Taylor wrote:
> In the meantime, I think there may be a bug here, in that memset is
> open coded for the i386 at -O0.  That doesn't make sense to me; e.g.,
> it prevents setting a breakpoing on memset.

This, IMO, has nothing to do with i386.  If we don't want to open-code
memset at -O0, we should have avoided transforming this such that we
call to clear_storage in the first place.


r~

Re: APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

[Joe Buck]

On Sun, Aug 28, 2005 at 06:48:17PM -0400, Kevin McBride wrote:
> Please take notice that I am appealing my bug (number 23605) to the
> steering committee of GCC on the basis that it is a legimate
> bug/enhancement in need of a through research.  I believe that Andrew
> Pinski is trying to keep the research from occuring by means of marking
> the bug as invalid.

I've looked at the bug in bugzilla; it's not marked as invalid, though
I tend to agree with Andrew and Ian's comments in the log.

In any case, the SC doesn't get involved in cases like this.  And even
if the SC lost its sanity and decided to micromanage Bugzilla as you
ask, it would take a 3/4 vote, and you certainly wouldn't get mine.

[DEAD] APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

[Kevin McBride]

Joe Buck wrote:
> I've looked at the bug in bugzilla; it's not marked as invalid, though
> I tend to agree with Andrew and Ian's comments in the log.

I set the bug back to unconfirmed after I noticed that, in my opinion, 
there can be more optimization done.

> In any case, the SC doesn't get involved in cases like this.  And even
> if the SC lost its sanity and decided to micromanage Bugzilla as you
> ask, it would take a 3/4 vote, and you certainly wouldn't get mine.

I didn't realize that the SC had no control over Bugzilla.  Unless there 
was something I missed, all what the web site said was:

 > In April 1999 the steering committee was appointed by the FSF as the
 > official GNU maintainer for GCC and changed its name to GCC steering
 > committee.

All I can now say is:

If no one on the GCC team wants to fully investigate my bug, then 
there's nothing I can do about the bug except to implement the fix in my 
own code.

This appeal started up over misunderstandings between Andrew Pinski, Ian 
Lance Taylor, and I.  I felt that Ian Lance Taylor agreed with me prior 
to submitting the bug to the bug tracker, and so, felt humiliated by 
Andrew Pinski's comments.  When Ian Lance Taylor stepped in, he made the 
misunderstanding obvious to me, and so, I did what I could to see if gcc 
was performing optimizations as much as possible.

This appeal is now dead.  Let's get on with our projects, regardless if 
my bug report will ever be turned into a bug fix.


- KJM

Re: [DEAD] APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

[Daniel Berlin]

On Mon, 2005-08-29 at 01:33 -0400, Kevin McBride wrote:
> Joe Buck wrote:
> > I've looked at the bug in bugzilla; it's not marked as invalid, though
> > I tend to agree with Andrew and Ian's comments in the log.
> 
> I set the bug back to unconfirmed after I noticed that, in my opinion, 
> there can be more optimization done.
> 
> > In any case, the SC doesn't get involved in cases like this.  And even
> > if the SC lost its sanity and decided to micromanage Bugzilla as you
> > ask, it would take a 3/4 vote, and you certainly wouldn't get mine.
> 
> I didn't realize that the SC had no control over Bugzilla.  Unless there 
> was something I missed, all what the web site said was:
> 
>  > In April 1999 the steering committee was appointed by the FSF as the
>  > official GNU maintainer for GCC and changed its name to GCC steering
>  > committee.

Yes, they control the overall direction.
They don't micromanage.

> 
> All I can now say is:
> 
> If no one on the GCC team wants to fully investigate my bug, then 
> there's nothing I can do about the bug except to implement the fix in my 
> own code.

If you want to see what's up, feel free. Nobody will stop you.  If you
want to propose a patch, feel free.

As for "no one on the GCC team", you seem to have a misunderstanding
about how GCC ends up working.  It's not like we have people paid who go
through all the enhancement requests or something.  The fact that the
bugs are in Bugzilla is just a way to track bugs.  It does not in any
way guarantee that your bug will be looked at, regardless of whether it
is open, closed, invalid, not invalid, etc.  There is no guarantee that
your bug will or won't be fixed for a certain release, etc, unless *you*
start submitting the patches to fix it.  Certainly, there are certain
classes of bugs that are more likely to be looked at than others, etc.
In addition, there are some people who are more attentive to certain
pieces of the compiler than others, and will go looking for enhancement
requests in bugzilla to fix.  This is not by stretch of the imagination
something that people do across the board.

In other words, the best way to get a bug attention is generally to give
that bug attention yourself.  

The other day we had someone who believed that if we marked his bug
"enhancement" instead of "minor", it was "misclassifying" and would
cause havoc.  The reality is that nobody was going to fix his bug
anytime soon, regardless of how it was marked, because he wasn't going
to, and it just wasn't high priority.


> 
> This appeal started up over misunderstandings between Andrew Pinski, Ian 
> Lance Taylor, and I.  I felt that Ian Lance Taylor agreed with me prior 
> to submitting the bug to the bug tracker, and so, felt humiliated by 
> Andrew Pinski's comments. 

At the risk of Andrew hating me (:P), this, sadly, is not the first time
someone has taken offense at his comments in a bug.  You shouldn't take
it personally.


>  When Ian Lance Taylor stepped in, he made the 
> misunderstanding obvious to me, and so, I did what I could to see if gcc 
> was performing optimizations as much as possible.
> 
> This appeal is now dead.  Let's get on with our projects, regardless if 
> my bug report will ever be turned into a bug fix.

Again, if you want a bug fix, your best course of action is to fix it :)

Re: APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

[Mike Stump]

On Aug 28, 2005, at 3:48 PM, Kevin McBride wrote:
> Please take notice that I am appealing my bug (number 23605) to the
> steering committee of GCC on the basis that it is a legimate
> bug/enhancement in need of a through research.

Ok, so go research it, collect data, and then report your findings  
back.  For example, benchmark an entire linux distro with your patch  
in and out, and tell us what the performance is, go measure spec,  
tell us what the performance is, benchmark CSiBE...

> I am hoping that the steering committee will order a through research

You have been so ordered, let us know how it goes.  :-)

> on the bug.


Another approach would be to take definitive measurements, for  
example, at -Os if one way is 30 bytes and the current approach gcc  
takes is 31 bytes, then that is a `bug'.

If you can show that a testcase takes fewer clock cycles and is  
smaller than the current codegen, file _that_ bug, include the  
numbers of ticks for each, give details, a vague, I wonder if this is  
better, isn't going to be as persuasive as hard numbers.

Failing all that you can appeal by hiring someone that will do the  
research, and report back their findings.

I hope this helps.

Re: APPEAL to steering committee: [Bug target/23605] memset() Optimization on x86-32 bit

[Joe Buck]

On Sun, Aug 28, 2005 at 06:48:17PM -0400, Kevin McBride wrote:
> I am hoping that the steering committee will order a through research on
> the bug. 

Kevin, what you don't seem to understand is that the SC can't order
anyone to do anything.  The SC has no employees, doesn't sign paychecks.
GCC is a volunteer organization.  True, a number of contributors draw a
salary from their companies for their GCC work, but their management, not
the SC, tells them what to work on.

The SC does have some powers: it can refuse to allow certain kinds of
changes into GCC, approves release plans put forward by the release
manager, and approves the people who will be maintainers to various parts
of the compiler.  Once in its entire history, the SC banned someone from
its mailing lists (this was back in the egcs days, and the guy was a
complete whacko who made escalating threats against the release manager,
including "I'm going to force your company to fire you" and "I've found out
where you live"). 

But even if the SC were persuaded that you are entirely correct, the most
it could do would be to ask for a volunteer to research your bug.  And
your bug is only one of 3,114 currently open gcc bugs (according to a
Bugzilla query I just did), and I am unpersuaded that it is a particularly
important one.