* efficiency
@ 2006-03-17 1:49 Bob Rossi
2006-03-17 1:58 ` efficiency Brian Budge
0 siblings, 1 reply; 4+ messages in thread
From: Bob Rossi @ 2006-03-17 1:49 UTC (permalink / raw)
To: gcc-help
Hi,
I'm currently writing a patch to bison, and can not afford to effect
it's efficiency.
Theoretically, a function in bison uses a local variable named "lfoo" and
a global variable named "gfoo". I need to pack both of these into a struct,
named "sfoo".
If the function currently uses the variables directly like 'lfoo = 0;',
will changing them to 'sfoo_obj->lfoo = 0;' effect the efficiency of the
program in regards to speed?
Thanks,
Bob Rossi
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: efficiency
2006-03-17 1:49 efficiency Bob Rossi
@ 2006-03-17 1:58 ` Brian Budge
2006-03-17 2:06 ` efficiency Bob Rossi
0 siblings, 1 reply; 4+ messages in thread
From: Brian Budge @ 2006-03-17 1:58 UTC (permalink / raw)
To: gcc-help
Hi -
This is not really a gcc question, and it should really be asked
elsewhere... however, it's unlikely that this occasional dereference
will adversely affect performance.
Brian
On 3/16/06, Bob Rossi <bob_rossi@cox.net> wrote:
> Hi,
>
> I'm currently writing a patch to bison, and can not afford to effect
> it's efficiency.
>
> Theoretically, a function in bison uses a local variable named "lfoo" and
> a global variable named "gfoo". I need to pack both of these into a struct,
> named "sfoo".
>
> If the function currently uses the variables directly like 'lfoo = 0;',
> will changing them to 'sfoo_obj->lfoo = 0;' effect the efficiency of the
> program in regards to speed?
>
> Thanks,
> Bob Rossi
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: efficiency
2006-03-17 1:58 ` efficiency Brian Budge
@ 2006-03-17 2:06 ` Bob Rossi
2006-03-17 13:23 ` efficiency Andrew Haley
0 siblings, 1 reply; 4+ messages in thread
From: Bob Rossi @ 2006-03-17 2:06 UTC (permalink / raw)
To: Brian Budge; +Cc: gcc-help
On Thu, Mar 16, 2006 at 05:58:29PM -0800, Brian Budge wrote:
> Hi -
>
> This is not really a gcc question, and it should really be asked
> elsewhere... however, it's unlikely that this occasional dereference
> will adversely affect performance.
OK, where should a question like this be asked? if not the compiler that
does the optimization? I forgot to mention, I only really care about the
efficiency regarding gcc's output.
Bob Rossi
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: efficiency
2006-03-17 2:06 ` efficiency Bob Rossi
@ 2006-03-17 13:23 ` Andrew Haley
0 siblings, 0 replies; 4+ messages in thread
From: Andrew Haley @ 2006-03-17 13:23 UTC (permalink / raw)
To: Bob Rossi; +Cc: Brian Budge, gcc-help
Bob Rossi writes:
> On Thu, Mar 16, 2006 at 05:58:29PM -0800, Brian Budge wrote:
> > Hi -
> >
> > This is not really a gcc question, and it should really be asked
> > elsewhere... however, it's unlikely that this occasional dereference
> > will adversely affect performance.
>
> OK, where should a question like this be asked? if not the compiler that
> does the optimization?
I agree with you, Bob -- it's a perfectly reasonable question.
> I forgot to mention, I only really care about the efficiency
> regarding gcc's output.
Well, if you really want to know, use "gcc -S".
Access to a local is something like
movl 8(%ebp), %eax
and to a global via a pointer
movl sfoo, %eax
movl 4(%eax), %eax
Andrew.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2006-03-17 13:23 UTC | newest]
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