Huh, I had heard frame pointer omission wasn't a huge optimization. We
turned it off to get reliable stacks off of our release builds. A quick
google doesn't mention much other than how to turn it off or that it
affects ebp. Does anyone have any numbers on performance, or in what
circumstances it makes a large difference?
By the way, in VS8.0 "Optimize for Speed" and "Optimize for Size" both
force enable frame pointer omission. From the docs:
"The /Ox (Full Optimization)
<http://msdn2.microsoft.com/en-us/library/59a3b321.aspx> (Full
Optimization) and /O1, /O2 (Minimize Size, Maximize Speed)
<http://msdn2.microsoft.com/en-us/library/8f8h5cxt.aspx> (Fast Code)
options imply */Oy*. Specifying */Oy–* after the */Ox*, */O1*, or */O2*
option disables */Oy*, whether it is explicit or implied."
-Dan
Kevin Wasserman wrote:
> Make sure properties->optimization "omit frame pointers" is set to "No" for
> your release build, otherwise the compiler will feel free to do what it
> wants with ebp.
>
> My understanding was that if you ever use _alloca() in a function, though,
> the compiler would be forced to use ebp as a frame pointer regardless
> because of the exception handling cleanup issue. This was a strong reason
> not to use _alloca because the "omit frame pointers" optimization can be a
> quite significant performance gain. All this may have changed with 7.1,
> however.
>
> -Kevin Wasserman
>
>
>> Date: Tue, 25 Jul 2006 23:12:40 +0000 (GMT)
>> From: Emmanuel Astier <e_a...@ya...>
>> Subject: [GD-Windows] Re : Strange prolog function issue
>> To: Game Development for MS Windows
>> <gam...@li...>
>> Message-ID: <200...@we...>
>> Content-Type: text/plain; charset=utf-8
>>
>> Hi,
>>
>> It only happens in release build. And as you said, I suspect a compiler
>> bug.
>>
>> Actually, I don't understand when the compiler decide to switch to a
>> different prolog for the function, where ebp doesn't have the same meaning.
>> It is all fine as the function code knows the different ebp meaning, and
>> has no trouble accessing local vars, but the exception handler seems not to
>> be aware of the change in the ebp meaning.
>>
>> Thanks for your help,
>> we send a mail to microsoft, we will wait for their anwser...
>>
>> Emmanuel
>>
>> Ps : Kent, replying to your mails only replies to you, not to the list...
>>
>
>
>
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