Re: [2.6 patch] add a config option for -Os compilation

[Martin J. Bligh]

--Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote (on Sunday, September 14, 2003 15:57:49 +0100):

> On Sul, 2003-09-14 at 14:53, Wade wrote:
>> Adrian Bunk wrote:
>> > The patch below adds a config option OPTIMIZE_FOR_SIZE for telling gcc 
>> > to use -Os instead of -O2. Besides this, it removes constructs on 
>> > architectures that had a -Os hardcoded in their Makefiles.
>> 
>> Someone told me that -Os is actually faster than -O2 for Athlons, is 
>> that true?
> 
> On gcc 2.95 -Os was faster for most stuff. I would intuitively expect
> the best result to be a mix varied by function but I don't think gcc has
> the support to do that.
> 
> I've also not benched gcc 3.2 -Os v -O2 at real workloads - thats a 
> nice little project for someone.

I think it depends heavily on the chip - I tried 2.95 and 3.3. For me,
-Os was slower for both, but I have a 2MB L2 cache. If you have a 128K
celeron or something, I'm sure it'd be faster.

M.

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