[LLVMdev] arm compiler benchmarks

[Renato Golin]

I haven't tried using -Os/z on any ARM device for the last 3 years, and
back then, -Os would break many things.

People normally care about code size on Cortex-R/M and ARM9 or older, and
in there, not many LLVM users.

--renato


On 27 February 2013 00:38, Jim Grosbach <grosbach at apple.com> wrote:

> I've not run any on non-iOS devices, and haven't looked at GCC since
> v4.2.1 due to licensing issues, so I don't have a good feel for comparative
> benchmarking.
>
> -Jim
>
>
> On Feb 26, 2013, at 4:20 PM, Reed Kotler <rkotler at mips.com> wrote:
>
> What about benchmarks on other Arm devices?
>
> On 02/26/2013 02:52 PM, Jim Grosbach wrote:
>
> Cortex-M0 is a Thumb1 only device. There hasn't been any concerted
> effort to tune LLVM's Thumb1 output in quite a long time. Even back then
> (2008 or so), the effort was mainly to get it to work acceptably, with
> the real performance tuning work being done for Thumb2. I'm not
> surprised that an embedded market focussed compiler like IAR is better
> tuned for a chip like that.
>
> -Jim
>
> On Feb 26, 2013, at 2:11 PM, matic at nimp.co.uk <mailto:matic at nimp.co.uk<matic at nimp.co.uk>
> >
> wrote:
>
> Hi,
>
>
> I didn't do any serious benchmarking but so far I never found a case
> where LLVM does better than IAR on CortexM0, but I saw a lot of cases
> where IAR output is better than LLVM...
>
> That said I did not use -Os or -Oz, I just used -O3.
>
> A recurrent situation is that LLVM push/pop one or two extra registers
> compared to IAR, I guess it does so in order to comply with a standard
> ABI or something but in the world of deeply embedded system, we don't
> care of such things 99.99% of the time...
>
> If you want to see some good code output, take a look at IAR, there is
> a free version limited in code size online.
>
> Cheers,
>
> Sebastien
>
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