<div dir="ltr">I haven't tried using -Os/z on any ARM device for the last 3 years, and back then, -Os would break many things.<div><br></div><div style>People normally care about code size on Cortex-R/M and ARM9 or older, and in there, not many LLVM users.</div>
<div style><br></div><div style>--renato</div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On 27 February 2013 00:38, Jim Grosbach <span dir="ltr"><<a href="mailto:grosbach@apple.com" target="_blank">grosbach@apple.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word">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.<span class="HOEnZb"><font color="#888888"><div>
<br></div></font></span><div><span class="HOEnZb"><font color="#888888">-Jim</font></span><div><div class="h5"><br><div><br><div><div>On Feb 26, 2013, at 4:20 PM, Reed Kotler <<a href="mailto:rkotler@mips.com" target="_blank">rkotler@mips.com</a>> wrote:</div>
<br><blockquote type="cite"><div style="letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">What about benchmarks on other Arm devices?<br><br>On 02/26/2013 02:52 PM, Jim Grosbach wrote:<br>
<blockquote type="cite">Cortex-M0 is a Thumb1 only device. There hasn't been any concerted<br>effort to tune LLVM's Thumb1 output in quite a long time. Even back then<br>(2008 or so), the effort was mainly to get it to work acceptably, with<br>
the real performance tuning work being done for Thumb2. I'm not<br>surprised that an embedded market focussed compiler like IAR is better<br>tuned for a chip like that.<br><br>-Jim<br><br>On Feb 26, 2013, at 2:11 PM,<span> </span><a href="mailto:matic@nimp.co.uk" target="_blank">matic@nimp.co.uk</a><span> </span><<a href="mailto:matic@nimp.co.uk" target="_blank">mailto:matic@nimp.co.uk</a>><br>
wrote:<br><br><blockquote type="cite">Hi,<br><br><br>I didn't do any serious benchmarking but so far I never found a case<br>where LLVM does better than IAR on CortexM0, but I saw a lot of cases<br>where IAR output is better than LLVM...<br>
<br>That said I did not use -Os or -Oz, I just used -O3.<br><br>A recurrent situation is that LLVM push/pop one or two extra registers<br>compared to IAR, I guess it does so in order to comply with a standard<br>ABI or something but in the world of deeply embedded system, we don't<br>
care of such things 99.99% of the time...<br><br>If you want to see some good code output, take a look at IAR, there is<br>a free version limited in code size online.<br><br>Cheers,<br><br>Sebastien<br><br>_______________________________________________<br>
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