[LLVMdev] Performance regression on ARM (original) (raw)

Anton Korobeynikov anton at korobeynikov.info
Sat Oct 18 04:27:37 PDT 2014

Hi Chandler,

That's embarrassing how weird this part of clang is. I have a provisional patch which fixes the problem but underlines clang's problems. I will submit it tonight for comments.

суббота, 18 октября 2014 г. пользователь Chandler Carruth написал:

On Fri, Oct 17, 2014 at 7:51 AM, Anton Korobeynikov <_ _anton at korobeynikov.info_ _<javascript:e(%7B%7D,'cvml','anton at korobeynikov.info');>> wrote:

> Chandler’s complex arithmetic changes are also in the range: r219557 in clang. We saw it change the code in mandel-2 significantly. mandel-2 is broken on hard FP ABI systems, btw. The reason is simply: _we're emitting a call to muldc3 with AAPCS VFP calling convention, however, the function expects softfp (AAPCS) calling conv and reads garbage from GP registers.

I'm working on fix. Thanks for looking at this Anton. I don't really know what signal should be used here. Several initial attempts at this didn't work because of ABI and calling convention issues and I thought I had figured out a sound solution by directly forming and calling the library routines using Clang's code generation to handle all of the ABI issues.... but apparently not. If you need to back out the patch temporarily or take any other steps to mitigate, by all means. =/ Sorry for the fallout.

-- With best regards, Anton Korobeynikov Faculty of Mathematics and Mechanics, Saint Petersburg State University -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20141018/958de1a8/attachment.html>

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