[LLVMdev] Performance regression on ARM

C Bergström cbergstrom at pathscale.com
Sat Oct 18 16:31:24 PDT 2014

On Sun, Oct 19, 2014 at 6:11 AM, Joerg Sonnenberger <joerg at britannica.bec.de
> wrote:

> On Fri, Oct 17, 2014 at 06:51:38PM +0400, Anton Korobeynikov 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.
> One possible approach is the attached patch. It is not completely
> correct as it doesn't handle the possible exceptions for WoA and iOS,
> but it might be a starting point. The real question for me is whether
> this logic belongs into clang at all. Who can speak up for the Fortran
> related behavior of complex arithmetic? If it matters the desired C
> rules, especially with regard to real and imaginary numbers, it would
> strongly support putting it into IR properly.

I apologize that I haven't been able to follow this thread entirely, but if
someone gives me a Fortran testcase I can check what Fortran+llvm would do
currently and maybe give more feedback.
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