llvm dev - Oct 2014 - [LLVMdev] Performance regression on ARM

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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On Sun, Oct 19, 2014 at 06:31:24AM +0700, C Bergström
wrote:
> 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.
Short version: if you multiple or divide a complex number by a real
number, is it valid to just do the trivial component wise computation?
What about multiplying with / dividing by a pure imaginary number?

Joerg

On Sun, Oct 19, 2014 at 6:45 AM, Joerg Sonnenberger <joerg at
britannica.bec.de
> wrote:
> On Sun, Oct 19, 2014 at 06:31:24AM +0700, C Bergström wrote:
> > 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.
>
> Short version: if you multiple or divide a complex number by a real
> number, is it valid to just do the trivial component wise computation?
> What about multiplying with / dividing by a pure imaginary number?
>
I'll try to get a solid answer, but for clarity.. Fortran has types REAL
and CMPLX. I'm not sure if you mean INT or REAL when you say
"real" number..
https://gcc.gnu.org/onlinedocs/gfortran/CMPLX.html
https://gcc.gnu.org/onlinedocs/gfortran/REAL.html
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