[Bug target/79581] VFP4 slower than VFP3 in C-ray on Cortex A5

[tulipawn at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79581

--- Comment #8 from PeteVine  ---
I've just confirmed the result on a newer Linux distribution (Ubuntu 16.04) and
the difference between VFPv3 and v4 is clearly there (2330 vs 2560) using gcc
5.4. 

Unless the CPU itself requires an erratum, that probably leaves suboptimal
codegen as the main suspect.

[Bug target/79581] VFP4 slower than VFP3 in C-ray on Cortex A5

[tulipawn at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79581

--- Comment #7 from PeteVine  ---
Thanks, I promise to test any patches without delay :)

[Bug target/79581] VFP4 slower than VFP3 in C-ray on Cortex A5

[ramana at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79581

Ramana Radhakrishnan  changed:

   What|Removed |Added

 Status|UNCONFIRMED |NEW
   Last reconfirmed||2017-06-15
 CC||ramana at gcc dot gnu.org
 Ever confirmed|0   |1

--- Comment #6 from Ramana Radhakrishnan  ---
(In reply to PeteVine from comment #4)
> > Judging by your -mcpu option is this on a Cortex-A5?
> 
> Yes, if you look at the results on a Cortex A53 running armv7 code, it
> doesn't reproduce either, and A5-codegen is king :) (hopefully due to
> in-order design or sth)
> 
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53659#c12
> 
> A quick question regarding -mcpu=cortex-a5 codegen; is there a similar
> switch to llvm's `-slowfpvmlx` feature? (disable slow vmla/vmls), which the
> nice ARM guy divulged here:
> 
> https://bugs.llvm.org//show_bug.cgi?id=26135#c9  
> 
> or is it a non-issue in gcc?

No, there isn't a similar switch to that in GCC that I'm aware of.

It's also not yet clear why the change is - the only difference is as per
kyrill's analysis in c#3

I'm going to confirm this but I don't have Cortex-A5 hardware to investigate /
play with this any further.

[Bug target/79581] VFP4 slower than VFP3 in C-ray on Cortex A5

[tulipawn at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79581

--- Comment #5 from PeteVine  ---
Unchanged in gcc version 8.0.0 20170501.