[LLVMdev] RE : RE : Is there any llvm neon intrinsic that maps to vmla.f32 instruction ?

[Sebastien DELDON-GNB]

Hi Lang,

I'm speaking about 64-fp vmla. Find attached to this e-mail, a .ll file that exhibits problem encountered in MILC. 
I've built LLVM (trunk & 3.2) on a x86-64 Ubuntu 10.04 LTS system.
Try 
llc  -march=arm -mcpu=cortex-a9  vmlx_ex.ll -o vmlx_ex.s
and
llc  -march=arm -mcpu=cortex-a9 -mattr=-vmlx-forwarding vmlx_ex.ll -o vmlx_ex.s

You should see difference and trust me it make significant difference in performance - at least on my platform - on MILC and other FP intensive code.

Best Regards
Seb


________________________________________
De : Lang Hames [lhames at gmail.com]
Date d'envoi : mercredi 13 février 2013 08:31
À : Renato Golin
Cc : Sebastien DELDON-GNB; llvmdev at cs.uiuc.edu
Objet : Re: [LLVMdev] RE : Is there any llvm neon intrinsic that maps to vmla.f32 instruction ?

Hi Sebastien,

How many extra vmlas did you see in 433.milc due to disabling -vmlx-forwarding?
As I mentioned earlier, I saw only two additional integer vmlx instructions when I tested.

Could you send me your 433.milc compile setup? (os, flags, compiler version, etc.). I'd like to try to reproduce your results.

Cheers,
Lang.


On Tue, Feb 12, 2013 at 9:05 AM, Renato Golin <renato.golin at linaro.org<mailto:renato.golin at linaro.org>> wrote:
On 12 February 2013 16:56, Sebastien DELDON-GNB <sebastien.deldon at st.com<mailto:sebastien.deldon at st.com>> wrote:
If this helps taking your decision, there are at least two benchmarks for which disabling vmlx-forwarding makes a significant difference.

I think Evan's worry was to base this decision on visible and comprehensible benchmarks, such as the test-suite.


If I get lucky I may be able to run on a panda board by next week and have more info to share

That'd be great, thanks!

--renato

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