llvm dev - May 2017 - LLVM and Xeon Skylake v5

Hi,

I have a JIT compiler using the legacy JIT on LLVM 3.5 that, when run on the
Xeon v5 Skylakes produces "Cannot select: intrinsic
%llvm.x86.sse41.round.sd". Note, this does not occur on i7 Kabylakes. To
get this far I had to disable AVX512 code gen.

Upgrading the system I am looking at from 3.5 to a later version is a big job
that I'd prefer not to have on my critical path.

Does anyone have any tips on where I would look to debug this sort of issue?
I'm new to LLVM.

Thanks

Andy

I can try to help.

Are you passing a CPU string or are you letting it autodetect the CPU using
getHostCPUName? I don't see support detecting skylake or even avx-512
support in the autodetection code that far back. Are you doing the same
thing for the i7 kabylake? How did you disable AVX-512 code gen?

~Craig

On Mon, May 8, 2017 at 9:21 AM, Andy Schneider via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi,
>
> I have a JIT compiler using the legacy JIT on LLVM 3.5 that, when run on
> the Xeon v5 Skylakes produces "Cannot select: intrinsic %
> llvm.x86.sse41.round.sd". Note, this does not occur on i7 Kabylakes.
To
> get this far I had to disable AVX512 code gen.
>
> Upgrading the system I am looking at from 3.5 to a later version is a big
> job that I'd prefer not to have on my critical path.
>
> Does anyone have any tips on where I would look to debug this sort of
> issue? I'm new to LLVM.
>
> Thanks
>
> Andy
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Thank you. I'm letting it auto detect by setting the target using
getProcessTarget. I disabled avx512 support by passing -avx512f (and the other
variants) to setMAttrs on EngineBuilder. I can see refs to avx512 in X86.td.
It's the exact same executable running on Kabylake.

What does the Cannot select: specifically mean? Is there some table that
doesn't have a definition for a key in it that I would need to patch up?

Am I answering your questions?

> On 8 May 2017, at 17:32, Craig Topper <craig.topper at gmail.com>
wrote:
> 
> I can try to help.
> 
> Are you passing a CPU string or are you letting it autodetect the CPU using
getHostCPUName? I don't see support detecting skylake or even avx-512
support in the autodetection code that far back. Are you doing the same thing
for the i7 kabylake? How did you disable AVX-512 code gen?
> 
> ~Craig
> 
>> On Mon, May 8, 2017 at 9:21 AM, Andy Schneider via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>> Hi,
>> 
>> I have a JIT compiler using the legacy JIT on LLVM 3.5 that, when run
on the Xeon v5 Skylakes produces "Cannot select: intrinsic
%llvm.x86.sse41.round.sd". Note, this does not occur on i7 Kabylakes. To
get this far I had to disable AVX512 code gen.
>> 
>> Upgrading the system I am looking at from 3.5 to a later version is a
big job that I'd prefer not to have on my critical path.
>> 
>> Does anyone have any tips on where I would look to debug this sort of
issue? I'm new to LLVM.
>> 
>> Thanks
>> 
>> Andy
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
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