[llvm-dev] KNL Vectorization with larger vector width

[hameeza ahmed via llvm-dev]

Thank You.

I am currently seeing how LLVM treats remainder loops. For eg with 63 loop
iterations i get 3 v16i32 and 15 scalars. I want to use v8 and v4 for 15
remainder instructions. How to do this?

I am seeing LoopVectorize.cpp but unable to find the code lines that deal
with remainder scalar loop iterations.

Please help..



On Tue, Jul 24, 2018 at 10:54 PM, Friedman, Eli <efriedma at codeaurora.org>
wrote:

> There currently isn't any implementation of epilog loop vectorization (see
> https://reviews.llvm.org/D30247, but it never got merged).
>
> In some cases you might get lucky with loop unrolling plus SLP
> vectorization.
>
> -Eli
>
>
> On 7/24/2018 10:34 AM, hameeza ahmed wrote:
>
> Hello,
> I need help here. I am able to adjust the vector width through
> WidestRegister value. When number of iterations=31 and  I set vector
> width=32 it gives <16xi32> and <8xi32> instructions.
>
> However if i replicate same behavior with number of iterations=63 and  I
> set vector width=64, no vector instructions are emitted. it should do as
> previous and gives <32xi32> and <16xi32> vector instructions.
>
> How to do this?
> What adjustments are needed?
>
> Please help
>
> I m trying this but unable to solve.
>
> Thank You
>
> On Tue, Jul 24, 2018 at 4:44 PM, hameeza ahmed <hahmed2305 at gmail.com>
> wrote:
>
>> Hello,
>> Do i need to change following function;
>>
>> unsigned X86TTIImpl::getNumberOfRegisters(bool Vector) {
>>   if (Vector && !ST->hasSSE1())
>>     return 0;
>>
>>   if (ST->is64Bit()) {
>>     if (Vector && ST->hasAVX512())
>>       return 32;
>>     return 16;
>>   }
>>   return 8;
>> }
>>
>> to
>>
>> if (ST->is2048Bit()) {
>>     if (Vector && ST->hasAVX512())
>>       return 1024;
>>     return 512;
>>   }
>>   return 256;
>>
>>
>> please help...
>>
>> On Tue, Jul 24, 2018 at 5:05 AM, hameeza ahmed <hahmed2305 at gmail.com>
>> wrote:
>>
>>> Thank You.
>>> Right now to see the effect i did following changes;
>>>
>>> unsigned X86TTIImpl::getRegisterBitWidth(bool Vector) {
>>>   if (Vector) {
>>>     if (ST->hasAVX512())
>>>       return 65536;
>>>
>>> here i changed 512 to 65536. Then in loopvectorize.cpp i did following;
>>>
>>>  assert(MaxVectorSize <= 2048 && "Did not expect to pack so many
>>> elements"
>>>                                 " into one vector!");
>>>
>>> changed 64 to 2048.
>>>
>>> It runs fine. I can see in IR <2048xi32> or <1024xi64> emission.
>>>
>>> But I cannot see the vector mix like in default knl if iterations=15 we
>>> see 1<8xi32> and rest scalar. so here when i keep iteration=2047 i get all
>>> scalar why is that so? similarly in polly as well i cant see vector mixes
>>> like its happening for KNL it emits <v16i32>, <v8i32>,<v4i32>...so here it
>>> should emit recursively like <v2048i32> <v1024i32> <v512i32>.....<v32i32>
>>>
>>> how to do this?
>>>
>>> What am i missing here?
>>> what further changes do i need to make?
>>>
>>> Please help...
>>>
>>>
>>>
>>>
>>>
>>>
>>> On Tue, Jul 24, 2018 at 1:52 AM, Friedman, Eli <efriedma at codeaurora.org>
>>> wrote:
>>>
>>>> On 7/23/2018 12:40 PM, hameeza ahmed wrote:
>>>>
>>>>> Thank You. I got it. Version issue.
>>>>>
>>>>> TTI.getRegisterBitWidth(true)
>>>>>
>>>>> How to put my target machine info in TTI?
>>>>>
>>>>
>>>> Each target has an implementation, e.g. X86TTIImpl::getRegisterBitWidth.
>>>>
>>>>
>>>>
>>>> -Eli
>>>>
>>>> --
>>>> Employee of Qualcomm Innovation Center, Inc.
>>>> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
>>>> Linux Foundation Collaborative Project
>>>>
>>>>
>>>
>>
> --
> You received this message because you are subscribed to the Google Groups
> "Polly Development" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to polly-dev+unsubscribe at googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
>
>
> --
> Employee of Qualcomm Innovation Center, Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20180728/c38cee5d/attachment.html>