[llvm-dev] generate vectorized code

[Rail Shafigulin via llvm-dev]

On Thu, Mar 17, 2016 at 2:41 PM, Rail Shafigulin <rail at esenciatech.com>
wrote:

> On Thu, Mar 17, 2016 at 10:10 AM, Rail Shafigulin <rail at esenciatech.com>
> wrote:
>
>> On Wed, Mar 16, 2016 at 6:38 PM, Mehdi Amini <mehdi.amini at apple.com>
>> wrote:
>>
>>>
>>> On Mar 16, 2016, at 5:38 PM, Rail Shafigulin <rail at esenciatech.com>
>>> wrote:
>>>
>>> On Wed, Mar 16, 2016 at 11:48 AM, Mehdi Amini <mehdi.amini at apple.com>
>>> wrote:
>>>
>>>> Hi Rail,
>>>>
>>>> Two hints to begin with:
>>>>
>>>> 1) Makes sure you example is vectorized on X86 for example
>>>> 2) Is your target correctly overriding the TTI (declaring the vector
>>>> register size for example) so that the vectorizer can kicks-in (see
>>>> X86TTIImpl::getRegisterBitWidth for instance). Alternatively you can test
>>>> the SLP vectorizer by passing to clang: -mllvm -slp-max-reg-size -mllvm 512
>>>>  (I don't see an equivalent option for the loop vectorizer though).
>>>>
>>>> Well, it sort of worked. I added a getRegisterBitWidth(...) but then I
>>> got this error:
>>>
>>> fatal error: error in backend: Cannot select: 0x5e949a8: v4i32 =
>>> BUILD_VECTOR 0x5e91ae8, 0x5e91ae8, 0x5e91ae8, 0x5e91ae8 [ORD=16] [ID=16]
>>>   0x5e91ae8: i32 = Constant<0> [ID=5]
>>>   0x5e91ae8: i32 = Constant<0> [ID=5]
>>>   0x5e91ae8: i32 = Constant<0> [ID=5]
>>>   0x5e91ae8: i32 = Constant<0> [ID=5]
>>>
>>> What am I missing?
>>>
>>>
>>> I means that you have a vectorized IR that reached your backend, but
>>> your backend is not ready to deal with all the vector constructs in
>>> SelectionDAG.
>>> You need to express how to legalize/select the BUILD_VECTOR in
>>> SelectionDAG to instructions that your target supports. You can look at
>>> what other targets are doing.
>>>
>>> --
>>> Mehdi
>>>
>>>
So I've added setOperationAction(ISD::BUILD_VECTOR,      MVT::v4i32,
Expand); to my code but that generated a following error:

fatal error: error in backend: Cannot select: 0x6a84dc8: i32 =
extract_vector_elt 0x6a85388, 0x6a813b0 [ORD=9] [ID=16]
  0x6a85388: v4i32 = add 0x6a81098, 0x6a81e00 [ORD=8] [ID=15]
    0x6a81098: v4i32 = add 0x6a81bf0, 0x6a84168 [ORD=6] [ID=12]
      0x6a81bf0: v4i32,ch = CopyFromReg 0x6a2b7f0, 0x6a819e0 [ORD=5] [ID=8]
        0x6a819e0: v4i32 = Register %vreg4 [ID=1]
      0x6a84168: v4i32 = vector_shuffle 0x6a81bf0, 0x6a857a8<2,3,u,u>
[ORD=5] [ID=10]
        0x6a81bf0: v4i32,ch = CopyFromReg 0x6a2b7f0, 0x6a819e0 [ORD=5]
[ID=8]
          0x6a819e0: v4i32 = Register %vreg4 [ID=1]
        0x6a857a8: v4i32 = undef [ID=2]
    0x6a81e00: v4i32 = vector_shuffle 0x6a81098, 0x6a857a8<1,u,u,u> [ORD=7]
[ID=14]
      0x6a81098: v4i32 = add 0x6a81bf0, 0x6a84168 [ORD=6] [ID=12]
        0x6a81bf0: v4i32,ch = CopyFromReg 0x6a2b7f0, 0x6a819e0 [ORD=5]
[ID=8]
          0x6a819e0: v4i32 = Register %vreg4 [ID=1]
        0x6a84168: v4i32 = vector_shuffle 0x6a81bf0, 0x6a857a8<2,3,u,u>
[ORD=5] [ID=10]
          0x6a81bf0: v4i32,ch = CopyFromReg 0x6a2b7f0, 0x6a819e0 [ORD=5]
[ID=8]
            0x6a819e0: v4i32 = Register %vreg4 [ID=1]
          0x6a857a8: v4i32 = undef [ID=2]
      0x6a857a8: v4i32 = undef [ID=2]
  0x6a813b0: i32 = Constant<0> [ID=3]
In function: main

Then I've added
setOperationAction(ISD::EXTRACT_VECTOR_ELT,      MVT::i32, Expand);

but I still got the same error. So removed
setOperationAction(ISD::EXTRACT_VECTOR_ELT,      MVT::i32, Expand); and
added

setOperationAction(ISD::EXTRACT_VECTOR_ELT,      MVT::v4i32, Expand);

which produced a following error:

fatal error: error in backend: Cannot select: 0x7389250: v4i32 =
vector_shuffle 0x73884e8, 0x738cbf8<1,u,u,u> [ORD=7] [ID=15]
  0x73884e8: v4i32 = add 0x7389040, 0x738b5b8 [ORD=6] [ID=13]
    0x7389040: v4i32,ch = CopyFromReg 0x73327f0, 0x7388e30 [ORD=5] [ID=9]
      0x7388e30: v4i32 = Register %vreg4 [ID=1]
    0x738b5b8: v4i32 = vector_shuffle 0x7389040, 0x738cbf8<2,3,u,u> [ORD=5]
[ID=11]
      0x7389040: v4i32,ch = CopyFromReg 0x73327f0, 0x7388e30 [ORD=5] [ID=9]
        0x7388e30: v4i32 = Register %vreg4 [ID=1]
      0x738cbf8: v4i32 = undef [ID=2]
  0x738cbf8: v4i32 = undef [ID=2]
In function: main

Then I'v added setOperationAction(ISD::VECTOR_SHUFFLE,      MVT::v4i32,
Expand);

and then my clang just hang. There is no error, no warning clang just sits
there and nothing happens.

I'm doing a lot of guess work in trying to understand what is going on. I
would really appreciate any help on this.


-- 
Rail Shafigulin
Software Engineer
Esencia Technologies
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