[llvm-dev] Instruction selection pattern for intrinsic returning llvm_any_ty

[Mikael Holmén via llvm-dev]

Hi,

On 03/30/2016 11:15 AM, Matt Arsenault wrote:
>
>> On Mar 30, 2016, at 09:33, Mikael Holmén via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>
>> Hi,
>>
>> On my out-of-tree target I have an intrinsic
>>
>> def int_phx_divm_u16 : Intrinsic<[llvm_any_ty],
>>                                  [llvm_i16_ty, llvm_i16_ty],
>>                                  [IntrNoMem]>;
>>
>> that I want to translate to the following instruction during instruction selection:
>>
>> def divm16_pseudo : MyPseudoInst<
>>     (outs aNh_0_7:$dst, aNh_0_7:$dst2),
>>     (ins aNh_0_7:$src1, aNh_0_7:$src2)>;
>>
>> So I've done a pattern the same way I've done for numerous other intrinsics (that returns simple types like i16/i32 etc):
>>
>> def : Pat<(int_phx_divm_u16 i16:$src1, i16:$src2),
>>           (divm16_pseudo $src1, $src2)>;
>
> It isn’t able to infer the type of the divm16_pseudo instruction, which would be necessary depending on whether the result’s register class for divm16_pseudo includes other types. I would expect you would need to add an explicit i16 around the instruction (e.g. (i16 (divm16_pseudo …)), tlahough the error message does look like it’s having trouble with the operands. You can try inserting the explicit i16:$src1 there if that still doesn’t work

Thanks!

Adding i16 on the arguments to my instruction

def : Pat<(int_phx_divm_u16 i16:$src1, i16:$src2),
           (divm16_pseudo i16:$src1, i16:$src2)>;

now gives me

anonymous_1654:         (divm16_pseudo:i16:i16:i16 i16:i16:$src1, 
i16:i16:$src2)

error: In anonymous_1654: Type inference contradiction found, merging 
'i16' into 'Any'
def : Pat<(int_phx_divm_u16 i16:$src1, i16:$src2),
^

So at least it doesn't say "?" on the arguments anymore, but then I 
still get the same error about merging i16 and Any.

Since the divm16_pseudo instruction (and the lowered call to the 
intrinsic) defines two i16 values, what would be the syntax for the

(i16 (divm16_pseudo …)

stuff?

I've tried
(i16, i16 (divm16_pseudo i16:$src1, i16:$src2)
and
((i16, i16) (divm16_pseudo i16:$src1, i16:$src2)
and a few other variants without managing to get it through.

Thanks again,
Mikael


>
>
>>
>> But this doesn't work for me:
>>
>> anonymous_1373(src1, src2):     (divm16_pseudo:i16:i16:i16 ?:i16:$src1, ?:i16:$src2)
>>
>> error: In anonymous_1373: Type inference contradiction found, merging 'i16' into 'Any'
>> def : Pat<(int_phx_divm_u16 i16:$src1, i16:$src2),
>> ^
>>
>> So is there a way I can get around this?
>>
>>
>> Before ISel the call to my intrisic looks like
>>
>>   %_tmp3 = call %rec6 @llvm.phx.divm.u16.rec6(i16 %_tmp1, i16 %_tmp2)
>>
>> and %rec6 is
>>
>>   %rec6 = type { i16, i16 }
>>
>> Then at ISel, before selection the call is lowered to
>>
>>   t6: i16,i16 = llvm.phx.divm.u16 TargetConstant:i16<3778>, t2, t4
>>
>> which fits nicely to my divm16_pseudo that I want to select.
>>
>> Is there any way I can select this with a tablegen pattern, and not having to do selection "manually" in my target's MytargetDAGToDAGISel::Select function?
>>
>> I'm having a bunch of intrisics looking like this and I'd prefer selecting them with patterns rather than doing much more verbose stuff in C++.
>>
>> I've tried to look in in-tree targets for something similar but I've failed to find anything.
>>
>> Thanks,
>> Mikael
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>
>