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

[Matt Arsenault via llvm-dev]

> 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


> 
> 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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