[PATCH] D125764: Assert on polymorphic pointer intrinsic param

[Thomas Preud'homme via Phabricator via llvm-commits]

thopre added a comment.

In D125764#3521604 <https://reviews.llvm.org/D125764#3521604>, @nikic wrote:

> In D125764#3519427 <https://reviews.llvm.org/D125764#3519427>, @thopre wrote:
>
>> In D125764#3519318 <https://reviews.llvm.org/D125764#3519318>, @nikic wrote:
>>
>>> Could you please share an example of a problematic intrinsic signature?
>>
>>
>>
>>   def int_colossus_ststep :
>>     Intrinsic<
>>       [LLVMPointerType<llvm_any_ty>],
>>       [llvm_any_ty,
>>        LLVMPointerType<LLVMMatchType<0>>,
>>        llvm_i32_ty],
>>       [IntrWriteMem, IntrArgMemOnly]>;
>
> Okay, I don't think I really understand the issue you're fixing then. This kind of intrinsic declaration //should// work with opaque pointers. The `LLVMMatchType<0>` predicate inside `LLVMPointerType<>` should just be ignored, which is what the current code is doing (right?)
>
> It looks like we also have some in-tree intrinsics that are using this pattern, such as int_riscv_vlm.

int_riscv_vlm is different because it matches a non-pointer polymorphic type. (the return value). In our case, the polymorphic type is on the pointed type. When that happens, matchIntrinsicType will *not* recurse for the pointed type since there is no pointed type for opaque pointers and thus will *not* push the pointed type into ArgTys. When processing the first parameter (the llvm_any_ty), the function exits with a match failure during deferred checks because of:

        if (D.getArgumentNumber() > ArgTys.size() ||
            D.getArgumentKind() == IITDescriptor::AK_MatchType)
          return IsDeferredCheck || DeferCheck(Ty);
  
  This is because the argument number is 1 but argTys.size() is 0 since the pointed to type was not pushed. Any polymorphic type after a polymorphic pointer type will fail because of that problem.


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