[llvm] [MemoryLocation] Model value parameter of memset.pattern intrinsic (PR #138559)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

We should definitely handle this via attributes on the intrinsic instead. I have recently done the groundwork to allow intrinsic attributes to depend on the type, so doing this should be pretty simple now.

I'd expect the lowest complexity ways to achieve this would be to either a) add something like `IntrCustom<ArgIndex<1>, "getMemsetPatternAttrs">` and implement the logic in C++ or b) add a pseudo-property like `IntrReadNoneNoCaptureIfPtr`. (Could probably also use it in some other places like llvm.is.constant.)

https://github.com/llvm/llvm-project/pull/138559