How to implement relocation of return values

[Tt421]

In the llvm-project of emscripten. It use TypeIndex in the file /llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyInstrCall.td implement the parameter of CALL_INDIRECT instruction. I looked at the code briefly and found that it is indeed handling TypeIndex in Relocation.

If I need to implement an instruction, the return value of this instruction is related to the processing type of TypeIndex.
This instruction looks like ref.null ht, which ht is 𝑥:s33, the return value of this instruction can be ref x (𝑥 ≥ 0).

How can I modify the code of the llvm-project to achieve the above effect? Can you give me some implementation suggestions?

[llvmbot]

@llvm/issue-subscribers-backend-webassembly

Author: None (Tt421)

In the llvm-project of emscripten. It use `TypeIndex` in the file `/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyInstrCall.td` implement the parameter of `CALL_INDIRECT` instruction. I looked at the code briefly and found that it is indeed handling `TypeIndex` in Relocation.

If I need to implement an instruction, the return value of this instruction is related to the processing type of TypeIndex.
This instruction looks like ref.null ht, which ht is 𝑥:s33, the return value of this instruction can be ref x (𝑥 ≥ 0).

How can I modify the code of the llvm-project to achieve the above effect? Can you give me some implementation suggestions?

[dschuff]

Unfortunately LLVM does not currently model WasmGC types at all. Its idea of wasm types are basically just function signatures (see e.g. WasmSignature). Furthermore there are a lot of assumptions baked into LLVM about memory that are mapped directly onto wasm linear memory, so there's currently not a clear idea of how one would use LLVM to compile to WasmGC. Which isn't to say it's impossible, but it would probably require quite a bit of design work and thinking through issues.