[clang] [WebAssembly,clang] Add __builtin_wasm_test_function_pointer_signature (PR #150201)

[Sam Clegg via cfe-commits]

sbc100 wrote:

> I'd also like to add `__builtin_wasm_nontrapping_call(&success, func, a, b, c)` which tries to call func with 3, 2, 1, and 0 arguments.

Where would the return value go here?  Would end up in &success?  What happens if none of the signatures match?

Could you write this in terms of `__builtin_wasm_test_function_pointer_signature` using C++ templates?

https://github.com/llvm/llvm-project/pull/150201