[Wasm RyuJIT] Stack Tracing #121830
Description
To be able to walk the stack in the Wasm environment we need to manually maintain a stack of the managed code that is executing as we recurse (via function calls) and return. You can see one approach to this described in NAOT-LLVM's documentation, here: https://github.com/dotnet/runtimelab/blob/feature/NativeAOT-LLVM/docs/design/coreclr/botr/nativeaot-wasm-exception-handling.md#:~:text=With%20that%20said%2C%20here%20is%20one%20way%20codegen%20could%20maintain%20the%20unwind%20index
Implementing this will require the JIT to generate a prologue at the head of every managed method to create a virtual stack frame and push it onto the stack, along with an epilogue to pop it when returning. Exception unwinding will also need to properly manipulate this stack during abnormal exits of methods to ensure they don't remain on the stack.
The current stack pointer likely needs to be passed to all managed methods as an argument because the code size penalty from using a global is severe due to the limitations of Wasm linkers (the global index would have to be 5 bytes long, raising the size of a stack access from 2 bytes to 6.)
(incomplete - work in progress)