✔ riscv64 fiber port. · general

Stream: general

Topic: ✔ riscv64 fiber port.

yang yu (Jul 25 2022 at 05:36):

Can someone help me port fiber lib to riscv64.
I am not very understand the concept of the lib.
https://github.com/bytecodealliance/wasmtime/pull/4271#issuecomment-1186734601
thanks.

add riscv64 backend for cranelift. by yuyang-ok · Pull Request #4271 · bytecodealliance/wasmtime

I am been trying to add riscv64 backend for cranelift these days. right now I have pass all run test in filetests. some features not implemented right now. i128 mul div rem, all simd type and com...

Anton Kirilov (Jul 25 2022 at 13:47):

I might be able to answer general questions, but nothing RISC-V-specific. Since you say that you don't understand the concept of the crate, are you aware of the general concept of a fiber?
The wasmtime_fiber_switch() function is executed after one fiber yields, and there is another runnable fiber. wasmtime_fiber_init() is a fiber creation routine, or at least contains the bits that must be implemented in assembly.

yang yu (Aug 04 2022 at 02:51):

right now . only unwinding stack not working.

image.png
https://github.com/yuyang-ok/wasmtime/blob/risc-v/crates/fiber/src/unix/riscv64.rs

I am wondering if something wrong with sp pointer, since sp is callee-save register.
But looks didnot restore.

wasmtime/riscv64.rs at risc-v · yuyang-ok/wasmtime

Standalone JIT-style runtime for WebAssembly, using Cranelift - wasmtime/riscv64.rs at risc-v · yuyang-ok/wasmtime

Chris Fallin (Aug 04 2022 at 15:05):

I am wondering if something wrong with sp pointer, since sp is callee-save register.
But looks didnot restore.

@yang yu a stack-swapping context switch (what the fiber switch routine is doing) saves/restores SP right in the middle, as it switches to the new one; or do I misunderstand the issue? In any case, great that fibers are working now!

nagisa (Aug 04 2022 at 18:45):

unwinds not working usually are going to be caused by incorrect cfi somewhere.

yang yu (Aug 05 2022 at 00:59):

@Chris Fallin I have switch sp in assembly code. sp didnot restore I means sp didnot restore when unwinding the stack.
I have another question at.

https://stackoverflow.com/questions/73232295/how-dwarf-format-caculate-provious-sp-pointer

how dwarf format caculate provious sp pointer

this is example is from dwarf document. How Can I caculate provious sp(r7) pointer,I mean It didnot save sp somewhere since sp is a callee-save register. The architectural ABI committee specifies t...

Chris Fallin (Aug 05 2022 at 01:12):

@yang yu it's probably best to ask @Alex Crichton , he set up the CFI directives in wasmtime-fiber I think

yang yu (Aug 05 2022 at 01:13):

yes , but He still have no time.

Notification Bot (Aug 10 2022 at 00:44):

yang yu has marked this topic as resolved.

Last updated: Oct 23 2024 at 20:03 UTC