playX (Jun 09 2020 at 13:33): playX (Jun 09 2020 at 13:33):I would like to use Cranelift as baseline JIT and instead of placing VM registers on heap allocated stack I would like to use real registers and machine stack, but I can't find any information/tutorial/documentation on how to use stackmaps in cranelift, is there any information?
playX (Jun 09 2020 at 13:35):P.S My languge is dynamically typed and uses nan-boxing so I need to place all values to stackmap and VM Value can be stored in just I64 on both 32 bit and 64 bit machines
Notification Bot (Jun 09 2020 at 13:40):This topic was moved here from #general > Stackmap and GC roots by Till Schneidereit
Till Schneidereit (Jun 09 2020 at 13:41):(I moved this for more visibility to Cranelift folks)
Till Schneidereit (Jun 09 2020 at 13:41):@playX does https://github.com/bytecodealliance/wasmtime/pull/1832 help, by any chance?
playX (Jun 09 2020 at 13:48):@Till Schneidereit helps a litte, but there is no good explanation on how to use these stackmaps, how to get them e.g with SimpleJITBackend and Idk where and when I should use reference type vs just i32/i64
Till Schneidereit (Jun 09 2020 at 14:12):@fitzgen (he/him) might be able to answer some of this, but it seems plausible that for now using this does require digging into the code quite a bit
fitzgen (he/him) (Jun 09 2020 at 16:40):@playX, I recently landed a PR that improved the docs for Stackmap a bit and cleared up questions that I had when implementing their integration into Wasmtime: https://github.com/bytecodealliance/wasmtime/pull/1824/files#diff-97dbc08ed429dd9faefe70055a6c2009
Note that Cranelift's stack map support assumes that references are pointer-sized, so using r64 on 32-bit architectures won't work right now.
fitzgen (he/him) (Jun 09 2020 at 16:40):@playX ^
playX (Jun 09 2020 at 16:55):This documentation is cool but still does not show any example code, maybe it's worth adding some examples on how to use it and how to get frame pointers etc.
fitzgen (he/him) (Jun 09 2020 at 20:34):to get the stack pointers, you need to use something like libunwind to walk the stack, or your own stack walker
there is a WIP pr to add SP support to the backtrace crate here: https://github.com/rust-lang/backtrace-rs/pull/341
playX (Jun 15 2020 at 01:37):@fitzgen (he/him) I'll probably go with conservative on stack GC right now because in my project roots might be located anywhere, but for JITed functions when I'll learn more about stackmaps I'll use them :)
Last updated: Dec 23 2024 at 12:05 UTC