Add libsetjmp.a/so #483
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Add libsetjmp.a/so #483
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Add setjmp/longjump support based on Wasm EH proposal.
It's provided as a separate library (libsetjmp) from libc so that
runtimes w/o EH support can still load libc.so.
To use this setjmp/longjmp implementation, an application should
be compiled with `-mllvm -wasm-enable-sjlj` and linked with `-lsetjmp`.
(You need an LLVM with the change mentioned below.)
Also, you need a runtime with EH support to run such an application.
If you want to use the latest EH instructions, you can use
`binaryen --translate-eh-old-to-new` on your application.
Note: You don't need to translate libsetjmp.a/so to the new EH.
While LLVM currently produces bytecode for an old version of the EH
proposal, luckily for us, the bytecode used in this library (ie. the tag
definition and the "throw" instruction) is compatible with the latest
version of the proposal.
The runtime logic is basically copy-and-paste from:
https://github.com/yamt/garbage/tree/wasm-sjlj-alt2/wasm/longjmp
The corresponding LLVM change:
llvm/llvm-project#84137
(Note: you need this change to build setjmp/longjmp using code.
otoh, you don't need this to build libsetjmp.)
A similar change for emscripten:
emscripten-core/emscripten#21502
An older version of this PR, which doesn't require LLVM changes:
WebAssembly#467
Discussion:
https://docs.google.com/document/d/1ZvTPT36K5jjiedF8MCXbEmYjULJjI723aOAks1IdLLg/edit
An example to use the latest EH instructions:
```
clang -mllvm -wasm-enable-sjlj -o your_app.wasm your_app.c -lsetjmp
wasm-opt --translate-eh-old-to-new -o your_app.wasm your_app.wasm
toywasm --wasi your_app.wasm
```
Note: use toywasm built with `-DTOYWASM_ENABLE_WASM_EXCEPTION_HANDLING=ON`.
An example to use the older EH instructions, which LLVM currently produces:
```
clang -mllvm -wasm-enable-sjlj -o your_app.wasm your_app.c -lsetjmp
iwasm your_app.wasm
```
Note: use wasm-micro-runtime built with `-DWAMR_BUILD_EXCE_HANDLING=1`.
Note: as of writing this, only the classic interpreter supports EH.
|
this looks really cool! i don't know how to propose changes to a PR, so i'll just write a comment.
|
oops. fixed. thank you. |
yamt
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Mar 16, 2024
sunfishcode
approved these changes
Mar 19, 2024
| /* | ||
| * a runtime implementation for | ||
| * https://github.com/llvm/llvm-project/pull/84137 | ||
| * https://docs.google.com/document/d/1ZvTPT36K5jjiedF8MCXbEmYjULJjI723aOAks1IdLLg/edit |
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Ideally we should copy the content of this into the tool-conventions repo. Would you be interested in doing this, or would you mind if I did it?
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i agree we should document in the tool-conventions repo.
i think i can write something next month.
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i wrote something. WebAssembly/tool-conventions#225
aheejin
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to llvm/llvm-project
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Mar 26, 2024
…jlj (#84137) Instead of maintaining per-function-invocation malloc()'ed tables to track which functions each label belongs to, store the equivalent info in jump buffers (jmp_buf) themselves. Also, use a less emscripten-looking ABI symbols: ``` saveSetjmp -> __wasm_setjmp testSetjmp -> __wasm_setjmp_test getTempRet0 -> (removed) __wasm_longjmp -> (no change) ``` While I want to use this for WASI, it should work for emscripten as well. An example runtime and a few tests: https://github.com/yamt/garbage/tree/wasm-sjlj-alt2/wasm/longjmp wasi-libc version of the runtime: WebAssembly/wasi-libc#483 emscripten version of the runtime: emscripten-core/emscripten#21502 Discussion: https://docs.google.com/document/d/1ZvTPT36K5jjiedF8MCXbEmYjULJjI723aOAks1IdLLg/edit
|
Thanks for filing that. This looks good! |
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Add setjmp/longjump support based on Wasm EH proposal.
It's provided as a separate library (libsetjmp) from libc so that runtimes w/o EH support can still load libc.so.
To use this setjmp/longjmp implementation, an application should be compiled with
-mllvm -wasm-enable-sjljand linked with-lsetjmp. (You need an LLVM with the change mentioned below.)Also, you need a runtime with EH support to run such an application.
If you want to use the latest EH instructions, you can use
binaryen --translate-eh-old-to-newon your application.Note: You don't need to translate libsetjmp.a/so to the new EH. While LLVM currently produces bytecode for an old version of the EH proposal, luckily for us, the bytecode used in this library (ie. the tag definition and the "throw" instruction) is compatible with the latest version of the proposal.
The runtime logic is basically copy-and-paste from:
https://github.com/yamt/garbage/tree/wasm-sjlj-alt2/wasm/longjmp
The corresponding LLVM change:
llvm/llvm-project#84137
(Note: you need this change to build setjmp/longjmp using code.
otoh, you don't need this to build libsetjmp.)
A similar change for emscripten:
emscripten-core/emscripten#21502
An older version of this PR, which doesn't require LLVM changes:
#467
Discussion:
https://docs.google.com/document/d/1ZvTPT36K5jjiedF8MCXbEmYjULJjI723aOAks1IdLLg/edit
An example to use the latest EH instructions:
Note: use toywasm built with
-DTOYWASM_ENABLE_WASM_EXCEPTION_HANDLING=ON.An example to use the older EH instructions, which LLVM currently produces:
Note: use wasm-micro-runtime built with
-DWAMR_BUILD_EXCE_HANDLING=1.Note: as of writing this, only the classic interpreter supports EH.