Micro-optimize performance and code size generated for longjmp #15792
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juj
commented
Dec 15, 2021
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| _emscripten_throw_longjmp__sig: 'v', | ||
| _emscripten_throw_longjmp: function() { throw 'longjmp'; }, | ||
| _emscripten_throw_longjmp: function() { throw Infinity; }, |
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I wonder if the existence of this whole function should be gated behind
#if SUPPORT_LONGJMP == 'emscripten'
?
Though the function
void emscripten_longjmp(uintptr_t env, int val) {
setThrew(env, val);
_emscripten_throw_longjmp();
}in emscripten_setjmp.c is not gated behind a #ifndef __USING_WASM_SJLJ__, which seems to be at odds against the choice with line 709 in preamble.js (#if SUPPORT_LONGJMP == 'emscripten')?
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Those both seem like reasonable suggestions. Neither should save any code size benefit I guess because neither should ever be referenced in that case.. but its still good for correctness to prevent accidental references.
sbc100
reviewed
Dec 16, 2021
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Great!
I hadn't realized what (e != e+0) was doing exactly until read your comments here..
sbc100
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Dec 16, 2021
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…cripten invokes to avoid string comparisons Gate code that is only used for Emscripten EH and not Wasm EH behind `#if SUPPORT_LONGJMP == 'emscripten'` / `#ifndef __USING_WASM_SJLJ__`
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Micro-optimize performance and code size generated for longjmp in Emscripten invokes to avoid string comparisons.
Something that came to mind while reviewing #15788.