Convert Imports to Indirect Calls for Dynamic Linking #10003
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@sbc100 , this is my initial attempt to replace imports with indirect calls. Can you take a look and give me your comments? Thanks. |
emscripten.py
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| originalAccessor = '' | ||
| if shared.Settings.LEGALIZE_JS_FFI and not shared.JS.is_legal_sig(sig): | ||
| name = 'orig$' + name | ||
| originalAccessor = ('if (!func) func = Module["_%s"];' % (name)) |
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Remove the extra pair of ( ) around this statement.
emscripten.py
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| var func = Module['asm']['%(original)s']; | ||
| // If there is no wasm function, this may be a JS library function or | ||
| // something from another module. | ||
| %(originalAccessor)s |
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I think this part is already handles above now isn't it?
I think that was what alon fixed in #9810? Maybe this part of this change can be reverted now?
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I believe the side exports are added to the Module object and not Module['asm'] thus the line var func = Module['asm']['%(original)s']; can only retrieve the original exports from the Main module and not the side. For this PR, we actually need the original exports from the side module, thus the need to retrieve the original side functions from the Module object instead e.g. originalAccessor = ('if (!func) func = Module["_%s"];' % (name))
emscripten.py
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| libraryfile = infile + '.libfile' | ||
| with open(libraryfile, 'w') as f: | ||
| f.write(str(library_fns_list)) |
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I better format would probably just one line per symbols:
for sym in library_fns_list:
f.write(sym + '\n')
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Can we call the file, and this variable somehow more meaningful too? Perhaps "js_imports"? Or "js_symbols"?
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Thanks for the suggestion, will update the format :)
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I am uncomfortable with getting the list of JS library functions in this way. It means that there are two kinds of imports, one that is provided by wasm and one by JS, and the module being compiled needs to know which is which at compile time. This feels a little risky. IIUC this PR makes imported wasm functions be called indirectly. If that is fast enough, then making the JS functions be indirect calls as well may be fast enough too. That is, JS library functions would be added to the table, then treated just like any other import. That layer could also add legalization for JS as needed, which would simplify our legalization story. (However, that assumes these indirect calls are fast enough, and we may want to keep one direction's calls as direct, for speed? That would make this more complicated.) |
…zation when making indirect inter-module calls.
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| for sym in library_fns_list: | ||
| js_symbols_file.write(sym + '\n') | ||
| else: | ||
| js_symbols = [] |
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I stole this idea/code and made it part of #10350 in a function called get_all_js_library_funcs hopefully that is about to land and we can use that shared function here.
| printf("sidey2 says %d", 18); | ||
| return 18; | ||
| } | ||
| ''', expected='sidey says 17 sidey2 says 18', need_reverse=False) |
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Can we somehow verify that this worked by looking at import/exports of the resulting wasm file?
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This issue has been automatically marked as stale because there has been no activity in the past year. It will be closed automatically if no further activity occurs in the next 30 days. Feel free to re-open at any time if this issue is still relevant. |
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This issue has been automatically marked as stale because there has been no activity in the past year. It will be closed automatically if no further activity occurs in the next 30 days. Feel free to re-open at any time if this issue is still relevant. |
4 participants
This complements the work done in WebAssembly/binaryen#2523 to convert Imports in Dynamic Linking into Indirect Calls. The benefits of doing this are:
A sample benchmark has been uploaded here: https://github.com/awtcode/dylink_benchmark
These are the results of the benchmark:
This PR gives a 13x improvement in Chrome and a 7x improvement in FF.