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Use WebAssembly.compileStreaming API if available #5606

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Merged
merged 5 commits into from
Sep 28, 2017
Merged

Use WebAssembly.compileStreaming API if available #5606

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ccdf34c
Use WebAssembly.compileStreaming API if available
dschuff Sep 27, 2017
23a2364
remove spurious change and debug print
dschuff Sep 27, 2017
bc1fc50
review comments
dschuff Sep 27, 2017
c2cb807
update server
dschuff Sep 28, 2017
626f349
remove extra print
dschuff Sep 28, 2017
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32 changes: 25 additions & 7 deletions src/preamble.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2318,19 +2318,37 @@ function integrateWasmJS() {
// later), so we save Module and check it later.
var trueModule = Module;
#endif
getBinaryPromise().then(function(binary) {
return WebAssembly.instantiate(binary, info)
}).then(function(output) {
function receiveInstantiatedSource(output) {
// 'output' is a WebAssemblyInstantiatedSource object which has both the module and instance.
// receiveInstance() will swap in the exports (to Module.asm) so they can be called
#if ASSERTIONS
assert(Module === trueModule, 'the Module object should not be replaced during async compilation - perhaps the order of HTML elements is wrong?');
trueModule = null;
#endif
receiveInstance(output['instance']);
}).catch(function(reason) {
Module['printErr']('failed to asynchronously prepare wasm: ' + reason);
abort(reason);
});
}
function instantiateArrayBuffer(receiver) {
getBinaryPromise().then(function(binary) {
return WebAssembly.instantiate(binary, info);
}).then(receiver).catch(function(reason) {
Module['printErr']('failed to asynchronously prepare wasm: ' + reason);
abort(reason);
});
}
// Prefer streaming instantiation if available.
if (!Module['wasmBinary'] && typeof WebAssembly.instantiateStreaming === 'function') {
WebAssembly.instantiateStreaming(fetch(wasmBinaryFile, { credentials: 'same-origin' }), info)
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The indentation made this a little hard for me to read (to see where the .s go etc.). How about

WebAssembly.instantiateStreaming(
  fetch(wasmBinaryFile, { credentials: 'same-origin' }), info)
    .then(receiveInstantiatedSource)
    .catch(function(reason) {
      // We expect the most common failure cause to be a bad MIME type for the binary,
      // in which case falling back to ArrayBuffer instantiation should work.
      Module['printErr']('wasm streaming compile failed: ' + reason);
      Module['printErr']('falling back to ArrayBuffer instantiation');
      instantiateArrayBuffer(receiveInstantiatedSource);
    })
);

Also I had to add a ) so I think one might have been missing before.

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Actually, that indentation isn't right because the .then and .catch are not attached to the promise returned by fetch, they go with the return of instantiateStreaming. The fetch's promise is the first argument to instantiateStreaming. (That is also the reason why the number of parens is correct). I did make the .catch line up with the .then though, agreed that's better.

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cool, looks nice.

.then(receiveInstantiatedSource)
.catch(function(reason) {
// We expect the most common failure cause to be a bad MIME type for the binary,
// in which case falling back to ArrayBuffer instantiation should work.
Module['printErr']('wasm streaming compile failed: ' + reason);
Module['printErr']('falling back to ArrayBuffer instantiation');
instantiateArrayBuffer(receiveInstantiatedSource);
});
} else {
instantiateArrayBuffer(receiveInstantiatedSource);
}
return {}; // no exports yet; we'll fill them in later
#else
var instance;
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2 changes: 2 additions & 0 deletions tests/runner.py
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Original file line number Diff line number Diff line change
Expand Up @@ -746,6 +746,8 @@ def do_GET(self):
def log_request(code=0, size=0):
# don't log; too noisy
pass

SimpleHTTPServer.SimpleHTTPRequestHandler.extensions_map['.wasm'] = 'application/wasm'
os.chdir(dir)
httpd = BaseHTTPServer.HTTPServer(('localhost', 8888), TestServerHandler)
httpd.serve_forever() # test runner will kill us
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