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Implement timeout argument in wasm2js_atomic_wait_i32 #4385

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Merged
sbc100 merged 1 commit into from
Dec 11, 2021
Merged

Implement timeout argument in wasm2js_atomic_wait_i32 #4385

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9 changes: 7 additions & 2 deletions src/wasm2js.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2856,9 +2856,14 @@ void Wasm2JSGlue::emitSpecialSupport() {
} else if (import->base == ABI::wasm2js::ATOMIC_WAIT_I32) {
out << R"(
function wasm2js_atomic_wait_i32(ptr, expected, timeoutLow, timeoutHigh) {
if (timeoutLow != -1 || timeoutHigh != -1) throw 'unsupported timeout';
var timeout = Infinity;
if (timeoutHigh >= 0) {
// Convert from nanoseconds to milliseconds
// Taken from convertI32PairToI53 in emscripten's library_int53.js
timeout = ((timeoutLow / 1e6) >>> 0) + timeoutHigh * (4294967296 / 1e6);
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@kripken kripken Dec 13, 2021

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I think maybe (timeoutLow / 1e6) >>> 0 should be (timeoutLow >>> 0) / 1e6. That would allow timeouts of less than 1ms as the current code rounds the output.

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@MaxGraey MaxGraey Dec 13, 2021 •
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I thought of that too at first, but it looks like the timeout cannot be sub-millisecond according to the specification. timeout is rational (ℝ) value:

  1. Let q be ? ToNumber(timeout).
  2. If q is NaN or +∞𝔽, let t be +∞; else if q is -∞𝔽, let t be 0; else let t be max(ℝ(q), 0).

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@kripken kripken Dec 13, 2021

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Hmm, maybe this differs between countries, but isn't ℝ the set of real numbers, not rational? See wikipedia, The rational numbers (Q) are included in the real numbers (R) (link)

JS does a ToNumber, so it converts to a double, and sub-millisecond values are allowed IIUC

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@MaxGraey MaxGraey Dec 13, 2021 •
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Ah, right! I got confused with natural (ℕ).

}
var view = new Int32Array(bufferView.buffer); // TODO cache
var result = Atomics.wait(view, ptr, expected);
var result = Atomics.wait(view, ptr >> 2, expected, timeout);
if (result == 'ok') return 0;
if (result == 'not-equal') return 1;
if (result == 'timed-out') return 2;
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9 changes: 7 additions & 2 deletions test/wasm2js/atomics_32.2asm.js
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Expand Up @@ -30,9 +30,14 @@ memorySegments[1] = base64DecodeToExistingUint8Array(new Uint8Array(6), 0, "d29y
var f64ScratchView = new Float64Array(scratchBuffer);

function wasm2js_atomic_wait_i32(ptr, expected, timeoutLow, timeoutHigh) {
if (timeoutLow != -1 || timeoutHigh != -1) throw 'unsupported timeout';
var timeout = Infinity;
if (timeoutHigh >= 0) {
// Convert from nanoseconds to milliseconds
// Taken from convertI32PairToI53 in emscripten's library_int53.js
timeout = ((timeoutLow / 1e6) >>> 0) + timeoutHigh * (4294967296 / 1e6);
}
var view = new Int32Array(bufferView.buffer); // TODO cache
var result = Atomics.wait(view, ptr, expected);
var result = Atomics.wait(view, ptr >> 2, expected, timeout);
if (result == 'ok') return 0;
if (result == 'not-equal') return 1;
if (result == 'timed-out') return 2;
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9 changes: 7 additions & 2 deletions test/wasm2js/atomics_32.2asm.js.opt
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Original file line number Diff line number Diff line change
Expand Up @@ -30,9 +30,14 @@ memorySegments[1] = base64DecodeToExistingUint8Array(new Uint8Array(6), 0, "d29y
var f64ScratchView = new Float64Array(scratchBuffer);

function wasm2js_atomic_wait_i32(ptr, expected, timeoutLow, timeoutHigh) {
if (timeoutLow != -1 || timeoutHigh != -1) throw 'unsupported timeout';
var timeout = Infinity;
if (timeoutHigh >= 0) {
// Convert from nanoseconds to milliseconds
// Taken from convertI32PairToI53 in emscripten's library_int53.js
timeout = ((timeoutLow / 1e6) >>> 0) + timeoutHigh * (4294967296 / 1e6);
}
var view = new Int32Array(bufferView.buffer); // TODO cache
var result = Atomics.wait(view, ptr, expected);
var result = Atomics.wait(view, ptr >> 2, expected, timeout);
if (result == 'ok') return 0;
if (result == 'not-equal') return 1;
if (result == 'timed-out') return 2;
Expand Down