Implement timeout argument in wasm2js_atomic_wait_i32 (#4385)

Also, fix bug where pointer was being used direcltly to
index into Int32Array.  I suppose this code had basically
zero users until I tried to land this change in emscripten:
https://github.com/emscripten-core/emscripten/pull/15742

1 files changed, 7 insertions, 2 deletions

diff --git a/src/wasm2js.h b/src/wasm2js.h
index 7c9bef0ba..615e47268 100644
--- a/src/wasm2js.h
+++ b/src/wasm2js.h
@@ -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);
+    }
     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;