Proxy webgpu calls back to the main thread. NFC

Until we have real multi-threaded webgpu support this is probable
the best we can do.

I tested these locally. I don't think we actually have WebGPU support
in our CI yet, but that is something else I'm working on.

Fixes: #19645

src/library_html5_webgpu.js

@@ -90,4 +90,8 @@ var LibraryHTML5WebGPU = {
 {{{ html5_gpu.makeImportExport('render_bundle_encoder', 'RenderBundleEncoder') }}}
 {{{ html5_gpu.makeImportExport('render_bundle', 'RenderBundle') }}}
 
+for (const key of Object.keys(LibraryHTML5WebGPU)) {
+  LibraryHTML5WebGPU[key + '__proxy'] = 'sync';
+}
+
 addToLibrary(LibraryHTML5WebGPU);

src/library_webgpu.js

@@ -2196,7 +2196,7 @@ var LibraryWebGPU = {
 #endif
 
     var bundles = Array.from(HEAP32.subarray(bundlesPtr >> 2, (bundlesPtr >> 2) + count),
-      function(id) { return WebGPU.mgrRenderBundle.get(id); });
+      (id) => WebGPU.mgrRenderBundle.get(id));
     pass["executeBundles"](bundles);
   },
 
@@ -2582,23 +2582,22 @@ var LibraryWebGPU = {
     var device = WebGPU.mgrDevice.get(deviceId);
     var context = WebGPU.mgrSurface.get(surfaceId);
 
-
 #if ASSERTIONS
     assert({{{ gpu.PresentMode.Fifo }}} ===
       {{{ gpu.makeGetU32('descriptor', C_STRUCTS.WGPUSwapChainDescriptor.presentMode) }}});
 #endif
 
     var canvasSize = [
-        {{{ gpu.makeGetU32('descriptor', C_STRUCTS.WGPUSwapChainDescriptor.width) }}},
-        {{{ gpu.makeGetU32('descriptor', C_STRUCTS.WGPUSwapChainDescriptor.height) }}}
+      {{{ gpu.makeGetU32('descriptor', C_STRUCTS.WGPUSwapChainDescriptor.width) }}},
+      {{{ gpu.makeGetU32('descriptor', C_STRUCTS.WGPUSwapChainDescriptor.height) }}}
     ];
 
     if (canvasSize[0] !== 0) {
-        context["canvas"]["width"] = canvasSize[0];
+      context["canvas"]["width"] = canvasSize[0];
     }
 
     if (canvasSize[1] !== 0) {
-        context["canvas"]["height"] = canvasSize[1];
+      context["canvas"]["height"] = canvasSize[1];
     }
 
     var configuration = {
@@ -2642,6 +2641,7 @@ for (var value in LibraryWebGPU.$WebGPU.FeatureName) {
 
 for (const key of Object.keys(LibraryWebGPU)) {
   LibraryWebGPU[key + '__i53abi'] = true;
+  LibraryWebGPU[key + '__proxy'] = 'sync';
 }
 
 autoAddDeps(LibraryWebGPU, '$WebGPU');

test/test_browser.py

@@ -4661,9 +4661,18 @@ def test_webgl_simple_enable_extensions(self):
   def test_webgpu_basic_rendering(self, args):
     self.btest_exit('webgpu_basic_rendering.cpp', args=['-sUSE_WEBGPU'] + args)
 
+  @requires_graphics_hardware
+  @requires_threads
+  def test_webgpu_basic_rendering_pthreads(self):
+    self.btest_exit('webgpu_basic_rendering.cpp', args=['-sUSE_WEBGPU', '-pthread', '-sPROXY_TO_PTHREAD'])
+
   def test_webgpu_get_device(self):
     self.btest_exit('webgpu_get_device.cpp', args=['-sUSE_WEBGPU', '-sASSERTIONS', '--closure=1'])
 
+  @requires_threads
+  def test_webgpu_get_device_pthreads(self):
+    self.btest_exit('webgpu_get_device.cpp', args=['-sUSE_WEBGPU', '-pthread', '-sPROXY_TO_PTHREAD'])
+
   # Tests the feature that shell html page can preallocate the typed array and place it
   # to Module.buffer before loading the script page.
   # In this build mode, the -sINITIAL_MEMORY=xxx option will be ignored.

test/webgpu_get_device.cpp

@@ -1,9 +1,16 @@
-#include <emscripten.h>
+#include <stdio.h>
+
+#include <emscripten/em_asm.h>
 #include <emscripten/html5_webgpu.h>
 
-int main() {
+__attribute__((constructor)) void init() {
   EM_ASM({
     Module['preinitializedWebGPUDevice'] = { this_is: 'a_dummy_object' };
   });
-  emscripten_webgpu_get_device();
+}
+
+int main() {
+  WGPUDevice d = emscripten_webgpu_get_device();
+  printf("emscripten_webgpu_get_device: %p\n", d);
+  return 0;
 }