Support a few simple WebGPU entry points (via dawn.h)

src/library_webgpu.js

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2019 The Emscripten Authors.  All rights reserved.
+ * Emscripten is available under two separate licenses, the MIT license and the
+ * University of Illinois/NCSA Open Source License.  Both these licenses can be
+ * found in the LICENSE file.
+ *
+ * WebGPU support. (TODO: Add documentation.)
+ */
+var LibraryWebGPU = {
+  $WebGPU: {
+    buffers: {
+      nextId: 1,
+      objects: []
+    },
+  },
+
+  dawnDeviceRelease: function() {
+    console.warn("dawnDeviceRelease not implemented");
+  },
+
+  dawnDeviceCreateBuffer: function(deviceId, descriptor) {
+#if ASSERTIONS
+    assert(deviceId === 1);
+    assert(descriptor !== 0);
+    var nextInChain = {{{ makeGetValue('descriptor', C_STRUCTS.DawnBufferDescriptor.nextInChain, '*') }}};
+    assert(nextInChain === 0);
+#endif
+    var desc = {
+      usage: {{{ makeGetValue('descriptor', C_STRUCTS.DawnBufferDescriptor.usage, 'i64') }}},
+      size: {{{ makeGetValue('descriptor', C_STRUCTS.DawnBufferDescriptor.size, 'i64') }}},
+    };
+
+    var buffer = Module['preinitializedWebGPUDevice'].createBuffer(desc);
+
+    var id = WebGPU.buffers.nextId;
+    WebGPU.buffers.nextId++;
+    WebGPU.buffers.objects[id] = { refcount: 1, object: buffer };
+    return id;
+  },
+
+  dawnBufferRelease: function(bufferId) {
+    var b = WebGPU.buffers.objects[bufferId];
+    b.refcount--;
+    if (b.refcount === 0) {
+      WebGPU.buffers.objects[bufferId] = undefined;
+    }
+  },
+
+  dawnBufferSetSubData: function(bufferId, start_l, start_h, count_l, count_h, data) {
+    var buffer = WebGPU.buffers.objects[bufferId].object;
+#if ASSERTIONS
+    assert(buffer);
+    assert(start_h < 0x200000);
+    assert(count_h < 0x200000);
+#endif
+    var start = start_h * 0x100000000 + start_l;
+    var count = count_h * 0x100000000 + count_l;
+    buffer.setSubData(start, HEAPU8, data, count);
+  },
+
+  dawnBufferMapReadAsync: function(bufferId, callback, userdata) {
+    var buffer = WebGPU.buffers.objects[bufferId].object;
+#if ASSERTIONS
+    assert(buffer);
+    assert(callback);
+#endif
+    buffer.mapReadAsync().then(function(mapped) {
+      var DAWN_BUFFER_MAP_ASYNC_STATUS_SUCCESS = 0;
+      var data = _malloc(mapped.byteLength);
+      HEAP8.set(new Uint8Array(mapped), data);
+      var dataLength_h = (mapped.byteLength / 0x100000000) | 0;
+      var dataLength_l = mapped.byteLength | 0;
+      dynCall('viiji', callback, [DAWN_BUFFER_MAP_ASYNC_STATUS_SUCCESS, data, dataLength_l, dataLength_h, userdata]);
+    }, function() {
+      // TODO(kainino0x): Figure out how to pick other error status values.
+      var DAWN_BUFFER_MAP_ASYNC_STATUS_ERROR = 1;
+      dynCall('viiji', callback, [DAWN_BUFFER_MAP_ASYNC_STATUS_ERROR, 0, 0, 0, userdata]);
+    });
+  },
+};
+
+autoAddDeps(LibraryWebGPU, '$WebGPU');
+
+mergeInto(LibraryManager.library, LibraryWebGPU);

src/modules.js

@@ -113,6 +113,7 @@ var LibraryManager = {
     if (!STRICT && !MINIMAL_RUNTIME) {
       libraries = libraries.concat([
         'library_webgl.js',
+        'library_webgpu.js',
         'library_openal.js',
         'library_vr.js',
         'library_sdl.js',

src/settings.js

@@ -440,6 +440,9 @@ var GL_FFP_ONLY = 0;
 // WebGL initialization afterwards will use this GL context to render.
 var GL_PREINITIALIZED_CONTEXT = 0;
 
+// If true, enables WebGPU support via dawn.h.
+var WEBGPU = 0;
+
 // Enables building of stb-image, a tiny public-domain library for decoding
 // images, allowing decoding of images without using the browser's built-in
 // decoders. The benefit is that this can be done synchronously, however, it

src/struct_info.json

@@ -1615,5 +1615,19 @@
             "EMSCRIPTEN_FETCH_SYNCHRONOUS",
             "EMSCRIPTEN_FETCH_WAITABLE"
         ]
+    },
+    // ===========================================
+    // WebGPU
+    // ===========================================
+    {
+        "file": "dawn/dawn.h",
+        "defines": [],
+        "structs": {
+            "DawnBufferDescriptor": [
+                "nextInChain",
+                "usage",
+                "size"
+            ]
+        }
     }
  ]

src/support.js

@@ -904,7 +904,7 @@ function makeBigInt(low, high, unsigned) {
 function dynCall(sig, ptr, args) {
   if (args && args.length) {
 #if ASSERTIONS
-    assert(args.length == sig.length-1);
+    assert(args.length === sig.substring(1).replace(/j/g, '--').length);
 #endif
 #if ASSERTIONS
     assert(('dynCall_' + sig) in Module, 'bad function pointer type - no table for sig \'' + sig + '\'');