syscall/js.FuncOf support

compiler/asserts.go

@@ -42,7 +42,7 @@ func (c *Compiler) emitLookupBoundsCheck(frame *Frame, arrayLen, index llvm.Valu
 
 	// Fail: this is a nil pointer, exit with a panic.
 	c.builder.SetInsertPointAtEnd(faultBlock)
-	c.createRuntimeCall("lookuppanic", nil, "")
+	c.createRuntimeCall("lookupPanic", nil, "")
 	c.builder.CreateUnreachable()
 
 	// Ok: this is a valid pointer.
@@ -103,7 +103,7 @@ func (c *Compiler) emitSliceBoundsCheck(frame *Frame, capacity, low, high llvm.V
 
 	// Fail: this is a nil pointer, exit with a panic.
 	c.builder.SetInsertPointAtEnd(faultBlock)
-	c.createRuntimeCall("slicepanic", nil, "")
+	c.createRuntimeCall("slicePanic", nil, "")
 	c.builder.CreateUnreachable()
 
 	// Ok: this is a valid pointer.
@@ -146,7 +146,7 @@ func (c *Compiler) emitNilCheck(frame *Frame, ptr llvm.Value, blockPrefix string
 
 	// Fail: this is a nil pointer, exit with a panic.
 	c.builder.SetInsertPointAtEnd(faultBlock)
-	c.createRuntimeCall("nilpanic", nil, "")
+	c.createRuntimeCall("nilPanic", nil, "")
 	c.builder.CreateUnreachable()
 
 	// Ok: this is a valid pointer.

compiler/func-lowering.go

@@ -154,17 +154,17 @@ func (c *Compiler) LowerFuncValues() {
 				// What we'll do is transform the following:
 				//     rawPtr := runtime.getFuncPtr(fn)
 				//     if func.rawPtr == nil {
-				//         runtime.nilpanic()
+				//         runtime.nilPanic()
 				//     }
 				//     result := func.rawPtr(...args, func.context)
 				// into this:
 				//     if false {
-				//         runtime.nilpanic()
+				//         runtime.nilPanic()
 				//     }
 				//     var result // Phi
 				//     switch fn.id {
 				//     case 0:
-				//         runtime.nilpanic()
+				//         runtime.nilPanic()
 				//     case 1:
 				//         result = call first implementation...
 				//     case 2:
@@ -222,7 +222,7 @@ func (c *Compiler) LowerFuncValues() {
 				// The 0 case, which is actually a nil check.
 				nilBlock := llvm.InsertBasicBlock(nextBlock, "func.nil")
 				c.builder.SetInsertPointAtEnd(nilBlock)
-				c.createRuntimeCall("nilpanic", nil, "")
+				c.createRuntimeCall("nilPanic", nil, "")
 				c.builder.CreateUnreachable()
 				sw.AddCase(llvm.ConstInt(c.uintptrType, 0, false), nilBlock)
 

compiler/goroutine-lowering.go

@@ -389,7 +389,20 @@ func (c *Compiler) markAsyncFunctions() (needsScheduler bool, err error) {
 
 			c.builder.SetInsertPointBefore(inst)
 
-			parentHandle := f.LastParam()
+			var parentHandle llvm.Value
+			if f.Linkage() == llvm.ExternalLinkage {
+				// Exported function.
+				// Note that getTaskPromisePtr will panic if it is called with
+				// a nil pointer, so blocking exported functions that try to
+				// return anything will not work.
+				parentHandle = llvm.ConstPointerNull(c.i8ptrType)
+			} else {
+				parentHandle = f.LastParam()
+				if parentHandle.IsNil() || parentHandle.Name() != "parentHandle" {
+					// sanity check
+					panic("trying to make exported function async")
+				}
+			}
 
 			// Store return values.
 			switch inst.OperandsCount() {
@@ -417,7 +430,7 @@ func (c *Compiler) markAsyncFunctions() (needsScheduler bool, err error) {
 			// behavior somehow (with the unreachable instruction).
 			continuePoint := c.builder.CreateCall(coroSuspendFunc, []llvm.Value{
 				llvm.ConstNull(c.ctx.TokenType()),
-				llvm.ConstInt(c.ctx.Int1Type(), 1, false),
+				llvm.ConstInt(c.ctx.Int1Type(), 0, false),
 			}, "ret")
 			sw := c.builder.CreateSwitch(continuePoint, frame.suspendBlock, 2)
 			sw.AddCase(llvm.ConstInt(c.ctx.Int8Type(), 0, false), frame.unreachableBlock)
@@ -488,7 +501,7 @@ func (c *Compiler) markAsyncFunctions() (needsScheduler bool, err error) {
 		c.builder.SetInsertPointBefore(deadlockCall)
 		continuePoint := c.builder.CreateCall(coroSuspendFunc, []llvm.Value{
 			llvm.ConstNull(c.ctx.TokenType()),
-			llvm.ConstInt(c.ctx.Int1Type(), 1, false), // final suspend
+			llvm.ConstInt(c.ctx.Int1Type(), 0, false),
 		}, "")
 		c.splitBasicBlock(deadlockCall, llvm.NextBasicBlock(c.builder.GetInsertBlock()), "task.wakeup.dead")
 		c.builder.SetInsertPointBefore(deadlockCall)

src/examples/wasm/Makefile

@@ -3,6 +3,11 @@ export: clean wasm_exec
 	cp ./export/wasm.js ./html/
 	cp ./export/index.html ./html/
 
+callback: clean wasm_exec
+	tinygo build -o ./html/wasm.wasm -target wasm ./callback/wasm.go
+	cp ./callback/wasm.js ./html/
+	cp ./callback/index.html ./html/
+
 main: clean wasm_exec
 	tinygo build -o ./html/wasm.wasm -target wasm ./main/main.go
 	cp ./main/index.html ./html/

src/examples/wasm/callback/index.html

@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+
+<html>
+
+<head>
+	<meta charset="utf-8" />
+	<title>Go WebAssembly</title>
+	<meta name="viewport" content="width=device-width, initial-scale=1" />
+	<script src="wasm_exec.js" defer></script>
+	<script src="wasm.js" defer></script>
+</head>
+
+<body>
+	<h1>WebAssembly</h1>
+	<p>Add two numbers, using WebAssembly:</p>
+	<input type="number" id="a" value="0" /> + <input type="number" id="b" value="0" /> = <input type="number" id="result" readonly />
+</body>
+
+</html>

src/examples/wasm/callback/wasm.go

@@ -0,0 +1,27 @@
+package main
+
+import (
+	"strconv"
+	"syscall/js"
+)
+
+var a, b int
+
+func main() {
+	document := js.Global().Get("document")
+	document.Call("getElementById", "a").Set("oninput", updater(&a))
+	document.Call("getElementById", "b").Set("oninput", updater(&b))
+	update()
+}
+
+func updater(n *int) js.Func {
+	return js.FuncOf(func(this js.Value, args []js.Value) interface{} {
+		*n, _ = strconv.Atoi(this.Get("value").String())
+		update()
+		return nil
+	})
+}
+
+func update() {
+	js.Global().Get("document").Call("getElementById", "result").Set("value", a+b)
+}

src/examples/wasm/callback/wasm.js

@@ -0,0 +1,26 @@
+'use strict';
+
+const WASM_URL = 'wasm.wasm';
+
+var wasm;
+
+function init() {
+  const go = new Go();
+  if ('instantiateStreaming' in WebAssembly) {
+    WebAssembly.instantiateStreaming(fetch(WASM_URL), go.importObject).then(function (obj) {
+      wasm = obj.instance;
+      go.run(wasm);
+    })
+  } else {
+    fetch(WASM_URL).then(resp =>
+      resp.arrayBuffer()
+    ).then(bytes =>
+      WebAssembly.instantiate(bytes, go.importObject).then(function (obj) {
+        wasm = obj.instance;
+        go.run(wasm);
+      })
+    )
+  }
+}
+
+init();

src/runtime/panic.go

@@ -36,16 +36,20 @@ func isnil(ptr *uint8) bool {
 }
 
 // Panic when trying to dereference a nil pointer.
-func nilpanic() {
+func nilPanic() {
 	runtimePanic("nil pointer dereference")
 }
 
 // Panic when trying to acces an array or slice out of bounds.
-func lookuppanic() {
+func lookupPanic() {
 	runtimePanic("index out of range")
 }
 
 // Panic when trying to slice a slice out of bounds.
-func slicepanic() {
+func slicePanic() {
 	runtimePanic("slice out of range")
 }
+
+func blockingPanic() {
+	runtimePanic("trying to do blocking operation in exported function")
+}

src/runtime/runtime_wasm.go

@@ -37,9 +37,16 @@ func putchar(c byte) {
 	resource_write(stdout, &c, 1)
 }
 
+var handleEvent func()
+
 //go:linkname setEventHandler syscall/js.setEventHandler
 func setEventHandler(fn func()) {
-	// TODO
+	handleEvent = fn
+}
+
+//go:export resume
+func resume() {
+	handleEvent()
 }
 
 //go:export go_scheduler

src/runtime/scheduler.go

@@ -120,6 +120,9 @@ func setTaskPromisePtr(task *coroutine, value unsafe.Pointer) {
 // getTaskPromisePtr is a helper function to get the current .ptr field from a
 // coroutine promise.
 func getTaskPromisePtr(task *coroutine) unsafe.Pointer {
+	if task == nil {
+		blockingPanic()
+	}
 	return task.promise().ptr
 }
 

targets/wasm_exec.js

@@ -240,9 +240,9 @@
 					},
 
 					// func valueIndex(v ref, i int) ref
-					//"syscall/js.valueIndex": (sp) => {
-					//	storeValue(sp + 24, Reflect.get(loadValue(sp + 8), getInt64(sp + 16)));
-					//},
+					"syscall/js.valueIndex": (ret_addr, v_addr, i) => {
+						storeValue(ret_addr, Reflect.get(loadValue(v_addr), i));
+					},
 
 					// valueSetIndex(v ref, i int, x ref)
 					//"syscall/js.valueSetIndex": (sp) => {
@@ -291,9 +291,9 @@
 					},
 
 					// func valueLength(v ref) int
-					//"syscall/js.valueLength": (sp) => {
-					//	setInt64(sp + 16, parseInt(loadValue(sp + 8).length));
-					//},
+					"syscall/js.valueLength": (v_addr) => {
+						return loadValue(v_addr).length;
+					},
 
 					// valuePrepareString(v ref) (ref, int)
 					"syscall/js.valuePrepareString": (ret_addr, v_addr) => {
@@ -352,25 +352,23 @@
 			}
 		}
 
-		static _makeCallbackHelper(id, pendingCallbacks, go) {
-			return function () {
-				pendingCallbacks.push({ id: id, args: arguments });
-				go._resolveCallbackPromise();
-			};
+		_resume() {
+			if (this.exited) {
+				throw new Error("Go program has already exited");
+			}
+			this._inst.exports.resume();
+			if (this.exited) {
+				this._resolveExitPromise();
+			}
 		}
 
-		static _makeEventCallbackHelper(preventDefault, stopPropagation, stopImmediatePropagation, fn) {
-			return function (event) {
-				if (preventDefault) {
-					event.preventDefault();
-				}
-				if (stopPropagation) {
-					event.stopPropagation();
-				}
-				if (stopImmediatePropagation) {
-					event.stopImmediatePropagation();
-				}
-				fn(event);
+		_makeFuncWrapper(id) {
+			const go = this;
+			return function () {
+				const event = { id: id, this: this, args: arguments };
+				go._pendingEvent = event;
+				go._resume();
+				return event.result;
 			};
 		}
 	}