wasm: add recover() support

builder/build.go

@@ -747,6 +747,7 @@ func Build(pkgName, outpath, tmpdir string, config *compileopts.Config) (BuildRe
 			}
 			ldflags = append(ldflags, "-mllvm", "-mcpu="+config.CPU())
 			ldflags = append(ldflags, "-mllvm", "-mattr="+config.Features()) // needed for MIPS softfloat
+			ldflags = append(ldflags, "-mllvm", "-wasm-enable-eh")
 			if config.GOOS() == "windows" {
 				// Options for the MinGW wrapper for the lld COFF linker.
 				ldflags = append(ldflags,

compiler/calls.go

@@ -70,21 +70,25 @@ func (b *builder) createRuntimeInvoke(fnName string, args []llvm.Value, name str
 // createCall creates a call to the given function with the arguments possibly
 // expanded.
 func (b *builder) createCall(fnType llvm.Type, fn llvm.Value, args []llvm.Value, name string) llvm.Value {
-	expanded := make([]llvm.Value, 0, len(args))
-	for _, arg := range args {
-		fragments := b.expandFormalParam(arg)
-		expanded = append(expanded, fragments...)
-	}
-	return b.CreateCall(fnType, fn, expanded, name)
+	return b.CreateCall(fnType, fn, b.expandFormalParams(args), name)
 }
 
 // createInvoke is like createCall but continues execution at the landing pad if
 // the call resulted in a panic.
 func (b *builder) createInvoke(fnType llvm.Type, fn llvm.Value, args []llvm.Value, name string) llvm.Value {
-	if b.hasDeferFrame() {
+	switch b.deferFrameType() {
+	case recoverInlineAsm:
 		b.createInvokeCheckpoint()
+		return b.createCall(fnType, fn, args, name)
+	case recoverWasmEH:
+		continueBB := b.insertBasicBlock("invoke.cont")
+		call := b.CreateInvoke(fnType, fn, b.expandFormalParams(args), continueBB, b.landingpad, name)
+		b.SetInsertPointAtEnd(continueBB)
+		b.blockExits[b.currentBlock] = continueBB
+		return call
+	default:
+		return b.createCall(fnType, fn, args, name)
 	}
-	return b.createCall(fnType, fn, args, name)
 }
 
 // Expand an argument type to a list that can be used in a function call
@@ -123,6 +127,17 @@ func (b *builder) expandFormalParamOffsets(t llvm.Type) []uint64 {
 	}
 }
 
+// expandFormalParams expands every param in the params slice like
+// expandFormalParam.
+func (b *builder) expandFormalParams(params []llvm.Value) []llvm.Value {
+	expanded := make([]llvm.Value, 0, len(params))
+	for _, arg := range params {
+		fragments := b.expandFormalParam(arg)
+		expanded = append(expanded, fragments...)
+	}
+	return expanded
+}
+
 // expandFormalParam splits a formal param value into pieces, so it can be
 // passed directly as part of a function call. For example, it splits up small
 // structs into individual fields. It is the equivalent of expandFormalParamType

compiler/compiler.go

@@ -355,7 +355,10 @@ func CompilePackage(moduleName string, pkg *loader.Package, ssaPkg *ssa.Package,
 }
 
 func (c *compilerContext) getRuntimeType(name string) types.Type {
-	return c.runtimePkg.Scope().Lookup(name).(*types.TypeName).Type()
+	if typ, ok := c.runtimePkg.Scope().Lookup(name).(*types.TypeName); ok {
+		return typ.Type()
+	}
+	panic("runtime type not found: " + name)
 }
 
 // getLLVMRuntimeType obtains a named type from the runtime package and returns
@@ -1350,7 +1353,7 @@ func (b *builder) createFunction() {
 		b.CreateBr(b.afterDefersBlock[i])
 	}
 
-	if b.hasDeferFrame() {
+	if b.deferFrameType() != recoverNone {
 		// Create the landing pad block, where execution continues after a
 		// panic.
 		b.createLandingPad()
@@ -1487,8 +1490,11 @@ func (b *builder) createInstruction(instr ssa.Instruction) {
 		b.createRuntimeInvoke("_panic", []llvm.Value{value}, "")
 		b.CreateUnreachable()
 	case *ssa.Return:
-		if b.hasDeferFrame() {
-			b.createRuntimeCall("destroyDeferFrame", []llvm.Value{b.deferFrame}, "")
+		switch b.deferFrameType() {
+		case recoverInlineAsm:
+			b.createRuntimeCall("destroyDeferFrameInlineAsm", []llvm.Value{b.deferFrame}, "")
+		case recoverWasmEH:
+			b.createRuntimeCall("destroyDeferFrameWasmEH", []llvm.Value{b.deferFrame}, "")
 		}
 		if len(instr.Results) == 0 {
 			b.CreateRetVoid()
@@ -1741,7 +1747,7 @@ func (b *builder) createBuiltin(argTypes []types.Type, argValues []llvm.Value, c
 		return b.CreateExtractValue(cplx, 0, "real"), nil
 	case "recover":
 		useParentFrame := uint64(0)
-		if b.hasDeferFrame() {
+		if b.fn.Recover != nil {
 			// recover() should return the panic value of the parent function,
 			// not of the current function.
 			useParentFrame = 1
@@ -1851,11 +1857,8 @@ func (b *builder) createFunctionCall(instr *ssa.CallCommon) (llvm.Value, error)
 		case strings.HasPrefix(name, "syscall.rawSyscallNoError") || strings.HasPrefix(name, "golang.org/x/sys/unix.RawSyscallNoError"):
 			return b.createRawSyscallNoError(instr)
 		case name == "runtime.supportsRecover":
-			supportsRecover := uint64(0)
-			if b.supportsRecover() {
-				supportsRecover = 1
-			}
-			return llvm.ConstInt(b.ctx.Int1Type(), supportsRecover, false), nil
+			supportsRecover := uint64(b.supportsRecover())
+			return llvm.ConstInt(b.ctx.Int8Type(), supportsRecover, false), nil
 		case name == "runtime.panicStrategy":
 			// These constants are defined in src/runtime/panic.go.
 			panicStrategy := map[string]uint64{

compiler/compiler_test.go

@@ -44,6 +44,7 @@ func TestCompiler(t *testing.T) {
 		{"interface.go", "", ""},
 		{"func.go", "", ""},
 		{"defer.go", "cortex-m-qemu", ""},
+		{"defer.go", "wasm", "none"},
 		{"pragma.go", "", ""},
 		{"goroutine.go", "wasm", "asyncify"},
 		{"goroutine.go", "cortex-m-qemu", "tasks"},