Merge pull request #666 from cpunion/async-functions

Async functions
2024-08-06 20:38:34 +08:00
parent 43fd5d233a 7b2747ce0c
commit ee0e0a5c51
25 changed files with 2019 additions and 486 deletions
--- a/ssa/cl_test.go
+++ b/ssa/cl_test.go
@@ -50,7 +50,7 @@ func TestFromTestrt(t *testing.T) {
 }

 func TestFromTestdata(t *testing.T) {
-	cltest.FromDir(t, "", "../cl/_testdata", false)
+	cltest.FromDir(t, "", "../cl/_testdata", true)
 }

 func TestMakeInterface(t *testing.T) {
--- a/ssa/coro.go
+++ b/ssa/coro.go
@@ -0,0 +1,690 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package ssa
+
+import (
+	"fmt"
+	"go/constant"
+	"go/token"
+	"go/types"
+)
+
+// declare void @llvm.coro.destroy(ptr <handle>)
+// declare void @llvm.coro.resume(ptr <handle>)
+// declare i1 @llvm.coro.done(ptr <handle>)
+// declare ptr @llvm.coro.promise(ptr <ptr>, i32 <alignment>, i1 <from>)
+// declare i32 @llvm.coro.size.i32()
+// declare i64 @llvm.coro.size.i64()
+// declare i32 @llvm.coro.align.i32()
+// declare i64 @llvm.coro.align.i64()
+// declare ptr @llvm.coro.begin(token <id>, ptr <mem>)
+// declare ptr @llvm.coro.free(token %id, ptr <frame>)
+// declare i1 @llvm.coro.alloc(token <id>)
+// declare ptr @llvm.coro.noop()
+// declare ptr @llvm.coro.frame()
+// declare token @llvm.coro.id(i32 <align>, ptr <promise>, ptr <coroaddr>, ptr <fnaddrs>)
+// declare token @llvm.coro.id.async(i32 <context size>, i32 <align>, ptr <context arg>, ptr <async function pointer>)
+// declare token @llvm.coro.id.retcon(i32 <size>, i32 <align>, ptr <buffer>, ptr <continuation prototype>, ptr <alloc>, ptr <dealloc>)
+// declare token @llvm.coro.id.retcon.once(i32 <size>, i32 <align>, ptr <buffer>, ptr <prototype>, ptr <alloc>, ptr <dealloc>)
+// declare i1 @llvm.coro.end(ptr <handle>, i1 <unwind>, token <result.token>)
+// declare token @llvm.coro.end.results(...)
+// declare i1 @llvm.coro.end.async(ptr <handle>, i1 <unwind>, ...)
+// declare i8 @llvm.coro.suspend(token <save>, i1 <final>)
+// declare token @llvm.coro.save(ptr <handle>)
+// declare {ptr, ptr, ptr} @llvm.coro.suspend.async(ptr <resume function>, ptr <context projection function>, ... <function to call> ... <arguments to function>)
+// declare ptr @llvm.coro.prepare.async(ptr <coroutine function>)
+// declare i1 @llvm.coro.suspend.retcon(...)
+// declare void @await_suspend_function(ptr %awaiter, ptr %hdl)
+// declare void @llvm.coro.await.suspend.void(ptr <awaiter>, ptr <handle>, ptr <await_suspend_function>)
+// declare i1 @llvm.coro.await.suspend.bool(ptr <awaiter>, ptr <handle>, ptr <await_suspend_function>)
+// declare void @llvm.coro.await.suspend.handle(ptr <awaiter>, ptr <handle>, ptr <await_suspend_function>)
+
+// -----------------------------------------------------------------------------
+
+// declare void @llvm.coro.destroy(ptr <handle>)
+func (p Program) tyCoDestroy() *types.Signature {
+	if p.coDestroyTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i8Ptr)
+		p.coDestroyTy = types.NewSignatureType(nil, nil, nil, params, nil, false)
+	}
+	return p.coDestroyTy
+}
+
+// declare void @llvm.coro.resume(ptr <handle>)
+func (p Program) tyCoResume() *types.Signature {
+	if p.coResumeTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i8Ptr)
+		p.coResumeTy = types.NewSignatureType(nil, nil, nil, params, nil, false)
+	}
+	return p.coResumeTy
+}
+
+// declare i1 @llvm.coro.done(ptr <handle>)
+func (p Program) tyCoDone() *types.Signature {
+	if p.coDoneTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i8Ptr)
+		results := types.NewTuple(types.NewParam(token.NoPos, nil, "", p.Bool().raw.Type))
+		p.coDoneTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coDoneTy
+}
+
+// declare ptr @llvm.coro.promise(ptr <ptr>, i32 <alignment>, i1 <from>)
+func (p Program) tyCoPromise() *types.Signature {
+	if p.coPromiseTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		i32 := types.NewParam(token.NoPos, nil, "", p.Int32().raw.Type)
+		boolParam := types.NewParam(token.NoPos, nil, "", p.Bool().raw.Type)
+		params := types.NewTuple(i8Ptr, i32, boolParam)
+		results := types.NewTuple(i8Ptr)
+		p.coPromiseTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coPromiseTy
+}
+
+// declare i32 @llvm.coro.size.i32()
+func (p Program) tyCoSizeI32() *types.Signature {
+	if p.coSizeI32Ty == nil {
+		results := types.NewTuple(types.NewParam(token.NoPos, nil, "", p.Int32().raw.Type))
+		p.coSizeI32Ty = types.NewSignatureType(nil, nil, nil, nil, results, false)
+	}
+	return p.coSizeI32Ty
+}
+
+// declare i64 @llvm.coro.size.i64()
+func (p Program) tyCoSizeI64() *types.Signature {
+	if p.coSizeI64Ty == nil {
+		results := types.NewTuple(types.NewParam(token.NoPos, nil, "", p.Int64().raw.Type))
+		p.coSizeI64Ty = types.NewSignatureType(nil, nil, nil, nil, results, false)
+	}
+	return p.coSizeI64Ty
+}
+
+// declare i32 @llvm.coro.align.i32()
+func (p Program) tyCoAlignI32() *types.Signature {
+	if p.coAlignI32Ty == nil {
+		results := types.NewTuple(types.NewParam(token.NoPos, nil, "", p.Int32().raw.Type))
+		p.coAlignI32Ty = types.NewSignatureType(nil, nil, nil, nil, results, false)
+	}
+	return p.coAlignI32Ty
+}
+
+// declare i64 @llvm.coro.align.i64()
+func (p Program) tyCoAlignI64() *types.Signature {
+	if p.coAlignI64Ty == nil {
+		results := types.NewTuple(types.NewParam(token.NoPos, nil, "", p.Int64().raw.Type))
+		p.coAlignI64Ty = types.NewSignatureType(nil, nil, nil, nil, results, false)
+	}
+	return p.coAlignI64Ty
+}
+
+// declare ptr @llvm.coro.begin(token <id>, ptr <mem>)
+func (p Program) tyCoBegin() *types.Signature {
+	if p.coBeginTy == nil {
+		tokenParam := types.NewParam(token.NoPos, nil, "", p.Token().raw.Type)
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(tokenParam, i8Ptr)
+		results := types.NewTuple(i8Ptr)
+		p.coBeginTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coBeginTy
+}
+
+// declare ptr @llvm.coro.free(token %id, ptr <frame>)
+func (p Program) tyCoFree() *types.Signature {
+	if p.coFreeTy == nil {
+		tokenParam := types.NewParam(token.NoPos, nil, "", p.Token().raw.Type)
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(tokenParam, i8Ptr)
+		results := types.NewTuple(i8Ptr)
+		p.coFreeTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coFreeTy
+}
+
+// declare i1 @llvm.coro.alloc(token <id>)
+func (p Program) tyCoAlloc() *types.Signature {
+	if p.coAllocTy == nil {
+		tokenParam := types.NewParam(token.NoPos, nil, "", p.Token().raw.Type)
+		params := types.NewTuple(tokenParam)
+		boolParam := types.NewParam(token.NoPos, nil, "", p.Bool().raw.Type)
+		results := types.NewTuple(boolParam)
+		p.coAllocTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coAllocTy
+}
+
+// declare ptr @llvm.coro.noop()
+func (p Program) tyCoNoop() *types.Signature {
+	if p.coNoopTy == nil {
+		results := types.NewTuple(types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type))
+		p.coNoopTy = types.NewSignatureType(nil, nil, nil, nil, results, false)
+	}
+	return p.coNoopTy
+}
+
+// declare ptr @llvm.coro.frame()
+func (p Program) tyCoFrame() *types.Signature {
+	if p.coFrameTy == nil {
+		results := types.NewTuple(types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type))
+		p.coFrameTy = types.NewSignatureType(nil, nil, nil, nil, results, false)
+	}
+	return p.coFrameTy
+}
+
+// declare token @llvm.coro.id(i32 <align>, ptr <promise>, ptr <coroaddr>, ptr <fnaddrs>)
+func (p Program) tyCoID() *types.Signature {
+	if p.coIDTy == nil {
+		i32 := types.NewParam(token.NoPos, nil, "", p.Int32().raw.Type)
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i32, i8Ptr, i8Ptr, i8Ptr)
+		tokenParam := types.NewParam(token.NoPos, nil, "", p.Token().raw.Type)
+		results := types.NewTuple(tokenParam)
+		p.coIDTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coIDTy
+}
+
+/*
+// declare token @llvm.coro.id.async(i32 <context size>, i32 <align>, ptr <context arg>, ptr <async function pointer>)
+func (p Program) tyCoIDAsync() *types.Signature {
+	if p.coIDAsyncTy == nil {
+		i32 := types.NewParam(token.NoPos, nil, "", p.Int32().raw.Type)
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i32, i32, i8Ptr, i8Ptr)
+		tokenParam := types.NewParam(token.NoPos, nil, "", p.Token().raw.Type)
+		results := types.NewTuple(tokenParam)
+		p.coIDAsyncTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coIDAsyncTy
+}
+
+// declare token @llvm.coro.id.retcon(i32 <size>, i32 <align>, ptr <buffer>, ptr <continuation prototype>, ptr <alloc>, ptr <dealloc>)
+func (p Program) tyCoIDRetcon() *types.Signature {
+	if p.coIDRetconTy == nil {
+		i32 := types.NewParam(token.NoPos, nil, "", p.Int32().raw.Type)
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i32, i32, i8Ptr, i8Ptr, i8Ptr, i8Ptr)
+		tokenParam := types.NewParam(token.NoPos, nil, "", p.Token().raw.Type)
+		results := types.NewTuple(tokenParam)
+		p.coIDRetconTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coIDRetconTy
+}
+
+// declare token @llvm.coro.id.retcon.once(i32 <size>, i32 <align>, ptr <buffer>, ptr <prototype>, ptr <alloc>, ptr <dealloc>)
+func (p Program) tyCoIDRetconOnce() *types.Signature {
+	if p.coIDRetconOnceTy == nil {
+		i32 := types.NewParam(token.NoPos, nil, "", p.Int32().raw.Type)
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i32, i32, i8Ptr, i8Ptr, i8Ptr, i8Ptr)
+		tokenParam := types.NewParam(token.NoPos, nil, "", p.Token().raw.Type)
+		results := types.NewTuple(tokenParam)
+		p.coIDRetconOnceTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coIDRetconOnceTy
+}
+*/
+
+// declare i1 @llvm.coro.end(ptr <handle>, i1 <unwind>, token <result.token>)
+func (p Program) tyCoEnd() *types.Signature {
+	if p.coEndTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		boolParam := types.NewParam(token.NoPos, nil, "", p.Bool().raw.Type)
+		tokenParam := types.NewParam(token.NoPos, nil, "", p.Token().raw.Type)
+		params := types.NewTuple(i8Ptr, boolParam, tokenParam)
+		results := types.NewTuple(boolParam)
+		p.coEndTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coEndTy
+}
+
+/*
+// TODO(lijie): varargs
+// declare token @llvm.coro.end.results(...)
+func (p Program) tyCoEndResults() *types.Signature {
+	panic("not implemented")
+}
+
+// TODO(lijie): varargs
+// declare i1 @llvm.coro.end.async(ptr <handle>, i1 <unwind>, ...)
+func (p Program) tyCoEndAsync() *types.Signature {
+	panic("not implemented")
+}
+*/
+
+// declare i8 @llvm.coro.suspend(token <save>, i1 <final>)
+func (p Program) tyCoSuspend() *types.Signature {
+	if p.coSuspendTy == nil {
+		tokenParam := types.NewParam(token.NoPos, nil, "", p.Token().raw.Type)
+		boolParam := types.NewParam(token.NoPos, nil, "", p.Bool().raw.Type)
+		params := types.NewTuple(tokenParam, boolParam)
+		paramByte := types.NewParam(token.NoPos, nil, "", p.Byte().raw.Type)
+		results := types.NewTuple(paramByte)
+		p.coSuspendTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coSuspendTy
+}
+
+/*
+// declare token @llvm.coro.save(ptr <handle>)
+func (p Program) tyCoSave() *types.Signature {
+	if p.coSaveTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i8Ptr)
+		tokenParam := types.NewParam(token.NoPos, nil, "", p.Token().raw.Type)
+		results := types.NewTuple(tokenParam)
+		p.coSaveTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coSaveTy
+}
+
+// TODO(lijie): varargs
+// declare {ptr, ptr, ptr} @llvm.coro.suspend.async(ptr <resume function>, ptr <context projection function>, ... <function to call> ... <arguments to function>)
+func (p Program) tyCoSuspendAsync() *types.Signature {
+	panic("not implemented")
+}
+
+// declare ptr @llvm.coro.prepare.async(ptr <coroutine function>)
+func (p Program) tyCoPrepareAsync() *types.Signature {
+	if p.coPrepareAsyncTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i8Ptr)
+		results := types.NewTuple(i8Ptr)
+		p.coPrepareAsyncTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coPrepareAsyncTy
+}
+
+// declare i1 @llvm.coro.suspend.retcon(...)
+func (p Program) tyCoSuspendRetcon() *types.Signature {
+	panic("not implemented")
+}
+
+// declare void @await_suspend_function(ptr %awaiter, ptr %hdl)
+func (p Program) tyCoAwaitSuspendFunction() *types.Signature {
+	if p.coAwaitSuspendFunctionTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i8Ptr, i8Ptr)
+		p.coAwaitSuspendFunctionTy = types.NewSignatureType(nil, nil, nil, params, nil, false)
+	}
+	return p.coAwaitSuspendFunctionTy
+}
+
+// declare void @llvm.coro.await.suspend.void(ptr <awaiter>, ptr <handle>, ptr <await_suspend_function>)
+func (p Program) tyCoAwaitSuspendVoid() *types.Signature {
+	if p.coAwaitSuspendVoidTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i8Ptr, i8Ptr, i8Ptr)
+		p.coAwaitSuspendVoidTy = types.NewSignatureType(nil, nil, nil, params, nil, false)
+	}
+	return p.coAwaitSuspendVoidTy
+}
+
+// declare i1 @llvm.coro.await.suspend.bool(ptr <awaiter>, ptr <handle>, ptr <await_suspend_function>)
+func (p Program) tyCoAwaitSuspendBool() *types.Signature {
+	if p.coAwaitSuspendBoolTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i8Ptr, i8Ptr, i8Ptr)
+		results := types.NewTuple(types.NewParam(token.NoPos, nil, "", p.Bool().raw.Type))
+		p.coAwaitSuspendBoolTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.coAwaitSuspendBoolTy
+}
+
+// declare void @llvm.coro.await.suspend.handle(ptr <awaiter>, ptr <handle>, ptr <await_suspend_function>)
+func (p Program) tyCoAwaitSuspendHandle() *types.Signature {
+	if p.coAwaitSuspendHandleTy == nil {
+		i8Ptr := types.NewParam(token.NoPos, nil, "", p.VoidPtr().raw.Type)
+		params := types.NewTuple(i8Ptr, i8Ptr, i8Ptr)
+		p.coAwaitSuspendHandleTy = types.NewSignatureType(nil, nil, nil, params, nil, false)
+	}
+	return p.coAwaitSuspendHandleTy
+}
+*/
+
+// -----------------------------------------------------------------------------
+
+func (b Builder) SetBlockOffset(offset int) {
+	b.blkOffset = offset
+}
+
+func (b Builder) BlockOffset() int {
+	return b.blkOffset
+}
+
+func (b Builder) Async() bool {
+	return b.async
+}
+
+func (b Builder) AsyncToken() Expr {
+	return b.asyncToken
+}
+
+func (b Builder) EndAsync() {
+	b.onReturn()
+}
+
+/*
+	pesudo code:
+
+retPtr := malloc(sizeof(Promise))
+id := @llvm.coro.id(0, null, null, null)
+promiseSize := sizeof(Promise[T])
+frameSize := @llvm.coro.size.i64()
+allocSize := promiseSize + frameSize
+promise := malloc(allocSize)
+needAlloc := @llvm.coro.alloc(id)
+; Allocate memory for return type and coroutine frame
+frame := null
+
+	if needAlloc {
+		frame := malloc(frameSize)
+	}
+
+hdl := @llvm.coro.begin(id, frame)
+*retPtr = hdl
+*/
+func (b Builder) BeginAsync(fn Function, entryBlk, allocBlk, cleanBlk, suspdBlk, trapBlk, beginBlk BasicBlock) {
+	ty := fn.Type.RawType().(*types.Signature).Results().At(0).Type()
+	ptrTy, ok := ty.(*types.Pointer)
+	if !ok {
+		panic("async function must return a *async.Promise")
+	}
+	promiseTy := b.Prog.Type(ptrTy.Elem(), InGo)
+
+	b.async = true
+
+	b.SetBlock(entryBlk)
+	align := b.Const(constant.MakeInt64(0), b.Prog.CInt()).SetName("align")
+	null := b.Const(nil, b.Prog.CIntPtr())
+	id := b.CoID(align, null, null, null).SetName("id")
+	b.asyncToken = id
+	promiseSize := b.Const(constant.MakeUint64(b.Prog.SizeOf(promiseTy)), b.Prog.Int64()).SetName("alloc.size")
+	frameSize := b.CoSizeI64().SetName("frame.size")
+	allocSize := b.BinOp(token.ADD, promiseSize, frameSize).SetName("alloc.size")
+	promise := b.AllocZ(allocSize).SetName("promise")
+	b.promise = promise
+	promise.Type = b.Prog.Pointer(promiseTy)
+	needAlloc := b.CoAlloc(id).SetName("need.dyn.alloc")
+	b.If(needAlloc, allocBlk, beginBlk)
+
+	b.SetBlock(allocBlk)
+	frame := b.OffsetPtr(promise, promiseSize)
+	b.Jump(beginBlk)
+
+	b.SetBlock(beginBlk)
+	phi := b.Phi(b.Prog.VoidPtr())
+	phi.SetName("frame")
+	phi.AddIncoming(b, []BasicBlock{entryBlk, allocBlk}, func(i int, blk BasicBlock) Expr {
+		if i == 0 {
+			return null
+		}
+		return frame
+	})
+	hdl := b.CoBegin(id, phi.Expr)
+	hdl.SetName("hdl")
+	b.Store(promise, hdl)
+
+	b.SetBlock(cleanBlk)
+	b.CoFree(id, hdl)
+	b.Jump(suspdBlk)
+
+	b.SetBlock(suspdBlk)
+	b.CoEnd(hdl, b.Prog.BoolVal(false), b.Prog.TokenNone())
+	b.Return(promise)
+
+	b.SetBlock(trapBlk)
+	b.LLVMTrap()
+	b.Unreachable()
+
+	b.onSuspBlk = func(nextBlk BasicBlock) (BasicBlock, BasicBlock, BasicBlock) {
+		if nextBlk == nil {
+			nextBlk = trapBlk
+		}
+		return suspdBlk, nextBlk, cleanBlk
+	}
+	b.onReturn = func() {
+		b.CoSuspend(b.asyncToken, b.Prog.BoolVal(true), trapBlk)
+	}
+}
+
+// -----------------------------------------------------------------------------
+
+// declare void @llvm.coro.destroy(ptr <handle>)
+func (b Builder) CoDestroy(hdl Expr) {
+	fn := b.Pkg.cFunc("llvm.coro.destroy", b.Prog.tyCoDestroy())
+	b.Call(fn, hdl)
+}
+
+// declare void @llvm.coro.resume(ptr <handle>)
+func (b Builder) CoResume(hdl Expr) {
+	fn := b.Pkg.cFunc("llvm.coro.resume", b.Prog.tyCoResume())
+	b.Call(fn, hdl)
+}
+
+// declare i1 @llvm.coro.done(ptr <handle>)
+func (b Builder) coDone(hdl Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.done", b.Prog.tyCoDone())
+	return b.Call(fn, hdl)
+}
+
+// return c.Char
+func (b Builder) CoDone(hdl Expr) Expr {
+	bvar := b.coDone(hdl)
+	// TODO(lijie): inefficient
+	// %6 = zext i1 %5 to i64
+	// %7 = trunc i64 %6 to i8
+	return b.valFromData(b.Prog.Byte(), bvar.impl)
+}
+
+// declare ptr @llvm.coro.promise(ptr <ptr>, i32 <alignment>, i1 <from>)
+func (b Builder) CoPromise(ptr, align, from Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.promise", b.Prog.tyCoPromise())
+	return b.Call(fn, ptr, align, from)
+}
+
+// declare i32 @llvm.coro.size.i32()
+func (b Builder) CoSizeI32() Expr {
+	fn := b.Pkg.cFunc("llvm.coro.size.i32", b.Prog.tyCoSizeI32())
+	return b.Call(fn)
+}
+
+// declare i64 @llvm.coro.size.i64()
+func (b Builder) CoSizeI64() Expr {
+	fn := b.Pkg.cFunc("llvm.coro.size.i64", b.Prog.tyCoSizeI64())
+	return b.Call(fn)
+}
+
+// declare i32 @llvm.coro.align.i32()
+func (b Builder) CoAlignI32() Expr {
+	fn := b.Pkg.cFunc("llvm.coro.align.i32", b.Prog.tyCoAlignI32())
+	return b.Call(fn)
+}
+
+// declare i64 @llvm.coro.align.i64()
+func (b Builder) CoAlignI64() Expr {
+	fn := b.Pkg.cFunc("llvm.coro.align.i64", b.Prog.tyCoAlignI64())
+	return b.Call(fn)
+}
+
+// declare ptr @llvm.coro.begin(token <id>, ptr <mem>)
+func (b Builder) CoBegin(id, mem Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.begin", b.Prog.tyCoBegin())
+	return b.Call(fn, id, mem)
+}
+
+// declare ptr @llvm.coro.free(token %id, ptr <frame>)
+func (b Builder) CoFree(id, frame Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.free", b.Prog.tyCoFree())
+	return b.Call(fn, id, frame)
+}
+
+// declare i1 @llvm.coro.alloc(token <id>)
+func (b Builder) CoAlloc(id Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.alloc", b.Prog.tyCoAlloc())
+	return b.Call(fn, id)
+}
+
+// declare ptr @llvm.coro.noop()
+func (b Builder) CoNoop() Expr {
+	fn := b.Pkg.cFunc("llvm.coro.noop", b.Prog.tyCoNoop())
+	return b.Call(fn)
+}
+
+// declare ptr @llvm.coro.frame()
+func (b Builder) CoFrame() Expr {
+	fn := b.Pkg.cFunc("llvm.coro.frame", b.Prog.tyCoFrame())
+	return b.Call(fn)
+}
+
+// declare token @llvm.coro.id(i32 <align>, ptr <promise>, ptr <coroaddr>, ptr <fnaddrs>)
+func (b Builder) CoID(align Expr, promise, coroAddr, fnAddrs Expr) Expr {
+	if align.Type != b.Prog.Int32() {
+		panic("align must be i32")
+	}
+	fn := b.Pkg.cFunc("llvm.coro.id", b.Prog.tyCoID())
+	return b.Call(fn, align, promise, coroAddr, fnAddrs)
+}
+
+/*
+// declare token @llvm.coro.id.async(i32 <context size>, i32 <align>, ptr <context arg>, ptr <async function pointer>)
+func (b Builder) CoIDAsync(contextSize, align, contextArg, asyncFnPtr Expr) Expr {
+	if contextSize.Type != b.Prog.Int32() {
+		panic("contextSize must be i32")
+	}
+	if align.Type != b.Prog.Int32() {
+		panic("align must be i32")
+	}
+	fn := b.Pkg.cFunc("llvm.coro.id.async", b.Prog.tyCoIDAsync())
+	return b.Call(fn, contextSize, align, contextArg, asyncFnPtr)
+}
+
+// declare token @llvm.coro.id.retcon(i32 <size>, i32 <align>, ptr <buffer>, ptr <continuation prototype>, ptr <alloc>, ptr <dealloc>)
+func (b Builder) CoIDRetcon(size, align, buffer, contProto, alloc, dealloc Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.id.retcon", b.Prog.tyCoIDRetcon())
+	return b.Call(fn, size, align, buffer, contProto, alloc, dealloc)
+}
+
+// declare token @llvm.coro.id.retcon.once(i32 <size>, i32 <align>, ptr <buffer>, ptr <prototype>, ptr <alloc>, ptr <dealloc>)
+func (b Builder) CoIDRetconOnce(size, align, buffer, prototype, alloc, dealloc Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.id.retcon.once", b.Prog.tyCoIDRetconOnce())
+	return b.Call(fn, size, align, buffer, prototype, alloc, dealloc)
+}
+*/
+
+// declare i1 @llvm.coro.end(ptr <handle>, i1 <unwind>, token <result.token>)
+func (b Builder) CoEnd(hdl Expr, unwind Expr, resultToken Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.end", b.Prog.tyCoEnd())
+	return b.Call(fn, hdl, unwind, resultToken)
+}
+
+/*
+// declare token @llvm.coro.end.results(...)
+func (b Builder) CoEndResults(args []Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.end.results", b.Prog.tyCoEndResults())
+	return b.Call(fn, args...)
+}
+
+// declare i1 @llvm.coro.end.async(ptr <handle>, i1 <unwind>, ...)
+func (b Builder) CoEndAsync(handle, unwind Expr, args ...Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.end.async", b.Prog.tyCoEndAsync())
+	vargs := append([]Expr{handle, unwind}, args...)
+	return b.Call(fn, vargs...)
+}
+*/
+
+// declare i8 @llvm.coro.suspend(token <save>, i1 <final>)
+func (b Builder) coSuspend(save, final Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.suspend", b.Prog.tyCoSuspend())
+	return b.Call(fn, save, final)
+}
+
+func (b Builder) CoSuspend(save, final Expr, nextBlk BasicBlock) {
+	if !b.async {
+		panic(fmt.Errorf("suspend %v not in async block", b.Func.Name()))
+	}
+	if nextBlk == nil {
+		b.Func.MakeBlock("")
+		nextBlk = b.Func.Block(b.blk.idx + 1)
+	}
+	ret := b.coSuspend(save, final)
+	susp, next, clean := b.onSuspBlk(nextBlk)
+	swt := b.Switch(ret, susp)
+	swt.Case(b.Const(constant.MakeInt64(0), b.Prog.Byte()), next)
+	swt.Case(b.Const(constant.MakeInt64(1), b.Prog.Byte()), clean)
+	swt.End(b)
+	b.SetBlock(nextBlk)
+}
+
+func (b Builder) CoReturn(setValueFn Function, value Expr) {
+	if !b.async {
+		panic(fmt.Errorf("return %v not in async block", b.Func.Name()))
+	}
+	b.Call(setValueFn.Expr, b.promise, value)
+	_, _, cleanBlk := b.onSuspBlk(nil)
+	b.Jump(cleanBlk)
+}
+
+func (b Builder) CoYield(setValueFn Function, value Expr, final Expr) {
+	if !b.async {
+		panic(fmt.Errorf("yield %v not in async block", b.Func.Name()))
+	}
+	b.Call(setValueFn.Expr, b.promise, value)
+	b.CoSuspend(b.AsyncToken(), final, nil)
+}
+
+/*
+// declare token @llvm.coro.save(ptr <handle>)
+func (b Builder) CoSave(hdl Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.save", b.Prog.tyCoSave())
+	return b.Call(fn, hdl)
+}
+
+// declare ptr @llvm.coro.prepare.async(ptr <coroutine function>)
+func (b Builder) CoPrepareAsync(f Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.prepare.async", b.Prog.tyCoPrepareAsync())
+	return b.Call(fn, f)
+}
+
+// declare i1 @llvm.coro.suspend.retcon(...)
+func (b Builder) CoSuspendRetcon(args []Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.suspend.retcon", b.Prog.tyCoSuspendRetcon())
+	return b.Call(fn, args...)
+}
+
+// declare void @llvm.coro.await.suspend.void(ptr <awaiter>, ptr <handle>, ptr <await_suspend_function>)
+func (b Builder) CoAwaitSuspendVoid(awaiter, handle, f Expr) {
+	fn := b.Pkg.cFunc("llvm.coro.await.suspend.void", b.Prog.tyCoAwaitSuspendVoid())
+	b.Call(fn, awaiter, handle, f)
+}
+
+// declare i1 @llvm.coro.await.suspend.bool(ptr <awaiter>, ptr <handle>, ptr <await_suspend_function>)
+func (b Builder) CoAwaitSuspendBool(awaiter, handle, f Expr) Expr {
+	fn := b.Pkg.cFunc("llvm.coro.await.suspend.bool", b.Prog.tyCoAwaitSuspendBool())
+	return b.Call(fn, awaiter, handle, f)
+}
+
+// declare void @llvm.coro.await.suspend.handle(ptr <awaiter>, ptr <handle>, ptr <await_suspend_function>)
+func (b Builder) CoAwaitSuspendHandle(awaiter, handle, f Expr) {
+	fn := b.Pkg.cFunc("llvm.coro.await.suspend.handle", b.Prog.tyCoAwaitSuspendHandle())
+	b.Call(fn, awaiter, handle, f)
+}
+*/
--- a/ssa/decl.go
+++ b/ssa/decl.go
@@ -180,11 +180,11 @@ type Function = *aFunction

 // NewFunc creates a new function.
 func (p Package) NewFunc(name string, sig *types.Signature, bg Background) Function {
-	return p.NewFuncEx(name, sig, bg, false)
+	return p.NewFuncEx(name, sig, bg, false, false)
 }

 // NewFuncEx creates a new function.
-func (p Package) NewFuncEx(name string, sig *types.Signature, bg Background, hasFreeVars bool) Function {
+func (p Package) NewFuncEx(name string, sig *types.Signature, bg Background, hasFreeVars, async bool) Function {
 	if v, ok := p.fns[name]; ok {
 		return v
 	}
@@ -193,6 +193,9 @@ func (p Package) NewFuncEx(name string, sig *types.Signature, bg Background, has
 		log.Println("NewFunc", name, t.raw.Type, "hasFreeVars:", hasFreeVars)
 	}
 	fn := llvm.AddFunction(p.mod, name, t.ll)
+	if async {
+		fn.AddFunctionAttr(p.Prog.ctx.CreateStringAttribute("presplitcoroutine", ""))
+	}
 	ret := newFunction(fn, t, p, p.Prog, hasFreeVars)
 	p.fns[name] = ret
 	return ret
@@ -268,7 +271,7 @@ func (p Function) NewBuilder() Builder {
 	b := prog.ctx.NewBuilder()
 	// TODO(xsw): Finalize may cause panic, so comment it.
 	// b.Finalize()
-	return &aBuilder{b, nil, p, p.Pkg, prog}
+	return &aBuilder{impl: b, blk: nil, Func: p, Pkg: p.Pkg, Prog: prog}
 }

 // HasBody reports whether the function has a body.
@@ -293,13 +296,15 @@ func (p Function) MakeBlocks(nblk int) []BasicBlock {
 		p.blks = make([]BasicBlock, 0, nblk)
 	}
 	for i := 0; i < nblk; i++ {
-		p.addBlock(n + i)
+		p.addBlock(n+i, "")
 	}
 	return p.blks[n:]
 }

-func (p Function) addBlock(idx int) BasicBlock {
-	label := "_llgo_" + strconv.Itoa(idx)
+func (p Function) addBlock(idx int, label string) BasicBlock {
+	if label == "" {
+		label = "_llgo_" + strconv.Itoa(idx)
+	}
 	blk := llvm.AddBasicBlock(p.impl, label)
 	ret := &aBasicBlock{blk, blk, p, idx}
 	p.blks = append(p.blks, ret)
@@ -307,8 +312,8 @@ func (p Function) addBlock(idx int) BasicBlock {
 }

 // MakeBlock creates a new basic block for the function.
-func (p Function) MakeBlock() BasicBlock {
-	return p.addBlock(len(p.blks))
+func (p Function) MakeBlock(label string) BasicBlock {
+	return p.addBlock(len(p.blks), label)
 }

 // Block returns the ith basic block of the function.
--- a/ssa/eh.go
+++ b/ssa/eh.go
@@ -55,6 +55,13 @@ func (p Program) tySiglongjmp() *types.Signature {
 	return p.sigljmpTy
 }

+func (p Program) tyLLVMTrap() *types.Signature {
+	if p.llvmTrapTy == nil {
+		p.llvmTrapTy = types.NewSignatureType(nil, nil, nil, nil, nil, false)
+	}
+	return p.llvmTrapTy
+}
+
 func (b Builder) AllocaSigjmpBuf() Expr {
 	prog := b.Prog
 	n := unsafe.Sizeof(sigjmpbuf{})
@@ -77,6 +84,11 @@ func (b Builder) Siglongjmp(jb, retval Expr) {
 	// b.Unreachable()
 }

+func (b Builder) LLVMTrap() {
+	fn := b.Pkg.cFunc("llvm.trap", b.Prog.tyLLVMTrap())
+	b.Call(fn)
+}
+
 // -----------------------------------------------------------------------------

 const (
@@ -166,7 +178,7 @@ func (b Builder) getDefer(kind DoAction) *aDefer {
 		czero := prog.IntVal(0, prog.CInt())
 		retval := b.Sigsetjmp(jb, czero)
 		if kind != DeferAlways {
-			panicBlk = self.MakeBlock()
+			panicBlk = self.MakeBlock("")
 		} else {
 			blks = self.MakeBlocks(2)
 			next, panicBlk = blks[0], blks[1]
@@ -240,7 +252,7 @@ func (b Builder) Defer(kind DoAction, fn Expr, args ...Expr) {
 // RunDefers emits instructions to run deferred instructions.
 func (b Builder) RunDefers() {
 	self := b.getDefer(DeferInCond)
-	blk := b.Func.MakeBlock()
+	blk := b.Func.MakeBlock("")
 	self.rundsNext = append(self.rundsNext, blk)

 	b.Store(self.rundPtr, blk.Addr())
--- a/ssa/expr.go
+++ b/ssa/expr.go
@@ -59,6 +59,11 @@ func (v Expr) SetOrdering(ordering AtomicOrdering) Expr {
 	return v
 }

+func (v Expr) SetName(name string) Expr {
+	v.impl.SetName(name)
+	return v
+}
+
 // -----------------------------------------------------------------------------

 type builtinTy struct {
--- a/ssa/memory.go
+++ b/ssa/memory.go
@@ -232,6 +232,13 @@ func (b Builder) ArrayAlloca(telem Type, n Expr) (ret Expr) {
 	return
 }

+func (b Builder) OffsetPtr(ptr, offset Expr) Expr {
+	if debugInstr {
+		log.Printf("OffsetPtr %v, %v\n", ptr.impl, offset.impl)
+	}
+	return Expr{llvm.CreateGEP(b.impl, ptr.Type.ll, ptr.impl, []llvm.Value{offset.impl}), ptr.Type}
+}
+
 /* TODO(xsw):
 // ArrayAlloc allocates zero initialized space for an array of n elements of type telem.
 func (b Builder) ArrayAlloc(telem Type, n Expr) (ret Expr) {
--- a/ssa/package.go
+++ b/ssa/package.go
@@ -19,8 +19,10 @@ package ssa
 import (
 	"go/token"
 	"go/types"
+	"regexp"
 	"runtime"
 	"strconv"
+	"strings"
 	"unsafe"

 	"github.com/goplus/llgo/ssa/abi"
@@ -136,6 +138,8 @@ type aProgram struct {
 	rtMapTy    llvm.Type
 	rtChanTy   llvm.Type

+	tokenType llvm.Type
+
 	anyTy     Type
 	voidTy    Type
 	voidPtr   Type
@@ -166,6 +170,8 @@ type aProgram struct {
 	deferTy   Type
 	deferPtr  Type

+	tokenTy Type
+
 	pyImpTy      *types.Signature
 	pyNewList    *types.Signature
 	pyListSetI   *types.Signature
@@ -189,6 +195,41 @@ type aProgram struct {
 	sigsetjmpTy *types.Signature
 	sigljmpTy   *types.Signature

+	llvmTrapTy *types.Signature
+
+	// coroutine manipulation intrinsics (ordered by LLVM coroutine doc)
+	coDestroyTy *types.Signature
+	coResumeTy  *types.Signature
+	coDoneTy    *types.Signature
+	coPromiseTy *types.Signature
+
+	// coroutine structure intrinsics (ordered by LLVM coroutine doc)
+	coSizeI32Ty  *types.Signature
+	coSizeI64Ty  *types.Signature
+	coAlignI32Ty *types.Signature
+	coAlignI64Ty *types.Signature
+	coBeginTy    *types.Signature
+	coFreeTy     *types.Signature
+	coAllocTy    *types.Signature
+	coNoopTy     *types.Signature
+	coFrameTy    *types.Signature
+	coIDTy       *types.Signature
+	// coIDAsyncTy              *types.Signature
+	// coIDRetconTy             *types.Signature
+	// coIDRetconOnceTy         *types.Signature
+	coEndTy *types.Signature
+	// coEndResultsTy           *types.Signature
+	// coEndAsyncTy             *types.Signature
+	coSuspendTy *types.Signature
+	// coSaveTy                 *types.Signature
+	// coSuspendAsyncTy         *types.Signature
+	// coPrepareAsyncTy         *types.Signature
+	// coSuspendRetconTy        *types.Signature
+	// coAwaitSuspendFunctionTy *types.Signature
+	// coAwaitSuspendVoidTy     *types.Signature
+	// coAwaitSuspendBoolTy     *types.Signature
+	// coAwaitSuspendHandleTy   *types.Signature
+
 	paramObjPtr_ *types.Var

 	ptrSize int
@@ -441,6 +482,18 @@ func (p Program) Any() Type {
 	return p.anyTy
 }

+func (p Program) Token() Type {
+	if p.tokenTy == nil {
+		p.tokenTy = &aType{p.tyToken(), rawType{types.Typ[types.Invalid]}, vkInvalid}
+	}
+	return p.tokenTy
+}
+
+func (p Program) TokenNone() Expr {
+	impl := llvm.ConstNull(p.Token().ll)
+	return Expr{impl: impl, Type: p.Token()}
+}
+
 /*
 // Eface returns the empty interface type.
 // It is equivalent to Any.
@@ -649,9 +702,41 @@ func (p Package) Path() string {
 	return p.abi.Pkg
 }

+// Find presplitcoroutine attribute and replace attribute tag with it
+// e.g. attributes #0 = { noinline nounwind readnone "presplitcoroutine" }
+// replace #0 with presplitcoroutine
+// and also remove all other attributes
+func removeLLVMAttributes(ll string) string {
+	attrRe := regexp.MustCompile(`^attributes (#\d+) = {[^}]*}$`)
+	attrRe2 := regexp.MustCompile(`(\) #\d+ {|\) #\d+)$`)
+	lines := strings.Split(ll, "\n")
+	newLines := make([]string, 0, len(lines))
+	presplitcoroutine := ""
+	for _, line := range lines {
+		if m := attrRe.FindStringSubmatch(line); m != nil {
+			if strings.Contains(line, "\"presplitcoroutine\"") {
+				presplitcoroutine = " " + m[1] + " "
+			}
+		} else {
+			newLines = append(newLines, line)
+		}
+	}
+
+	for i, line := range newLines {
+		if presplitcoroutine != "" {
+			line = strings.Replace(line, presplitcoroutine, " presplitcoroutine ", 1)
+		}
+		line = attrRe2.ReplaceAllString(line, ")")
+		newLines[i] = line
+	}
+
+	return strings.Join(newLines, "\n")
+}
+
 // String returns a string representation of the package.
 func (p Package) String() string {
-	return p.mod.String()
+	// TODO(lijie): workaround for compiling errors of LLVM attributes
+	return removeLLVMAttributes(p.mod.String())
 }

 // SetPatch sets a patch function.
--- a/ssa/ssa_test.go
+++ b/ssa/ssa_test.go
@@ -469,6 +469,47 @@ _llgo_0:
 `)
 }

+func TestSwitch(t *testing.T) {
+	prog := NewProgram(nil)
+	pkg := prog.NewPackage("bar", "foo/bar")
+	params := types.NewTuple(types.NewVar(0, nil, "a", types.Typ[types.Int]))
+	rets := types.NewTuple(types.NewVar(0, nil, "", types.Typ[types.Int]))
+	sig := types.NewSignatureType(nil, nil, nil, params, rets, false)
+	fn := pkg.NewFunc("fn", sig, InGo)
+	b := fn.MakeBody(4)
+	cond := fn.Param(0)
+	case1 := fn.Block(1)
+	case2 := fn.Block(2)
+	defb := fn.Block(3)
+	swc := b.Switch(cond, defb)
+	swc.Case(prog.Val(1), case1)
+	swc.Case(prog.Val(2), case2)
+	swc.End(b)
+	b.SetBlock(case1).Return(prog.Val(3))
+	b.SetBlock(case2).Return(prog.Val(4))
+	b.SetBlock(defb).Return(prog.Val(5))
+	assertPkg(t, pkg, `; ModuleID = 'foo/bar'
+source_filename = "foo/bar"
+
+define i64 @fn(i64 %0) {
+_llgo_0:
+  switch i64 %0, label %_llgo_3 [
+    i64 1, label %_llgo_1
+    i64 2, label %_llgo_2
+  ]
+
+_llgo_1:                                          ; preds = %_llgo_0
+  ret i64 3
+
+_llgo_2:                                          ; preds = %_llgo_0
+  ret i64 4
+
+_llgo_3:                                          ; preds = %_llgo_0
+  ret i64 5
+}
+`)
+}
+
 func TestUnOp(t *testing.T) {
 	prog := NewProgram(nil)
 	pkg := prog.NewPackage("bar", "foo/bar")
@@ -552,3 +593,194 @@ _llgo_0:
 }
 `)
 }
+
+func TestPointerOffset(t *testing.T) {
+	prog := NewProgram(nil)
+	pkg := prog.NewPackage("bar", "foo/bar")
+	params := types.NewTuple(
+		types.NewVar(0, nil, "p", types.NewPointer(types.Typ[types.Int])),
+		types.NewVar(0, nil, "offset", types.Typ[types.Int]),
+	)
+	rets := types.NewTuple(types.NewVar(0, nil, "", types.NewPointer(types.Typ[types.Int])))
+	sig := types.NewSignatureType(nil, nil, nil, params, rets, false)
+	fn := pkg.NewFunc("fn", sig, InGo)
+	b := fn.MakeBody(1)
+	ptr := fn.Param(0)
+	offset := fn.Param(1)
+	result := b.OffsetPtr(ptr, offset)
+	b.Return(result)
+	assertPkg(t, pkg, `; ModuleID = 'foo/bar'
+source_filename = "foo/bar"
+
+define ptr @fn(ptr %0, i64 %1) {
+_llgo_0:
+  %2 = getelementptr ptr, ptr %0, i64 %1
+  ret ptr %2
+}
+`)
+}
+
+func TestLLVMTrap(t *testing.T) {
+	prog := NewProgram(nil)
+	pkg := prog.NewPackage("bar", "foo/bar")
+	b := pkg.NewFunc("fn", NoArgsNoRet, InGo).MakeBody(1)
+	b.LLVMTrap()
+	b.Unreachable()
+	assertPkg(t, pkg, `; ModuleID = 'foo/bar'
+source_filename = "foo/bar"
+
+define void @fn() {
+_llgo_0:
+  call void @llvm.trap()
+  unreachable
+}
+
+; Function Attrs: cold noreturn nounwind memory(inaccessiblemem: write)
+declare void @llvm.trap()
+
+`)
+}
+
+func TestCoroFuncs(t *testing.T) {
+	prog := NewProgram(nil)
+	pkg := prog.NewPackage("bar", "foo/bar")
+	fn := pkg.NewFunc("fn", NoArgsNoRet, InGo)
+	entryBlk := fn.MakeBlock("entry")
+	suspdBlk := fn.MakeBlock("suspend")
+	cleanBlk := fn.MakeBlock("clean")
+	b := fn.NewBuilder()
+	b.async = true
+
+	b.SetBlock(entryBlk)
+	align := b.Const(constant.MakeInt64(0), prog.Int32())
+	align8 := b.Const(constant.MakeInt64(8), prog.Int32())
+	null := b.Const(nil, b.Prog.CIntPtr())
+	b.promise = null
+	id := b.CoID(align, null, null, null)
+	bf := b.Const(constant.MakeBool(false), prog.Bool())
+	b.CoSizeI32()
+	size := b.CoSizeI64()
+	b.CoAlignI32()
+	b.CoAlignI64()
+	b.CoAlloc(id)
+	frame := b.Alloca(size)
+	hdl := b.CoBegin(id, frame)
+
+	b.SetBlock(cleanBlk)
+	b.CoFree(id, frame)
+	b.Jump(suspdBlk)
+
+	b.SetBlock(suspdBlk)
+	b.CoEnd(hdl, bf, prog.TokenNone())
+	// b.Return(b.promise)
+
+	b.SetBlock(entryBlk)
+
+	b.CoResume(hdl)
+	b.CoDone(hdl)
+	b.CoDestroy(hdl)
+
+	b.CoPromise(null, align8, bf)
+	b.CoNoop()
+	b.CoFrame()
+	setArgs := types.NewTuple(types.NewVar(0, nil, "value", types.Typ[types.Int]))
+	setSig := types.NewSignatureType(nil, nil, nil, setArgs, nil, false)
+	setFn := pkg.NewFunc("setValue", setSig, InGo)
+	one := b.Const(constant.MakeInt64(1), prog.Int())
+
+	b.onSuspBlk = func(next BasicBlock) (BasicBlock, BasicBlock, BasicBlock) {
+		return suspdBlk, next, cleanBlk
+	}
+	b.CoYield(setFn, one, bf)
+	b.CoReturn(setFn, one)
+
+	assertPkg(t, pkg, `; ModuleID = 'foo/bar'
+source_filename = "foo/bar"
+
+define void @fn() {
+entry:
+  %0 = call token @llvm.coro.id(i32 0, ptr null, ptr null, ptr null)
+  %1 = call i32 @llvm.coro.size.i32()
+  %2 = call i64 @llvm.coro.size.i64()
+  %3 = call i32 @llvm.coro.align.i32()
+  %4 = call i64 @llvm.coro.align.i64()
+  %5 = call i1 @llvm.coro.alloc(token %0)
+  %6 = alloca i8, i64 %2, align 1
+  %7 = call ptr @llvm.coro.begin(token %0, ptr %6)
+  call void @llvm.coro.resume(ptr %7)
+  %8 = call i1 @llvm.coro.done(ptr %7)
+  %9 = zext i1 %8 to i64
+  %10 = trunc i64 %9 to i8
+  call void @llvm.coro.destroy(ptr %7)
+  %11 = call ptr @llvm.coro.promise(ptr null, i32 8, i1 false)
+  %12 = call ptr @llvm.coro.noop()
+  %13 = call ptr @llvm.coro.frame()
+  call void @setValue(ptr null, i64 1)
+  %14 = call i8 @llvm.coro.suspend(<null operand!>, i1 false)
+  switch i8 %14, label %suspend [
+    i8 0, label %suspend
+    i8 1, label %clean
+  ]
+
+suspend:                                          ; preds = %entry, %entry, %clean
+  %15 = call i1 @llvm.coro.end(ptr %7, i1 false, token none)
+  call void @setValue(ptr null, i64 1)
+  br label %clean
+
+clean:                                            ; preds = %suspend, %entry
+  %16 = call ptr @llvm.coro.free(token %0, ptr %6)
+  br label %suspend
+
+_llgo_3:                                          ; No predecessors!
+}
+
+; Function Attrs: nocallback nofree nosync nounwind willreturn memory(argmem: read)
+declare token @llvm.coro.id(i32, ptr readnone, ptr nocapture readonly, ptr)
+
+; Function Attrs: nounwind memory(none)
+declare i32 @llvm.coro.size.i32()
+
+; Function Attrs: nounwind memory(none)
+declare i64 @llvm.coro.size.i64()
+
+; Function Attrs: nounwind memory(none)
+declare i32 @llvm.coro.align.i32()
+
+; Function Attrs: nounwind memory(none)
+declare i64 @llvm.coro.align.i64()
+
+; Function Attrs: nounwind
+declare i1 @llvm.coro.alloc(token)
+
+; Function Attrs: nounwind
+declare ptr @llvm.coro.begin(token, ptr writeonly)
+
+; Function Attrs: nounwind memory(argmem: read)
+declare ptr @llvm.coro.free(token, ptr nocapture readonly)
+
+; Function Attrs: nounwind
+declare i1 @llvm.coro.end(ptr, i1, token)
+
+declare void @llvm.coro.resume(ptr)
+
+; Function Attrs: nounwind memory(argmem: readwrite)
+declare i1 @llvm.coro.done(ptr nocapture readonly)
+
+declare void @llvm.coro.destroy(ptr)
+
+; Function Attrs: nounwind memory(none)
+declare ptr @llvm.coro.promise(ptr nocapture, i32, i1)
+
+; Function Attrs: nounwind memory(none)
+declare ptr @llvm.coro.noop()
+
+; Function Attrs: nounwind memory(none)
+declare ptr @llvm.coro.frame()
+
+declare void @setValue(i64)
+
+; Function Attrs: nounwind
+declare i8 @llvm.coro.suspend(token, i1)
+
+`)
+}
--- a/ssa/stmt_builder.go
+++ b/ssa/stmt_builder.go
@@ -63,6 +63,13 @@ type aBuilder struct {
 	Func Function
 	Pkg  Package
 	Prog Program
+
+	async      bool
+	asyncToken Expr
+	promise    Expr
+	onSuspBlk  func(blk BasicBlock) (susp BasicBlock, next BasicBlock, clean BasicBlock)
+	onReturn   func()
+	blkOffset  int
 }

 // Builder represents a builder for creating instructions in a function.
@@ -94,7 +101,7 @@ func (b Builder) setBlockMoveLast(blk BasicBlock) (next BasicBlock) {

 	impl := b.impl

-	next = b.Func.MakeBlock()
+	next = b.Func.MakeBlock("")
 	impl.SetInsertPointAtEnd(next.last)
 	impl.Insert(last)

@@ -288,7 +295,7 @@ func (b Builder) Times(n Expr, loop func(i Expr)) {
 }

 // -----------------------------------------------------------------------------
-/*
+
 type caseStmt struct {
 	v   llvm.Value
 	blk llvm.BasicBlock
@@ -326,7 +333,7 @@ func (b Builder) Switch(v Expr, defb BasicBlock) Switch {
 	}
 	return &aSwitch{v.impl, defb.first, nil}
 }
-*/
+
 // -----------------------------------------------------------------------------

 // Phi represents a phi node.
--- a/ssa/type.go
+++ b/ssa/type.go
@@ -58,6 +58,7 @@ const (
 	vkIface
 	vkStruct
 	vkChan
+	vkToken
 )

 // -----------------------------------------------------------------------------
@@ -282,6 +283,13 @@ func (p Program) tyInt() llvm.Type {
 	return p.intType
 }

+func (p Program) tyToken() llvm.Type {
+	if p.tokenType.IsNil() {
+		p.tokenType = p.ctx.TokenType()
+	}
+	return p.tokenType
+}
+
 func llvmIntType(ctx llvm.Context, size int) llvm.Type {
 	if size <= 4 {
 		return ctx.Int32Type()
@@ -362,6 +370,9 @@ func (p Program) toType(raw types.Type) Type {
 			return &aType{p.rtString(), typ, vkString}
 		case types.UnsafePointer:
 			return &aType{p.tyVoidPtr(), typ, vkPtr}
+		// TODO(lijie): temporary solution, should be replaced by a proper type
+		case types.Invalid:
+			return &aType{p.tyToken(), typ, vkInvalid}
 		}
 	case *types.Pointer:
 		elem := p.rawType(t.Elem())
@@ -444,7 +455,8 @@ func (p Program) toLLVMTypes(t *types.Tuple, n int) (ret []llvm.Type) {
 	if n > 0 {
 		ret = make([]llvm.Type, n)
 		for i := 0; i < n; i++ {
-			ret[i] = p.rawType(t.At(i).Type()).ll
+			pt := t.At(i)
+			ret[i] = p.rawType(pt.Type()).ll
 		}
 	}
 	return