package main

import (
	"errors"
	"flag"
	"fmt"
	"go/build"
	"go/constant"
	"go/token"
	"go/types"
	"os"
	"sort"
	"strings"

	"github.com/aykevl/llvm/bindings/go/llvm"
	"golang.org/x/tools/go/loader"
	"golang.org/x/tools/go/ssa"
	"golang.org/x/tools/go/ssa/ssautil"
)

func init() {
	llvm.InitializeAllTargets()
	llvm.InitializeAllTargetMCs()
	llvm.InitializeAllTargetInfos()
	llvm.InitializeAllAsmParsers()
	llvm.InitializeAllAsmPrinters()
}

type Compiler struct {
	triple          string
	mod             llvm.Module
	ctx             llvm.Context
	builder         llvm.Builder
	machine         llvm.TargetMachine
	targetData      llvm.TargetData
	intType         llvm.Type
	i8ptrType       llvm.Type // for convenience
	uintptrType     llvm.Type
	stringLenType   llvm.Type
	stringType      llvm.Type
	interfaceType   llvm.Type
	typeassertType  llvm.Type
	taskDataType    llvm.Type
	allocFunc       llvm.Value
	freeFunc        llvm.Value
	coroIdFunc      llvm.Value
	coroSizeFunc    llvm.Value
	coroBeginFunc   llvm.Value
	coroSuspendFunc llvm.Value
	coroEndFunc     llvm.Value
	coroFreeFunc    llvm.Value
	itfTypeNumbers  map[types.Type]uint64
	itfTypes        []types.Type
	initFuncs       []llvm.Value
	analysis        *Analysis
}

type Frame struct {
	fn           *ssa.Function
	llvmFn       llvm.Value
	params       map[*ssa.Parameter]int   // arguments to the function
	locals       map[ssa.Value]llvm.Value // local variables
	blocks       map[*ssa.BasicBlock]llvm.BasicBlock
	phis         []Phi
	blocking     bool
	taskState    llvm.Value
	taskHandle   llvm.Value
	cleanupBlock llvm.BasicBlock
	suspendBlock llvm.BasicBlock
}

func pkgPrefix(pkg *ssa.Package) string {
	if pkg.Pkg.Name() == "main" {
		return "main"
	}
	return pkg.Pkg.Path()
}

type Phi struct {
	ssa  *ssa.Phi
	llvm llvm.Value
}

func NewCompiler(pkgName, triple string) (*Compiler, error) {
	c := &Compiler{
		triple:         triple,
		itfTypeNumbers: make(map[types.Type]uint64),
		analysis:       NewAnalysis(),
	}

	target, err := llvm.GetTargetFromTriple(triple)
	if err != nil {
		return nil, err
	}
	c.machine = target.CreateTargetMachine(triple, "", "", llvm.CodeGenLevelDefault, llvm.RelocDefault, llvm.CodeModelDefault)
	c.targetData = c.machine.CreateTargetData()

	c.mod = llvm.NewModule(pkgName)
	c.ctx = c.mod.Context()
	c.builder = c.ctx.NewBuilder()

	// Depends on platform (32bit or 64bit), but fix it here for now.
	c.intType = llvm.Int32Type()
	c.stringLenType = llvm.Int32Type()
	c.uintptrType = c.targetData.IntPtrType()
	c.i8ptrType = llvm.PointerType(llvm.Int8Type(), 0)

	// Go string: tuple of (len, ptr)
	c.stringType = llvm.StructType([]llvm.Type{c.stringLenType, c.i8ptrType}, false)

	// Go interface: tuple of (type, ptr)
	c.interfaceType = llvm.StructType([]llvm.Type{llvm.Int32Type(), c.i8ptrType}, false)

	// Go typeassert result: tuple of (ptr, bool)
	c.typeassertType = llvm.StructType([]llvm.Type{c.i8ptrType, llvm.Int1Type()}, false)

	// Goroutine / task data: {i8 state, i32 data, i8* next}
	c.taskDataType = llvm.StructType([]llvm.Type{llvm.Int8Type(), llvm.Int32Type(), c.i8ptrType}, false)

	allocType := llvm.FunctionType(c.i8ptrType, []llvm.Type{c.uintptrType}, false)
	c.allocFunc = llvm.AddFunction(c.mod, "runtime.alloc", allocType)

	freeType := llvm.FunctionType(llvm.VoidType(), []llvm.Type{c.i8ptrType}, false)
	c.freeFunc = llvm.AddFunction(c.mod, "runtime.free", freeType)

	coroIdType := llvm.FunctionType(c.ctx.TokenType(), []llvm.Type{llvm.Int32Type(), c.i8ptrType, c.i8ptrType, c.i8ptrType}, false)
	c.coroIdFunc = llvm.AddFunction(c.mod, "llvm.coro.id", coroIdType)

	coroSizeType := llvm.FunctionType(llvm.Int32Type(), nil, false)
	c.coroSizeFunc = llvm.AddFunction(c.mod, "llvm.coro.size.i32", coroSizeType)

	coroBeginType := llvm.FunctionType(c.i8ptrType, []llvm.Type{c.ctx.TokenType(), c.i8ptrType}, false)
	c.coroBeginFunc = llvm.AddFunction(c.mod, "llvm.coro.begin", coroBeginType)

	coroSuspendType := llvm.FunctionType(llvm.Int8Type(), []llvm.Type{c.ctx.TokenType(), llvm.Int1Type()}, false)
	c.coroSuspendFunc = llvm.AddFunction(c.mod, "llvm.coro.suspend", coroSuspendType)

	coroEndType := llvm.FunctionType(llvm.Int1Type(), []llvm.Type{c.i8ptrType, llvm.Int1Type()}, false)
	c.coroEndFunc = llvm.AddFunction(c.mod, "llvm.coro.end", coroEndType)

	coroFreeType := llvm.FunctionType(c.i8ptrType, []llvm.Type{c.ctx.TokenType(), c.i8ptrType}, false)
	c.coroFreeFunc = llvm.AddFunction(c.mod, "llvm.coro.free", coroFreeType)

	return c, nil
}

func (c *Compiler) Parse(mainPath string, buildTags []string) error {
	tripleSplit := strings.Split(c.triple, "-")

	config := loader.Config {
		TypeChecker: types.Config{
			Sizes: &types.StdSizes{
				int64(c.targetData.PointerSize()),
				int64(c.targetData.PrefTypeAlignment(c.i8ptrType)),
			},
		},
		Build: &build.Context {
			GOARCH:      tripleSplit[0],
			GOOS:        tripleSplit[2],
			GOROOT:      ".",
			CgoEnabled:  true,
			UseAllFiles: false,
			Compiler:    "gc", // must be one of the recognized compilers
			BuildTags:   append([]string{"tgo"}, buildTags...),
		},
		AllowErrors: true,
	}
	config.Import("runtime")
	config.Import(mainPath)
	lprogram, err := config.Load()
	if err != nil {
		return err
	}

	// TODO: pick the error of the first package, not a random package
	for _, pkgInfo := range lprogram.AllPackages {
		if len(pkgInfo.Errors) != 0 {
			return pkgInfo.Errors[0]
		}
	}

	program := ssautil.CreateProgram(lprogram, ssa.SanityCheckFunctions | ssa.BareInits)
	program.Build()

	// Make a list of packages in import order.
	packageList := []*ssa.Package{}
	packageSet := map[string]struct{}{}
	worklist := []string{"runtime", mainPath}
	for len(worklist) != 0 {
		pkgPath := worklist[0]
		pkg := program.ImportedPackage(pkgPath)
		if pkg == nil {
			// Non-SSA package (e.g. cgo).
			packageSet[pkgPath] = struct{}{}
			worklist = worklist[1:]
			continue
		}
		if _, ok := packageSet[pkgPath]; ok {
			// Package already in the final package list.
			worklist = worklist[1:]
			continue
		}

		unsatisfiedImports := make([]string, 0)
		imports := pkg.Pkg.Imports()
		for _, pkg := range imports {
			if _, ok := packageSet[pkg.Path()]; ok {
				continue
			}
			unsatisfiedImports = append(unsatisfiedImports, pkg.Path())
		}
		if len(unsatisfiedImports) == 0 {
			// All dependencies of this package are satisfied, so add this
			// package to the list.
			packageList = append(packageList, pkg)
			packageSet[pkgPath] = struct{}{}
			worklist = worklist[1:]
		} else {
			// Prepend all dependencies to the worklist and reconsider this
			// package (by not removing it from the worklist). At that point, it
			// must be possible to add it to packageList.
			worklist = append(unsatisfiedImports, worklist...)
		}
	}

	for _, pkg := range packageList {
		c.analysis.AddPackage(pkg)
	}
	c.analysis.AnalyseCallgraph()         // set up callgraph
	c.analysis.AnalyseBlockingRecursive() // make all parents of blocking calls blocking (transitively)
	c.analysis.AnalyseGoCalls()           // check whether we need a scheduler

	// Transform each package into LLVM IR.
	for _, pkg := range packageList {
		err := c.parsePackage(program, pkg)
		if err != nil {
			return err
		}
	}

	// After all packages are imported, add a synthetic initializer function
	// that calls the initializer of each package.
	initFn := c.mod.NamedFunction("runtime.initAll")
	if initFn.IsNil() {
		initType := llvm.FunctionType(llvm.VoidType(), nil, false)
		initFn = llvm.AddFunction(c.mod, "runtime.initAll", initType)
	}
	initFn.SetLinkage(llvm.PrivateLinkage)
	block := c.ctx.AddBasicBlock(initFn, "entry")
	c.builder.SetInsertPointAtEnd(block)
	for _, fn := range c.initFuncs {
		c.builder.CreateCall(fn, nil, "")
	}
	c.builder.CreateRetVoid()

	// Set functions referenced in runtime.ll to internal linkage, to improve
	// optimization (hopefully).
	main := c.mod.NamedFunction("main.main")
	if !main.IsDeclaration() {
		main.SetLinkage(llvm.PrivateLinkage)
	}
	mainAsync := c.mod.NamedFunction("main.main$async")
	if !mainAsync.IsDeclaration() {
		mainAsync.SetLinkage(llvm.PrivateLinkage)
	}
	c.mod.NamedFunction("runtime.scheduler").SetLinkage(llvm.PrivateLinkage)

	if c.analysis.NeedsScheduler() {
		// Enable the scheduler.
		c.mod.NamedGlobal(".has_scheduler").SetInitializer(llvm.ConstInt(llvm.Int1Type(), 1, false))
	}

	return nil
}

func (c *Compiler) getLLVMType(goType types.Type) (llvm.Type, error) {
	switch typ := goType.(type) {
	case *types.Array:
		elemType, err := c.getLLVMType(typ.Elem())
		if err != nil {
			return llvm.Type{}, err
		}
		return llvm.ArrayType(elemType, int(typ.Len())), nil
	case *types.Basic:
		switch typ.Kind() {
		case types.Bool:
			return llvm.Int1Type(), nil
		case types.Int8, types.Uint8:
			return llvm.Int8Type(), nil
		case types.Int16, types.Uint16:
			return llvm.Int16Type(), nil
		case types.Int32, types.Uint32:
			return llvm.Int32Type(), nil
		case types.Int, types.Uint:
			return c.intType, nil
		case types.Int64, types.Uint64:
			return llvm.Int64Type(), nil
		case types.String:
			return c.stringType, nil
		case types.Uintptr:
			return c.uintptrType, nil
		case types.UnsafePointer:
			return c.i8ptrType, nil
		default:
			return llvm.Type{}, errors.New("todo: unknown basic type: " + fmt.Sprintf("%#v", typ))
		}
	case *types.Interface:
		return c.interfaceType, nil
	case *types.Named:
		return c.getLLVMType(typ.Underlying())
	case *types.Pointer:
		ptrTo, err := c.getLLVMType(typ.Elem())
		if err != nil {
			return llvm.Type{}, err
		}
		return llvm.PointerType(ptrTo, 0), nil
	case *types.Signature: // function pointer
		// return value
		var err error
		var returnType llvm.Type
		if typ.Results().Len() == 0 {
			returnType = llvm.VoidType()
		} else if typ.Results().Len() == 1 {
			returnType, err = c.getLLVMType(typ.Results().At(0).Type())
			if err != nil {
				return llvm.Type{}, err
			}
		} else {
			return llvm.Type{}, errors.New("todo: multiple return values in function pointer")
		}
		// param values
		var paramTypes []llvm.Type
		params := typ.Params()
		for i := 0; i < params.Len(); i++ {
			subType, err := c.getLLVMType(params.At(i).Type())
			if err != nil {
				return llvm.Type{}, err
			}
			paramTypes = append(paramTypes, subType)
		}
		// make a function pointer of it
		return llvm.PointerType(llvm.FunctionType(returnType, paramTypes, false), 0), nil
	case *types.Struct:
		members := make([]llvm.Type, typ.NumFields())
		for i := 0; i < typ.NumFields(); i++ {
			member, err := c.getLLVMType(typ.Field(i).Type())
			if err != nil {
				return llvm.Type{}, err
			}
			members[i] = member
		}
		return llvm.StructType(members, false), nil
	default:
		return llvm.Type{}, errors.New("todo: unknown type: " + fmt.Sprintf("%#v", goType))
	}
}

func (c *Compiler) getZeroValue(typ llvm.Type) (llvm.Value, error) {
	switch typ.TypeKind() {
	case llvm.ArrayTypeKind:
		subTyp := typ.ElementType()
		vals := make([]llvm.Value, typ.ArrayLength())
		for i := range vals {
			val, err := c.getZeroValue(subTyp)
			if err != nil {
				return llvm.Value{}, err
			}
			vals[i] = val
		}
		return llvm.ConstArray(subTyp, vals), nil
	case llvm.IntegerTypeKind:
		return llvm.ConstInt(typ, 0, false), nil
	case llvm.PointerTypeKind:
		return llvm.ConstPointerNull(typ), nil
	case llvm.StructTypeKind:
		types := typ.StructElementTypes()
		vals := make([]llvm.Value, len(types))
		for i, subTyp := range types {
			val, err := c.getZeroValue(subTyp)
			if err != nil {
				return llvm.Value{}, err
			}
			vals[i] = val
		}
		return llvm.ConstStruct(vals, false), nil
	default:
		return llvm.Value{}, errors.New("todo: LLVM zero initializer")
	}
}

func (c *Compiler) getInterfaceType(typ types.Type) llvm.Value {
	if _, ok := c.itfTypeNumbers[typ]; !ok {
		num := uint64(len(c.itfTypes))
		c.itfTypes = append(c.itfTypes, typ)
		c.itfTypeNumbers[typ] = num
	}
	return llvm.ConstInt(llvm.Int32Type(), c.itfTypeNumbers[typ], false)
}

func (c *Compiler) isPointer(typ types.Type) bool {
	if _, ok := typ.(*types.Pointer); ok {
		return true
	} else if typ, ok := typ.(*types.Basic); ok && typ.Kind() == types.UnsafePointer {
		return true
	} else {
		return false
	}
}

func getFunctionName(fn *ssa.Function, blocking bool) string {
	suffix := ""
	if blocking {
		suffix = "$async"
	}
	if fn.Signature.Recv() != nil {
		// Method on a defined type.
		typeName := fn.Params[0].Type().(*types.Named).Obj().Name()
		return pkgPrefix(fn.Pkg) + "." + typeName + "." + fn.Name() + suffix
	} else {
		// Bare function.
		if strings.HasPrefix(fn.Name(), "_Cfunc_") {
			// Name CGo functions directly.
			return fn.Name()[len("_Cfunc_"):]
		} else {
			name := pkgPrefix(fn.Pkg) + "." + fn.Name() + suffix
			if fn.Pkg.Pkg.Path() == "runtime" && strings.HasPrefix(fn.Name(), "_llvm_") {
				// Special case for LLVM intrinsics in the runtime.
				name = "llvm." + strings.Replace(fn.Name()[len("_llvm_"):], "_", ".", -1)
			}
			return name
		}
	}
}

func getGlobalName(global *ssa.Global) string {
	if strings.HasPrefix(global.Name(), "_extern_") {
		return global.Name()[len("_extern_"):]
	} else {
		return pkgPrefix(global.Pkg) + "." +  global.Name()
	}
}

func (c *Compiler) parsePackage(program *ssa.Program, pkg *ssa.Package) error {
	// Make sure we're walking through all members in a constant order every
	// run.
	memberNames := make([]string, 0)
	for name := range pkg.Members {
		if strings.HasPrefix(name, "_Cgo_") || strings.HasPrefix(name, "_cgo") {
			// _Cgo_ptr, _Cgo_use, _cgoCheckResult, _cgo_runtime_cgocall
			continue // CGo-internal functions
		}
		if strings.HasPrefix(name, "__cgofn__cgo_") {
			continue // CGo function pointer in global scope
		}
		memberNames = append(memberNames, name)
	}
	sort.Strings(memberNames)

	frames := make(map[*ssa.Function]*Frame)

	// First, build all function declarations.
	for _, name := range memberNames {
		member := pkg.Members[name]

		switch member := member.(type) {
		case *ssa.Function:
			frame, err := c.parseFuncDecl(member)
			if err != nil {
				return err
			}
			frames[member] = frame
			if member.Synthetic == "package initializer" {
				c.initFuncs = append(c.initFuncs, frame.llvmFn)
			}
			// TODO: recursively anonymous functions
			for _, child := range member.AnonFuncs {
				frame, err := c.parseFuncDecl(child)
				if err != nil {
					return err
				}
				frames[child] = frame
			}
		case *ssa.NamedConst:
			// Ignore package-level untyped constants. The SSA form doesn't need
			// them.
		case *ssa.Global:
			typ := member.Type()
			if typPtr, ok := typ.(*types.Pointer); ok {
				typ = typPtr.Elem()
			} else {
				return errors.New("global is not a pointer")
			}
			llvmType, err := c.getLLVMType(typ)
			if err != nil {
				return err
			}
			global := llvm.AddGlobal(c.mod, llvmType, getGlobalName(member))
			if !strings.HasPrefix(member.Name(), "_extern_") {
				global.SetLinkage(llvm.PrivateLinkage)
				if getGlobalName(member) == "runtime.TargetBits" {
					bitness := c.targetData.PointerSize() * 8
					if bitness < 32 {
						// Only 8 and 32+ architectures supported at the moment.
						// On 8 bit architectures, pointers are normally bigger
						// than 8 bits to do anything meaningful.
						// TODO: clean up this hack to support 16-bit
						// architectures.
						bitness = 8
					}
					global.SetInitializer(llvm.ConstInt(llvm.Int8Type(), uint64(bitness), false))
					global.SetGlobalConstant(true)
				} else {
					initializer, err := c.getZeroValue(llvmType)
					if err != nil {
						return err
					}
					global.SetInitializer(initializer)
				}
			}
		case *ssa.Type:
			ms := program.MethodSets.MethodSet(member.Type())
			for i := 0; i < ms.Len(); i++ {
				fn := program.MethodValue(ms.At(i))
				frame, err := c.parseFuncDecl(fn)
				if err != nil {
					return err
				}
				frames[fn] = frame
			}
		default:
			return errors.New("todo: member: " + fmt.Sprintf("%#v", member))
		}
	}

	// Now, add definitions to those declarations.
	for _, name := range memberNames {
		member := pkg.Members[name]
		switch member := member.(type) {
		case *ssa.Function:
			if strings.HasPrefix(name, "_Cfunc_") {
				// CGo function. Don't implement it's body.
				continue
			}
			if member.Blocks == nil {
				continue // external function
			}
			var err error
			if member.Synthetic == "package initializer" {
				err = c.parseInitFunc(frames[member], member)
			} else {
				err = c.parseFunc(frames[member], member)
			}
			if err != nil {
				return err
			}
		case *ssa.Type:
			ms := program.MethodSets.MethodSet(member.Type())
			for i := 0; i < ms.Len(); i++ {
				fn := program.MethodValue(ms.At(i))
				err := c.parseFunc(frames[fn], fn)
				if err != nil {
					return err
				}
			}
		}
	}

	return nil
}

func (c *Compiler) parseFuncDecl(f *ssa.Function) (*Frame, error) {
	f.WriteTo(os.Stdout)

	frame := &Frame{
		fn:       f,
		params:   make(map[*ssa.Parameter]int),
		locals:   make(map[ssa.Value]llvm.Value),
		blocks:   make(map[*ssa.BasicBlock]llvm.BasicBlock),
		blocking: c.analysis.IsBlocking(f),
	}

	var retType llvm.Type
	if frame.blocking {
		if f.Signature.Results() != nil {
			return nil, errors.New("todo: return values in blocking function")
		}
		retType = c.i8ptrType
	} else if f.Signature.Results() == nil {
		retType = llvm.VoidType()
	} else if f.Signature.Results().Len() == 1 {
		var err error
		retType, err = c.getLLVMType(f.Signature.Results().At(0).Type())
		if err != nil {
			return nil, err
		}
	} else {
		return nil, errors.New("todo: return values")
	}

	var paramTypes []llvm.Type
	if frame.blocking {
		paramTypes = append(paramTypes, c.i8ptrType) // parent coroutine
	}
	for i, param := range f.Params {
		paramType, err := c.getLLVMType(param.Type())
		if err != nil {
			return nil, err
		}
		paramTypes = append(paramTypes, paramType)
		frame.params[param] = i
	}

	fnType := llvm.FunctionType(retType, paramTypes, false)

	name := getFunctionName(f, frame.blocking)
	frame.llvmFn = c.mod.NamedFunction(name)
	if frame.llvmFn.IsNil() {
		frame.llvmFn = llvm.AddFunction(c.mod, name, fnType)
	}
	return frame, nil
}

// Special function parser for generated package initializers (which also
// initializes global variables).
func (c *Compiler) parseInitFunc(frame *Frame, f *ssa.Function) error {
	frame.llvmFn.SetLinkage(llvm.PrivateLinkage)
	llvmBlock := c.ctx.AddBasicBlock(frame.llvmFn, "entry")
	c.builder.SetInsertPointAtEnd(llvmBlock)

	for _, block := range f.DomPreorder() {
		for _, instr := range block.Instrs {
			var err error
			switch instr := instr.(type) {
			case *ssa.Call, *ssa.Return:
				err = c.parseInstr(frame, instr)
			case *ssa.Convert:
				// Ignore: CGo pointer conversion.
			case *ssa.FieldAddr, *ssa.IndexAddr:
				// Ignore: handled below with *ssa.Store.
			case *ssa.Store:
				switch addr := instr.Addr.(type) {
				case *ssa.Global:
					// Regular store, like a global int variable.
					if strings.HasPrefix(addr.Name(), "__cgofn__cgo_") || strings.HasPrefix(addr.Name(), "_cgo_") {
						// Ignore CGo global variables which we don't use.
						continue
					}
					val, err := c.parseExpr(frame, instr.Val)
					if err != nil {
						return err
					}
					llvmAddr := c.mod.NamedGlobal(getGlobalName(addr))
					llvmAddr.SetInitializer(val)
				case *ssa.FieldAddr:
					// Initialize field of a global struct.
					// LLVM does not allow setting an initializer on part of a
					// global variable. So we take the current initializer, add
					// the field, and replace the initializer with the new
					// initializer.
					val, err := c.parseExpr(frame, instr.Val)
					if err != nil {
						return err
					}
					global := addr.X.(*ssa.Global)
					llvmAddr := c.mod.NamedGlobal(getGlobalName(global))
					llvmValue := llvmAddr.Initializer()
					if llvmValue.IsNil() {
						llvmValue, err = c.getZeroValue(llvmAddr.Type().ElementType())
						if err != nil {
							return err
						}
					}
					llvmValue = c.builder.CreateInsertValue(llvmValue, val, addr.Field, "")
					llvmAddr.SetInitializer(llvmValue)
				case *ssa.IndexAddr:
					val, err := c.parseExpr(frame, instr.Val)
					if err != nil {
						return err
					}
					constIndex := addr.Index.(*ssa.Const)
					index, exact := constant.Int64Val(constIndex.Value)
					if !exact {
						return errors.New("could not get store index: " + constIndex.Value.ExactString())
					}
					fieldAddr := addr.X.(*ssa.FieldAddr)
					global := fieldAddr.X.(*ssa.Global)
					llvmAddr := c.mod.NamedGlobal(getGlobalName(global))
					llvmValue := llvmAddr.Initializer()
					if llvmValue.IsNil() {
						llvmValue, err = c.getZeroValue(llvmAddr.Type().ElementType())
						if err != nil {
							return err
						}
					}
					llvmFieldValue := c.builder.CreateExtractValue(llvmValue, fieldAddr.Field, "")
					llvmFieldValue = c.builder.CreateInsertValue(llvmFieldValue, val, int(index), "")
					llvmValue = c.builder.CreateInsertValue(llvmValue, llvmFieldValue, fieldAddr.Field, "")
					llvmAddr.SetInitializer(llvmValue)
				default:
					return errors.New("unknown init store: " + fmt.Sprintf("%#v", addr))
				}
			default:
				return errors.New("unknown init instruction: " + fmt.Sprintf("%#v", instr))
			}
			if err != nil {
				return err
			}
		}
	}
	return nil
}

func (c *Compiler) parseFunc(frame *Frame, f *ssa.Function) error {
	frame.llvmFn.SetLinkage(llvm.PrivateLinkage)

	// Pre-create all basic blocks in the function.
	for _, block := range f.DomPreorder() {
		llvmBlock := c.ctx.AddBasicBlock(frame.llvmFn, block.Comment)
		frame.blocks[block] = llvmBlock
	}
	if frame.blocking {
		frame.cleanupBlock = c.ctx.AddBasicBlock(frame.llvmFn, "task.cleanup")
		frame.suspendBlock = c.ctx.AddBasicBlock(frame.llvmFn, "task.suspend")
	}

	// Load function parameters
	for _, param := range f.Params {
		llvmParam := frame.llvmFn.Param(frame.params[param])
		frame.locals[param] = llvmParam
	}

	if frame.blocking {
		// Coroutine initialization.
		c.builder.SetInsertPointAtEnd(frame.blocks[f.Blocks[0]])
		frame.taskState = c.builder.CreateAlloca(c.taskDataType, "task.state")
		stateI8 := c.builder.CreateBitCast(frame.taskState, c.i8ptrType, "task.state.i8")
		id := c.builder.CreateCall(c.coroIdFunc, []llvm.Value{
			llvm.ConstInt(llvm.Int32Type(), 0, false),
			stateI8,
			llvm.ConstNull(c.i8ptrType),
			llvm.ConstNull(c.i8ptrType),
		}, "task.token")
		size := c.builder.CreateCall(c.coroSizeFunc, nil, "task.size")
		if c.targetData.TypeAllocSize(size.Type()) > c.targetData.TypeAllocSize(c.uintptrType) {
			size = c.builder.CreateTrunc(size, c.uintptrType, "task.size.uintptr")
		} else if c.targetData.TypeAllocSize(size.Type()) < c.targetData.TypeAllocSize(c.uintptrType) {
			size = c.builder.CreateZExt(size, c.uintptrType, "task.size.uintptr")
		}
		data := c.builder.CreateCall(c.allocFunc, []llvm.Value{size}, "task.data")
		frame.taskHandle = c.builder.CreateCall(c.coroBeginFunc, []llvm.Value{id, data}, "task.handle")

		// Coroutine cleanup. Free resources associated with this coroutine.
		c.builder.SetInsertPointAtEnd(frame.cleanupBlock)
		mem := c.builder.CreateCall(c.coroFreeFunc, []llvm.Value{id, frame.taskHandle}, "task.data.free")
		c.builder.CreateCall(c.freeFunc, []llvm.Value{mem}, "")
		// re-insert parent coroutine
		c.builder.CreateCall(c.mod.NamedFunction("runtime.scheduleTask"), []llvm.Value{frame.llvmFn.FirstParam()}, "")
		c.builder.CreateBr(frame.suspendBlock)

		// Coroutine suspend. A call to llvm.coro.suspend() will branch here.
		c.builder.SetInsertPointAtEnd(frame.suspendBlock)
		c.builder.CreateCall(c.coroEndFunc, []llvm.Value{frame.taskHandle, llvm.ConstInt(llvm.Int1Type(), 0, false)}, "unused")
		c.builder.CreateRet(frame.taskHandle)
	}

	// Fill blocks with instructions.
	for _, block := range f.DomPreorder() {
		c.builder.SetInsertPointAtEnd(frame.blocks[block])
		for _, instr := range block.Instrs {
			err := c.parseInstr(frame, instr)
			if err != nil {
				return err
			}
		}
	}

	// Resolve phi nodes
	for _, phi := range frame.phis {
		block := phi.ssa.Block()
		for i, edge := range phi.ssa.Edges {
			llvmVal, err := c.parseExpr(frame, edge)
			if err != nil {
				return err
			}
			llvmBlock := frame.blocks[block.Preds[i]]
			phi.llvm.AddIncoming([]llvm.Value{llvmVal}, []llvm.BasicBlock{llvmBlock})
		}
	}

	return nil
}

func (c *Compiler) parseInstr(frame *Frame, instr ssa.Instruction) error {
	switch instr := instr.(type) {
	case ssa.Value:
		value, err := c.parseExpr(frame, instr)
		frame.locals[instr] = value
		return err
	case *ssa.Go:
		if instr.Common().Method != nil {
			return errors.New("todo: go on method receiver")
		}

		// Execute non-blocking calls (including builtins) directly.
		// parentHandle param is ignored.
		if !c.analysis.IsBlocking(instr.Common().Value) {
			_, err := c.parseCall(frame, instr.Common(), llvm.Value{})
			return err // probably nil
		}

		// Start this goroutine.
		// parentHandle is nil, as the goroutine has no parent frame (it's a new
		// stack).
		handle, err := c.parseCall(frame, instr.Common(), llvm.Value{})
		if err != nil {
			return err
		}
		c.builder.CreateCall(c.mod.NamedFunction("runtime.scheduleTask"), []llvm.Value{handle}, "")
		return nil
	case *ssa.If:
		cond, err := c.parseExpr(frame, instr.Cond)
		if err != nil {
			return err
		}
		block := instr.Block()
		blockThen := frame.blocks[block.Succs[0]]
		blockElse := frame.blocks[block.Succs[1]]
		c.builder.CreateCondBr(cond, blockThen, blockElse)
		return nil
	case *ssa.Jump:
		blockJump := frame.blocks[instr.Block().Succs[0]]
		c.builder.CreateBr(blockJump)
		return nil
	case *ssa.Panic:
		value, err := c.parseExpr(frame, instr.X)
		if err != nil {
			return err
		}
		c.builder.CreateCall(c.mod.NamedFunction("runtime._panic"), []llvm.Value{value}, "")
		c.builder.CreateUnreachable()
		return nil
	case *ssa.Return:
		if frame.blocking {
			if len(instr.Results) != 0 {
				return errors.New("todo: return values from blocking function")
			}
			// Final suspend.
			continuePoint := c.builder.CreateCall(c.coroSuspendFunc, []llvm.Value{
				llvm.ConstNull(c.ctx.TokenType()),
				llvm.ConstInt(llvm.Int1Type(), 1, false), // final=true
			}, "")
			sw := c.builder.CreateSwitch(continuePoint, frame.suspendBlock, 2)
			sw.AddCase(llvm.ConstInt(llvm.Int8Type(), 1, false), frame.cleanupBlock)
			return nil
		} else {
			if len(instr.Results) == 0 {
				c.builder.CreateRetVoid()
				return nil
			} else if len(instr.Results) == 1 {
				val, err := c.parseExpr(frame, instr.Results[0])
				if err != nil {
					return err
				}
				c.builder.CreateRet(val)
				return nil
			} else {
				return errors.New("todo: return value")
			}
		}
	case *ssa.Store:
		llvmAddr, err := c.parseExpr(frame, instr.Addr)
		if err != nil {
			return err
		}
		llvmVal, err := c.parseExpr(frame, instr.Val)
		if err != nil {
			return err
		}
		valType := instr.Addr.Type().(*types.Pointer).Elem()
		if valType, ok := valType.(*types.Named); ok && valType.Obj().Name() == "__reg" {
			// Magic type name to transform this store to a register store.
			registerAddr := c.builder.CreateLoad(llvmAddr, "")
			ptr := c.builder.CreateIntToPtr(registerAddr, llvmAddr.Type(), "")
			store := c.builder.CreateStore(llvmVal, ptr)
			store.SetVolatile(true)
		} else {
			c.builder.CreateStore(llvmVal, llvmAddr)
		}
		return nil
	default:
		return errors.New("unknown instruction: " + fmt.Sprintf("%#v", instr))
	}
}

func (c *Compiler) parseBuiltin(frame *Frame, args []ssa.Value, callName string) (llvm.Value, error) {
	switch callName {
	case "print", "println":
		for i, arg := range args {
			if i >= 1 {
				c.builder.CreateCall(c.mod.NamedFunction("runtime.printspace"), nil, "")
			}
			value, err := c.parseExpr(frame, arg)
			if err != nil {
				return llvm.Value{}, err
			}
			typ := arg.Type()
			if _, ok := typ.(*types.Named); ok {
				typ = typ.Underlying()
			}
			switch typ := typ.(type) {
			case *types.Basic:
				switch typ.Kind() {
				case types.Int8:
					c.builder.CreateCall(c.mod.NamedFunction("runtime.printint8"), []llvm.Value{value}, "")
				case types.Uint8:
					c.builder.CreateCall(c.mod.NamedFunction("runtime.printuint8"), []llvm.Value{value}, "")
				case types.Int, types.Int32: // TODO: assumes a 32-bit int type
					c.builder.CreateCall(c.mod.NamedFunction("runtime.printint32"), []llvm.Value{value}, "")
				case types.Uint, types.Uint32:
					c.builder.CreateCall(c.mod.NamedFunction("runtime.printuint32"), []llvm.Value{value}, "")
				case types.Int64:
					c.builder.CreateCall(c.mod.NamedFunction("runtime.printint64"), []llvm.Value{value}, "")
				case types.Uint64:
					c.builder.CreateCall(c.mod.NamedFunction("runtime.printuint64"), []llvm.Value{value}, "")
				case types.String:
					c.builder.CreateCall(c.mod.NamedFunction("runtime.printstring"), []llvm.Value{value}, "")
				case types.Uintptr:
					c.builder.CreateCall(c.mod.NamedFunction("runtime.printptr"), []llvm.Value{value}, "")
				case types.UnsafePointer:
					ptrValue := c.builder.CreatePtrToInt(value, c.uintptrType, "")
					c.builder.CreateCall(c.mod.NamedFunction("runtime.printptr"), []llvm.Value{ptrValue}, "")
				default:
					return llvm.Value{}, errors.New("unknown basic arg type: " + fmt.Sprintf("%#v", typ))
				}
			case *types.Pointer:
				ptrValue := c.builder.CreatePtrToInt(value, c.uintptrType, "")
				c.builder.CreateCall(c.mod.NamedFunction("runtime.printptr"), []llvm.Value{ptrValue}, "")
			default:
				return llvm.Value{}, errors.New("unknown arg type: " + fmt.Sprintf("%#v", typ))
			}
		}
		if callName == "println" {
			c.builder.CreateCall(c.mod.NamedFunction("runtime.printnl"), nil, "")
		}
		return llvm.Value{}, nil // print() or println() returns void
	case "len":
		value, err := c.parseExpr(frame, args[0])
		if err != nil {
			return llvm.Value{}, err
		}
		switch typ := args[0].Type().(type) {
		case *types.Basic:
			switch typ.Kind() {
			case types.String:
				return c.builder.CreateExtractValue(value, 0, "len"), nil
			default:
				return llvm.Value{}, errors.New("todo: len: unknown basic type")
			}
		default:
			return llvm.Value{}, errors.New("todo: len: unknown type")
		}
	default:
		return llvm.Value{}, errors.New("todo: builtin: " + callName)
	}
}

func (c *Compiler) parseFunctionCall(frame *Frame, call *ssa.CallCommon, llvmFn llvm.Value, blocking bool, parentHandle llvm.Value) (llvm.Value, error) {
	var params []llvm.Value
	if blocking {
		if parentHandle.IsNil() {
			// Started from 'go' statement.
			params = append(params, llvm.ConstNull(c.i8ptrType))
		} else {
			// Blocking function calls another blocking function.
			params = append(params, parentHandle)
		}
	}
	for _, param := range call.Args {
		val, err := c.parseExpr(frame, param)
		if err != nil {
			return llvm.Value{}, err
		}
		params = append(params, val)
	}

	if frame.blocking && llvmFn.Name() == "runtime.Sleep" {
		// Set task state to TASK_STATE_SLEEP and set the duration.
		c.builder.CreateCall(c.mod.NamedFunction("runtime.sleepTask"), []llvm.Value{frame.taskHandle, params[0]}, "")

		// Yield to scheduler.
		continuePoint := c.builder.CreateCall(c.coroSuspendFunc, []llvm.Value{
			llvm.ConstNull(c.ctx.TokenType()),
			llvm.ConstInt(llvm.Int1Type(), 0, false),
		}, "")
		wakeup := c.ctx.InsertBasicBlock(llvm.NextBasicBlock(c.builder.GetInsertBlock()), "task.wakeup")
		sw := c.builder.CreateSwitch(continuePoint, frame.suspendBlock, 2)
		sw.AddCase(llvm.ConstInt(llvm.Int8Type(), 0, false), wakeup)
		sw.AddCase(llvm.ConstInt(llvm.Int8Type(), 1, false), frame.cleanupBlock)
		c.builder.SetInsertPointAtEnd(wakeup)

		return llvm.Value{}, nil
	}

	result := c.builder.CreateCall(llvmFn, params, "")
	if blocking && !parentHandle.IsNil() {
		// Calling a blocking function as a regular function call.
		// This is done by passing the current coroutine as a parameter to the
		// new coroutine and dropping the current coroutine from the scheduler
		// (with the TASK_STATE_CALL state). When the subroutine is finished, it
		// will reactivate the parent (this frame) in it's destroy function.

		c.builder.CreateCall(c.mod.NamedFunction("runtime.scheduleTask"), []llvm.Value{result}, "")

		// Set task state to TASK_STATE_CALL.
		c.builder.CreateCall(c.mod.NamedFunction("runtime.waitForAsyncCall"), []llvm.Value{frame.taskHandle}, "")

		// Yield to the scheduler.
		continuePoint := c.builder.CreateCall(c.coroSuspendFunc, []llvm.Value{
			llvm.ConstNull(c.ctx.TokenType()),
			llvm.ConstInt(llvm.Int1Type(), 0, false),
		}, "")
		resume := c.ctx.InsertBasicBlock(llvm.NextBasicBlock(c.builder.GetInsertBlock()), "task.callComplete")
		sw := c.builder.CreateSwitch(continuePoint, frame.suspendBlock, 2)
		sw.AddCase(llvm.ConstInt(llvm.Int8Type(), 0, false), resume)
		sw.AddCase(llvm.ConstInt(llvm.Int8Type(), 1, false), frame.cleanupBlock)
		c.builder.SetInsertPointAtEnd(resume)
	}
	return result, nil
}

func (c *Compiler) parseCall(frame *Frame, instr *ssa.CallCommon, parentHandle llvm.Value) (llvm.Value, error) {
	switch call := instr.Value.(type) {
	case *ssa.Builtin:
		return c.parseBuiltin(frame, instr.Args, call.Name())
	case *ssa.Function:
		targetBlocks := false
		name := getFunctionName(call, targetBlocks)
		llvmFn := c.mod.NamedFunction(name)
		if llvmFn.IsNil() {
			targetBlocks = true
			nameAsync := getFunctionName(call, targetBlocks)
			llvmFn = c.mod.NamedFunction(nameAsync)
			if llvmFn.IsNil() {
				return llvm.Value{}, errors.New("undefined function: " + name)
			}
		}
		return c.parseFunctionCall(frame, instr, llvmFn, targetBlocks, parentHandle)
	default: // function pointer
		value, err := c.parseExpr(frame, instr.Value)
		if err != nil {
			return llvm.Value{}, err
		}
		// TODO: blocking function pointers (needs analysis)
		return c.parseFunctionCall(frame, instr, value, false, parentHandle)
	}
}

func (c *Compiler) parseExpr(frame *Frame, expr ssa.Value) (llvm.Value, error) {
	if frame != nil {
		if value, ok := frame.locals[expr]; ok {
			// Value is a local variable that has already been computed.
			if value.IsNil() {
				return llvm.Value{}, errors.New("undefined local var (from cgo?)")
			}
			return value, nil
		}
	}

	switch expr := expr.(type) {
	case *ssa.Alloc:
		typ, err := c.getLLVMType(expr.Type().Underlying().(*types.Pointer).Elem())
		if err != nil {
			return llvm.Value{}, err
		}
		var buf llvm.Value
		if expr.Heap {
			// TODO: escape analysis
			size := llvm.ConstInt(c.uintptrType, c.targetData.TypeAllocSize(typ), false)
			buf = c.builder.CreateCall(c.allocFunc, []llvm.Value{size}, expr.Comment)
			buf = c.builder.CreateBitCast(buf, llvm.PointerType(typ, 0), "")
		} else {
			buf = c.builder.CreateAlloca(typ, expr.Comment)
			zero, err := c.getZeroValue(typ)
			if err != nil {
				return llvm.Value{}, err
			}
			c.builder.CreateStore(zero, buf) // zero-initialize var
		}
		return buf, nil
	case *ssa.BinOp:
		return c.parseBinOp(frame, expr)
	case *ssa.Call:
		// Passing the current task here to the subroutine. It is only used when
		// the subroutine is blocking.
		return c.parseCall(frame, expr.Common(), frame.taskHandle)
	case *ssa.ChangeType:
		return c.parseConvert(frame, expr.Type(), expr.X)
	case *ssa.Const:
		return c.parseConst(expr)
	case *ssa.Convert:
		return c.parseConvert(frame, expr.Type(), expr.X)
	case *ssa.Extract:
		value, err := c.parseExpr(frame, expr.Tuple)
		if err != nil {
			return llvm.Value{}, err
		}
		result := c.builder.CreateExtractValue(value, expr.Index, "")
		return result, nil
	case *ssa.FieldAddr:
		val, err := c.parseExpr(frame, expr.X)
		if err != nil {
			return llvm.Value{}, err
		}
		indices := []llvm.Value{
			llvm.ConstInt(llvm.Int32Type(), 0, false),
			llvm.ConstInt(llvm.Int32Type(), uint64(expr.Field), false),
		}
		return c.builder.CreateGEP(val, indices, ""), nil
	case *ssa.Function:
		return c.mod.NamedFunction(getFunctionName(expr, false)), nil
	case *ssa.Global:
		fullName := getGlobalName(expr)
		value := c.mod.NamedGlobal(fullName)
		if value.IsNil() {
			return llvm.Value{}, errors.New("global not found: " + fullName)
		}
		return value, nil
	case *ssa.IndexAddr:
		val, err := c.parseExpr(frame, expr.X)
		if err != nil {
			return llvm.Value{}, err
		}
		index, err := c.parseExpr(frame, expr.Index)
		if err != nil {
			return llvm.Value{}, err
		}

		// Get buffer length
		var buflen llvm.Value
		typ := expr.X.Type().(*types.Pointer).Elem()
		switch typ := typ.(type) {
		case *types.Array:
			buflen = llvm.ConstInt(llvm.Int32Type(), uint64(typ.Len()), false)
		default:
			return llvm.Value{}, errors.New("todo: indexaddr: len")
		}

		// Bounds check.
		// LLVM optimizes this away in most cases.
		// TODO: runtime.boundsCheck is undefined in packages imported by
		// package runtime, so we have to remove it. This should be fixed.
		boundsCheck := c.mod.NamedFunction("runtime.boundsCheck")
		if !boundsCheck.IsNil() {
			constZero := llvm.ConstInt(c.intType, 0, false)
			isNegative := c.builder.CreateICmp(llvm.IntSLT, index, constZero, "") // index < 0
			isTooBig := c.builder.CreateICmp(llvm.IntSGE, index, buflen, "") // index >= len(value)
			isOverflow := c.builder.CreateOr(isNegative, isTooBig, "")
			c.builder.CreateCall(boundsCheck, []llvm.Value{isOverflow}, "")
		}

		indices := []llvm.Value{
			llvm.ConstInt(llvm.Int32Type(), 0, false),
			index,
		}
		return c.builder.CreateGEP(val, indices, ""), nil
	case *ssa.Lookup:
		if expr.CommaOk {
			return llvm.Value{}, errors.New("todo: lookup with comma-ok")
		}
		if _, ok := expr.X.Type().(*types.Map); ok {
			return llvm.Value{}, errors.New("todo: lookup in map")
		}
		// Value type must be a string, which is a basic type.
		if expr.X.Type().(*types.Basic).Kind() != types.String {
			panic("lookup on non-string?")
		}
		value, err := c.parseExpr(frame, expr.X)
		if err != nil {
			return llvm.Value{}, nil
		}
		index, err := c.parseExpr(frame, expr.Index)
		if err != nil {
			return llvm.Value{}, nil
		}

		// Bounds check.
		// LLVM optimizes this away in most cases.
		if frame.llvmFn.Name() != "runtime.boundsCheck" {
			constZero := llvm.ConstInt(c.intType, 0, false)
			isNegative := c.builder.CreateICmp(llvm.IntSLT, index, constZero, "") // index < 0
			strlen, err := c.parseBuiltin(frame, []ssa.Value{expr.X}, "len")
			if err != nil {
				return llvm.Value{}, err // shouldn't happen
			}
			isTooBig := c.builder.CreateICmp(llvm.IntSGE, index, strlen, "") // index >= len(value)
			isOverflow := c.builder.CreateOr(isNegative, isTooBig, "")
			c.builder.CreateCall(c.mod.NamedFunction("runtime.boundsCheck"), []llvm.Value{isOverflow}, "")
		}

		// Lookup byte
		buf := c.builder.CreateExtractValue(value, 1, "")
		bufPtr := c.builder.CreateGEP(buf, []llvm.Value{index}, "")
		return c.builder.CreateLoad(bufPtr, ""), nil
	case *ssa.MakeInterface:
		val, err := c.parseExpr(frame, expr.X)
		if err != nil {
			return llvm.Value{}, err
		}
		var itfValue llvm.Value
		switch typ := expr.X.Type().(type) {
		case *types.Basic:
			if typ.Info() & types.IsInteger != 0 { // TODO: 64-bit int on 32-bit platform
				itfValue = c.builder.CreateIntToPtr(val, c.i8ptrType, "")
			} else if typ.Kind() == types.String {
				// TODO: escape analysis
				size := c.targetData.TypeAllocSize(c.stringType)
				sizeValue := llvm.ConstInt(c.uintptrType, size, false)
				itfValue = c.builder.CreateCall(c.allocFunc, []llvm.Value{sizeValue}, "")
				itfValueCast := c.builder.CreateBitCast(itfValue, llvm.PointerType(c.stringType, 0), "")
				c.builder.CreateStore(val, itfValueCast)
			} else {
				return llvm.Value{}, errors.New("todo: make interface: unknown basic type")
			}
		default:
			return llvm.Value{}, errors.New("todo: make interface: unknown type")
		}
		itfType := c.getInterfaceType(expr.X.Type())
		itf := c.ctx.ConstStruct([]llvm.Value{itfType, llvm.Undef(c.i8ptrType)}, false)
		itf = c.builder.CreateInsertValue(itf, itfValue, 1, "")
		return itf, nil
	case *ssa.Phi:
		t, err := c.getLLVMType(expr.Type())
		if err != nil {
			return llvm.Value{}, err
		}
		phi := c.builder.CreatePHI(t, "")
		frame.phis = append(frame.phis, Phi{expr, phi})
		return phi, nil
	case *ssa.TypeAssert:
		if !expr.CommaOk {
			return llvm.Value{}, errors.New("todo: type assert without comma-ok")
		}
		itf, err := c.parseExpr(frame, expr.X)
		if err != nil {
			return llvm.Value{}, err
		}
		assertedType, err := c.getLLVMType(expr.AssertedType)
		if err != nil {
			return llvm.Value{}, err
		}
		assertedTypeNum := c.getInterfaceType(expr.AssertedType)
		actualTypeNum := c.builder.CreateExtractValue(itf, 0, "interface.type")
		valuePtr := c.builder.CreateExtractValue(itf, 1, "interface.value")
		var value llvm.Value
		switch typ := expr.AssertedType.(type) {
		case *types.Basic:
			if typ.Info() & types.IsInteger != 0 {
				value = c.builder.CreatePtrToInt(valuePtr, assertedType, "")
			} else if typ.Kind() == types.String {
				valueStringPtr := c.builder.CreateBitCast(valuePtr, llvm.PointerType(c.stringType, 0), "")
				value = c.builder.CreateLoad(valueStringPtr, "")
			} else {
				return llvm.Value{}, errors.New("todo: typeassert: unknown basic type")
			}
		default:
			return llvm.Value{}, errors.New("todo: typeassert: unknown type")
		}
		commaOk := c.builder.CreateICmp(llvm.IntEQ, assertedTypeNum, actualTypeNum, "")
		tuple := llvm.ConstStruct([]llvm.Value{llvm.Undef(assertedType), llvm.Undef(llvm.Int1Type())}, false) // create empty tuple
		tuple = c.builder.CreateInsertValue(tuple, value, 0, "") // insert value
		tuple = c.builder.CreateInsertValue(tuple, commaOk, 1, "") // insert 'comma ok' boolean
		return tuple, nil
	case *ssa.UnOp:
		return c.parseUnOp(frame, expr)
	default:
		return llvm.Value{}, errors.New("todo: unknown expression: " + fmt.Sprintf("%#v", expr))
	}
}

func (c *Compiler) parseBinOp(frame *Frame, binop *ssa.BinOp) (llvm.Value, error) {
	x, err := c.parseExpr(frame, binop.X)
	if err != nil {
		return llvm.Value{}, err
	}
	y, err := c.parseExpr(frame, binop.Y)
	if err != nil {
		return llvm.Value{}, err
	}
	typ := binop.X.Type()
	if typNamed, ok := typ.(*types.Named); ok {
		typ = typNamed.Underlying()
	}
	signed := typ.(*types.Basic).Info() & types.IsUnsigned == 0
	switch binop.Op {
	case token.ADD: // +
		return c.builder.CreateAdd(x, y, ""), nil
	case token.SUB: // -
		return c.builder.CreateSub(x, y, ""), nil
	case token.MUL: // *
		return c.builder.CreateMul(x, y, ""), nil
	case token.QUO: // /
		if signed {
			return c.builder.CreateSDiv(x, y, ""), nil
		} else {
			return c.builder.CreateUDiv(x, y, ""), nil
		}
	case token.REM: // %
		if signed {
			return c.builder.CreateSRem(x, y, ""), nil
		} else {
			return c.builder.CreateURem(x, y, ""), nil
		}
	case token.AND: // &
		return c.builder.CreateAnd(x, y, ""), nil
	case token.OR:  // |
		return c.builder.CreateOr(x, y, ""), nil
	case token.XOR: // ^
		return c.builder.CreateXor(x, y, ""), nil
	case token.SHL: // <<
		return c.builder.CreateShl(x, y, ""), nil
	case token.SHR: // >>
		if signed {
			return c.builder.CreateAShr(x, y, ""), nil
		} else {
			return c.builder.CreateLShr(x, y, ""), nil
		}
	case token.AND_NOT: // &^
		// Go specific. Calculate "and not" with x & (~y)
		inv := c.builder.CreateNot(y, "") // ~y
		return c.builder.CreateAnd(x, inv, ""), nil
	case token.EQL: // ==
		return c.builder.CreateICmp(llvm.IntEQ, x, y, ""), nil
	case token.NEQ: // !=
		return c.builder.CreateICmp(llvm.IntNE, x, y, ""), nil
	case token.LSS: // <
		if signed {
			return c.builder.CreateICmp(llvm.IntSLT, x, y, ""), nil
		} else {
			return c.builder.CreateICmp(llvm.IntULT, x, y, ""), nil
		}
	case token.LEQ: // <=
		if signed {
			return c.builder.CreateICmp(llvm.IntSLE, x, y, ""), nil
		} else {
			return c.builder.CreateICmp(llvm.IntULE, x, y, ""), nil
		}
	case token.GTR: // >
		if signed {
			return c.builder.CreateICmp(llvm.IntSGT, x, y, ""), nil
		} else {
			return c.builder.CreateICmp(llvm.IntUGT, x, y, ""), nil
		}
	case token.GEQ: // >=
		if signed {
			return c.builder.CreateICmp(llvm.IntSGE, x, y, ""), nil
		} else {
			return c.builder.CreateICmp(llvm.IntUGE, x, y, ""), nil
		}
	default:
		return llvm.Value{}, errors.New("unknown binop")
	}
}

func (c *Compiler) parseConst(expr *ssa.Const) (llvm.Value, error) {
	typ := expr.Type()
	if named, ok := typ.(*types.Named); ok {
		typ = named.Underlying()
	}
	switch typ := typ.(type) {
	case *types.Basic:
		llvmType, err := c.getLLVMType(typ)
		if err != nil {
			return llvm.Value{}, err
		}
		if typ.Kind() == types.Bool {
			b := constant.BoolVal(expr.Value)
			n := uint64(0)
			if b {
				n = 1
			}
			return llvm.ConstInt(llvmType, n, false), nil
		} else if typ.Kind() == types.String {
			str := constant.StringVal(expr.Value)
			strLen := llvm.ConstInt(c.stringLenType, uint64(len(str)), false)
			strPtr := c.builder.CreateGlobalStringPtr(str, ".str") // TODO: remove \0 at end
			strObj := llvm.ConstStruct([]llvm.Value{strLen, strPtr}, false)
			return strObj, nil
		} else if typ.Kind() == types.UnsafePointer {
			if !expr.IsNil() {
				return llvm.Value{}, errors.New("todo: non-null constant pointer")
			}
			return llvm.ConstNull(c.i8ptrType), nil
		} else if typ.Info() & types.IsUnsigned != 0 {
			n, _ := constant.Uint64Val(expr.Value)
			return llvm.ConstInt(llvmType, n, false), nil
		} else if typ.Info() & types.IsInteger != 0 { // signed
			n, _ := constant.Int64Val(expr.Value)
			return llvm.ConstInt(llvmType, uint64(n), true), nil
		} else {
			return llvm.Value{}, errors.New("todo: unknown constant: " + fmt.Sprintf("%v", typ))
		}
	default:
		return llvm.Value{}, errors.New("todo: unknown constant: " + fmt.Sprintf("%#v", typ))
	}
}

func (c *Compiler) parseConvert(frame *Frame, typeTo types.Type, x ssa.Value) (llvm.Value, error) {
	value, err := c.parseExpr(frame, x)
	if err != nil {
		return value, nil
	}

	llvmTypeFrom, err := c.getLLVMType(x.Type())
	if err != nil {
		return llvm.Value{}, err
	}
	llvmTypeTo, err := c.getLLVMType(typeTo)
	if err != nil {
		return llvm.Value{}, err
	}

	switch typeTo := typeTo.(type) {
	case *types.Basic:
		isPtrFrom := c.isPointer(x.Type())
		isPtrTo := c.isPointer(typeTo)
		if isPtrFrom && !isPtrTo {
			return c.builder.CreatePtrToInt(value, llvmTypeTo, ""), nil
		} else if !isPtrFrom && isPtrTo {
			return c.builder.CreateIntToPtr(value, llvmTypeTo, ""), nil
		}

		sizeFrom := c.targetData.TypeAllocSize(llvmTypeFrom)
		sizeTo := c.targetData.TypeAllocSize(llvmTypeTo)
		if sizeFrom == sizeTo {
			return c.builder.CreateBitCast(value, llvmTypeTo, ""), nil
		}

		if typeTo.Info() & types.IsInteger == 0 { // if not integer
			return llvm.Value{}, errors.New("todo: convert: extend non-integer type")
		}

		if sizeFrom > sizeTo {
			return c.builder.CreateTrunc(value, llvmTypeTo, ""), nil
		} else if typeTo.Info() & types.IsUnsigned != 0 { // if unsigned
			return c.builder.CreateZExt(value, llvmTypeTo, ""), nil
		} else { // if signed
			return c.builder.CreateSExt(value, llvmTypeTo, ""), nil
		}
	case *types.Named:
		return c.parseConvert(frame, typeTo.Underlying(), x)
	case *types.Pointer:
		return c.builder.CreateBitCast(value, llvmTypeTo, ""), nil
	default:
		return llvm.Value{}, errors.New("todo: convert: extend non-basic type: " + fmt.Sprintf("%#v", typeTo))
	}
}

func (c *Compiler) parseUnOp(frame *Frame, unop *ssa.UnOp) (llvm.Value, error) {
	x, err := c.parseExpr(frame, unop.X)
	if err != nil {
		return llvm.Value{}, err
	}
	switch unop.Op {
	case token.NOT: // !x
		return c.builder.CreateNot(x, ""), nil
	case token.SUB: // -x
		return c.builder.CreateSub(llvm.ConstInt(x.Type(), 0, false), x, ""), nil
	case token.MUL: // *x, dereference pointer
		valType := unop.X.Type().(*types.Pointer).Elem()
		if valType, ok := valType.(*types.Named); ok && valType.Obj().Name() == "__reg" {
			// Magic type name: treat the value as a register pointer.
			register := unop.X.(*ssa.FieldAddr)
			global := register.X.(*ssa.Global)
			llvmGlobal := c.mod.NamedGlobal(getGlobalName(global))
			llvmAddr := c.builder.CreateExtractValue(llvmGlobal.Initializer(), register.Field, "")
			ptr := llvm.ConstIntToPtr(llvmAddr, x.Type())
			load := c.builder.CreateLoad(ptr, "")
			load.SetVolatile(true)
			return load, nil
		} else {
			return c.builder.CreateLoad(x, ""), nil
		}
	case token.XOR: // ^x, toggle all bits in integer
		return c.builder.CreateXor(x, llvm.ConstInt(x.Type(), ^uint64(0), false), ""), nil
	default:
		return llvm.Value{}, errors.New("todo: unknown unop")
	}
}

// IR returns the whole IR as a human-readable string.
func (c *Compiler) IR() string {
	return c.mod.String()
}

func (c *Compiler) Verify() error {
	return llvm.VerifyModule(c.mod, 0)
}

func (c *Compiler) LinkModule(mod llvm.Module) error {
	return llvm.LinkModules(c.mod, mod)
}

func (c *Compiler) ApplyFunctionSections() {
	// Put every function in a separate section. This makes it possible for the
	// linker to remove dead code (-ffunction-sections).
	llvmFn := c.mod.FirstFunction()
	for !llvmFn.IsNil() {
		if !llvmFn.IsDeclaration() {
			name := llvmFn.Name()
			if strings.HasSuffix(name, "$async") {
				name = name[:len(name)-len("$async")]
			}
			llvmFn.SetSection(".text." + name)
		}
		llvmFn = llvm.NextFunction(llvmFn)
	}
}

func (c *Compiler) Optimize(optLevel, sizeLevel int) {
	builder := llvm.NewPassManagerBuilder()
	defer builder.Dispose()
	builder.SetOptLevel(optLevel)
	builder.SetSizeLevel(sizeLevel)
	builder.UseInlinerWithThreshold(200) // TODO depend on opt level, and -Os

	funcPasses := llvm.NewFunctionPassManagerForModule(c.mod)
	defer funcPasses.Dispose()
	builder.PopulateFunc(funcPasses)

	modPasses := llvm.NewPassManager()
	defer modPasses.Dispose()
	builder.Populate(modPasses)

	modPasses.Run(c.mod)
}

func (c *Compiler) EmitObject(path string) error {
	// Generate output
	var buf []byte
	if strings.HasSuffix(path, ".o") {
		llvmBuf, err := c.machine.EmitToMemoryBuffer(c.mod, llvm.ObjectFile)
		if err != nil {
			return err
		}
		buf = llvmBuf.Bytes()
	} else if strings.HasSuffix(path, ".bc") {
		buf = llvm.WriteBitcodeToMemoryBuffer(c.mod).Bytes()
	} else if strings.HasSuffix(path, ".ll") {
		buf = []byte(c.mod.String())
	} else {
		return errors.New("unknown output file extension")
	}

	// Write output to file
	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE, 0666)
	if err != nil {
		return err
	}
	f.Write(buf)
	f.Close()
	return nil
}

// Helper function for Compiler object.
func Compile(pkgName, runtimePath, outpath, target string, printIR bool) error {
	var buildTags []string
	// TODO: put this somewhere else
	if target == "pca10040" {
		buildTags = append(buildTags, "nrf", "nrf52", "nrf52832")
		target = "armv7m-none-eabi"
	}

	c, err := NewCompiler(pkgName, target)
	if err != nil {
		return err
	}

	// Add C/LLVM runtime.
	runtime, err := llvm.ParseBitcodeFile(runtimePath)
	if err != nil {
		return err
	}
	err = c.LinkModule(runtime)
	if err != nil {
		return err
	}

	// Compile Go code to IR.
	parseErr := c.Parse(pkgName, buildTags)
	if printIR {
		fmt.Println(c.IR())
	}
	if parseErr != nil {
		return parseErr
	}

	c.ApplyFunctionSections() // -ffunction-sections

	if err := c.Verify(); err != nil {
		return err
	}
	//c.Optimize(2, 1) // -O2 -Os
	if err := c.Verify(); err != nil {
		return err
	}

	err = c.EmitObject(outpath)
	if err != nil {
		return err
	}

	return nil
}


func main() {
	outpath := flag.String("o", "", "output filename")
	printIR := flag.Bool("printir", false, "print LLVM IR after optimizing")
	runtime := flag.String("runtime", "", "runtime LLVM bitcode files (from C sources)")
	target := flag.String("target", llvm.DefaultTargetTriple(), "LLVM target")

	flag.Parse()

	if *outpath == "" || flag.NArg() != 1 {
		fmt.Fprintf(os.Stderr, "usage: %s [-printir] -runtime=<runtime.bc> [-target=<target>] -o <output> <input>", os.Args[0])
		flag.PrintDefaults()
		return
	}

	os.Setenv("CC", "clang -target=" + *target)

	err := Compile(flag.Args()[0], *runtime, *outpath, *target, *printIR)
	if err != nil {
		fmt.Fprintln(os.Stderr, "error:", err)
		os.Exit(1)
	}
}