package compiler

import (
	"errors"
	"fmt"
	"go/build"
	"go/constant"
	"go/token"
	"go/types"
	"os"
	"path/filepath"
	"runtime"
	"strconv"
	"strings"

	"github.com/aykevl/go-llvm"
	"github.com/aykevl/tinygo/ir"
	"go/parser"
	"golang.org/x/tools/go/loader"
	"golang.org/x/tools/go/ssa"
)

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

// Configure the compiler.
type Config struct {
	Triple    string   // LLVM target triple, e.g. x86_64-unknown-linux-gnu (empty string means default)
	DumpSSA   bool     // dump Go SSA, for compiler debugging
	Debug     bool     // add debug symbols for gdb
	RootDir   string   // GOROOT for TinyGo
	GOPATH    string   // GOPATH, like `go env GOPATH`
	BuildTags []string // build tags for TinyGo (empty means {runtime.GOOS/runtime.GOARCH})
}

type Compiler struct {
	Config
	mod             llvm.Module
	ctx             llvm.Context
	builder         llvm.Builder
	dibuilder       *llvm.DIBuilder
	cu              llvm.Metadata
	difiles         map[string]llvm.Metadata
	ditypes         map[string]llvm.Metadata
	machine         llvm.TargetMachine
	targetData      llvm.TargetData
	intType         llvm.Type
	i8ptrType       llvm.Type // for convenience
	uintptrType     llvm.Type
	lenType         llvm.Type
	coroIdFunc      llvm.Value
	coroSizeFunc    llvm.Value
	coroBeginFunc   llvm.Value
	coroSuspendFunc llvm.Value
	coroEndFunc     llvm.Value
	coroFreeFunc    llvm.Value
	initFuncs       []llvm.Value
	deferFuncs      []*ir.Function
	ir              *ir.Program
}

type Frame struct {
	fn           *ir.Function
	locals       map[ssa.Value]llvm.Value // local variables
	blocks       map[*ssa.BasicBlock]llvm.BasicBlock
	currentBlock *ssa.BasicBlock
	phis         []Phi
	blocking     bool
	taskHandle   llvm.Value
	cleanupBlock llvm.BasicBlock
	suspendBlock llvm.BasicBlock
	deferPtr     llvm.Value
	difunc       llvm.Metadata
}

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

func NewCompiler(pkgName string, config Config) (*Compiler, error) {
	if config.Triple == "" {
		config.Triple = llvm.DefaultTargetTriple()
	}
	if len(config.BuildTags) == 0 {
		config.BuildTags = []string{runtime.GOOS, runtime.GOARCH}
	}
	c := &Compiler{
		Config:  config,
		difiles: make(map[string]llvm.Metadata),
		ditypes: make(map[string]llvm.Metadata),
	}

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

	c.mod = llvm.NewModule(pkgName)
	c.mod.SetTarget(config.Triple)
	c.mod.SetDataLayout(c.targetData.String())
	c.ctx = c.mod.Context()
	c.builder = c.ctx.NewBuilder()
	c.dibuilder = llvm.NewDIBuilder(c.mod)

	// Depends on platform (32bit or 64bit), but fix it here for now.
	c.intType = llvm.Int32Type()
	c.uintptrType = c.targetData.IntPtrType()
	if c.targetData.PointerSize() < 4 {
		// 16 or 8 bits target with smaller length type
		c.lenType = c.uintptrType
	} else {
		c.lenType = llvm.Int32Type() // also defined as runtime.lenType
	}
	c.i8ptrType = llvm.PointerType(llvm.Int8Type(), 0)

	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
}

// Return the LLVM module. Only valid after a successful compile.
func (c *Compiler) Module() llvm.Module {
	return c.mod
}

// Compile the given package path or .go file path. Return an error when this
// fails (in any stage).
func (c *Compiler) Compile(mainPath string) error {
	tripleSplit := strings.Split(c.Triple, "-")

	// Prefix the GOPATH with the system GOROOT, as GOROOT is already set to
	// the TinyGo root.
	gopath := c.GOPATH
	if gopath == "" {
		gopath = runtime.GOROOT()
	} else {
		gopath = runtime.GOROOT() + string(filepath.ListSeparator) + gopath
	}

	config := loader.Config{
		TypeChecker: types.Config{
			Sizes: &StdSizes{
				IntSize:  int64(c.targetData.TypeAllocSize(c.intType)),
				PtrSize:  int64(c.targetData.PointerSize()),
				MaxAlign: int64(c.targetData.PrefTypeAlignment(c.i8ptrType)),
			},
		},
		Build: &build.Context{
			GOARCH:      tripleSplit[0],
			GOOS:        tripleSplit[2],
			GOROOT:      c.RootDir,
			GOPATH:      gopath,
			CgoEnabled:  true,
			UseAllFiles: false,
			Compiler:    "gc", // must be one of the recognized compilers
			BuildTags:   append([]string{"tgo"}, c.BuildTags...),
		},
		ParserMode: parser.ParseComments,
	}
	config.Import("runtime")
	if strings.HasSuffix(mainPath, ".go") {
		config.CreateFromFilenames("main", mainPath)
	} else {
		config.Import(mainPath)
	}
	lprogram, err := config.Load()
	if err != nil {
		return err
	}

	c.ir = ir.NewProgram(lprogram, mainPath)

	// Run some DCE and analysis passes. The results are later used by the
	// compiler.
	c.ir.SimpleDCE()                   // remove most dead code
	c.ir.AnalyseCallgraph()            // set up callgraph
	c.ir.AnalyseInterfaceConversions() // determine which types are converted to an interface
	c.ir.AnalyseFunctionPointers()     // determine which function pointer signatures need context
	c.ir.AnalyseBlockingRecursive()    // make all parents of blocking calls blocking (transitively)
	c.ir.AnalyseGoCalls()              // check whether we need a scheduler

	// Initialize debug information.
	c.cu = c.dibuilder.CreateCompileUnit(llvm.DICompileUnit{
		Language:  llvm.DW_LANG_Go,
		File:      mainPath,
		Dir:       "",
		Producer:  "TinyGo",
		Optimized: true,
	})

	var frames []*Frame

	// Declare all named struct types.
	for _, t := range c.ir.NamedTypes {
		if named, ok := t.Type.Type().(*types.Named); ok {
			if _, ok := named.Underlying().(*types.Struct); ok {
				t.LLVMType = c.ctx.StructCreateNamed(named.Obj().Pkg().Path() + "." + named.Obj().Name())
			}
		}
	}

	// Define all named struct types.
	for _, t := range c.ir.NamedTypes {
		if named, ok := t.Type.Type().(*types.Named); ok {
			if st, ok := named.Underlying().(*types.Struct); ok {
				llvmType, err := c.getLLVMType(st)
				if err != nil {
					return err
				}
				t.LLVMType.StructSetBody(llvmType.StructElementTypes(), false)
			}
		}
	}

	// Declare all globals. These will get an initializer when parsing "package
	// initializer" functions.
	for _, g := range c.ir.Globals {
		typ := g.Type().(*types.Pointer).Elem()
		llvmType, err := c.getLLVMType(typ)
		if err != nil {
			return err
		}
		global := c.mod.NamedGlobal(g.LinkName())
		if global.IsNil() {
			global = llvm.AddGlobal(c.mod, llvmType, g.LinkName())
		}
		g.LLVMGlobal = global
		if !g.IsExtern() {
			global.SetLinkage(llvm.InternalLinkage)
			initializer, err := getZeroValue(llvmType)
			if err != nil {
				return err
			}
			global.SetInitializer(initializer)
		}
	}

	// Declare all functions.
	for _, f := range c.ir.Functions {
		frame, err := c.parseFuncDecl(f)
		if err != nil {
			return err
		}
		frames = append(frames, frame)
	}

	// Find and interpret package initializers.
	for _, frame := range frames {
		if frame.fn.Synthetic == "package initializer" {
			c.initFuncs = append(c.initFuncs, frame.fn.LLVMFn)
			if len(frame.fn.Blocks) != 1 {
				panic("unexpected number of basic blocks in package initializer")
			}
			// Try to interpret as much as possible of the init() function.
			// Whenever it hits an instruction that it doesn't understand, it
			// bails out and leaves the rest to the compiler (so initialization
			// continues at runtime).
			// This should only happen when it hits a function call or the end
			// of the block, ideally.
			err := c.ir.Interpret(frame.fn.Blocks[0], c.DumpSSA)
			if err != nil {
				return err
			}
			err = c.parseFunc(frame)
			if err != nil {
				return err
			}
		}
	}

	// Set values for globals (after package initializer has been interpreted).
	for _, g := range c.ir.Globals {
		if g.Initializer() == nil {
			continue
		}
		err := c.parseGlobalInitializer(g)
		if err != nil {
			return err
		}
	}

	// Add definitions to declarations.
	for _, frame := range frames {
		if frame.fn.CName() != "" {
			continue
		}
		if frame.fn.Blocks == nil {
			continue // external function
		}
		var err error
		if frame.fn.Synthetic == "package initializer" {
			continue // already done
		} else {
			err = c.parseFunc(frame)
		}
		if err != nil {
			return err
		}
	}

	// Create deferred function wrappers.
	for _, fn := range c.deferFuncs {
		// This function gets a single parameter which is a pointer to a struct.
		// This struct starts with the values of runtime._defer, but after that
		// follow the real parameters.
		// The job of this wrapper is to extract these parameters and to call
		// the real function with them.
		llvmFn := c.mod.NamedFunction(fn.LinkName() + "$defer")
		entry := c.ctx.AddBasicBlock(llvmFn, "entry")
		c.builder.SetInsertPointAtEnd(entry)
		deferRawPtr := llvmFn.Param(0)

		// Get the real param type and cast to it.
		valueTypes := []llvm.Type{llvmFn.Type(), llvm.PointerType(c.mod.GetTypeByName("runtime._defer"), 0)}
		for _, param := range fn.Params {
			llvmType, err := c.getLLVMType(param.Type())
			if err != nil {
				return err
			}
			valueTypes = append(valueTypes, llvmType)
		}
		contextType := llvm.StructType(valueTypes, false)
		contextPtr := c.builder.CreateBitCast(deferRawPtr, llvm.PointerType(contextType, 0), "context")

		// Extract the params from the struct.
		forwardParams := []llvm.Value{}
		zero := llvm.ConstInt(llvm.Int32Type(), 0, false)
		for i := range fn.Params {
			gep := c.builder.CreateGEP(contextPtr, []llvm.Value{zero, llvm.ConstInt(llvm.Int32Type(), uint64(i+2), false)}, "gep")
			forwardParam := c.builder.CreateLoad(gep, "param")
			forwardParams = append(forwardParams, forwardParam)
		}

		// Call real function (of which this is a wrapper).
		c.createCall(fn.LLVMFn, forwardParams, "")
		c.builder.CreateRetVoid()
	}

	// After all packages are imported, add a synthetic initializer function
	// that calls the initializer of each package.
	initFn := c.ir.GetFunction(c.ir.Program.ImportedPackage("runtime").Members["initAll"].(*ssa.Function))
	initFn.LLVMFn.SetLinkage(llvm.InternalLinkage)
	difunc, err := c.attachDebugInfo(initFn)
	if err != nil {
		return err
	}
	pos := c.ir.Program.Fset.Position(initFn.Pos())
	c.builder.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), difunc, llvm.Metadata{})
	block := c.ctx.AddBasicBlock(initFn.LLVMFn, "entry")
	c.builder.SetInsertPointAtEnd(block)
	for _, fn := range c.initFuncs {
		c.builder.CreateCall(fn, nil, "")
	}
	c.builder.CreateRetVoid()

	mainWrapper := c.mod.NamedFunction("runtime.mainWrapper")
	block = c.ctx.AddBasicBlock(mainWrapper, "entry")
	c.builder.SetInsertPointAtEnd(block)
	realMain := c.mod.NamedFunction(c.ir.MainPkg().Pkg.Path() + ".main")
	if c.ir.NeedsScheduler() {
		coroutine := c.builder.CreateCall(realMain, []llvm.Value{llvm.ConstPointerNull(c.i8ptrType)}, "")
		scheduler := c.mod.NamedFunction("runtime.scheduler")
		c.builder.CreateCall(scheduler, []llvm.Value{coroutine}, "")
	} else {
		c.builder.CreateCall(realMain, nil, "")
	}
	c.builder.CreateRetVoid()

	// Initialize runtime type information, for interfaces.
	// See src/runtime/interface.go for more details.
	dynamicTypes := c.ir.AllDynamicTypes()
	numDynamicTypes := 0
	for _, meta := range dynamicTypes {
		numDynamicTypes += len(meta.Methods)
	}
	ranges := make([]llvm.Value, 0, len(dynamicTypes))
	funcPointers := make([]llvm.Value, 0, numDynamicTypes)
	signatures := make([]llvm.Value, 0, numDynamicTypes)
	startIndex := 0
	rangeType := c.mod.GetTypeByName("runtime.methodSetRange")
	for _, meta := range dynamicTypes {
		rangeValues := []llvm.Value{
			llvm.ConstInt(llvm.Int16Type(), uint64(startIndex), false),
			llvm.ConstInt(llvm.Int16Type(), uint64(len(meta.Methods)), false),
		}
		rangeValue := llvm.ConstNamedStruct(rangeType, rangeValues)
		ranges = append(ranges, rangeValue)
		methods := make([]*types.Selection, 0, len(meta.Methods))
		for _, method := range meta.Methods {
			methods = append(methods, method)
		}
		c.ir.SortMethods(methods)
		for _, method := range methods {
			f := c.ir.GetFunction(c.ir.Program.MethodValue(method))
			if f.LLVMFn.IsNil() {
				return errors.New("cannot find function: " + f.LinkName())
			}
			fn, err := c.wrapInterfaceInvoke(f)
			if err != nil {
				return err
			}
			fnPtr := llvm.ConstBitCast(fn, c.i8ptrType)
			funcPointers = append(funcPointers, fnPtr)
			signatureNum := c.ir.MethodNum(method.Obj().(*types.Func))
			signature := llvm.ConstInt(llvm.Int16Type(), uint64(signatureNum), false)
			signatures = append(signatures, signature)
		}
		startIndex += len(meta.Methods)
	}

	interfaceTypes := c.ir.AllInterfaces()
	interfaceIndex := make([]llvm.Value, len(interfaceTypes))
	interfaceLengths := make([]llvm.Value, len(interfaceTypes))
	interfaceMethods := make([]llvm.Value, 0)
	for i, itfType := range interfaceTypes {
		if itfType.Type.NumMethods() > 0xff {
			return errors.New("too many methods for interface " + itfType.Type.String())
		}
		interfaceIndex[i] = llvm.ConstInt(llvm.Int16Type(), uint64(i), false)
		interfaceLengths[i] = llvm.ConstInt(llvm.Int8Type(), uint64(itfType.Type.NumMethods()), false)
		funcs := make([]*types.Func, itfType.Type.NumMethods())
		for i := range funcs {
			funcs[i] = itfType.Type.Method(i)
		}
		c.ir.SortFuncs(funcs)
		for _, f := range funcs {
			id := llvm.ConstInt(llvm.Int16Type(), uint64(c.ir.MethodNum(f)), false)
			interfaceMethods = append(interfaceMethods, id)
		}
	}

	if len(ranges) >= 1<<16 {
		return errors.New("method call numbers do not fit in a 16-bit integer")
	}

	// Replace the pre-created arrays with the generated arrays.
	rangeArray := llvm.ConstArray(rangeType, ranges)
	rangeArrayNewGlobal := llvm.AddGlobal(c.mod, rangeArray.Type(), "runtime.methodSetRanges.tmp")
	rangeArrayNewGlobal.SetInitializer(rangeArray)
	rangeArrayNewGlobal.SetLinkage(llvm.InternalLinkage)
	rangeArrayOldGlobal := c.mod.NamedGlobal("runtime.methodSetRanges")
	rangeArrayOldGlobal.ReplaceAllUsesWith(llvm.ConstBitCast(rangeArrayNewGlobal, rangeArrayOldGlobal.Type()))
	rangeArrayOldGlobal.EraseFromParentAsGlobal()
	rangeArrayNewGlobal.SetName("runtime.methodSetRanges")
	funcArray := llvm.ConstArray(c.i8ptrType, funcPointers)
	funcArrayNewGlobal := llvm.AddGlobal(c.mod, funcArray.Type(), "runtime.methodSetFunctions.tmp")
	funcArrayNewGlobal.SetInitializer(funcArray)
	funcArrayNewGlobal.SetLinkage(llvm.InternalLinkage)
	funcArrayOldGlobal := c.mod.NamedGlobal("runtime.methodSetFunctions")
	funcArrayOldGlobal.ReplaceAllUsesWith(llvm.ConstBitCast(funcArrayNewGlobal, funcArrayOldGlobal.Type()))
	funcArrayOldGlobal.EraseFromParentAsGlobal()
	funcArrayNewGlobal.SetName("runtime.methodSetFunctions")
	signatureArray := llvm.ConstArray(llvm.Int16Type(), signatures)
	signatureArrayNewGlobal := llvm.AddGlobal(c.mod, signatureArray.Type(), "runtime.methodSetSignatures.tmp")
	signatureArrayNewGlobal.SetInitializer(signatureArray)
	signatureArrayNewGlobal.SetLinkage(llvm.InternalLinkage)
	signatureArrayOldGlobal := c.mod.NamedGlobal("runtime.methodSetSignatures")
	signatureArrayOldGlobal.ReplaceAllUsesWith(llvm.ConstBitCast(signatureArrayNewGlobal, signatureArrayOldGlobal.Type()))
	signatureArrayOldGlobal.EraseFromParentAsGlobal()
	signatureArrayNewGlobal.SetName("runtime.methodSetSignatures")
	interfaceIndexArray := llvm.ConstArray(llvm.Int16Type(), interfaceIndex)
	interfaceIndexArrayNewGlobal := llvm.AddGlobal(c.mod, interfaceIndexArray.Type(), "runtime.interfaceIndex.tmp")
	interfaceIndexArrayNewGlobal.SetInitializer(interfaceIndexArray)
	interfaceIndexArrayNewGlobal.SetLinkage(llvm.InternalLinkage)
	interfaceIndexArrayOldGlobal := c.mod.NamedGlobal("runtime.interfaceIndex")
	interfaceIndexArrayOldGlobal.ReplaceAllUsesWith(llvm.ConstBitCast(interfaceIndexArrayNewGlobal, interfaceIndexArrayOldGlobal.Type()))
	interfaceIndexArrayOldGlobal.EraseFromParentAsGlobal()
	interfaceIndexArrayNewGlobal.SetName("runtime.interfaceIndex")
	interfaceLengthsArray := llvm.ConstArray(llvm.Int8Type(), interfaceLengths)
	interfaceLengthsArrayNewGlobal := llvm.AddGlobal(c.mod, interfaceLengthsArray.Type(), "runtime.interfaceLengths.tmp")
	interfaceLengthsArrayNewGlobal.SetInitializer(interfaceLengthsArray)
	interfaceLengthsArrayNewGlobal.SetLinkage(llvm.InternalLinkage)
	interfaceLengthsArrayOldGlobal := c.mod.NamedGlobal("runtime.interfaceLengths")
	interfaceLengthsArrayOldGlobal.ReplaceAllUsesWith(llvm.ConstBitCast(interfaceLengthsArrayNewGlobal, interfaceLengthsArrayOldGlobal.Type()))
	interfaceLengthsArrayOldGlobal.EraseFromParentAsGlobal()
	interfaceLengthsArrayNewGlobal.SetName("runtime.interfaceLengths")
	interfaceMethodsArray := llvm.ConstArray(llvm.Int16Type(), interfaceMethods)
	interfaceMethodsArrayNewGlobal := llvm.AddGlobal(c.mod, interfaceMethodsArray.Type(), "runtime.interfaceMethods.tmp")
	interfaceMethodsArrayNewGlobal.SetInitializer(interfaceMethodsArray)
	interfaceMethodsArrayNewGlobal.SetLinkage(llvm.InternalLinkage)
	interfaceMethodsArrayOldGlobal := c.mod.NamedGlobal("runtime.interfaceMethods")
	interfaceMethodsArrayOldGlobal.ReplaceAllUsesWith(llvm.ConstBitCast(interfaceMethodsArrayNewGlobal, interfaceMethodsArrayOldGlobal.Type()))
	interfaceMethodsArrayOldGlobal.EraseFromParentAsGlobal()
	interfaceMethodsArrayNewGlobal.SetName("runtime.interfaceMethods")

	c.mod.NamedGlobal("runtime.firstTypeWithMethods").SetInitializer(llvm.ConstInt(llvm.Int16Type(), uint64(c.ir.FirstDynamicType()), false))

	// see: https://reviews.llvm.org/D18355
	c.mod.AddNamedMetadataOperand("llvm.module.flags",
		c.ctx.MDNode([]llvm.Metadata{
			llvm.ConstInt(llvm.Int32Type(), 1, false).ConstantAsMetadata(), // Error on mismatch
			llvm.GlobalContext().MDString("Debug Info Version"),
			llvm.ConstInt(llvm.Int32Type(), 3, false).ConstantAsMetadata(), // DWARF version
		}),
	)
	c.dibuilder.Finalize()

	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, types.UntypedBool:
			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.Float32:
			return llvm.FloatType(), nil
		case types.Float64:
			return llvm.DoubleType(), nil
		case types.Complex64:
			return llvm.VectorType(llvm.FloatType(), 2), nil
		case types.Complex128:
			return llvm.VectorType(llvm.DoubleType(), 2), nil
		case types.String, types.UntypedString:
			return c.mod.GetTypeByName("runtime._string"), 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: " + typ.String())
		}
	case *types.Chan:
		return llvm.PointerType(c.mod.GetTypeByName("runtime.channel"), 0), nil
	case *types.Interface:
		return c.mod.GetTypeByName("runtime._interface"), nil
	case *types.Map:
		return llvm.PointerType(c.mod.GetTypeByName("runtime.hashmap"), 0), nil
	case *types.Named:
		if _, ok := typ.Underlying().(*types.Struct); ok {
			llvmType := c.mod.GetTypeByName(typ.Obj().Pkg().Path() + "." + typ.Obj().Name())
			if llvmType.IsNil() {
				return llvm.Type{}, errors.New("type not found: " + typ.Obj().Pkg().Path() + "." + typ.Obj().Name())
			}
			return llvmType, nil
		}
		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 {
			// Multiple return values. Put them together in a struct.
			members := make([]llvm.Type, typ.Results().Len())
			for i := 0; i < typ.Results().Len(); i++ {
				returnType, err := c.getLLVMType(typ.Results().At(i).Type())
				if err != nil {
					return llvm.Type{}, err
				}
				members[i] = returnType
			}
			returnType = llvm.StructType(members, false)
		}
		// param values
		var paramTypes []llvm.Type
		if typ.Recv() != nil {
			recv, err := c.getLLVMType(typ.Recv().Type())
			if err != nil {
				return llvm.Type{}, err
			}
			if recv.StructName() == "runtime._interface" {
				recv = c.i8ptrType
			}
			paramTypes = append(paramTypes, c.expandFormalParamType(recv)...)
		}
		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, c.expandFormalParamType(subType)...)
		}
		var ptr llvm.Type
		if c.ir.SignatureNeedsContext(typ) {
			// make a closure type (with a function pointer type inside):
			// {context, funcptr}
			paramTypes = append(paramTypes, c.i8ptrType)
			ptr = llvm.PointerType(llvm.FunctionType(returnType, paramTypes, false), 0)
			ptr = c.ctx.StructType([]llvm.Type{c.i8ptrType, ptr}, false)
		} else {
			// make a simple function pointer
			ptr = llvm.PointerType(llvm.FunctionType(returnType, paramTypes, false), 0)
		}
		return ptr, nil
	case *types.Slice:
		elemType, err := c.getLLVMType(typ.Elem())
		if err != nil {
			return llvm.Type{}, err
		}
		members := []llvm.Type{
			llvm.PointerType(elemType, 0),
			c.lenType, // len
			c.lenType, // cap
		}
		return llvm.StructType(members, false), 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: " + goType.String())
	}
}

// Return a zero LLVM value for any LLVM type. Setting this value as an
// initializer has the same effect as setting 'zeroinitializer' on a value.
// Sadly, I haven't found a way to do it directly with the Go API but this works
// just fine.
func 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 := getZeroValue(subTyp)
			if err != nil {
				return llvm.Value{}, err
			}
			vals[i] = val
		}
		return llvm.ConstArray(subTyp, vals), nil
	case llvm.FloatTypeKind, llvm.DoubleTypeKind:
		return llvm.ConstFloat(typ, 0.0), 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 := getZeroValue(subTyp)
			if err != nil {
				return llvm.Value{}, err
			}
			vals[i] = val
		}
		if typ.StructName() != "" {
			return llvm.ConstNamedStruct(typ, vals), nil
		} else {
			return llvm.ConstStruct(vals, false), nil
		}
	default:
		return llvm.Value{}, errors.New("todo: LLVM zero initializer")
	}
}

// Is this a pointer type of some sort? Can be unsafe.Pointer or any *T pointer.
func 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
	}
}

// Get the DWARF type for this Go type.
func (c *Compiler) getDIType(typ types.Type) (llvm.Metadata, error) {
	name := typ.String()
	if dityp, ok := c.ditypes[name]; ok {
		return dityp, nil
	} else {
		llvmType, err := c.getLLVMType(typ)
		if err != nil {
			return llvm.Metadata{}, err
		}
		sizeInBytes := c.targetData.TypeAllocSize(llvmType)
		var encoding llvm.DwarfTypeEncoding
		switch typ := typ.(type) {
		case *types.Basic:
			if typ.Info()&types.IsBoolean != 0 {
				encoding = llvm.DW_ATE_boolean
			} else if typ.Info()&types.IsFloat != 0 {
				encoding = llvm.DW_ATE_float
			} else if typ.Info()&types.IsComplex != 0 {
				encoding = llvm.DW_ATE_complex_float
			} else if typ.Info()&types.IsUnsigned != 0 {
				encoding = llvm.DW_ATE_unsigned
			} else if typ.Info()&types.IsInteger != 0 {
				encoding = llvm.DW_ATE_signed
			} else if typ.Kind() == types.UnsafePointer {
				encoding = llvm.DW_ATE_address
			}
		case *types.Pointer:
			encoding = llvm.DW_ATE_address
		}
		// TODO: other types
		dityp = c.dibuilder.CreateBasicType(llvm.DIBasicType{
			Name:       name,
			SizeInBits: sizeInBytes * 8,
			Encoding:   encoding,
		})
		c.ditypes[name] = dityp
		return dityp, nil
	}
}

// Wrap an interface method function pointer. The wrapper takes in a pointer to
// the underlying value, dereferences it, and calls the real method. This
// wrapper is only needed when the interface value actually doesn't fit in a
// pointer and a pointer to the value must be created.
func (c *Compiler) wrapInterfaceInvoke(f *ir.Function) (llvm.Value, error) {
	receiverType, err := c.getLLVMType(f.Params[0].Type())
	if err != nil {
		return llvm.Value{}, err
	}
	expandedReceiverType := c.expandFormalParamType(receiverType)

	if c.targetData.TypeAllocSize(receiverType) <= c.targetData.TypeAllocSize(c.i8ptrType) && len(expandedReceiverType) == 1 {
		// nothing to wrap
		return f.LLVMFn, nil
	}

	// create wrapper function
	fnType := f.LLVMFn.Type().ElementType()
	paramTypes := append([]llvm.Type{c.i8ptrType}, fnType.ParamTypes()[len(expandedReceiverType):]...)
	wrapFnType := llvm.FunctionType(fnType.ReturnType(), paramTypes, false)
	wrapper := llvm.AddFunction(c.mod, f.LinkName()+"$invoke", wrapFnType)
	wrapper.SetLinkage(llvm.InternalLinkage)

	// add debug info
	pos := c.ir.Program.Fset.Position(f.Pos())
	difunc, err := c.attachDebugInfoRaw(f, wrapper, "$invoke", pos.Filename, pos.Line)
	if err != nil {
		return llvm.Value{}, err
	}
	c.builder.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), difunc, llvm.Metadata{})

	// set up IR builder
	block := c.ctx.AddBasicBlock(wrapper, "entry")
	c.builder.SetInsertPointAtEnd(block)

	var receiverPtr llvm.Value
	if c.targetData.TypeAllocSize(receiverType) > c.targetData.TypeAllocSize(c.i8ptrType) {
		// The receiver is passed in using a pointer. We have to load it here
		// and pass it by value to the real function.

		// Load the underlying value.
		receiverPtrType := llvm.PointerType(receiverType, 0)
		receiverPtr = c.builder.CreateBitCast(wrapper.Param(0), receiverPtrType, "receiver.ptr")
	} else if len(expandedReceiverType) != 1 {
		// The value is stored in the interface, but it is of type struct which
		// is expanded to multiple parameters (e.g. {i8, i8}). So we have to
		// receive the struct as parameter, expand it, and pass it on to the
		// real function.

		// Cast the passed-in i8* to the struct value (using an alloca) and
		// extract its values.
		alloca := c.builder.CreateAlloca(c.i8ptrType, "receiver.alloca")
		c.builder.CreateStore(wrapper.Param(0), alloca)
		receiverPtr = c.builder.CreateBitCast(alloca, llvm.PointerType(receiverType, 0), "receiver.ptr")
	} else {
		panic("unreachable")
	}

	receiverValue := c.builder.CreateLoad(receiverPtr, "receiver")
	params := append(c.expandFormalParam(receiverValue), wrapper.Params()[1:]...)
	if fnType.ReturnType().TypeKind() == llvm.VoidTypeKind {
		c.builder.CreateCall(f.LLVMFn, params, "")
		c.builder.CreateRetVoid()
	} else {
		ret := c.builder.CreateCall(f.LLVMFn, params, "ret")
		c.builder.CreateRet(ret)
	}

	return wrapper, nil
}

func (c *Compiler) parseFuncDecl(f *ir.Function) (*Frame, error) {
	frame := &Frame{
		fn:       f,
		locals:   make(map[ssa.Value]llvm.Value),
		blocks:   make(map[*ssa.BasicBlock]llvm.BasicBlock),
		blocking: c.ir.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 {
		results := make([]llvm.Type, 0, f.Signature.Results().Len())
		for i := 0; i < f.Signature.Results().Len(); i++ {
			typ, err := c.getLLVMType(f.Signature.Results().At(i).Type())
			if err != nil {
				return nil, err
			}
			results = append(results, typ)
		}
		retType = llvm.StructType(results, false)
	}

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

	if c.ir.FunctionNeedsContext(f) {
		// This function gets an extra parameter: the context pointer (for
		// closures and bound methods). Add it as an extra paramter here.
		paramTypes = append(paramTypes, c.i8ptrType)
	}

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

	name := f.LinkName()
	frame.fn.LLVMFn = c.mod.NamedFunction(name)
	if frame.fn.LLVMFn.IsNil() {
		frame.fn.LLVMFn = llvm.AddFunction(c.mod, name, fnType)
	}

	if c.Debug && f.Synthetic == "package initializer" {
		difunc, err := c.attachDebugInfoRaw(f, f.LLVMFn, "", "", 0)
		if err != nil {
			return nil, err
		}
		frame.difunc = difunc
	} else if c.Debug && f.Syntax() != nil && len(f.Blocks) != 0 {
		// Create debug info file if needed.
		difunc, err := c.attachDebugInfo(f)
		if err != nil {
			return nil, err
		}
		frame.difunc = difunc
	}

	return frame, nil
}

func (c *Compiler) attachDebugInfo(f *ir.Function) (llvm.Metadata, error) {
	pos := c.ir.Program.Fset.Position(f.Syntax().Pos())
	return c.attachDebugInfoRaw(f, f.LLVMFn, "", pos.Filename, pos.Line)
}

func (c *Compiler) attachDebugInfoRaw(f *ir.Function, llvmFn llvm.Value, suffix, filename string, line int) (llvm.Metadata, error) {
	if _, ok := c.difiles[filename]; !ok {
		dir, file := filepath.Split(filename)
		if dir != "" {
			dir = dir[:len(dir)-1]
		}
		c.difiles[filename] = c.dibuilder.CreateFile(file, dir)
	}

	// Debug info for this function.
	diparams := make([]llvm.Metadata, 0, len(f.Params))
	for _, param := range f.Params {
		ditype, err := c.getDIType(param.Type())
		if err != nil {
			return llvm.Metadata{}, err
		}
		diparams = append(diparams, ditype)
	}
	diFuncType := c.dibuilder.CreateSubroutineType(llvm.DISubroutineType{
		File:       c.difiles[filename],
		Parameters: diparams,
		Flags:      0, // ?
	})
	difunc := c.dibuilder.CreateFunction(c.difiles[filename], llvm.DIFunction{
		Name:         f.RelString(nil) + suffix,
		LinkageName:  f.LinkName() + suffix,
		File:         c.difiles[filename],
		Line:         line,
		Type:         diFuncType,
		LocalToUnit:  true,
		IsDefinition: true,
		ScopeLine:    0,
		Flags:        llvm.FlagPrototyped,
		Optimized:    true,
	})
	llvmFn.SetSubprogram(difunc)
	return difunc, nil
}

// Create a new global hashmap bucket, for map initialization.
func (c *Compiler) initMapNewBucket(prefix string, mapType *types.Map) (llvm.Value, uint64, uint64, error) {
	llvmKeyType, err := c.getLLVMType(mapType.Key().Underlying())
	if err != nil {
		return llvm.Value{}, 0, 0, err
	}
	llvmValueType, err := c.getLLVMType(mapType.Elem().Underlying())
	if err != nil {
		return llvm.Value{}, 0, 0, err
	}
	keySize := c.targetData.TypeAllocSize(llvmKeyType)
	valueSize := c.targetData.TypeAllocSize(llvmValueType)
	bucketType := llvm.StructType([]llvm.Type{
		llvm.ArrayType(llvm.Int8Type(), 8), // tophash
		c.i8ptrType,                        // next bucket
		llvm.ArrayType(llvmKeyType, 8),     // key type
		llvm.ArrayType(llvmValueType, 8),   // value type
	}, false)
	bucketValue, err := getZeroValue(bucketType)
	if err != nil {
		return llvm.Value{}, 0, 0, err
	}
	bucket := llvm.AddGlobal(c.mod, bucketType, prefix+"$hashmap$bucket")
	bucket.SetInitializer(bucketValue)
	bucket.SetLinkage(llvm.InternalLinkage)
	return bucket, keySize, valueSize, nil
}

func (c *Compiler) parseGlobalInitializer(g *ir.Global) error {
	if g.IsExtern() {
		return nil
	}
	llvmValue, err := c.getInterpretedValue(g.LinkName(), g.Initializer())
	if err != nil {
		return err
	}
	g.LLVMGlobal.SetInitializer(llvmValue)
	return nil
}

// Turn a computed Value type (ConstValue, ArrayValue, etc.) into a LLVM value.
// This is used to set the initializer of globals after they have been
// calculated by the package initializer interpreter.
func (c *Compiler) getInterpretedValue(prefix string, value ir.Value) (llvm.Value, error) {
	switch value := value.(type) {
	case *ir.ArrayValue:
		vals := make([]llvm.Value, len(value.Elems))
		for i, elem := range value.Elems {
			val, err := c.getInterpretedValue(prefix+"$arrayval", elem)
			if err != nil {
				return llvm.Value{}, err
			}
			vals[i] = val
		}
		subTyp, err := c.getLLVMType(value.ElemType)
		if err != nil {
			return llvm.Value{}, err
		}
		return llvm.ConstArray(subTyp, vals), nil

	case *ir.ConstValue:
		return c.parseConst(prefix, value.Expr)

	case *ir.FunctionValue:
		if value.Elem == nil {
			llvmType, err := c.getLLVMType(value.Type)
			if err != nil {
				return llvm.Value{}, err
			}
			return getZeroValue(llvmType)
		}
		fn := c.ir.GetFunction(value.Elem)
		ptr := fn.LLVMFn
		if c.ir.SignatureNeedsContext(fn.Signature) {
			// Create closure value: {context, function pointer}
			ptr = llvm.ConstStruct([]llvm.Value{llvm.ConstPointerNull(c.i8ptrType), ptr}, false)
		}
		return ptr, nil

	case *ir.GlobalValue:
		zero := llvm.ConstInt(llvm.Int32Type(), 0, false)
		ptr := llvm.ConstInBoundsGEP(value.Global.LLVMGlobal, []llvm.Value{zero})
		return ptr, nil

	case *ir.InterfaceValue:
		underlying := llvm.ConstPointerNull(c.i8ptrType) // could be any 0 value
		if value.Elem != nil {
			elem, err := c.getInterpretedValue(prefix, value.Elem)
			if err != nil {
				return llvm.Value{}, err
			}
			underlying = elem
		}
		return c.parseMakeInterface(underlying, value.Type, prefix)

	case *ir.MapValue:
		// Create initial bucket.
		firstBucketGlobal, keySize, valueSize, err := c.initMapNewBucket(prefix, value.Type)
		if err != nil {
			return llvm.Value{}, err
		}

		// Insert each key/value pair in the hashmap.
		bucketGlobal := firstBucketGlobal
		for i, key := range value.Keys {
			llvmKey, err := c.getInterpretedValue(prefix, key)
			if err != nil {
				return llvm.Value{}, nil
			}
			llvmValue, err := c.getInterpretedValue(prefix, value.Values[i])
			if err != nil {
				return llvm.Value{}, nil
			}

			constVal := key.(*ir.ConstValue).Expr
			var keyBuf []byte
			switch constVal.Type().Underlying().(*types.Basic).Kind() {
			case types.String:
				keyBuf = []byte(constant.StringVal(constVal.Value))
			case types.Int:
				keyBuf = make([]byte, c.targetData.TypeAllocSize(c.intType))
				n, _ := constant.Uint64Val(constVal.Value)
				for i := range keyBuf {
					keyBuf[i] = byte(n)
					n >>= 8
				}
			default:
				return llvm.Value{}, errors.New("todo: init: map key not implemented: " + constVal.Type().Underlying().String())
			}
			hash := hashmapHash(keyBuf)

			if i%8 == 0 && i != 0 {
				// Bucket is full, create a new one.
				newBucketGlobal, _, _, err := c.initMapNewBucket(prefix, value.Type)
				if err != nil {
					return llvm.Value{}, err
				}
				zero := llvm.ConstInt(llvm.Int32Type(), 0, false)
				newBucketPtr := llvm.ConstInBoundsGEP(newBucketGlobal, []llvm.Value{zero})
				newBucketPtrCast := llvm.ConstBitCast(newBucketPtr, c.i8ptrType)
				// insert pointer into old bucket
				bucket := bucketGlobal.Initializer()
				bucket = llvm.ConstInsertValue(bucket, newBucketPtrCast, []uint32{1})
				bucketGlobal.SetInitializer(bucket)
				// switch to next bucket
				bucketGlobal = newBucketGlobal
			}

			tophashValue := llvm.ConstInt(llvm.Int8Type(), uint64(hashmapTopHash(hash)), false)
			bucket := bucketGlobal.Initializer()
			bucket = llvm.ConstInsertValue(bucket, tophashValue, []uint32{0, uint32(i % 8)})
			bucket = llvm.ConstInsertValue(bucket, llvmKey, []uint32{2, uint32(i % 8)})
			bucket = llvm.ConstInsertValue(bucket, llvmValue, []uint32{3, uint32(i % 8)})
			bucketGlobal.SetInitializer(bucket)
		}

		// Create the hashmap itself.
		zero := llvm.ConstInt(llvm.Int32Type(), 0, false)
		bucketPtr := llvm.ConstInBoundsGEP(bucketGlobal, []llvm.Value{zero})
		hashmapType := c.mod.GetTypeByName("runtime.hashmap")
		hashmap := llvm.ConstNamedStruct(hashmapType, []llvm.Value{
			llvm.ConstPointerNull(llvm.PointerType(hashmapType, 0)),  // next
			llvm.ConstBitCast(bucketPtr, c.i8ptrType),                // buckets
			llvm.ConstInt(c.lenType, uint64(len(value.Keys)), false), // count
			llvm.ConstInt(llvm.Int8Type(), keySize, false),           // keySize
			llvm.ConstInt(llvm.Int8Type(), valueSize, false),         // valueSize
			llvm.ConstInt(llvm.Int8Type(), 0, false),                 // bucketBits
		})

		// Create a pointer to this hashmap.
		hashmapPtr := llvm.AddGlobal(c.mod, hashmap.Type(), prefix+"$hashmap")
		hashmapPtr.SetInitializer(hashmap)
		hashmapPtr.SetLinkage(llvm.InternalLinkage)
		return llvm.ConstInBoundsGEP(hashmapPtr, []llvm.Value{zero}), nil

	case *ir.PointerBitCastValue:
		elem, err := c.getInterpretedValue(prefix, value.Elem)
		if err != nil {
			return llvm.Value{}, err
		}
		llvmType, err := c.getLLVMType(value.Type)
		if err != nil {
			return llvm.Value{}, err
		}
		return llvm.ConstBitCast(elem, llvmType), nil

	case *ir.PointerToUintptrValue:
		elem, err := c.getInterpretedValue(prefix, value.Elem)
		if err != nil {
			return llvm.Value{}, err
		}
		return llvm.ConstPtrToInt(elem, c.uintptrType), nil

	case *ir.PointerValue:
		if value.Elem == nil {
			typ, err := c.getLLVMType(value.Type)
			if err != nil {
				return llvm.Value{}, err
			}
			return llvm.ConstPointerNull(typ), nil
		}
		elem, err := c.getInterpretedValue(prefix, *value.Elem)
		if err != nil {
			return llvm.Value{}, err
		}

		obj := llvm.AddGlobal(c.mod, elem.Type(), prefix+"$ptrvalue")
		obj.SetInitializer(elem)
		obj.SetLinkage(llvm.InternalLinkage)
		elem = obj

		zero := llvm.ConstInt(llvm.Int32Type(), 0, false)
		ptr := llvm.ConstInBoundsGEP(elem, []llvm.Value{zero})
		return ptr, nil

	case *ir.SliceValue:
		var globalPtr llvm.Value
		var arrayLength uint64
		if value.Array == nil {
			arrayType, err := c.getLLVMType(value.Type.Elem())
			if err != nil {
				return llvm.Value{}, err
			}
			globalPtr = llvm.ConstPointerNull(llvm.PointerType(arrayType, 0))
		} else {
			// make array
			array, err := c.getInterpretedValue(prefix, value.Array)
			if err != nil {
				return llvm.Value{}, err
			}
			// make global from array
			global := llvm.AddGlobal(c.mod, array.Type(), prefix+"$array")
			global.SetInitializer(array)
			global.SetLinkage(llvm.InternalLinkage)

			// get pointer to global
			zero := llvm.ConstInt(llvm.Int32Type(), 0, false)
			globalPtr = c.builder.CreateInBoundsGEP(global, []llvm.Value{zero, zero}, "")

			arrayLength = uint64(len(value.Array.Elems))
		}

		// make slice
		sliceTyp, err := c.getLLVMType(value.Type)
		if err != nil {
			return llvm.Value{}, err
		}
		llvmLen := llvm.ConstInt(c.lenType, arrayLength, false)
		slice := llvm.ConstNamedStruct(sliceTyp, []llvm.Value{
			globalPtr, // ptr
			llvmLen,   // len
			llvmLen,   // cap
		})
		return slice, nil

	case *ir.StructValue:
		fields := make([]llvm.Value, len(value.Fields))
		for i, elem := range value.Fields {
			field, err := c.getInterpretedValue(prefix, elem)
			if err != nil {
				return llvm.Value{}, err
			}
			fields[i] = field
		}
		switch value.Type.(type) {
		case *types.Named:
			llvmType, err := c.getLLVMType(value.Type)
			if err != nil {
				return llvm.Value{}, err
			}
			return llvm.ConstNamedStruct(llvmType, fields), nil
		case *types.Struct:
			return llvm.ConstStruct(fields, false), nil
		default:
			return llvm.Value{}, errors.New("init: unknown struct type: " + value.Type.String())
		}

	case *ir.ZeroBasicValue:
		llvmType, err := c.getLLVMType(value.Type)
		if err != nil {
			return llvm.Value{}, err
		}
		return getZeroValue(llvmType)

	default:
		return llvm.Value{}, errors.New("init: unknown initializer type: " + fmt.Sprintf("%#v", value))
	}
}

func (c *Compiler) parseFunc(frame *Frame) error {
	if c.DumpSSA {
		fmt.Printf("\nfunc %s:\n", frame.fn.Function)
	}
	if !frame.fn.IsExported() {
		frame.fn.LLVMFn.SetLinkage(llvm.InternalLinkage)
	}
	if frame.fn.IsInterrupt() && strings.HasPrefix(c.Triple, "avr") {
		frame.fn.LLVMFn.SetFunctionCallConv(85) // CallingConv::AVR_SIGNAL
	}

	if c.Debug {
		pos := c.ir.Program.Fset.Position(frame.fn.Pos())
		c.builder.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), frame.difunc, llvm.Metadata{})
	}

	// Pre-create all basic blocks in the function.
	for _, block := range frame.fn.DomPreorder() {
		llvmBlock := c.ctx.AddBasicBlock(frame.fn.LLVMFn, block.Comment)
		frame.blocks[block] = llvmBlock
	}
	if frame.blocking {
		frame.cleanupBlock = c.ctx.AddBasicBlock(frame.fn.LLVMFn, "task.cleanup")
		frame.suspendBlock = c.ctx.AddBasicBlock(frame.fn.LLVMFn, "task.suspend")
	}
	entryBlock := frame.blocks[frame.fn.Blocks[0]]
	c.builder.SetInsertPointAtEnd(entryBlock)

	// Load function parameters
	llvmParamIndex := 0
	for i, param := range frame.fn.Params {
		llvmType, err := c.getLLVMType(param.Type())
		if err != nil {
			return err
		}
		fields := make([]llvm.Value, 0, 1)
		for range c.expandFormalParamType(llvmType) {
			fields = append(fields, frame.fn.LLVMFn.Param(llvmParamIndex))
			llvmParamIndex++
		}
		frame.locals[param] = c.collapseFormalParam(llvmType, fields)

		// Add debug information to this parameter (if available)
		if c.Debug && frame.fn.Syntax() != nil {
			pos := c.ir.Program.Fset.Position(frame.fn.Syntax().Pos())
			dityp, err := c.getDIType(param.Type())
			if err != nil {
				return err
			}
			c.dibuilder.CreateParameterVariable(frame.difunc, llvm.DIParameterVariable{
				Name:           param.Name(),
				File:           c.difiles[pos.Filename],
				Line:           pos.Line,
				Type:           dityp,
				AlwaysPreserve: true,
				ArgNo:          i + 1,
			})
			// TODO: set the value of this parameter.
		}
	}

	// Load free variables from the context. This is a closure (or bound
	// method).
	if len(frame.fn.FreeVars) != 0 {
		if !c.ir.FunctionNeedsContext(frame.fn) {
			panic("free variables on function without context")
		}
		context := frame.fn.LLVMFn.LastParam()

		// Determine the context type. It's a struct containing all variables.
		freeVarTypes := make([]llvm.Type, 0, len(frame.fn.FreeVars))
		for _, freeVar := range frame.fn.FreeVars {
			typ, err := c.getLLVMType(freeVar.Type())
			if err != nil {
				return err
			}
			freeVarTypes = append(freeVarTypes, typ)
		}
		contextType := llvm.StructType(freeVarTypes, false)

		// Get a correctly-typed pointer to the context.
		contextAlloc := llvm.Value{}
		if c.targetData.TypeAllocSize(contextType) <= c.targetData.TypeAllocSize(c.i8ptrType) {
			// Context stored directly in pointer. Load it using an alloca.
			contextRawAlloc := c.builder.CreateAlloca(llvm.PointerType(c.i8ptrType, 0), "")
			contextRawValue := c.builder.CreateBitCast(context, llvm.PointerType(c.i8ptrType, 0), "")
			c.builder.CreateStore(contextRawValue, contextRawAlloc)
			contextAlloc = c.builder.CreateBitCast(contextRawAlloc, llvm.PointerType(contextType, 0), "")
		} else {
			// Context stored in the heap. Bitcast the passed-in pointer to the
			// correct pointer type.
			contextAlloc = c.builder.CreateBitCast(context, llvm.PointerType(contextType, 0), "")
		}

		// Load each free variable from the context.
		// A free variable is always a pointer when this is a closure, but it
		// can be another type when it is a wrapper for a bound method (these
		// wrappers are generated by the ssa package).
		for i, freeVar := range frame.fn.FreeVars {
			indices := []llvm.Value{
				llvm.ConstInt(llvm.Int32Type(), 0, false),
				llvm.ConstInt(llvm.Int32Type(), uint64(i), false),
			}
			gep := c.builder.CreateInBoundsGEP(contextAlloc, indices, "")
			frame.locals[freeVar] = c.builder.CreateLoad(gep, "")
		}
	}

	if frame.fn.Recover != nil {
		// Create defer list pointer.
		deferType := llvm.PointerType(c.mod.GetTypeByName("runtime._defer"), 0)
		frame.deferPtr = c.builder.CreateAlloca(deferType, "deferPtr")
		c.builder.CreateStore(llvm.ConstPointerNull(deferType), frame.deferPtr)
	}

	if frame.blocking {
		// Coroutine initialization.
		taskState := c.builder.CreateAlloca(c.mod.GetTypeByName("runtime.taskState"), "task.state")
		stateI8 := c.builder.CreateBitCast(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.createRuntimeCall("alloc", []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.createRuntimeCall("free", []llvm.Value{mem}, "")
		// re-insert parent coroutine
		c.createRuntimeCall("yieldToScheduler", []llvm.Value{frame.fn.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 frame.fn.DomPreorder() {
		if c.DumpSSA {
			fmt.Printf("%s:\n", block.Comment)
		}
		c.builder.SetInsertPointAtEnd(frame.blocks[block])
		frame.currentBlock = block
		for _, instr := range block.Instrs {
			if _, ok := instr.(*ssa.DebugRef); ok {
				continue
			}
			if c.DumpSSA {
				if val, ok := instr.(ssa.Value); ok && val.Name() != "" {
					fmt.Printf("\t%s = %s\n", val.Name(), val.String())
				} else {
					fmt.Printf("\t%s\n", instr.String())
				}
			}
			err := c.parseInstr(frame, instr)
			if err != nil {
				return err
			}
		}
		if frame.fn.Name() == "init" && len(block.Instrs) == 0 {
			c.builder.CreateRetVoid()
		}
	}

	// 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 {
	if c.Debug {
		pos := c.ir.Program.Fset.Position(instr.Pos())
		c.builder.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), frame.difunc, llvm.Metadata{})
	}

	switch instr := instr.(type) {
	case ssa.Value:
		value, err := c.parseExpr(frame, instr)
		if err == ir.ErrCGoWrapper {
			// Ignore CGo global variables which we don't use.
			return nil
		}
		frame.locals[instr] = value
		return err
	case *ssa.DebugRef:
		return nil // ignore
	case *ssa.Defer:
		if _, ok := instr.Call.Value.(*ssa.Function); !ok || instr.Call.IsInvoke() {
			return errors.New("todo: non-direct function calls in defer")
		}
		fn := c.ir.GetFunction(instr.Call.Value.(*ssa.Function))

		// The pointer to the previous defer struct, which we will replace to
		// make a linked list.
		next := c.builder.CreateLoad(frame.deferPtr, "defer.next")

		// Try to find the wrapper $defer function.
		deferName := fn.LinkName() + "$defer"
		callback := c.mod.NamedFunction(deferName)
		if callback.IsNil() {
			// Not found, have to add it.
			deferFuncType := llvm.FunctionType(llvm.VoidType(), []llvm.Type{next.Type()}, false)
			callback = llvm.AddFunction(c.mod, deferName, deferFuncType)
			c.deferFuncs = append(c.deferFuncs, fn)
		}

		// Collect all values to be put in the struct (starting with
		// runtime._defer fields).
		values := []llvm.Value{callback, next}
		valueTypes := []llvm.Type{callback.Type(), next.Type()}
		for _, param := range instr.Call.Args {
			llvmParam, err := c.parseExpr(frame, param)
			if err != nil {
				return err
			}
			values = append(values, llvmParam)
			valueTypes = append(valueTypes, llvmParam.Type())
		}

		// Make a struct out of it.
		contextType := llvm.StructType(valueTypes, false)
		context, err := getZeroValue(contextType)
		if err != nil {
			return err
		}
		for i, value := range values {
			context = c.builder.CreateInsertValue(context, value, i, "")
		}

		// Put this struct in an alloca.
		alloca := c.builder.CreateAlloca(contextType, "defer.alloca")
		c.builder.CreateStore(context, alloca)

		// Push it on top of the linked list by replacing deferPtr.
		allocaCast := c.builder.CreateBitCast(alloca, next.Type(), "defer.alloca.cast")
		c.builder.CreateStore(allocaCast, frame.deferPtr)
		return nil

	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.ir.IsBlocking(c.ir.GetFunction(instr.Common().Value.(*ssa.Function))) {
			_, 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.createRuntimeCall("yieldToScheduler", []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.MapUpdate:
		m, err := c.parseExpr(frame, instr.Map)
		if err != nil {
			return err
		}
		key, err := c.parseExpr(frame, instr.Key)
		if err != nil {
			return err
		}
		value, err := c.parseExpr(frame, instr.Value)
		if err != nil {
			return err
		}
		mapType := instr.Map.Type().Underlying().(*types.Map)
		switch keyType := mapType.Key().Underlying().(type) {
		case *types.Basic:
			valueAlloca := c.builder.CreateAlloca(value.Type(), "hashmap.value")
			c.builder.CreateStore(value, valueAlloca)
			valuePtr := c.builder.CreateBitCast(valueAlloca, c.i8ptrType, "hashmap.valueptr")
			if keyType.Info()&types.IsString != 0 {
				params := []llvm.Value{m, key, valuePtr}
				c.createRuntimeCall("hashmapStringSet", params, "")
				return nil
			} else if keyType.Info()&(types.IsBoolean|types.IsInteger) != 0 {
				keyAlloca := c.builder.CreateAlloca(key.Type(), "hashmap.key")
				c.builder.CreateStore(key, keyAlloca)
				keyPtr := c.builder.CreateBitCast(keyAlloca, c.i8ptrType, "hashmap.keyptr")
				params := []llvm.Value{m, keyPtr, valuePtr}
				c.createRuntimeCall("hashmapBinarySet", params, "")
				return nil
			} else {
				return errors.New("todo: map update key type: " + keyType.String())
			}
		default:
			return errors.New("todo: map update key type: " + keyType.String())
		}
	case *ssa.Panic:
		value, err := c.parseExpr(frame, instr.X)
		if err != nil {
			return err
		}
		c.createRuntimeCall("_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 {
				// Multiple return values. Put them all in a struct.
				retVal, err := getZeroValue(frame.fn.LLVMFn.Type().ElementType().ReturnType())
				if err != nil {
					return err
				}
				for i, result := range instr.Results {
					val, err := c.parseExpr(frame, result)
					if err != nil {
						return err
					}
					retVal = c.builder.CreateInsertValue(retVal, val, i, "")
				}
				c.builder.CreateRet(retVal)
				return nil
			}
		}
	case *ssa.RunDefers:
		deferData := c.builder.CreateLoad(frame.deferPtr, "")
		c.createRuntimeCall("rundefers", []llvm.Value{deferData}, "")
		return nil
	case *ssa.Store:
		llvmAddr, err := c.parseExpr(frame, instr.Addr)
		if err == ir.ErrCGoWrapper {
			// Ignore CGo global variables which we don't use.
			return nil
		}
		if err != nil {
			return err
		}
		llvmVal, err := c.parseExpr(frame, instr.Val)
		if err != nil {
			return err
		}
		store := c.builder.CreateStore(llvmVal, llvmAddr)
		valType := instr.Addr.Type().(*types.Pointer).Elem()
		if c.ir.IsVolatile(valType) {
			// Volatile store, for memory-mapped registers.
			store.SetVolatile(true)
		}
		return nil
	default:
		return errors.New("unknown instruction: " + instr.String())
	}
}

func (c *Compiler) parseBuiltin(frame *Frame, args []ssa.Value, callName string) (llvm.Value, error) {
	switch callName {
	case "cap":
		value, err := c.parseExpr(frame, args[0])
		if err != nil {
			return llvm.Value{}, err
		}
		switch args[0].Type().(type) {
		case *types.Slice:
			return c.builder.CreateExtractValue(value, 2, "cap"), nil
		default:
			return llvm.Value{}, errors.New("todo: cap: unknown type")
		}
	case "copy":
		dst, err := c.parseExpr(frame, args[0])
		if err != nil {
			return llvm.Value{}, err
		}
		src, err := c.parseExpr(frame, args[1])
		if err != nil {
			return llvm.Value{}, err
		}
		dstLen := c.builder.CreateExtractValue(dst, 1, "copy.dstLen")
		srcLen := c.builder.CreateExtractValue(src, 1, "copy.srcLen")
		dstBuf := c.builder.CreateExtractValue(dst, 0, "copy.dstArray")
		srcBuf := c.builder.CreateExtractValue(src, 0, "copy.srcArray")
		elemType := dstBuf.Type().ElementType()
		dstBuf = c.builder.CreateBitCast(dstBuf, c.i8ptrType, "copy.dstPtr")
		srcBuf = c.builder.CreateBitCast(srcBuf, c.i8ptrType, "copy.srcPtr")
		elemSize := llvm.ConstInt(c.uintptrType, c.targetData.TypeAllocSize(elemType), false)
		return c.createRuntimeCall("sliceCopy", []llvm.Value{dstBuf, srcBuf, dstLen, srcLen, elemSize}, "copy.n"), nil
	case "len":
		value, err := c.parseExpr(frame, args[0])
		if err != nil {
			return llvm.Value{}, err
		}
		var llvmLen llvm.Value
		switch args[0].Type().(type) {
		case *types.Basic, *types.Slice:
			// string or slice
			llvmLen = c.builder.CreateExtractValue(value, 1, "len")
		case *types.Map:
			indices := []llvm.Value{
				llvm.ConstInt(llvm.Int32Type(), 0, false),
				llvm.ConstInt(llvm.Int32Type(), 2, false), // hashmap.count
			}
			ptr := c.builder.CreateGEP(value, indices, "lenptr")
			llvmLen = c.builder.CreateLoad(ptr, "len")
		default:
			return llvm.Value{}, errors.New("todo: len: unknown type")
		}
		if c.targetData.TypeAllocSize(llvmLen.Type()) < c.targetData.TypeAllocSize(c.intType) {
			llvmLen = c.builder.CreateZExt(llvmLen, c.intType, "len.int")
		}
		return llvmLen, nil
	case "print", "println":
		for i, arg := range args {
			if i >= 1 && callName == "println" {
				c.createRuntimeCall("printspace", nil, "")
			}
			value, err := c.parseExpr(frame, arg)
			if err != nil {
				return llvm.Value{}, err
			}
			typ := arg.Type().Underlying()
			switch typ := typ.(type) {
			case *types.Basic:
				switch typ.Kind() {
				case types.String:
					c.createRuntimeCall("printstring", []llvm.Value{value}, "")
				case types.Uintptr:
					c.createRuntimeCall("printptr", []llvm.Value{value}, "")
				case types.UnsafePointer:
					ptrValue := c.builder.CreatePtrToInt(value, c.uintptrType, "")
					c.createRuntimeCall("printptr", []llvm.Value{ptrValue}, "")
				default:
					// runtime.print{int,uint}{8,16,32,64}
					if typ.Info()&types.IsInteger != 0 {
						name := "print"
						if typ.Info()&types.IsUnsigned != 0 {
							name += "uint"
						} else {
							name += "int"
						}
						name += strconv.FormatUint(c.targetData.TypeAllocSize(value.Type())*8, 10)
						c.createRuntimeCall(name, []llvm.Value{value}, "")
					} else if typ.Kind() == types.Bool {
						c.createRuntimeCall("printbool", []llvm.Value{value}, "")
					} else if typ.Kind() == types.Float32 {
						c.createRuntimeCall("printfloat32", []llvm.Value{value}, "")
					} else if typ.Kind() == types.Float64 {
						c.createRuntimeCall("printfloat64", []llvm.Value{value}, "")
					} else {
						return llvm.Value{}, errors.New("unknown basic arg type: " + typ.String())
					}
				}
			case *types.Interface:
				c.createRuntimeCall("printitf", []llvm.Value{value}, "")
			case *types.Map:
				c.createRuntimeCall("printmap", []llvm.Value{value}, "")
			case *types.Pointer:
				ptrValue := c.builder.CreatePtrToInt(value, c.uintptrType, "")
				c.createRuntimeCall("printptr", []llvm.Value{ptrValue}, "")
			default:
				return llvm.Value{}, errors.New("unknown arg type: " + typ.String())
			}
		}
		if callName == "println" {
			c.createRuntimeCall("printnl", nil, "")
		}
		return llvm.Value{}, nil // print() or println() returns void
	case "ssa:wrapnilchk":
		// TODO: do an actual nil check?
		return c.parseExpr(frame, args[0])
	default:
		return llvm.Value{}, errors.New("todo: builtin: " + callName)
	}
}

func (c *Compiler) parseFunctionCall(frame *Frame, args []ssa.Value, llvmFn, context 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 args {
		val, err := c.parseExpr(frame, param)
		if err != nil {
			return llvm.Value{}, err
		}
		params = append(params, val)
	}

	if !context.IsNil() {
		// This function takes a context parameter.
		// Add it to the end of the parameter list.
		params = append(params, context)
	}

	if frame.blocking && llvmFn.Name() == "time.Sleep" {
		// Set task state to TASK_STATE_SLEEP and set the duration.
		c.createRuntimeCall("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.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.createRuntimeCall("yieldToScheduler", []llvm.Value{result}, "")

		// Set task state to TASK_STATE_CALL.
		c.createRuntimeCall("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) {
	if instr.IsInvoke() {
		// Call an interface method with dynamic dispatch.
		itf, err := c.parseExpr(frame, instr.Value) // interface
		if err != nil {
			return llvm.Value{}, err
		}

		llvmFnType, err := c.getLLVMType(instr.Method.Type())
		if err != nil {
			return llvm.Value{}, err
		}
		if c.ir.SignatureNeedsContext(instr.Method.Type().(*types.Signature)) {
			// This is somewhat of a hack.
			// getLLVMType() has created a closure type for us, but we don't
			// actually want a closure type as an interface call can never be a
			// closure call. So extract the function pointer type from the
			// closure.
			// This happens because somewhere the same function signature is
			// used in a closure or bound method.
			llvmFnType = llvmFnType.Subtypes()[1]
		}

		values := []llvm.Value{
			itf,
			llvm.ConstInt(llvm.Int16Type(), uint64(c.ir.MethodNum(instr.Method)), false),
		}
		fn := c.createRuntimeCall("interfaceMethod", values, "invoke.func")
		fnCast := c.builder.CreateBitCast(fn, llvmFnType, "invoke.func.cast")
		receiverValue := c.builder.CreateExtractValue(itf, 1, "invoke.func.receiver")

		args := []llvm.Value{receiverValue}
		for _, arg := range instr.Args {
			val, err := c.parseExpr(frame, arg)
			if err != nil {
				return llvm.Value{}, err
			}
			args = append(args, val)
		}
		if c.ir.SignatureNeedsContext(instr.Method.Type().(*types.Signature)) {
			// This function takes an extra context parameter. An interface call
			// cannot also be a closure but we have to supply the nil pointer
			// anyway.
			args = append(args, llvm.ConstPointerNull(c.i8ptrType))
		}

		// TODO: blocking methods (needs analysis)
		return c.createCall(fnCast, args, ""), nil
	}

	// Try to call the function directly for trivially static calls.
	if fn := instr.StaticCallee(); fn != nil {
		if fn.Name() == "Asm" && len(instr.Args) == 1 {
			// Magic function: insert inline assembly instead of calling it.
			if named, ok := instr.Args[0].Type().(*types.Named); ok && named.Obj().Name() == "__asm" {
				fnType := llvm.FunctionType(llvm.VoidType(), []llvm.Type{}, false)
				asm := constant.StringVal(instr.Args[0].(*ssa.Const).Value)
				target := llvm.InlineAsm(fnType, asm, "", true, false, 0)
				return c.builder.CreateCall(target, nil, ""), nil
			}
		}
		targetFunc := c.ir.GetFunction(fn)
		if targetFunc.LLVMFn.IsNil() {
			return llvm.Value{}, errors.New("undefined function: " + targetFunc.LinkName())
		}
		var context llvm.Value
		if c.ir.FunctionNeedsContext(targetFunc) {
			// This function call is to a (potential) closure, not a regular
			// function. See whether it is a closure and if so, call it as such.
			// Else, supply a dummy nil pointer as the last parameter.
			var err error
			if mkClosure, ok := instr.Value.(*ssa.MakeClosure); ok {
				// closure is {context, function pointer}
				closure, err := c.parseExpr(frame, mkClosure)
				if err != nil {
					return llvm.Value{}, err
				}
				context = c.builder.CreateExtractValue(closure, 0, "")
			} else {
				context, err = getZeroValue(c.i8ptrType)
				if err != nil {
					return llvm.Value{}, err
				}
			}
		}
		return c.parseFunctionCall(frame, instr.Args, targetFunc.LLVMFn, context, c.ir.IsBlocking(targetFunc), parentHandle)
	}

	// Builtin or function pointer.
	switch call := instr.Value.(type) {
	case *ssa.Builtin:
		return c.parseBuiltin(frame, instr.Args, call.Name())
	default: // function pointer
		value, err := c.parseExpr(frame, instr.Value)
		if err != nil {
			return llvm.Value{}, err
		}
		// TODO: blocking function pointers (needs analysis)
		var context llvm.Value
		if c.ir.SignatureNeedsContext(instr.Signature()) {
			// 'value' is a closure, not a raw function pointer.
			// Extract the function pointer and the context pointer.
			// closure: {context, function pointer}
			context = c.builder.CreateExtractValue(value, 0, "")
			value = c.builder.CreateExtractValue(value, 1, "")
		}
		return c.parseFunctionCall(frame, instr.Args, value, context, false, parentHandle)
	}
}

func (c *Compiler) emitBoundsCheck(frame *Frame, arrayLen, index llvm.Value) {
	if frame.fn.IsNoBounds() {
		// The //go:nobounds pragma was added to the function to avoid bounds
		// checking.
		return
	}
	// Optimize away trivial cases.
	// LLVM would do this anyway with interprocedural optimizations, but it
	// helps to see cases where bounds checking would really help.
	if index.IsConstant() && arrayLen.IsConstant() {
		index := index.SExtValue()
		arrayLen := arrayLen.SExtValue()
		if index >= 0 && index < arrayLen {
			return
		}
	}
	c.createRuntimeCall("lookupBoundsCheck", []llvm.Value{arrayLen, index}, "")
}

func (c *Compiler) parseExpr(frame *Frame, expr ssa.Value) (llvm.Value, error) {
	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.createRuntimeCall("alloc", []llvm.Value{size}, expr.Comment)
			buf = c.builder.CreateBitCast(buf, llvm.PointerType(typ, 0), "")
		} else {
			buf = c.builder.CreateAlloca(typ, expr.Comment)
			zero, err := 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.ChangeInterface:
		// Do not change between interface types: always use the underlying
		// (concrete) type in the type number of the interface. Every method
		// call on an interface will do a lookup which method to call.
		// This is different from how the official Go compiler works, because of
		// heap allocation and because it's easier to implement, see:
		// https://research.swtch.com/interfaces
		return c.parseExpr(frame, expr.X)
	case *ssa.ChangeType:
		x, err := c.parseExpr(frame, expr.X)
		if err != nil {
			return llvm.Value{}, err
		}
		// The only case when we need to bitcast is when casting between named
		// struct types, as those are actually different in LLVM. Let's just
		// bitcast all struct types for ease of use.
		if _, ok := expr.Type().Underlying().(*types.Struct); ok {
			llvmType, err := c.getLLVMType(expr.X.Type())
			if err != nil {
				return llvm.Value{}, err
			}
			return c.builder.CreateBitCast(x, llvmType, "changetype"), nil
		}
		return x, nil
	case *ssa.Const:
		return c.parseConst(frame.fn.LinkName(), expr)
	case *ssa.Convert:
		x, err := c.parseExpr(frame, expr.X)
		if err != nil {
			return llvm.Value{}, err
		}
		return c.parseConvert(expr.X.Type(), expr.Type(), 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.Field:
		value, err := c.parseExpr(frame, expr.X)
		if err != nil {
			return llvm.Value{}, err
		}
		result := c.builder.CreateExtractValue(value, expr.Field, "")
		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:
		fn := c.ir.GetFunction(expr)
		ptr := fn.LLVMFn
		if c.ir.FunctionNeedsContext(fn) {
			// Create closure for function pointer.
			// Closure is: {context, function pointer}
			ptr = llvm.ConstStruct([]llvm.Value{
				llvm.ConstPointerNull(c.i8ptrType),
				ptr,
			}, false)
		}
		return ptr, nil
	case *ssa.Global:
		if strings.HasPrefix(expr.Name(), "__cgofn__cgo_") || strings.HasPrefix(expr.Name(), "_cgo_") {
			// Ignore CGo global variables which we don't use.
			return llvm.Value{}, ir.ErrCGoWrapper
		}
		value := c.ir.GetGlobal(expr).LLVMGlobal
		if value.IsNil() {
			return llvm.Value{}, errors.New("global not found: " + c.ir.GetGlobal(expr).LinkName())
		}
		return value, nil
	case *ssa.Index:
		array, 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
		}

		// Check bounds.
		arrayLen := expr.X.Type().(*types.Array).Len()
		arrayLenLLVM := llvm.ConstInt(c.lenType, uint64(arrayLen), false)
		c.emitBoundsCheck(frame, arrayLenLLVM, index)

		// Can't load directly from array (as index is non-constant), so have to
		// do it using an alloca+gep+load.
		alloca := c.builder.CreateAlloca(array.Type(), "")
		c.builder.CreateStore(array, alloca)
		zero := llvm.ConstInt(llvm.Int32Type(), 0, false)
		ptr := c.builder.CreateGEP(alloca, []llvm.Value{zero, index}, "")
		return c.builder.CreateLoad(ptr, ""), 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 pointer and length
		var bufptr, buflen llvm.Value
		switch ptrTyp := expr.X.Type().Underlying().(type) {
		case *types.Pointer:
			typ := expr.X.Type().(*types.Pointer).Elem().Underlying()
			switch typ := typ.(type) {
			case *types.Array:
				bufptr = val
				buflen = llvm.ConstInt(c.lenType, uint64(typ.Len()), false)
			default:
				return llvm.Value{}, errors.New("todo: indexaddr: " + typ.String())
			}
		case *types.Slice:
			bufptr = c.builder.CreateExtractValue(val, 0, "indexaddr.ptr")
			buflen = c.builder.CreateExtractValue(val, 1, "indexaddr.len")
		default:
			return llvm.Value{}, errors.New("todo: indexaddr: " + ptrTyp.String())
		}

		// Bounds check.
		// LLVM optimizes this away in most cases.
		c.emitBoundsCheck(frame, buflen, index)

		switch expr.X.Type().(type) {
		case *types.Pointer:
			indices := []llvm.Value{
				llvm.ConstInt(llvm.Int32Type(), 0, false),
				index,
			}
			return c.builder.CreateGEP(bufptr, indices, ""), nil
		case *types.Slice:
			return c.builder.CreateGEP(bufptr, []llvm.Value{index}, ""), nil
		default:
			panic("unreachable")
		}
	case *ssa.Lookup:
		if expr.CommaOk {
			return llvm.Value{}, errors.New("todo: lookup with comma-ok")
		}
		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
		}
		switch xType := expr.X.Type().(type) {
		case *types.Basic:
			// Value type must be a string, which is a basic type.
			if xType.Kind() != types.String {
				panic("lookup on non-string?")
			}

			// Bounds check.
			// LLVM optimizes this away in most cases.
			length, err := c.parseBuiltin(frame, []ssa.Value{expr.X}, "len")
			if err != nil {
				return llvm.Value{}, err // shouldn't happen
			}
			c.emitBoundsCheck(frame, length, index)

			// Lookup byte
			buf := c.builder.CreateExtractValue(value, 0, "")
			bufPtr := c.builder.CreateGEP(buf, []llvm.Value{index}, "")
			return c.builder.CreateLoad(bufPtr, ""), nil
		case *types.Map:
			switch keyType := xType.Key().Underlying().(type) {
			case *types.Basic:
				llvmValueType, err := c.getLLVMType(expr.Type())
				if err != nil {
					return llvm.Value{}, err
				}
				mapValueAlloca := c.builder.CreateAlloca(llvmValueType, "hashmap.value")
				mapValuePtr := c.builder.CreateBitCast(mapValueAlloca, c.i8ptrType, "hashmap.valueptr")
				if keyType.Info()&types.IsString != 0 {
					params := []llvm.Value{value, index, mapValuePtr}
					c.createRuntimeCall("hashmapStringGet", params, "")
					return c.builder.CreateLoad(mapValueAlloca, ""), nil
				} else if keyType.Info()&(types.IsBoolean|types.IsInteger) != 0 {
					keyAlloca := c.builder.CreateAlloca(index.Type(), "hashmap.key")
					c.builder.CreateStore(index, keyAlloca)
					keyPtr := c.builder.CreateBitCast(keyAlloca, c.i8ptrType, "hashmap.keyptr")
					params := []llvm.Value{value, keyPtr, mapValuePtr}
					c.createRuntimeCall("hashmapBinaryGet", params, "")
					return c.builder.CreateLoad(mapValueAlloca, ""), nil
				} else {
					return llvm.Value{}, errors.New("todo: map lookup key type: " + keyType.String())
				}
			default:
				return llvm.Value{}, errors.New("todo: map lookup key type: " + keyType.String())
			}
		default:
			panic("unknown lookup type: " + expr.String())
		}

	case *ssa.MakeClosure:
		return c.parseMakeClosure(frame, expr)

	case *ssa.MakeInterface:
		val, err := c.parseExpr(frame, expr.X)
		if err != nil {
			return llvm.Value{}, err
		}
		return c.parseMakeInterface(val, expr.X.Type(), "")
	case *ssa.MakeMap:
		mapType := expr.Type().Underlying().(*types.Map)
		llvmKeyType, err := c.getLLVMType(mapType.Key().Underlying())
		if err != nil {
			return llvm.Value{}, err
		}
		llvmValueType, err := c.getLLVMType(mapType.Elem().Underlying())
		if err != nil {
			return llvm.Value{}, err
		}
		keySize := c.targetData.TypeAllocSize(llvmKeyType)
		valueSize := c.targetData.TypeAllocSize(llvmValueType)
		llvmKeySize := llvm.ConstInt(llvm.Int8Type(), keySize, false)
		llvmValueSize := llvm.ConstInt(llvm.Int8Type(), valueSize, false)
		hashmap := c.createRuntimeCall("hashmapMake", []llvm.Value{llvmKeySize, llvmValueSize}, "")
		return hashmap, nil
	case *ssa.MakeSlice:
		sliceLen, err := c.parseExpr(frame, expr.Len)
		if err != nil {
			return llvm.Value{}, nil
		}
		sliceCap, err := c.parseExpr(frame, expr.Cap)
		if err != nil {
			return llvm.Value{}, nil
		}
		sliceType := expr.Type().Underlying().(*types.Slice)
		llvmElemType, err := c.getLLVMType(sliceType.Elem())
		if err != nil {
			return llvm.Value{}, nil
		}
		elemSize := c.targetData.TypeAllocSize(llvmElemType)

		// Bounds checking.
		if !frame.fn.IsNoBounds() {
			c.createRuntimeCall("sliceBoundsCheckMake", []llvm.Value{sliceLen, sliceCap}, "")
		}

		// Allocate the backing array.
		// TODO: escape analysis
		elemSizeValue := llvm.ConstInt(c.uintptrType, elemSize, false)
		sliceCapCast, err := c.parseConvert(expr.Cap.Type(), types.Typ[types.Uintptr], sliceCap)
		if err != nil {
			return llvm.Value{}, err
		}
		sliceSize := c.builder.CreateBinOp(llvm.Mul, elemSizeValue, sliceCapCast, "makeslice.cap")
		slicePtr := c.createRuntimeCall("alloc", []llvm.Value{sliceSize}, "makeslice.buf")
		slicePtr = c.builder.CreateBitCast(slicePtr, llvm.PointerType(llvmElemType, 0), "makeslice.array")

		if c.targetData.TypeAllocSize(sliceLen.Type()) > c.targetData.TypeAllocSize(c.lenType) {
			sliceLen = c.builder.CreateTrunc(sliceLen, c.lenType, "")
			sliceCap = c.builder.CreateTrunc(sliceCap, c.lenType, "")
		}

		// Create the slice.
		slice := llvm.ConstStruct([]llvm.Value{
			llvm.Undef(slicePtr.Type()),
			llvm.Undef(c.lenType),
			llvm.Undef(c.lenType),
		}, false)
		slice = c.builder.CreateInsertValue(slice, slicePtr, 0, "")
		slice = c.builder.CreateInsertValue(slice, sliceLen, 1, "")
		slice = c.builder.CreateInsertValue(slice, sliceCap, 2, "")
		return slice, nil
	case *ssa.Next:
		rangeVal := expr.Iter.(*ssa.Range).X
		llvmRangeVal, err := c.parseExpr(frame, rangeVal)
		if err != nil {
			return llvm.Value{}, err
		}
		it, err := c.parseExpr(frame, expr.Iter)
		if err != nil {
			return llvm.Value{}, err
		}
		if expr.IsString {
			return c.createRuntimeCall("stringNext", []llvm.Value{llvmRangeVal, it}, "range.next"), nil
		} else { // map
			llvmKeyType, err := c.getLLVMType(rangeVal.Type().(*types.Map).Key())
			if err != nil {
				return llvm.Value{}, err
			}
			llvmValueType, err := c.getLLVMType(rangeVal.Type().(*types.Map).Elem())
			if err != nil {
				return llvm.Value{}, err
			}

			mapKeyAlloca := c.builder.CreateAlloca(llvmKeyType, "range.key")
			mapKeyPtr := c.builder.CreateBitCast(mapKeyAlloca, c.i8ptrType, "range.keyptr")
			mapValueAlloca := c.builder.CreateAlloca(llvmValueType, "range.value")
			mapValuePtr := c.builder.CreateBitCast(mapValueAlloca, c.i8ptrType, "range.valueptr")
			ok := c.createRuntimeCall("hashmapNext", []llvm.Value{llvmRangeVal, it, mapKeyPtr, mapValuePtr}, "range.next")

			tuple := llvm.Undef(llvm.StructType([]llvm.Type{llvm.Int1Type(), llvmKeyType, llvmValueType}, false))
			tuple = c.builder.CreateInsertValue(tuple, ok, 0, "")
			tuple = c.builder.CreateInsertValue(tuple, c.builder.CreateLoad(mapKeyAlloca, ""), 1, "")
			tuple = c.builder.CreateInsertValue(tuple, c.builder.CreateLoad(mapValueAlloca, ""), 2, "")
			return tuple, 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.Range:
		var iteratorType llvm.Type
		switch typ := expr.X.Type().Underlying().(type) {
		case *types.Basic: // string
			iteratorType = c.mod.GetTypeByName("runtime.stringIterator")
		case *types.Map:
			iteratorType = c.mod.GetTypeByName("runtime.hashmapIterator")
		default:
			panic("unknown type in range: " + typ.String())
		}
		it := c.builder.CreateAlloca(iteratorType, "range.it")
		zero, err := getZeroValue(iteratorType)
		if err != nil {
			return llvm.Value{}, nil
		}
		c.builder.CreateStore(zero, it)
		return it, nil
	case *ssa.Slice:
		if expr.Max != nil {
			return llvm.Value{}, errors.New("todo: full slice expressions (with max): " + expr.Type().String())
		}
		value, err := c.parseExpr(frame, expr.X)
		if err != nil {
			return llvm.Value{}, err
		}
		var low, high llvm.Value
		if expr.Low == nil {
			low = llvm.ConstInt(c.intType, 0, false)
		} else {
			low, err = c.parseExpr(frame, expr.Low)
			if err != nil {
				return llvm.Value{}, nil
			}
		}
		if expr.High != nil {
			high, err = c.parseExpr(frame, expr.High)
			if err != nil {
				return llvm.Value{}, nil
			}
		}
		switch typ := expr.X.Type().Underlying().(type) {
		case *types.Pointer: // pointer to array
			// slice an array
			length := typ.Elem().(*types.Array).Len()
			llvmLen := llvm.ConstInt(c.lenType, uint64(length), false)
			llvmLenInt := llvm.ConstInt(c.intType, uint64(length), false)
			if high.IsNil() {
				high = llvmLenInt
			}
			indices := []llvm.Value{
				llvm.ConstInt(llvm.Int32Type(), 0, false),
				low,
			}
			slicePtr := c.builder.CreateGEP(value, indices, "slice.ptr")
			sliceLen := c.builder.CreateSub(high, low, "slice.len")
			sliceCap := c.builder.CreateSub(llvmLenInt, low, "slice.cap")

			// This check is optimized away in most cases.
			if !frame.fn.IsNoBounds() {
				c.createRuntimeCall("sliceBoundsCheck", []llvm.Value{llvmLen, low, high}, "")
			}

			if c.targetData.TypeAllocSize(sliceLen.Type()) > c.targetData.TypeAllocSize(c.lenType) {
				sliceLen = c.builder.CreateTrunc(sliceLen, c.lenType, "")
				sliceCap = c.builder.CreateTrunc(sliceCap, c.lenType, "")
			}

			slice := llvm.ConstStruct([]llvm.Value{
				llvm.Undef(slicePtr.Type()),
				llvm.Undef(c.lenType),
				llvm.Undef(c.lenType),
			}, false)
			slice = c.builder.CreateInsertValue(slice, slicePtr, 0, "")
			slice = c.builder.CreateInsertValue(slice, sliceLen, 1, "")
			slice = c.builder.CreateInsertValue(slice, sliceCap, 2, "")
			return slice, nil

		case *types.Slice:
			// slice a slice
			oldPtr := c.builder.CreateExtractValue(value, 0, "")
			oldLen := c.builder.CreateExtractValue(value, 1, "")
			oldCap := c.builder.CreateExtractValue(value, 2, "")
			if high.IsNil() {
				high = oldLen
			}

			if !frame.fn.IsNoBounds() {
				c.createRuntimeCall("sliceBoundsCheck", []llvm.Value{oldLen, low, high}, "")
			}

			if c.targetData.TypeAllocSize(low.Type()) > c.targetData.TypeAllocSize(c.lenType) {
				low = c.builder.CreateTrunc(low, c.lenType, "")
			}
			if c.targetData.TypeAllocSize(high.Type()) > c.targetData.TypeAllocSize(c.lenType) {
				high = c.builder.CreateTrunc(high, c.lenType, "")
			}

			newPtr := c.builder.CreateGEP(oldPtr, []llvm.Value{low}, "")
			newLen := c.builder.CreateSub(high, low, "")
			newCap := c.builder.CreateSub(oldCap, low, "")
			slice := llvm.ConstStruct([]llvm.Value{
				llvm.Undef(newPtr.Type()),
				llvm.Undef(c.lenType),
				llvm.Undef(c.lenType),
			}, false)
			slice = c.builder.CreateInsertValue(slice, newPtr, 0, "")
			slice = c.builder.CreateInsertValue(slice, newLen, 1, "")
			slice = c.builder.CreateInsertValue(slice, newCap, 2, "")
			return slice, nil

		case *types.Basic:
			if typ.Kind() != types.String {
				return llvm.Value{}, errors.New("unknown slice type: " + typ.String())
			}
			// slice a string
			oldPtr := c.builder.CreateExtractValue(value, 0, "")
			oldLen := c.builder.CreateExtractValue(value, 1, "")
			if high.IsNil() {
				high = oldLen
			}

			if !frame.fn.IsNoBounds() {
				c.createRuntimeCall("sliceBoundsCheck", []llvm.Value{oldLen, low, high}, "")
			}

			newPtr := c.builder.CreateGEP(oldPtr, []llvm.Value{low}, "")
			newLen := c.builder.CreateSub(high, low, "")
			str, err := getZeroValue(c.mod.GetTypeByName("runtime._string"))
			if err != nil {
				return llvm.Value{}, err
			}
			str = c.builder.CreateInsertValue(str, newPtr, 0, "")
			str = c.builder.CreateInsertValue(str, newLen, 1, "")
			return str, nil

		default:
			return llvm.Value{}, errors.New("unknown slice type: " + typ.String())
		}
	case *ssa.TypeAssert:
		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
		}
		valueNil, err := getZeroValue(assertedType)
		if err != nil {
			return llvm.Value{}, err
		}

		actualTypeNum := c.builder.CreateExtractValue(itf, 0, "interface.type")
		commaOk := llvm.Value{}
		if itf, ok := expr.AssertedType.Underlying().(*types.Interface); ok {
			// Type assert on interface type.
			// This is slightly non-trivial: at runtime the list of methods
			// needs to be checked to see whether it implements the interface.
			// At the same time, the interface value itself is unchanged.
			itfTypeNum := c.ir.InterfaceNum(itf)
			itfTypeNumValue := llvm.ConstInt(llvm.Int16Type(), uint64(itfTypeNum), false)
			commaOk = c.createRuntimeCall("interfaceImplements", []llvm.Value{actualTypeNum, itfTypeNumValue}, "")

		} else {
			// Type assert on concrete type.
			// This is easy: just compare the type number.
			assertedTypeNum, typeExists := c.ir.TypeNum(expr.AssertedType)
			if !typeExists {
				// Static analysis has determined this type assert will never apply.
				// Using undef here so that LLVM knows we'll never get here and
				// can optimize accordingly.
				undef := llvm.Undef(assertedType)
				commaOk := llvm.ConstInt(llvm.Int1Type(), 0, false)
				if expr.CommaOk {
					return llvm.ConstStruct([]llvm.Value{undef, commaOk}, false), nil
				} else {
					c.createRuntimeCall("interfaceTypeAssert", []llvm.Value{commaOk}, "")
					return undef, nil
				}
			}
			if assertedTypeNum >= 1<<16 {
				return llvm.Value{}, errors.New("interface typecodes do not fit in a 16-bit integer")
			}

			assertedTypeNumValue := llvm.ConstInt(llvm.Int16Type(), uint64(assertedTypeNum), false)
			commaOk = c.builder.CreateICmp(llvm.IntEQ, assertedTypeNumValue, actualTypeNum, "")
		}

		// Add 2 new basic blocks (that should get optimized away): one for the
		// 'ok' case and one for all instructions following this type assert.
		// This is necessary because we need to insert the casted value or the
		// nil value based on whether the assert was successful. Casting before
		// this check tells LLVM that it can use this value and may
		// speculatively dereference pointers before the check. This can lead to
		// a miscompilation resulting in a segfault at runtime.
		// Additionally, this is even required by the Go spec: a failed
		// typeassert should return a zero value, not an incorrectly casted
		// value.

		prevBlock := c.builder.GetInsertBlock()
		okBlock := c.ctx.AddBasicBlock(frame.fn.LLVMFn, "typeassert.ok")
		nextBlock := c.ctx.AddBasicBlock(frame.fn.LLVMFn, "typeassert.next")
		frame.blocks[frame.currentBlock] = nextBlock // adjust outgoing block for phi nodes
		c.builder.CreateCondBr(commaOk, okBlock, nextBlock)

		// Retrieve the value from the interface if the type assert was
		// successful.
		c.builder.SetInsertPointAtEnd(okBlock)
		var valueOk llvm.Value
		if _, ok := expr.AssertedType.Underlying().(*types.Interface); ok {
			// Type assert on interface type. Easy: just return the same
			// interface value.
			valueOk = itf
		} else {
			// Type assert on concrete type. Extract the underlying type from
			// the interface (but only after checking it matches).
			valuePtr := c.builder.CreateExtractValue(itf, 1, "typeassert.value.ptr")
			if c.targetData.TypeAllocSize(assertedType) > c.targetData.TypeAllocSize(c.i8ptrType) {
				// Value was stored in an allocated buffer, load it from there.
				valuePtrCast := c.builder.CreateBitCast(valuePtr, llvm.PointerType(assertedType, 0), "")
				valueOk = c.builder.CreateLoad(valuePtrCast, "typeassert.value.ok")
			} else {
				// Value was stored directly in the interface.
				switch assertedType.TypeKind() {
				case llvm.IntegerTypeKind:
					valueOk = c.builder.CreatePtrToInt(valuePtr, assertedType, "typeassert.value.ok")
				case llvm.PointerTypeKind:
					valueOk = c.builder.CreateBitCast(valuePtr, assertedType, "typeassert.value.ok")
				case llvm.StructTypeKind:
					// A bitcast would be useful here, but bitcast doesn't allow
					// aggregate types. So we'll bitcast it using an alloca.
					// Hopefully this will get optimized away.
					mem := c.builder.CreateAlloca(c.i8ptrType, "")
					c.builder.CreateStore(valuePtr, mem)
					memStructPtr := c.builder.CreateBitCast(mem, llvm.PointerType(assertedType, 0), "")
					valueOk = c.builder.CreateLoad(memStructPtr, "typeassert.value.ok")
				default:
					return llvm.Value{}, errors.New("todo: typeassert: bitcast small types")
				}
			}
		}
		c.builder.CreateBr(nextBlock)

		// Continue after the if statement.
		c.builder.SetInsertPointAtEnd(nextBlock)
		phi := c.builder.CreatePHI(assertedType, "typeassert.value")
		phi.AddIncoming([]llvm.Value{valueNil, valueOk}, []llvm.BasicBlock{prevBlock, okBlock})

		if expr.CommaOk {
			tuple := llvm.ConstStruct([]llvm.Value{llvm.Undef(assertedType), llvm.Undef(llvm.Int1Type())}, false) // create empty tuple
			tuple = c.builder.CreateInsertValue(tuple, phi, 0, "")                                                // insert value
			tuple = c.builder.CreateInsertValue(tuple, commaOk, 1, "")                                            // insert 'comma ok' boolean
			return tuple, nil
		} else {
			// This is kind of dirty as the branch above becomes mostly useless,
			// but hopefully this gets optimized away.
			c.createRuntimeCall("interfaceTypeAssert", []llvm.Value{commaOk}, "")
			return phi, nil
		}
	case *ssa.UnOp:
		return c.parseUnOp(frame, expr)
	default:
		return llvm.Value{}, errors.New("todo: unknown expression: " + expr.String())
	}
}

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
	}
	switch typ := binop.X.Type().Underlying().(type) {
	case *types.Basic:
		if typ.Info()&types.IsInteger != 0 {
			// Operations on integers
			signed := typ.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, token.SHR:
				sizeX := c.targetData.TypeAllocSize(x.Type())
				sizeY := c.targetData.TypeAllocSize(y.Type())
				if sizeX > sizeY {
					// x and y must have equal sizes, make Y bigger in this case.
					// y is unsigned, this has been checked by the Go type checker.
					y = c.builder.CreateZExt(y, x.Type(), "")
				} else if sizeX < sizeY {
					// What about shifting more than the integer width?
					// I'm not entirely sure what the Go spec is on that, but as
					// Intel CPUs have undefined behavior when shifting more
					// than the integer width I'm assuming it is also undefined
					// in Go.
					y = c.builder.CreateTrunc(y, x.Type(), "")
				}
				switch binop.Op {
				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
					}
				default:
					panic("unreachable")
				}
			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.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.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("todo: binop on integer: " + binop.Op.String())
			}
		} else if typ.Info()&types.IsFloat != 0 {
			// Operations on floats
			switch binop.Op {
			case token.ADD:
				return c.builder.CreateFAdd(x, y, ""), nil
			case token.SUB: // -
				return c.builder.CreateFSub(x, y, ""), nil
			case token.MUL: // *
				return c.builder.CreateFMul(x, y, ""), nil
			case token.QUO: // /
				return c.builder.CreateFDiv(x, y, ""), nil
			case token.REM: // %
				return c.builder.CreateFRem(x, y, ""), nil
			case token.EQL: // ==
				return c.builder.CreateFCmp(llvm.FloatOEQ, x, y, ""), nil
			case token.NEQ: // !=
				return c.builder.CreateFCmp(llvm.FloatONE, x, y, ""), nil
			case token.LSS: // <
				return c.builder.CreateFCmp(llvm.FloatOLT, x, y, ""), nil
			case token.LEQ: // <=
				return c.builder.CreateFCmp(llvm.FloatOLE, x, y, ""), nil
			case token.GTR: // >
				return c.builder.CreateFCmp(llvm.FloatOGT, x, y, ""), nil
			case token.GEQ: // >=
				return c.builder.CreateFCmp(llvm.FloatOGE, x, y, ""), nil
			default:
				return llvm.Value{}, errors.New("todo: binop on float: " + binop.Op.String())
			}
		} else if typ.Kind() == types.UnsafePointer {
			// Operations on pointers
			switch binop.Op {
			case token.EQL: // ==
				return c.builder.CreateICmp(llvm.IntEQ, x, y, ""), nil
			case token.NEQ: // !=
				return c.builder.CreateICmp(llvm.IntNE, x, y, ""), nil
			default:
				return llvm.Value{}, errors.New("todo: binop on pointer: " + binop.Op.String())
			}
		} else if typ.Info()&types.IsString != 0 {
			// Operations on strings
			switch binop.Op {
			case token.ADD:
				return c.createRuntimeCall("stringConcat", []llvm.Value{x, y}, ""), nil
			case token.EQL, token.NEQ: // ==, !=
				result := c.createRuntimeCall("stringEqual", []llvm.Value{x, y}, "")
				if binop.Op == token.NEQ {
					result = c.builder.CreateNot(result, "")
				}
				return result, nil
			default:
				return llvm.Value{}, errors.New("todo: binop on string: " + binop.Op.String())
			}
		} else {
			return llvm.Value{}, errors.New("todo: unknown basic type in binop: " + typ.String())
		}
	case *types.Signature:
		if c.ir.SignatureNeedsContext(typ) {
			// This is a closure, not a function pointer. Get the underlying
			// function pointer.
			// This is safe: function pointers are generally not comparable
			// against each other, only against nil. So one or both has to be
			// nil, so we can ignore the contents of the closure.
			x = c.builder.CreateExtractValue(x, 1, "")
			y = c.builder.CreateExtractValue(y, 1, "")
		}
		switch binop.Op {
		case token.EQL: // ==
			return c.builder.CreateICmp(llvm.IntEQ, x, y, ""), nil
		case token.NEQ: // !=
			return c.builder.CreateICmp(llvm.IntNE, x, y, ""), nil
		default:
			return llvm.Value{}, errors.New("binop on signature: " + binop.Op.String())
		}
	case *types.Interface:
		switch binop.Op {
		case token.EQL, token.NEQ: // ==, !=
			result := c.createRuntimeCall("interfaceEqual", []llvm.Value{x, y}, "")
			if binop.Op == token.NEQ {
				result = c.builder.CreateNot(result, "")
			}
			return result, nil
		default:
			return llvm.Value{}, errors.New("binop on interface: " + binop.Op.String())
		}
	case *types.Pointer:
		switch binop.Op {
		case token.EQL: // ==
			return c.builder.CreateICmp(llvm.IntEQ, x, y, ""), nil
		case token.NEQ: // !=
			return c.builder.CreateICmp(llvm.IntNE, x, y, ""), nil
		default:
			return llvm.Value{}, errors.New("todo: binop on pointer: " + binop.Op.String())
		}
	default:
		return llvm.Value{}, errors.New("unknown binop type: " + binop.X.Type().String())
	}
}

func (c *Compiler) parseConst(prefix string, expr *ssa.Const) (llvm.Value, error) {
	switch typ := expr.Type().Underlying().(type) {
	case *types.Basic:
		llvmType, err := c.getLLVMType(typ)
		if err != nil {
			return llvm.Value{}, err
		}
		if typ.Info()&types.IsBoolean != 0 {
			b := constant.BoolVal(expr.Value)
			n := uint64(0)
			if b {
				n = 1
			}
			return llvm.ConstInt(llvmType, n, false), nil
		} else if typ.Info()&types.IsString != 0 {
			str := constant.StringVal(expr.Value)
			strLen := llvm.ConstInt(c.lenType, uint64(len(str)), false)
			objname := prefix + "$string"
			global := llvm.AddGlobal(c.mod, llvm.ArrayType(llvm.Int8Type(), len(str)), objname)
			global.SetInitializer(c.ctx.ConstString(str, false))
			global.SetLinkage(llvm.InternalLinkage)
			global.SetGlobalConstant(true)
			global.SetUnnamedAddr(true)
			zero := llvm.ConstInt(llvm.Int32Type(), 0, false)
			strPtr := c.builder.CreateInBoundsGEP(global, []llvm.Value{zero, zero}, "")
			strObj := llvm.ConstNamedStruct(c.mod.GetTypeByName("runtime._string"), []llvm.Value{strPtr, strLen})
			return strObj, nil
		} else if typ.Kind() == types.UnsafePointer {
			if !expr.IsNil() {
				value, _ := constant.Uint64Val(expr.Value)
				return llvm.ConstIntToPtr(llvm.ConstInt(c.uintptrType, value, false), c.i8ptrType), nil
			}
			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 if typ.Info()&types.IsFloat != 0 {
			n, _ := constant.Float64Val(expr.Value)
			return llvm.ConstFloat(llvmType, n), nil
		} else {
			return llvm.Value{}, errors.New("todo: unknown constant: " + expr.String())
		}
	case *types.Signature:
		if expr.Value != nil {
			return llvm.Value{}, errors.New("non-nil signature constant")
		}
		sig, err := c.getLLVMType(expr.Type())
		if err != nil {
			return llvm.Value{}, err
		}
		return getZeroValue(sig)
	case *types.Interface:
		if expr.Value != nil {
			return llvm.Value{}, errors.New("non-nil interface constant")
		}
		// Create a generic nil interface with no dynamic type (typecode=0).
		fields := []llvm.Value{
			llvm.ConstInt(llvm.Int16Type(), 0, false),
			llvm.ConstPointerNull(c.i8ptrType),
		}
		itf := llvm.ConstNamedStruct(c.mod.GetTypeByName("runtime._interface"), fields)
		return itf, nil
	case *types.Pointer:
		if expr.Value != nil {
			return llvm.Value{}, errors.New("non-nil pointer constant")
		}
		llvmType, err := c.getLLVMType(typ)
		if err != nil {
			return llvm.Value{}, err
		}
		return llvm.ConstPointerNull(llvmType), nil
	case *types.Slice:
		if expr.Value != nil {
			return llvm.Value{}, errors.New("non-nil slice constant")
		}
		elemType, err := c.getLLVMType(typ.Elem())
		if err != nil {
			return llvm.Value{}, err
		}
		llvmPtr := llvm.ConstPointerNull(llvm.PointerType(elemType, 0))
		llvmLen := llvm.ConstInt(c.lenType, 0, false)
		slice := llvm.ConstStruct([]llvm.Value{
			llvmPtr, // backing array
			llvmLen, // len
			llvmLen, // cap
		}, false)
		return slice, nil
	default:
		return llvm.Value{}, errors.New("todo: unknown constant: " + expr.String())
	}
}

func (c *Compiler) parseConvert(typeFrom, typeTo types.Type, value llvm.Value) (llvm.Value, error) {
	llvmTypeFrom := value.Type()
	llvmTypeTo, err := c.getLLVMType(typeTo)
	if err != nil {
		return llvm.Value{}, err
	}

	// Conversion between unsafe.Pointer and uintptr.
	isPtrFrom := isPointer(typeFrom.Underlying())
	isPtrTo := isPointer(typeTo.Underlying())
	if isPtrFrom && !isPtrTo {
		return c.builder.CreatePtrToInt(value, llvmTypeTo, ""), nil
	} else if !isPtrFrom && isPtrTo {
		return c.builder.CreateIntToPtr(value, llvmTypeTo, ""), nil
	}

	// Conversion between pointers and unsafe.Pointer.
	if isPtrFrom && isPtrTo {
		return c.builder.CreateBitCast(value, llvmTypeTo, ""), nil
	}

	switch typeTo := typeTo.Underlying().(type) {
	case *types.Basic:
		sizeFrom := c.targetData.TypeAllocSize(llvmTypeFrom)

		if typeTo.Info()&types.IsString != 0 {
			switch typeFrom := typeFrom.Underlying().(type) {
			case *types.Basic:
				// Assume a Unicode code point, as that is the only possible
				// value here.
				// Cast to an i32 value as expected by
				// runtime.stringFromUnicode.
				if sizeFrom > 4 {
					value = c.builder.CreateTrunc(value, llvm.Int32Type(), "")
				} else if sizeFrom < 4 && typeTo.Info()&types.IsUnsigned != 0 {
					value = c.builder.CreateZExt(value, llvm.Int32Type(), "")
				} else if sizeFrom < 4 {
					value = c.builder.CreateSExt(value, llvm.Int32Type(), "")
				}
				return c.createRuntimeCall("stringFromUnicode", []llvm.Value{value}, ""), nil
			case *types.Slice:
				switch typeFrom.Elem().(*types.Basic).Kind() {
				case types.Byte:
					return c.createRuntimeCall("stringFromBytes", []llvm.Value{value}, ""), nil
				default:
					return llvm.Value{}, errors.New("todo: convert to string: " + typeFrom.String())
				}
			default:
				return llvm.Value{}, errors.New("todo: convert to string: " + typeFrom.String())
			}
		}

		typeFrom := typeFrom.Underlying().(*types.Basic)
		sizeTo := c.targetData.TypeAllocSize(llvmTypeTo)

		if typeFrom.Info()&types.IsInteger != 0 && typeTo.Info()&types.IsInteger != 0 {
			// Conversion between two integers.
			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
			}
		}

		if typeFrom.Info()&types.IsFloat != 0 && typeTo.Info()&types.IsFloat != 0 {
			// Conversion between two floats.
			if sizeFrom > sizeTo {
				return c.builder.CreateFPTrunc(value, llvmTypeTo, ""), nil
			} else if sizeFrom < sizeTo {
				return c.builder.CreateFPExt(value, llvmTypeTo, ""), nil
			} else {
				return value, nil
			}
		}

		if typeFrom.Info()&types.IsFloat != 0 && typeTo.Info()&types.IsInteger != 0 {
			// Conversion from float to int.
			if typeTo.Info()&types.IsUnsigned != 0 { // to signed int
				return c.builder.CreateFPToSI(value, llvmTypeTo, ""), nil
			} else { // to unsigned int
				return c.builder.CreateFPToUI(value, llvmTypeTo, ""), nil
			}
		}

		if typeFrom.Info()&types.IsInteger != 0 && typeTo.Info()&types.IsFloat != 0 {
			// Conversion from int to float.
			if typeFrom.Info()&types.IsUnsigned != 0 { // from signed int
				return c.builder.CreateSIToFP(value, llvmTypeTo, ""), nil
			} else { // from unsigned int
				return c.builder.CreateUIToFP(value, llvmTypeTo, ""), nil
			}
		}

		return llvm.Value{}, errors.New("todo: convert: basic non-integer type: " + typeFrom.String() + " -> " + typeTo.String())

	case *types.Slice:
		if basic, ok := typeFrom.(*types.Basic); !ok || basic.Kind() != types.String {
			panic("can only convert from a string to a slice")
		}

		elemType := typeTo.Elem().Underlying().(*types.Basic) // must be byte or rune
		switch elemType.Kind() {
		case types.Byte:
			return c.createRuntimeCall("stringToBytes", []llvm.Value{value}, ""), nil
		default:
			return llvm.Value{}, errors.New("todo: convert from string: " + elemType.String())
		}

	default:
		return llvm.Value{}, errors.New("todo: convert " + typeTo.String() + " <- " + typeFrom.String())
	}
}

func (c *Compiler) parseMakeClosure(frame *Frame, expr *ssa.MakeClosure) (llvm.Value, error) {
	if len(expr.Bindings) == 0 {
		panic("unexpected: MakeClosure without bound variables")
	}
	f := c.ir.GetFunction(expr.Fn.(*ssa.Function))
	if !c.ir.FunctionNeedsContext(f) {
		// Maybe AnalyseFunctionPointers didn't run?
		panic("MakeClosure on function signature without context")
	}

	// Collect all bound variables.
	boundVars := make([]llvm.Value, 0, len(expr.Bindings))
	boundVarTypes := make([]llvm.Type, 0, len(expr.Bindings))
	for _, binding := range expr.Bindings {
		// The context stores the bound variables.
		llvmBoundVar, err := c.parseExpr(frame, binding)
		if err != nil {
			return llvm.Value{}, err
		}
		boundVars = append(boundVars, llvmBoundVar)
		boundVarTypes = append(boundVarTypes, llvmBoundVar.Type())
	}
	contextType := llvm.StructType(boundVarTypes, false)

	// Allocate memory for the context.
	contextAlloc := llvm.Value{}
	contextHeapAlloc := llvm.Value{}
	if c.targetData.TypeAllocSize(contextType) <= c.targetData.TypeAllocSize(c.i8ptrType) {
		// Context fits in a pointer - e.g. when it is a pointer. Store it
		// directly in the stack after a convert.
		// Because contextType is a struct and we have to cast it to a *i8,
		// store it in an alloca first for bitcasting (store+bitcast+load).
		contextAlloc = c.builder.CreateAlloca(contextType, "")
	} else {
		// Context is bigger than a pointer, so allocate it on the heap.
		size := c.targetData.TypeAllocSize(contextType)
		sizeValue := llvm.ConstInt(c.uintptrType, size, false)
		contextHeapAlloc = c.createRuntimeCall("alloc", []llvm.Value{sizeValue}, "")
		contextAlloc = c.builder.CreateBitCast(contextHeapAlloc, llvm.PointerType(contextType, 0), "")
	}

	// Store all bound variables in the alloca or heap pointer.
	for i, boundVar := range boundVars {
		indices := []llvm.Value{
			llvm.ConstInt(llvm.Int32Type(), 0, false),
			llvm.ConstInt(llvm.Int32Type(), uint64(i), false),
		}
		gep := c.builder.CreateInBoundsGEP(contextAlloc, indices, "")
		c.builder.CreateStore(boundVar, gep)
	}

	context := llvm.Value{}
	if c.targetData.TypeAllocSize(contextType) <= c.targetData.TypeAllocSize(c.i8ptrType) {
		// Load value (as *i8) from the alloca.
		contextAlloc = c.builder.CreateBitCast(contextAlloc, llvm.PointerType(c.i8ptrType, 0), "")
		context = c.builder.CreateLoad(contextAlloc, "")
	} else {
		// Get the original heap allocation pointer, which already is an
		// *i8.
		context = contextHeapAlloc
	}

	// Get the function signature type, which is a closure type.
	// A closure is a tuple of {context, function pointer}.
	typ, err := c.getLLVMType(f.Signature)
	if err != nil {
		return llvm.Value{}, err
	}

	// Create the closure, which is a struct: {context, function pointer}.
	closure, err := getZeroValue(typ)
	if err != nil {
		return llvm.Value{}, err
	}
	closure = c.builder.CreateInsertValue(closure, f.LLVMFn, 1, "")
	closure = c.builder.CreateInsertValue(closure, context, 0, "")
	return closure, nil
}

func (c *Compiler) parseMakeInterface(val llvm.Value, typ types.Type, global string) (llvm.Value, error) {
	var itfValue llvm.Value
	size := c.targetData.TypeAllocSize(val.Type())
	if size > c.targetData.TypeAllocSize(c.i8ptrType) {
		if global != "" {
			// Allocate in a global variable.
			global := llvm.AddGlobal(c.mod, val.Type(), global+"$itfvalue")
			global.SetInitializer(val)
			global.SetLinkage(llvm.InternalLinkage)
			global.SetGlobalConstant(true)
			zero := llvm.ConstInt(llvm.Int32Type(), 0, false)
			itfValueRaw := llvm.ConstInBoundsGEP(global, []llvm.Value{zero, zero})
			itfValue = llvm.ConstBitCast(itfValueRaw, c.i8ptrType)
		} else {
			// Allocate on the heap and put a pointer in the interface.
			// TODO: escape analysis.
			sizeValue := llvm.ConstInt(c.uintptrType, size, false)
			itfValue = c.createRuntimeCall("alloc", []llvm.Value{sizeValue}, "")
			itfValueCast := c.builder.CreateBitCast(itfValue, llvm.PointerType(val.Type(), 0), "")
			c.builder.CreateStore(val, itfValueCast)
		}
	} else {
		// Directly place the value in the interface.
		switch val.Type().TypeKind() {
		case llvm.IntegerTypeKind:
			itfValue = c.builder.CreateIntToPtr(val, c.i8ptrType, "")
		case llvm.PointerTypeKind:
			itfValue = c.builder.CreateBitCast(val, c.i8ptrType, "")
		case llvm.StructTypeKind:
			// A bitcast would be useful here, but bitcast doesn't allow
			// aggregate types. So we'll bitcast it using an alloca.
			// Hopefully this will get optimized away.
			mem := c.builder.CreateAlloca(c.i8ptrType, "")
			memStructPtr := c.builder.CreateBitCast(mem, llvm.PointerType(val.Type(), 0), "")
			c.builder.CreateStore(val, memStructPtr)
			itfValue = c.builder.CreateLoad(mem, "")
		default:
			return llvm.Value{}, errors.New("todo: makeinterface: cast small type to i8*")
		}
	}
	itfTypeNum, _ := c.ir.TypeNum(typ)
	if itfTypeNum >= 1<<16 {
		return llvm.Value{}, errors.New("interface typecodes do not fit in a 16-bit integer")
	}
	itf := llvm.ConstNamedStruct(c.mod.GetTypeByName("runtime._interface"), []llvm.Value{llvm.ConstInt(llvm.Int16Type(), uint64(itfTypeNum), false), llvm.Undef(c.i8ptrType)})
	itf = c.builder.CreateInsertValue(itf, itfValue, 1, "")
	return itf, nil
}

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
		if typ, ok := unop.X.Type().Underlying().(*types.Basic); ok {
			if typ.Info()&types.IsInteger != 0 {
				return c.builder.CreateSub(llvm.ConstInt(x.Type(), 0, false), x, ""), nil
			} else if typ.Info()&types.IsFloat != 0 {
				return c.builder.CreateFSub(llvm.ConstFloat(x.Type(), 0.0), x, ""), nil
			} else {
				return llvm.Value{}, errors.New("todo: unknown basic type for negate: " + typ.String())
			}
		} else {
			return llvm.Value{}, errors.New("todo: unknown type for negate: " + unop.X.Type().Underlying().String())
		}
	case token.MUL: // *x, dereference pointer
		valType := unop.X.Type().(*types.Pointer).Elem()
		load := c.builder.CreateLoad(x, "")
		if c.ir.IsVolatile(valType) {
			// Volatile load, for memory-mapped registers.
			load.SetVolatile(true)
		}
		return load, 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) 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()
			llvmFn.SetSection(".text." + name)
		}
		llvmFn = llvm.NextFunction(llvmFn)
	}
}

// Turn all global constants into global variables. This works around a
// limitation on Harvard architectures (e.g. AVR), where constant and
// non-constant pointers point to a different address space.
func (c *Compiler) NonConstGlobals() {
	global := c.mod.FirstGlobal()
	for !global.IsNil() {
		global.SetGlobalConstant(false)
		global = llvm.NextGlobal(global)
	}
}

// Emit object file (.o).
func (c *Compiler) EmitObject(path string) error {
	llvmBuf, err := c.machine.EmitToMemoryBuffer(c.mod, llvm.ObjectFile)
	if err != nil {
		return err
	}
	return c.writeFile(llvmBuf.Bytes(), path)
}

// Emit LLVM bitcode file (.bc).
func (c *Compiler) EmitBitcode(path string) error {
	data := llvm.WriteBitcodeToMemoryBuffer(c.mod).Bytes()
	return c.writeFile(data, path)
}

// Emit LLVM IR source file (.ll).
func (c *Compiler) EmitText(path string) error {
	data := []byte(c.mod.String())
	return c.writeFile(data, path)
}

// Write the data to the file specified by path.
func (c *Compiler) writeFile(data []byte, path string) error {
	// Write output to file
	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
	if err != nil {
		return err
	}
	_, err = f.Write(data)
	if err != nil {
		return err
	}
	return f.Close()
}