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|
package compiler
// This file transforms interface-related instructions (*ssa.MakeInterface,
// *ssa.TypeAssert, calls on interface types) to an intermediate IR form, to be
// lowered to the final form by the interface lowering pass. See
// interface-lowering.go for more details.
import (
"encoding/binary"
"fmt"
"go/token"
"go/types"
"strconv"
"strings"
"golang.org/x/tools/go/ssa"
"tinygo.org/x/go-llvm"
)
// Type kinds for basic types.
// They must match the constants for the Kind type in src/reflect/type.go.
var basicTypes = [...]uint8{
types.Bool: 1,
types.Int: 2,
types.Int8: 3,
types.Int16: 4,
types.Int32: 5,
types.Int64: 6,
types.Uint: 7,
types.Uint8: 8,
types.Uint16: 9,
types.Uint32: 10,
types.Uint64: 11,
types.Uintptr: 12,
types.Float32: 13,
types.Float64: 14,
types.Complex64: 15,
types.Complex128: 16,
types.String: 17,
types.UnsafePointer: 18,
}
// These must also match the constants for the Kind type in src/reflect/type.go.
const (
typeKindChan = 19
typeKindInterface = 20
typeKindPointer = 21
typeKindSlice = 22
typeKindArray = 23
typeKindSignature = 24
typeKindMap = 25
typeKindStruct = 26
)
// Flags stored in the first byte of the struct field byte array. Must be kept
// up to date with src/reflect/type.go.
const (
structFieldFlagAnonymous = 1 << iota
structFieldFlagHasTag
structFieldFlagIsExported
structFieldFlagIsEmbedded
)
type reflectChanDir int
const (
refRecvDir reflectChanDir = 1 << iota // <-chan
refSendDir // chan<-
refBothDir = refRecvDir | refSendDir // chan
)
// createMakeInterface emits the LLVM IR for the *ssa.MakeInterface instruction.
// It tries to put the type in the interface value, but if that's not possible,
// it will do an allocation of the right size and put that in the interface
// value field.
//
// An interface value is a {typecode, value} tuple named runtime._interface.
func (b *builder) createMakeInterface(val llvm.Value, typ types.Type, pos token.Pos) llvm.Value {
itfValue := b.emitPointerPack([]llvm.Value{val})
itfType := b.getTypeCode(typ)
itf := llvm.Undef(b.getLLVMRuntimeType("_interface"))
itf = b.CreateInsertValue(itf, itfType, 0, "")
itf = b.CreateInsertValue(itf, itfValue, 1, "")
return itf
}
// extractValueFromInterface extract the value from an interface value
// (runtime._interface) under the assumption that it is of the type given in
// llvmType. The behavior is undefined if the interface is nil or llvmType
// doesn't match the underlying type of the interface.
func (b *builder) extractValueFromInterface(itf llvm.Value, llvmType llvm.Type) llvm.Value {
valuePtr := b.CreateExtractValue(itf, 1, "typeassert.value.ptr")
return b.emitPointerUnpack(valuePtr, []llvm.Type{llvmType})[0]
}
func (c *compilerContext) pkgPathPtr(pkgpath string) llvm.Value {
pkgpathName := "reflect/types.type.pkgpath.empty"
if pkgpath != "" {
pkgpathName = "reflect/types.type.pkgpath:" + pkgpath
}
pkgpathGlobal := c.mod.NamedGlobal(pkgpathName)
if pkgpathGlobal.IsNil() {
pkgpathInitializer := c.ctx.ConstString(pkgpath+"\x00", false)
pkgpathGlobal = llvm.AddGlobal(c.mod, pkgpathInitializer.Type(), pkgpathName)
pkgpathGlobal.SetInitializer(pkgpathInitializer)
pkgpathGlobal.SetAlignment(1)
pkgpathGlobal.SetUnnamedAddr(true)
pkgpathGlobal.SetLinkage(llvm.LinkOnceODRLinkage)
pkgpathGlobal.SetGlobalConstant(true)
}
pkgPathPtr := llvm.ConstGEP(pkgpathGlobal.GlobalValueType(), pkgpathGlobal, []llvm.Value{
llvm.ConstInt(c.ctx.Int32Type(), 0, false),
llvm.ConstInt(c.ctx.Int32Type(), 0, false),
})
return pkgPathPtr
}
// getTypeCode returns a reference to a type code.
// A type code is a pointer to a constant global that describes the type.
// This function returns a pointer to the 'kind' field (which might not be the
// first field in the struct).
func (c *compilerContext) getTypeCode(typ types.Type) llvm.Value {
ms := c.program.MethodSets.MethodSet(typ)
hasMethodSet := ms.Len() != 0
_, isInterface := typ.Underlying().(*types.Interface)
if isInterface {
hasMethodSet = false
}
// As defined in https://pkg.go.dev/reflect#Type:
// NumMethod returns the number of methods accessible using Method.
// For a non-interface type, it returns the number of exported methods.
// For an interface type, it returns the number of exported and unexported methods.
var numMethods int
for i := 0; i < ms.Len(); i++ {
if isInterface || ms.At(i).Obj().Exported() {
numMethods++
}
}
// Short-circuit all the global pointer logic here for pointers to pointers.
if typ, ok := typ.(*types.Pointer); ok {
if _, ok := typ.Elem().(*types.Pointer); ok {
// For a pointer to a pointer, we just increase the pointer by 1
ptr := c.getTypeCode(typ.Elem())
// if the type is already *****T or higher, we can't make it.
if typstr := typ.String(); strings.HasPrefix(typstr, "*****") {
c.addError(token.NoPos, fmt.Sprintf("too many levels of pointers for typecode: %s", typstr))
}
return llvm.ConstGEP(c.ctx.Int8Type(), ptr, []llvm.Value{
llvm.ConstInt(c.ctx.Int32Type(), 1, false),
})
}
}
typeCodeName, isLocal := getTypeCodeName(typ)
globalName := "reflect/types.type:" + typeCodeName
var global llvm.Value
if isLocal {
// This type is a named type inside a function, like this:
//
// func foo() any {
// type named int
// return named(0)
// }
if obj := c.interfaceTypes.At(typ); obj != nil {
global = obj.(llvm.Value)
}
} else {
// Regular type (named or otherwise).
global = c.mod.NamedGlobal(globalName)
}
if global.IsNil() {
var typeFields []llvm.Value
// Define the type fields. These must match the structs in
// src/reflect/type.go (ptrType, arrayType, etc). See the comment at the
// top of src/reflect/type.go for more information on the layout of these structs.
typeFieldTypes := []*types.Var{
types.NewVar(token.NoPos, nil, "kind", types.Typ[types.Int8]),
}
switch typ := typ.(type) {
case *types.Basic:
typeFieldTypes = append(typeFieldTypes,
types.NewVar(token.NoPos, nil, "ptrTo", types.Typ[types.UnsafePointer]),
)
case *types.Named:
name := typ.Obj().Name()
var pkgname string
if pkg := typ.Obj().Pkg(); pkg != nil {
pkgname = pkg.Name()
}
typeFieldTypes = append(typeFieldTypes,
types.NewVar(token.NoPos, nil, "numMethods", types.Typ[types.Uint16]),
types.NewVar(token.NoPos, nil, "ptrTo", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "underlying", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "pkgpath", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "name", types.NewArray(types.Typ[types.Int8], int64(len(pkgname)+1+len(name)+1))),
)
case *types.Chan:
typeFieldTypes = append(typeFieldTypes,
types.NewVar(token.NoPos, nil, "numMethods", types.Typ[types.Uint16]), // reuse for select chan direction
types.NewVar(token.NoPos, nil, "ptrTo", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "elementType", types.Typ[types.UnsafePointer]),
)
case *types.Slice:
typeFieldTypes = append(typeFieldTypes,
types.NewVar(token.NoPos, nil, "numMethods", types.Typ[types.Uint16]),
types.NewVar(token.NoPos, nil, "ptrTo", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "elementType", types.Typ[types.UnsafePointer]),
)
case *types.Pointer:
typeFieldTypes = append(typeFieldTypes,
types.NewVar(token.NoPos, nil, "numMethods", types.Typ[types.Uint16]),
types.NewVar(token.NoPos, nil, "elementType", types.Typ[types.UnsafePointer]),
)
case *types.Array:
typeFieldTypes = append(typeFieldTypes,
types.NewVar(token.NoPos, nil, "numMethods", types.Typ[types.Uint16]),
types.NewVar(token.NoPos, nil, "ptrTo", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "elementType", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "length", types.Typ[types.Uintptr]),
types.NewVar(token.NoPos, nil, "sliceOf", types.Typ[types.UnsafePointer]),
)
case *types.Map:
typeFieldTypes = append(typeFieldTypes,
types.NewVar(token.NoPos, nil, "numMethods", types.Typ[types.Uint16]),
types.NewVar(token.NoPos, nil, "ptrTo", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "elementType", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "keyType", types.Typ[types.UnsafePointer]),
)
case *types.Struct:
typeFieldTypes = append(typeFieldTypes,
types.NewVar(token.NoPos, nil, "numMethods", types.Typ[types.Uint16]),
types.NewVar(token.NoPos, nil, "ptrTo", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "pkgpath", types.Typ[types.UnsafePointer]),
types.NewVar(token.NoPos, nil, "size", types.Typ[types.Uint32]),
types.NewVar(token.NoPos, nil, "numFields", types.Typ[types.Uint16]),
types.NewVar(token.NoPos, nil, "fields", types.NewArray(c.getRuntimeType("structField"), int64(typ.NumFields()))),
)
case *types.Interface:
typeFieldTypes = append(typeFieldTypes,
types.NewVar(token.NoPos, nil, "ptrTo", types.Typ[types.UnsafePointer]),
)
// TODO: methods
case *types.Signature:
typeFieldTypes = append(typeFieldTypes,
types.NewVar(token.NoPos, nil, "ptrTo", types.Typ[types.UnsafePointer]),
)
// TODO: signature params and return values
}
if hasMethodSet {
// This method set is appended at the start of the struct. It is
// removed in the interface lowering pass.
// TODO: don't remove these and instead do what upstream Go is doing
// instead. See: https://research.swtch.com/interfaces. This can
// likely be optimized in LLVM using
// https://llvm.org/docs/TypeMetadata.html.
typeFieldTypes = append([]*types.Var{
types.NewVar(token.NoPos, nil, "methodSet", types.Typ[types.UnsafePointer]),
}, typeFieldTypes...)
}
globalType := types.NewStruct(typeFieldTypes, nil)
global = llvm.AddGlobal(c.mod, c.getLLVMType(globalType), globalName)
if isLocal {
c.interfaceTypes.Set(typ, global)
}
metabyte := getTypeKind(typ)
// Precompute these so we don't have to calculate them at runtime.
if types.Comparable(typ) {
metabyte |= 1 << 6
}
if hashmapIsBinaryKey(typ) {
metabyte |= 1 << 7
}
switch typ := typ.(type) {
case *types.Basic:
typeFields = []llvm.Value{c.getTypeCode(types.NewPointer(typ))}
case *types.Named:
name := typ.Obj().Name()
var pkgpath string
var pkgname string
if pkg := typ.Obj().Pkg(); pkg != nil {
pkgpath = pkg.Path()
pkgname = pkg.Name()
}
pkgPathPtr := c.pkgPathPtr(pkgpath)
typeFields = []llvm.Value{
llvm.ConstInt(c.ctx.Int16Type(), uint64(numMethods), false), // numMethods
c.getTypeCode(types.NewPointer(typ)), // ptrTo
c.getTypeCode(typ.Underlying()), // underlying
pkgPathPtr, // pkgpath pointer
c.ctx.ConstString(pkgname+"."+name+"\x00", false), // name
}
metabyte |= 1 << 5 // "named" flag
case *types.Chan:
var dir reflectChanDir
switch typ.Dir() {
case types.SendRecv:
dir = refBothDir
case types.RecvOnly:
dir = refRecvDir
case types.SendOnly:
dir = refSendDir
}
typeFields = []llvm.Value{
llvm.ConstInt(c.ctx.Int16Type(), uint64(dir), false), // actually channel direction
c.getTypeCode(types.NewPointer(typ)), // ptrTo
c.getTypeCode(typ.Elem()), // elementType
}
case *types.Slice:
typeFields = []llvm.Value{
llvm.ConstInt(c.ctx.Int16Type(), 0, false), // numMethods
c.getTypeCode(types.NewPointer(typ)), // ptrTo
c.getTypeCode(typ.Elem()), // elementType
}
case *types.Pointer:
typeFields = []llvm.Value{
llvm.ConstInt(c.ctx.Int16Type(), uint64(numMethods), false), // numMethods
c.getTypeCode(typ.Elem()),
}
case *types.Array:
typeFields = []llvm.Value{
llvm.ConstInt(c.ctx.Int16Type(), 0, false), // numMethods
c.getTypeCode(types.NewPointer(typ)), // ptrTo
c.getTypeCode(typ.Elem()), // elementType
llvm.ConstInt(c.uintptrType, uint64(typ.Len()), false), // length
c.getTypeCode(types.NewSlice(typ.Elem())), // slicePtr
}
case *types.Map:
typeFields = []llvm.Value{
llvm.ConstInt(c.ctx.Int16Type(), 0, false), // numMethods
c.getTypeCode(types.NewPointer(typ)), // ptrTo
c.getTypeCode(typ.Elem()), // elem
c.getTypeCode(typ.Key()), // key
}
case *types.Struct:
var pkgpath string
if typ.NumFields() > 0 {
if pkg := typ.Field(0).Pkg(); pkg != nil {
pkgpath = pkg.Path()
}
}
pkgPathPtr := c.pkgPathPtr(pkgpath)
llvmStructType := c.getLLVMType(typ)
size := c.targetData.TypeStoreSize(llvmStructType)
typeFields = []llvm.Value{
llvm.ConstInt(c.ctx.Int16Type(), uint64(numMethods), false), // numMethods
c.getTypeCode(types.NewPointer(typ)), // ptrTo
pkgPathPtr,
llvm.ConstInt(c.ctx.Int32Type(), uint64(size), false), // size
llvm.ConstInt(c.ctx.Int16Type(), uint64(typ.NumFields()), false), // numFields
}
structFieldType := c.getLLVMRuntimeType("structField")
var fields []llvm.Value
for i := 0; i < typ.NumFields(); i++ {
field := typ.Field(i)
offset := c.targetData.ElementOffset(llvmStructType, i)
var flags uint8
if field.Anonymous() {
flags |= structFieldFlagAnonymous
}
if typ.Tag(i) != "" {
flags |= structFieldFlagHasTag
}
if token.IsExported(field.Name()) {
flags |= structFieldFlagIsExported
}
if field.Embedded() {
flags |= structFieldFlagIsEmbedded
}
var offsBytes [binary.MaxVarintLen32]byte
offLen := binary.PutUvarint(offsBytes[:], offset)
data := string(flags) + string(offsBytes[:offLen]) + field.Name() + "\x00"
if typ.Tag(i) != "" {
if len(typ.Tag(i)) > 0xff {
c.addError(field.Pos(), fmt.Sprintf("struct tag is %d bytes which is too long, max is 255", len(typ.Tag(i))))
}
data += string([]byte{byte(len(typ.Tag(i)))}) + typ.Tag(i)
}
dataInitializer := c.ctx.ConstString(data, false)
dataGlobal := llvm.AddGlobal(c.mod, dataInitializer.Type(), globalName+"."+field.Name())
dataGlobal.SetInitializer(dataInitializer)
dataGlobal.SetAlignment(1)
dataGlobal.SetUnnamedAddr(true)
dataGlobal.SetLinkage(llvm.InternalLinkage)
dataGlobal.SetGlobalConstant(true)
fieldType := c.getTypeCode(field.Type())
fields = append(fields, llvm.ConstNamedStruct(structFieldType, []llvm.Value{
fieldType,
llvm.ConstGEP(dataGlobal.GlobalValueType(), dataGlobal, []llvm.Value{
llvm.ConstInt(c.ctx.Int32Type(), 0, false),
llvm.ConstInt(c.ctx.Int32Type(), 0, false),
}),
}))
}
typeFields = append(typeFields, llvm.ConstArray(structFieldType, fields))
case *types.Interface:
typeFields = []llvm.Value{c.getTypeCode(types.NewPointer(typ))}
// TODO: methods
case *types.Signature:
typeFields = []llvm.Value{c.getTypeCode(types.NewPointer(typ))}
// TODO: params, return values, etc
}
// Prepend metadata byte.
typeFields = append([]llvm.Value{
llvm.ConstInt(c.ctx.Int8Type(), uint64(metabyte), false),
}, typeFields...)
if hasMethodSet {
typeFields = append([]llvm.Value{
c.getTypeMethodSet(typ),
}, typeFields...)
}
alignment := c.targetData.TypeAllocSize(c.dataPtrType)
if alignment < 4 {
alignment = 4
}
globalValue := c.ctx.ConstStruct(typeFields, false)
global.SetInitializer(globalValue)
if isLocal {
global.SetLinkage(llvm.InternalLinkage)
} else {
global.SetLinkage(llvm.LinkOnceODRLinkage)
}
global.SetGlobalConstant(true)
global.SetAlignment(int(alignment))
if c.Debug {
file := c.getDIFile("<Go type>")
diglobal := c.dibuilder.CreateGlobalVariableExpression(file, llvm.DIGlobalVariableExpression{
Name: "type " + typ.String(),
File: file,
Line: 1,
Type: c.getDIType(globalType),
LocalToUnit: false,
Expr: c.dibuilder.CreateExpression(nil),
AlignInBits: uint32(alignment * 8),
})
global.AddMetadata(0, diglobal)
}
}
offset := uint64(0)
if hasMethodSet {
// The pointer to the method set is always the first element of the
// global (if there is a method set). However, the pointer we return
// should point to the 'kind' field not the method set.
offset = 1
}
return llvm.ConstGEP(global.GlobalValueType(), global, []llvm.Value{
llvm.ConstInt(c.ctx.Int32Type(), 0, false),
llvm.ConstInt(c.ctx.Int32Type(), offset, false),
})
}
// getTypeKind returns the type kind for the given type, as defined by
// reflect.Kind.
func getTypeKind(t types.Type) uint8 {
switch t := t.Underlying().(type) {
case *types.Basic:
return basicTypes[t.Kind()]
case *types.Chan:
return typeKindChan
case *types.Interface:
return typeKindInterface
case *types.Pointer:
return typeKindPointer
case *types.Slice:
return typeKindSlice
case *types.Array:
return typeKindArray
case *types.Signature:
return typeKindSignature
case *types.Map:
return typeKindMap
case *types.Struct:
return typeKindStruct
default:
panic("unknown type")
}
}
var basicTypeNames = [...]string{
types.Bool: "bool",
types.Int: "int",
types.Int8: "int8",
types.Int16: "int16",
types.Int32: "int32",
types.Int64: "int64",
types.Uint: "uint",
types.Uint8: "uint8",
types.Uint16: "uint16",
types.Uint32: "uint32",
types.Uint64: "uint64",
types.Uintptr: "uintptr",
types.Float32: "float32",
types.Float64: "float64",
types.Complex64: "complex64",
types.Complex128: "complex128",
types.String: "string",
types.UnsafePointer: "unsafe.Pointer",
}
// getTypeCodeName returns a name for this type that can be used in the
// interface lowering pass to assign type codes as expected by the reflect
// package. See getTypeCodeNum.
func getTypeCodeName(t types.Type) (string, bool) {
switch t := t.(type) {
case *types.Named:
if t.Obj().Parent() != t.Obj().Pkg().Scope() {
return "named:" + t.String() + "$local", true
}
return "named:" + t.String(), false
case *types.Array:
s, isLocal := getTypeCodeName(t.Elem())
return "array:" + strconv.FormatInt(t.Len(), 10) + ":" + s, isLocal
case *types.Basic:
return "basic:" + basicTypeNames[t.Kind()], false
case *types.Chan:
s, isLocal := getTypeCodeName(t.Elem())
var dir string
switch t.Dir() {
case types.SendOnly:
dir = "s:"
case types.RecvOnly:
dir = "r:"
case types.SendRecv:
dir = "sr:"
}
return "chan:" + dir + s, isLocal
case *types.Interface:
isLocal := false
methods := make([]string, t.NumMethods())
for i := 0; i < t.NumMethods(); i++ {
name := t.Method(i).Name()
if !token.IsExported(name) {
name = t.Method(i).Pkg().Path() + "." + name
}
s, local := getTypeCodeName(t.Method(i).Type())
if local {
isLocal = true
}
methods[i] = name + ":" + s
}
return "interface:" + "{" + strings.Join(methods, ",") + "}", isLocal
case *types.Map:
keyType, keyLocal := getTypeCodeName(t.Key())
elemType, elemLocal := getTypeCodeName(t.Elem())
return "map:" + "{" + keyType + "," + elemType + "}", keyLocal || elemLocal
case *types.Pointer:
s, isLocal := getTypeCodeName(t.Elem())
return "pointer:" + s, isLocal
case *types.Signature:
isLocal := false
params := make([]string, t.Params().Len())
for i := 0; i < t.Params().Len(); i++ {
s, local := getTypeCodeName(t.Params().At(i).Type())
if local {
isLocal = true
}
params[i] = s
}
results := make([]string, t.Results().Len())
for i := 0; i < t.Results().Len(); i++ {
s, local := getTypeCodeName(t.Results().At(i).Type())
if local {
isLocal = true
}
results[i] = s
}
return "func:" + "{" + strings.Join(params, ",") + "}{" + strings.Join(results, ",") + "}", isLocal
case *types.Slice:
s, isLocal := getTypeCodeName(t.Elem())
return "slice:" + s, isLocal
case *types.Struct:
elems := make([]string, t.NumFields())
isLocal := false
for i := 0; i < t.NumFields(); i++ {
embedded := ""
if t.Field(i).Embedded() {
embedded = "#"
}
s, local := getTypeCodeName(t.Field(i).Type())
if local {
isLocal = true
}
elems[i] = embedded + t.Field(i).Name() + ":" + s
if t.Tag(i) != "" {
elems[i] += "`" + t.Tag(i) + "`"
}
}
return "struct:" + "{" + strings.Join(elems, ",") + "}", isLocal
default:
panic("unknown type: " + t.String())
}
}
// getTypeMethodSet returns a reference (GEP) to a global method set. This
// method set should be unreferenced after the interface lowering pass.
func (c *compilerContext) getTypeMethodSet(typ types.Type) llvm.Value {
globalName := typ.String() + "$methodset"
global := c.mod.NamedGlobal(globalName)
if global.IsNil() {
ms := c.program.MethodSets.MethodSet(typ)
// Create method set.
var signatures, wrappers []llvm.Value
for i := 0; i < ms.Len(); i++ {
method := ms.At(i)
signatureGlobal := c.getMethodSignature(method.Obj().(*types.Func))
signatures = append(signatures, signatureGlobal)
fn := c.program.MethodValue(method)
llvmFnType, llvmFn := c.getFunction(fn)
if llvmFn.IsNil() {
// compiler error, so panic
panic("cannot find function: " + c.getFunctionInfo(fn).linkName)
}
wrapper := c.getInterfaceInvokeWrapper(fn, llvmFnType, llvmFn)
wrappers = append(wrappers, wrapper)
}
// Construct global value.
globalValue := c.ctx.ConstStruct([]llvm.Value{
llvm.ConstInt(c.uintptrType, uint64(ms.Len()), false),
llvm.ConstArray(c.dataPtrType, signatures),
c.ctx.ConstStruct(wrappers, false),
}, false)
global = llvm.AddGlobal(c.mod, globalValue.Type(), globalName)
global.SetInitializer(globalValue)
global.SetGlobalConstant(true)
global.SetUnnamedAddr(true)
global.SetLinkage(llvm.LinkOnceODRLinkage)
}
return global
}
// getMethodSignatureName returns a unique name (that can be used as the name of
// a global) for the given method.
func (c *compilerContext) getMethodSignatureName(method *types.Func) string {
signature := methodSignature(method)
var globalName string
if token.IsExported(method.Name()) {
globalName = "reflect/methods." + signature
} else {
globalName = method.Type().(*types.Signature).Recv().Pkg().Path() + ".$methods." + signature
}
return globalName
}
// getMethodSignature returns a global variable which is a reference to an
// external *i8 indicating the indicating the signature of this method. It is
// used during the interface lowering pass.
func (c *compilerContext) getMethodSignature(method *types.Func) llvm.Value {
globalName := c.getMethodSignatureName(method)
signatureGlobal := c.mod.NamedGlobal(globalName)
if signatureGlobal.IsNil() {
// TODO: put something useful in these globals, such as the method
// signature. Useful to one day implement reflect.Value.Method(n).
signatureGlobal = llvm.AddGlobal(c.mod, c.ctx.Int8Type(), globalName)
signatureGlobal.SetInitializer(llvm.ConstInt(c.ctx.Int8Type(), 0, false))
signatureGlobal.SetLinkage(llvm.LinkOnceODRLinkage)
signatureGlobal.SetGlobalConstant(true)
signatureGlobal.SetAlignment(1)
}
return signatureGlobal
}
// createTypeAssert will emit the code for a typeassert, used in if statements
// and in type switches (Go SSA does not have type switches, only if/else
// chains). Note that even though the Go SSA does not contain type switches,
// LLVM will recognize the pattern and make it a real switch in many cases.
//
// Type asserts on concrete types are trivial: just compare type numbers. Type
// asserts on interfaces are more difficult, see the comments in the function.
func (b *builder) createTypeAssert(expr *ssa.TypeAssert) llvm.Value {
itf := b.getValue(expr.X, getPos(expr))
assertedType := b.getLLVMType(expr.AssertedType)
actualTypeNum := b.CreateExtractValue(itf, 0, "interface.type")
commaOk := llvm.Value{}
if intf, ok := expr.AssertedType.Underlying().(*types.Interface); ok {
if intf.Empty() {
// intf is the empty interface => no methods
// This type assertion always succeeds, so we can just set commaOk to true.
commaOk = llvm.ConstInt(b.ctx.Int1Type(), 1, true)
} else {
// Type assert on interface type with methods.
// This is a call to an interface type assert function.
// The interface lowering pass will define this function by filling it
// with a type switch over all concrete types that implement this
// interface, and returning whether it's one of the matched types.
// This is very different from how interface asserts are implemented in
// the main Go compiler, where the runtime checks whether the type
// implements each method of the interface. See:
// https://research.swtch.com/interfaces
fn := b.getInterfaceImplementsFunc(expr.AssertedType)
commaOk = b.CreateCall(fn.GlobalValueType(), fn, []llvm.Value{actualTypeNum}, "")
}
} else {
name, _ := getTypeCodeName(expr.AssertedType)
globalName := "reflect/types.typeid:" + name
assertedTypeCodeGlobal := b.mod.NamedGlobal(globalName)
if assertedTypeCodeGlobal.IsNil() {
// Create a new typecode global.
assertedTypeCodeGlobal = llvm.AddGlobal(b.mod, b.ctx.Int8Type(), globalName)
assertedTypeCodeGlobal.SetGlobalConstant(true)
}
// Type assert on concrete type.
// Call runtime.typeAssert, which will be lowered to a simple icmp or
// const false in the interface lowering pass.
commaOk = b.createRuntimeCall("typeAssert", []llvm.Value{actualTypeNum, assertedTypeCodeGlobal}, "typecode")
}
// 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 := b.GetInsertBlock()
okBlock := b.insertBasicBlock("typeassert.ok")
nextBlock := b.insertBasicBlock("typeassert.next")
b.blockExits[b.currentBlock] = nextBlock // adjust outgoing block for phi nodes
b.CreateCondBr(commaOk, okBlock, nextBlock)
// Retrieve the value from the interface if the type assert was
// successful.
b.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).
valueOk = b.extractValueFromInterface(itf, assertedType)
}
b.CreateBr(nextBlock)
// Continue after the if statement.
b.SetInsertPointAtEnd(nextBlock)
phi := b.CreatePHI(assertedType, "typeassert.value")
phi.AddIncoming([]llvm.Value{llvm.ConstNull(assertedType), valueOk}, []llvm.BasicBlock{prevBlock, okBlock})
if expr.CommaOk {
tuple := b.ctx.ConstStruct([]llvm.Value{llvm.Undef(assertedType), llvm.Undef(b.ctx.Int1Type())}, false) // create empty tuple
tuple = b.CreateInsertValue(tuple, phi, 0, "") // insert value
tuple = b.CreateInsertValue(tuple, commaOk, 1, "") // insert 'comma ok' boolean
return tuple
} else {
// This is kind of dirty as the branch above becomes mostly useless,
// but hopefully this gets optimized away.
b.createRuntimeCall("interfaceTypeAssert", []llvm.Value{commaOk}, "")
return phi
}
}
// getMethodsString returns a string to be used in the "tinygo-methods" string
// attribute for interface functions.
func (c *compilerContext) getMethodsString(itf *types.Interface) string {
methods := make([]string, itf.NumMethods())
for i := range methods {
methods[i] = c.getMethodSignatureName(itf.Method(i))
}
return strings.Join(methods, "; ")
}
// getInterfaceImplementsFunc returns a declared function that works as a type
// switch. The interface lowering pass will define this function.
func (c *compilerContext) getInterfaceImplementsFunc(assertedType types.Type) llvm.Value {
s, _ := getTypeCodeName(assertedType.Underlying())
fnName := s + ".$typeassert"
llvmFn := c.mod.NamedFunction(fnName)
if llvmFn.IsNil() {
llvmFnType := llvm.FunctionType(c.ctx.Int1Type(), []llvm.Type{c.dataPtrType}, false)
llvmFn = llvm.AddFunction(c.mod, fnName, llvmFnType)
c.addStandardDeclaredAttributes(llvmFn)
methods := c.getMethodsString(assertedType.Underlying().(*types.Interface))
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("tinygo-methods", methods))
}
return llvmFn
}
// getInvokeFunction returns the thunk to call the given interface method. The
// thunk is declared, not defined: it will be defined by the interface lowering
// pass.
func (c *compilerContext) getInvokeFunction(instr *ssa.CallCommon) llvm.Value {
s, _ := getTypeCodeName(instr.Value.Type().Underlying())
fnName := s + "." + instr.Method.Name() + "$invoke"
llvmFn := c.mod.NamedFunction(fnName)
if llvmFn.IsNil() {
sig := instr.Method.Type().(*types.Signature)
var paramTuple []*types.Var
for i := 0; i < sig.Params().Len(); i++ {
paramTuple = append(paramTuple, sig.Params().At(i))
}
paramTuple = append(paramTuple, types.NewVar(token.NoPos, nil, "$typecode", types.Typ[types.UnsafePointer]))
llvmFnType := c.getLLVMFunctionType(types.NewSignature(sig.Recv(), types.NewTuple(paramTuple...), sig.Results(), false))
llvmFn = llvm.AddFunction(c.mod, fnName, llvmFnType)
c.addStandardDeclaredAttributes(llvmFn)
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("tinygo-invoke", c.getMethodSignatureName(instr.Method)))
methods := c.getMethodsString(instr.Value.Type().Underlying().(*types.Interface))
llvmFn.AddFunctionAttr(c.ctx.CreateStringAttribute("tinygo-methods", methods))
}
return llvmFn
}
// getInterfaceInvokeWrapper returns a wrapper for the given method so it can be
// invoked from an interface. The wrapper takes in a pointer to the underlying
// value, dereferences or unpacks it if necessary, and calls the real method.
// If the method to wrap has a pointer receiver, no wrapping is necessary and
// the function is returned directly.
func (c *compilerContext) getInterfaceInvokeWrapper(fn *ssa.Function, llvmFnType llvm.Type, llvmFn llvm.Value) llvm.Value {
wrapperName := llvmFn.Name() + "$invoke"
wrapper := c.mod.NamedFunction(wrapperName)
if !wrapper.IsNil() {
// Wrapper already created. Return it directly.
return wrapper
}
// Get the expanded receiver type.
receiverType := c.getLLVMType(fn.Signature.Recv().Type())
var expandedReceiverType []llvm.Type
for _, info := range c.expandFormalParamType(receiverType, "", nil) {
expandedReceiverType = append(expandedReceiverType, info.llvmType)
}
// Does this method even need any wrapping?
if len(expandedReceiverType) == 1 && receiverType.TypeKind() == llvm.PointerTypeKind {
// Nothing to wrap.
// Casting a function signature to a different signature and calling it
// with a receiver pointer bitcasted to *i8 (as done in calls on an
// interface) is hopefully a safe (defined) operation.
return llvmFn
}
// create wrapper function
paramTypes := append([]llvm.Type{c.dataPtrType}, llvmFnType.ParamTypes()[len(expandedReceiverType):]...)
wrapFnType := llvm.FunctionType(llvmFnType.ReturnType(), paramTypes, false)
wrapper = llvm.AddFunction(c.mod, wrapperName, wrapFnType)
c.addStandardAttributes(wrapper)
wrapper.SetLinkage(llvm.LinkOnceODRLinkage)
wrapper.SetUnnamedAddr(true)
// Create a new builder just to create this wrapper.
b := builder{
compilerContext: c,
Builder: c.ctx.NewBuilder(),
}
defer b.Builder.Dispose()
// add debug info if needed
if c.Debug {
pos := c.program.Fset.Position(fn.Pos())
difunc := c.attachDebugInfoRaw(fn, wrapper, "$invoke", pos.Filename, pos.Line)
b.SetCurrentDebugLocation(uint(pos.Line), uint(pos.Column), difunc, llvm.Metadata{})
}
// set up IR builder
block := b.ctx.AddBasicBlock(wrapper, "entry")
b.SetInsertPointAtEnd(block)
receiverValue := b.emitPointerUnpack(wrapper.Param(0), []llvm.Type{receiverType})[0]
params := append(b.expandFormalParam(receiverValue), wrapper.Params()[1:]...)
if llvmFnType.ReturnType().TypeKind() == llvm.VoidTypeKind {
b.CreateCall(llvmFnType, llvmFn, params, "")
b.CreateRetVoid()
} else {
ret := b.CreateCall(llvmFnType, llvmFn, params, "ret")
b.CreateRet(ret)
}
return wrapper
}
// methodSignature creates a readable version of a method signature (including
// the function name, excluding the receiver name). This string is used
// internally to match interfaces and to call the correct method on an
// interface. Examples:
//
// String() string
// Read([]byte) (int, error)
func methodSignature(method *types.Func) string {
return method.Name() + signature(method.Type().(*types.Signature))
}
// Make a readable version of a function (pointer) signature.
// Examples:
//
// () string
// (string, int) (int, error)
func signature(sig *types.Signature) string {
s := ""
if sig.Params().Len() == 0 {
s += "()"
} else {
s += "("
for i := 0; i < sig.Params().Len(); i++ {
if i > 0 {
s += ", "
}
s += typestring(sig.Params().At(i).Type())
}
s += ")"
}
if sig.Results().Len() == 0 {
// keep as-is
} else if sig.Results().Len() == 1 {
s += " " + typestring(sig.Results().At(0).Type())
} else {
s += " ("
for i := 0; i < sig.Results().Len(); i++ {
if i > 0 {
s += ", "
}
s += typestring(sig.Results().At(i).Type())
}
s += ")"
}
return s
}
// typestring returns a stable (human-readable) type string for the given type
// that can be used for interface equality checks. It is almost (but not
// exactly) the same as calling t.String(). The main difference is some
// normalization around `byte` vs `uint8` for example.
func typestring(t types.Type) string {
// See: https://github.com/golang/go/blob/master/src/go/types/typestring.go
switch t := t.(type) {
case *types.Array:
return "[" + strconv.FormatInt(t.Len(), 10) + "]" + typestring(t.Elem())
case *types.Basic:
return basicTypeNames[t.Kind()]
case *types.Chan:
switch t.Dir() {
case types.SendRecv:
return "chan (" + typestring(t.Elem()) + ")"
case types.SendOnly:
return "chan<- (" + typestring(t.Elem()) + ")"
case types.RecvOnly:
return "<-chan (" + typestring(t.Elem()) + ")"
default:
panic("unknown channel direction")
}
case *types.Interface:
methods := make([]string, t.NumMethods())
for i := range methods {
method := t.Method(i)
methods[i] = method.Name() + signature(method.Type().(*types.Signature))
}
return "interface{" + strings.Join(methods, ";") + "}"
case *types.Map:
return "map[" + typestring(t.Key()) + "]" + typestring(t.Elem())
case *types.Named:
return t.String()
case *types.Pointer:
return "*" + typestring(t.Elem())
case *types.Signature:
return "func" + signature(t)
case *types.Slice:
return "[]" + typestring(t.Elem())
case *types.Struct:
fields := make([]string, t.NumFields())
for i := range fields {
field := t.Field(i)
fields[i] = field.Name() + " " + typestring(field.Type())
if tag := t.Tag(i); tag != "" {
fields[i] += " " + strconv.Quote(tag)
}
}
return "struct{" + strings.Join(fields, ";") + "}"
default:
panic("unknown type: " + t.String())
}
}
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