neoneo-go/pkg/vm/compiler/codegen.go

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package compiler
import (
"bytes"
"encoding/binary"
"go/ast"
"go/constant"
"go/token"
"go/types"
"log"
"github.com/CityOfZion/neo-go/pkg/vm"
)
const mainIdent = "Main"
type codegen struct {
// Information about the program with all its dependencies.
buildInfo *buildInfo
// prog holds the output buffer
prog *bytes.Buffer
// Type information
typeInfo *types.Info
// A mapping of func identifiers with their scope.
funcs map[string]*funcScope
// Current funcScope being converted.
scope *funcScope
// Label table for recording jump destinations.
l []int
}
// newLabel creates a new label to jump to
func (c *codegen) newLabel() (l int) {
l = len(c.l)
c.l = append(c.l, -1)
return
}
func (c *codegen) setLabel(l int) {
c.l[l] = c.pc() + 1
}
// pc return the program offset off the last instruction.
func (c *codegen) pc() int {
return c.prog.Len() - 1
}
func (c *codegen) emitLoadConst(t types.TypeAndValue) {
switch typ := t.Type.Underlying().(type) {
case *types.Basic:
switch typ.Kind() {
case types.Int, types.UntypedInt:
val, _ := constant.Int64Val(t.Value)
emitInt(c.prog, val)
case types.String, types.UntypedString:
val := constant.StringVal(t.Value)
emitString(c.prog, val)
case types.Bool, types.UntypedBool:
val := constant.BoolVal(t.Value)
emitBool(c.prog, val)
case types.Byte:
val, _ := constant.Int64Val(t.Value)
b := byte(val)
emitBytes(c.prog, []byte{b})
default:
log.Fatalf("compiler don't know how to convert this basic type: %v", t)
}
default:
log.Fatalf("compiler don't know how to convert this constant: %v", t)
}
}
func (c *codegen) emitLoadLocal(name string) {
pos := c.scope.loadLocal(name)
if pos < 0 {
log.Fatalf("cannot load local variable with position: %d", pos)
}
emitOpcode(c.prog, vm.Ofromaltstack)
emitOpcode(c.prog, vm.Odup)
emitOpcode(c.prog, vm.Otoaltstack)
emitInt(c.prog, int64(pos))
emitOpcode(c.prog, vm.Opickitem)
}
func (c *codegen) emitStoreLocal(pos int) {
emitOpcode(c.prog, vm.Ofromaltstack)
emitOpcode(c.prog, vm.Odup)
emitOpcode(c.prog, vm.Otoaltstack)
if pos < 0 {
log.Fatalf("invalid position to store local: %d", pos)
}
emitInt(c.prog, int64(pos))
emitInt(c.prog, 2)
emitOpcode(c.prog, vm.Oroll)
emitOpcode(c.prog, vm.Osetitem)
}
func (c *codegen) emitLoadStructField(i int) {
emitInt(c.prog, int64(i))
emitOpcode(c.prog, vm.Opickitem)
}
func (c *codegen) emitStoreStructField(i int) {
emitInt(c.prog, int64(i))
emitOpcode(c.prog, vm.Orot)
emitOpcode(c.prog, vm.Osetitem)
}
func (c *codegen) emitSyscallReturn() {
emitOpcode(c.prog, vm.Ojmp)
emitOpcode(c.prog, vm.Opcode(0x03))
emitOpcode(c.prog, vm.Opush0)
emitInt(c.prog, int64(0))
emitOpcode(c.prog, vm.Onop)
emitOpcode(c.prog, vm.Ofromaltstack)
emitOpcode(c.prog, vm.Odrop)
emitOpcode(c.prog, vm.Oret)
}
// convertGlobals will traverse the AST and only convert global declarations.
// If we call this in convertFuncDecl then it will load all global variables
// into the scope of the function.
func (c *codegen) convertGlobals(f *ast.File) {
ast.Inspect(f, func(node ast.Node) bool {
switch n := node.(type) {
case *ast.FuncDecl:
return false
case *ast.GenDecl:
ast.Walk(c, n)
}
return true
})
}
func (c *codegen) convertFuncDecl(file *ast.File, decl *ast.FuncDecl) {
var (
f *funcScope
ok bool
)
f, ok = c.funcs[decl.Name.Name]
if ok {
c.setLabel(f.label)
} else {
f = c.newFunc(decl)
}
c.scope = f
ast.Inspect(decl, c.scope.analyzeVoidCalls)
// All globals copied into the scope of the function need to be added
// to the stack size of the function.
emitInt(c.prog, f.stackSize()+countGlobals(file))
emitOpcode(c.prog, vm.Onewarray)
emitOpcode(c.prog, vm.Otoaltstack)
// We need to handle methods, which in Go, is just syntactic sugar.
// The method receiver will be passed in as first argument.
// We check if this declaration has a receiver and load it into scope.
//
// FIXME: For now we will hard cast this to a struct. We can later finetune this
// to support other types.
if decl.Recv != nil {
for _, arg := range decl.Recv.List {
ident := arg.Names[0]
// Currently only method receives for struct types is supported.
_, ok := c.typeInfo.Defs[ident].Type().Underlying().(*types.Struct)
if !ok {
log.Fatal("method receives for non-struct types is not yet supported")
}
l := c.scope.newLocal(ident.Name)
c.emitStoreLocal(l)
}
}
// Load the arguments in scope.
for _, arg := range decl.Type.Params.List {
name := arg.Names[0].Name // for now.
l := c.scope.newLocal(name)
c.emitStoreLocal(l)
}
// If this function is a syscall we will manipulate the return value to 0.
// All the syscalls are just signatures functions and bring no real return value.
// The return values you will find in the smartcontract package is just for
// satisfying the typechecker and the user experience.
if isSyscall(f.name) {
c.emitSyscallReturn()
} else {
// After loading the arguments we can convert the globals into the scope of the function.
c.convertGlobals(file)
ast.Walk(c, decl.Body)
}
}
func (c *codegen) Visit(node ast.Node) ast.Visitor {
switch n := node.(type) {
// General declarations.
// var (
// x = 2
// )
case *ast.GenDecl:
for _, spec := range n.Specs {
switch t := spec.(type) {
case *ast.ValueSpec:
for i, val := range t.Values {
ast.Walk(c, val)
l := c.scope.newLocal(t.Names[i].Name)
c.emitStoreLocal(l)
}
}
}
return nil
case *ast.AssignStmt:
for i := 0; i < len(n.Lhs); i++ {
switch t := n.Lhs[i].(type) {
case *ast.Ident:
switch n.Tok {
case token.ADD_ASSIGN, token.SUB_ASSIGN, token.MUL_ASSIGN, token.QUO_ASSIGN:
c.emitLoadLocal(t.Name)
ast.Walk(c, n.Rhs[0]) // can only add assign to 1 expr on the RHS
c.convertToken(n.Tok)
l := c.scope.loadLocal(t.Name)
c.emitStoreLocal(l)
default:
ast.Walk(c, n.Rhs[i])
l := c.scope.loadLocal(t.Name)
c.emitStoreLocal(l)
}
case *ast.SelectorExpr:
switch expr := t.X.(type) {
case *ast.Ident:
ast.Walk(c, n.Rhs[i])
typ := c.typeInfo.ObjectOf(expr).Type().Underlying()
if strct, ok := typ.(*types.Struct); ok {
c.emitLoadLocal(expr.Name) // load the struct
i := indexOfStruct(strct, t.Sel.Name) // get the index of the field
c.emitStoreStructField(i) // store the field
}
default:
log.Fatal("nested selector assigns not supported yet")
}
}
}
return nil
case *ast.ReturnStmt:
if len(n.Results) > 1 {
log.Fatal("multiple returns not supported.")
}
emitOpcode(c.prog, vm.Ojmp)
emitOpcode(c.prog, vm.Opcode(0x03))
emitOpcode(c.prog, vm.Opush0)
if len(n.Results) > 0 {
ast.Walk(c, n.Results[0])
}
emitOpcode(c.prog, vm.Onop)
emitOpcode(c.prog, vm.Ofromaltstack)
emitOpcode(c.prog, vm.Odrop)
emitOpcode(c.prog, vm.Oret)
return nil
case *ast.IfStmt:
lIf := c.newLabel()
lElse := c.newLabel()
if n.Cond != nil {
ast.Walk(c, n.Cond)
emitJmp(c.prog, vm.Ojmpifnot, int16(lElse))
}
c.setLabel(lIf)
ast.Walk(c, n.Body)
if n.Else != nil {
// TODO: handle else statements.
// emitJmp(c.prog, vm.Ojmp, int16(lEnd))
}
c.setLabel(lElse)
if n.Else != nil {
ast.Walk(c, n.Else)
}
return nil
case *ast.BasicLit:
c.emitLoadConst(c.typeInfo.Types[n])
return nil
case *ast.Ident:
if isIdentBool(n) {
c.emitLoadConst(makeBoolFromIdent(n, c.typeInfo))
} else {
c.emitLoadLocal(n.Name)
}
return nil
case *ast.CompositeLit:
var typ types.Type
switch t := n.Type.(type) {
case *ast.Ident:
typ = c.typeInfo.ObjectOf(t).Type().Underlying()
case *ast.SelectorExpr:
typ = c.typeInfo.ObjectOf(t.Sel).Type().Underlying()
default:
ln := len(n.Elts)
// ByteArrays need a different approach then normal arrays.
if isByteArray(n, c.typeInfo) {
c.convertByteArray(n)
return nil
}
for i := ln - 1; i >= 0; i-- {
c.emitLoadConst(c.typeInfo.Types[n.Elts[i]])
}
emitInt(c.prog, int64(ln))
emitOpcode(c.prog, vm.Opack)
return nil
}
switch typ.(type) {
case *types.Struct:
c.convertStruct(n)
}
return nil
case *ast.BinaryExpr:
switch n.Op {
case token.LAND:
ast.Walk(c, n.X)
emitJmp(c.prog, vm.Ojmpifnot, int16(len(c.l)-1))
ast.Walk(c, n.Y)
return nil
case token.LOR:
ast.Walk(c, n.X)
emitJmp(c.prog, vm.Ojmpif, int16(len(c.l)-2))
ast.Walk(c, n.Y)
return nil
default:
// The AST package will try to resolve all basic literals for us.
// If the typeinfo.Value is not nil we know that the expr is resolved
// and needs no further action. e.g. x := 2 + 2 + 2 will be resolved to 6.
// NOTE: Constants will also be automagically resolved be the AST parser.
// example:
// const x = 10
// x + 2 will results into 12
if tinfo := c.typeInfo.Types[n]; tinfo.Value != nil {
c.emitLoadConst(tinfo)
return nil
}
ast.Walk(c, n.X)
ast.Walk(c, n.Y)
c.convertToken(n.Op)
return nil
}
case *ast.CallExpr:
var (
f *funcScope
ok bool
numArgs = len(n.Args)
)
switch fun := n.Fun.(type) {
case *ast.Ident:
f, ok = c.funcs[fun.Name]
if !ok {
log.Fatalf("could not resolve function %s", fun.Name)
}
case *ast.SelectorExpr:
// If this is a method call we need to walk the AST to load the struct locally.
// Otherwise this is a function call from a imported package and we can call it
// directly.
if c.typeInfo.Selections[fun] != nil {
ast.Walk(c, fun.X)
// Dont forget to add 1 extra argument when its a method.
numArgs++
}
f, ok = c.funcs[fun.Sel.Name]
if !ok {
log.Fatalf("could not resolve function %s", fun.Sel.Name)
}
}
// Handle the arguments
for _, arg := range n.Args {
ast.Walk(c, arg)
}
if numArgs == 2 {
emitOpcode(c.prog, vm.Oswap)
}
if numArgs == 3 {
emitInt(c.prog, 2)
emitOpcode(c.prog, vm.Oxswap)
}
// c# compiler adds a NOP (0x61) before every function call. Dont think its relevant
// and we could easily removed it, but to be consistent with the original compiler I
// will put them in. ^^
emitOpcode(c.prog, vm.Onop)
if isSyscall(f.name) {
c.convertSyscall(f.name)
} else {
emitCall(c.prog, vm.Ocall, int16(f.label))
}
// If we are not assigning this function to a variable we need to drop
// the top stack item. It's not a void but you get the point \o/.
if _, ok := c.scope.voidCalls[n]; ok && !isNoRetSyscall(f.name) {
emitOpcode(c.prog, vm.Odrop)
}
return nil
case *ast.SelectorExpr:
switch t := n.X.(type) {
case *ast.Ident:
typ := c.typeInfo.ObjectOf(t).Type().Underlying()
if strct, ok := typ.(*types.Struct); ok {
c.emitLoadLocal(t.Name) // load the struct
i := indexOfStruct(strct, n.Sel.Name)
c.emitLoadStructField(i) // load the field
}
default:
log.Fatal("nested selectors not supported yet")
}
return nil
case *ast.UnaryExpr:
// fmt.Println(n)
}
return c
}
func (c *codegen) convertSyscall(name string) {
api, ok := vm.Syscalls[name]
if !ok {
log.Fatalf("unknown VM syscall api: %s", name)
}
emitSyscall(c.prog, api)
emitOpcode(c.prog, vm.Onop)
}
func (c *codegen) convertByteArray(lit *ast.CompositeLit) {
buf := make([]byte, len(lit.Elts))
for i := 0; i < len(lit.Elts); i++ {
t := c.typeInfo.Types[lit.Elts[i]]
val, _ := constant.Int64Val(t.Value)
buf[i] = byte(val)
}
emitBytes(c.prog, buf)
}
func (c *codegen) convertStruct(lit *ast.CompositeLit) {
// Create a new structScope to initialize and store
// the positions of its variables.
strct, ok := c.typeInfo.TypeOf(lit).Underlying().(*types.Struct)
if !ok {
log.Fatalf("the given literal is not of type struct: %v", lit)
}
emitOpcode(c.prog, vm.Onop)
emitInt(c.prog, int64(strct.NumFields()))
emitOpcode(c.prog, vm.Onewstruct)
emitOpcode(c.prog, vm.Otoaltstack)
// We need to locally store all the fields, even if they are not initialized.
// We will initialize all fields to their "zero" value.
for i := 0; i < strct.NumFields(); i++ {
sField := strct.Field(i)
fieldAdded := false
// Fields initialized by the program.
for _, field := range lit.Elts {
f := field.(*ast.KeyValueExpr)
fieldName := f.Key.(*ast.Ident).Name
if sField.Name() == fieldName {
ast.Walk(c, f.Value)
pos := indexOfStruct(strct, fieldName)
c.emitStoreLocal(pos)
fieldAdded = true
break
}
}
if fieldAdded {
continue
}
typeAndVal := typeAndValueForField(sField)
c.emitLoadConst(typeAndVal)
c.emitStoreLocal(i)
}
emitOpcode(c.prog, vm.Ofromaltstack)
}
func (c *codegen) convertToken(tok token.Token) {
switch tok {
case token.ADD_ASSIGN:
emitOpcode(c.prog, vm.Oadd)
case token.SUB_ASSIGN:
emitOpcode(c.prog, vm.Osub)
case token.MUL_ASSIGN:
emitOpcode(c.prog, vm.Omul)
case token.QUO_ASSIGN:
emitOpcode(c.prog, vm.Odiv)
case token.ADD:
emitOpcode(c.prog, vm.Oadd)
case token.SUB:
emitOpcode(c.prog, vm.Osub)
case token.MUL:
emitOpcode(c.prog, vm.Omul)
case token.QUO:
emitOpcode(c.prog, vm.Odiv)
case token.LSS:
emitOpcode(c.prog, vm.Olt)
case token.LEQ:
emitOpcode(c.prog, vm.Olte)
case token.GTR:
emitOpcode(c.prog, vm.Ogt)
case token.GEQ:
emitOpcode(c.prog, vm.Ogte)
case token.EQL, token.NEQ:
emitOpcode(c.prog, vm.Onumequal)
default:
log.Fatalf("compiler could not convert token: %s", tok)
}
}
func (c *codegen) newFunc(decl *ast.FuncDecl) *funcScope {
f := newFuncScope(decl, c.newLabel())
c.funcs[f.name] = f
return f
}
// CodeGen is the function that compiles the program to bytecode.
func CodeGen(info *buildInfo) (*bytes.Buffer, error) {
pkg := info.program.Package(info.initialPackage)
c := &codegen{
buildInfo: info,
prog: new(bytes.Buffer),
l: []int{},
funcs: map[string]*funcScope{},
typeInfo: &pkg.Info,
}
// Resolve the entrypoint of the program
main, mainFile := resolveEntryPoint(mainIdent, pkg)
if main == nil {
log.Fatal("could not find func main. did you forgot to declare it?")
}
funUsage := analyzeFuncUsage(info.program.AllPackages)
// Bring all imported functions into scope
for _, pkg := range info.program.AllPackages {
for _, f := range pkg.Files {
c.resolveFuncDecls(f)
}
}
// convert the entry point first
c.convertFuncDecl(mainFile, main)
// Generate the code for the program
for _, pkg := range info.program.AllPackages {
c.typeInfo = &pkg.Info
for _, f := range pkg.Files {
for _, decl := range f.Decls {
switch n := decl.(type) {
case *ast.FuncDecl:
// Dont convert the function if its not used. This will save alot
// of bytecode space.
if n.Name.Name != mainIdent && funUsage.funcUsed(n.Name.Name) {
c.convertFuncDecl(f, n)
}
}
}
}
}
c.writeJumps()
return c.prog, nil
}
func (c *codegen) resolveFuncDecls(f *ast.File) {
for _, decl := range f.Decls {
switch n := decl.(type) {
case *ast.FuncDecl:
if n.Name.Name != mainIdent {
c.newFunc(n)
}
}
}
}
func (c *codegen) writeJumps() {
b := c.prog.Bytes()
for i, op := range b {
j := i + 1
switch vm.Opcode(op) {
case vm.Ojmpifnot, vm.Ojmpif, vm.Ocall:
index := binary.LittleEndian.Uint16(b[j : j+2])
if int(index) > len(c.l) {
continue
}
offset := uint16(c.l[index] - i)
if offset < 0 {
log.Fatalf("new offset is negative, table list %v", c.l)
}
binary.LittleEndian.PutUint16(b[j:j+2], offset)
}
}
}
func isSyscall(name string) bool {
_, ok := vm.Syscalls[name]
return ok
}
var noRetSyscalls = []string{
"Notify", "Log", "Put", "Register", "Delete",
"SetVotes", "ContractDestroy", "MerkleRoot", "Hash",
"PrevHash", "GetHeader",
}
// isNoRetSyscall checks if the syscall has a return value.
func isNoRetSyscall(name string) bool {
for _, s := range noRetSyscalls {
if s == name {
return true
}
}
return false
}