neo-go/pkg/compiler/analysis.go

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package compiler
import (
"errors"
"fmt"
"go/ast"
"go/token"
"go/types"
"strings"
"github.com/nspcc-dev/neo-go/pkg/vm/emit"
"github.com/nspcc-dev/neo-go/pkg/vm/opcode"
"golang.org/x/tools/go/packages"
)
// Various exported functions usage errors.
var (
// ErrMissingExportedParamName is returned when exported contract method has unnamed parameter.
ErrMissingExportedParamName = errors.New("exported method is not allowed to have unnamed parameter")
// ErrInvalidExportedRetCount is returned when exported contract method has invalid return values count.
ErrInvalidExportedRetCount = errors.New("exported method is not allowed to have more than one return value")
)
var (
// Go language builtin functions.
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goBuiltins = []string{"len", "append", "panic", "make", "copy", "recover", "delete"}
// Custom builtin utility functions.
customBuiltins = []string{
"FromAddress",
}
// Custom builtin utility functions that contain some meaningful code inside and
// require code generation using standard rules, but sometimes (depending on
// the expression usage condition) may be optimized at compile time.
potentialCustomBuiltins = map[string]func(f ast.Expr) bool{
"ToHash160": func(f ast.Expr) bool {
c, ok := f.(*ast.CallExpr)
if !ok {
return false
}
if len(c.Args) != 1 {
return false
}
switch c.Args[0].(type) {
case *ast.BasicLit:
return true
default:
return false
}
},
}
)
// newGlobal creates a new global variable.
func (c *codegen) newGlobal(pkg string, name string) {
name = c.getIdentName(pkg, name)
c.globals[name] = len(c.globals)
}
// getIdentName returns a fully-qualified name for a variable.
func (c *codegen) getIdentName(pkg string, name string) string {
if fullName, ok := c.importMap[pkg]; ok {
pkg = fullName
}
return pkg + "." + name
}
// traverseGlobals visits and initializes global variables.
// It returns `true` if contract has `_deploy` function.
func (c *codegen) traverseGlobals() bool {
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var hasDefer bool
var n, nConst int
var hasUnusedCall bool
var hasDeploy bool
c.ForEachFile(func(f *ast.File, pkg *types.Package) {
nv, nc, huc := countGlobals(f, !hasUnusedCall)
n += nv
nConst += nc
if huc {
hasUnusedCall = true
}
if !hasDeploy || !hasDefer {
ast.Inspect(f, func(node ast.Node) bool {
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switch n := node.(type) {
case *ast.FuncDecl:
hasDeploy = hasDeploy || isDeployFunc(n)
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case *ast.DeferStmt:
hasDefer = true
return false
}
return true
})
}
})
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if hasDefer {
n++
}
if n > 255 {
c.prog.BinWriter.Err = errors.New("too many global variables")
return hasDeploy
}
if n != 0 {
emit.Instruction(c.prog.BinWriter, opcode.INITSSLOT, []byte{byte(n)})
}
initOffset := c.prog.Len()
emit.Instruction(c.prog.BinWriter, opcode.INITSLOT, []byte{0, 0})
lastCnt, maxCnt := -1, -1
c.ForEachPackage(func(pkg *packages.Package) {
if n+nConst > 0 || hasUnusedCall {
for _, f := range pkg.Syntax {
c.fillImportMap(f, pkg)
c.convertGlobals(f)
}
}
for _, f := range pkg.Syntax {
c.fillImportMap(f, pkg)
var currMax int
lastCnt, currMax = c.convertInitFuncs(f, pkg.Types, lastCnt)
if currMax > maxCnt {
maxCnt = currMax
}
}
// because we reuse `convertFuncDecl` for init funcs,
// we need to clear scope, so that global variables
// encountered after will be recognized as globals.
c.scope = nil
})
if c.globalInlineCount > maxCnt {
maxCnt = c.globalInlineCount
}
// Here we remove `INITSLOT` if no code was emitted for `init` function.
// Note that the `INITSSLOT` must stay in place.
hasNoInit := initOffset+3 == c.prog.Len()
if hasNoInit {
buf := c.prog.Bytes()
c.prog.Reset()
c.prog.WriteBytes(buf[:initOffset])
}
if initOffset != 0 || !hasNoInit { // if there are some globals or `init()`.
c.initEndOffset = c.prog.Len()
emit.Opcodes(c.prog.BinWriter, opcode.RET)
if maxCnt >= 0 {
c.reverseOffsetMap[initOffset] = nameWithLocals{
name: "init",
count: maxCnt,
}
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}
}
// store auxiliary variables after all others.
if hasDefer {
c.exceptionIndex = len(c.globals)
c.globals[exceptionVarName] = c.exceptionIndex
}
return hasDeploy
}
// countGlobals counts the global variables in the program to add
// them with the stack size of the function.
// Second returned argument contains the amount of global constants.
// If checkUnusedCalls set to true then unnamed global variables containing call
// will be searched for and their presence is returned as the last argument.
func countGlobals(f ast.Node, checkUnusedCalls bool) (int, int, bool) {
var numVar, numConst int
var hasUnusedCall bool
ast.Inspect(f, func(node ast.Node) bool {
switch n := node.(type) {
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// Skip all function declarations if we have already encountered `defer`.
case *ast.FuncDecl:
return false
// After skipping all funcDecls, we are sure that each value spec
// is a globally declared variable or constant.
case *ast.GenDecl:
isVar := n.Tok == token.VAR
if isVar || n.Tok == token.CONST {
for _, s := range n.Specs {
valueSpec := s.(*ast.ValueSpec)
multiRet := len(valueSpec.Values) != 0 && len(valueSpec.Names) != len(valueSpec.Values) // e.g. var A, B = f() where func f() (int, int)
for j, id := range valueSpec.Names {
if id.Name != "_" { // If variable has name, then it's treated as used - that's countGlobals' caller responsibility to guarantee that.
if isVar {
numVar++
} else {
numConst++
}
} else if isVar && len(valueSpec.Values) != 0 && checkUnusedCalls && !hasUnusedCall {
indexToCheck := j
if multiRet {
indexToCheck = 0
}
hasUnusedCall = containsCall(valueSpec.Values[indexToCheck])
}
}
}
}
return false
}
return true
})
return numVar, numConst, hasUnusedCall
}
// containsCall traverses node and looks if it contains a function or method call.
func containsCall(n ast.Node) bool {
var hasCall bool
ast.Inspect(n, func(node ast.Node) bool {
switch node.(type) {
case *ast.CallExpr:
hasCall = true
case *ast.Ident:
// Can safely skip idents immediately, we're interested at function calls only.
return false
}
return !hasCall
})
return hasCall
}
// isExprNil looks if the given expression is a `nil`.
func isExprNil(e ast.Expr) bool {
v, ok := e.(*ast.Ident)
return ok && v.Name == "nil"
}
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// indexOfStruct returns the index of the given field inside that struct.
// If the struct does not contain that field, it will return -1.
func indexOfStruct(strct *types.Struct, fldName string) int {
for i := 0; i < strct.NumFields(); i++ {
if strct.Field(i).Name() == fldName {
return i
}
}
return -1
}
type funcUsage map[string]bool
func (f funcUsage) funcUsed(name string) bool {
_, ok := f[name]
return ok
}
// lastStmtIsReturn checks if the last statement of the declaration was return statement.
func lastStmtIsReturn(body *ast.BlockStmt) (b bool) {
if l := len(body.List); l != 0 {
switch inner := body.List[l-1].(type) {
case *ast.BlockStmt:
return lastStmtIsReturn(inner)
case *ast.ReturnStmt:
return true
default:
return false
}
}
return false
}
// analyzePkgOrder sets the order in which packages should be processed.
// From Go spec:
//
// A package with no imports is initialized by assigning initial values to all its package-level variables
// followed by calling all init functions in the order they appear in the source, possibly in multiple files,
// as presented to the compiler. If a package has imports, the imported packages are initialized before
// initializing the package itself. If multiple packages import a package, the imported package
// will be initialized only once. The importing of packages, by construction, guarantees
// that there can be no cyclic initialization dependencies.
func (c *codegen) analyzePkgOrder() {
seen := make(map[string]bool)
info := c.buildInfo.program[0]
c.visitPkg(info, seen)
}
func (c *codegen) visitPkg(pkg *packages.Package, seen map[string]bool) {
if seen[pkg.PkgPath] {
return
}
for _, imp := range pkg.Types.Imports() {
c.visitPkg(pkg.Imports[imp.Path()], seen)
}
seen[pkg.PkgPath] = true
c.packages = append(c.packages, pkg.PkgPath)
c.packageCache[pkg.PkgPath] = pkg
}
func (c *codegen) fillDocumentInfo() {
fset := c.buildInfo.config.Fset
fset.Iterate(func(f *token.File) bool {
filePath := f.Position(f.Pos(0)).Filename
c.docIndex[filePath] = len(c.documents)
c.documents = append(c.documents, filePath)
return true
})
}
// analyzeFuncAndGlobalVarUsage traverses all code and returns a map with functions
// which should be present in the emitted code.
// This is done using BFS starting from exported functions or
// the function used in variable declarations (graph edge corresponds to
// the function being called in declaration). It also analyzes global variables
// usage preserving the same traversal strategy and rules. Unused global variables
// are renamed to "_" in the end. Global variable is treated as "used" iff:
// 1. It belongs either to main or to exported package AND is used directly from the exported (or _init\_deploy) method of the main package.
// 2. It belongs either to main or to exported package AND is used non-directly from the exported (or _init\_deploy) method of the main package
// (e.g. via series of function calls or in some expression that is "used").
// 3. It belongs either to main or to exported package AND contains function call inside its value definition.
func (c *codegen) analyzeFuncAndGlobalVarUsage() funcUsage {
type declPair struct {
decl *ast.FuncDecl
importMap map[string]string
path string
}
// globalVar represents a global variable declaration node with the corresponding package context.
type globalVar struct {
decl *ast.GenDecl // decl contains global variables declaration node (there can be multiple declarations in a single node).
specIdx int // specIdx is the index of variable specification in the list of GenDecl specifications.
varIdx int // varIdx is the index of variable name in the specification names.
ident *ast.Ident // ident is a named global variable identifier got from the specified node.
importMap map[string]string
path string
}
// nodeCache contains top-level function declarations.
nodeCache := make(map[string]declPair)
// globalVarsCache contains both used and unused declared named global vars.
globalVarsCache := make(map[string]globalVar)
// diff contains used functions that are not yet marked as "used" and those definition
// requires traversal in the subsequent stages.
diff := funcUsage{}
// globalVarsDiff contains used named global variables that are not yet marked as "used"
// and those declaration requires traversal in the subsequent stages.
globalVarsDiff := funcUsage{}
// usedExpressions contains a set of ast.Nodes that are used in the program and need to be evaluated
// (either they are used from the used functions OR belong to global variable declaration and surrounded by a function call)
var usedExpressions []nodeContext
c.ForEachFile(func(f *ast.File, pkg *types.Package) {
var pkgPath string
isMain := pkg == c.mainPkg.Types
if !isMain {
pkgPath = pkg.Path()
}
ast.Inspect(f, func(node ast.Node) bool {
switch n := node.(type) {
case *ast.CallExpr:
// functions invoked in variable declarations in imported packages
// are marked as used.
var name string
switch t := n.Fun.(type) {
case *ast.Ident:
name = c.getIdentName(pkgPath, t.Name)
case *ast.SelectorExpr:
name, _ = c.getFuncNameFromSelector(t)
default:
return true
}
diff[name] = true
case *ast.FuncDecl:
name := c.getFuncNameFromDecl(pkgPath, n)
// exported functions and methods are always assumed to be used
if isMain && n.Name.IsExported() || isInitFunc(n) || isDeployFunc(n) {
diff[name] = true
}
// exported functions are not allowed to have unnamed parameters or multiple return values
if isMain && n.Name.IsExported() && n.Recv == nil {
if n.Type.Params.List != nil {
for i, param := range n.Type.Params.List {
if param.Names == nil {
c.prog.Err = fmt.Errorf("%w: %s", ErrMissingExportedParamName, n.Name)
return false // Program is invalid.
}
for _, name := range param.Names {
if name == nil || name.Name == "_" {
c.prog.Err = fmt.Errorf("%w: %s/%d", ErrMissingExportedParamName, n.Name, i)
return false // Program is invalid.
}
}
}
}
if retCnt := n.Type.Results.NumFields(); retCnt > 1 {
c.prog.Err = fmt.Errorf("%w: %s/%d return values", ErrInvalidExportedRetCount, n.Name, retCnt)
}
}
nodeCache[name] = declPair{n, c.importMap, pkgPath}
return false // will be processed in the next stage
case *ast.GenDecl:
// After skipping all funcDecls, we are sure that each value spec
// is a globally declared variable or constant. We need to gather global
// vars from both main and imported packages.
if n.Tok == token.VAR {
for i, s := range n.Specs {
valSpec := s.(*ast.ValueSpec)
for j, id := range valSpec.Names {
if id.Name != "_" {
name := c.getIdentName(pkgPath, id.Name)
globalVarsCache[name] = globalVar{
decl: n,
specIdx: i,
varIdx: j,
ident: id,
importMap: c.importMap,
path: pkgPath,
}
}
// Traverse both named/unnamed global variables, check whether function/method call
// is present inside variable value and if so, mark all its children as "used" for
// further traversal and evaluation.
if len(valSpec.Values) == 0 {
continue
}
multiRet := len(valSpec.Values) != len(valSpec.Names)
if (j == 0 || !multiRet) && containsCall(valSpec.Values[j]) {
usedExpressions = append(usedExpressions, nodeContext{
node: valSpec.Values[j],
path: pkgPath,
importMap: c.importMap,
typeInfo: c.typeInfo,
currPkg: c.currPkg,
})
}
}
}
}
}
return true
})
})
if c.prog.Err != nil {
return nil
}
// Handle nodes that contain (or surrounded by) function calls and are a part
// of global variable declaration.
c.pickVarsFromNodes(usedExpressions, func(name string) {
if _, gOK := globalVarsCache[name]; gOK {
globalVarsDiff[name] = true
}
})
// Traverse the set of upper-layered used functions and construct the functions' usage map.
// At the same time, go through the whole set of used functions and mark global vars used
// from these functions as "used". Also mark the global variables from the previous step
// and their children as "used".
usage := funcUsage{}
globalVarsUsage := funcUsage{}
for len(diff) != 0 || len(globalVarsDiff) != 0 {
nextDiff := funcUsage{}
nextGlobalVarsDiff := funcUsage{}
usedExpressions = usedExpressions[:0]
for name := range diff {
fd, ok := nodeCache[name]
if !ok || usage[name] {
continue
}
usage[name] = true
pkg := c.mainPkg
if fd.path != "" {
pkg = c.packageCache[fd.path]
}
c.typeInfo = pkg.TypesInfo
c.currPkg = pkg
c.importMap = fd.importMap
ast.Inspect(fd.decl, func(node ast.Node) bool {
switch n := node.(type) {
case *ast.CallExpr:
switch t := n.Fun.(type) {
case *ast.Ident:
nextDiff[c.getIdentName(fd.path, t.Name)] = true
case *ast.SelectorExpr:
name, _ := c.getFuncNameFromSelector(t)
nextDiff[name] = true
}
}
return true
})
usedExpressions = append(usedExpressions, nodeContext{
node: fd.decl.Body,
path: fd.path,
importMap: c.importMap,
typeInfo: c.typeInfo,
currPkg: c.currPkg,
})
}
// Traverse used global vars in a separate cycle so that we're sure there's no other unrelated vars.
// Mark their children as "used".
for name := range globalVarsDiff {
fd, ok := globalVarsCache[name]
if !ok || globalVarsUsage[name] {
continue
}
globalVarsUsage[name] = true
pkg := c.mainPkg
if fd.path != "" {
pkg = c.packageCache[fd.path]
}
valSpec := fd.decl.Specs[fd.specIdx].(*ast.ValueSpec)
if len(valSpec.Values) == 0 {
continue
}
multiRet := len(valSpec.Values) != len(valSpec.Names)
if fd.varIdx == 0 || !multiRet {
usedExpressions = append(usedExpressions, nodeContext{
node: valSpec.Values[fd.varIdx],
path: fd.path,
importMap: fd.importMap,
typeInfo: pkg.TypesInfo,
currPkg: pkg,
})
}
}
c.pickVarsFromNodes(usedExpressions, func(name string) {
if _, gOK := globalVarsCache[name]; gOK {
nextGlobalVarsDiff[name] = true
}
})
diff = nextDiff
globalVarsDiff = nextGlobalVarsDiff
}
// Tiny hack: rename all remaining unused global vars. After that these unused
// vars will be handled as any other unnamed unused variables, i.e.
// c.traverseGlobals() won't take them into account during static slot creation
// and the code won't be emitted for them.
for name, node := range globalVarsCache {
if _, ok := globalVarsUsage[name]; !ok {
node.ident.Name = "_"
}
}
return usage
}
// nodeContext contains ast node with the corresponding import map, type info and package information
// required to retrieve fully qualified node name (if so).
type nodeContext struct {
node ast.Node
path string
importMap map[string]string
typeInfo *types.Info
currPkg *packages.Package
}
// derive returns provided node with the parent's context.
func (c nodeContext) derive(n ast.Node) nodeContext {
return nodeContext{
node: n,
path: c.path,
importMap: c.importMap,
typeInfo: c.typeInfo,
currPkg: c.currPkg,
}
}
// pickVarsFromNodes searches for variables used in the given set of nodes
// calling markAsUsed for each variable. Be careful while using codegen after
// pickVarsFromNodes, it changes importMap, currPkg and typeInfo.
func (c *codegen) pickVarsFromNodes(nodes []nodeContext, markAsUsed func(name string)) {
for len(nodes) != 0 {
var nextExprToCheck []nodeContext
for _, val := range nodes {
// Set variable context for proper name extraction.
c.importMap = val.importMap
c.currPkg = val.currPkg
c.typeInfo = val.typeInfo
ast.Inspect(val.node, func(node ast.Node) bool {
switch n := node.(type) {
case *ast.KeyValueExpr: // var _ = f() + CustomInt{Int: Unused}.Int + 3 => mark Unused as "used".
nextExprToCheck = append(nextExprToCheck, val.derive(n.Value))
return false
case *ast.CallExpr:
switch t := n.Fun.(type) {
case *ast.Ident:
// Do nothing, used functions are handled in a separate cycle.
case *ast.SelectorExpr:
nextExprToCheck = append(nextExprToCheck, val.derive(t))
}
for _, arg := range n.Args {
switch arg.(type) {
case *ast.BasicLit:
default:
nextExprToCheck = append(nextExprToCheck, val.derive(arg))
}
}
return false
case *ast.SelectorExpr:
if c.typeInfo.Selections[n] != nil {
switch t := n.X.(type) {
case *ast.Ident:
nextExprToCheck = append(nextExprToCheck, val.derive(t))
case *ast.CompositeLit:
nextExprToCheck = append(nextExprToCheck, val.derive(t))
case *ast.SelectorExpr: // imp_pkg.Anna.GetAge() => mark Anna (exported global struct) as used.
nextExprToCheck = append(nextExprToCheck, val.derive(t))
}
} else {
ident := n.X.(*ast.Ident)
name := c.getIdentName(ident.Name, n.Sel.Name)
markAsUsed(name)
}
return false
case *ast.CompositeLit: // var _ = f(1) + []int{1, Unused, 3}[1] => mark Unused as "used".
for _, e := range n.Elts {
switch e.(type) {
case *ast.BasicLit:
default:
nextExprToCheck = append(nextExprToCheck, val.derive(e))
}
}
return false
case *ast.Ident:
name := c.getIdentName(val.path, n.Name)
markAsUsed(name)
return false
case *ast.DeferStmt:
nextExprToCheck = append(nextExprToCheck, val.derive(n.Call.Fun))
return false
case *ast.BasicLit:
return false
}
return true
})
}
nodes = nextExprToCheck
}
}
func isGoBuiltin(name string) bool {
for i := range goBuiltins {
if name == goBuiltins[i] {
return true
}
}
return false
}
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func isCustomBuiltin(f *funcScope) bool {
if !isInteropPath(f.pkg.Path()) {
return false
}
for _, n := range customBuiltins {
if f.name == n {
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return true
}
}
return false
}
func isPotentialCustomBuiltin(f *funcScope, expr ast.Expr) bool {
if !isInteropPath(f.pkg.Path()) {
return false
}
for name, isBuiltin := range potentialCustomBuiltins {
if f.name == name && isBuiltin(expr) {
return true
}
}
return false
}
func isSyscall(fun *funcScope) bool {
if fun.selector == nil || fun.pkg == nil || !isInteropPath(fun.pkg.Path()) {
return false
}
return fun.pkg.Name() == "neogointernal" && (strings.HasPrefix(fun.name, "Syscall") ||
strings.HasPrefix(fun.name, "Opcode") || strings.HasPrefix(fun.name, "CallWithToken"))
}
const interopPrefix = "github.com/nspcc-dev/neo-go/pkg/interop"
func isInteropPath(s string) bool {
return strings.HasPrefix(s, interopPrefix)
}
// canConvert returns true if type doesn't need to be converted on type assertion.
func canConvert(s string) bool {
if len(s) != 0 && s[0] == '*' {
s = s[1:]
}
if isInteropPath(s) {
s = s[len(interopPrefix):]
return s != "/iterator.Iterator" && s != "/storage.Context" &&
s != "/native/ledger.Block" && s != "/native/ledger.Transaction" &&
s != "/native/management.Contract" && s != "/native/neo.AccountState" &&
s != "/native/ledger.BlockSR"
}
return true
}
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// canInline returns true if the function is to be inlined.
// The list of functions that can be inlined is not static, it depends on the function usages.
// isBuiltin denotes whether code generation for dynamic builtin function will be performed
// manually.
func canInline(s string, name string, isBuiltin bool) bool {
if strings.HasPrefix(s, "github.com/nspcc-dev/neo-go/pkg/compiler/testdata/inline") {
return true
}
if !isInteropPath(s) {
return false
}
return !strings.HasPrefix(s[len(interopPrefix):], "/neogointernal") &&
!(strings.HasPrefix(s[len(interopPrefix):], "/util") && name == "FromAddress") &&
!(strings.HasPrefix(s[len(interopPrefix):], "/lib/address") && name == "ToHash160" && isBuiltin)
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}