diff --git a/compiler/internal/build/build.go b/compiler/internal/build/build.go
index f80d8daf..a8aa3f0b 100644
--- a/compiler/internal/build/build.go
+++ b/compiler/internal/build/build.go
@@ -46,6 +46,7 @@ import (
 	"github.com/goplus/llgo/xtool/env/llvm"
 
 	llssa "github.com/goplus/llgo/compiler/ssa"
+	llruntime "github.com/goplus/llgo/runtime"
 	clangCheck "github.com/goplus/llgo/xtool/clang/check"
 )
 
@@ -133,9 +134,9 @@ func Do(args []string, conf *Config) ([]Package, error) {
 		cfg.Mode |= packages.NeedForTest
 	}
 
-	if len(overlayFiles) > 0 {
+	if len(llruntime.OverlayFiles) > 0 {
 		cfg.Overlay = make(map[string][]byte)
-		for file, src := range overlayFiles {
+		for file, src := range llruntime.OverlayFiles {
 			overlay := unsafe.Slice(unsafe.StringData(src), len(src))
 			cfg.Overlay[filepath.Join(env.GOROOT(), "src", file)] = overlay
 		}
@@ -154,7 +155,7 @@ func Do(args []string, conf *Config) ([]Package, error) {
 	sizes := prog.TypeSizes
 	dedup := packages.NewDeduper()
 	dedup.SetPreload(func(pkg *types.Package, files []*ast.File) {
-		if canSkipToBuild(pkg.Path()) {
+		if llruntime.SkipToBuild(pkg.Path()) {
 			return
 		}
 		cl.ParsePkgSyntax(prog, pkg, files)
@@ -580,7 +581,7 @@ func buildPkg(ctx *context, aPkg *aPackage, verbose bool) (cgoLdflags []string,
 	if debugBuild || verbose {
 		fmt.Fprintln(os.Stderr, pkgPath)
 	}
-	if canSkipToBuild(pkgPath) {
+	if llruntime.SkipToBuild(pkgPath) {
 		pkg.ExportFile = ""
 		return
 	}
@@ -642,8 +643,8 @@ const (
 func altPkgs(initial []*packages.Package, alts ...string) []string {
 	packages.Visit(initial, nil, func(p *packages.Package) {
 		if p.Types != nil && !p.IllTyped {
-			if _, ok := hasAltPkg[p.ID]; ok {
-				alts = append(alts, altPkgPathPrefix+p.ID)
+			if llruntime.HasAltPkg(p.PkgPath) {
+				alts = append(alts, altPkgPathPrefix+p.PkgPath)
 			}
 		}
 	})
@@ -691,7 +692,7 @@ func allPkgs(ctx *context, initial []*packages.Package, verbose bool) (all []*aP
 			}
 			var altPkg *packages.Cached
 			var ssaPkg = createSSAPkg(prog, p, verbose)
-			if _, ok := hasAltPkg[pkgPath]; ok {
+			if llruntime.HasAltPkg(pkgPath) {
 				if altPkg = ctx.dedup.Check(altPkgPathPrefix + pkgPath); altPkg == nil {
 					return
 				}
@@ -864,13 +865,6 @@ func pkgExists(initial []*packages.Package, pkg *packages.Package) bool {
 	return false
 }
 
-func canSkipToBuild(pkgPath string) bool {
-	if _, ok := hasAltPkg[pkgPath]; ok {
-		return false
-	}
-	return pkgPath == "unsafe"
-}
-
 // findDylibDep finds the dylib dependency in the executable. It returns empty
 // string if not found.
 func findDylibDep(exe, lib string) string {
@@ -889,49 +883,6 @@ func findDylibDep(exe, lib string) string {
 
 type none struct{}
 
-var hasAltPkg = map[string]none{
-	"crypto/hmac":              {},
-	"crypto/md5":               {},
-	"crypto/rand":              {},
-	"crypto/sha1":              {},
-	"crypto/sha256":            {},
-	"crypto/sha512":            {},
-	"crypto/subtle":            {},
-	"go/parser":                {},
-	"hash/crc32":               {},
-	"internal/abi":             {},
-	"internal/bytealg":         {},
-	"internal/cpu":             {},
-	"internal/itoa":            {},
-	"internal/filepathlite":    {},
-	"internal/godebug":         {},
-	"internal/oserror":         {},
-	"internal/poll":            {},
-	"internal/race":            {},
-	"internal/reflectlite":     {},
-	"internal/stringslite":     {},
-	"internal/syscall/execenv": {},
-	"internal/syscall/unix":    {},
-	"math":                     {},
-	"math/big":                 {},
-	"math/cmplx":               {},
-	"math/rand":                {},
-	"reflect":                  {},
-	"sync":                     {},
-	"sync/atomic":              {},
-	"syscall":                  {},
-	"time":                     {},
-	"os":                       {},
-	"os/exec":                  {},
-	"os/signal":                {},
-	"runtime":                  {},
-	"runtime/debug":            {},
-	"runtime/pprof":            {},
-	"runtime/trace":            {},
-	"runtime/internal/syscall": {},
-	"io":                       {},
-}
-
 func check(err error) {
 	if err != nil {
 		panic(err)
diff --git a/compiler/internal/build/_overlay/go/parser/resolver.go b/runtime/_overlay/go/parser/resolver.go
similarity index 100%
rename from compiler/internal/build/_overlay/go/parser/resolver.go
rename to runtime/_overlay/go/parser/resolver.go
diff --git a/compiler/internal/build/_overlay/net/textproto/textproto.go b/runtime/_overlay/net/textproto/textproto.go
similarity index 100%
rename from compiler/internal/build/_overlay/net/textproto/textproto.go
rename to runtime/_overlay/net/textproto/textproto.go
diff --git a/compiler/internal/build/_overlay/testing/testing.go b/runtime/_overlay/testing/testing.go
similarity index 100%
rename from compiler/internal/build/_overlay/testing/testing.go
rename to runtime/_overlay/testing/testing.go
diff --git a/runtime/build.go b/runtime/build.go
new file mode 100644
index 00000000..dc6dfe67
--- /dev/null
+++ b/runtime/build.go
@@ -0,0 +1,75 @@
+package runtime
+
+import (
+	"strings"
+)
+
+func SkipToBuild(pkgPath string) bool {
+	if _, ok := hasAltPkg[pkgPath]; ok {
+		return false
+	}
+	if _, ok := supportedInternal[pkgPath]; ok {
+		return false
+	}
+	switch pkgPath {
+	case "unsafe":
+		return true
+	default:
+		return strings.HasPrefix(pkgPath, "internal/") ||
+			strings.HasPrefix(pkgPath, "runtime/internal/")
+	}
+}
+
+func HasAltPkg(path string) (b bool) {
+	_, b = hasAltPkg[path]
+	return
+}
+
+type none struct{}
+
+var hasAltPkg = map[string]none{
+	"crypto/hmac":              {},
+	"crypto/md5":               {},
+	"crypto/rand":              {},
+	"crypto/sha1":              {},
+	"crypto/sha256":            {},
+	"crypto/sha512":            {},
+	"crypto/subtle":            {},
+	"go/parser":                {},
+	"hash/crc32":               {},
+	"internal/abi":             {},
+	"internal/bytealg":         {},
+	"internal/cpu":             {},
+	"internal/itoa":            {},
+	"internal/godebug":         {},
+	"internal/oserror":         {},
+	"internal/poll":            {},
+	"internal/reflectlite":     {},
+	"internal/syscall/execenv": {},
+	"internal/syscall/unix":    {},
+	"math":                     {},
+	"math/big":                 {},
+	"math/cmplx":               {},
+	"math/rand":                {},
+	"reflect":                  {},
+	"sync":                     {},
+	"sync/atomic":              {},
+	"syscall":                  {},
+	"time":                     {},
+	"os":                       {},
+	"os/exec":                  {},
+	"os/signal":                {},
+	"runtime":                  {},
+	"runtime/debug":            {},
+	"runtime/pprof":            {},
+	"runtime/trace":            {},
+	"runtime/internal/syscall": {},
+	"io":                       {},
+}
+
+var supportedInternal = map[string]none{
+	"internal/race":         {},
+	"internal/stringslite":  {},
+	"internal/filepathlite": {},
+	"internal/fmtsort":      {},
+}
diff --git a/runtime/internal/lib/internal/filepathlite/filepathlite.go b/runtime/internal/lib/internal/filepathlite/filepathlite.go
deleted file mode 100644
index 34a3de68..00000000
--- a/runtime/internal/lib/internal/filepathlite/filepathlite.go
+++ /dev/null
@@ -1 +0,0 @@
-package filepathlite
diff --git a/runtime/internal/lib/internal/fmtsort/sort.go b/runtime/internal/lib/internal/fmtsort/sort.go
deleted file mode 100644
index 802f724d..00000000
--- a/runtime/internal/lib/internal/fmtsort/sort.go
+++ /dev/null
@@ -1,222 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// Package fmtsort provides a general stable ordering mechanism
-// for maps, on behalf of the fmt and text/template packages.
-// It is not guaranteed to be efficient and works only for types
-// that are valid map keys.
-package fmtsort
-
-import (
-	"reflect"
-	"sort"
-)
-
-// llgo:skipall
-type _fmtsort struct{}
-
-// Note: Throughout this package we avoid calling reflect.Value.Interface as
-// it is not always legal to do so and it's easier to avoid the issue than to face it.
-
-// SortedMap represents a map's keys and values. The keys and values are
-// aligned in index order: Value[i] is the value in the map corresponding to Key[i].
-type SortedMap struct {
-	Key   []reflect.Value
-	Value []reflect.Value
-}
-
-func (o *SortedMap) Len() int           { return len(o.Key) }
-func (o *SortedMap) Less(i, j int) bool { return compare(o.Key[i], o.Key[j]) < 0 }
-func (o *SortedMap) Swap(i, j int) {
-	o.Key[i], o.Key[j] = o.Key[j], o.Key[i]
-	o.Value[i], o.Value[j] = o.Value[j], o.Value[i]
-}
-
-// Sort accepts a map and returns a SortedMap that has the same keys and
-// values but in a stable sorted order according to the keys, modulo issues
-// raised by unorderable key values such as NaNs.
-//
-// The ordering rules are more general than with Go's < operator:
-//
-//   - when applicable, nil compares low
-//   - ints, floats, and strings order by <
-//   - NaN compares less than non-NaN floats
-//   - bool compares false before true
-//   - complex compares real, then imag
-//   - pointers compare by machine address
-//   - channel values compare by machine address
-//   - structs compare each field in turn
-//   - arrays compare each element in turn.
-//     Otherwise identical arrays compare by length.
-//   - interface values compare first by reflect.Type describing the concrete type
-//     and then by concrete value as described in the previous rules.
-func Sort(mapValue reflect.Value) *SortedMap {
-	if mapValue.Type().Kind() != reflect.Map {
-		return nil
-	}
-	// Note: this code is arranged to not panic even in the presence
-	// of a concurrent map update. The runtime is responsible for
-	// yelling loudly if that happens. See issue 33275.
-	n := mapValue.Len()
-	key := make([]reflect.Value, 0, n)
-	value := make([]reflect.Value, 0, n)
-	iter := mapValue.MapRange()
-	for iter.Next() {
-		key = append(key, iter.Key())
-		value = append(value, iter.Value())
-	}
-	sorted := &SortedMap{
-		Key:   key,
-		Value: value,
-	}
-	sort.Stable(sorted)
-	return sorted
-}
-
-// compare compares two values of the same type. It returns -1, 0, 1
-// according to whether a > b (1), a == b (0), or a < b (-1).
-// If the types differ, it returns -1.
-// See the comment on Sort for the comparison rules.
-func compare(aVal, bVal reflect.Value) int {
-	aType, bType := aVal.Type(), bVal.Type()
-	if aType != bType {
-		return -1 // No good answer possible, but don't return 0: they're not equal.
-	}
-	switch aVal.Kind() {
-	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
-		a, b := aVal.Int(), bVal.Int()
-		switch {
-		case a < b:
-			return -1
-		case a > b:
-			return 1
-		default:
-			return 0
-		}
-	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
-		a, b := aVal.Uint(), bVal.Uint()
-		switch {
-		case a < b:
-			return -1
-		case a > b:
-			return 1
-		default:
-			return 0
-		}
-	case reflect.String:
-		a, b := aVal.String(), bVal.String()
-		switch {
-		case a < b:
-			return -1
-		case a > b:
-			return 1
-		default:
-			return 0
-		}
-	case reflect.Float32, reflect.Float64:
-		return floatCompare(aVal.Float(), bVal.Float())
-	case reflect.Complex64, reflect.Complex128:
-		a, b := aVal.Complex(), bVal.Complex()
-		if c := floatCompare(real(a), real(b)); c != 0 {
-			return c
-		}
-		return floatCompare(imag(a), imag(b))
-	case reflect.Bool:
-		a, b := aVal.Bool(), bVal.Bool()
-		switch {
-		case a == b:
-			return 0
-		case a:
-			return 1
-		default:
-			return -1
-		}
-	case reflect.Pointer, reflect.UnsafePointer:
-		a, b := aVal.Pointer(), bVal.Pointer()
-		switch {
-		case a < b:
-			return -1
-		case a > b:
-			return 1
-		default:
-			return 0
-		}
-	case reflect.Chan:
-		if c, ok := nilCompare(aVal, bVal); ok {
-			return c
-		}
-		ap, bp := aVal.Pointer(), bVal.Pointer()
-		switch {
-		case ap < bp:
-			return -1
-		case ap > bp:
-			return 1
-		default:
-			return 0
-		}
-	case reflect.Struct:
-		for i := 0; i < aVal.NumField(); i++ {
-			if c := compare(aVal.Field(i), bVal.Field(i)); c != 0 {
-				return c
-			}
-		}
-		return 0
-	case reflect.Array:
-		for i := 0; i < aVal.Len(); i++ {
-			if c := compare(aVal.Index(i), bVal.Index(i)); c != 0 {
-				return c
-			}
-		}
-		return 0
-	case reflect.Interface:
-		if c, ok := nilCompare(aVal, bVal); ok {
-			return c
-		}
-		c := compare(reflect.ValueOf(aVal.Elem().Type()), reflect.ValueOf(bVal.Elem().Type()))
-		if c != 0 {
-			return c
-		}
-		return compare(aVal.Elem(), bVal.Elem())
-	default:
-		// Certain types cannot appear as keys (maps, funcs, slices), but be explicit.
-		panic("bad type in compare: " + aType.String())
-	}
-}
-
-// nilCompare checks whether either value is nil. If not, the boolean is false.
-// If either value is nil, the boolean is true and the integer is the comparison
-// value. The comparison is defined to be 0 if both are nil, otherwise the one
-// nil value compares low. Both arguments must represent a chan, func,
-// interface, map, pointer, or slice.
-func nilCompare(aVal, bVal reflect.Value) (int, bool) {
-	if aVal.IsNil() {
-		if bVal.IsNil() {
-			return 0, true
-		}
-		return -1, true
-	}
-	if bVal.IsNil() {
-		return 1, true
-	}
-	return 0, false
-}
-
-// floatCompare compares two floating-point values. NaNs compare low.
-func floatCompare(a, b float64) int {
-	switch {
-	case isNaN(a):
-		return -1 // No good answer if b is a NaN so don't bother checking.
-	case isNaN(b):
-		return 1
-	case a < b:
-		return -1
-	case a > b:
-		return 1
-	}
-	return 0
-}
-
-func isNaN(a float64) bool {
-	return a != a
-}
diff --git a/runtime/internal/lib/internal/race/race.go b/runtime/internal/lib/internal/race/race.go
deleted file mode 100644
index a6b23589..00000000
--- a/runtime/internal/lib/internal/race/race.go
+++ /dev/null
@@ -1 +0,0 @@
-package race
diff --git a/runtime/internal/lib/internal/stringslite/strings.go b/runtime/internal/lib/internal/stringslite/strings.go
deleted file mode 100644
index 66be1e34..00000000
--- a/runtime/internal/lib/internal/stringslite/strings.go
+++ /dev/null
@@ -1 +0,0 @@
-package stringslite
diff --git a/compiler/internal/build/overlay.go b/runtime/overlay.go
similarity index 88%
rename from compiler/internal/build/overlay.go
rename to runtime/overlay.go
index fd8ff857..62bbea28 100644
--- a/compiler/internal/build/overlay.go
+++ b/runtime/overlay.go
@@ -1,4 +1,4 @@
-package build
+package runtime
 
 import (
 	_ "embed"
@@ -13,7 +13,7 @@ var testing_testing string
 //go:embed _overlay/net/textproto/textproto.go
 var net_textproto string
 
-var overlayFiles = map[string]string{
+var OverlayFiles = map[string]string{
 	"math/exp_amd64.go":          "package math;",
 	"go/parser/resolver.go":      go_parser_resolver,
 	"testing/testing.go":         testing_testing,