diff --git a/cl/_testcgo/any/in.go b/cl/_testcgo/any/in.go
new file mode 100644
index 00000000..0c75725e
--- /dev/null
+++ b/cl/_testcgo/any/in.go
@@ -0,0 +1,16 @@
+package main
+
+import _ "unsafe"
+
+func incVal(a any) int {
+	return a.(int) + 1
+}
+
+//go:linkname printf C.printf
+func printf(format *int8, __llgo_va_list ...any)
+
+var format = [...]int8{'H', 'e', 'l', 'l', 'o', ' ', '%', 'd', '\n', 0}
+
+func main() {
+	printf(&format[0], incVal(100))
+}
diff --git a/cl/_testcgo/any/out.ll b/cl/_testcgo/any/out.ll
new file mode 100644
index 00000000..e69de29b
diff --git a/cl/compile.go b/cl/compile.go
index 5a3a602d..58aa435a 100644
--- a/cl/compile.go
+++ b/cl/compile.go
@@ -329,6 +329,9 @@ func (p *context) compileInstrAndValue(b llssa.Builder, iv instrAndValue) (ret l
 			return
 		}
 		panic("todo")
+	case *ssa.TypeAssert:
+		x := p.compileValue(b, v.X)
+		ret = b.TypeAssert(x, p.prog.Type(v.AssertedType), v.CommaOk)
 	default:
 		panic(fmt.Sprintf("compileInstrAndValue: unknown instr - %T\n", iv))
 	}
diff --git a/cl/compile_test.go b/cl/compile_test.go
index 671f8cba..249d8274 100644
--- a/cl/compile_test.go
+++ b/cl/compile_test.go
@@ -28,7 +28,7 @@ func testCompile(t *testing.T, src, expected string) {
 }
 
 func TestFromTestcgo(t *testing.T) {
-	cltest.FromDir(t, "", "./_testcgo", true)
+	cltest.FromDir(t, "any", "./_testcgo", true)
 }
 
 func TestFromTestdata(t *testing.T) {
diff --git a/internal/build/build.go b/internal/build/build.go
index 20bc0bf2..0c97023f 100644
--- a/internal/build/build.go
+++ b/internal/build/build.go
@@ -19,6 +19,7 @@ package build
 import (
 	"fmt"
 	"go/token"
+	"go/types"
 	"log"
 	"os"
 	"os/exec"
@@ -112,6 +113,11 @@ func Do(args []string, conf *Config) {
 	}
 
 	prog := llssa.NewProgram(nil)
+	prog.SetRuntime(func() *types.Package {
+		rt, err := packages.Load(cfg, "github.com/goplus/llgo/internal/runtime")
+		check(err)
+		return rt[0].Types
+	})
 	mode := conf.Mode
 	if mode == ModeBuild && len(initial) == 1 {
 		mode = ModeInstall
diff --git a/internal/llgen/llgenf.go b/internal/llgen/llgenf.go
index 9eca9f8d..203ed23e 100644
--- a/internal/llgen/llgenf.go
+++ b/internal/llgen/llgenf.go
@@ -17,6 +17,7 @@
 package llgen
 
 import (
+	"go/types"
 	"os"
 
 	"github.com/goplus/llgo/cl"
@@ -48,6 +49,12 @@ func GenFromFile(inFile string) string {
 	ssaPkg.Build()
 
 	prog := llssa.NewProgram(nil)
+	prog.SetRuntime(func() *types.Package {
+		rt, err := packages.Load(cfg, "github.com/goplus/llgo/internal/runtime")
+		check(err)
+		return rt[0].Types
+	})
+
 	ret, err := cl.NewPackage(prog, ssaPkg, pkg.Syntax)
 	check(err)
 
diff --git a/internal/runtime/slice.go b/internal/runtime/slice.go
new file mode 100644
index 00000000..21caa126
--- /dev/null
+++ b/internal/runtime/slice.go
@@ -0,0 +1,15 @@
+// Copyright 2009 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 runtime
+
+import (
+	"unsafe"
+)
+
+type slice struct {
+	array unsafe.Pointer
+	len   int
+	cap   int
+}
diff --git a/internal/runtime/z_iface.go b/internal/runtime/z_iface.go
index 87689b2b..b3ae4d05 100644
--- a/internal/runtime/z_iface.go
+++ b/internal/runtime/z_iface.go
@@ -26,8 +26,6 @@ type Interface = iface
 
 type InterfaceType = abi.InterfaceType
 
-type Type = abi.Type
-
 var (
 	TyAny = &InterfaceType{}
 )
diff --git a/internal/runtime/z_slice.go b/internal/runtime/z_slice.go
new file mode 100644
index 00000000..b6d5cbf5
--- /dev/null
+++ b/internal/runtime/z_slice.go
@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package runtime
+
+type Slice = slice
+
+func MakeEmptySlice() Slice {
+	return Slice{nil, 0, 0}
+}
diff --git a/internal/runtime/z_type.go b/internal/runtime/z_type.go
new file mode 100644
index 00000000..41b4f53d
--- /dev/null
+++ b/internal/runtime/z_type.go
@@ -0,0 +1,93 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package runtime
+
+import (
+	"go/types"
+	"unsafe"
+
+	"github.com/goplus/llgo/internal/abi"
+)
+
+type Type = abi.Type
+
+func I2Int(v Interface, t *Type) int64 {
+	if v.tab._type == t {
+		return int64(uintptr(v.data))
+	}
+	panic("I2Int: type mismatch")
+}
+
+func CheckI2Int(v Interface, t *Type) (int64, bool) {
+	if v.tab._type == t {
+		return int64(uintptr(v.data)), true
+	}
+	return 0, false
+}
+
+func Basic(kind types.BasicKind) *Type {
+	return basicTypes[kind]
+}
+
+var (
+	basicTypes = [...]*Type{
+		abi.Bool:       basicType(abi.Bool),
+		abi.Int:        basicType(abi.Int),
+		abi.Int8:       basicType(abi.Int8),
+		abi.Int16:      basicType(abi.Int16),
+		abi.Int32:      basicType(abi.Int32),
+		abi.Int64:      basicType(abi.Int64),
+		abi.Uint:       basicType(abi.Uint),
+		abi.Uint8:      basicType(abi.Uint8),
+		abi.Uint16:     basicType(abi.Uint16),
+		abi.Uint32:     basicType(abi.Uint32),
+		abi.Uint64:     basicType(abi.Uint64),
+		abi.Uintptr:    basicType(abi.Uintptr),
+		abi.Float32:    basicType(abi.Float32),
+		abi.Float64:    basicType(abi.Float64),
+		abi.Complex64:  basicType(abi.Complex64),
+		abi.Complex128: basicType(abi.Complex128),
+	}
+)
+
+var (
+	sizeBasicTypes = [...]uintptr{
+		abi.Bool:       unsafe.Sizeof(false),
+		abi.Int:        unsafe.Sizeof(0),
+		abi.Int8:       1,
+		abi.Int16:      2,
+		abi.Int32:      4,
+		abi.Int64:      8,
+		abi.Uint:       unsafe.Sizeof(uint(0)),
+		abi.Uint8:      1,
+		abi.Uint16:     2,
+		abi.Uint32:     4,
+		abi.Uint64:     8,
+		abi.Uintptr:    unsafe.Sizeof(uintptr(0)),
+		abi.Float32:    4,
+		abi.Float64:    8,
+		abi.Complex64:  8,
+		abi.Complex128: 16,
+	}
+)
+
+func basicType(kind abi.Kind) *Type {
+	return &abi.Type{
+		Size_: sizeBasicTypes[kind],
+		Kind_: uint8(kind),
+	}
+}
diff --git a/ssa/decl.go b/ssa/decl.go
index 18760708..942a1623 100644
--- a/ssa/decl.go
+++ b/ssa/decl.go
@@ -106,6 +106,7 @@ func (g Global) Init(v Expr) {
 // respectively, and is nil in the generic method.
 type aFunction struct {
 	Expr
+	pkg  Package
 	prog Program
 	blks []BasicBlock
 
@@ -116,9 +117,9 @@ type aFunction struct {
 // Function represents a function or method.
 type Function = *aFunction
 
-func newFunction(fn llvm.Value, t Type, prog Program) Function {
+func newFunction(fn llvm.Value, t Type, pkg Package, prog Program) Function {
 	params, hasVArg := newParams(t, prog)
-	return &aFunction{Expr{fn, t}, prog, nil, params, hasVArg}
+	return &aFunction{Expr{fn, t}, pkg, prog, nil, params, hasVArg}
 }
 
 func newParams(fn Type, prog Program) (params []Type, hasVArg bool) {
diff --git a/ssa/expr.go b/ssa/expr.go
index dca906b9..e8aaa3ad 100644
--- a/ssa/expr.go
+++ b/ssa/expr.go
@@ -407,8 +407,76 @@ func (b Builder) ChangeType(t Type, x Expr) (ret Expr) {
 	panic("todo")
 }
 
+// The TypeAssert instruction tests whether interface value X has type
+// AssertedType.
+//
+// If !CommaOk, on success it returns v, the result of the conversion
+// (defined below); on failure it panics.
+//
+// If CommaOk: on success it returns a pair (v, true) where v is the
+// result of the conversion; on failure it returns (z, false) where z
+// is AssertedType's zero value.  The components of the pair must be
+// accessed using the Extract instruction.
+//
+// If Underlying: tests whether interface value X has the underlying
+// type AssertedType.
+//
+// If AssertedType is a concrete type, TypeAssert checks whether the
+// dynamic type in interface X is equal to it, and if so, the result
+// of the conversion is a copy of the value in the interface.
+//
+// If AssertedType is an interface, TypeAssert checks whether the
+// dynamic type of the interface is assignable to it, and if so, the
+// result of the conversion is a copy of the interface value X.
+// If AssertedType is a superinterface of X.Type(), the operation will
+// fail iff the operand is nil.  (Contrast with ChangeInterface, which
+// performs no nil-check.)
+//
+// Type() reflects the actual type of the result, possibly a
+// 2-types.Tuple; AssertedType is the asserted type.
+//
+// Depending on the TypeAssert's purpose, Pos may return:
+//   - the ast.CallExpr.Lparen of an explicit T(e) conversion;
+//   - the ast.TypeAssertExpr.Lparen of an explicit e.(T) operation;
+//   - the ast.CaseClause.Case of a case of a type-switch statement;
+//   - the Ident(m).NamePos of an interface method value i.m
+//     (for which TypeAssert may be used to effect the nil check).
+//
+// Example printed form:
+//
+//	t1 = typeassert t0.(int)
+//	t3 = typeassert,ok t2.(T)
+func (b Builder) TypeAssert(x Expr, assertedTyp Type, commaOk bool) (ret Expr) {
+	if debugInstr {
+		log.Printf("TypeAssert %v, %v, %v\n", x.impl, assertedTyp.t, commaOk)
+	}
+	switch assertedTyp.kind {
+	case vkSigned, vkUnsigned:
+		pkg := b.fn.pkg
+		fnName := "I2Int"
+		if commaOk {
+			fnName = "CheckI2Int"
+		}
+		fn := pkg.rtFunc(fnName)
+		var kind types.BasicKind
+		switch t := assertedTyp.t.(type) {
+		case *types.Basic:
+			kind = t.Kind()
+		default:
+			panic("todo")
+		}
+		typ := b.InlineCall(pkg.rtFunc("Basic"), b.prog.Val(int(kind)))
+		return b.InlineCall(fn, x, typ)
+	}
+	panic("todo")
+}
+
 // -----------------------------------------------------------------------------
 
+func (b Builder) InlineCall(fn Expr, args ...Expr) (ret Expr) {
+	return b.Call(fn, args...)
+}
+
 // The Call instruction represents a function or method call.
 //
 // The Call instruction yields the function result if there is exactly
diff --git a/ssa/package.go b/ssa/package.go
index 85b7c9d2..12bc7df4 100644
--- a/ssa/package.go
+++ b/ssa/package.go
@@ -90,16 +90,12 @@ func Initialize(flags InitFlags) {
 
 // -----------------------------------------------------------------------------
 
-type Runtime interface {
-	Runtime() *types.Package
-}
-
 type aProgram struct {
 	ctx  llvm.Context
 	typs typeutil.Map
 
 	rt    *types.Scope
-	rtget Runtime
+	rtget func() *types.Package
 
 	target *Target
 	td     llvm.TargetData
@@ -136,18 +132,22 @@ func NewProgram(target *Target) Program {
 	return &aProgram{ctx: ctx, target: target, td: td}
 }
 
-// SetRuntime sets the runtime package.
-func (p Program) SetRuntime(runtime Runtime) {
+// SetRuntime sets the runtime.
+func (p Program) SetRuntime(runtime func() *types.Package) {
 	p.rtget = runtime
 }
 
 func (p Program) runtime() *types.Scope {
 	if p.rt == nil {
-		p.rt = p.rtget.Runtime().Scope()
+		p.rt = p.rtget().Scope()
 	}
 	return p.rt
 }
 
+func (p Program) rtType(name string) *types.Named {
+	return p.runtime().Lookup(name).Type().(*types.Named)
+}
+
 // NewPackage creates a new package.
 func (p Program) NewPackage(name, pkgPath string) Package {
 	mod := p.ctx.NewModule(pkgPath)
@@ -230,11 +230,16 @@ func (p Package) NewVar(name string, typ types.Type) Global {
 	return ret
 }
 
+// VarOf returns a global variable by name.
+func (p Package) VarOf(name string) Global {
+	return p.vars[name]
+}
+
 // NewFunc creates a new function.
 func (p Package) NewFunc(name string, sig *types.Signature) Function {
 	t := p.prog.llvmSignature(sig)
 	fn := llvm.AddFunction(p.mod, name, t.ll)
-	ret := newFunction(fn, t, p.prog)
+	ret := newFunction(fn, t, p, p.prog)
 	p.fns[name] = ret
 	return ret
 }
@@ -244,9 +249,14 @@ func (p Package) FuncOf(name string) Function {
 	return p.fns[name]
 }
 
-// VarOf returns a global variable by name.
-func (p Package) VarOf(name string) Global {
-	return p.vars[name]
+func (p Package) rtFunc(fnName string) Expr {
+	fn := p.prog.runtime().Lookup(fnName).(*types.Func)
+	name := FullName(fn.Pkg(), fnName)
+	v, ok := p.fns[name]
+	if !ok {
+		v = p.NewFunc(name, fn.Type().(*types.Signature))
+	}
+	return v.Expr
 }
 
 // -----------------------------------------------------------------------------
diff --git a/ssa/type.go b/ssa/type.go
index 21e438c9..6e5030f4 100644
--- a/ssa/type.go
+++ b/ssa/type.go
@@ -242,9 +242,9 @@ func (p Program) toLLVMType(typ types.Type) Type {
 		elem := p.Type(t.Elem())
 		return &aType{llvm.PointerType(elem.ll, 0), typ, vkInvalid}
 	case *types.Interface:
-		tyIface := p.runtime().Lookup("Interface").(*types.TypeName).Type().(*types.Named)
-		return p.toLLVMNamed(tyIface)
+		return p.toLLVMNamed(p.rtType("Interface"))
 	case *types.Slice:
+		return p.toLLVMNamed(p.rtType("Slice"))
 	case *types.Map:
 	case *types.Struct:
 		return p.toLLVMStruct(t)