diff --git a/go.mod b/go.mod
index f8b4cbf2..8768b130 100644
--- a/go.mod
+++ b/go.mod
@@ -6,7 +6,7 @@ require (
 	github.com/aykevl/go-wasm v0.0.1
 	github.com/blakesmith/ar v0.0.0-20190502131153-809d4375e1fb
 	github.com/goplus/gop v1.2.6
-	github.com/goplus/llvm v0.7.1-0.20240417171659-4fb15c5dc82a
+	github.com/goplus/llvm v0.7.1-0.20240418070213-5013f6a4299b
 	github.com/qiniu/x v1.13.10
 	golang.org/x/tools v0.19.0
 )
diff --git a/go.sum b/go.sum
index dda1662c..b557f82b 100644
--- a/go.sum
+++ b/go.sum
@@ -10,6 +10,8 @@ github.com/goplus/llvm v0.7.0 h1:b8XzmRA97U0V0BPSaYuZ2vw+lLO2JSpRLMtR6dAenIo=
 github.com/goplus/llvm v0.7.0/go.mod h1:PeVK8GgzxwAYCiMiUAJb5wJR6xbhj989tu9oulKLLT4=
 github.com/goplus/llvm v0.7.1-0.20240417171659-4fb15c5dc82a h1:pKOqI/f4lyPAlto2MT0JJsDCNMvRyF8jBT2saegwIK8=
 github.com/goplus/llvm v0.7.1-0.20240417171659-4fb15c5dc82a/go.mod h1:PeVK8GgzxwAYCiMiUAJb5wJR6xbhj989tu9oulKLLT4=
+github.com/goplus/llvm v0.7.1-0.20240418070213-5013f6a4299b h1:sRVmYXGgKjqgaoVQ1bshnw9Ar77stDtjHC4A/PDJ0fk=
+github.com/goplus/llvm v0.7.1-0.20240418070213-5013f6a4299b/go.mod h1:PeVK8GgzxwAYCiMiUAJb5wJR6xbhj989tu9oulKLLT4=
 github.com/goplus/mod v0.13.10 h1:5Om6KOvo31daN7N30kWU1vC5zhsJPM+uPbcEN/FnlzE=
 github.com/goplus/mod v0.13.10/go.mod h1:HDuPZgpWiaTp3PUolFgsiX+Q77cbUWB/mikVHfYND3c=
 github.com/qiniu/x v1.13.10 h1:J4Z3XugYzAq85SlyAfqlKVrbf05glMbAOh+QncsDQpE=
diff --git a/ssa/builder.go b/ssa/builder.go
index 3b6ec4ea..18ec7b96 100644
--- a/ssa/builder.go
+++ b/ssa/builder.go
@@ -20,13 +20,35 @@ import (
 	"github.com/goplus/llvm"
 )
 
-type Builder struct {
-	impl llvm.Builder
-}
-
+// -----------------------------------------------------------------------------
+/*
 type BasicBlock struct {
 	impl llvm.BasicBlock
 }
+*/
+// -----------------------------------------------------------------------------
 
-func (p BasicBlock) End() {
+type aBuilder struct {
+	impl llvm.Builder
+	prog Program
 }
+
+type Builder = *aBuilder
+
+func (b Builder) Return(results ...Expr) Builder {
+	switch n := len(results); n {
+	case 0:
+		b.impl.CreateRetVoid()
+	case 1:
+		b.impl.CreateRet(results[0].impl)
+	default:
+		rets := make([]llvm.Value, n)
+		for i, v := range results {
+			rets[i] = v.impl
+		}
+		b.impl.CreateAggregateRet(rets)
+	}
+	return b
+}
+
+// -----------------------------------------------------------------------------
diff --git a/ssa/decl.go b/ssa/decl.go
index 7d0843ae..a42f9cb6 100644
--- a/ssa/decl.go
+++ b/ssa/decl.go
@@ -20,6 +20,8 @@ import (
 	"github.com/goplus/llvm"
 )
 
+// -----------------------------------------------------------------------------
+
 // A NamedConst is a Member of a Package representing a package-level
 // named constant.
 //
@@ -33,6 +35,8 @@ type aNamedConst struct {
 
 type NamedConst = *aNamedConst
 
+// -----------------------------------------------------------------------------
+
 // A Global is a named Value holding the address of a package-level
 // variable.
 //
@@ -40,10 +44,13 @@ type NamedConst = *aNamedConst
 // identifier.
 type aGlobal struct {
 	impl llvm.Value
+	Type
 }
 
 type Global = *aGlobal
 
+// -----------------------------------------------------------------------------
+
 // Function represents the parameters, results, and code of a function
 // or method.
 //
@@ -95,12 +102,20 @@ type Global = *aGlobal
 // respectively, and is nil in the generic method.
 type aFunction struct {
 	impl llvm.Value
+	Type
+
 	prog Program
 }
 
 type Function = *aFunction
 
-func (p *aFunction) BodyStart() *BasicBlock {
-	body := llvm.AddBasicBlock(p.impl, "entry")
-	return &BasicBlock{body}
+func (p *aFunction) MakeBody(label string) Builder {
+	body := llvm.AddBasicBlock(p.impl, label)
+	prog := p.prog
+	b := prog.ctx.NewBuilder()
+	b.Finalize()
+	b.SetInsertPointAtEnd(body)
+	return &aBuilder{b, prog}
 }
+
+// -----------------------------------------------------------------------------
diff --git a/ssa/expr.go b/ssa/expr.go
index 4c151a79..5de23502 100644
--- a/ssa/expr.go
+++ b/ssa/expr.go
@@ -15,3 +15,21 @@
  */
 
 package ssa
+
+import (
+	"github.com/goplus/llvm"
+)
+
+func (p Program) Val(v interface{}) Expr {
+	switch v := v.(type) {
+	case int:
+		t := p.Int()
+		ret := llvm.ConstInt(t.ll, uint64(v), false)
+		return Expr{ret, t}
+	case float64:
+		t := p.Float64()
+		ret := llvm.ConstFloat(t.ll, v)
+		return Expr{ret, t}
+	}
+	panic("todo")
+}
diff --git a/ssa/operator.go b/ssa/operator.go
index 31232763..7a318386 100644
--- a/ssa/operator.go
+++ b/ssa/operator.go
@@ -24,9 +24,9 @@ import (
 
 type valueKind = int
 
-type Value struct {
+type Expr struct {
 	impl llvm.Value
-	kind valueKind
+	Type
 }
 
 const (
@@ -42,6 +42,7 @@ const (
 	vkComplex
 	vkString
 	vkBool
+	vkFunc
 )
 
 var mathOpToLLVM = []llvm.Opcode{
@@ -134,45 +135,44 @@ func isPredOp(op token.Token) bool {
 // ADD SUB MUL QUO REM          + - * / %
 // AND OR XOR SHL SHR AND_NOT   & | ^ << >> &^
 // EQL NEQ LSS LEQ GTR GEQ      == != < <= < >=
-func (b Builder) BinOp(op token.Token, x, y Value) (v Value) {
+func (b Builder) BinOp(op token.Token, x, y Expr) Expr {
 	switch {
 	case isMathOp(op): // op: + - * / %
-		switch x.kind {
+		kind := x.kind
+		switch kind {
 		case vkString, vkComplex:
 			panic("todo")
 		}
-		idx := mathOpIdx(op, x.kind)
+		idx := mathOpIdx(op, kind)
 		if llop := mathOpToLLVM[idx]; llop != 0 {
-			v.impl = llvm.CreateBinOp(b.impl, llop, x.impl, y.impl)
-			return
+			return Expr{llvm.CreateBinOp(b.impl, llop, x.impl, y.impl), x.Type}
 		}
 	case isLogicOp(op): // op: & | ^ << >> &^
 		if op == token.AND_NOT {
 			panic("todo")
 		}
+		kind := x.kind
 		llop := logicOpToLLVM[op-logicOpBase]
-		if op == token.SHR && x.kind == vkUnsigned {
+		if op == token.SHR && kind == vkUnsigned {
 			llop = llvm.AShr
 		}
-		v.impl = llvm.CreateBinOp(b.impl, llop, x.impl, y.impl)
-		return
+		return Expr{llvm.CreateBinOp(b.impl, llop, x.impl, y.impl), x.Type}
 	case isPredOp(op): // op: == != < <= < >=
-		switch x.kind {
+		tret := b.prog.Bool()
+		kind := x.kind
+		switch kind {
 		case vkSigned:
 			pred := intPredOpToLLVM[op-predOpBase]
-			v.impl = llvm.CreateICmp(b.impl, pred, x.impl, y.impl)
-			return
+			return Expr{llvm.CreateICmp(b.impl, pred, x.impl, y.impl), tret}
 		case vkUnsigned:
 			pred := uintPredOpToLLVM[op-predOpBase]
-			v.impl = llvm.CreateICmp(b.impl, pred, x.impl, y.impl)
-			return
+			return Expr{llvm.CreateICmp(b.impl, pred, x.impl, y.impl), tret}
 		case vkFloat:
 			pred := floatPredOpToLLVM[op-predOpBase]
-			v.impl = llvm.ConstFCmp(pred, x.impl, y.impl)
-			return
+			return Expr{llvm.ConstFCmp(pred, x.impl, y.impl), tret}
 		case vkString, vkComplex, vkBool:
 			panic("todo")
 		}
 	}
-	return
+	panic("todo")
 }
diff --git a/ssa/package.go b/ssa/package.go
index b0934708..f38e4565 100644
--- a/ssa/package.go
+++ b/ssa/package.go
@@ -27,7 +27,6 @@ import (
 // A Program is a partial or complete Go program converted to SSA form.
 type aProgram struct {
 	ctx  llvm.Context
-	b    Builder
 	typs typeutil.Map
 
 	target *Target
@@ -35,12 +34,17 @@ type aProgram struct {
 	// tm  llvm.TargetMachine
 
 	intType   llvm.Type
+	int1Type  llvm.Type
 	int8Type  llvm.Type
 	int16Type llvm.Type
 	int32Type llvm.Type
 	int64Type llvm.Type
 	voidType  llvm.Type
 	voidPtrTy llvm.Type
+
+	boolTy Type
+	intTy  Type
+	f64Ty  Type
 }
 
 type Program = *aProgram
@@ -51,20 +55,35 @@ func NewProgram(target *Target) Program {
 	}
 	ctx := llvm.NewContext()
 	ctx.Finalize()
-	b := ctx.NewBuilder()
-	b.Finalize()
 	td := llvm.NewTargetData("") // TODO(xsw): target config
-	return &aProgram{ctx: ctx, b: Builder{b}, target: target, td: td}
+	return &aProgram{ctx: ctx, target: target, td: td}
 }
 
-func (p *aProgram) NewPackage(name, pkgPath string) Package {
+func (p Program) NewPackage(name, pkgPath string) Package {
 	mod := p.ctx.NewModule(pkgPath)
 	mod.Finalize()
 	return &aPackage{mod, p}
 }
 
-func (p *aProgram) Builder() Builder {
-	return p.b
+func (p Program) Bool() Type {
+	if p.boolTy == nil {
+		p.boolTy = p.llvmType(types.Typ[types.Bool])
+	}
+	return p.boolTy
+}
+
+func (p Program) Int() Type {
+	if p.intTy == nil {
+		p.intTy = p.llvmType(types.Typ[types.Int])
+	}
+	return p.intTy
+}
+
+func (p Program) Float64() Type {
+	if p.f64Ty == nil {
+		p.f64Ty = p.llvmType(types.Typ[types.Float64])
+	}
+	return p.f64Ty
 }
 
 // A Package is a single analyzed Go package containing Members for
@@ -82,21 +101,23 @@ type aPackage struct {
 
 type Package = *aPackage
 
-func (p *aPackage) NewConst(name string, val constant.Value) NamedConst {
+func (p Package) NewConst(name string, val constant.Value) NamedConst {
 	return &aNamedConst{}
 }
 
-func (p *aPackage) NewVar(name string, typ types.Type) Global {
-	gbl := llvm.AddGlobal(p.mod, p.prog.llvmType(typ), name)
-	return &aGlobal{gbl}
+func (p Package) NewVar(name string, typ types.Type) Global {
+	t := p.prog.llvmType(typ)
+	gbl := llvm.AddGlobal(p.mod, t.ll, name)
+	return &aGlobal{gbl, t}
 }
 
-func (p *aPackage) NewFunc(name string, sig *types.Signature) Function {
-	fn := llvm.AddFunction(p.mod, name, p.prog.llvmSignature(sig))
-	return &aFunction{fn, p.prog}
+func (p Package) NewFunc(name string, sig *types.Signature) Function {
+	t := p.prog.llvmSignature(sig)
+	fn := llvm.AddFunction(p.mod, name, t.ll)
+	return &aFunction{fn, t, p.prog}
 }
 
-func (p *aPackage) String() string {
+func (p Package) String() string {
 	return p.mod.String()
 }
 
diff --git a/ssa/ssa_test.go b/ssa/ssa_test.go
index 8bd2aabe..49adf334 100644
--- a/ssa/ssa_test.go
+++ b/ssa/ssa_test.go
@@ -79,7 +79,7 @@ source_filename = "foo/bar"
 `)
 }
 
-func TestFunc(t *testing.T) {
+func TestDeclFunc(t *testing.T) {
 	prog := NewProgram(nil)
 	pkg := prog.NewPackage("bar", "foo/bar")
 	params := types.NewTuple(types.NewVar(0, nil, "a", types.Typ[types.Int]))
@@ -91,3 +91,19 @@ source_filename = "foo/bar"
 declare void @fn(i64)
 `)
 }
+
+func TestBasicFunc(t *testing.T) {
+	prog := NewProgram(nil)
+	pkg := prog.NewPackage("bar", "foo/bar")
+	rets := types.NewTuple(types.NewVar(0, nil, "a", types.Typ[types.Int]))
+	sig := types.NewSignatureType(nil, nil, nil, nil, rets, false)
+	b := pkg.NewFunc("fn", sig).MakeBody("")
+	b.Return(prog.Val(1))
+	assertPkg(t, pkg, `; ModuleID = 'foo/bar'
+source_filename = "foo/bar"
+
+define i64 @fn() {
+  ret i64 1
+}
+`)
+}
diff --git a/ssa/type.go b/ssa/type.go
index 39132d64..c0ae36c5 100644
--- a/ssa/type.go
+++ b/ssa/type.go
@@ -22,107 +22,136 @@ import (
 	"github.com/goplus/llvm"
 )
 
-/*
-// A Type is a Member of a Package representing a package-level named type.
-type Type struct {
-	impl llvm.Type
-}
-*/
+// -----------------------------------------------------------------------------
 
-func (p *aProgram) llvmType(typ types.Type) llvm.Type {
+type aType struct {
+	ll   llvm.Type
+	t    types.Type
+	kind valueKind
+}
+
+type Type = *aType
+
+func (p Program) llvmType(typ types.Type) Type {
 	if v := p.typs.At(typ); v != nil {
-		return v.(llvm.Type)
+		return v.(Type)
 	}
 	ret := p.toLLVMType(typ)
 	p.typs.Set(typ, ret)
 	return ret
 }
 
-func (p *aProgram) llvmSignature(sig *types.Signature) llvm.Type {
+func (p Program) llvmSignature(sig *types.Signature) Type {
 	if v := p.typs.At(sig); v != nil {
-		return v.(llvm.Type)
+		return v.(Type)
 	}
 	ret := p.toLLVMFunc(sig)
 	p.typs.Set(sig, ret)
 	return ret
 }
 
-func (p *aProgram) tyVoidPtr() llvm.Type {
+func (p Program) tyVoidPtr() llvm.Type {
 	if p.voidPtrTy.IsNil() {
 		p.voidPtrTy = llvm.PointerType(p.tyVoid(), 0)
 	}
 	return p.voidPtrTy
 }
 
-func (p *aProgram) tyVoid() llvm.Type {
+func (p Program) tyVoid() llvm.Type {
 	if p.voidType.IsNil() {
 		p.voidType = p.ctx.VoidType()
 	}
 	return p.voidType
 }
 
-func (p *aProgram) tyInt() llvm.Type {
+func (p Program) tyInt1() llvm.Type {
+	if p.int1Type.IsNil() {
+		p.int1Type = p.ctx.Int1Type()
+	}
+	return p.int1Type
+}
+
+func (p Program) tyInt() llvm.Type {
 	if p.intType.IsNil() {
 		p.intType = llvmIntType(p.ctx, p.td.PointerSize())
 	}
 	return p.intType
 }
 
-func (p *aProgram) tyInt8() llvm.Type {
+func llvmIntType(ctx llvm.Context, size int) llvm.Type {
+	if size <= 4 {
+		return ctx.Int32Type()
+	}
+	return ctx.Int64Type()
+}
+
+func (p Program) tyInt8() llvm.Type {
 	if p.int8Type.IsNil() {
 		p.int8Type = p.ctx.Int8Type()
 	}
 	return p.int8Type
 }
 
-func (p *aProgram) tyInt16() llvm.Type {
+func (p Program) tyInt16() llvm.Type {
 	if p.int16Type.IsNil() {
 		p.int16Type = p.ctx.Int16Type()
 	}
 	return p.int16Type
 }
 
-func (p *aProgram) tyInt32() llvm.Type {
+func (p Program) tyInt32() llvm.Type {
 	if p.int32Type.IsNil() {
 		p.int32Type = p.ctx.Int32Type()
 	}
 	return p.int32Type
 }
 
-func (p *aProgram) tyInt64() llvm.Type {
+func (p Program) tyInt64() llvm.Type {
 	if p.int64Type.IsNil() {
 		p.int64Type = p.ctx.Int64Type()
 	}
 	return p.int64Type
 }
 
-func (p *aProgram) toLLVMType(typ types.Type) llvm.Type {
+func (p Program) toLLVMType(typ types.Type) Type {
 	switch t := typ.(type) {
 	case *types.Basic:
 		switch t.Kind() {
-		case types.Int, types.Uint, types.Uintptr:
-			return p.tyInt()
-		case types.Bool, types.Uint8, types.Int8:
-			return p.tyInt8()
-		case types.Int16, types.Uint16:
-			return p.tyInt16()
-		case types.Int32, types.Uint32:
-			return p.tyInt32()
-		case types.Int64, types.Uint64:
-			return p.tyInt64()
+		case types.Int:
+			return &aType{p.tyInt(), typ, vkSigned}
+		case types.Uint, types.Uintptr:
+			return &aType{p.tyInt(), typ, vkUnsigned}
+		case types.Bool:
+			return &aType{p.tyInt1(), typ, vkBool}
+		case types.Uint8:
+			return &aType{p.tyInt8(), typ, vkUnsigned}
+		case types.Int8:
+			return &aType{p.tyInt8(), typ, vkSigned}
+		case types.Int16:
+			return &aType{p.tyInt16(), typ, vkSigned}
+		case types.Uint16:
+			return &aType{p.tyInt16(), typ, vkUnsigned}
+		case types.Int32:
+			return &aType{p.tyInt32(), typ, vkSigned}
+		case types.Uint32:
+			return &aType{p.tyInt32(), typ, vkUnsigned}
+		case types.Int64:
+			return &aType{p.tyInt64(), typ, vkSigned}
+		case types.Uint64:
+			return &aType{p.tyInt64(), typ, vkUnsigned}
 		case types.Float32:
-			return p.ctx.FloatType()
+			return &aType{p.ctx.FloatType(), typ, vkFloat}
 		case types.Float64:
-			return p.ctx.DoubleType()
+			return &aType{p.ctx.DoubleType(), typ, vkFloat}
 		case types.Complex64:
 		case types.Complex128:
 		case types.String:
 		case types.UnsafePointer:
-			return p.tyVoidPtr()
+			return &aType{p.tyVoidPtr(), typ, vkInvalid}
 		}
 	case *types.Pointer:
 		elem := p.llvmType(t.Elem())
-		return llvm.PointerType(elem, 0)
+		return &aType{llvm.PointerType(elem.ll, 0), typ, vkInvalid}
 	case *types.Slice:
 	case *types.Map:
 	case *types.Struct:
@@ -133,54 +162,47 @@ func (p *aProgram) toLLVMType(typ types.Type) llvm.Type {
 		return p.toLLVMFunc(t)
 	case *types.Array:
 		elem := p.llvmType(t.Elem())
-		return llvm.ArrayType(elem, int(t.Len()))
+		return &aType{llvm.ArrayType(elem.ll, int(t.Len())), typ, vkInvalid}
 	case *types.Chan:
 	}
 	panic("todo")
 }
 
-func llvmIntType(ctx llvm.Context, size int) llvm.Type {
-	if size <= 4 {
-		return ctx.Int32Type()
-	}
-	return ctx.Int64Type()
-}
-
-func (p *aProgram) toLLVMNamedStruct(name string, typ *types.Struct) llvm.Type {
+func (p Program) toLLVMNamedStruct(name string, typ *types.Struct) llvm.Type {
 	t := p.ctx.StructCreateNamed(name)
 	fields := p.toLLVMFields(typ)
 	t.StructSetBody(fields, false)
 	return t
 }
 
-func (p *aProgram) toLLVMStruct(typ *types.Struct) llvm.Type {
+func (p Program) toLLVMStruct(typ *types.Struct) Type {
 	fields := p.toLLVMFields(typ)
-	return p.ctx.StructType(fields, false)
+	return &aType{p.ctx.StructType(fields, false), typ, vkInvalid}
 }
 
-func (p *aProgram) toLLVMFields(typ *types.Struct) []llvm.Type {
+func (p Program) toLLVMFields(typ *types.Struct) []llvm.Type {
 	n := typ.NumFields()
 	fields := make([]llvm.Type, n)
 	for i := 0; i < n; i++ {
-		fields[i] = p.llvmType(typ.Field(i).Type())
+		fields[i] = p.llvmType(typ.Field(i).Type()).ll
 	}
 	return fields
 }
 
-func (p *aProgram) toLLVMTuple(t *types.Tuple) llvm.Type {
+func (p Program) toLLVMTuple(t *types.Tuple) llvm.Type {
 	return p.ctx.StructType(p.toLLVMTypes(t), false)
 }
 
-func (p *aProgram) toLLVMTypes(t *types.Tuple) []llvm.Type {
+func (p Program) toLLVMTypes(t *types.Tuple) []llvm.Type {
 	n := t.Len()
 	ret := make([]llvm.Type, n)
 	for i := 0; i < n; i++ {
-		ret[i] = p.llvmType(t.At(i).Type())
+		ret[i] = p.llvmType(t.At(i).Type()).ll
 	}
 	return ret
 }
 
-func (p *aProgram) toLLVMFunc(sig *types.Signature) llvm.Type {
+func (p Program) toLLVMFunc(sig *types.Signature) Type {
 	params := p.toLLVMTypes(sig.Params())
 	results := sig.Results()
 	var ret llvm.Type
@@ -188,18 +210,21 @@ func (p *aProgram) toLLVMFunc(sig *types.Signature) llvm.Type {
 	case 0:
 		ret = p.tyVoid()
 	case 1:
-		ret = p.llvmType(results.At(0).Type())
+		ret = p.llvmType(results.At(0).Type()).ll
 	default:
 		ret = p.toLLVMTuple(results)
 	}
-	return llvm.FunctionType(ret, params, sig.Variadic())
+	ft := llvm.FunctionType(ret, params, sig.Variadic())
+	return &aType{ft, sig, vkFunc}
 }
 
-func (p *aProgram) toLLVMNamed(typ *types.Named) llvm.Type {
+func (p Program) toLLVMNamed(typ *types.Named) Type {
 	name := typ.Obj().Name()
 	switch typ := typ.Underlying().(type) {
 	case *types.Struct:
-		return p.toLLVMNamedStruct(name, typ)
+		return &aType{p.toLLVMNamedStruct(name, typ), typ, vkInvalid}
 	}
 	panic("todo")
 }
+
+// -----------------------------------------------------------------------------