start = n
			end = n
		} else {
			end.then = n
			end = n
		}
	}
	for _, stmt := range body {
		switch stmt := stmt.(type) {
		case *ast.ExprStmt:
			if x, _ := stmt.X.(*ast.CallExpr); x != nil {
				funstr := exprToString(x.Fun)
				if funstr == "putattr" {
					form, _ := x.Args[3].(*ast.Ident)
					if form == nil {
						t.Fatalf("%s invalid use of putattr", fset.Position(x.Pos()))
					}

// do not return, so the builder can remove infeasible graph edges
// following such calls.  The builder calls mayReturn only for a
// CallExpr beneath an ExprStmt.
func New(body *ast.BlockStmt, mayReturn func(*ast.CallExpr) bool) *CFG {
	b := builder{
		mayReturn: mayReturn,
		cfg:       new(CFG),
	}
	b.current = b.newBlock(KindBody, body)
	b.stmt(body)

func (f *File) saveExprs(x interface{}, context astContext) {
	switch x := x.(type) {
	case *ast.Expr:
		switch (*x).(type) {
		case *ast.SelectorExpr:
			f.saveRef(x, context)
		}
	case *ast.CallExpr:
		f.saveCall(x, context)
	}
}

// Save references to C.xxx for later processing.
func (f *File) saveRef(n *ast.Expr, context astContext) {
	sel := (*n).(*ast.SelectorExpr)

		return 1 << nBasicLit
	case *ast.BinaryExpr:
		return 1 << nBinaryExpr
	case *ast.BlockStmt:
		return 1 << nBlockStmt
	case *ast.BranchStmt:
		return 1 << nBranchStmt
	case *ast.CallExpr:
		return 1 << nCallExpr
	case *ast.CaseClause:
		return 1 << nCaseClause
	case *ast.ChanType:
		return 1 << nChanType
	case *ast.CommClause:
		return 1 << nCommClause
	case *ast.Comment:
		return 1 << nComment

		return check.isTerminating(s.Stmt, s.Label.Value)

	case *syntax.ExprStmt:
		// calling the predeclared (possibly parenthesized) panic() function is terminating
		if call, ok := syntax.Unparen(s.X).(*syntax.CallExpr); ok && check.isPanic[call] {
			return true
		}

	case *syntax.ReturnStmt:
		return true

	case *syntax.BranchStmt:
		if s.Tok == syntax.Goto || s.Tok == syntax.Fallthrough {
			return true
		}

	case *ast.LabeledStmt:
		return check.isTerminating(s.Stmt, s.Label.Name)

	case *ast.ExprStmt:
		// calling the predeclared (possibly parenthesized) panic() function is terminating
		if call, ok := ast.Unparen(s.X).(*ast.CallExpr); ok && check.isPanic[call] {
			return true
		}

	case *ast.ReturnStmt:
		return true

	case *ast.BranchStmt:
		if s.Tok == token.GOTO || s.Tok == token.FALLTHROUGH {
			return true
		}

// HasSideEffects reports whether evaluation of e has side effects.
func HasSideEffects(info *types.Info, e ast.Expr) bool {
	safe := true
	ast.Inspect(e, func(node ast.Node) bool {
		switch n := node.(type) {
		case *ast.CallExpr:
			typVal := info.Types[n.Fun]
			switch {
			case typVal.IsType():
				// Type conversion, which is safe.
			case typVal.IsBuiltin():
				// Builtin func, conservatively assumed to not
				// be safe for now.

		}
	}

	nodeFilter := []ast.Node{
		(*ast.ExprStmt)(nil),
	}
	inspect.Preorder(nodeFilter, func(n ast.Node) {
		call, ok := astutil.Unparen(n.(*ast.ExprStmt).X).(*ast.CallExpr)
		if !ok {
			return // not a call statement
		}

		// Call to function or method?
		fn, ok := typeutil.Callee(pass.TypesInfo, call).(*types.Func)
		if !ok {
			return // e.g. var or builtin
		}

				WriteExpr(buf, x.Max)
			}
		}
		buf.WriteByte(']')

	case *ast.TypeAssertExpr:
		WriteExpr(buf, x.X)
		buf.WriteString(".(")
		WriteExpr(buf, x.Type)
		buf.WriteByte(')')

	case *ast.CallExpr:
		WriteExpr(buf, x.Fun)
		buf.WriteByte('(')
		writeExprList(buf, x.Args)
		if hasDots(x) {
			buf.WriteString("...")
		}
		buf.WriteByte(')')

	case *ast.StarExpr:
		buf.WriteByte('*')

		}
		return stackTempAddr(init, t)
	}
	types.CalcSize(t)
	n.MarkNonNil()
	return n
}

func walkMinMax(n *ir.CallExpr, init *ir.Nodes) ir.Node {
	init.Append(ir.TakeInit(n)...)
	walkExprList(n.Args, init)
	return n
}

// generate code for print.
func walkPrint(nn *ir.CallExpr, init *ir.Nodes) ir.Node {
	// Hoist all the argument evaluation up before the lock.
	walkExprListCheap(nn.Args, init)