Current File : //usr/local/go/src/cmd/compile/internal/walk/order.go
// Copyright 2012 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 walk
import (
"fmt"
"go/constant"
"internal/buildcfg"
"cmd/compile/internal/base"
"cmd/compile/internal/escape"
"cmd/compile/internal/ir"
"cmd/compile/internal/reflectdata"
"cmd/compile/internal/staticinit"
"cmd/compile/internal/typecheck"
"cmd/compile/internal/types"
"cmd/internal/src"
)
// Rewrite tree to use separate statements to enforce
// order of evaluation. Makes walk easier, because it
// can (after this runs) reorder at will within an expression.
//
// Rewrite m[k] op= r into m[k] = m[k] op r if op is / or %.
//
// Introduce temporaries as needed by runtime routines.
// For example, the map runtime routines take the map key
// by reference, so make sure all map keys are addressable
// by copying them to temporaries as needed.
// The same is true for channel operations.
//
// Arrange that map index expressions only appear in direct
// assignments x = m[k] or m[k] = x, never in larger expressions.
//
// Arrange that receive expressions only appear in direct assignments
// x = <-c or as standalone statements <-c, never in larger expressions.
// TODO(rsc): The temporary introduction during multiple assignments
// should be moved into this file, so that the temporaries can be cleaned
// and so that conversions implicit in the OAS2FUNC and OAS2RECV
// nodes can be made explicit and then have their temporaries cleaned.
// TODO(rsc): Goto and multilevel break/continue can jump over
// inserted VARKILL annotations. Work out a way to handle these.
// The current implementation is safe, in that it will execute correctly.
// But it won't reuse temporaries as aggressively as it might, and
// it can result in unnecessary zeroing of those variables in the function
// prologue.
// orderState holds state during the ordering process.
type orderState struct {
out []ir.Node // list of generated statements
temp []*ir.Name // stack of temporary variables
free map[string][]*ir.Name // free list of unused temporaries, by type.LongString().
edit func(ir.Node) ir.Node // cached closure of o.exprNoLHS
}
// Order rewrites fn.Nbody to apply the ordering constraints
// described in the comment at the top of the file.
func order(fn *ir.Func) {
if base.Flag.W > 1 {
s := fmt.Sprintf("\nbefore order %v", fn.Sym())
ir.DumpList(s, fn.Body)
}
orderBlock(&fn.Body, map[string][]*ir.Name{})
}
// append typechecks stmt and appends it to out.
func (o *orderState) append(stmt ir.Node) {
o.out = append(o.out, typecheck.Stmt(stmt))
}
// newTemp allocates a new temporary with the given type,
// pushes it onto the temp stack, and returns it.
// If clear is true, newTemp emits code to zero the temporary.
func (o *orderState) newTemp(t *types.Type, clear bool) *ir.Name {
var v *ir.Name
// Note: LongString is close to the type equality we want,
// but not exactly. We still need to double-check with types.Identical.
key := t.LongString()
a := o.free[key]
for i, n := range a {
if types.Identical(t, n.Type()) {
v = a[i]
a[i] = a[len(a)-1]
a = a[:len(a)-1]
o.free[key] = a
break
}
}
if v == nil {
v = typecheck.Temp(t)
}
if clear {
o.append(ir.NewAssignStmt(base.Pos, v, nil))
}
o.temp = append(o.temp, v)
return v
}
// copyExpr behaves like newTemp but also emits
// code to initialize the temporary to the value n.
func (o *orderState) copyExpr(n ir.Node) *ir.Name {
return o.copyExpr1(n, false)
}
// copyExprClear is like copyExpr but clears the temp before assignment.
// It is provided for use when the evaluation of tmp = n turns into
// a function call that is passed a pointer to the temporary as the output space.
// If the call blocks before tmp has been written,
// the garbage collector will still treat the temporary as live,
// so we must zero it before entering that call.
// Today, this only happens for channel receive operations.
// (The other candidate would be map access, but map access
// returns a pointer to the result data instead of taking a pointer
// to be filled in.)
func (o *orderState) copyExprClear(n ir.Node) *ir.Name {
return o.copyExpr1(n, true)
}
func (o *orderState) copyExpr1(n ir.Node, clear bool) *ir.Name {
t := n.Type()
v := o.newTemp(t, clear)
o.append(ir.NewAssignStmt(base.Pos, v, n))
return v
}
// cheapExpr returns a cheap version of n.
// The definition of cheap is that n is a variable or constant.
// If not, cheapExpr allocates a new tmp, emits tmp = n,
// and then returns tmp.
func (o *orderState) cheapExpr(n ir.Node) ir.Node {
if n == nil {
return nil
}
switch n.Op() {
case ir.ONAME, ir.OLITERAL, ir.ONIL:
return n
case ir.OLEN, ir.OCAP:
n := n.(*ir.UnaryExpr)
l := o.cheapExpr(n.X)
if l == n.X {
return n
}
a := ir.SepCopy(n).(*ir.UnaryExpr)
a.X = l
return typecheck.Expr(a)
}
return o.copyExpr(n)
}
// safeExpr returns a safe version of n.
// The definition of safe is that n can appear multiple times
// without violating the semantics of the original program,
// and that assigning to the safe version has the same effect
// as assigning to the original n.
//
// The intended use is to apply to x when rewriting x += y into x = x + y.
func (o *orderState) safeExpr(n ir.Node) ir.Node {
switch n.Op() {
case ir.ONAME, ir.OLITERAL, ir.ONIL:
return n
case ir.OLEN, ir.OCAP:
n := n.(*ir.UnaryExpr)
l := o.safeExpr(n.X)
if l == n.X {
return n
}
a := ir.SepCopy(n).(*ir.UnaryExpr)
a.X = l
return typecheck.Expr(a)
case ir.ODOT:
n := n.(*ir.SelectorExpr)
l := o.safeExpr(n.X)
if l == n.X {
return n
}
a := ir.SepCopy(n).(*ir.SelectorExpr)
a.X = l
return typecheck.Expr(a)
case ir.ODOTPTR:
n := n.(*ir.SelectorExpr)
l := o.cheapExpr(n.X)
if l == n.X {
return n
}
a := ir.SepCopy(n).(*ir.SelectorExpr)
a.X = l
return typecheck.Expr(a)
case ir.ODEREF:
n := n.(*ir.StarExpr)
l := o.cheapExpr(n.X)
if l == n.X {
return n
}
a := ir.SepCopy(n).(*ir.StarExpr)
a.X = l
return typecheck.Expr(a)
case ir.OINDEX, ir.OINDEXMAP:
n := n.(*ir.IndexExpr)
var l ir.Node
if n.X.Type().IsArray() {
l = o.safeExpr(n.X)
} else {
l = o.cheapExpr(n.X)
}
r := o.cheapExpr(n.Index)
if l == n.X && r == n.Index {
return n
}
a := ir.SepCopy(n).(*ir.IndexExpr)
a.X = l
a.Index = r
return typecheck.Expr(a)
default:
base.Fatalf("order.safeExpr %v", n.Op())
return nil // not reached
}
}
// isaddrokay reports whether it is okay to pass n's address to runtime routines.
// Taking the address of a variable makes the liveness and optimization analyses
// lose track of where the variable's lifetime ends. To avoid hurting the analyses
// of ordinary stack variables, those are not 'isaddrokay'. Temporaries are okay,
// because we emit explicit VARKILL instructions marking the end of those
// temporaries' lifetimes.
func isaddrokay(n ir.Node) bool {
return ir.IsAddressable(n) && (n.Op() != ir.ONAME || n.(*ir.Name).Class == ir.PEXTERN || ir.IsAutoTmp(n))
}
// addrTemp ensures that n is okay to pass by address to runtime routines.
// If the original argument n is not okay, addrTemp creates a tmp, emits
// tmp = n, and then returns tmp.
// The result of addrTemp MUST be assigned back to n, e.g.
// n.Left = o.addrTemp(n.Left)
func (o *orderState) addrTemp(n ir.Node) ir.Node {
if n.Op() == ir.OLITERAL || n.Op() == ir.ONIL {
// TODO: expand this to all static composite literal nodes?
n = typecheck.DefaultLit(n, nil)
types.CalcSize(n.Type())
vstat := readonlystaticname(n.Type())
var s staticinit.Schedule
s.StaticAssign(vstat, 0, n, n.Type())
if s.Out != nil {
base.Fatalf("staticassign of const generated code: %+v", n)
}
vstat = typecheck.Expr(vstat).(*ir.Name)
return vstat
}
if isaddrokay(n) {
return n
}
return o.copyExpr(n)
}
// mapKeyTemp prepares n to be a key in a map runtime call and returns n.
// It should only be used for map runtime calls which have *_fast* versions.
func (o *orderState) mapKeyTemp(t *types.Type, n ir.Node) ir.Node {
// Most map calls need to take the address of the key.
// Exception: map*_fast* calls. See golang.org/issue/19015.
alg := mapfast(t)
if alg == mapslow {
return o.addrTemp(n)
}
var kt *types.Type
switch alg {
case mapfast32:
kt = types.Types[types.TUINT32]
case mapfast64:
kt = types.Types[types.TUINT64]
case mapfast32ptr, mapfast64ptr:
kt = types.Types[types.TUNSAFEPTR]
case mapfaststr:
kt = types.Types[types.TSTRING]
}
nt := n.Type()
switch {
case nt == kt:
return n
case nt.Kind() == kt.Kind(), nt.IsPtrShaped() && kt.IsPtrShaped():
// can directly convert (e.g. named type to underlying type, or one pointer to another)
return typecheck.Expr(ir.NewConvExpr(n.Pos(), ir.OCONVNOP, kt, n))
case nt.IsInteger() && kt.IsInteger():
// can directly convert (e.g. int32 to uint32)
if n.Op() == ir.OLITERAL && nt.IsSigned() {
// avoid constant overflow error
n = ir.NewConstExpr(constant.MakeUint64(uint64(ir.Int64Val(n))), n)
n.SetType(kt)
return n
}
return typecheck.Expr(ir.NewConvExpr(n.Pos(), ir.OCONV, kt, n))
default:
// Unsafe cast through memory.
// We'll need to do a load with type kt. Create a temporary of type kt to
// ensure sufficient alignment. nt may be under-aligned.
if kt.Align < nt.Align {
base.Fatalf("mapKeyTemp: key type is not sufficiently aligned, kt=%v nt=%v", kt, nt)
}
tmp := o.newTemp(kt, true)
// *(*nt)(&tmp) = n
var e ir.Node = typecheck.NodAddr(tmp)
e = ir.NewConvExpr(n.Pos(), ir.OCONVNOP, nt.PtrTo(), e)
e = ir.NewStarExpr(n.Pos(), e)
o.append(ir.NewAssignStmt(base.Pos, e, n))
return tmp
}
}
// mapKeyReplaceStrConv replaces OBYTES2STR by OBYTES2STRTMP
// in n to avoid string allocations for keys in map lookups.
// Returns a bool that signals if a modification was made.
//
// For:
// x = m[string(k)]
// x = m[T1{... Tn{..., string(k), ...}]
// where k is []byte, T1 to Tn is a nesting of struct and array literals,
// the allocation of backing bytes for the string can be avoided
// by reusing the []byte backing array. These are special cases
// for avoiding allocations when converting byte slices to strings.
// It would be nice to handle these generally, but because
// []byte keys are not allowed in maps, the use of string(k)
// comes up in important cases in practice. See issue 3512.
func mapKeyReplaceStrConv(n ir.Node) bool {
var replaced bool
switch n.Op() {
case ir.OBYTES2STR:
n := n.(*ir.ConvExpr)
n.SetOp(ir.OBYTES2STRTMP)
replaced = true
case ir.OSTRUCTLIT:
n := n.(*ir.CompLitExpr)
for _, elem := range n.List {
elem := elem.(*ir.StructKeyExpr)
if mapKeyReplaceStrConv(elem.Value) {
replaced = true
}
}
case ir.OARRAYLIT:
n := n.(*ir.CompLitExpr)
for _, elem := range n.List {
if elem.Op() == ir.OKEY {
elem = elem.(*ir.KeyExpr).Value
}
if mapKeyReplaceStrConv(elem) {
replaced = true
}
}
}
return replaced
}
type ordermarker int
// markTemp returns the top of the temporary variable stack.
func (o *orderState) markTemp() ordermarker {
return ordermarker(len(o.temp))
}
// popTemp pops temporaries off the stack until reaching the mark,
// which must have been returned by markTemp.
func (o *orderState) popTemp(mark ordermarker) {
for _, n := range o.temp[mark:] {
key := n.Type().LongString()
o.free[key] = append(o.free[key], n)
}
o.temp = o.temp[:mark]
}
// cleanTempNoPop emits VARKILL instructions to *out
// for each temporary above the mark on the temporary stack.
// It does not pop the temporaries from the stack.
func (o *orderState) cleanTempNoPop(mark ordermarker) []ir.Node {
var out []ir.Node
for i := len(o.temp) - 1; i >= int(mark); i-- {
n := o.temp[i]
out = append(out, typecheck.Stmt(ir.NewUnaryExpr(base.Pos, ir.OVARKILL, n)))
}
return out
}
// cleanTemp emits VARKILL instructions for each temporary above the
// mark on the temporary stack and removes them from the stack.
func (o *orderState) cleanTemp(top ordermarker) {
o.out = append(o.out, o.cleanTempNoPop(top)...)
o.popTemp(top)
}
// stmtList orders each of the statements in the list.
func (o *orderState) stmtList(l ir.Nodes) {
s := l
for i := range s {
orderMakeSliceCopy(s[i:])
o.stmt(s[i])
}
}
// orderMakeSliceCopy matches the pattern:
// m = OMAKESLICE([]T, x); OCOPY(m, s)
// and rewrites it to:
// m = OMAKESLICECOPY([]T, x, s); nil
func orderMakeSliceCopy(s []ir.Node) {
if base.Flag.N != 0 || base.Flag.Cfg.Instrumenting {
return
}
if len(s) < 2 || s[0] == nil || s[0].Op() != ir.OAS || s[1] == nil || s[1].Op() != ir.OCOPY {
return
}
as := s[0].(*ir.AssignStmt)
cp := s[1].(*ir.BinaryExpr)
if as.Y == nil || as.Y.Op() != ir.OMAKESLICE || ir.IsBlank(as.X) ||
as.X.Op() != ir.ONAME || cp.X.Op() != ir.ONAME || cp.Y.Op() != ir.ONAME ||
as.X.Name() != cp.X.Name() || cp.X.Name() == cp.Y.Name() {
// The line above this one is correct with the differing equality operators:
// we want as.X and cp.X to be the same name,
// but we want the initial data to be coming from a different name.
return
}
mk := as.Y.(*ir.MakeExpr)
if mk.Esc() == ir.EscNone || mk.Len == nil || mk.Cap != nil {
return
}
mk.SetOp(ir.OMAKESLICECOPY)
mk.Cap = cp.Y
// Set bounded when m = OMAKESLICE([]T, len(s)); OCOPY(m, s)
mk.SetBounded(mk.Len.Op() == ir.OLEN && ir.SameSafeExpr(mk.Len.(*ir.UnaryExpr).X, cp.Y))
as.Y = typecheck.Expr(mk)
s[1] = nil // remove separate copy call
}
// edge inserts coverage instrumentation for libfuzzer.
func (o *orderState) edge() {
if base.Debug.Libfuzzer == 0 {
return
}
// Create a new uint8 counter to be allocated in section
// __libfuzzer_extra_counters.
counter := staticinit.StaticName(types.Types[types.TUINT8])
counter.SetLibfuzzerExtraCounter(true)
// counter += 1
incr := ir.NewAssignOpStmt(base.Pos, ir.OADD, counter, ir.NewInt(1))
o.append(incr)
}
// orderBlock orders the block of statements in n into a new slice,
// and then replaces the old slice in n with the new slice.
// free is a map that can be used to obtain temporary variables by type.
func orderBlock(n *ir.Nodes, free map[string][]*ir.Name) {
var order orderState
order.free = free
mark := order.markTemp()
order.edge()
order.stmtList(*n)
order.cleanTemp(mark)
*n = order.out
}
// exprInPlace orders the side effects in *np and
// leaves them as the init list of the final *np.
// The result of exprInPlace MUST be assigned back to n, e.g.
// n.Left = o.exprInPlace(n.Left)
func (o *orderState) exprInPlace(n ir.Node) ir.Node {
var order orderState
order.free = o.free
n = order.expr(n, nil)
n = ir.InitExpr(order.out, n)
// insert new temporaries from order
// at head of outer list.
o.temp = append(o.temp, order.temp...)
return n
}
// orderStmtInPlace orders the side effects of the single statement *np
// and replaces it with the resulting statement list.
// The result of orderStmtInPlace MUST be assigned back to n, e.g.
// n.Left = orderStmtInPlace(n.Left)
// free is a map that can be used to obtain temporary variables by type.
func orderStmtInPlace(n ir.Node, free map[string][]*ir.Name) ir.Node {
var order orderState
order.free = free
mark := order.markTemp()
order.stmt(n)
order.cleanTemp(mark)
return ir.NewBlockStmt(src.NoXPos, order.out)
}
// init moves n's init list to o.out.
func (o *orderState) init(n ir.Node) {
if ir.MayBeShared(n) {
// For concurrency safety, don't mutate potentially shared nodes.
// First, ensure that no work is required here.
if len(n.Init()) > 0 {
base.Fatalf("order.init shared node with ninit")
}
return
}
o.stmtList(ir.TakeInit(n))
}
// call orders the call expression n.
// n.Op is OCALLMETH/OCALLFUNC/OCALLINTER or a builtin like OCOPY.
func (o *orderState) call(nn ir.Node) {
if len(nn.Init()) > 0 {
// Caller should have already called o.init(nn).
base.Fatalf("%v with unexpected ninit", nn.Op())
}
// Builtin functions.
if nn.Op() != ir.OCALLFUNC && nn.Op() != ir.OCALLMETH && nn.Op() != ir.OCALLINTER {
switch n := nn.(type) {
default:
base.Fatalf("unexpected call: %+v", n)
case *ir.UnaryExpr:
n.X = o.expr(n.X, nil)
case *ir.ConvExpr:
n.X = o.expr(n.X, nil)
case *ir.BinaryExpr:
n.X = o.expr(n.X, nil)
n.Y = o.expr(n.Y, nil)
case *ir.MakeExpr:
n.Len = o.expr(n.Len, nil)
n.Cap = o.expr(n.Cap, nil)
case *ir.CallExpr:
o.exprList(n.Args)
}
return
}
n := nn.(*ir.CallExpr)
typecheck.FixVariadicCall(n)
if isFuncPCIntrinsic(n) && isIfaceOfFunc(n.Args[0]) {
// For internal/abi.FuncPCABIxxx(fn), if fn is a defined function,
// do not introduce temporaries here, so it is easier to rewrite it
// to symbol address reference later in walk.
return
}
n.X = o.expr(n.X, nil)
o.exprList(n.Args)
if n.Op() == ir.OCALLINTER {
return
}
keepAlive := func(arg ir.Node) {
// If the argument is really a pointer being converted to uintptr,
// arrange for the pointer to be kept alive until the call returns,
// by copying it into a temp and marking that temp
// still alive when we pop the temp stack.
if arg.Op() == ir.OCONVNOP {
arg := arg.(*ir.ConvExpr)
if arg.X.Type().IsUnsafePtr() {
x := o.copyExpr(arg.X)
arg.X = x
x.SetAddrtaken(true) // ensure SSA keeps the x variable
n.KeepAlive = append(n.KeepAlive, x)
}
}
}
// Check for "unsafe-uintptr" tag provided by escape analysis.
for i, param := range n.X.Type().Params().FieldSlice() {
if param.Note == escape.UnsafeUintptrNote || param.Note == escape.UintptrEscapesNote {
if arg := n.Args[i]; arg.Op() == ir.OSLICELIT {
arg := arg.(*ir.CompLitExpr)
for _, elt := range arg.List {
keepAlive(elt)
}
} else {
keepAlive(arg)
}
}
}
}
// mapAssign appends n to o.out.
func (o *orderState) mapAssign(n ir.Node) {
switch n.Op() {
default:
base.Fatalf("order.mapAssign %v", n.Op())
case ir.OAS:
n := n.(*ir.AssignStmt)
if n.X.Op() == ir.OINDEXMAP {
n.Y = o.safeMapRHS(n.Y)
}
o.out = append(o.out, n)
case ir.OASOP:
n := n.(*ir.AssignOpStmt)
if n.X.Op() == ir.OINDEXMAP {
n.Y = o.safeMapRHS(n.Y)
}
o.out = append(o.out, n)
}
}
func (o *orderState) safeMapRHS(r ir.Node) ir.Node {
// Make sure we evaluate the RHS before starting the map insert.
// We need to make sure the RHS won't panic. See issue 22881.
if r.Op() == ir.OAPPEND {
r := r.(*ir.CallExpr)
s := r.Args[1:]
for i, n := range s {
s[i] = o.cheapExpr(n)
}
return r
}
return o.cheapExpr(r)
}
// stmt orders the statement n, appending to o.out.
// Temporaries created during the statement are cleaned
// up using VARKILL instructions as possible.
func (o *orderState) stmt(n ir.Node) {
if n == nil {
return
}
lno := ir.SetPos(n)
o.init(n)
switch n.Op() {
default:
base.Fatalf("order.stmt %v", n.Op())
case ir.OVARKILL, ir.OVARLIVE, ir.OINLMARK:
o.out = append(o.out, n)
case ir.OAS:
n := n.(*ir.AssignStmt)
t := o.markTemp()
n.X = o.expr(n.X, nil)
n.Y = o.expr(n.Y, n.X)
o.mapAssign(n)
o.cleanTemp(t)
case ir.OASOP:
n := n.(*ir.AssignOpStmt)
t := o.markTemp()
n.X = o.expr(n.X, nil)
n.Y = o.expr(n.Y, nil)
if base.Flag.Cfg.Instrumenting || n.X.Op() == ir.OINDEXMAP && (n.AsOp == ir.ODIV || n.AsOp == ir.OMOD) {
// Rewrite m[k] op= r into m[k] = m[k] op r so
// that we can ensure that if op panics
// because r is zero, the panic happens before
// the map assignment.
// DeepCopy is a big hammer here, but safeExpr
// makes sure there is nothing too deep being copied.
l1 := o.safeExpr(n.X)
l2 := ir.DeepCopy(src.NoXPos, l1)
if l2.Op() == ir.OINDEXMAP {
l2 := l2.(*ir.IndexExpr)
l2.Assigned = false
}
l2 = o.copyExpr(l2)
r := o.expr(typecheck.Expr(ir.NewBinaryExpr(n.Pos(), n.AsOp, l2, n.Y)), nil)
as := typecheck.Stmt(ir.NewAssignStmt(n.Pos(), l1, r))
o.mapAssign(as)
o.cleanTemp(t)
return
}
o.mapAssign(n)
o.cleanTemp(t)
case ir.OAS2:
n := n.(*ir.AssignListStmt)
t := o.markTemp()
o.exprList(n.Lhs)
o.exprList(n.Rhs)
o.out = append(o.out, n)
o.cleanTemp(t)
// Special: avoid copy of func call n.Right
case ir.OAS2FUNC:
n := n.(*ir.AssignListStmt)
t := o.markTemp()
o.exprList(n.Lhs)
o.init(n.Rhs[0])
o.call(n.Rhs[0])
o.as2func(n)
o.cleanTemp(t)
// Special: use temporary variables to hold result,
// so that runtime can take address of temporary.
// No temporary for blank assignment.
//
// OAS2MAPR: make sure key is addressable if needed,
// and make sure OINDEXMAP is not copied out.
case ir.OAS2DOTTYPE, ir.OAS2RECV, ir.OAS2MAPR:
n := n.(*ir.AssignListStmt)
t := o.markTemp()
o.exprList(n.Lhs)
switch r := n.Rhs[0]; r.Op() {
case ir.ODOTTYPE2:
r := r.(*ir.TypeAssertExpr)
r.X = o.expr(r.X, nil)
case ir.ORECV:
r := r.(*ir.UnaryExpr)
r.X = o.expr(r.X, nil)
case ir.OINDEXMAP:
r := r.(*ir.IndexExpr)
r.X = o.expr(r.X, nil)
r.Index = o.expr(r.Index, nil)
// See similar conversion for OINDEXMAP below.
_ = mapKeyReplaceStrConv(r.Index)
r.Index = o.mapKeyTemp(r.X.Type(), r.Index)
default:
base.Fatalf("order.stmt: %v", r.Op())
}
o.as2ok(n)
o.cleanTemp(t)
// Special: does not save n onto out.
case ir.OBLOCK:
n := n.(*ir.BlockStmt)
o.stmtList(n.List)
// Special: n->left is not an expression; save as is.
case ir.OBREAK,
ir.OCONTINUE,
ir.ODCL,
ir.ODCLCONST,
ir.ODCLTYPE,
ir.OFALL,
ir.OGOTO,
ir.OLABEL,
ir.OTAILCALL:
o.out = append(o.out, n)
// Special: handle call arguments.
case ir.OCALLFUNC, ir.OCALLINTER, ir.OCALLMETH:
n := n.(*ir.CallExpr)
t := o.markTemp()
o.call(n)
o.out = append(o.out, n)
o.cleanTemp(t)
case ir.OCLOSE, ir.ORECV:
n := n.(*ir.UnaryExpr)
t := o.markTemp()
n.X = o.expr(n.X, nil)
o.out = append(o.out, n)
o.cleanTemp(t)
case ir.OCOPY:
n := n.(*ir.BinaryExpr)
t := o.markTemp()
n.X = o.expr(n.X, nil)
n.Y = o.expr(n.Y, nil)
o.out = append(o.out, n)
o.cleanTemp(t)
case ir.OPRINT, ir.OPRINTN, ir.ORECOVER:
n := n.(*ir.CallExpr)
t := o.markTemp()
o.exprList(n.Args)
o.out = append(o.out, n)
o.cleanTemp(t)
// Special: order arguments to inner call but not call itself.
case ir.ODEFER, ir.OGO:
n := n.(*ir.GoDeferStmt)
t := o.markTemp()
o.init(n.Call)
o.call(n.Call)
if n.Call.Op() == ir.ORECOVER {
// Special handling of "defer recover()". We need to evaluate the FP
// argument before wrapping.
var init ir.Nodes
n.Call = walkRecover(n.Call.(*ir.CallExpr), &init)
o.stmtList(init)
}
if buildcfg.Experiment.RegabiDefer {
o.wrapGoDefer(n)
}
o.out = append(o.out, n)
o.cleanTemp(t)
case ir.ODELETE:
n := n.(*ir.CallExpr)
t := o.markTemp()
n.Args[0] = o.expr(n.Args[0], nil)
n.Args[1] = o.expr(n.Args[1], nil)
n.Args[1] = o.mapKeyTemp(n.Args[0].Type(), n.Args[1])
o.out = append(o.out, n)
o.cleanTemp(t)
// Clean temporaries from condition evaluation at
// beginning of loop body and after for statement.
case ir.OFOR:
n := n.(*ir.ForStmt)
t := o.markTemp()
n.Cond = o.exprInPlace(n.Cond)
n.Body.Prepend(o.cleanTempNoPop(t)...)
orderBlock(&n.Body, o.free)
n.Post = orderStmtInPlace(n.Post, o.free)
o.out = append(o.out, n)
o.cleanTemp(t)
// Clean temporaries from condition at
// beginning of both branches.
case ir.OIF:
n := n.(*ir.IfStmt)
t := o.markTemp()
n.Cond = o.exprInPlace(n.Cond)
n.Body.Prepend(o.cleanTempNoPop(t)...)
n.Else.Prepend(o.cleanTempNoPop(t)...)
o.popTemp(t)
orderBlock(&n.Body, o.free)
orderBlock(&n.Else, o.free)
o.out = append(o.out, n)
case ir.OPANIC:
n := n.(*ir.UnaryExpr)
t := o.markTemp()
n.X = o.expr(n.X, nil)
if !n.X.Type().IsEmptyInterface() {
base.FatalfAt(n.Pos(), "bad argument to panic: %L", n.X)
}
o.out = append(o.out, n)
o.cleanTemp(t)
case ir.ORANGE:
// n.Right is the expression being ranged over.
// order it, and then make a copy if we need one.
// We almost always do, to ensure that we don't
// see any value changes made during the loop.
// Usually the copy is cheap (e.g., array pointer,
// chan, slice, string are all tiny).
// The exception is ranging over an array value
// (not a slice, not a pointer to array),
// which must make a copy to avoid seeing updates made during
// the range body. Ranging over an array value is uncommon though.
// Mark []byte(str) range expression to reuse string backing storage.
// It is safe because the storage cannot be mutated.
n := n.(*ir.RangeStmt)
if n.X.Op() == ir.OSTR2BYTES {
n.X.(*ir.ConvExpr).SetOp(ir.OSTR2BYTESTMP)
}
t := o.markTemp()
n.X = o.expr(n.X, nil)
orderBody := true
xt := typecheck.RangeExprType(n.X.Type())
switch xt.Kind() {
default:
base.Fatalf("order.stmt range %v", n.Type())
case types.TARRAY, types.TSLICE:
if n.Value == nil || ir.IsBlank(n.Value) {
// for i := range x will only use x once, to compute len(x).
// No need to copy it.
break
}
fallthrough
case types.TCHAN, types.TSTRING:
// chan, string, slice, array ranges use value multiple times.
// make copy.
r := n.X
if r.Type().IsString() && r.Type() != types.Types[types.TSTRING] {
r = ir.NewConvExpr(base.Pos, ir.OCONV, nil, r)
r.SetType(types.Types[types.TSTRING])
r = typecheck.Expr(r)
}
n.X = o.copyExpr(r)
case types.TMAP:
if isMapClear(n) {
// Preserve the body of the map clear pattern so it can
// be detected during walk. The loop body will not be used
// when optimizing away the range loop to a runtime call.
orderBody = false
break
}
// copy the map value in case it is a map literal.
// TODO(rsc): Make tmp = literal expressions reuse tmp.
// For maps tmp is just one word so it hardly matters.
r := n.X
n.X = o.copyExpr(r)
// n.Prealloc is the temp for the iterator.
// MapIterType contains pointers and needs to be zeroed.
n.Prealloc = o.newTemp(reflectdata.MapIterType(xt), true)
}
n.Key = o.exprInPlace(n.Key)
n.Value = o.exprInPlace(n.Value)
if orderBody {
orderBlock(&n.Body, o.free)
}
o.out = append(o.out, n)
o.cleanTemp(t)
case ir.ORETURN:
n := n.(*ir.ReturnStmt)
o.exprList(n.Results)
o.out = append(o.out, n)
// Special: clean case temporaries in each block entry.
// Select must enter one of its blocks, so there is no
// need for a cleaning at the end.
// Doubly special: evaluation order for select is stricter
// than ordinary expressions. Even something like p.c
// has to be hoisted into a temporary, so that it cannot be
// reordered after the channel evaluation for a different
// case (if p were nil, then the timing of the fault would
// give this away).
case ir.OSELECT:
n := n.(*ir.SelectStmt)
t := o.markTemp()
for _, ncas := range n.Cases {
r := ncas.Comm
ir.SetPos(ncas)
// Append any new body prologue to ninit.
// The next loop will insert ninit into nbody.
if len(ncas.Init()) != 0 {
base.Fatalf("order select ninit")
}
if r == nil {
continue
}
switch r.Op() {
default:
ir.Dump("select case", r)
base.Fatalf("unknown op in select %v", r.Op())
case ir.OSELRECV2:
// case x, ok = <-c
r := r.(*ir.AssignListStmt)
recv := r.Rhs[0].(*ir.UnaryExpr)
recv.X = o.expr(recv.X, nil)
if !ir.IsAutoTmp(recv.X) {
recv.X = o.copyExpr(recv.X)
}
init := ir.TakeInit(r)
colas := r.Def
do := func(i int, t *types.Type) {
n := r.Lhs[i]
if ir.IsBlank(n) {
return
}
// If this is case x := <-ch or case x, y := <-ch, the case has
// the ODCL nodes to declare x and y. We want to delay that
// declaration (and possible allocation) until inside the case body.
// Delete the ODCL nodes here and recreate them inside the body below.
if colas {
if len(init) > 0 && init[0].Op() == ir.ODCL && init[0].(*ir.Decl).X == n {
init = init[1:]
}
dcl := typecheck.Stmt(ir.NewDecl(base.Pos, ir.ODCL, n.(*ir.Name)))
ncas.PtrInit().Append(dcl)
}
tmp := o.newTemp(t, t.HasPointers())
as := typecheck.Stmt(ir.NewAssignStmt(base.Pos, n, typecheck.Conv(tmp, n.Type())))
ncas.PtrInit().Append(as)
r.Lhs[i] = tmp
}
do(0, recv.X.Type().Elem())
do(1, types.Types[types.TBOOL])
if len(init) != 0 {
ir.DumpList("ninit", r.Init())
base.Fatalf("ninit on select recv")
}
orderBlock(ncas.PtrInit(), o.free)
case ir.OSEND:
r := r.(*ir.SendStmt)
if len(r.Init()) != 0 {
ir.DumpList("ninit", r.Init())
base.Fatalf("ninit on select send")
}
// case c <- x
// r->left is c, r->right is x, both are always evaluated.
r.Chan = o.expr(r.Chan, nil)
if !ir.IsAutoTmp(r.Chan) {
r.Chan = o.copyExpr(r.Chan)
}
r.Value = o.expr(r.Value, nil)
if !ir.IsAutoTmp(r.Value) {
r.Value = o.copyExpr(r.Value)
}
}
}
// Now that we have accumulated all the temporaries, clean them.
// Also insert any ninit queued during the previous loop.
// (The temporary cleaning must follow that ninit work.)
for _, cas := range n.Cases {
orderBlock(&cas.Body, o.free)
cas.Body.Prepend(o.cleanTempNoPop(t)...)
// TODO(mdempsky): Is this actually necessary?
// walkSelect appears to walk Ninit.
cas.Body.Prepend(ir.TakeInit(cas)...)
}
o.out = append(o.out, n)
o.popTemp(t)
// Special: value being sent is passed as a pointer; make it addressable.
case ir.OSEND:
n := n.(*ir.SendStmt)
t := o.markTemp()
n.Chan = o.expr(n.Chan, nil)
n.Value = o.expr(n.Value, nil)
if base.Flag.Cfg.Instrumenting {
// Force copying to the stack so that (chan T)(nil) <- x
// is still instrumented as a read of x.
n.Value = o.copyExpr(n.Value)
} else {
n.Value = o.addrTemp(n.Value)
}
o.out = append(o.out, n)
o.cleanTemp(t)
// TODO(rsc): Clean temporaries more aggressively.
// Note that because walkSwitch will rewrite some of the
// switch into a binary search, this is not as easy as it looks.
// (If we ran that code here we could invoke order.stmt on
// the if-else chain instead.)
// For now just clean all the temporaries at the end.
// In practice that's fine.
case ir.OSWITCH:
n := n.(*ir.SwitchStmt)
if base.Debug.Libfuzzer != 0 && !hasDefaultCase(n) {
// Add empty "default:" case for instrumentation.
n.Cases = append(n.Cases, ir.NewCaseStmt(base.Pos, nil, nil))
}
t := o.markTemp()
n.Tag = o.expr(n.Tag, nil)
for _, ncas := range n.Cases {
o.exprListInPlace(ncas.List)
orderBlock(&ncas.Body, o.free)
}
o.out = append(o.out, n)
o.cleanTemp(t)
}
base.Pos = lno
}
func hasDefaultCase(n *ir.SwitchStmt) bool {
for _, ncas := range n.Cases {
if len(ncas.List) == 0 {
return true
}
}
return false
}
// exprList orders the expression list l into o.
func (o *orderState) exprList(l ir.Nodes) {
s := l
for i := range s {
s[i] = o.expr(s[i], nil)
}
}
// exprListInPlace orders the expression list l but saves
// the side effects on the individual expression ninit lists.
func (o *orderState) exprListInPlace(l ir.Nodes) {
s := l
for i := range s {
s[i] = o.exprInPlace(s[i])
}
}
func (o *orderState) exprNoLHS(n ir.Node) ir.Node {
return o.expr(n, nil)
}
// expr orders a single expression, appending side
// effects to o.out as needed.
// If this is part of an assignment lhs = *np, lhs is given.
// Otherwise lhs == nil. (When lhs != nil it may be possible
// to avoid copying the result of the expression to a temporary.)
// The result of expr MUST be assigned back to n, e.g.
// n.Left = o.expr(n.Left, lhs)
func (o *orderState) expr(n, lhs ir.Node) ir.Node {
if n == nil {
return n
}
lno := ir.SetPos(n)
n = o.expr1(n, lhs)
base.Pos = lno
return n
}
func (o *orderState) expr1(n, lhs ir.Node) ir.Node {
o.init(n)
switch n.Op() {
default:
if o.edit == nil {
o.edit = o.exprNoLHS // create closure once
}
ir.EditChildren(n, o.edit)
return n
// Addition of strings turns into a function call.
// Allocate a temporary to hold the strings.
// Fewer than 5 strings use direct runtime helpers.
case ir.OADDSTR:
n := n.(*ir.AddStringExpr)
o.exprList(n.List)
if len(n.List) > 5 {
t := types.NewArray(types.Types[types.TSTRING], int64(len(n.List)))
n.Prealloc = o.newTemp(t, false)
}
// Mark string(byteSlice) arguments to reuse byteSlice backing
// buffer during conversion. String concatenation does not
// memorize the strings for later use, so it is safe.
// However, we can do it only if there is at least one non-empty string literal.
// Otherwise if all other arguments are empty strings,
// concatstrings will return the reference to the temp string
// to the caller.
hasbyte := false
haslit := false
for _, n1 := range n.List {
hasbyte = hasbyte || n1.Op() == ir.OBYTES2STR
haslit = haslit || n1.Op() == ir.OLITERAL && len(ir.StringVal(n1)) != 0
}
if haslit && hasbyte {
for _, n2 := range n.List {
if n2.Op() == ir.OBYTES2STR {
n2 := n2.(*ir.ConvExpr)
n2.SetOp(ir.OBYTES2STRTMP)
}
}
}
return n
case ir.OINDEXMAP:
n := n.(*ir.IndexExpr)
n.X = o.expr(n.X, nil)
n.Index = o.expr(n.Index, nil)
needCopy := false
if !n.Assigned {
// Enforce that any []byte slices we are not copying
// can not be changed before the map index by forcing
// the map index to happen immediately following the
// conversions. See copyExpr a few lines below.
needCopy = mapKeyReplaceStrConv(n.Index)
if base.Flag.Cfg.Instrumenting {
// Race detector needs the copy.
needCopy = true
}
}
// key must be addressable
n.Index = o.mapKeyTemp(n.X.Type(), n.Index)
if needCopy {
return o.copyExpr(n)
}
return n
// concrete type (not interface) argument might need an addressable
// temporary to pass to the runtime conversion routine.
case ir.OCONVIFACE:
n := n.(*ir.ConvExpr)
n.X = o.expr(n.X, nil)
if n.X.Type().IsInterface() {
return n
}
if _, _, needsaddr := convFuncName(n.X.Type(), n.Type()); needsaddr || isStaticCompositeLiteral(n.X) {
// Need a temp if we need to pass the address to the conversion function.
// We also process static composite literal node here, making a named static global
// whose address we can put directly in an interface (see OCONVIFACE case in walk).
n.X = o.addrTemp(n.X)
}
return n
case ir.OCONVNOP:
n := n.(*ir.ConvExpr)
if n.Type().IsKind(types.TUNSAFEPTR) && n.X.Type().IsKind(types.TUINTPTR) && (n.X.Op() == ir.OCALLFUNC || n.X.Op() == ir.OCALLINTER || n.X.Op() == ir.OCALLMETH) {
call := n.X.(*ir.CallExpr)
// When reordering unsafe.Pointer(f()) into a separate
// statement, the conversion and function call must stay
// together. See golang.org/issue/15329.
o.init(call)
o.call(call)
if lhs == nil || lhs.Op() != ir.ONAME || base.Flag.Cfg.Instrumenting {
return o.copyExpr(n)
}
} else {
n.X = o.expr(n.X, nil)
}
return n
case ir.OANDAND, ir.OOROR:
// ... = LHS && RHS
//
// var r bool
// r = LHS
// if r { // or !r, for OROR
// r = RHS
// }
// ... = r
n := n.(*ir.LogicalExpr)
r := o.newTemp(n.Type(), false)
// Evaluate left-hand side.
lhs := o.expr(n.X, nil)
o.out = append(o.out, typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, lhs)))
// Evaluate right-hand side, save generated code.
saveout := o.out
o.out = nil
t := o.markTemp()
o.edge()
rhs := o.expr(n.Y, nil)
o.out = append(o.out, typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, rhs)))
o.cleanTemp(t)
gen := o.out
o.out = saveout
// If left-hand side doesn't cause a short-circuit, issue right-hand side.
nif := ir.NewIfStmt(base.Pos, r, nil, nil)
if n.Op() == ir.OANDAND {
nif.Body = gen
} else {
nif.Else = gen
}
o.out = append(o.out, nif)
return r
case ir.OCALLFUNC,
ir.OCALLINTER,
ir.OCALLMETH,
ir.OCAP,
ir.OCOMPLEX,
ir.OCOPY,
ir.OIMAG,
ir.OLEN,
ir.OMAKECHAN,
ir.OMAKEMAP,
ir.OMAKESLICE,
ir.OMAKESLICECOPY,
ir.ONEW,
ir.OREAL,
ir.ORECOVER,
ir.OSTR2BYTES,
ir.OSTR2BYTESTMP,
ir.OSTR2RUNES:
if isRuneCount(n) {
// len([]rune(s)) is rewritten to runtime.countrunes(s) later.
conv := n.(*ir.UnaryExpr).X.(*ir.ConvExpr)
conv.X = o.expr(conv.X, nil)
} else {
o.call(n)
}
if lhs == nil || lhs.Op() != ir.ONAME || base.Flag.Cfg.Instrumenting {
return o.copyExpr(n)
}
return n
case ir.OAPPEND:
// Check for append(x, make([]T, y)...) .
n := n.(*ir.CallExpr)
if isAppendOfMake(n) {
n.Args[0] = o.expr(n.Args[0], nil) // order x
mk := n.Args[1].(*ir.MakeExpr)
mk.Len = o.expr(mk.Len, nil) // order y
} else {
o.exprList(n.Args)
}
if lhs == nil || lhs.Op() != ir.ONAME && !ir.SameSafeExpr(lhs, n.Args[0]) {
return o.copyExpr(n)
}
return n
case ir.OSLICE, ir.OSLICEARR, ir.OSLICESTR, ir.OSLICE3, ir.OSLICE3ARR:
n := n.(*ir.SliceExpr)
n.X = o.expr(n.X, nil)
n.Low = o.cheapExpr(o.expr(n.Low, nil))
n.High = o.cheapExpr(o.expr(n.High, nil))
n.Max = o.cheapExpr(o.expr(n.Max, nil))
if lhs == nil || lhs.Op() != ir.ONAME && !ir.SameSafeExpr(lhs, n.X) {
return o.copyExpr(n)
}
return n
case ir.OCLOSURE:
n := n.(*ir.ClosureExpr)
if n.Transient() && len(n.Func.ClosureVars) > 0 {
n.Prealloc = o.newTemp(typecheck.ClosureType(n), false)
}
return n
case ir.OCALLPART:
n := n.(*ir.SelectorExpr)
n.X = o.expr(n.X, nil)
if n.Transient() {
t := typecheck.PartialCallType(n)
n.Prealloc = o.newTemp(t, false)
}
return n
case ir.OSLICELIT:
n := n.(*ir.CompLitExpr)
o.exprList(n.List)
if n.Transient() {
t := types.NewArray(n.Type().Elem(), n.Len)
n.Prealloc = o.newTemp(t, false)
}
return n
case ir.ODOTTYPE, ir.ODOTTYPE2:
n := n.(*ir.TypeAssertExpr)
n.X = o.expr(n.X, nil)
if !types.IsDirectIface(n.Type()) || base.Flag.Cfg.Instrumenting {
return o.copyExprClear(n)
}
return n
case ir.ORECV:
n := n.(*ir.UnaryExpr)
n.X = o.expr(n.X, nil)
return o.copyExprClear(n)
case ir.OEQ, ir.ONE, ir.OLT, ir.OLE, ir.OGT, ir.OGE:
n := n.(*ir.BinaryExpr)
n.X = o.expr(n.X, nil)
n.Y = o.expr(n.Y, nil)
t := n.X.Type()
switch {
case t.IsString():
// Mark string(byteSlice) arguments to reuse byteSlice backing
// buffer during conversion. String comparison does not
// memorize the strings for later use, so it is safe.
if n.X.Op() == ir.OBYTES2STR {
n.X.(*ir.ConvExpr).SetOp(ir.OBYTES2STRTMP)
}
if n.Y.Op() == ir.OBYTES2STR {
n.Y.(*ir.ConvExpr).SetOp(ir.OBYTES2STRTMP)
}
case t.IsStruct() || t.IsArray():
// for complex comparisons, we need both args to be
// addressable so we can pass them to the runtime.
n.X = o.addrTemp(n.X)
n.Y = o.addrTemp(n.Y)
}
return n
case ir.OMAPLIT:
// Order map by converting:
// map[int]int{
// a(): b(),
// c(): d(),
// e(): f(),
// }
// to
// m := map[int]int{}
// m[a()] = b()
// m[c()] = d()
// m[e()] = f()
// Then order the result.
// Without this special case, order would otherwise compute all
// the keys and values before storing any of them to the map.
// See issue 26552.
n := n.(*ir.CompLitExpr)
entries := n.List
statics := entries[:0]
var dynamics []*ir.KeyExpr
for _, r := range entries {
r := r.(*ir.KeyExpr)
if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
dynamics = append(dynamics, r)
continue
}
// Recursively ordering some static entries can change them to dynamic;
// e.g., OCONVIFACE nodes. See #31777.
r = o.expr(r, nil).(*ir.KeyExpr)
if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
dynamics = append(dynamics, r)
continue
}
statics = append(statics, r)
}
n.List = statics
if len(dynamics) == 0 {
return n
}
// Emit the creation of the map (with all its static entries).
m := o.newTemp(n.Type(), false)
as := ir.NewAssignStmt(base.Pos, m, n)
typecheck.Stmt(as)
o.stmt(as)
// Emit eval+insert of dynamic entries, one at a time.
for _, r := range dynamics {
as := ir.NewAssignStmt(base.Pos, ir.NewIndexExpr(base.Pos, m, r.Key), r.Value)
typecheck.Stmt(as) // Note: this converts the OINDEX to an OINDEXMAP
o.stmt(as)
}
return m
}
// No return - type-assertions above. Each case must return for itself.
}
// as2func orders OAS2FUNC nodes. It creates temporaries to ensure left-to-right assignment.
// The caller should order the right-hand side of the assignment before calling order.as2func.
// It rewrites,
// a, b, a = ...
// as
// tmp1, tmp2, tmp3 = ...
// a, b, a = tmp1, tmp2, tmp3
// This is necessary to ensure left to right assignment order.
func (o *orderState) as2func(n *ir.AssignListStmt) {
results := n.Rhs[0].Type()
as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
for i, nl := range n.Lhs {
if !ir.IsBlank(nl) {
typ := results.Field(i).Type
tmp := o.newTemp(typ, typ.HasPointers())
n.Lhs[i] = tmp
as.Lhs = append(as.Lhs, nl)
as.Rhs = append(as.Rhs, tmp)
}
}
o.out = append(o.out, n)
o.stmt(typecheck.Stmt(as))
}
// as2ok orders OAS2XXX with ok.
// Just like as2func, this also adds temporaries to ensure left-to-right assignment.
func (o *orderState) as2ok(n *ir.AssignListStmt) {
as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
do := func(i int, typ *types.Type) {
if nl := n.Lhs[i]; !ir.IsBlank(nl) {
var tmp ir.Node = o.newTemp(typ, typ.HasPointers())
n.Lhs[i] = tmp
as.Lhs = append(as.Lhs, nl)
if i == 1 {
// The "ok" result is an untyped boolean according to the Go
// spec. We need to explicitly convert it to the LHS type in
// case the latter is a defined boolean type (#8475).
tmp = typecheck.Conv(tmp, nl.Type())
}
as.Rhs = append(as.Rhs, tmp)
}
}
do(0, n.Rhs[0].Type())
do(1, types.Types[types.TBOOL])
o.out = append(o.out, n)
o.stmt(typecheck.Stmt(as))
}
var wrapGoDefer_prgen int
// wrapGoDefer wraps the target of a "go" or "defer" statement with a
// new "function with no arguments" closure. Specifically, it converts
//
// defer f(x, y)
//
// to
//
// x1, y1 := x, y
// defer func() { f(x1, y1) }()
//
// This is primarily to enable a quicker bringup of defers under the
// new register ABI; by doing this conversion, we can simplify the
// code in the runtime that invokes defers on the panic path.
func (o *orderState) wrapGoDefer(n *ir.GoDeferStmt) {
call := n.Call
var callX ir.Node // thing being called
var callArgs []ir.Node // call arguments
var keepAlive []*ir.Name // KeepAlive list from call, if present
// A helper to recreate the call within the closure.
var mkNewCall func(pos src.XPos, op ir.Op, fun ir.Node, args []ir.Node) ir.Node
// Defer calls come in many shapes and sizes; not all of them
// are ir.CallExpr's. Examine the type to see what we're dealing with.
switch x := call.(type) {
case *ir.CallExpr:
callX = x.X
callArgs = x.Args
keepAlive = x.KeepAlive
mkNewCall = func(pos src.XPos, op ir.Op, fun ir.Node, args []ir.Node) ir.Node {
newcall := ir.NewCallExpr(pos, op, fun, args)
newcall.IsDDD = x.IsDDD
return ir.Node(newcall)
}
case *ir.UnaryExpr: // ex: OCLOSE
callArgs = []ir.Node{x.X}
mkNewCall = func(pos src.XPos, op ir.Op, fun ir.Node, args []ir.Node) ir.Node {
if len(args) != 1 {
panic("internal error, expecting single arg")
}
return ir.Node(ir.NewUnaryExpr(pos, op, args[0]))
}
case *ir.BinaryExpr: // ex: OCOPY
callArgs = []ir.Node{x.X, x.Y}
mkNewCall = func(pos src.XPos, op ir.Op, fun ir.Node, args []ir.Node) ir.Node {
if len(args) != 2 {
panic("internal error, expecting two args")
}
return ir.Node(ir.NewBinaryExpr(pos, op, args[0], args[1]))
}
default:
panic("unhandled op")
}
// No need to wrap if called func has no args, no receiver, and no results.
// However in the case of "defer func() { ... }()" we need to
// protect against the possibility of directClosureCall rewriting
// things so that the call does have arguments.
//
// Do wrap method calls (OCALLMETH, OCALLINTER), because it has
// a receiver.
//
// Also do wrap builtin functions, because they may be expanded to
// calls with arguments (e.g. ORECOVER).
//
// TODO: maybe not wrap if the called function has no arguments and
// only in-register results?
if len(callArgs) == 0 && call.Op() == ir.OCALLFUNC && callX.Type().NumResults() == 0 {
if c, ok := call.(*ir.CallExpr); ok && callX != nil && callX.Op() == ir.OCLOSURE {
cloFunc := callX.(*ir.ClosureExpr).Func
cloFunc.SetClosureCalled(false)
c.PreserveClosure = true
}
return
}
if c, ok := call.(*ir.CallExpr); ok {
// To simplify things, turn f(a, b, []T{c, d, e}...) back
// into f(a, b, c, d, e) -- when the final call is run through the
// type checker below, it will rebuild the proper slice literal.
undoVariadic(c)
callX = c.X
callArgs = c.Args
}
// This is set to true if the closure we're generating escapes
// (needs heap allocation).
cloEscapes := func() bool {
if n.Op() == ir.OGO {
// For "go", assume that all closures escape.
return true
}
// For defer, just use whatever result escape analysis
// has determined for the defer.
return n.Esc() != ir.EscNever
}()
// A helper for making a copy of an argument. Note that it is
// not safe to use o.copyExpr(arg) if we're putting a
// reference to the temp into the closure (as opposed to
// copying it in by value), since in the by-reference case we
// need a temporary whose lifetime extends to the end of the
// function (as opposed to being local to the current block or
// statement being ordered).
mkArgCopy := func(arg ir.Node) *ir.Name {
t := arg.Type()
byval := t.Size() <= 128 || cloEscapes
var argCopy *ir.Name
if byval {
argCopy = o.copyExpr(arg)
} else {
argCopy = typecheck.Temp(t)
o.append(ir.NewAssignStmt(base.Pos, argCopy, arg))
}
// The value of 128 below is meant to be consistent with code
// in escape analysis that picks byval/byaddr based on size.
argCopy.SetByval(byval)
return argCopy
}
// getUnsafeArg looks for an unsafe.Pointer arg that has been
// previously captured into the call's keepalive list, returning
// the name node for it if found.
getUnsafeArg := func(arg ir.Node) *ir.Name {
// Look for uintptr(unsafe.Pointer(name))
if arg.Op() != ir.OCONVNOP {
return nil
}
if !arg.Type().IsUintptr() {
return nil
}
if !arg.(*ir.ConvExpr).X.Type().IsUnsafePtr() {
return nil
}
arg = arg.(*ir.ConvExpr).X
argname, ok := arg.(*ir.Name)
if !ok {
return nil
}
for i := range keepAlive {
if argname == keepAlive[i] {
return argname
}
}
return nil
}
// Copy the arguments to the function into temps.
//
// For calls with uintptr(unsafe.Pointer(...)) args that are being
// kept alive (see code in (*orderState).call that does this), use
// the existing arg copy instead of creating a new copy.
unsafeArgs := make([]*ir.Name, len(callArgs))
origArgs := callArgs
var newNames []*ir.Name
for i := range callArgs {
arg := callArgs[i]
var argname *ir.Name
unsafeArgName := getUnsafeArg(arg)
if unsafeArgName != nil {
// arg has been copied already, use keepalive copy
argname = unsafeArgName
unsafeArgs[i] = unsafeArgName
} else {
argname = mkArgCopy(arg)
}
newNames = append(newNames, argname)
}
// Deal with cases where the function expression (what we're
// calling) is not a simple function symbol.
var fnExpr *ir.Name
var methSelectorExpr *ir.SelectorExpr
if callX != nil {
switch {
case callX.Op() == ir.ODOTMETH || callX.Op() == ir.ODOTINTER:
// Handle defer of a method call, e.g. "defer v.MyMethod(x, y)"
n := callX.(*ir.SelectorExpr)
n.X = mkArgCopy(n.X)
methSelectorExpr = n
if callX.Op() == ir.ODOTINTER {
// Currently for "defer i.M()" if i is nil it panics at the
// point of defer statement, not when deferred function is called.
// (I think there is an issue discussing what is the intended
// behavior but I cannot find it.)
// We need to do the nil check outside of the wrapper.
tab := typecheck.Expr(ir.NewUnaryExpr(base.Pos, ir.OITAB, n.X))
c := ir.NewUnaryExpr(n.Pos(), ir.OCHECKNIL, tab)
c.SetTypecheck(1)
o.append(c)
}
case !(callX.Op() == ir.ONAME && callX.(*ir.Name).Class == ir.PFUNC):
// Deal with "defer returnsafunc()(x, y)" (for
// example) by copying the callee expression.
fnExpr = mkArgCopy(callX)
if callX.Op() == ir.OCLOSURE {
// For "defer func(...)", in addition to copying the
// closure into a temp, mark it as no longer directly
// called.
callX.(*ir.ClosureExpr).Func.SetClosureCalled(false)
}
}
}
// Create a new no-argument function that we'll hand off to defer.
var noFuncArgs []*ir.Field
noargst := ir.NewFuncType(base.Pos, nil, noFuncArgs, nil)
wrapGoDefer_prgen++
outerfn := ir.CurFunc
wrapname := fmt.Sprintf("%v·dwrap·%d", outerfn, wrapGoDefer_prgen)
sym := types.LocalPkg.Lookup(wrapname)
fn := typecheck.DeclFunc(sym, noargst)
fn.SetIsHiddenClosure(true)
fn.SetWrapper(true)
// helper for capturing reference to a var declared in an outer scope.
capName := func(pos src.XPos, fn *ir.Func, n *ir.Name) *ir.Name {
t := n.Type()
cv := ir.CaptureName(pos, fn, n)
cv.SetType(t)
return typecheck.Expr(cv).(*ir.Name)
}
// Call args (x1, y1) need to be captured as part of the newly
// created closure.
newCallArgs := []ir.Node{}
for i := range newNames {
var arg ir.Node
arg = capName(callArgs[i].Pos(), fn, newNames[i])
if unsafeArgs[i] != nil {
arg = ir.NewConvExpr(arg.Pos(), origArgs[i].Op(), origArgs[i].Type(), arg)
}
newCallArgs = append(newCallArgs, arg)
}
// Also capture the function or method expression (if needed) into
// the closure.
if fnExpr != nil {
callX = capName(callX.Pos(), fn, fnExpr)
}
if methSelectorExpr != nil {
methSelectorExpr.X = capName(callX.Pos(), fn, methSelectorExpr.X.(*ir.Name))
}
ir.FinishCaptureNames(n.Pos(), outerfn, fn)
// This flags a builtin as opposed to a regular call.
irregular := (call.Op() != ir.OCALLFUNC &&
call.Op() != ir.OCALLMETH &&
call.Op() != ir.OCALLINTER)
// Construct new function body: f(x1, y1)
op := ir.OCALL
if irregular {
op = call.Op()
}
newcall := mkNewCall(call.Pos(), op, callX, newCallArgs)
// Type-check the result.
if !irregular {
typecheck.Call(newcall.(*ir.CallExpr))
} else {
typecheck.Stmt(newcall)
}
// Finalize body, register function on the main decls list.
fn.Body = []ir.Node{newcall}
typecheck.FinishFuncBody()
typecheck.Func(fn)
typecheck.Target.Decls = append(typecheck.Target.Decls, fn)
// Create closure expr
clo := ir.NewClosureExpr(n.Pos(), fn)
fn.OClosure = clo
clo.SetType(fn.Type())
// Set escape properties for closure.
if n.Op() == ir.OGO {
// For "go", assume that the closure is going to escape
// (with an exception for the runtime, which doesn't
// permit heap-allocated closures).
if base.Ctxt.Pkgpath != "runtime" {
clo.SetEsc(ir.EscHeap)
}
} else {
// For defer, just use whatever result escape analysis
// has determined for the defer.
if n.Esc() == ir.EscNever {
clo.SetTransient(true)
clo.SetEsc(ir.EscNone)
}
}
// Create new top level call to closure over argless function.
topcall := ir.NewCallExpr(n.Pos(), ir.OCALL, clo, []ir.Node{})
typecheck.Call(topcall)
// Tag the call to insure that directClosureCall doesn't undo our work.
topcall.PreserveClosure = true
fn.SetClosureCalled(false)
// Finally, point the defer statement at the newly generated call.
n.Call = topcall
}
// isFuncPCIntrinsic returns whether n is a direct call of internal/abi.FuncPCABIxxx functions.
func isFuncPCIntrinsic(n *ir.CallExpr) bool {
if n.Op() != ir.OCALLFUNC || n.X.Op() != ir.ONAME {
return false
}
fn := n.X.(*ir.Name).Sym()
return (fn.Name == "FuncPCABI0" || fn.Name == "FuncPCABIInternal") &&
(fn.Pkg.Path == "internal/abi" || fn.Pkg == types.LocalPkg && base.Ctxt.Pkgpath == "internal/abi")
}
// isIfaceOfFunc returns whether n is an interface conversion from a direct reference of a func.
func isIfaceOfFunc(n ir.Node) bool {
return n.Op() == ir.OCONVIFACE && n.(*ir.ConvExpr).X.Op() == ir.ONAME && n.(*ir.ConvExpr).X.(*ir.Name).Class == ir.PFUNC
}
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