1 // Copyright 2012 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
11 "cmd/compile/internal/base"
12 "cmd/compile/internal/ir"
13 "cmd/compile/internal/reflectdata"
14 "cmd/compile/internal/staticinit"
15 "cmd/compile/internal/typecheck"
16 "cmd/compile/internal/types"
21 // Rewrite tree to use separate statements to enforce
22 // order of evaluation. Makes walk easier, because it
23 // can (after this runs) reorder at will within an expression.
25 // Rewrite m[k] op= r into m[k] = m[k] op r if op is / or %.
27 // Introduce temporaries as needed by runtime routines.
28 // For example, the map runtime routines take the map key
29 // by reference, so make sure all map keys are addressable
30 // by copying them to temporaries as needed.
31 // The same is true for channel operations.
33 // Arrange that map index expressions only appear in direct
34 // assignments x = m[k] or m[k] = x, never in larger expressions.
36 // Arrange that receive expressions only appear in direct assignments
37 // x = <-c or as standalone statements <-c, never in larger expressions.
39 // TODO(rsc): The temporary introduction during multiple assignments
40 // should be moved into this file, so that the temporaries can be cleaned
41 // and so that conversions implicit in the OAS2FUNC and OAS2RECV
42 // nodes can be made explicit and then have their temporaries cleaned.
44 // TODO(rsc): Goto and multilevel break/continue can jump over
45 // inserted VARKILL annotations. Work out a way to handle these.
46 // The current implementation is safe, in that it will execute correctly.
47 // But it won't reuse temporaries as aggressively as it might, and
48 // it can result in unnecessary zeroing of those variables in the function
51 // orderState holds state during the ordering process.
52 type orderState struct {
53 out []ir.Node // list of generated statements
54 temp []*ir.Name // stack of temporary variables
55 free map[string][]*ir.Name // free list of unused temporaries, by type.LinkString().
56 edit func(ir.Node) ir.Node // cached closure of o.exprNoLHS
59 // Order rewrites fn.Nbody to apply the ordering constraints
60 // described in the comment at the top of the file.
61 func order(fn *ir.Func) {
63 s := fmt.Sprintf("\nbefore order %v", fn.Sym())
64 ir.DumpList(s, fn.Body)
67 orderBlock(&fn.Body, map[string][]*ir.Name{})
70 // append typechecks stmt and appends it to out.
71 func (o *orderState) append(stmt ir.Node) {
72 o.out = append(o.out, typecheck.Stmt(stmt))
75 // newTemp allocates a new temporary with the given type,
76 // pushes it onto the temp stack, and returns it.
77 // If clear is true, newTemp emits code to zero the temporary.
78 func (o *orderState) newTemp(t *types.Type, clear bool) *ir.Name {
81 if a := o.free[key]; len(a) > 0 {
83 if !types.Identical(t, v.Type()) {
84 base.Fatalf("expected %L to have type %v", v, t)
86 o.free[key] = a[:len(a)-1]
91 o.append(ir.NewAssignStmt(base.Pos, v, nil))
94 o.temp = append(o.temp, v)
98 // copyExpr behaves like newTemp but also emits
99 // code to initialize the temporary to the value n.
100 func (o *orderState) copyExpr(n ir.Node) *ir.Name {
101 return o.copyExpr1(n, false)
104 // copyExprClear is like copyExpr but clears the temp before assignment.
105 // It is provided for use when the evaluation of tmp = n turns into
106 // a function call that is passed a pointer to the temporary as the output space.
107 // If the call blocks before tmp has been written,
108 // the garbage collector will still treat the temporary as live,
109 // so we must zero it before entering that call.
110 // Today, this only happens for channel receive operations.
111 // (The other candidate would be map access, but map access
112 // returns a pointer to the result data instead of taking a pointer
114 func (o *orderState) copyExprClear(n ir.Node) *ir.Name {
115 return o.copyExpr1(n, true)
118 func (o *orderState) copyExpr1(n ir.Node, clear bool) *ir.Name {
120 v := o.newTemp(t, clear)
121 o.append(ir.NewAssignStmt(base.Pos, v, n))
125 // cheapExpr returns a cheap version of n.
126 // The definition of cheap is that n is a variable or constant.
127 // If not, cheapExpr allocates a new tmp, emits tmp = n,
128 // and then returns tmp.
129 func (o *orderState) cheapExpr(n ir.Node) ir.Node {
135 case ir.ONAME, ir.OLITERAL, ir.ONIL:
137 case ir.OLEN, ir.OCAP:
138 n := n.(*ir.UnaryExpr)
139 l := o.cheapExpr(n.X)
143 a := ir.SepCopy(n).(*ir.UnaryExpr)
145 return typecheck.Expr(a)
151 // safeExpr returns a safe version of n.
152 // The definition of safe is that n can appear multiple times
153 // without violating the semantics of the original program,
154 // and that assigning to the safe version has the same effect
155 // as assigning to the original n.
157 // The intended use is to apply to x when rewriting x += y into x = x + y.
158 func (o *orderState) safeExpr(n ir.Node) ir.Node {
160 case ir.ONAME, ir.OLITERAL, ir.ONIL:
163 case ir.OLEN, ir.OCAP:
164 n := n.(*ir.UnaryExpr)
169 a := ir.SepCopy(n).(*ir.UnaryExpr)
171 return typecheck.Expr(a)
174 n := n.(*ir.SelectorExpr)
179 a := ir.SepCopy(n).(*ir.SelectorExpr)
181 return typecheck.Expr(a)
184 n := n.(*ir.SelectorExpr)
185 l := o.cheapExpr(n.X)
189 a := ir.SepCopy(n).(*ir.SelectorExpr)
191 return typecheck.Expr(a)
194 n := n.(*ir.StarExpr)
195 l := o.cheapExpr(n.X)
199 a := ir.SepCopy(n).(*ir.StarExpr)
201 return typecheck.Expr(a)
203 case ir.OINDEX, ir.OINDEXMAP:
204 n := n.(*ir.IndexExpr)
206 if n.X.Type().IsArray() {
211 r := o.cheapExpr(n.Index)
212 if l == n.X && r == n.Index {
215 a := ir.SepCopy(n).(*ir.IndexExpr)
218 return typecheck.Expr(a)
221 base.Fatalf("order.safeExpr %v", n.Op())
222 return nil // not reached
226 // isaddrokay reports whether it is okay to pass n's address to runtime routines.
227 // Taking the address of a variable makes the liveness and optimization analyses
228 // lose track of where the variable's lifetime ends. To avoid hurting the analyses
229 // of ordinary stack variables, those are not 'isaddrokay'. Temporaries are okay,
230 // because we emit explicit VARKILL instructions marking the end of those
231 // temporaries' lifetimes.
232 func isaddrokay(n ir.Node) bool {
233 return ir.IsAddressable(n) && (n.Op() != ir.ONAME || n.(*ir.Name).Class == ir.PEXTERN || ir.IsAutoTmp(n))
236 // addrTemp ensures that n is okay to pass by address to runtime routines.
237 // If the original argument n is not okay, addrTemp creates a tmp, emits
238 // tmp = n, and then returns tmp.
239 // The result of addrTemp MUST be assigned back to n, e.g.
241 // n.Left = o.addrTemp(n.Left)
242 func (o *orderState) addrTemp(n ir.Node) ir.Node {
243 if n.Op() == ir.OLITERAL || n.Op() == ir.ONIL {
244 // TODO: expand this to all static composite literal nodes?
245 n = typecheck.DefaultLit(n, nil)
246 types.CalcSize(n.Type())
247 vstat := readonlystaticname(n.Type())
248 var s staticinit.Schedule
249 s.StaticAssign(vstat, 0, n, n.Type())
251 base.Fatalf("staticassign of const generated code: %+v", n)
253 vstat = typecheck.Expr(vstat).(*ir.Name)
262 // mapKeyTemp prepares n to be a key in a map runtime call and returns n.
263 // It should only be used for map runtime calls which have *_fast* versions.
264 func (o *orderState) mapKeyTemp(t *types.Type, n ir.Node) ir.Node {
265 // Most map calls need to take the address of the key.
266 // Exception: map*_fast* calls. See golang.org/issue/19015.
274 kt = types.Types[types.TUINT32]
276 kt = types.Types[types.TUINT64]
277 case mapfast32ptr, mapfast64ptr:
278 kt = types.Types[types.TUNSAFEPTR]
280 kt = types.Types[types.TSTRING]
286 case nt.Kind() == kt.Kind(), nt.IsPtrShaped() && kt.IsPtrShaped():
287 // can directly convert (e.g. named type to underlying type, or one pointer to another)
288 return typecheck.Expr(ir.NewConvExpr(n.Pos(), ir.OCONVNOP, kt, n))
289 case nt.IsInteger() && kt.IsInteger():
290 // can directly convert (e.g. int32 to uint32)
291 if n.Op() == ir.OLITERAL && nt.IsSigned() {
292 // avoid constant overflow error
293 n = ir.NewConstExpr(constant.MakeUint64(uint64(ir.Int64Val(n))), n)
297 return typecheck.Expr(ir.NewConvExpr(n.Pos(), ir.OCONV, kt, n))
299 // Unsafe cast through memory.
300 // We'll need to do a load with type kt. Create a temporary of type kt to
301 // ensure sufficient alignment. nt may be under-aligned.
302 if uint8(kt.Alignment()) < uint8(nt.Alignment()) {
303 base.Fatalf("mapKeyTemp: key type is not sufficiently aligned, kt=%v nt=%v", kt, nt)
305 tmp := o.newTemp(kt, true)
307 var e ir.Node = typecheck.NodAddr(tmp)
308 e = ir.NewConvExpr(n.Pos(), ir.OCONVNOP, nt.PtrTo(), e)
309 e = ir.NewStarExpr(n.Pos(), e)
310 o.append(ir.NewAssignStmt(base.Pos, e, n))
315 // mapKeyReplaceStrConv replaces OBYTES2STR by OBYTES2STRTMP
316 // in n to avoid string allocations for keys in map lookups.
317 // Returns a bool that signals if a modification was made.
322 // x = m[T1{... Tn{..., string(k), ...}]
324 // where k is []byte, T1 to Tn is a nesting of struct and array literals,
325 // the allocation of backing bytes for the string can be avoided
326 // by reusing the []byte backing array. These are special cases
327 // for avoiding allocations when converting byte slices to strings.
328 // It would be nice to handle these generally, but because
329 // []byte keys are not allowed in maps, the use of string(k)
330 // comes up in important cases in practice. See issue 3512.
331 func mapKeyReplaceStrConv(n ir.Node) bool {
335 n := n.(*ir.ConvExpr)
336 n.SetOp(ir.OBYTES2STRTMP)
339 n := n.(*ir.CompLitExpr)
340 for _, elem := range n.List {
341 elem := elem.(*ir.StructKeyExpr)
342 if mapKeyReplaceStrConv(elem.Value) {
347 n := n.(*ir.CompLitExpr)
348 for _, elem := range n.List {
349 if elem.Op() == ir.OKEY {
350 elem = elem.(*ir.KeyExpr).Value
352 if mapKeyReplaceStrConv(elem) {
362 // markTemp returns the top of the temporary variable stack.
363 func (o *orderState) markTemp() ordermarker {
364 return ordermarker(len(o.temp))
367 // popTemp pops temporaries off the stack until reaching the mark,
368 // which must have been returned by markTemp.
369 func (o *orderState) popTemp(mark ordermarker) {
370 for _, n := range o.temp[mark:] {
371 key := n.Type().LinkString()
372 o.free[key] = append(o.free[key], n)
374 o.temp = o.temp[:mark]
377 // cleanTempNoPop emits VARKILL instructions to *out
378 // for each temporary above the mark on the temporary stack.
379 // It does not pop the temporaries from the stack.
380 func (o *orderState) cleanTempNoPop(mark ordermarker) []ir.Node {
382 for i := len(o.temp) - 1; i >= int(mark); i-- {
384 out = append(out, typecheck.Stmt(ir.NewUnaryExpr(base.Pos, ir.OVARKILL, n)))
389 // cleanTemp emits VARKILL instructions for each temporary above the
390 // mark on the temporary stack and removes them from the stack.
391 func (o *orderState) cleanTemp(top ordermarker) {
392 o.out = append(o.out, o.cleanTempNoPop(top)...)
396 // stmtList orders each of the statements in the list.
397 func (o *orderState) stmtList(l ir.Nodes) {
400 orderMakeSliceCopy(s[i:])
405 // orderMakeSliceCopy matches the pattern:
407 // m = OMAKESLICE([]T, x); OCOPY(m, s)
409 // and rewrites it to:
411 // m = OMAKESLICECOPY([]T, x, s); nil
412 func orderMakeSliceCopy(s []ir.Node) {
413 if base.Flag.N != 0 || base.Flag.Cfg.Instrumenting {
416 if len(s) < 2 || s[0] == nil || s[0].Op() != ir.OAS || s[1] == nil || s[1].Op() != ir.OCOPY {
420 as := s[0].(*ir.AssignStmt)
421 cp := s[1].(*ir.BinaryExpr)
422 if as.Y == nil || as.Y.Op() != ir.OMAKESLICE || ir.IsBlank(as.X) ||
423 as.X.Op() != ir.ONAME || cp.X.Op() != ir.ONAME || cp.Y.Op() != ir.ONAME ||
424 as.X.Name() != cp.X.Name() || cp.X.Name() == cp.Y.Name() {
425 // The line above this one is correct with the differing equality operators:
426 // we want as.X and cp.X to be the same name,
427 // but we want the initial data to be coming from a different name.
431 mk := as.Y.(*ir.MakeExpr)
432 if mk.Esc() == ir.EscNone || mk.Len == nil || mk.Cap != nil {
435 mk.SetOp(ir.OMAKESLICECOPY)
437 // Set bounded when m = OMAKESLICE([]T, len(s)); OCOPY(m, s)
438 mk.SetBounded(mk.Len.Op() == ir.OLEN && ir.SameSafeExpr(mk.Len.(*ir.UnaryExpr).X, cp.Y))
439 as.Y = typecheck.Expr(mk)
440 s[1] = nil // remove separate copy call
443 // edge inserts coverage instrumentation for libfuzzer.
444 func (o *orderState) edge() {
445 if base.Debug.Libfuzzer == 0 {
449 // Create a new uint8 counter to be allocated in section
450 // __libfuzzer_extra_counters.
451 counter := staticinit.StaticName(types.Types[types.TUINT8])
452 counter.SetLibfuzzerExtraCounter(true)
453 // As well as setting SetLibfuzzerExtraCounter, we preemptively set the
454 // symbol type to SLIBFUZZER_EXTRA_COUNTER so that the race detector
455 // instrumentation pass (which does not have access to the flags set by
456 // SetLibfuzzerExtraCounter) knows to ignore them. This information is
457 // lost by the time it reaches the compile step, so SetLibfuzzerExtraCounter
458 // is still necessary.
459 counter.Linksym().Type = objabi.SLIBFUZZER_EXTRA_COUNTER
462 incr := ir.NewAssignOpStmt(base.Pos, ir.OADD, counter, ir.NewInt(1))
466 // orderBlock orders the block of statements in n into a new slice,
467 // and then replaces the old slice in n with the new slice.
468 // free is a map that can be used to obtain temporary variables by type.
469 func orderBlock(n *ir.Nodes, free map[string][]*ir.Name) {
472 mark := order.markTemp()
475 order.cleanTemp(mark)
479 // exprInPlace orders the side effects in *np and
480 // leaves them as the init list of the final *np.
481 // The result of exprInPlace MUST be assigned back to n, e.g.
483 // n.Left = o.exprInPlace(n.Left)
484 func (o *orderState) exprInPlace(n ir.Node) ir.Node {
487 n = order.expr(n, nil)
488 n = ir.InitExpr(order.out, n)
490 // insert new temporaries from order
491 // at head of outer list.
492 o.temp = append(o.temp, order.temp...)
496 // orderStmtInPlace orders the side effects of the single statement *np
497 // and replaces it with the resulting statement list.
498 // The result of orderStmtInPlace MUST be assigned back to n, e.g.
500 // n.Left = orderStmtInPlace(n.Left)
502 // free is a map that can be used to obtain temporary variables by type.
503 func orderStmtInPlace(n ir.Node, free map[string][]*ir.Name) ir.Node {
506 mark := order.markTemp()
508 order.cleanTemp(mark)
509 return ir.NewBlockStmt(src.NoXPos, order.out)
512 // init moves n's init list to o.out.
513 func (o *orderState) init(n ir.Node) {
514 if ir.MayBeShared(n) {
515 // For concurrency safety, don't mutate potentially shared nodes.
516 // First, ensure that no work is required here.
517 if len(n.Init()) > 0 {
518 base.Fatalf("order.init shared node with ninit")
522 o.stmtList(ir.TakeInit(n))
525 // call orders the call expression n.
526 // n.Op is OCALLFUNC/OCALLINTER or a builtin like OCOPY.
527 func (o *orderState) call(nn ir.Node) {
528 if len(nn.Init()) > 0 {
529 // Caller should have already called o.init(nn).
530 base.Fatalf("%v with unexpected ninit", nn.Op())
532 if nn.Op() == ir.OCALLMETH {
533 base.FatalfAt(nn.Pos(), "OCALLMETH missed by typecheck")
536 // Builtin functions.
537 if nn.Op() != ir.OCALLFUNC && nn.Op() != ir.OCALLINTER {
538 switch n := nn.(type) {
540 base.Fatalf("unexpected call: %+v", n)
542 n.X = o.expr(n.X, nil)
544 n.X = o.expr(n.X, nil)
546 n.X = o.expr(n.X, nil)
547 n.Y = o.expr(n.Y, nil)
549 n.Len = o.expr(n.Len, nil)
550 n.Cap = o.expr(n.Cap, nil)
557 n := nn.(*ir.CallExpr)
558 typecheck.FixVariadicCall(n)
560 if isFuncPCIntrinsic(n) && isIfaceOfFunc(n.Args[0]) {
561 // For internal/abi.FuncPCABIxxx(fn), if fn is a defined function,
562 // do not introduce temporaries here, so it is easier to rewrite it
563 // to symbol address reference later in walk.
567 n.X = o.expr(n.X, nil)
571 // mapAssign appends n to o.out.
572 func (o *orderState) mapAssign(n ir.Node) {
575 base.Fatalf("order.mapAssign %v", n.Op())
578 n := n.(*ir.AssignStmt)
579 if n.X.Op() == ir.OINDEXMAP {
580 n.Y = o.safeMapRHS(n.Y)
582 o.out = append(o.out, n)
584 n := n.(*ir.AssignOpStmt)
585 if n.X.Op() == ir.OINDEXMAP {
586 n.Y = o.safeMapRHS(n.Y)
588 o.out = append(o.out, n)
592 func (o *orderState) safeMapRHS(r ir.Node) ir.Node {
593 // Make sure we evaluate the RHS before starting the map insert.
594 // We need to make sure the RHS won't panic. See issue 22881.
595 if r.Op() == ir.OAPPEND {
596 r := r.(*ir.CallExpr)
598 for i, n := range s {
599 s[i] = o.cheapExpr(n)
603 return o.cheapExpr(r)
606 // stmt orders the statement n, appending to o.out.
607 // Temporaries created during the statement are cleaned
608 // up using VARKILL instructions as possible.
609 func (o *orderState) stmt(n ir.Node) {
619 base.Fatalf("order.stmt %v", n.Op())
621 case ir.OVARKILL, ir.OVARLIVE, ir.OINLMARK:
622 o.out = append(o.out, n)
625 n := n.(*ir.AssignStmt)
627 n.X = o.expr(n.X, nil)
628 n.Y = o.expr(n.Y, n.X)
633 n := n.(*ir.AssignOpStmt)
635 n.X = o.expr(n.X, nil)
636 n.Y = o.expr(n.Y, nil)
638 if base.Flag.Cfg.Instrumenting || n.X.Op() == ir.OINDEXMAP && (n.AsOp == ir.ODIV || n.AsOp == ir.OMOD) {
639 // Rewrite m[k] op= r into m[k] = m[k] op r so
640 // that we can ensure that if op panics
641 // because r is zero, the panic happens before
642 // the map assignment.
643 // DeepCopy is a big hammer here, but safeExpr
644 // makes sure there is nothing too deep being copied.
645 l1 := o.safeExpr(n.X)
646 l2 := ir.DeepCopy(src.NoXPos, l1)
647 if l2.Op() == ir.OINDEXMAP {
648 l2 := l2.(*ir.IndexExpr)
652 r := o.expr(typecheck.Expr(ir.NewBinaryExpr(n.Pos(), n.AsOp, l2, n.Y)), nil)
653 as := typecheck.Stmt(ir.NewAssignStmt(n.Pos(), l1, r))
663 n := n.(*ir.AssignListStmt)
667 o.out = append(o.out, n)
670 // Special: avoid copy of func call n.Right
672 n := n.(*ir.AssignListStmt)
677 if ic, ok := call.(*ir.InlinedCallExpr); ok {
681 n.Rhs = ic.ReturnVars
684 o.out = append(o.out, n)
691 // Special: use temporary variables to hold result,
692 // so that runtime can take address of temporary.
693 // No temporary for blank assignment.
695 // OAS2MAPR: make sure key is addressable if needed,
696 // and make sure OINDEXMAP is not copied out.
697 case ir.OAS2DOTTYPE, ir.OAS2RECV, ir.OAS2MAPR:
698 n := n.(*ir.AssignListStmt)
702 switch r := n.Rhs[0]; r.Op() {
704 r := r.(*ir.TypeAssertExpr)
705 r.X = o.expr(r.X, nil)
706 case ir.ODYNAMICDOTTYPE2:
707 r := r.(*ir.DynamicTypeAssertExpr)
708 r.X = o.expr(r.X, nil)
709 r.RType = o.expr(r.RType, nil)
710 r.ITab = o.expr(r.ITab, nil)
712 r := r.(*ir.UnaryExpr)
713 r.X = o.expr(r.X, nil)
715 r := r.(*ir.IndexExpr)
716 r.X = o.expr(r.X, nil)
717 r.Index = o.expr(r.Index, nil)
718 // See similar conversion for OINDEXMAP below.
719 _ = mapKeyReplaceStrConv(r.Index)
720 r.Index = o.mapKeyTemp(r.X.Type(), r.Index)
722 base.Fatalf("order.stmt: %v", r.Op())
728 // Special: does not save n onto out.
730 n := n.(*ir.BlockStmt)
733 // Special: n->left is not an expression; save as is.
743 o.out = append(o.out, n)
745 // Special: handle call arguments.
746 case ir.OCALLFUNC, ir.OCALLINTER:
747 n := n.(*ir.CallExpr)
750 o.out = append(o.out, n)
754 n := n.(*ir.InlinedCallExpr)
757 // discard results; double-check for no side effects
758 for _, result := range n.ReturnVars {
759 if staticinit.AnySideEffects(result) {
760 base.FatalfAt(result.Pos(), "inlined call result has side effects: %v", result)
764 case ir.OCHECKNIL, ir.OCLOSE, ir.OPANIC, ir.ORECV:
765 n := n.(*ir.UnaryExpr)
767 n.X = o.expr(n.X, nil)
768 o.out = append(o.out, n)
772 n := n.(*ir.BinaryExpr)
774 n.X = o.expr(n.X, nil)
775 n.Y = o.expr(n.Y, nil)
776 o.out = append(o.out, n)
779 case ir.OPRINT, ir.OPRINTN, ir.ORECOVERFP:
780 n := n.(*ir.CallExpr)
783 o.out = append(o.out, n)
786 // Special: order arguments to inner call but not call itself.
787 case ir.ODEFER, ir.OGO:
788 n := n.(*ir.GoDeferStmt)
792 o.out = append(o.out, n)
796 n := n.(*ir.CallExpr)
798 n.Args[0] = o.expr(n.Args[0], nil)
799 n.Args[1] = o.expr(n.Args[1], nil)
800 n.Args[1] = o.mapKeyTemp(n.Args[0].Type(), n.Args[1])
801 o.out = append(o.out, n)
804 // Clean temporaries from condition evaluation at
805 // beginning of loop body and after for statement.
809 n.Cond = o.exprInPlace(n.Cond)
810 n.Body.Prepend(o.cleanTempNoPop(t)...)
811 orderBlock(&n.Body, o.free)
812 n.Post = orderStmtInPlace(n.Post, o.free)
813 o.out = append(o.out, n)
816 // Clean temporaries from condition at
817 // beginning of both branches.
821 n.Cond = o.exprInPlace(n.Cond)
822 n.Body.Prepend(o.cleanTempNoPop(t)...)
823 n.Else.Prepend(o.cleanTempNoPop(t)...)
825 orderBlock(&n.Body, o.free)
826 orderBlock(&n.Else, o.free)
827 o.out = append(o.out, n)
830 // n.Right is the expression being ranged over.
831 // order it, and then make a copy if we need one.
832 // We almost always do, to ensure that we don't
833 // see any value changes made during the loop.
834 // Usually the copy is cheap (e.g., array pointer,
835 // chan, slice, string are all tiny).
836 // The exception is ranging over an array value
837 // (not a slice, not a pointer to array),
838 // which must make a copy to avoid seeing updates made during
839 // the range body. Ranging over an array value is uncommon though.
841 // Mark []byte(str) range expression to reuse string backing storage.
842 // It is safe because the storage cannot be mutated.
843 n := n.(*ir.RangeStmt)
844 if n.X.Op() == ir.OSTR2BYTES {
845 n.X.(*ir.ConvExpr).SetOp(ir.OSTR2BYTESTMP)
849 n.X = o.expr(n.X, nil)
852 xt := typecheck.RangeExprType(n.X.Type())
855 base.Fatalf("order.stmt range %v", n.Type())
857 case types.TARRAY, types.TSLICE:
858 if n.Value == nil || ir.IsBlank(n.Value) {
859 // for i := range x will only use x once, to compute len(x).
860 // No need to copy it.
865 case types.TCHAN, types.TSTRING:
866 // chan, string, slice, array ranges use value multiple times.
870 if r.Type().IsString() && r.Type() != types.Types[types.TSTRING] {
871 r = ir.NewConvExpr(base.Pos, ir.OCONV, nil, r)
872 r.SetType(types.Types[types.TSTRING])
873 r = typecheck.Expr(r)
880 // Preserve the body of the map clear pattern so it can
881 // be detected during walk. The loop body will not be used
882 // when optimizing away the range loop to a runtime call.
887 // copy the map value in case it is a map literal.
888 // TODO(rsc): Make tmp = literal expressions reuse tmp.
889 // For maps tmp is just one word so it hardly matters.
893 // n.Prealloc is the temp for the iterator.
894 // MapIterType contains pointers and needs to be zeroed.
895 n.Prealloc = o.newTemp(reflectdata.MapIterType(xt), true)
897 n.Key = o.exprInPlace(n.Key)
898 n.Value = o.exprInPlace(n.Value)
900 orderBlock(&n.Body, o.free)
902 o.out = append(o.out, n)
906 n := n.(*ir.ReturnStmt)
907 o.exprList(n.Results)
908 o.out = append(o.out, n)
910 // Special: clean case temporaries in each block entry.
911 // Select must enter one of its blocks, so there is no
912 // need for a cleaning at the end.
913 // Doubly special: evaluation order for select is stricter
914 // than ordinary expressions. Even something like p.c
915 // has to be hoisted into a temporary, so that it cannot be
916 // reordered after the channel evaluation for a different
917 // case (if p were nil, then the timing of the fault would
920 n := n.(*ir.SelectStmt)
922 for _, ncas := range n.Cases {
926 // Append any new body prologue to ninit.
927 // The next loop will insert ninit into nbody.
928 if len(ncas.Init()) != 0 {
929 base.Fatalf("order select ninit")
936 ir.Dump("select case", r)
937 base.Fatalf("unknown op in select %v", r.Op())
941 r := r.(*ir.AssignListStmt)
942 recv := r.Rhs[0].(*ir.UnaryExpr)
943 recv.X = o.expr(recv.X, nil)
944 if !ir.IsAutoTmp(recv.X) {
945 recv.X = o.copyExpr(recv.X)
947 init := ir.TakeInit(r)
950 do := func(i int, t *types.Type) {
955 // If this is case x := <-ch or case x, y := <-ch, the case has
956 // the ODCL nodes to declare x and y. We want to delay that
957 // declaration (and possible allocation) until inside the case body.
958 // Delete the ODCL nodes here and recreate them inside the body below.
960 if len(init) > 0 && init[0].Op() == ir.ODCL && init[0].(*ir.Decl).X == n {
963 // iimport may have added a default initialization assignment,
964 // due to how it handles ODCL statements.
965 if len(init) > 0 && init[0].Op() == ir.OAS && init[0].(*ir.AssignStmt).X == n {
969 dcl := typecheck.Stmt(ir.NewDecl(base.Pos, ir.ODCL, n.(*ir.Name)))
970 ncas.PtrInit().Append(dcl)
972 tmp := o.newTemp(t, t.HasPointers())
973 as := typecheck.Stmt(ir.NewAssignStmt(base.Pos, n, typecheck.Conv(tmp, n.Type())))
974 ncas.PtrInit().Append(as)
977 do(0, recv.X.Type().Elem())
978 do(1, types.Types[types.TBOOL])
980 ir.DumpList("ninit", r.Init())
981 base.Fatalf("ninit on select recv")
983 orderBlock(ncas.PtrInit(), o.free)
986 r := r.(*ir.SendStmt)
987 if len(r.Init()) != 0 {
988 ir.DumpList("ninit", r.Init())
989 base.Fatalf("ninit on select send")
993 // r->left is c, r->right is x, both are always evaluated.
994 r.Chan = o.expr(r.Chan, nil)
996 if !ir.IsAutoTmp(r.Chan) {
997 r.Chan = o.copyExpr(r.Chan)
999 r.Value = o.expr(r.Value, nil)
1000 if !ir.IsAutoTmp(r.Value) {
1001 r.Value = o.copyExpr(r.Value)
1005 // Now that we have accumulated all the temporaries, clean them.
1006 // Also insert any ninit queued during the previous loop.
1007 // (The temporary cleaning must follow that ninit work.)
1008 for _, cas := range n.Cases {
1009 orderBlock(&cas.Body, o.free)
1010 cas.Body.Prepend(o.cleanTempNoPop(t)...)
1012 // TODO(mdempsky): Is this actually necessary?
1013 // walkSelect appears to walk Ninit.
1014 cas.Body.Prepend(ir.TakeInit(cas)...)
1017 o.out = append(o.out, n)
1020 // Special: value being sent is passed as a pointer; make it addressable.
1022 n := n.(*ir.SendStmt)
1024 n.Chan = o.expr(n.Chan, nil)
1025 n.Value = o.expr(n.Value, nil)
1026 if base.Flag.Cfg.Instrumenting {
1027 // Force copying to the stack so that (chan T)(nil) <- x
1028 // is still instrumented as a read of x.
1029 n.Value = o.copyExpr(n.Value)
1031 n.Value = o.addrTemp(n.Value)
1033 o.out = append(o.out, n)
1036 // TODO(rsc): Clean temporaries more aggressively.
1037 // Note that because walkSwitch will rewrite some of the
1038 // switch into a binary search, this is not as easy as it looks.
1039 // (If we ran that code here we could invoke order.stmt on
1040 // the if-else chain instead.)
1041 // For now just clean all the temporaries at the end.
1042 // In practice that's fine.
1044 n := n.(*ir.SwitchStmt)
1045 if base.Debug.Libfuzzer != 0 && !hasDefaultCase(n) {
1046 // Add empty "default:" case for instrumentation.
1047 n.Cases = append(n.Cases, ir.NewCaseStmt(base.Pos, nil, nil))
1051 n.Tag = o.expr(n.Tag, nil)
1052 for _, ncas := range n.Cases {
1053 o.exprListInPlace(ncas.List)
1054 orderBlock(&ncas.Body, o.free)
1057 o.out = append(o.out, n)
1064 func hasDefaultCase(n *ir.SwitchStmt) bool {
1065 for _, ncas := range n.Cases {
1066 if len(ncas.List) == 0 {
1073 // exprList orders the expression list l into o.
1074 func (o *orderState) exprList(l ir.Nodes) {
1077 s[i] = o.expr(s[i], nil)
1081 // exprListInPlace orders the expression list l but saves
1082 // the side effects on the individual expression ninit lists.
1083 func (o *orderState) exprListInPlace(l ir.Nodes) {
1086 s[i] = o.exprInPlace(s[i])
1090 func (o *orderState) exprNoLHS(n ir.Node) ir.Node {
1091 return o.expr(n, nil)
1094 // expr orders a single expression, appending side
1095 // effects to o.out as needed.
1096 // If this is part of an assignment lhs = *np, lhs is given.
1097 // Otherwise lhs == nil. (When lhs != nil it may be possible
1098 // to avoid copying the result of the expression to a temporary.)
1099 // The result of expr MUST be assigned back to n, e.g.
1101 // n.Left = o.expr(n.Left, lhs)
1102 func (o *orderState) expr(n, lhs ir.Node) ir.Node {
1112 func (o *orderState) expr1(n, lhs ir.Node) ir.Node {
1118 o.edit = o.exprNoLHS // create closure once
1120 ir.EditChildren(n, o.edit)
1123 // Addition of strings turns into a function call.
1124 // Allocate a temporary to hold the strings.
1125 // Fewer than 5 strings use direct runtime helpers.
1127 n := n.(*ir.AddStringExpr)
1130 if len(n.List) > 5 {
1131 t := types.NewArray(types.Types[types.TSTRING], int64(len(n.List)))
1132 n.Prealloc = o.newTemp(t, false)
1135 // Mark string(byteSlice) arguments to reuse byteSlice backing
1136 // buffer during conversion. String concatenation does not
1137 // memorize the strings for later use, so it is safe.
1138 // However, we can do it only if there is at least one non-empty string literal.
1139 // Otherwise if all other arguments are empty strings,
1140 // concatstrings will return the reference to the temp string
1145 for _, n1 := range n.List {
1146 hasbyte = hasbyte || n1.Op() == ir.OBYTES2STR
1147 haslit = haslit || n1.Op() == ir.OLITERAL && len(ir.StringVal(n1)) != 0
1150 if haslit && hasbyte {
1151 for _, n2 := range n.List {
1152 if n2.Op() == ir.OBYTES2STR {
1153 n2 := n2.(*ir.ConvExpr)
1154 n2.SetOp(ir.OBYTES2STRTMP)
1161 n := n.(*ir.IndexExpr)
1162 n.X = o.expr(n.X, nil)
1163 n.Index = o.expr(n.Index, nil)
1167 // Enforce that any []byte slices we are not copying
1168 // can not be changed before the map index by forcing
1169 // the map index to happen immediately following the
1170 // conversions. See copyExpr a few lines below.
1171 needCopy = mapKeyReplaceStrConv(n.Index)
1173 if base.Flag.Cfg.Instrumenting {
1174 // Race detector needs the copy.
1179 // key must be addressable
1180 n.Index = o.mapKeyTemp(n.X.Type(), n.Index)
1182 return o.copyExpr(n)
1186 // concrete type (not interface) argument might need an addressable
1187 // temporary to pass to the runtime conversion routine.
1188 case ir.OCONVIFACE, ir.OCONVIDATA:
1189 n := n.(*ir.ConvExpr)
1190 n.X = o.expr(n.X, nil)
1191 if n.X.Type().IsInterface() {
1194 if _, _, needsaddr := dataWordFuncName(n.X.Type()); needsaddr || isStaticCompositeLiteral(n.X) {
1195 // Need a temp if we need to pass the address to the conversion function.
1196 // We also process static composite literal node here, making a named static global
1197 // whose address we can put directly in an interface (see OCONVIFACE/OCONVIDATA case in walk).
1198 n.X = o.addrTemp(n.X)
1203 n := n.(*ir.ConvExpr)
1204 if n.X.Op() == ir.OCALLMETH {
1205 base.FatalfAt(n.X.Pos(), "OCALLMETH missed by typecheck")
1207 if n.Type().IsKind(types.TUNSAFEPTR) && n.X.Type().IsKind(types.TUINTPTR) && (n.X.Op() == ir.OCALLFUNC || n.X.Op() == ir.OCALLINTER) {
1208 call := n.X.(*ir.CallExpr)
1209 // When reordering unsafe.Pointer(f()) into a separate
1210 // statement, the conversion and function call must stay
1211 // together. See golang.org/issue/15329.
1214 if lhs == nil || lhs.Op() != ir.ONAME || base.Flag.Cfg.Instrumenting {
1215 return o.copyExpr(n)
1218 n.X = o.expr(n.X, nil)
1222 case ir.OANDAND, ir.OOROR:
1227 // if r { // or !r, for OROR
1232 n := n.(*ir.LogicalExpr)
1233 r := o.newTemp(n.Type(), false)
1235 // Evaluate left-hand side.
1236 lhs := o.expr(n.X, nil)
1237 o.out = append(o.out, typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, lhs)))
1239 // Evaluate right-hand side, save generated code.
1244 rhs := o.expr(n.Y, nil)
1245 o.out = append(o.out, typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, rhs)))
1250 // If left-hand side doesn't cause a short-circuit, issue right-hand side.
1251 nif := ir.NewIfStmt(base.Pos, r, nil, nil)
1252 if n.Op() == ir.OANDAND {
1257 o.out = append(o.out, nif)
1261 base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
1262 panic("unreachable")
1283 // len([]rune(s)) is rewritten to runtime.countrunes(s) later.
1284 conv := n.(*ir.UnaryExpr).X.(*ir.ConvExpr)
1285 conv.X = o.expr(conv.X, nil)
1290 if lhs == nil || lhs.Op() != ir.ONAME || base.Flag.Cfg.Instrumenting {
1291 return o.copyExpr(n)
1296 n := n.(*ir.InlinedCallExpr)
1298 return n.SingleResult()
1301 // Check for append(x, make([]T, y)...) .
1302 n := n.(*ir.CallExpr)
1303 if isAppendOfMake(n) {
1304 n.Args[0] = o.expr(n.Args[0], nil) // order x
1305 mk := n.Args[1].(*ir.MakeExpr)
1306 mk.Len = o.expr(mk.Len, nil) // order y
1311 if lhs == nil || lhs.Op() != ir.ONAME && !ir.SameSafeExpr(lhs, n.Args[0]) {
1312 return o.copyExpr(n)
1316 case ir.OSLICE, ir.OSLICEARR, ir.OSLICESTR, ir.OSLICE3, ir.OSLICE3ARR:
1317 n := n.(*ir.SliceExpr)
1318 n.X = o.expr(n.X, nil)
1319 n.Low = o.cheapExpr(o.expr(n.Low, nil))
1320 n.High = o.cheapExpr(o.expr(n.High, nil))
1321 n.Max = o.cheapExpr(o.expr(n.Max, nil))
1322 if lhs == nil || lhs.Op() != ir.ONAME && !ir.SameSafeExpr(lhs, n.X) {
1323 return o.copyExpr(n)
1328 n := n.(*ir.ClosureExpr)
1329 if n.Transient() && len(n.Func.ClosureVars) > 0 {
1330 n.Prealloc = o.newTemp(typecheck.ClosureType(n), false)
1335 n := n.(*ir.SelectorExpr)
1336 n.X = o.expr(n.X, nil)
1338 t := typecheck.MethodValueType(n)
1339 n.Prealloc = o.newTemp(t, false)
1344 n := n.(*ir.CompLitExpr)
1347 t := types.NewArray(n.Type().Elem(), n.Len)
1348 n.Prealloc = o.newTemp(t, false)
1352 case ir.ODOTTYPE, ir.ODOTTYPE2:
1353 n := n.(*ir.TypeAssertExpr)
1354 n.X = o.expr(n.X, nil)
1355 if !types.IsDirectIface(n.Type()) || base.Flag.Cfg.Instrumenting {
1356 return o.copyExprClear(n)
1361 n := n.(*ir.UnaryExpr)
1362 n.X = o.expr(n.X, nil)
1363 return o.copyExprClear(n)
1365 case ir.OEQ, ir.ONE, ir.OLT, ir.OLE, ir.OGT, ir.OGE:
1366 n := n.(*ir.BinaryExpr)
1367 n.X = o.expr(n.X, nil)
1368 n.Y = o.expr(n.Y, nil)
1373 // Mark string(byteSlice) arguments to reuse byteSlice backing
1374 // buffer during conversion. String comparison does not
1375 // memorize the strings for later use, so it is safe.
1376 if n.X.Op() == ir.OBYTES2STR {
1377 n.X.(*ir.ConvExpr).SetOp(ir.OBYTES2STRTMP)
1379 if n.Y.Op() == ir.OBYTES2STR {
1380 n.Y.(*ir.ConvExpr).SetOp(ir.OBYTES2STRTMP)
1383 case t.IsStruct() || t.IsArray():
1384 // for complex comparisons, we need both args to be
1385 // addressable so we can pass them to the runtime.
1386 n.X = o.addrTemp(n.X)
1387 n.Y = o.addrTemp(n.Y)
1392 // Order map by converting:
1399 // m := map[int]int{}
1403 // Then order the result.
1404 // Without this special case, order would otherwise compute all
1405 // the keys and values before storing any of them to the map.
1407 n := n.(*ir.CompLitExpr)
1409 statics := entries[:0]
1410 var dynamics []*ir.KeyExpr
1411 for _, r := range entries {
1412 r := r.(*ir.KeyExpr)
1414 if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
1415 dynamics = append(dynamics, r)
1419 // Recursively ordering some static entries can change them to dynamic;
1420 // e.g., OCONVIFACE nodes. See #31777.
1421 r = o.expr(r, nil).(*ir.KeyExpr)
1422 if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
1423 dynamics = append(dynamics, r)
1427 statics = append(statics, r)
1431 if len(dynamics) == 0 {
1435 // Emit the creation of the map (with all its static entries).
1436 m := o.newTemp(n.Type(), false)
1437 as := ir.NewAssignStmt(base.Pos, m, n)
1441 // Emit eval+insert of dynamic entries, one at a time.
1442 for _, r := range dynamics {
1443 as := ir.NewAssignStmt(base.Pos, ir.NewIndexExpr(base.Pos, m, r.Key), r.Value)
1444 typecheck.Stmt(as) // Note: this converts the OINDEX to an OINDEXMAP
1448 // Remember that we issued these assignments so we can include that count
1449 // in the map alloc hint.
1450 // We're assuming here that all the keys in the map literal are distinct.
1451 // If any are equal, this will be an overcount. Probably not worth accounting
1452 // for that, as equal keys in map literals are rare, and at worst we waste
1454 n.Len += int64(len(dynamics))
1459 // No return - type-assertions above. Each case must return for itself.
1462 // as2func orders OAS2FUNC nodes. It creates temporaries to ensure left-to-right assignment.
1463 // The caller should order the right-hand side of the assignment before calling order.as2func.
1470 // tmp1, tmp2, tmp3 = ...
1471 // a, b, a = tmp1, tmp2, tmp3
1473 // This is necessary to ensure left to right assignment order.
1474 func (o *orderState) as2func(n *ir.AssignListStmt) {
1475 results := n.Rhs[0].Type()
1476 as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
1477 for i, nl := range n.Lhs {
1478 if !ir.IsBlank(nl) {
1479 typ := results.Field(i).Type
1480 tmp := o.newTemp(typ, typ.HasPointers())
1482 as.Lhs = append(as.Lhs, nl)
1483 as.Rhs = append(as.Rhs, tmp)
1487 o.out = append(o.out, n)
1488 o.stmt(typecheck.Stmt(as))
1491 // as2ok orders OAS2XXX with ok.
1492 // Just like as2func, this also adds temporaries to ensure left-to-right assignment.
1493 func (o *orderState) as2ok(n *ir.AssignListStmt) {
1494 as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
1496 do := func(i int, typ *types.Type) {
1497 if nl := n.Lhs[i]; !ir.IsBlank(nl) {
1498 var tmp ir.Node = o.newTemp(typ, typ.HasPointers())
1500 as.Lhs = append(as.Lhs, nl)
1502 // The "ok" result is an untyped boolean according to the Go
1503 // spec. We need to explicitly convert it to the LHS type in
1504 // case the latter is a defined boolean type (#8475).
1505 tmp = typecheck.Conv(tmp, nl.Type())
1507 as.Rhs = append(as.Rhs, tmp)
1511 do(0, n.Rhs[0].Type())
1512 do(1, types.Types[types.TBOOL])
1514 o.out = append(o.out, n)
1515 o.stmt(typecheck.Stmt(as))
1518 // isFuncPCIntrinsic returns whether n is a direct call of internal/abi.FuncPCABIxxx functions.
1519 func isFuncPCIntrinsic(n *ir.CallExpr) bool {
1520 if n.Op() != ir.OCALLFUNC || n.X.Op() != ir.ONAME {
1523 fn := n.X.(*ir.Name).Sym()
1524 return (fn.Name == "FuncPCABI0" || fn.Name == "FuncPCABIInternal") &&
1525 (fn.Pkg.Path == "internal/abi" || fn.Pkg == types.LocalPkg && base.Ctxt.Pkgpath == "internal/abi")
1528 // isIfaceOfFunc returns whether n is an interface conversion from a direct reference of a func.
1529 func isIfaceOfFunc(n ir.Node) bool {
1530 return n.Op() == ir.OCONVIFACE && n.(*ir.ConvExpr).X.Op() == ir.ONAME && n.(*ir.ConvExpr).X.(*ir.Name).Class == ir.PFUNC