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.
10 "cmd/compile/internal/base"
11 "cmd/compile/internal/escape"
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"
20 // Rewrite tree to use separate statements to enforce
21 // order of evaluation. Makes walk easier, because it
22 // can (after this runs) reorder at will within an expression.
24 // Rewrite m[k] op= r into m[k] = m[k] op r if op is / or %.
26 // Introduce temporaries as needed by runtime routines.
27 // For example, the map runtime routines take the map key
28 // by reference, so make sure all map keys are addressable
29 // by copying them to temporaries as needed.
30 // The same is true for channel operations.
32 // Arrange that map index expressions only appear in direct
33 // assignments x = m[k] or m[k] = x, never in larger expressions.
35 // Arrange that receive expressions only appear in direct assignments
36 // x = <-c or as standalone statements <-c, never in larger expressions.
38 // TODO(rsc): The temporary introduction during multiple assignments
39 // should be moved into this file, so that the temporaries can be cleaned
40 // and so that conversions implicit in the OAS2FUNC and OAS2RECV
41 // nodes can be made explicit and then have their temporaries cleaned.
43 // TODO(rsc): Goto and multilevel break/continue can jump over
44 // inserted VARKILL annotations. Work out a way to handle these.
45 // The current implementation is safe, in that it will execute correctly.
46 // But it won't reuse temporaries as aggressively as it might, and
47 // it can result in unnecessary zeroing of those variables in the function
50 // orderState holds state during the ordering process.
51 type orderState struct {
52 out []ir.Node // list of generated statements
53 temp []*ir.Name // stack of temporary variables
54 free map[string][]*ir.Name // free list of unused temporaries, by type.LongString().
55 edit func(ir.Node) ir.Node // cached closure of o.exprNoLHS
58 // Order rewrites fn.Nbody to apply the ordering constraints
59 // described in the comment at the top of the file.
60 func order(fn *ir.Func) {
62 s := fmt.Sprintf("\nbefore order %v", fn.Sym())
63 ir.DumpList(s, fn.Body)
66 orderBlock(&fn.Body, map[string][]*ir.Name{})
69 // append typechecks stmt and appends it to out.
70 func (o *orderState) append(stmt ir.Node) {
71 o.out = append(o.out, typecheck.Stmt(stmt))
74 // newTemp allocates a new temporary with the given type,
75 // pushes it onto the temp stack, and returns it.
76 // If clear is true, newTemp emits code to zero the temporary.
77 func (o *orderState) newTemp(t *types.Type, clear bool) *ir.Name {
79 // Note: LongString is close to the type equality we want,
80 // but not exactly. We still need to double-check with types.Identical.
84 if types.Identical(t, n.Type()) {
96 o.append(ir.NewAssignStmt(base.Pos, v, nil))
99 o.temp = append(o.temp, v)
103 // copyExpr behaves like newTemp but also emits
104 // code to initialize the temporary to the value n.
105 func (o *orderState) copyExpr(n ir.Node) *ir.Name {
106 return o.copyExpr1(n, false)
109 // copyExprClear is like copyExpr but clears the temp before assignment.
110 // It is provided for use when the evaluation of tmp = n turns into
111 // a function call that is passed a pointer to the temporary as the output space.
112 // If the call blocks before tmp has been written,
113 // the garbage collector will still treat the temporary as live,
114 // so we must zero it before entering that call.
115 // Today, this only happens for channel receive operations.
116 // (The other candidate would be map access, but map access
117 // returns a pointer to the result data instead of taking a pointer
119 func (o *orderState) copyExprClear(n ir.Node) *ir.Name {
120 return o.copyExpr1(n, true)
123 func (o *orderState) copyExpr1(n ir.Node, clear bool) *ir.Name {
125 v := o.newTemp(t, clear)
126 o.append(ir.NewAssignStmt(base.Pos, v, n))
130 // cheapExpr returns a cheap version of n.
131 // The definition of cheap is that n is a variable or constant.
132 // If not, cheapExpr allocates a new tmp, emits tmp = n,
133 // and then returns tmp.
134 func (o *orderState) cheapExpr(n ir.Node) ir.Node {
140 case ir.ONAME, ir.OLITERAL, ir.ONIL:
142 case ir.OLEN, ir.OCAP:
143 n := n.(*ir.UnaryExpr)
144 l := o.cheapExpr(n.X)
148 a := ir.SepCopy(n).(*ir.UnaryExpr)
150 return typecheck.Expr(a)
156 // safeExpr returns a safe version of n.
157 // The definition of safe is that n can appear multiple times
158 // without violating the semantics of the original program,
159 // and that assigning to the safe version has the same effect
160 // as assigning to the original n.
162 // The intended use is to apply to x when rewriting x += y into x = x + y.
163 func (o *orderState) safeExpr(n ir.Node) ir.Node {
165 case ir.ONAME, ir.OLITERAL, ir.ONIL:
168 case ir.OLEN, ir.OCAP:
169 n := n.(*ir.UnaryExpr)
174 a := ir.SepCopy(n).(*ir.UnaryExpr)
176 return typecheck.Expr(a)
179 n := n.(*ir.SelectorExpr)
184 a := ir.SepCopy(n).(*ir.SelectorExpr)
186 return typecheck.Expr(a)
189 n := n.(*ir.SelectorExpr)
190 l := o.cheapExpr(n.X)
194 a := ir.SepCopy(n).(*ir.SelectorExpr)
196 return typecheck.Expr(a)
199 n := n.(*ir.StarExpr)
200 l := o.cheapExpr(n.X)
204 a := ir.SepCopy(n).(*ir.StarExpr)
206 return typecheck.Expr(a)
208 case ir.OINDEX, ir.OINDEXMAP:
209 n := n.(*ir.IndexExpr)
211 if n.X.Type().IsArray() {
216 r := o.cheapExpr(n.Index)
217 if l == n.X && r == n.Index {
220 a := ir.SepCopy(n).(*ir.IndexExpr)
223 return typecheck.Expr(a)
226 base.Fatalf("order.safeExpr %v", n.Op())
227 return nil // not reached
231 // isaddrokay reports whether it is okay to pass n's address to runtime routines.
232 // Taking the address of a variable makes the liveness and optimization analyses
233 // lose track of where the variable's lifetime ends. To avoid hurting the analyses
234 // of ordinary stack variables, those are not 'isaddrokay'. Temporaries are okay,
235 // because we emit explicit VARKILL instructions marking the end of those
236 // temporaries' lifetimes.
237 func isaddrokay(n ir.Node) bool {
238 return ir.IsAddressable(n) && (n.Op() != ir.ONAME || n.(*ir.Name).Class == ir.PEXTERN || ir.IsAutoTmp(n))
241 // addrTemp ensures that n is okay to pass by address to runtime routines.
242 // If the original argument n is not okay, addrTemp creates a tmp, emits
243 // tmp = n, and then returns tmp.
244 // The result of addrTemp MUST be assigned back to n, e.g.
245 // n.Left = o.addrTemp(n.Left)
246 func (o *orderState) addrTemp(n ir.Node) ir.Node {
247 if n.Op() == ir.OLITERAL || n.Op() == ir.ONIL {
248 // TODO: expand this to all static composite literal nodes?
249 n = typecheck.DefaultLit(n, nil)
250 types.CalcSize(n.Type())
251 vstat := readonlystaticname(n.Type())
252 var s staticinit.Schedule
253 s.StaticAssign(vstat, 0, n, n.Type())
255 base.Fatalf("staticassign of const generated code: %+v", n)
257 vstat = typecheck.Expr(vstat).(*ir.Name)
266 // mapKeyTemp prepares n to be a key in a map runtime call and returns n.
267 // It should only be used for map runtime calls which have *_fast* versions.
268 func (o *orderState) mapKeyTemp(t *types.Type, n ir.Node) ir.Node {
269 // Most map calls need to take the address of the key.
270 // Exception: map*_fast* calls. See golang.org/issue/19015.
271 if mapfast(t) == mapslow {
277 // mapKeyReplaceStrConv replaces OBYTES2STR by OBYTES2STRTMP
278 // in n to avoid string allocations for keys in map lookups.
279 // Returns a bool that signals if a modification was made.
283 // x = m[T1{... Tn{..., string(k), ...}]
284 // where k is []byte, T1 to Tn is a nesting of struct and array literals,
285 // the allocation of backing bytes for the string can be avoided
286 // by reusing the []byte backing array. These are special cases
287 // for avoiding allocations when converting byte slices to strings.
288 // It would be nice to handle these generally, but because
289 // []byte keys are not allowed in maps, the use of string(k)
290 // comes up in important cases in practice. See issue 3512.
291 func mapKeyReplaceStrConv(n ir.Node) bool {
295 n := n.(*ir.ConvExpr)
296 n.SetOp(ir.OBYTES2STRTMP)
299 n := n.(*ir.CompLitExpr)
300 for _, elem := range n.List {
301 elem := elem.(*ir.StructKeyExpr)
302 if mapKeyReplaceStrConv(elem.Value) {
307 n := n.(*ir.CompLitExpr)
308 for _, elem := range n.List {
309 if elem.Op() == ir.OKEY {
310 elem = elem.(*ir.KeyExpr).Value
312 if mapKeyReplaceStrConv(elem) {
322 // markTemp returns the top of the temporary variable stack.
323 func (o *orderState) markTemp() ordermarker {
324 return ordermarker(len(o.temp))
327 // popTemp pops temporaries off the stack until reaching the mark,
328 // which must have been returned by markTemp.
329 func (o *orderState) popTemp(mark ordermarker) {
330 for _, n := range o.temp[mark:] {
331 key := n.Type().LongString()
332 o.free[key] = append(o.free[key], n)
334 o.temp = o.temp[:mark]
337 // cleanTempNoPop emits VARKILL instructions to *out
338 // for each temporary above the mark on the temporary stack.
339 // It does not pop the temporaries from the stack.
340 func (o *orderState) cleanTempNoPop(mark ordermarker) []ir.Node {
342 for i := len(o.temp) - 1; i >= int(mark); i-- {
344 out = append(out, typecheck.Stmt(ir.NewUnaryExpr(base.Pos, ir.OVARKILL, n)))
349 // cleanTemp emits VARKILL instructions for each temporary above the
350 // mark on the temporary stack and removes them from the stack.
351 func (o *orderState) cleanTemp(top ordermarker) {
352 o.out = append(o.out, o.cleanTempNoPop(top)...)
356 // stmtList orders each of the statements in the list.
357 func (o *orderState) stmtList(l ir.Nodes) {
360 orderMakeSliceCopy(s[i:])
365 // orderMakeSliceCopy matches the pattern:
366 // m = OMAKESLICE([]T, x); OCOPY(m, s)
367 // and rewrites it to:
368 // m = OMAKESLICECOPY([]T, x, s); nil
369 func orderMakeSliceCopy(s []ir.Node) {
370 if base.Flag.N != 0 || base.Flag.Cfg.Instrumenting {
373 if len(s) < 2 || s[0] == nil || s[0].Op() != ir.OAS || s[1] == nil || s[1].Op() != ir.OCOPY {
377 as := s[0].(*ir.AssignStmt)
378 cp := s[1].(*ir.BinaryExpr)
379 if as.Y == nil || as.Y.Op() != ir.OMAKESLICE || ir.IsBlank(as.X) ||
380 as.X.Op() != ir.ONAME || cp.X.Op() != ir.ONAME || cp.Y.Op() != ir.ONAME ||
381 as.X.Name() != cp.X.Name() || cp.X.Name() == cp.Y.Name() {
382 // The line above this one is correct with the differing equality operators:
383 // we want as.X and cp.X to be the same name,
384 // but we want the initial data to be coming from a different name.
388 mk := as.Y.(*ir.MakeExpr)
389 if mk.Esc() == ir.EscNone || mk.Len == nil || mk.Cap != nil {
392 mk.SetOp(ir.OMAKESLICECOPY)
394 // Set bounded when m = OMAKESLICE([]T, len(s)); OCOPY(m, s)
395 mk.SetBounded(mk.Len.Op() == ir.OLEN && ir.SameSafeExpr(mk.Len.(*ir.UnaryExpr).X, cp.Y))
396 as.Y = typecheck.Expr(mk)
397 s[1] = nil // remove separate copy call
400 // edge inserts coverage instrumentation for libfuzzer.
401 func (o *orderState) edge() {
402 if base.Debug.Libfuzzer == 0 {
406 // Create a new uint8 counter to be allocated in section
407 // __libfuzzer_extra_counters.
408 counter := staticinit.StaticName(types.Types[types.TUINT8])
409 counter.SetLibfuzzerExtraCounter(true)
412 incr := ir.NewAssignOpStmt(base.Pos, ir.OADD, counter, ir.NewInt(1))
416 // orderBlock orders the block of statements in n into a new slice,
417 // and then replaces the old slice in n with the new slice.
418 // free is a map that can be used to obtain temporary variables by type.
419 func orderBlock(n *ir.Nodes, free map[string][]*ir.Name) {
422 mark := order.markTemp()
425 order.cleanTemp(mark)
429 // exprInPlace orders the side effects in *np and
430 // leaves them as the init list of the final *np.
431 // The result of exprInPlace MUST be assigned back to n, e.g.
432 // n.Left = o.exprInPlace(n.Left)
433 func (o *orderState) exprInPlace(n ir.Node) ir.Node {
436 n = order.expr(n, nil)
437 n = ir.InitExpr(order.out, n)
439 // insert new temporaries from order
440 // at head of outer list.
441 o.temp = append(o.temp, order.temp...)
445 // orderStmtInPlace orders the side effects of the single statement *np
446 // and replaces it with the resulting statement list.
447 // The result of orderStmtInPlace MUST be assigned back to n, e.g.
448 // n.Left = orderStmtInPlace(n.Left)
449 // free is a map that can be used to obtain temporary variables by type.
450 func orderStmtInPlace(n ir.Node, free map[string][]*ir.Name) ir.Node {
453 mark := order.markTemp()
455 order.cleanTemp(mark)
456 return ir.NewBlockStmt(src.NoXPos, order.out)
459 // init moves n's init list to o.out.
460 func (o *orderState) init(n ir.Node) {
461 if ir.MayBeShared(n) {
462 // For concurrency safety, don't mutate potentially shared nodes.
463 // First, ensure that no work is required here.
464 if len(n.Init()) > 0 {
465 base.Fatalf("order.init shared node with ninit")
469 o.stmtList(ir.TakeInit(n))
472 // call orders the call expression n.
473 // n.Op is OCALLMETH/OCALLFUNC/OCALLINTER or a builtin like OCOPY.
474 func (o *orderState) call(nn ir.Node) {
475 if len(nn.Init()) > 0 {
476 // Caller should have already called o.init(nn).
477 base.Fatalf("%v with unexpected ninit", nn.Op())
480 // Builtin functions.
481 if nn.Op() != ir.OCALLFUNC && nn.Op() != ir.OCALLMETH && nn.Op() != ir.OCALLINTER {
482 switch n := nn.(type) {
484 base.Fatalf("unexpected call: %+v", n)
486 n.X = o.expr(n.X, nil)
488 n.X = o.expr(n.X, nil)
490 n.X = o.expr(n.X, nil)
491 n.Y = o.expr(n.Y, nil)
493 n.Len = o.expr(n.Len, nil)
494 n.Cap = o.expr(n.Cap, nil)
501 n := nn.(*ir.CallExpr)
502 typecheck.FixVariadicCall(n)
503 n.X = o.expr(n.X, nil)
506 if n.Op() == ir.OCALLINTER {
509 keepAlive := func(arg ir.Node) {
510 // If the argument is really a pointer being converted to uintptr,
511 // arrange for the pointer to be kept alive until the call returns,
512 // by copying it into a temp and marking that temp
513 // still alive when we pop the temp stack.
514 if arg.Op() == ir.OCONVNOP {
515 arg := arg.(*ir.ConvExpr)
516 if arg.X.Type().IsUnsafePtr() {
517 x := o.copyExpr(arg.X)
519 x.SetAddrtaken(true) // ensure SSA keeps the x variable
520 n.KeepAlive = append(n.KeepAlive, x)
525 // Check for "unsafe-uintptr" tag provided by escape analysis.
526 for i, param := range n.X.Type().Params().FieldSlice() {
527 if param.Note == escape.UnsafeUintptrNote || param.Note == escape.UintptrEscapesNote {
528 if arg := n.Args[i]; arg.Op() == ir.OSLICELIT {
529 arg := arg.(*ir.CompLitExpr)
530 for _, elt := range arg.List {
540 // mapAssign appends n to o.out.
541 func (o *orderState) mapAssign(n ir.Node) {
544 base.Fatalf("order.mapAssign %v", n.Op())
547 n := n.(*ir.AssignStmt)
548 if n.X.Op() == ir.OINDEXMAP {
549 n.Y = o.safeMapRHS(n.Y)
551 o.out = append(o.out, n)
553 n := n.(*ir.AssignOpStmt)
554 if n.X.Op() == ir.OINDEXMAP {
555 n.Y = o.safeMapRHS(n.Y)
557 o.out = append(o.out, n)
561 func (o *orderState) safeMapRHS(r ir.Node) ir.Node {
562 // Make sure we evaluate the RHS before starting the map insert.
563 // We need to make sure the RHS won't panic. See issue 22881.
564 if r.Op() == ir.OAPPEND {
565 r := r.(*ir.CallExpr)
567 for i, n := range s {
568 s[i] = o.cheapExpr(n)
572 return o.cheapExpr(r)
575 // stmt orders the statement n, appending to o.out.
576 // Temporaries created during the statement are cleaned
577 // up using VARKILL instructions as possible.
578 func (o *orderState) stmt(n ir.Node) {
588 base.Fatalf("order.stmt %v", n.Op())
590 case ir.OVARKILL, ir.OVARLIVE, ir.OINLMARK:
591 o.out = append(o.out, n)
594 n := n.(*ir.AssignStmt)
596 n.X = o.expr(n.X, nil)
597 n.Y = o.expr(n.Y, n.X)
602 n := n.(*ir.AssignOpStmt)
604 n.X = o.expr(n.X, nil)
605 n.Y = o.expr(n.Y, nil)
607 if base.Flag.Cfg.Instrumenting || n.X.Op() == ir.OINDEXMAP && (n.AsOp == ir.ODIV || n.AsOp == ir.OMOD) {
608 // Rewrite m[k] op= r into m[k] = m[k] op r so
609 // that we can ensure that if op panics
610 // because r is zero, the panic happens before
611 // the map assignment.
612 // DeepCopy is a big hammer here, but safeExpr
613 // makes sure there is nothing too deep being copied.
614 l1 := o.safeExpr(n.X)
615 l2 := ir.DeepCopy(src.NoXPos, l1)
616 if l2.Op() == ir.OINDEXMAP {
617 l2 := l2.(*ir.IndexExpr)
621 r := o.expr(typecheck.Expr(ir.NewBinaryExpr(n.Pos(), n.AsOp, l2, n.Y)), nil)
622 as := typecheck.Stmt(ir.NewAssignStmt(n.Pos(), l1, r))
632 n := n.(*ir.AssignListStmt)
636 o.out = append(o.out, n)
639 // Special: avoid copy of func call n.Right
641 n := n.(*ir.AssignListStmt)
649 // Special: use temporary variables to hold result,
650 // so that runtime can take address of temporary.
651 // No temporary for blank assignment.
653 // OAS2MAPR: make sure key is addressable if needed,
654 // and make sure OINDEXMAP is not copied out.
655 case ir.OAS2DOTTYPE, ir.OAS2RECV, ir.OAS2MAPR:
656 n := n.(*ir.AssignListStmt)
660 switch r := n.Rhs[0]; r.Op() {
662 r := r.(*ir.TypeAssertExpr)
663 r.X = o.expr(r.X, nil)
665 r := r.(*ir.UnaryExpr)
666 r.X = o.expr(r.X, nil)
668 r := r.(*ir.IndexExpr)
669 r.X = o.expr(r.X, nil)
670 r.Index = o.expr(r.Index, nil)
671 // See similar conversion for OINDEXMAP below.
672 _ = mapKeyReplaceStrConv(r.Index)
673 r.Index = o.mapKeyTemp(r.X.Type(), r.Index)
675 base.Fatalf("order.stmt: %v", r.Op())
681 // Special: does not save n onto out.
683 n := n.(*ir.BlockStmt)
686 // Special: n->left is not an expression; save as is.
696 o.out = append(o.out, n)
698 // Special: handle call arguments.
699 case ir.OCALLFUNC, ir.OCALLINTER, ir.OCALLMETH:
700 n := n.(*ir.CallExpr)
703 o.out = append(o.out, n)
706 case ir.OCLOSE, ir.ORECV:
707 n := n.(*ir.UnaryExpr)
709 n.X = o.expr(n.X, nil)
710 o.out = append(o.out, n)
714 n := n.(*ir.BinaryExpr)
716 n.X = o.expr(n.X, nil)
717 n.Y = o.expr(n.Y, nil)
718 o.out = append(o.out, n)
721 case ir.OPRINT, ir.OPRINTN, ir.ORECOVER:
722 n := n.(*ir.CallExpr)
725 o.out = append(o.out, n)
728 // Special: order arguments to inner call but not call itself.
729 case ir.ODEFER, ir.OGO:
730 n := n.(*ir.GoDeferStmt)
734 o.out = append(o.out, n)
738 n := n.(*ir.CallExpr)
740 n.Args[0] = o.expr(n.Args[0], nil)
741 n.Args[1] = o.expr(n.Args[1], nil)
742 n.Args[1] = o.mapKeyTemp(n.Args[0].Type(), n.Args[1])
743 o.out = append(o.out, n)
746 // Clean temporaries from condition evaluation at
747 // beginning of loop body and after for statement.
751 n.Cond = o.exprInPlace(n.Cond)
752 n.Body.Prepend(o.cleanTempNoPop(t)...)
753 orderBlock(&n.Body, o.free)
754 n.Post = orderStmtInPlace(n.Post, o.free)
755 o.out = append(o.out, n)
758 // Clean temporaries from condition at
759 // beginning of both branches.
763 n.Cond = o.exprInPlace(n.Cond)
764 n.Body.Prepend(o.cleanTempNoPop(t)...)
765 n.Else.Prepend(o.cleanTempNoPop(t)...)
767 orderBlock(&n.Body, o.free)
768 orderBlock(&n.Else, o.free)
769 o.out = append(o.out, n)
772 n := n.(*ir.UnaryExpr)
774 n.X = o.expr(n.X, nil)
775 if !n.X.Type().IsEmptyInterface() {
776 base.FatalfAt(n.Pos(), "bad argument to panic: %L", n.X)
778 o.out = append(o.out, n)
782 // n.Right is the expression being ranged over.
783 // order it, and then make a copy if we need one.
784 // We almost always do, to ensure that we don't
785 // see any value changes made during the loop.
786 // Usually the copy is cheap (e.g., array pointer,
787 // chan, slice, string are all tiny).
788 // The exception is ranging over an array value
789 // (not a slice, not a pointer to array),
790 // which must make a copy to avoid seeing updates made during
791 // the range body. Ranging over an array value is uncommon though.
793 // Mark []byte(str) range expression to reuse string backing storage.
794 // It is safe because the storage cannot be mutated.
795 n := n.(*ir.RangeStmt)
796 if n.X.Op() == ir.OSTR2BYTES {
797 n.X.(*ir.ConvExpr).SetOp(ir.OSTR2BYTESTMP)
801 n.X = o.expr(n.X, nil)
804 xt := typecheck.RangeExprType(n.X.Type())
807 base.Fatalf("order.stmt range %v", n.Type())
809 case types.TARRAY, types.TSLICE:
810 if n.Value == nil || ir.IsBlank(n.Value) {
811 // for i := range x will only use x once, to compute len(x).
812 // No need to copy it.
817 case types.TCHAN, types.TSTRING:
818 // chan, string, slice, array ranges use value multiple times.
822 if r.Type().IsString() && r.Type() != types.Types[types.TSTRING] {
823 r = ir.NewConvExpr(base.Pos, ir.OCONV, nil, r)
824 r.SetType(types.Types[types.TSTRING])
825 r = typecheck.Expr(r)
832 // Preserve the body of the map clear pattern so it can
833 // be detected during walk. The loop body will not be used
834 // when optimizing away the range loop to a runtime call.
839 // copy the map value in case it is a map literal.
840 // TODO(rsc): Make tmp = literal expressions reuse tmp.
841 // For maps tmp is just one word so it hardly matters.
845 // n.Prealloc is the temp for the iterator.
846 // MapIterType contains pointers and needs to be zeroed.
847 n.Prealloc = o.newTemp(reflectdata.MapIterType(xt), true)
849 n.Key = o.exprInPlace(n.Key)
850 n.Value = o.exprInPlace(n.Value)
852 orderBlock(&n.Body, o.free)
854 o.out = append(o.out, n)
858 n := n.(*ir.ReturnStmt)
859 o.exprList(n.Results)
860 o.out = append(o.out, n)
862 // Special: clean case temporaries in each block entry.
863 // Select must enter one of its blocks, so there is no
864 // need for a cleaning at the end.
865 // Doubly special: evaluation order for select is stricter
866 // than ordinary expressions. Even something like p.c
867 // has to be hoisted into a temporary, so that it cannot be
868 // reordered after the channel evaluation for a different
869 // case (if p were nil, then the timing of the fault would
872 n := n.(*ir.SelectStmt)
874 for _, ncas := range n.Cases {
878 // Append any new body prologue to ninit.
879 // The next loop will insert ninit into nbody.
880 if len(ncas.Init()) != 0 {
881 base.Fatalf("order select ninit")
888 ir.Dump("select case", r)
889 base.Fatalf("unknown op in select %v", r.Op())
893 r := r.(*ir.AssignListStmt)
894 recv := r.Rhs[0].(*ir.UnaryExpr)
895 recv.X = o.expr(recv.X, nil)
896 if !ir.IsAutoTmp(recv.X) {
897 recv.X = o.copyExpr(recv.X)
899 init := ir.TakeInit(r)
902 do := func(i int, t *types.Type) {
907 // If this is case x := <-ch or case x, y := <-ch, the case has
908 // the ODCL nodes to declare x and y. We want to delay that
909 // declaration (and possible allocation) until inside the case body.
910 // Delete the ODCL nodes here and recreate them inside the body below.
912 if len(init) > 0 && init[0].Op() == ir.ODCL && init[0].(*ir.Decl).X == n {
915 dcl := typecheck.Stmt(ir.NewDecl(base.Pos, ir.ODCL, n.(*ir.Name)))
916 ncas.PtrInit().Append(dcl)
918 tmp := o.newTemp(t, t.HasPointers())
919 as := typecheck.Stmt(ir.NewAssignStmt(base.Pos, n, typecheck.Conv(tmp, n.Type())))
920 ncas.PtrInit().Append(as)
923 do(0, recv.X.Type().Elem())
924 do(1, types.Types[types.TBOOL])
926 ir.DumpList("ninit", r.Init())
927 base.Fatalf("ninit on select recv")
929 orderBlock(ncas.PtrInit(), o.free)
932 r := r.(*ir.SendStmt)
933 if len(r.Init()) != 0 {
934 ir.DumpList("ninit", r.Init())
935 base.Fatalf("ninit on select send")
939 // r->left is c, r->right is x, both are always evaluated.
940 r.Chan = o.expr(r.Chan, nil)
942 if !ir.IsAutoTmp(r.Chan) {
943 r.Chan = o.copyExpr(r.Chan)
945 r.Value = o.expr(r.Value, nil)
946 if !ir.IsAutoTmp(r.Value) {
947 r.Value = o.copyExpr(r.Value)
951 // Now that we have accumulated all the temporaries, clean them.
952 // Also insert any ninit queued during the previous loop.
953 // (The temporary cleaning must follow that ninit work.)
954 for _, cas := range n.Cases {
955 orderBlock(&cas.Body, o.free)
956 cas.Body.Prepend(o.cleanTempNoPop(t)...)
958 // TODO(mdempsky): Is this actually necessary?
959 // walkSelect appears to walk Ninit.
960 cas.Body.Prepend(ir.TakeInit(cas)...)
963 o.out = append(o.out, n)
966 // Special: value being sent is passed as a pointer; make it addressable.
968 n := n.(*ir.SendStmt)
970 n.Chan = o.expr(n.Chan, nil)
971 n.Value = o.expr(n.Value, nil)
972 if base.Flag.Cfg.Instrumenting {
973 // Force copying to the stack so that (chan T)(nil) <- x
974 // is still instrumented as a read of x.
975 n.Value = o.copyExpr(n.Value)
977 n.Value = o.addrTemp(n.Value)
979 o.out = append(o.out, n)
982 // TODO(rsc): Clean temporaries more aggressively.
983 // Note that because walkSwitch will rewrite some of the
984 // switch into a binary search, this is not as easy as it looks.
985 // (If we ran that code here we could invoke order.stmt on
986 // the if-else chain instead.)
987 // For now just clean all the temporaries at the end.
988 // In practice that's fine.
990 n := n.(*ir.SwitchStmt)
991 if base.Debug.Libfuzzer != 0 && !hasDefaultCase(n) {
992 // Add empty "default:" case for instrumentation.
993 n.Cases = append(n.Cases, ir.NewCaseStmt(base.Pos, nil, nil))
997 n.Tag = o.expr(n.Tag, nil)
998 for _, ncas := range n.Cases {
999 o.exprListInPlace(ncas.List)
1000 orderBlock(&ncas.Body, o.free)
1003 o.out = append(o.out, n)
1010 func hasDefaultCase(n *ir.SwitchStmt) bool {
1011 for _, ncas := range n.Cases {
1012 if len(ncas.List) == 0 {
1019 // exprList orders the expression list l into o.
1020 func (o *orderState) exprList(l ir.Nodes) {
1023 s[i] = o.expr(s[i], nil)
1027 // exprListInPlace orders the expression list l but saves
1028 // the side effects on the individual expression ninit lists.
1029 func (o *orderState) exprListInPlace(l ir.Nodes) {
1032 s[i] = o.exprInPlace(s[i])
1036 func (o *orderState) exprNoLHS(n ir.Node) ir.Node {
1037 return o.expr(n, nil)
1040 // expr orders a single expression, appending side
1041 // effects to o.out as needed.
1042 // If this is part of an assignment lhs = *np, lhs is given.
1043 // Otherwise lhs == nil. (When lhs != nil it may be possible
1044 // to avoid copying the result of the expression to a temporary.)
1045 // The result of expr MUST be assigned back to n, e.g.
1046 // n.Left = o.expr(n.Left, lhs)
1047 func (o *orderState) expr(n, lhs ir.Node) ir.Node {
1057 func (o *orderState) expr1(n, lhs ir.Node) ir.Node {
1063 o.edit = o.exprNoLHS // create closure once
1065 ir.EditChildren(n, o.edit)
1068 // Addition of strings turns into a function call.
1069 // Allocate a temporary to hold the strings.
1070 // Fewer than 5 strings use direct runtime helpers.
1072 n := n.(*ir.AddStringExpr)
1075 if len(n.List) > 5 {
1076 t := types.NewArray(types.Types[types.TSTRING], int64(len(n.List)))
1077 n.Prealloc = o.newTemp(t, false)
1080 // Mark string(byteSlice) arguments to reuse byteSlice backing
1081 // buffer during conversion. String concatenation does not
1082 // memorize the strings for later use, so it is safe.
1083 // However, we can do it only if there is at least one non-empty string literal.
1084 // Otherwise if all other arguments are empty strings,
1085 // concatstrings will return the reference to the temp string
1090 for _, n1 := range n.List {
1091 hasbyte = hasbyte || n1.Op() == ir.OBYTES2STR
1092 haslit = haslit || n1.Op() == ir.OLITERAL && len(ir.StringVal(n1)) != 0
1095 if haslit && hasbyte {
1096 for _, n2 := range n.List {
1097 if n2.Op() == ir.OBYTES2STR {
1098 n2 := n2.(*ir.ConvExpr)
1099 n2.SetOp(ir.OBYTES2STRTMP)
1106 n := n.(*ir.IndexExpr)
1107 n.X = o.expr(n.X, nil)
1108 n.Index = o.expr(n.Index, nil)
1112 // Enforce that any []byte slices we are not copying
1113 // can not be changed before the map index by forcing
1114 // the map index to happen immediately following the
1115 // conversions. See copyExpr a few lines below.
1116 needCopy = mapKeyReplaceStrConv(n.Index)
1118 if base.Flag.Cfg.Instrumenting {
1119 // Race detector needs the copy.
1124 // key must be addressable
1125 n.Index = o.mapKeyTemp(n.X.Type(), n.Index)
1127 return o.copyExpr(n)
1131 // concrete type (not interface) argument might need an addressable
1132 // temporary to pass to the runtime conversion routine.
1134 n := n.(*ir.ConvExpr)
1135 n.X = o.expr(n.X, nil)
1136 if n.X.Type().IsInterface() {
1139 if _, needsaddr := convFuncName(n.X.Type(), n.Type()); needsaddr || isStaticCompositeLiteral(n.X) {
1140 // Need a temp if we need to pass the address to the conversion function.
1141 // We also process static composite literal node here, making a named static global
1142 // whose address we can put directly in an interface (see OCONVIFACE case in walk).
1143 n.X = o.addrTemp(n.X)
1148 n := n.(*ir.ConvExpr)
1149 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) {
1150 call := n.X.(*ir.CallExpr)
1151 // When reordering unsafe.Pointer(f()) into a separate
1152 // statement, the conversion and function call must stay
1153 // together. See golang.org/issue/15329.
1156 if lhs == nil || lhs.Op() != ir.ONAME || base.Flag.Cfg.Instrumenting {
1157 return o.copyExpr(n)
1160 n.X = o.expr(n.X, nil)
1164 case ir.OANDAND, ir.OOROR:
1169 // if r { // or !r, for OROR
1174 n := n.(*ir.LogicalExpr)
1175 r := o.newTemp(n.Type(), false)
1177 // Evaluate left-hand side.
1178 lhs := o.expr(n.X, nil)
1179 o.out = append(o.out, typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, lhs)))
1181 // Evaluate right-hand side, save generated code.
1186 rhs := o.expr(n.Y, nil)
1187 o.out = append(o.out, typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, rhs)))
1192 // If left-hand side doesn't cause a short-circuit, issue right-hand side.
1193 nif := ir.NewIfStmt(base.Pos, r, nil, nil)
1194 if n.Op() == ir.OANDAND {
1199 o.out = append(o.out, nif)
1222 // len([]rune(s)) is rewritten to runtime.countrunes(s) later.
1223 conv := n.(*ir.UnaryExpr).X.(*ir.ConvExpr)
1224 conv.X = o.expr(conv.X, nil)
1229 if lhs == nil || lhs.Op() != ir.ONAME || base.Flag.Cfg.Instrumenting {
1230 return o.copyExpr(n)
1235 // Check for append(x, make([]T, y)...) .
1236 n := n.(*ir.CallExpr)
1237 if isAppendOfMake(n) {
1238 n.Args[0] = o.expr(n.Args[0], nil) // order x
1239 mk := n.Args[1].(*ir.MakeExpr)
1240 mk.Len = o.expr(mk.Len, nil) // order y
1245 if lhs == nil || lhs.Op() != ir.ONAME && !ir.SameSafeExpr(lhs, n.Args[0]) {
1246 return o.copyExpr(n)
1250 case ir.OSLICE, ir.OSLICEARR, ir.OSLICESTR, ir.OSLICE3, ir.OSLICE3ARR:
1251 n := n.(*ir.SliceExpr)
1252 n.X = o.expr(n.X, nil)
1253 n.Low = o.cheapExpr(o.expr(n.Low, nil))
1254 n.High = o.cheapExpr(o.expr(n.High, nil))
1255 n.Max = o.cheapExpr(o.expr(n.Max, nil))
1256 if lhs == nil || lhs.Op() != ir.ONAME && !ir.SameSafeExpr(lhs, n.X) {
1257 return o.copyExpr(n)
1262 n := n.(*ir.ClosureExpr)
1263 if n.Transient() && len(n.Func.ClosureVars) > 0 {
1264 n.Prealloc = o.newTemp(typecheck.ClosureType(n), false)
1269 n := n.(*ir.SelectorExpr)
1270 n.X = o.expr(n.X, nil)
1272 t := typecheck.PartialCallType(n)
1273 n.Prealloc = o.newTemp(t, false)
1278 n := n.(*ir.CompLitExpr)
1281 t := types.NewArray(n.Type().Elem(), n.Len)
1282 n.Prealloc = o.newTemp(t, false)
1286 case ir.ODOTTYPE, ir.ODOTTYPE2:
1287 n := n.(*ir.TypeAssertExpr)
1288 n.X = o.expr(n.X, nil)
1289 if !types.IsDirectIface(n.Type()) || base.Flag.Cfg.Instrumenting {
1290 return o.copyExprClear(n)
1295 n := n.(*ir.UnaryExpr)
1296 n.X = o.expr(n.X, nil)
1297 return o.copyExprClear(n)
1299 case ir.OEQ, ir.ONE, ir.OLT, ir.OLE, ir.OGT, ir.OGE:
1300 n := n.(*ir.BinaryExpr)
1301 n.X = o.expr(n.X, nil)
1302 n.Y = o.expr(n.Y, nil)
1307 // Mark string(byteSlice) arguments to reuse byteSlice backing
1308 // buffer during conversion. String comparison does not
1309 // memorize the strings for later use, so it is safe.
1310 if n.X.Op() == ir.OBYTES2STR {
1311 n.X.(*ir.ConvExpr).SetOp(ir.OBYTES2STRTMP)
1313 if n.Y.Op() == ir.OBYTES2STR {
1314 n.Y.(*ir.ConvExpr).SetOp(ir.OBYTES2STRTMP)
1317 case t.IsStruct() || t.IsArray():
1318 // for complex comparisons, we need both args to be
1319 // addressable so we can pass them to the runtime.
1320 n.X = o.addrTemp(n.X)
1321 n.Y = o.addrTemp(n.Y)
1326 // Order map by converting:
1333 // m := map[int]int{}
1337 // Then order the result.
1338 // Without this special case, order would otherwise compute all
1339 // the keys and values before storing any of them to the map.
1341 n := n.(*ir.CompLitExpr)
1343 statics := entries[:0]
1344 var dynamics []*ir.KeyExpr
1345 for _, r := range entries {
1346 r := r.(*ir.KeyExpr)
1348 if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
1349 dynamics = append(dynamics, r)
1353 // Recursively ordering some static entries can change them to dynamic;
1354 // e.g., OCONVIFACE nodes. See #31777.
1355 r = o.expr(r, nil).(*ir.KeyExpr)
1356 if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
1357 dynamics = append(dynamics, r)
1361 statics = append(statics, r)
1365 if len(dynamics) == 0 {
1369 // Emit the creation of the map (with all its static entries).
1370 m := o.newTemp(n.Type(), false)
1371 as := ir.NewAssignStmt(base.Pos, m, n)
1375 // Emit eval+insert of dynamic entries, one at a time.
1376 for _, r := range dynamics {
1377 as := ir.NewAssignStmt(base.Pos, ir.NewIndexExpr(base.Pos, m, r.Key), r.Value)
1378 typecheck.Stmt(as) // Note: this converts the OINDEX to an OINDEXMAP
1384 // No return - type-assertions above. Each case must return for itself.
1387 // as2func orders OAS2FUNC nodes. It creates temporaries to ensure left-to-right assignment.
1388 // The caller should order the right-hand side of the assignment before calling order.as2func.
1392 // tmp1, tmp2, tmp3 = ...
1393 // a, b, a = tmp1, tmp2, tmp3
1394 // This is necessary to ensure left to right assignment order.
1395 func (o *orderState) as2func(n *ir.AssignListStmt) {
1396 results := n.Rhs[0].Type()
1397 as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
1398 for i, nl := range n.Lhs {
1399 if !ir.IsBlank(nl) {
1400 typ := results.Field(i).Type
1401 tmp := o.newTemp(typ, typ.HasPointers())
1403 as.Lhs = append(as.Lhs, nl)
1404 as.Rhs = append(as.Rhs, tmp)
1408 o.out = append(o.out, n)
1409 o.stmt(typecheck.Stmt(as))
1412 // as2ok orders OAS2XXX with ok.
1413 // Just like as2func, this also adds temporaries to ensure left-to-right assignment.
1414 func (o *orderState) as2ok(n *ir.AssignListStmt) {
1415 as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
1417 do := func(i int, typ *types.Type) {
1418 if nl := n.Lhs[i]; !ir.IsBlank(nl) {
1419 var tmp ir.Node = o.newTemp(typ, typ.HasPointers())
1421 as.Lhs = append(as.Lhs, nl)
1423 // The "ok" result is an untyped boolean according to the Go
1424 // spec. We need to explicitly convert it to the LHS type in
1425 // case the latter is a defined boolean type (#8475).
1426 tmp = typecheck.Conv(tmp, nl.Type())
1428 as.Rhs = append(as.Rhs, tmp)
1432 do(0, n.Rhs[0].Type())
1433 do(1, types.Types[types.TBOOL])
1435 o.out = append(o.out, n)
1436 o.stmt(typecheck.Stmt(as))