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 __sancov_cntrs
450 counter := staticinit.StaticName(types.Types[types.TUINT8])
451 counter.SetLibfuzzer8BitCounter(true)
452 // As well as setting SetLibfuzzer8BitCounter, we preemptively set the
453 // symbol type to SLIBFUZZER_8BIT_COUNTER so that the race detector
454 // instrumentation pass (which does not have access to the flags set by
455 // SetLibfuzzer8BitCounter) knows to ignore them. This information is
456 // lost by the time it reaches the compile step, so SetLibfuzzer8BitCounter
457 // is still necessary.
458 counter.Linksym().Type = objabi.SLIBFUZZER_8BIT_COUNTER
460 // We guarantee that the counter never becomes zero again once it has been
461 // incremented once. This implementation follows the NeverZero optimization
462 // presented by the paper:
463 // "AFL++: Combining Incremental Steps of Fuzzing Research"
464 // The NeverZero policy avoids the overflow to 0 by setting the counter to one
465 // after it reaches 255 and so, if an edge is executed at least one time, the entry is
467 // Another policy presented in the paper is the Saturated Counters policy which
468 // freezes the counter when it reaches the value of 255. However, a range
469 // of experiments showed that that decreases overall performance.
470 o.append(ir.NewIfStmt(base.Pos,
471 ir.NewBinaryExpr(base.Pos, ir.OEQ, counter, ir.NewInt(0xff)),
472 []ir.Node{ir.NewAssignStmt(base.Pos, counter, ir.NewInt(1))},
473 []ir.Node{ir.NewAssignOpStmt(base.Pos, ir.OADD, counter, ir.NewInt(1))}))
476 // orderBlock orders the block of statements in n into a new slice,
477 // and then replaces the old slice in n with the new slice.
478 // free is a map that can be used to obtain temporary variables by type.
479 func orderBlock(n *ir.Nodes, free map[string][]*ir.Name) {
482 mark := order.markTemp()
485 order.cleanTemp(mark)
489 // exprInPlace orders the side effects in *np and
490 // leaves them as the init list of the final *np.
491 // The result of exprInPlace MUST be assigned back to n, e.g.
493 // n.Left = o.exprInPlace(n.Left)
494 func (o *orderState) exprInPlace(n ir.Node) ir.Node {
497 n = order.expr(n, nil)
498 n = ir.InitExpr(order.out, n)
500 // insert new temporaries from order
501 // at head of outer list.
502 o.temp = append(o.temp, order.temp...)
506 // orderStmtInPlace orders the side effects of the single statement *np
507 // and replaces it with the resulting statement list.
508 // The result of orderStmtInPlace MUST be assigned back to n, e.g.
510 // n.Left = orderStmtInPlace(n.Left)
512 // free is a map that can be used to obtain temporary variables by type.
513 func orderStmtInPlace(n ir.Node, free map[string][]*ir.Name) ir.Node {
516 mark := order.markTemp()
518 order.cleanTemp(mark)
519 return ir.NewBlockStmt(src.NoXPos, order.out)
522 // init moves n's init list to o.out.
523 func (o *orderState) init(n ir.Node) {
524 if ir.MayBeShared(n) {
525 // For concurrency safety, don't mutate potentially shared nodes.
526 // First, ensure that no work is required here.
527 if len(n.Init()) > 0 {
528 base.Fatalf("order.init shared node with ninit")
532 o.stmtList(ir.TakeInit(n))
535 // call orders the call expression n.
536 // n.Op is OCALLFUNC/OCALLINTER or a builtin like OCOPY.
537 func (o *orderState) call(nn ir.Node) {
538 if len(nn.Init()) > 0 {
539 // Caller should have already called o.init(nn).
540 base.Fatalf("%v with unexpected ninit", nn.Op())
542 if nn.Op() == ir.OCALLMETH {
543 base.FatalfAt(nn.Pos(), "OCALLMETH missed by typecheck")
546 // Builtin functions.
547 if nn.Op() != ir.OCALLFUNC && nn.Op() != ir.OCALLINTER {
548 switch n := nn.(type) {
550 base.Fatalf("unexpected call: %+v", n)
552 n.X = o.expr(n.X, nil)
554 n.X = o.expr(n.X, nil)
556 n.X = o.expr(n.X, nil)
557 n.Y = o.expr(n.Y, nil)
559 n.Len = o.expr(n.Len, nil)
560 n.Cap = o.expr(n.Cap, nil)
567 n := nn.(*ir.CallExpr)
568 typecheck.FixVariadicCall(n)
570 if isFuncPCIntrinsic(n) && isIfaceOfFunc(n.Args[0]) {
571 // For internal/abi.FuncPCABIxxx(fn), if fn is a defined function,
572 // do not introduce temporaries here, so it is easier to rewrite it
573 // to symbol address reference later in walk.
577 n.X = o.expr(n.X, nil)
581 // mapAssign appends n to o.out.
582 func (o *orderState) mapAssign(n ir.Node) {
585 base.Fatalf("order.mapAssign %v", n.Op())
588 n := n.(*ir.AssignStmt)
589 if n.X.Op() == ir.OINDEXMAP {
590 n.Y = o.safeMapRHS(n.Y)
592 o.out = append(o.out, n)
594 n := n.(*ir.AssignOpStmt)
595 if n.X.Op() == ir.OINDEXMAP {
596 n.Y = o.safeMapRHS(n.Y)
598 o.out = append(o.out, n)
602 func (o *orderState) safeMapRHS(r ir.Node) ir.Node {
603 // Make sure we evaluate the RHS before starting the map insert.
604 // We need to make sure the RHS won't panic. See issue 22881.
605 if r.Op() == ir.OAPPEND {
606 r := r.(*ir.CallExpr)
608 for i, n := range s {
609 s[i] = o.cheapExpr(n)
613 return o.cheapExpr(r)
616 // stmt orders the statement n, appending to o.out.
617 // Temporaries created during the statement are cleaned
618 // up using VARKILL instructions as possible.
619 func (o *orderState) stmt(n ir.Node) {
629 base.Fatalf("order.stmt %v", n.Op())
631 case ir.OVARKILL, ir.OVARLIVE, ir.OINLMARK:
632 o.out = append(o.out, n)
635 n := n.(*ir.AssignStmt)
637 n.X = o.expr(n.X, nil)
638 n.Y = o.expr(n.Y, n.X)
643 n := n.(*ir.AssignOpStmt)
645 n.X = o.expr(n.X, nil)
646 n.Y = o.expr(n.Y, nil)
648 if base.Flag.Cfg.Instrumenting || n.X.Op() == ir.OINDEXMAP && (n.AsOp == ir.ODIV || n.AsOp == ir.OMOD) {
649 // Rewrite m[k] op= r into m[k] = m[k] op r so
650 // that we can ensure that if op panics
651 // because r is zero, the panic happens before
652 // the map assignment.
653 // DeepCopy is a big hammer here, but safeExpr
654 // makes sure there is nothing too deep being copied.
655 l1 := o.safeExpr(n.X)
656 l2 := ir.DeepCopy(src.NoXPos, l1)
657 if l2.Op() == ir.OINDEXMAP {
658 l2 := l2.(*ir.IndexExpr)
662 r := o.expr(typecheck.Expr(ir.NewBinaryExpr(n.Pos(), n.AsOp, l2, n.Y)), nil)
663 as := typecheck.Stmt(ir.NewAssignStmt(n.Pos(), l1, r))
673 n := n.(*ir.AssignListStmt)
677 o.out = append(o.out, n)
680 // Special: avoid copy of func call n.Right
682 n := n.(*ir.AssignListStmt)
687 if ic, ok := call.(*ir.InlinedCallExpr); ok {
691 n.Rhs = ic.ReturnVars
694 o.out = append(o.out, n)
701 // Special: use temporary variables to hold result,
702 // so that runtime can take address of temporary.
703 // No temporary for blank assignment.
705 // OAS2MAPR: make sure key is addressable if needed,
706 // and make sure OINDEXMAP is not copied out.
707 case ir.OAS2DOTTYPE, ir.OAS2RECV, ir.OAS2MAPR:
708 n := n.(*ir.AssignListStmt)
712 switch r := n.Rhs[0]; r.Op() {
714 r := r.(*ir.TypeAssertExpr)
715 r.X = o.expr(r.X, nil)
716 case ir.ODYNAMICDOTTYPE2:
717 r := r.(*ir.DynamicTypeAssertExpr)
718 r.X = o.expr(r.X, nil)
719 r.RType = o.expr(r.RType, nil)
720 r.ITab = o.expr(r.ITab, nil)
722 r := r.(*ir.UnaryExpr)
723 r.X = o.expr(r.X, nil)
725 r := r.(*ir.IndexExpr)
726 r.X = o.expr(r.X, nil)
727 r.Index = o.expr(r.Index, nil)
728 // See similar conversion for OINDEXMAP below.
729 _ = mapKeyReplaceStrConv(r.Index)
730 r.Index = o.mapKeyTemp(r.X.Type(), r.Index)
732 base.Fatalf("order.stmt: %v", r.Op())
738 // Special: does not save n onto out.
740 n := n.(*ir.BlockStmt)
743 // Special: n->left is not an expression; save as is.
753 o.out = append(o.out, n)
755 // Special: handle call arguments.
756 case ir.OCALLFUNC, ir.OCALLINTER:
757 n := n.(*ir.CallExpr)
760 o.out = append(o.out, n)
764 n := n.(*ir.InlinedCallExpr)
767 // discard results; double-check for no side effects
768 for _, result := range n.ReturnVars {
769 if staticinit.AnySideEffects(result) {
770 base.FatalfAt(result.Pos(), "inlined call result has side effects: %v", result)
774 case ir.OCHECKNIL, ir.OCLOSE, ir.OPANIC, ir.ORECV:
775 n := n.(*ir.UnaryExpr)
777 n.X = o.expr(n.X, nil)
778 o.out = append(o.out, n)
782 n := n.(*ir.BinaryExpr)
784 n.X = o.expr(n.X, nil)
785 n.Y = o.expr(n.Y, nil)
786 o.out = append(o.out, n)
789 case ir.OPRINT, ir.OPRINTN, ir.ORECOVERFP:
790 n := n.(*ir.CallExpr)
793 o.out = append(o.out, n)
796 // Special: order arguments to inner call but not call itself.
797 case ir.ODEFER, ir.OGO:
798 n := n.(*ir.GoDeferStmt)
802 o.out = append(o.out, n)
806 n := n.(*ir.CallExpr)
808 n.Args[0] = o.expr(n.Args[0], nil)
809 n.Args[1] = o.expr(n.Args[1], nil)
810 n.Args[1] = o.mapKeyTemp(n.Args[0].Type(), n.Args[1])
811 o.out = append(o.out, n)
814 // Clean temporaries from condition evaluation at
815 // beginning of loop body and after for statement.
819 n.Cond = o.exprInPlace(n.Cond)
820 n.Body.Prepend(o.cleanTempNoPop(t)...)
821 orderBlock(&n.Body, o.free)
822 n.Post = orderStmtInPlace(n.Post, o.free)
823 o.out = append(o.out, n)
826 // Clean temporaries from condition at
827 // beginning of both branches.
831 n.Cond = o.exprInPlace(n.Cond)
832 n.Body.Prepend(o.cleanTempNoPop(t)...)
833 n.Else.Prepend(o.cleanTempNoPop(t)...)
835 orderBlock(&n.Body, o.free)
836 orderBlock(&n.Else, o.free)
837 o.out = append(o.out, n)
840 // n.Right is the expression being ranged over.
841 // order it, and then make a copy if we need one.
842 // We almost always do, to ensure that we don't
843 // see any value changes made during the loop.
844 // Usually the copy is cheap (e.g., array pointer,
845 // chan, slice, string are all tiny).
846 // The exception is ranging over an array value
847 // (not a slice, not a pointer to array),
848 // which must make a copy to avoid seeing updates made during
849 // the range body. Ranging over an array value is uncommon though.
851 // Mark []byte(str) range expression to reuse string backing storage.
852 // It is safe because the storage cannot be mutated.
853 n := n.(*ir.RangeStmt)
854 if n.X.Op() == ir.OSTR2BYTES {
855 n.X.(*ir.ConvExpr).SetOp(ir.OSTR2BYTESTMP)
859 n.X = o.expr(n.X, nil)
862 xt := typecheck.RangeExprType(n.X.Type())
865 base.Fatalf("order.stmt range %v", n.Type())
867 case types.TARRAY, types.TSLICE:
868 if n.Value == nil || ir.IsBlank(n.Value) {
869 // for i := range x will only use x once, to compute len(x).
870 // No need to copy it.
875 case types.TCHAN, types.TSTRING:
876 // chan, string, slice, array ranges use value multiple times.
880 if r.Type().IsString() && r.Type() != types.Types[types.TSTRING] {
881 r = ir.NewConvExpr(base.Pos, ir.OCONV, nil, r)
882 r.SetType(types.Types[types.TSTRING])
883 r = typecheck.Expr(r)
890 // Preserve the body of the map clear pattern so it can
891 // be detected during walk. The loop body will not be used
892 // when optimizing away the range loop to a runtime call.
897 // copy the map value in case it is a map literal.
898 // TODO(rsc): Make tmp = literal expressions reuse tmp.
899 // For maps tmp is just one word so it hardly matters.
903 // n.Prealloc is the temp for the iterator.
904 // MapIterType contains pointers and needs to be zeroed.
905 n.Prealloc = o.newTemp(reflectdata.MapIterType(xt), true)
907 n.Key = o.exprInPlace(n.Key)
908 n.Value = o.exprInPlace(n.Value)
910 orderBlock(&n.Body, o.free)
912 o.out = append(o.out, n)
916 n := n.(*ir.ReturnStmt)
917 o.exprList(n.Results)
918 o.out = append(o.out, n)
920 // Special: clean case temporaries in each block entry.
921 // Select must enter one of its blocks, so there is no
922 // need for a cleaning at the end.
923 // Doubly special: evaluation order for select is stricter
924 // than ordinary expressions. Even something like p.c
925 // has to be hoisted into a temporary, so that it cannot be
926 // reordered after the channel evaluation for a different
927 // case (if p were nil, then the timing of the fault would
930 n := n.(*ir.SelectStmt)
932 for _, ncas := range n.Cases {
936 // Append any new body prologue to ninit.
937 // The next loop will insert ninit into nbody.
938 if len(ncas.Init()) != 0 {
939 base.Fatalf("order select ninit")
946 ir.Dump("select case", r)
947 base.Fatalf("unknown op in select %v", r.Op())
951 r := r.(*ir.AssignListStmt)
952 recv := r.Rhs[0].(*ir.UnaryExpr)
953 recv.X = o.expr(recv.X, nil)
954 if !ir.IsAutoTmp(recv.X) {
955 recv.X = o.copyExpr(recv.X)
957 init := ir.TakeInit(r)
960 do := func(i int, t *types.Type) {
965 // If this is case x := <-ch or case x, y := <-ch, the case has
966 // the ODCL nodes to declare x and y. We want to delay that
967 // declaration (and possible allocation) until inside the case body.
968 // Delete the ODCL nodes here and recreate them inside the body below.
970 if len(init) > 0 && init[0].Op() == ir.ODCL && init[0].(*ir.Decl).X == n {
973 // iimport may have added a default initialization assignment,
974 // due to how it handles ODCL statements.
975 if len(init) > 0 && init[0].Op() == ir.OAS && init[0].(*ir.AssignStmt).X == n {
979 dcl := typecheck.Stmt(ir.NewDecl(base.Pos, ir.ODCL, n.(*ir.Name)))
980 ncas.PtrInit().Append(dcl)
982 tmp := o.newTemp(t, t.HasPointers())
983 as := typecheck.Stmt(ir.NewAssignStmt(base.Pos, n, typecheck.Conv(tmp, n.Type())))
984 ncas.PtrInit().Append(as)
987 do(0, recv.X.Type().Elem())
988 do(1, types.Types[types.TBOOL])
990 ir.DumpList("ninit", init)
991 base.Fatalf("ninit on select recv")
993 orderBlock(ncas.PtrInit(), o.free)
996 r := r.(*ir.SendStmt)
997 if len(r.Init()) != 0 {
998 ir.DumpList("ninit", r.Init())
999 base.Fatalf("ninit on select send")
1003 // r->left is c, r->right is x, both are always evaluated.
1004 r.Chan = o.expr(r.Chan, nil)
1006 if !ir.IsAutoTmp(r.Chan) {
1007 r.Chan = o.copyExpr(r.Chan)
1009 r.Value = o.expr(r.Value, nil)
1010 if !ir.IsAutoTmp(r.Value) {
1011 r.Value = o.copyExpr(r.Value)
1015 // Now that we have accumulated all the temporaries, clean them.
1016 // Also insert any ninit queued during the previous loop.
1017 // (The temporary cleaning must follow that ninit work.)
1018 for _, cas := range n.Cases {
1019 orderBlock(&cas.Body, o.free)
1020 cas.Body.Prepend(o.cleanTempNoPop(t)...)
1022 // TODO(mdempsky): Is this actually necessary?
1023 // walkSelect appears to walk Ninit.
1024 cas.Body.Prepend(ir.TakeInit(cas)...)
1027 o.out = append(o.out, n)
1030 // Special: value being sent is passed as a pointer; make it addressable.
1032 n := n.(*ir.SendStmt)
1034 n.Chan = o.expr(n.Chan, nil)
1035 n.Value = o.expr(n.Value, nil)
1036 if base.Flag.Cfg.Instrumenting {
1037 // Force copying to the stack so that (chan T)(nil) <- x
1038 // is still instrumented as a read of x.
1039 n.Value = o.copyExpr(n.Value)
1041 n.Value = o.addrTemp(n.Value)
1043 o.out = append(o.out, n)
1046 // TODO(rsc): Clean temporaries more aggressively.
1047 // Note that because walkSwitch will rewrite some of the
1048 // switch into a binary search, this is not as easy as it looks.
1049 // (If we ran that code here we could invoke order.stmt on
1050 // the if-else chain instead.)
1051 // For now just clean all the temporaries at the end.
1052 // In practice that's fine.
1054 n := n.(*ir.SwitchStmt)
1055 if base.Debug.Libfuzzer != 0 && !hasDefaultCase(n) {
1056 // Add empty "default:" case for instrumentation.
1057 n.Cases = append(n.Cases, ir.NewCaseStmt(base.Pos, nil, nil))
1061 n.Tag = o.expr(n.Tag, nil)
1062 for _, ncas := range n.Cases {
1063 o.exprListInPlace(ncas.List)
1064 orderBlock(&ncas.Body, o.free)
1067 o.out = append(o.out, n)
1074 func hasDefaultCase(n *ir.SwitchStmt) bool {
1075 for _, ncas := range n.Cases {
1076 if len(ncas.List) == 0 {
1083 // exprList orders the expression list l into o.
1084 func (o *orderState) exprList(l ir.Nodes) {
1087 s[i] = o.expr(s[i], nil)
1091 // exprListInPlace orders the expression list l but saves
1092 // the side effects on the individual expression ninit lists.
1093 func (o *orderState) exprListInPlace(l ir.Nodes) {
1096 s[i] = o.exprInPlace(s[i])
1100 func (o *orderState) exprNoLHS(n ir.Node) ir.Node {
1101 return o.expr(n, nil)
1104 // expr orders a single expression, appending side
1105 // effects to o.out as needed.
1106 // If this is part of an assignment lhs = *np, lhs is given.
1107 // Otherwise lhs == nil. (When lhs != nil it may be possible
1108 // to avoid copying the result of the expression to a temporary.)
1109 // The result of expr MUST be assigned back to n, e.g.
1111 // n.Left = o.expr(n.Left, lhs)
1112 func (o *orderState) expr(n, lhs ir.Node) ir.Node {
1122 func (o *orderState) expr1(n, lhs ir.Node) ir.Node {
1128 o.edit = o.exprNoLHS // create closure once
1130 ir.EditChildren(n, o.edit)
1133 // Addition of strings turns into a function call.
1134 // Allocate a temporary to hold the strings.
1135 // Fewer than 5 strings use direct runtime helpers.
1137 n := n.(*ir.AddStringExpr)
1140 if len(n.List) > 5 {
1141 t := types.NewArray(types.Types[types.TSTRING], int64(len(n.List)))
1142 n.Prealloc = o.newTemp(t, false)
1145 // Mark string(byteSlice) arguments to reuse byteSlice backing
1146 // buffer during conversion. String concatenation does not
1147 // memorize the strings for later use, so it is safe.
1148 // However, we can do it only if there is at least one non-empty string literal.
1149 // Otherwise if all other arguments are empty strings,
1150 // concatstrings will return the reference to the temp string
1155 for _, n1 := range n.List {
1156 hasbyte = hasbyte || n1.Op() == ir.OBYTES2STR
1157 haslit = haslit || n1.Op() == ir.OLITERAL && len(ir.StringVal(n1)) != 0
1160 if haslit && hasbyte {
1161 for _, n2 := range n.List {
1162 if n2.Op() == ir.OBYTES2STR {
1163 n2 := n2.(*ir.ConvExpr)
1164 n2.SetOp(ir.OBYTES2STRTMP)
1171 n := n.(*ir.IndexExpr)
1172 n.X = o.expr(n.X, nil)
1173 n.Index = o.expr(n.Index, nil)
1177 // Enforce that any []byte slices we are not copying
1178 // can not be changed before the map index by forcing
1179 // the map index to happen immediately following the
1180 // conversions. See copyExpr a few lines below.
1181 needCopy = mapKeyReplaceStrConv(n.Index)
1183 if base.Flag.Cfg.Instrumenting {
1184 // Race detector needs the copy.
1189 // key must be addressable
1190 n.Index = o.mapKeyTemp(n.X.Type(), n.Index)
1192 return o.copyExpr(n)
1196 // concrete type (not interface) argument might need an addressable
1197 // temporary to pass to the runtime conversion routine.
1198 case ir.OCONVIFACE, ir.OCONVIDATA:
1199 n := n.(*ir.ConvExpr)
1200 n.X = o.expr(n.X, nil)
1201 if n.X.Type().IsInterface() {
1204 if _, _, needsaddr := dataWordFuncName(n.X.Type()); needsaddr || isStaticCompositeLiteral(n.X) {
1205 // Need a temp if we need to pass the address to the conversion function.
1206 // We also process static composite literal node here, making a named static global
1207 // whose address we can put directly in an interface (see OCONVIFACE/OCONVIDATA case in walk).
1208 n.X = o.addrTemp(n.X)
1213 n := n.(*ir.ConvExpr)
1214 if n.X.Op() == ir.OCALLMETH {
1215 base.FatalfAt(n.X.Pos(), "OCALLMETH missed by typecheck")
1217 if n.Type().IsKind(types.TUNSAFEPTR) && n.X.Type().IsKind(types.TUINTPTR) && (n.X.Op() == ir.OCALLFUNC || n.X.Op() == ir.OCALLINTER) {
1218 call := n.X.(*ir.CallExpr)
1219 // When reordering unsafe.Pointer(f()) into a separate
1220 // statement, the conversion and function call must stay
1221 // together. See golang.org/issue/15329.
1224 if lhs == nil || lhs.Op() != ir.ONAME || base.Flag.Cfg.Instrumenting {
1225 return o.copyExpr(n)
1228 n.X = o.expr(n.X, nil)
1232 case ir.OANDAND, ir.OOROR:
1237 // if r { // or !r, for OROR
1242 n := n.(*ir.LogicalExpr)
1243 r := o.newTemp(n.Type(), false)
1245 // Evaluate left-hand side.
1246 lhs := o.expr(n.X, nil)
1247 o.out = append(o.out, typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, lhs)))
1249 // Evaluate right-hand side, save generated code.
1254 rhs := o.expr(n.Y, nil)
1255 o.out = append(o.out, typecheck.Stmt(ir.NewAssignStmt(base.Pos, r, rhs)))
1260 // If left-hand side doesn't cause a short-circuit, issue right-hand side.
1261 nif := ir.NewIfStmt(base.Pos, r, nil, nil)
1262 if n.Op() == ir.OANDAND {
1267 o.out = append(o.out, nif)
1271 base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
1272 panic("unreachable")
1293 // len([]rune(s)) is rewritten to runtime.countrunes(s) later.
1294 conv := n.(*ir.UnaryExpr).X.(*ir.ConvExpr)
1295 conv.X = o.expr(conv.X, nil)
1300 if lhs == nil || lhs.Op() != ir.ONAME || base.Flag.Cfg.Instrumenting {
1301 return o.copyExpr(n)
1306 n := n.(*ir.InlinedCallExpr)
1308 return n.SingleResult()
1311 // Check for append(x, make([]T, y)...) .
1312 n := n.(*ir.CallExpr)
1313 if isAppendOfMake(n) {
1314 n.Args[0] = o.expr(n.Args[0], nil) // order x
1315 mk := n.Args[1].(*ir.MakeExpr)
1316 mk.Len = o.expr(mk.Len, nil) // order y
1321 if lhs == nil || lhs.Op() != ir.ONAME && !ir.SameSafeExpr(lhs, n.Args[0]) {
1322 return o.copyExpr(n)
1326 case ir.OSLICE, ir.OSLICEARR, ir.OSLICESTR, ir.OSLICE3, ir.OSLICE3ARR:
1327 n := n.(*ir.SliceExpr)
1328 n.X = o.expr(n.X, nil)
1329 n.Low = o.cheapExpr(o.expr(n.Low, nil))
1330 n.High = o.cheapExpr(o.expr(n.High, nil))
1331 n.Max = o.cheapExpr(o.expr(n.Max, nil))
1332 if lhs == nil || lhs.Op() != ir.ONAME && !ir.SameSafeExpr(lhs, n.X) {
1333 return o.copyExpr(n)
1338 n := n.(*ir.ClosureExpr)
1339 if n.Transient() && len(n.Func.ClosureVars) > 0 {
1340 n.Prealloc = o.newTemp(typecheck.ClosureType(n), false)
1345 n := n.(*ir.SelectorExpr)
1346 n.X = o.expr(n.X, nil)
1348 t := typecheck.MethodValueType(n)
1349 n.Prealloc = o.newTemp(t, false)
1354 n := n.(*ir.CompLitExpr)
1357 t := types.NewArray(n.Type().Elem(), n.Len)
1358 n.Prealloc = o.newTemp(t, false)
1362 case ir.ODOTTYPE, ir.ODOTTYPE2:
1363 n := n.(*ir.TypeAssertExpr)
1364 n.X = o.expr(n.X, nil)
1365 if !types.IsDirectIface(n.Type()) || base.Flag.Cfg.Instrumenting {
1366 return o.copyExprClear(n)
1371 n := n.(*ir.UnaryExpr)
1372 n.X = o.expr(n.X, nil)
1373 return o.copyExprClear(n)
1375 case ir.OEQ, ir.ONE, ir.OLT, ir.OLE, ir.OGT, ir.OGE:
1376 n := n.(*ir.BinaryExpr)
1377 n.X = o.expr(n.X, nil)
1378 n.Y = o.expr(n.Y, nil)
1383 // Mark string(byteSlice) arguments to reuse byteSlice backing
1384 // buffer during conversion. String comparison does not
1385 // memorize the strings for later use, so it is safe.
1386 if n.X.Op() == ir.OBYTES2STR {
1387 n.X.(*ir.ConvExpr).SetOp(ir.OBYTES2STRTMP)
1389 if n.Y.Op() == ir.OBYTES2STR {
1390 n.Y.(*ir.ConvExpr).SetOp(ir.OBYTES2STRTMP)
1393 case t.IsStruct() || t.IsArray():
1394 // for complex comparisons, we need both args to be
1395 // addressable so we can pass them to the runtime.
1396 n.X = o.addrTemp(n.X)
1397 n.Y = o.addrTemp(n.Y)
1402 // Order map by converting:
1409 // m := map[int]int{}
1413 // Then order the result.
1414 // Without this special case, order would otherwise compute all
1415 // the keys and values before storing any of them to the map.
1417 n := n.(*ir.CompLitExpr)
1419 statics := entries[:0]
1420 var dynamics []*ir.KeyExpr
1421 for _, r := range entries {
1422 r := r.(*ir.KeyExpr)
1424 if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
1425 dynamics = append(dynamics, r)
1429 // Recursively ordering some static entries can change them to dynamic;
1430 // e.g., OCONVIFACE nodes. See #31777.
1431 r = o.expr(r, nil).(*ir.KeyExpr)
1432 if !isStaticCompositeLiteral(r.Key) || !isStaticCompositeLiteral(r.Value) {
1433 dynamics = append(dynamics, r)
1437 statics = append(statics, r)
1441 if len(dynamics) == 0 {
1445 // Emit the creation of the map (with all its static entries).
1446 m := o.newTemp(n.Type(), false)
1447 as := ir.NewAssignStmt(base.Pos, m, n)
1451 // Emit eval+insert of dynamic entries, one at a time.
1452 for _, r := range dynamics {
1453 lhs := typecheck.AssignExpr(ir.NewIndexExpr(base.Pos, m, r.Key)).(*ir.IndexExpr)
1454 base.AssertfAt(lhs.Op() == ir.OINDEXMAP, lhs.Pos(), "want OINDEXMAP, have %+v", lhs)
1457 as := ir.NewAssignStmt(base.Pos, lhs, r.Value)
1462 // Remember that we issued these assignments so we can include that count
1463 // in the map alloc hint.
1464 // We're assuming here that all the keys in the map literal are distinct.
1465 // If any are equal, this will be an overcount. Probably not worth accounting
1466 // for that, as equal keys in map literals are rare, and at worst we waste
1468 n.Len += int64(len(dynamics))
1473 // No return - type-assertions above. Each case must return for itself.
1476 // as2func orders OAS2FUNC nodes. It creates temporaries to ensure left-to-right assignment.
1477 // The caller should order the right-hand side of the assignment before calling order.as2func.
1484 // tmp1, tmp2, tmp3 = ...
1485 // a, b, a = tmp1, tmp2, tmp3
1487 // This is necessary to ensure left to right assignment order.
1488 func (o *orderState) as2func(n *ir.AssignListStmt) {
1489 results := n.Rhs[0].Type()
1490 as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
1491 for i, nl := range n.Lhs {
1492 if !ir.IsBlank(nl) {
1493 typ := results.Field(i).Type
1494 tmp := o.newTemp(typ, typ.HasPointers())
1496 as.Lhs = append(as.Lhs, nl)
1497 as.Rhs = append(as.Rhs, tmp)
1501 o.out = append(o.out, n)
1502 o.stmt(typecheck.Stmt(as))
1505 // as2ok orders OAS2XXX with ok.
1506 // Just like as2func, this also adds temporaries to ensure left-to-right assignment.
1507 func (o *orderState) as2ok(n *ir.AssignListStmt) {
1508 as := ir.NewAssignListStmt(n.Pos(), ir.OAS2, nil, nil)
1510 do := func(i int, typ *types.Type) {
1511 if nl := n.Lhs[i]; !ir.IsBlank(nl) {
1512 var tmp ir.Node = o.newTemp(typ, typ.HasPointers())
1514 as.Lhs = append(as.Lhs, nl)
1516 // The "ok" result is an untyped boolean according to the Go
1517 // spec. We need to explicitly convert it to the LHS type in
1518 // case the latter is a defined boolean type (#8475).
1519 tmp = typecheck.Conv(tmp, nl.Type())
1521 as.Rhs = append(as.Rhs, tmp)
1525 do(0, n.Rhs[0].Type())
1526 do(1, types.Types[types.TBOOL])
1528 o.out = append(o.out, n)
1529 o.stmt(typecheck.Stmt(as))
1532 // isFuncPCIntrinsic returns whether n is a direct call of internal/abi.FuncPCABIxxx functions.
1533 func isFuncPCIntrinsic(n *ir.CallExpr) bool {
1534 if n.Op() != ir.OCALLFUNC || n.X.Op() != ir.ONAME {
1537 fn := n.X.(*ir.Name).Sym()
1538 return (fn.Name == "FuncPCABI0" || fn.Name == "FuncPCABIInternal") &&
1539 (fn.Pkg.Path == "internal/abi" || fn.Pkg == types.LocalPkg && base.Ctxt.Pkgpath == "internal/abi")
1542 // isIfaceOfFunc returns whether n is an interface conversion from a direct reference of a func.
1543 func isIfaceOfFunc(n ir.Node) bool {
1544 return n.Op() == ir.OCONVIFACE && n.(*ir.ConvExpr).X.Op() == ir.ONAME && n.(*ir.ConvExpr).X.(*ir.Name).Class == ir.PFUNC