1 // Copyright 2011 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.
5 // The inlining facility makes 2 passes: first CanInline determines which
6 // functions are suitable for inlining, and for those that are it
7 // saves a copy of the body. Then InlineCalls walks each function body to
8 // expand calls to inlinable functions.
10 // The Debug.l flag controls the aggressiveness. Note that main() swaps level 0 and 1,
11 // making 1 the default and -l disable. Additional levels (beyond -l) may be buggy and
14 // 1: 80-nodes leaf functions, oneliners, panic, lazy typechecking (default)
17 // 4: allow non-leaf functions
19 // At some point this may get another default and become switch-offable with -N.
21 // The -d typcheckinl flag enables early typechecking of all imported bodies,
22 // which is useful to flush out bugs.
24 // The Debug.m flag enables diagnostic output. a single -m is useful for verifying
25 // which calls get inlined or not, more is for debugging, and may go away at any point.
35 "cmd/compile/internal/base"
36 "cmd/compile/internal/ir"
37 "cmd/compile/internal/logopt"
38 "cmd/compile/internal/pgo"
39 "cmd/compile/internal/typecheck"
40 "cmd/compile/internal/types"
44 // Inlining budget parameters, gathered in one place
47 inlineExtraAppendCost = 0
48 // default is to inline if there's at most one call. -l=4 overrides this by using 1 instead.
49 inlineExtraCallCost = 57 // 57 was benchmarked to provided most benefit with no bad surprises; see https://github.com/golang/go/issues/19348#issuecomment-439370742
50 inlineExtraPanicCost = 1 // do not penalize inlining panics.
51 inlineExtraThrowCost = inlineMaxBudget // with current (2018-05/1.11) code, inlining runtime.throw does not help.
53 inlineBigFunctionNodes = 5000 // Functions with this many nodes are considered "big".
54 inlineBigFunctionMaxCost = 20 // Max cost of inlinee when inlining into a "big" function.
58 // List of all hot callee nodes.
59 // TODO(prattmic): Make this non-global.
60 candHotCalleeMap = make(map[*pgo.IRNode]struct{})
62 // List of all hot call sites. CallSiteInfo.Callee is always nil.
63 // TODO(prattmic): Make this non-global.
64 candHotEdgeMap = make(map[pgo.CallSiteInfo]struct{})
66 // List of inlined call sites. CallSiteInfo.Callee is always nil.
67 // TODO(prattmic): Make this non-global.
68 inlinedCallSites = make(map[pgo.CallSiteInfo]struct{})
70 // Threshold in percentage for hot callsite inlining.
71 inlineHotCallSiteThresholdPercent float64
73 // Threshold in CDF percentage for hot callsite inlining,
74 // that is, for a threshold of X the hottest callsites that
75 // make up the top X% of total edge weight will be
76 // considered hot for inlining candidates.
77 inlineCDFHotCallSiteThresholdPercent = float64(99)
79 // Budget increased due to hotness.
80 inlineHotMaxBudget int32 = 2000
83 // pgoInlinePrologue records the hot callsites from ir-graph.
84 func pgoInlinePrologue(p *pgo.Profile, decls []ir.Node) {
85 if base.Debug.PGOInlineCDFThreshold != "" {
86 if s, err := strconv.ParseFloat(base.Debug.PGOInlineCDFThreshold, 64); err == nil && s >= 0 && s <= 100 {
87 inlineCDFHotCallSiteThresholdPercent = s
89 base.Fatalf("invalid PGOInlineCDFThreshold, must be between 0 and 100")
92 var hotCallsites []pgo.NodeMapKey
93 inlineHotCallSiteThresholdPercent, hotCallsites = hotNodesFromCDF(p)
94 if base.Debug.PGOInline > 0 {
95 fmt.Printf("hot-callsite-thres-from-CDF=%v\n", inlineHotCallSiteThresholdPercent)
98 if x := base.Debug.PGOInlineBudget; x != 0 {
99 inlineHotMaxBudget = int32(x)
102 for _, n := range hotCallsites {
103 // mark inlineable callees from hot edges
104 if callee := p.WeightedCG.IRNodes[n.CalleeName]; callee != nil {
105 candHotCalleeMap[callee] = struct{}{}
107 // mark hot call sites
108 if caller := p.WeightedCG.IRNodes[n.CallerName]; caller != nil {
109 csi := pgo.CallSiteInfo{LineOffset: n.CallSiteOffset, Caller: caller.AST}
110 candHotEdgeMap[csi] = struct{}{}
114 if base.Debug.PGOInline >= 2 {
115 fmt.Printf("hot-cg before inline in dot format:")
116 p.PrintWeightedCallGraphDOT(inlineHotCallSiteThresholdPercent)
120 // hotNodesFromCDF computes an edge weight threshold and the list of hot
121 // nodes that make up the given percentage of the CDF. The threshold, as
122 // a percent, is the lower bound of weight for nodes to be considered hot
123 // (currently only used in debug prints) (in case of equal weights,
124 // comparing with the threshold may not accurately reflect which nodes are
126 func hotNodesFromCDF(p *pgo.Profile) (float64, []pgo.NodeMapKey) {
127 nodes := make([]pgo.NodeMapKey, len(p.NodeMap))
129 for n := range p.NodeMap {
133 sort.Slice(nodes, func(i, j int) bool {
134 ni, nj := nodes[i], nodes[j]
135 if wi, wj := p.NodeMap[ni].EWeight, p.NodeMap[nj].EWeight; wi != wj {
136 return wi > wj // want larger weight first
138 // same weight, order by name/line number
139 if ni.CallerName != nj.CallerName {
140 return ni.CallerName < nj.CallerName
142 if ni.CalleeName != nj.CalleeName {
143 return ni.CalleeName < nj.CalleeName
145 return ni.CallSiteOffset < nj.CallSiteOffset
148 for i, n := range nodes {
149 w := p.NodeMap[n].EWeight
151 if pgo.WeightInPercentage(cum, p.TotalEdgeWeight) > inlineCDFHotCallSiteThresholdPercent {
152 // nodes[:i+1] to include the very last node that makes it to go over the threshold.
153 // (Say, if the CDF threshold is 50% and one hot node takes 60% of weight, we want to
154 // include that node instead of excluding it.)
155 return pgo.WeightInPercentage(w, p.TotalEdgeWeight), nodes[:i+1]
161 // pgoInlineEpilogue updates IRGraph after inlining.
162 func pgoInlineEpilogue(p *pgo.Profile, decls []ir.Node) {
163 if base.Debug.PGOInline >= 2 {
164 ir.VisitFuncsBottomUp(decls, func(list []*ir.Func, recursive bool) {
165 for _, f := range list {
166 name := ir.LinkFuncName(f)
167 if n, ok := p.WeightedCG.IRNodes[name]; ok {
168 p.RedirectEdges(n, inlinedCallSites)
172 // Print the call-graph after inlining. This is a debugging feature.
173 fmt.Printf("hot-cg after inline in dot:")
174 p.PrintWeightedCallGraphDOT(inlineHotCallSiteThresholdPercent)
178 // InlinePackage finds functions that can be inlined and clones them before walk expands them.
179 func InlinePackage(p *pgo.Profile) {
180 InlineDecls(p, typecheck.Target.Decls, true)
182 // Perform a garbage collection of hidden closures functions that
183 // are no longer reachable from top-level functions following
184 // inlining. See #59404 and #59638 for more context.
185 garbageCollectUnreferencedHiddenClosures()
188 // InlineDecls applies inlining to the given batch of declarations.
189 func InlineDecls(p *pgo.Profile, decls []ir.Node, doInline bool) {
191 pgoInlinePrologue(p, decls)
194 doCanInline := func(n *ir.Func, recursive bool, numfns int) {
195 if !recursive || numfns > 1 {
196 // We allow inlining if there is no
197 // recursion, or the recursion cycle is
198 // across more than one function.
201 if base.Flag.LowerM > 1 && n.OClosure == nil {
202 fmt.Printf("%v: cannot inline %v: recursive\n", ir.Line(n), n.Nname)
207 ir.VisitFuncsBottomUp(decls, func(list []*ir.Func, recursive bool) {
208 numfns := numNonClosures(list)
209 // We visit functions within an SCC in fairly arbitrary order,
210 // so by computing inlinability for all functions in the SCC
211 // before performing any inlining, the results are less
212 // sensitive to the order within the SCC (see #58905 for an
214 if base.Debug.InlineSCCOnePass == 0 {
215 // Compute inlinability for all functions in the SCC ...
216 for _, n := range list {
217 doCanInline(n, recursive, numfns)
219 // ... then make a second pass to do inlining of calls.
221 for _, n := range list {
226 // Legacy ordering to make it easier to triage any bugs
227 // or compile time issues that might crop up.
228 for _, n := range list {
229 doCanInline(n, recursive, numfns)
238 pgoInlineEpilogue(p, decls)
242 // garbageCollectUnreferencedHiddenClosures makes a pass over all the
243 // top-level (non-hidden-closure) functions looking for nested closure
244 // functions that are reachable, then sweeps through the Target.Decls
245 // list and marks any non-reachable hidden closure function as dead.
246 // See issues #59404 and #59638 for more context.
247 func garbageCollectUnreferencedHiddenClosures() {
249 liveFuncs := make(map[*ir.Func]bool)
251 var markLiveFuncs func(fn *ir.Func)
252 markLiveFuncs = func(fn *ir.Func) {
257 ir.Visit(fn, func(n ir.Node) {
258 if clo, ok := n.(*ir.ClosureExpr); ok {
259 markLiveFuncs(clo.Func)
264 for i := 0; i < len(typecheck.Target.Decls); i++ {
265 if fn, ok := typecheck.Target.Decls[i].(*ir.Func); ok {
266 if fn.IsHiddenClosure() {
273 for i := 0; i < len(typecheck.Target.Decls); i++ {
274 if fn, ok := typecheck.Target.Decls[i].(*ir.Func); ok {
275 if !fn.IsHiddenClosure() {
278 if fn.IsDeadcodeClosure() {
284 fn.SetIsDeadcodeClosure(true)
285 if base.Flag.LowerM > 2 {
286 fmt.Printf("%v: unreferenced closure %v marked as dead\n", ir.Line(fn), fn)
288 if fn.Inl != nil && fn.LSym == nil {
289 ir.InitLSym(fn, true)
295 // CanInline determines whether fn is inlineable.
296 // If so, CanInline saves copies of fn.Body and fn.Dcl in fn.Inl.
297 // fn and fn.Body will already have been typechecked.
298 func CanInline(fn *ir.Func, profile *pgo.Profile) {
300 base.Fatalf("CanInline no nname %+v", fn)
303 var reason string // reason, if any, that the function was not inlined
304 if base.Flag.LowerM > 1 || logopt.Enabled() {
307 if base.Flag.LowerM > 1 {
308 fmt.Printf("%v: cannot inline %v: %s\n", ir.Line(fn), fn.Nname, reason)
310 if logopt.Enabled() {
311 logopt.LogOpt(fn.Pos(), "cannotInlineFunction", "inline", ir.FuncName(fn), reason)
317 // If marked "go:noinline", don't inline
318 if fn.Pragma&ir.Noinline != 0 {
319 reason = "marked go:noinline"
323 // If marked "go:norace" and -race compilation, don't inline.
324 if base.Flag.Race && fn.Pragma&ir.Norace != 0 {
325 reason = "marked go:norace with -race compilation"
329 // If marked "go:nocheckptr" and -d checkptr compilation, don't inline.
330 if base.Debug.Checkptr != 0 && fn.Pragma&ir.NoCheckPtr != 0 {
331 reason = "marked go:nocheckptr"
335 // If marked "go:cgo_unsafe_args", don't inline, since the
336 // function makes assumptions about its argument frame layout.
337 if fn.Pragma&ir.CgoUnsafeArgs != 0 {
338 reason = "marked go:cgo_unsafe_args"
342 // If marked as "go:uintptrkeepalive", don't inline, since the
343 // keep alive information is lost during inlining.
345 // TODO(prattmic): This is handled on calls during escape analysis,
346 // which is after inlining. Move prior to inlining so the keep-alive is
347 // maintained after inlining.
348 if fn.Pragma&ir.UintptrKeepAlive != 0 {
349 reason = "marked as having a keep-alive uintptr argument"
353 // If marked as "go:uintptrescapes", don't inline, since the
354 // escape information is lost during inlining.
355 if fn.Pragma&ir.UintptrEscapes != 0 {
356 reason = "marked as having an escaping uintptr argument"
360 // The nowritebarrierrec checker currently works at function
361 // granularity, so inlining yeswritebarrierrec functions can
362 // confuse it (#22342). As a workaround, disallow inlining
364 if fn.Pragma&ir.Yeswritebarrierrec != 0 {
365 reason = "marked go:yeswritebarrierrec"
369 // If fn has no body (is defined outside of Go), cannot inline it.
370 if len(fn.Body) == 0 {
371 reason = "no function body"
375 // If fn is synthetic hash or eq function, cannot inline it.
376 // The function is not generated in Unified IR frontend at this moment.
377 if ir.IsEqOrHashFunc(fn) {
378 reason = "type eq/hash function"
382 if fn.Typecheck() == 0 {
383 base.Fatalf("CanInline on non-typechecked function %v", fn)
387 if n.Func.InlinabilityChecked() {
390 defer n.Func.SetInlinabilityChecked(true)
392 cc := int32(inlineExtraCallCost)
393 if base.Flag.LowerL == 4 {
394 cc = 1 // this appears to yield better performance than 0.
397 // Update the budget for profile-guided inlining.
398 budget := int32(inlineMaxBudget)
400 if n, ok := profile.WeightedCG.IRNodes[ir.LinkFuncName(fn)]; ok {
401 if _, ok := candHotCalleeMap[n]; ok {
402 budget = int32(inlineHotMaxBudget)
403 if base.Debug.PGOInline > 0 {
404 fmt.Printf("hot-node enabled increased budget=%v for func=%v\n", budget, ir.PkgFuncName(fn))
410 // At this point in the game the function we're looking at may
411 // have "stale" autos, vars that still appear in the Dcl list, but
412 // which no longer have any uses in the function body (due to
413 // elimination by deadcode). We'd like to exclude these dead vars
414 // when creating the "Inline.Dcl" field below; to accomplish this,
415 // the hairyVisitor below builds up a map of used/referenced
416 // locals, and we use this map to produce a pruned Inline.Dcl
417 // list. See issue 25249 for more context.
419 visitor := hairyVisitor{
426 if visitor.tooHairy(fn) {
427 reason = visitor.reason
431 n.Func.Inl = &ir.Inline{
432 Cost: budget - visitor.budget,
433 Dcl: pruneUnusedAutos(n.Defn.(*ir.Func).Dcl, &visitor),
434 Body: inlcopylist(fn.Body),
436 CanDelayResults: canDelayResults(fn),
439 if base.Flag.LowerM > 1 {
440 fmt.Printf("%v: can inline %v with cost %d as: %v { %v }\n", ir.Line(fn), n, budget-visitor.budget, fn.Type(), ir.Nodes(n.Func.Inl.Body))
441 } else if base.Flag.LowerM != 0 {
442 fmt.Printf("%v: can inline %v\n", ir.Line(fn), n)
444 if logopt.Enabled() {
445 logopt.LogOpt(fn.Pos(), "canInlineFunction", "inline", ir.FuncName(fn), fmt.Sprintf("cost: %d", budget-visitor.budget))
449 // canDelayResults reports whether inlined calls to fn can delay
450 // declaring the result parameter until the "return" statement.
451 func canDelayResults(fn *ir.Func) bool {
452 // We can delay declaring+initializing result parameters if:
453 // (1) there's exactly one "return" statement in the inlined function;
454 // (2) it's not an empty return statement (#44355); and
455 // (3) the result parameters aren't named.
458 ir.VisitList(fn.Body, func(n ir.Node) {
459 if n, ok := n.(*ir.ReturnStmt); ok {
461 if len(n.Results) == 0 {
462 nreturns++ // empty return statement (case 2)
468 return false // not exactly one return statement (case 1)
471 // temporaries for return values.
472 for _, param := range fn.Type().Results().FieldSlice() {
473 if sym := types.OrigSym(param.Sym); sym != nil && !sym.IsBlank() {
474 return false // found a named result parameter (case 3)
481 // hairyVisitor visits a function body to determine its inlining
482 // hairiness and whether or not it can be inlined.
483 type hairyVisitor struct {
484 // This is needed to access the current caller in the doNode function.
490 usedLocals ir.NameSet
491 do func(ir.Node) bool
495 func (v *hairyVisitor) tooHairy(fn *ir.Func) bool {
496 v.do = v.doNode // cache closure
497 if ir.DoChildren(fn, v.do) {
501 v.reason = fmt.Sprintf("function too complex: cost %d exceeds budget %d", v.maxBudget-v.budget, v.maxBudget)
507 // doNode visits n and its children, updates the state in v, and returns true if
508 // n makes the current function too hairy for inlining.
509 func (v *hairyVisitor) doNode(n ir.Node) bool {
514 // Call is okay if inlinable and we have the budget for the body.
516 n := n.(*ir.CallExpr)
517 // Functions that call runtime.getcaller{pc,sp} can not be inlined
518 // because getcaller{pc,sp} expect a pointer to the caller's first argument.
520 // runtime.throw is a "cheap call" like panic in normal code.
521 if n.X.Op() == ir.ONAME {
522 name := n.X.(*ir.Name)
523 if name.Class == ir.PFUNC && types.IsRuntimePkg(name.Sym().Pkg) {
524 fn := name.Sym().Name
525 if fn == "getcallerpc" || fn == "getcallersp" {
526 v.reason = "call to " + fn
530 v.budget -= inlineExtraThrowCost
534 // Special case for coverage counter updates; although
535 // these correspond to real operations, we treat them as
536 // zero cost for the moment. This is due to the existence
537 // of tests that are sensitive to inlining-- if the
538 // insertion of coverage instrumentation happens to tip a
539 // given function over the threshold and move it from
540 // "inlinable" to "not-inlinable", this can cause changes
541 // in allocation behavior, which can then result in test
542 // failures (a good example is the TestAllocations in
544 if isAtomicCoverageCounterUpdate(n) {
548 if n.X.Op() == ir.OMETHEXPR {
549 if meth := ir.MethodExprName(n.X); meth != nil {
550 if fn := meth.Func; fn != nil {
553 if types.IsRuntimePkg(s.Pkg) && s.Name == "heapBits.nextArena" {
554 // Special case: explicitly allow mid-stack inlining of
555 // runtime.heapBits.next even though it calls slow-path
556 // runtime.heapBits.nextArena.
559 // Special case: on architectures that can do unaligned loads,
560 // explicitly mark encoding/binary methods as cheap,
561 // because in practice they are, even though our inlining
562 // budgeting system does not see that. See issue 42958.
563 if base.Ctxt.Arch.CanMergeLoads && s.Pkg.Path == "encoding/binary" {
565 case "littleEndian.Uint64", "littleEndian.Uint32", "littleEndian.Uint16",
566 "bigEndian.Uint64", "bigEndian.Uint32", "bigEndian.Uint16",
567 "littleEndian.PutUint64", "littleEndian.PutUint32", "littleEndian.PutUint16",
568 "bigEndian.PutUint64", "bigEndian.PutUint32", "bigEndian.PutUint16",
569 "littleEndian.AppendUint64", "littleEndian.AppendUint32", "littleEndian.AppendUint16",
570 "bigEndian.AppendUint64", "bigEndian.AppendUint32", "bigEndian.AppendUint16":
575 break // treat like any other node, that is, cost of 1
581 // Determine if the callee edge is for an inlinable hot callee or not.
582 if v.profile != nil && v.curFunc != nil {
583 if fn := inlCallee(n.X, v.profile); fn != nil && typecheck.HaveInlineBody(fn) {
584 lineOffset := pgo.NodeLineOffset(n, fn)
585 csi := pgo.CallSiteInfo{LineOffset: lineOffset, Caller: v.curFunc}
586 if _, o := candHotEdgeMap[csi]; o {
587 if base.Debug.PGOInline > 0 {
588 fmt.Printf("hot-callsite identified at line=%v for func=%v\n", ir.Line(n), ir.PkgFuncName(v.curFunc))
594 if ir.IsIntrinsicCall(n) {
595 // Treat like any other node.
599 if fn := inlCallee(n.X, v.profile); fn != nil && typecheck.HaveInlineBody(fn) {
600 v.budget -= fn.Inl.Cost
604 // Call cost for non-leaf inlining.
605 v.budget -= v.extraCallCost
608 base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
610 // Things that are too hairy, irrespective of the budget
611 case ir.OCALL, ir.OCALLINTER:
612 // Call cost for non-leaf inlining.
613 v.budget -= v.extraCallCost
616 n := n.(*ir.UnaryExpr)
617 if n.X.Op() == ir.OCONVIFACE && n.X.(*ir.ConvExpr).Implicit() {
618 // Hack to keep reflect.flag.mustBe inlinable for TestIntendedInlining.
619 // Before CL 284412, these conversions were introduced later in the
620 // compiler, so they didn't count against inlining budget.
623 v.budget -= inlineExtraPanicCost
626 // recover matches the argument frame pointer to find
627 // the right panic value, so it needs an argument frame.
628 v.reason = "call to recover"
632 if base.Debug.InlFuncsWithClosures == 0 {
633 v.reason = "not inlining functions with closures"
637 // TODO(danscales): Maybe make budget proportional to number of closure
639 //v.budget -= int32(len(n.(*ir.ClosureExpr).Func.ClosureVars) * 3)
640 // TODO(austin): However, if we're able to inline this closure into
641 // v.curFunc, then we actually pay nothing for the closure captures. We
642 // should try to account for that if we're going to account for captures.
647 ir.ODCLTYPE, // can't print yet
649 v.reason = "unhandled op " + n.Op().String()
653 v.budget -= inlineExtraAppendCost
656 n := n.(*ir.AddrExpr)
657 // Make "&s.f" cost 0 when f's offset is zero.
658 if dot, ok := n.X.(*ir.SelectorExpr); ok && (dot.Op() == ir.ODOT || dot.Op() == ir.ODOTPTR) {
659 if _, ok := dot.X.(*ir.Name); ok && dot.Selection.Offset == 0 {
660 v.budget += 2 // undo ir.OADDR+ir.ODOT/ir.ODOTPTR
665 // *(*X)(unsafe.Pointer(&x)) is low-cost
666 n := n.(*ir.StarExpr)
669 for ptr.Op() == ir.OCONVNOP {
670 ptr = ptr.(*ir.ConvExpr).X
672 if ptr.Op() == ir.OADDR {
673 v.budget += 1 // undo half of default cost of ir.ODEREF+ir.OADDR
677 // This doesn't produce code, but the children might.
678 v.budget++ // undo default cost
680 case ir.ODCLCONST, ir.OFALL:
681 // These nodes don't produce code; omit from inlining budget.
686 if ir.IsConst(n.Cond, constant.Bool) {
687 // This if and the condition cost nothing.
688 if doList(n.Init(), v.do) {
691 if ir.BoolVal(n.Cond) {
692 return doList(n.Body, v.do)
694 return doList(n.Else, v.do)
700 if n.Class == ir.PAUTO {
705 // The only OBLOCK we should see at this point is an empty one.
706 // In any event, let the visitList(n.List()) below take care of the statements,
707 // and don't charge for the OBLOCK itself. The ++ undoes the -- below.
710 case ir.OMETHVALUE, ir.OSLICELIT:
711 v.budget-- // Hack for toolstash -cmp.
714 v.budget++ // Hack for toolstash -cmp.
717 n := n.(*ir.AssignListStmt)
719 // Unified IR unconditionally rewrites:
730 // so that it can insert implicit conversions as necessary. To
731 // minimize impact to the existing inlining heuristics (in
732 // particular, to avoid breaking the existing inlinability regress
733 // tests), we need to compensate for this here.
735 // See also identical logic in isBigFunc.
736 if init := n.Rhs[0].Init(); len(init) == 1 {
737 if _, ok := init[0].(*ir.AssignListStmt); ok {
738 // 4 for each value, because each temporary variable now
739 // appears 3 times (DCL, LHS, RHS), plus an extra DCL node.
741 // 1 for the extra "tmp1, tmp2 = f()" assignment statement.
742 v.budget += 4*int32(len(n.Lhs)) + 1
747 // Special case for coverage counter updates and coverage
748 // function registrations. Although these correspond to real
749 // operations, we treat them as zero cost for the moment. This
750 // is primarily due to the existence of tests that are
751 // sensitive to inlining-- if the insertion of coverage
752 // instrumentation happens to tip a given function over the
753 // threshold and move it from "inlinable" to "not-inlinable",
754 // this can cause changes in allocation behavior, which can
755 // then result in test failures (a good example is the
756 // TestAllocations in crypto/ed25519).
757 n := n.(*ir.AssignStmt)
758 if n.X.Op() == ir.OINDEX && isIndexingCoverageCounter(n.X) {
765 // When debugging, don't stop early, to get full cost of inlining this function
766 if v.budget < 0 && base.Flag.LowerM < 2 && !logopt.Enabled() {
767 v.reason = "too expensive"
771 return ir.DoChildren(n, v.do)
774 func isBigFunc(fn *ir.Func) bool {
775 budget := inlineBigFunctionNodes
776 return ir.Any(fn, func(n ir.Node) bool {
777 // See logic in hairyVisitor.doNode, explaining unified IR's
778 // handling of "a, b = f()" assignments.
779 if n, ok := n.(*ir.AssignListStmt); ok && n.Op() == ir.OAS2 {
780 if init := n.Rhs[0].Init(); len(init) == 1 {
781 if _, ok := init[0].(*ir.AssignListStmt); ok {
782 budget += 4*len(n.Lhs) + 1
792 // inlcopylist (together with inlcopy) recursively copies a list of nodes, except
793 // that it keeps the same ONAME, OTYPE, and OLITERAL nodes. It is used for copying
794 // the body and dcls of an inlineable function.
795 func inlcopylist(ll []ir.Node) []ir.Node {
796 s := make([]ir.Node, len(ll))
797 for i, n := range ll {
803 // inlcopy is like DeepCopy(), but does extra work to copy closures.
804 func inlcopy(n ir.Node) ir.Node {
805 var edit func(ir.Node) ir.Node
806 edit = func(x ir.Node) ir.Node {
808 case ir.ONAME, ir.OTYPE, ir.OLITERAL, ir.ONIL:
812 ir.EditChildren(m, edit)
813 if x.Op() == ir.OCLOSURE {
814 x := x.(*ir.ClosureExpr)
815 // Need to save/duplicate x.Func.Nname,
816 // x.Func.Nname.Ntype, x.Func.Dcl, x.Func.ClosureVars, and
817 // x.Func.Body for iexport and local inlining.
819 newfn := ir.NewFunc(oldfn.Pos())
820 m.(*ir.ClosureExpr).Func = newfn
821 newfn.Nname = ir.NewNameAt(oldfn.Nname.Pos(), oldfn.Nname.Sym())
822 // XXX OK to share fn.Type() ??
823 newfn.Nname.SetType(oldfn.Nname.Type())
824 newfn.Body = inlcopylist(oldfn.Body)
825 // Make shallow copy of the Dcl and ClosureVar slices
826 newfn.Dcl = append([]*ir.Name(nil), oldfn.Dcl...)
827 newfn.ClosureVars = append([]*ir.Name(nil), oldfn.ClosureVars...)
834 // InlineCalls/inlnode walks fn's statements and expressions and substitutes any
835 // calls made to inlineable functions. This is the external entry point.
836 func InlineCalls(fn *ir.Func, profile *pgo.Profile) {
839 bigCaller := isBigFunc(fn)
840 if bigCaller && base.Flag.LowerM > 1 {
841 fmt.Printf("%v: function %v considered 'big'; reducing max cost of inlinees\n", ir.Line(fn), fn)
843 var inlCalls []*ir.InlinedCallExpr
844 var edit func(ir.Node) ir.Node
845 edit = func(n ir.Node) ir.Node {
846 return inlnode(n, bigCaller, &inlCalls, edit, profile)
848 ir.EditChildren(fn, edit)
850 // If we inlined any calls, we want to recursively visit their
851 // bodies for further inlining. However, we need to wait until
852 // *after* the original function body has been expanded, or else
853 // inlCallee can have false positives (e.g., #54632).
854 for len(inlCalls) > 0 {
856 inlCalls = inlCalls[1:]
857 ir.EditChildren(call, edit)
863 // inlnode recurses over the tree to find inlineable calls, which will
864 // be turned into OINLCALLs by mkinlcall. When the recursion comes
865 // back up will examine left, right, list, rlist, ninit, ntest, nincr,
866 // nbody and nelse and use one of the 4 inlconv/glue functions above
867 // to turn the OINLCALL into an expression, a statement, or patch it
868 // in to this nodes list or rlist as appropriate.
869 // NOTE it makes no sense to pass the glue functions down the
870 // recursion to the level where the OINLCALL gets created because they
871 // have to edit /this/ n, so you'd have to push that one down as well,
872 // but then you may as well do it here. so this is cleaner and
873 // shorter and less complicated.
874 // The result of inlnode MUST be assigned back to n, e.g.
876 // n.Left = inlnode(n.Left)
877 func inlnode(n ir.Node, bigCaller bool, inlCalls *[]*ir.InlinedCallExpr, edit func(ir.Node) ir.Node, profile *pgo.Profile) ir.Node {
883 case ir.ODEFER, ir.OGO:
884 n := n.(*ir.GoDeferStmt)
885 switch call := n.Call; call.Op() {
887 base.FatalfAt(call.Pos(), "OCALLMETH missed by typecheck")
889 call := call.(*ir.CallExpr)
893 n := n.(*ir.TailCallStmt)
894 n.Call.NoInline = true // Not inline a tail call for now. Maybe we could inline it just like RETURN fn(arg)?
896 // TODO do them here (or earlier),
897 // so escape analysis can avoid more heapmoves.
901 base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
903 n := n.(*ir.CallExpr)
904 if n.X.Op() == ir.OMETHEXPR {
905 // Prevent inlining some reflect.Value methods when using checkptr,
906 // even when package reflect was compiled without it (#35073).
907 if meth := ir.MethodExprName(n.X); meth != nil {
909 if base.Debug.Checkptr != 0 && types.IsReflectPkg(s.Pkg) && (s.Name == "Value.UnsafeAddr" || s.Name == "Value.Pointer") {
918 ir.EditChildren(n, edit)
920 // with all the branches out of the way, it is now time to
921 // transmogrify this node itself unless inhibited by the
922 // switch at the top of this function.
925 base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
928 call := n.(*ir.CallExpr)
932 if base.Flag.LowerM > 3 {
933 fmt.Printf("%v:call to func %+v\n", ir.Line(n), call.X)
935 if ir.IsIntrinsicCall(call) {
938 if fn := inlCallee(call.X, profile); fn != nil && typecheck.HaveInlineBody(fn) {
939 n = mkinlcall(call, fn, bigCaller, inlCalls)
948 // inlCallee takes a function-typed expression and returns the underlying function ONAME
949 // that it refers to if statically known. Otherwise, it returns nil.
950 func inlCallee(fn ir.Node, profile *pgo.Profile) *ir.Func {
951 fn = ir.StaticValue(fn)
954 fn := fn.(*ir.SelectorExpr)
955 n := ir.MethodExprName(fn)
956 // Check that receiver type matches fn.X.
957 // TODO(mdempsky): Handle implicit dereference
958 // of pointer receiver argument?
959 if n == nil || !types.Identical(n.Type().Recv().Type, fn.X.Type()) {
965 if fn.Class == ir.PFUNC {
969 fn := fn.(*ir.ClosureExpr)
971 CanInline(c, profile)
979 // SSADumpInline gives the SSA back end a chance to dump the function
980 // when producing output for debugging the compiler itself.
981 var SSADumpInline = func(*ir.Func) {}
983 // InlineCall allows the inliner implementation to be overridden.
984 // If it returns nil, the function will not be inlined.
985 var InlineCall = func(call *ir.CallExpr, fn *ir.Func, inlIndex int) *ir.InlinedCallExpr {
986 base.Fatalf("inline.InlineCall not overridden")
990 // inlineCostOK returns true if call n from caller to callee is cheap enough to
991 // inline. bigCaller indicates that caller is a big function.
993 // If inlineCostOK returns false, it also returns the max cost that the callee
995 func inlineCostOK(n *ir.CallExpr, caller, callee *ir.Func, bigCaller bool) (bool, int32) {
996 maxCost := int32(inlineMaxBudget)
998 // We use this to restrict inlining into very big functions.
999 // See issue 26546 and 17566.
1000 maxCost = inlineBigFunctionMaxCost
1003 if callee.Inl.Cost <= maxCost {
1004 // Simple case. Function is already cheap enough.
1008 // We'll also allow inlining of hot functions below inlineHotMaxBudget,
1009 // but only in small functions.
1011 lineOffset := pgo.NodeLineOffset(n, caller)
1012 csi := pgo.CallSiteInfo{LineOffset: lineOffset, Caller: caller}
1013 if _, ok := candHotEdgeMap[csi]; !ok {
1015 return false, maxCost
1021 if base.Debug.PGOInline > 0 {
1022 fmt.Printf("hot-big check disallows inlining for call %s (cost %d) at %v in big function %s\n", ir.PkgFuncName(callee), callee.Inl.Cost, ir.Line(n), ir.PkgFuncName(caller))
1024 return false, maxCost
1027 if callee.Inl.Cost > inlineHotMaxBudget {
1028 return false, inlineHotMaxBudget
1031 if base.Debug.PGOInline > 0 {
1032 fmt.Printf("hot-budget check allows inlining for call %s (cost %d) at %v in function %s\n", ir.PkgFuncName(callee), callee.Inl.Cost, ir.Line(n), ir.PkgFuncName(caller))
1038 // If n is a OCALLFUNC node, and fn is an ONAME node for a
1039 // function with an inlinable body, return an OINLCALL node that can replace n.
1040 // The returned node's Ninit has the parameter assignments, the Nbody is the
1041 // inlined function body, and (List, Rlist) contain the (input, output)
1043 // The result of mkinlcall MUST be assigned back to n, e.g.
1045 // n.Left = mkinlcall(n.Left, fn, isddd)
1046 func mkinlcall(n *ir.CallExpr, fn *ir.Func, bigCaller bool, inlCalls *[]*ir.InlinedCallExpr) ir.Node {
1048 if logopt.Enabled() {
1049 logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", ir.FuncName(ir.CurFunc),
1050 fmt.Sprintf("%s cannot be inlined", ir.PkgFuncName(fn)))
1055 if ok, maxCost := inlineCostOK(n, ir.CurFunc, fn, bigCaller); !ok {
1056 if logopt.Enabled() {
1057 logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", ir.FuncName(ir.CurFunc),
1058 fmt.Sprintf("cost %d of %s exceeds max caller cost %d", fn.Inl.Cost, ir.PkgFuncName(fn), maxCost))
1063 if fn == ir.CurFunc {
1064 // Can't recursively inline a function into itself.
1065 if logopt.Enabled() {
1066 logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", fmt.Sprintf("recursive call to %s", ir.FuncName(ir.CurFunc)))
1071 if base.Flag.Cfg.Instrumenting && types.IsRuntimePkg(fn.Sym().Pkg) {
1072 // Runtime package must not be instrumented.
1073 // Instrument skips runtime package. However, some runtime code can be
1074 // inlined into other packages and instrumented there. To avoid this,
1075 // we disable inlining of runtime functions when instrumenting.
1076 // The example that we observed is inlining of LockOSThread,
1077 // which lead to false race reports on m contents.
1081 parent := base.Ctxt.PosTable.Pos(n.Pos()).Base().InliningIndex()
1084 // Check if we've already inlined this function at this particular
1085 // call site, in order to stop inlining when we reach the beginning
1086 // of a recursion cycle again. We don't inline immediately recursive
1087 // functions, but allow inlining if there is a recursion cycle of
1088 // many functions. Most likely, the inlining will stop before we
1089 // even hit the beginning of the cycle again, but this catches the
1091 for inlIndex := parent; inlIndex >= 0; inlIndex = base.Ctxt.InlTree.Parent(inlIndex) {
1092 if base.Ctxt.InlTree.InlinedFunction(inlIndex) == sym {
1093 if base.Flag.LowerM > 1 {
1094 fmt.Printf("%v: cannot inline %v into %v: repeated recursive cycle\n", ir.Line(n), fn, ir.FuncName(ir.CurFunc))
1100 typecheck.AssertFixedCall(n)
1102 inlIndex := base.Ctxt.InlTree.Add(parent, n.Pos(), sym)
1104 closureInitLSym := func(n *ir.CallExpr, fn *ir.Func) {
1105 // The linker needs FuncInfo metadata for all inlined
1106 // functions. This is typically handled by gc.enqueueFunc
1107 // calling ir.InitLSym for all function declarations in
1108 // typecheck.Target.Decls (ir.UseClosure adds all closures to
1111 // However, non-trivial closures in Decls are ignored, and are
1112 // insteaded enqueued when walk of the calling function
1115 // This presents a problem for direct calls to closures.
1116 // Inlining will replace the entire closure definition with its
1117 // body, which hides the closure from walk and thus suppresses
1120 // Explicitly create a symbol early in this edge case to ensure
1121 // we keep this metadata.
1123 // TODO: Refactor to keep a reference so this can all be done
1126 if n.Op() != ir.OCALLFUNC {
1127 // Not a standard call.
1130 if n.X.Op() != ir.OCLOSURE {
1131 // Not a direct closure call.
1135 clo := n.X.(*ir.ClosureExpr)
1136 if ir.IsTrivialClosure(clo) {
1137 // enqueueFunc will handle trivial closures anyways.
1141 ir.InitLSym(fn, true)
1144 closureInitLSym(n, fn)
1146 if base.Flag.GenDwarfInl > 0 {
1147 if !sym.WasInlined() {
1148 base.Ctxt.DwFixups.SetPrecursorFunc(sym, fn)
1149 sym.Set(obj.AttrWasInlined, true)
1153 if base.Flag.LowerM != 0 {
1154 fmt.Printf("%v: inlining call to %v\n", ir.Line(n), fn)
1156 if base.Flag.LowerM > 2 {
1157 fmt.Printf("%v: Before inlining: %+v\n", ir.Line(n), n)
1160 if base.Debug.PGOInline > 0 {
1161 csi := pgo.CallSiteInfo{LineOffset: pgo.NodeLineOffset(n, fn), Caller: ir.CurFunc}
1162 if _, ok := inlinedCallSites[csi]; !ok {
1163 inlinedCallSites[csi] = struct{}{}
1167 res := InlineCall(n, fn, inlIndex)
1170 base.FatalfAt(n.Pos(), "inlining call to %v failed", fn)
1173 if base.Flag.LowerM > 2 {
1174 fmt.Printf("%v: After inlining %+v\n\n", ir.Line(res), res)
1177 *inlCalls = append(*inlCalls, res)
1182 // CalleeEffects appends any side effects from evaluating callee to init.
1183 func CalleeEffects(init *ir.Nodes, callee ir.Node) {
1185 init.Append(ir.TakeInit(callee)...)
1187 switch callee.Op() {
1188 case ir.ONAME, ir.OCLOSURE, ir.OMETHEXPR:
1192 conv := callee.(*ir.ConvExpr)
1196 ic := callee.(*ir.InlinedCallExpr)
1197 init.Append(ic.Body.Take()...)
1198 callee = ic.SingleResult()
1201 base.FatalfAt(callee.Pos(), "unexpected callee expression: %v", callee)
1206 func pruneUnusedAutos(ll []*ir.Name, vis *hairyVisitor) []*ir.Name {
1207 s := make([]*ir.Name, 0, len(ll))
1208 for _, n := range ll {
1209 if n.Class == ir.PAUTO {
1210 if !vis.usedLocals.Has(n) {
1219 // numNonClosures returns the number of functions in list which are not closures.
1220 func numNonClosures(list []*ir.Func) int {
1222 for _, fn := range list {
1223 if fn.OClosure == nil {
1230 func doList(list []ir.Node, do func(ir.Node) bool) bool {
1231 for _, x := range list {
1241 // isIndexingCoverageCounter returns true if the specified node 'n' is indexing
1242 // into a coverage counter array.
1243 func isIndexingCoverageCounter(n ir.Node) bool {
1244 if n.Op() != ir.OINDEX {
1247 ixn := n.(*ir.IndexExpr)
1248 if ixn.X.Op() != ir.ONAME || !ixn.X.Type().IsArray() {
1251 nn := ixn.X.(*ir.Name)
1252 return nn.CoverageCounter()
1255 // isAtomicCoverageCounterUpdate examines the specified node to
1256 // determine whether it represents a call to sync/atomic.AddUint32 to
1257 // increment a coverage counter.
1258 func isAtomicCoverageCounterUpdate(cn *ir.CallExpr) bool {
1259 if cn.X.Op() != ir.ONAME {
1262 name := cn.X.(*ir.Name)
1263 if name.Class != ir.PFUNC {
1266 fn := name.Sym().Name
1267 if name.Sym().Pkg.Path != "sync/atomic" ||
1268 (fn != "AddUint32" && fn != "StoreUint32") {
1271 if len(cn.Args) != 2 || cn.Args[0].Op() != ir.OADDR {
1274 adn := cn.Args[0].(*ir.AddrExpr)
1275 v := isIndexingCoverageCounter(adn.X)