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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//
// The inlining facility makes 2 passes: first CanInline determines which
// functions are suitable for inlining, and for those that are it
// saves a copy of the body. Then InlineCalls walks each function body to
// expand calls to inlinable functions.
//
// The Debug.l flag controls the aggressiveness. Note that main() swaps level 0 and 1,
// making 1 the default and -l disable. Additional levels (beyond -l) may be buggy and
// are not supported.
// 0: disabled
// 1: 80-nodes leaf functions, oneliners, panic, lazy typechecking (default)
// 2: (unassigned)
// 3: (unassigned)
// 4: allow non-leaf functions
//
// At some point this may get another default and become switch-offable with -N.
//
// The -d typcheckinl flag enables early typechecking of all imported bodies,
// which is useful to flush out bugs.
//
// The Debug.m flag enables diagnostic output. a single -m is useful for verifying
// which calls get inlined or not, more is for debugging, and may go away at any point.
package inline
import (
"fmt"
"go/constant"
"sort"
"strconv"
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
"cmd/compile/internal/logopt"
"cmd/compile/internal/pgo"
"cmd/compile/internal/typecheck"
"cmd/compile/internal/types"
"cmd/internal/obj"
)
// Inlining budget parameters, gathered in one place
const (
inlineMaxBudget = 80
inlineExtraAppendCost = 0
// default is to inline if there's at most one call. -l=4 overrides this by using 1 instead.
inlineExtraCallCost = 57 // 57 was benchmarked to provided most benefit with no bad surprises; see https://github.com/golang/go/issues/19348#issuecomment-439370742
inlineExtraPanicCost = 1 // do not penalize inlining panics.
inlineExtraThrowCost = inlineMaxBudget // with current (2018-05/1.11) code, inlining runtime.throw does not help.
inlineBigFunctionNodes = 5000 // Functions with this many nodes are considered "big".
inlineBigFunctionMaxCost = 20 // Max cost of inlinee when inlining into a "big" function.
)
var (
// List of all hot callee nodes.
// TODO(prattmic): Make this non-global.
candHotCalleeMap = make(map[*pgo.IRNode]struct{})
// List of all hot call sites. CallSiteInfo.Callee is always nil.
// TODO(prattmic): Make this non-global.
candHotEdgeMap = make(map[pgo.CallSiteInfo]struct{})
// Threshold in percentage for hot callsite inlining.
inlineHotCallSiteThresholdPercent float64
// Threshold in CDF percentage for hot callsite inlining,
// that is, for a threshold of X the hottest callsites that
// make up the top X% of total edge weight will be
// considered hot for inlining candidates.
inlineCDFHotCallSiteThresholdPercent = float64(99)
// Budget increased due to hotness.
inlineHotMaxBudget int32 = 2000
)
// pgoInlinePrologue records the hot callsites from ir-graph.
func pgoInlinePrologue(p *pgo.Profile, decls []ir.Node) {
if base.Debug.PGOInlineCDFThreshold != "" {
if s, err := strconv.ParseFloat(base.Debug.PGOInlineCDFThreshold, 64); err == nil && s >= 0 && s <= 100 {
inlineCDFHotCallSiteThresholdPercent = s
} else {
base.Fatalf("invalid PGOInlineCDFThreshold, must be between 0 and 100")
}
}
var hotCallsites []pgo.NodeMapKey
inlineHotCallSiteThresholdPercent, hotCallsites = hotNodesFromCDF(p)
if base.Debug.PGODebug > 0 {
fmt.Printf("hot-callsite-thres-from-CDF=%v\n", inlineHotCallSiteThresholdPercent)
}
if x := base.Debug.PGOInlineBudget; x != 0 {
inlineHotMaxBudget = int32(x)
}
for _, n := range hotCallsites {
// mark inlineable callees from hot edges
if callee := p.WeightedCG.IRNodes[n.CalleeName]; callee != nil {
candHotCalleeMap[callee] = struct{}{}
}
// mark hot call sites
if caller := p.WeightedCG.IRNodes[n.CallerName]; caller != nil && caller.AST != nil {
csi := pgo.CallSiteInfo{LineOffset: n.CallSiteOffset, Caller: caller.AST}
candHotEdgeMap[csi] = struct{}{}
}
}
if base.Debug.PGODebug >= 3 {
fmt.Printf("hot-cg before inline in dot format:")
p.PrintWeightedCallGraphDOT(inlineHotCallSiteThresholdPercent)
}
}
// hotNodesFromCDF computes an edge weight threshold and the list of hot
// nodes that make up the given percentage of the CDF. The threshold, as
// a percent, is the lower bound of weight for nodes to be considered hot
// (currently only used in debug prints) (in case of equal weights,
// comparing with the threshold may not accurately reflect which nodes are
// considiered hot).
func hotNodesFromCDF(p *pgo.Profile) (float64, []pgo.NodeMapKey) {
nodes := make([]pgo.NodeMapKey, len(p.NodeMap))
i := 0
for n := range p.NodeMap {
nodes[i] = n
i++
}
sort.Slice(nodes, func(i, j int) bool {
ni, nj := nodes[i], nodes[j]
if wi, wj := p.NodeMap[ni].EWeight, p.NodeMap[nj].EWeight; wi != wj {
return wi > wj // want larger weight first
}
// same weight, order by name/line number
if ni.CallerName != nj.CallerName {
return ni.CallerName < nj.CallerName
}
if ni.CalleeName != nj.CalleeName {
return ni.CalleeName < nj.CalleeName
}
return ni.CallSiteOffset < nj.CallSiteOffset
})
cum := int64(0)
for i, n := range nodes {
w := p.NodeMap[n].EWeight
cum += w
if pgo.WeightInPercentage(cum, p.TotalEdgeWeight) > inlineCDFHotCallSiteThresholdPercent {
// nodes[:i+1] to include the very last node that makes it to go over the threshold.
// (Say, if the CDF threshold is 50% and one hot node takes 60% of weight, we want to
// include that node instead of excluding it.)
return pgo.WeightInPercentage(w, p.TotalEdgeWeight), nodes[:i+1]
}
}
return 0, nodes
}
// InlinePackage finds functions that can be inlined and clones them before walk expands them.
func InlinePackage(p *pgo.Profile) {
if base.Debug.PGOInline == 0 {
p = nil
}
InlineDecls(p, typecheck.Target.Decls, true)
// Perform a garbage collection of hidden closures functions that
// are no longer reachable from top-level functions following
// inlining. See #59404 and #59638 for more context.
garbageCollectUnreferencedHiddenClosures()
}
// InlineDecls applies inlining to the given batch of declarations.
func InlineDecls(p *pgo.Profile, decls []ir.Node, doInline bool) {
if p != nil {
pgoInlinePrologue(p, decls)
}
doCanInline := func(n *ir.Func, recursive bool, numfns int) {
if !recursive || numfns > 1 {
// We allow inlining if there is no
// recursion, or the recursion cycle is
// across more than one function.
CanInline(n, p)
} else {
if base.Flag.LowerM > 1 && n.OClosure == nil {
fmt.Printf("%v: cannot inline %v: recursive\n", ir.Line(n), n.Nname)
}
}
}
ir.VisitFuncsBottomUp(decls, func(list []*ir.Func, recursive bool) {
numfns := numNonClosures(list)
// We visit functions within an SCC in fairly arbitrary order,
// so by computing inlinability for all functions in the SCC
// before performing any inlining, the results are less
// sensitive to the order within the SCC (see #58905 for an
// example).
// First compute inlinability for all functions in the SCC ...
for _, n := range list {
doCanInline(n, recursive, numfns)
}
// ... then make a second pass to do inlining of calls.
if doInline {
for _, n := range list {
InlineCalls(n, p)
}
}
})
}
// garbageCollectUnreferencedHiddenClosures makes a pass over all the
// top-level (non-hidden-closure) functions looking for nested closure
// functions that are reachable, then sweeps through the Target.Decls
// list and marks any non-reachable hidden closure function as dead.
// See issues #59404 and #59638 for more context.
func garbageCollectUnreferencedHiddenClosures() {
liveFuncs := make(map[*ir.Func]bool)
var markLiveFuncs func(fn *ir.Func)
markLiveFuncs = func(fn *ir.Func) {
if liveFuncs[fn] {
return
}
liveFuncs[fn] = true
ir.Visit(fn, func(n ir.Node) {
if clo, ok := n.(*ir.ClosureExpr); ok {
markLiveFuncs(clo.Func)
}
})
}
for i := 0; i < len(typecheck.Target.Decls); i++ {
if fn, ok := typecheck.Target.Decls[i].(*ir.Func); ok {
if fn.IsHiddenClosure() {
continue
}
markLiveFuncs(fn)
}
}
for i := 0; i < len(typecheck.Target.Decls); i++ {
if fn, ok := typecheck.Target.Decls[i].(*ir.Func); ok {
if !fn.IsHiddenClosure() {
continue
}
if fn.IsDeadcodeClosure() {
continue
}
if liveFuncs[fn] {
continue
}
fn.SetIsDeadcodeClosure(true)
if base.Flag.LowerM > 2 {
fmt.Printf("%v: unreferenced closure %v marked as dead\n", ir.Line(fn), fn)
}
if fn.Inl != nil && fn.LSym == nil {
ir.InitLSym(fn, true)
}
}
}
}
// CanInline determines whether fn is inlineable.
// If so, CanInline saves copies of fn.Body and fn.Dcl in fn.Inl.
// fn and fn.Body will already have been typechecked.
func CanInline(fn *ir.Func, profile *pgo.Profile) {
if fn.Nname == nil {
base.Fatalf("CanInline no nname %+v", fn)
}
var reason string // reason, if any, that the function was not inlined
if base.Flag.LowerM > 1 || logopt.Enabled() {
defer func() {
if reason != "" {
if base.Flag.LowerM > 1 {
fmt.Printf("%v: cannot inline %v: %s\n", ir.Line(fn), fn.Nname, reason)
}
if logopt.Enabled() {
logopt.LogOpt(fn.Pos(), "cannotInlineFunction", "inline", ir.FuncName(fn), reason)
}
}
}()
}
reason = InlineImpossible(fn)
if reason != "" {
return
}
if fn.Typecheck() == 0 {
base.Fatalf("CanInline on non-typechecked function %v", fn)
}
n := fn.Nname
if n.Func.InlinabilityChecked() {
return
}
defer n.Func.SetInlinabilityChecked(true)
cc := int32(inlineExtraCallCost)
if base.Flag.LowerL == 4 {
cc = 1 // this appears to yield better performance than 0.
}
// Update the budget for profile-guided inlining.
budget := int32(inlineMaxBudget)
if profile != nil {
if n, ok := profile.WeightedCG.IRNodes[ir.LinkFuncName(fn)]; ok {
if _, ok := candHotCalleeMap[n]; ok {
budget = int32(inlineHotMaxBudget)
if base.Debug.PGODebug > 0 {
fmt.Printf("hot-node enabled increased budget=%v for func=%v\n", budget, ir.PkgFuncName(fn))
}
}
}
}
// At this point in the game the function we're looking at may
// have "stale" autos, vars that still appear in the Dcl list, but
// which no longer have any uses in the function body (due to
// elimination by deadcode). We'd like to exclude these dead vars
// when creating the "Inline.Dcl" field below; to accomplish this,
// the hairyVisitor below builds up a map of used/referenced
// locals, and we use this map to produce a pruned Inline.Dcl
// list. See issue 25249 for more context.
visitor := hairyVisitor{
curFunc: fn,
budget: budget,
maxBudget: budget,
extraCallCost: cc,
profile: profile,
}
if visitor.tooHairy(fn) {
reason = visitor.reason
return
}
n.Func.Inl = &ir.Inline{
Cost: budget - visitor.budget,
Dcl: pruneUnusedAutos(n.Defn.(*ir.Func).Dcl, &visitor),
Body: inlcopylist(fn.Body),
CanDelayResults: canDelayResults(fn),
}
if base.Flag.LowerM > 1 {
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))
} else if base.Flag.LowerM != 0 {
fmt.Printf("%v: can inline %v\n", ir.Line(fn), n)
}
if logopt.Enabled() {
logopt.LogOpt(fn.Pos(), "canInlineFunction", "inline", ir.FuncName(fn), fmt.Sprintf("cost: %d", budget-visitor.budget))
}
}
// InlineImpossible returns a non-empty reason string if fn is impossible to
// inline regardless of cost or contents.
func InlineImpossible(fn *ir.Func) string {
var reason string // reason, if any, that the function can not be inlined.
if fn.Nname == nil {
reason = "no name"
return reason
}
// If marked "go:noinline", don't inline.
if fn.Pragma&ir.Noinline != 0 {
reason = "marked go:noinline"
return reason
}
// If marked "go:norace" and -race compilation, don't inline.
if base.Flag.Race && fn.Pragma&ir.Norace != 0 {
reason = "marked go:norace with -race compilation"
return reason
}
// If marked "go:nocheckptr" and -d checkptr compilation, don't inline.
if base.Debug.Checkptr != 0 && fn.Pragma&ir.NoCheckPtr != 0 {
reason = "marked go:nocheckptr"
return reason
}
// If marked "go:cgo_unsafe_args", don't inline, since the function
// makes assumptions about its argument frame layout.
if fn.Pragma&ir.CgoUnsafeArgs != 0 {
reason = "marked go:cgo_unsafe_args"
return reason
}
// If marked as "go:uintptrkeepalive", don't inline, since the keep
// alive information is lost during inlining.
//
// TODO(prattmic): This is handled on calls during escape analysis,
// which is after inlining. Move prior to inlining so the keep-alive is
// maintained after inlining.
if fn.Pragma&ir.UintptrKeepAlive != 0 {
reason = "marked as having a keep-alive uintptr argument"
return reason
}
// If marked as "go:uintptrescapes", don't inline, since the escape
// information is lost during inlining.
if fn.Pragma&ir.UintptrEscapes != 0 {
reason = "marked as having an escaping uintptr argument"
return reason
}
// The nowritebarrierrec checker currently works at function
// granularity, so inlining yeswritebarrierrec functions can confuse it
// (#22342). As a workaround, disallow inlining them for now.
if fn.Pragma&ir.Yeswritebarrierrec != 0 {
reason = "marked go:yeswritebarrierrec"
return reason
}
// If a local function has no fn.Body (is defined outside of Go), cannot inline it.
// Imported functions don't have fn.Body but might have inline body in fn.Inl.
if len(fn.Body) == 0 && !typecheck.HaveInlineBody(fn) {
reason = "no function body"
return reason
}
// If fn is synthetic hash or eq function, cannot inline it.
// The function is not generated in Unified IR frontend at this moment.
if ir.IsEqOrHashFunc(fn) {
reason = "type eq/hash function"
return reason
}
return ""
}
// canDelayResults reports whether inlined calls to fn can delay
// declaring the result parameter until the "return" statement.
func canDelayResults(fn *ir.Func) bool {
// We can delay declaring+initializing result parameters if:
// (1) there's exactly one "return" statement in the inlined function;
// (2) it's not an empty return statement (#44355); and
// (3) the result parameters aren't named.
nreturns := 0
ir.VisitList(fn.Body, func(n ir.Node) {
if n, ok := n.(*ir.ReturnStmt); ok {
nreturns++
if len(n.Results) == 0 {
nreturns++ // empty return statement (case 2)
}
}
})
if nreturns != 1 {
return false // not exactly one return statement (case 1)
}
// temporaries for return values.
for _, param := range fn.Type().Results().FieldSlice() {
if sym := types.OrigSym(param.Sym); sym != nil && !sym.IsBlank() {
return false // found a named result parameter (case 3)
}
}
return true
}
// hairyVisitor visits a function body to determine its inlining
// hairiness and whether or not it can be inlined.
type hairyVisitor struct {
// This is needed to access the current caller in the doNode function.
curFunc *ir.Func
budget int32
maxBudget int32
reason string
extraCallCost int32
usedLocals ir.NameSet
do func(ir.Node) bool
profile *pgo.Profile
}
func (v *hairyVisitor) tooHairy(fn *ir.Func) bool {
v.do = v.doNode // cache closure
if ir.DoChildren(fn, v.do) {
return true
}
if v.budget < 0 {
v.reason = fmt.Sprintf("function too complex: cost %d exceeds budget %d", v.maxBudget-v.budget, v.maxBudget)
return true
}
return false
}
// doNode visits n and its children, updates the state in v, and returns true if
// n makes the current function too hairy for inlining.
func (v *hairyVisitor) doNode(n ir.Node) bool {
if n == nil {
return false
}
switch n.Op() {
// Call is okay if inlinable and we have the budget for the body.
case ir.OCALLFUNC:
n := n.(*ir.CallExpr)
// Functions that call runtime.getcaller{pc,sp} can not be inlined
// because getcaller{pc,sp} expect a pointer to the caller's first argument.
//
// runtime.throw is a "cheap call" like panic in normal code.
var cheap bool
if n.X.Op() == ir.ONAME {
name := n.X.(*ir.Name)
if name.Class == ir.PFUNC && types.IsRuntimePkg(name.Sym().Pkg) {
fn := name.Sym().Name
if fn == "getcallerpc" || fn == "getcallersp" {
v.reason = "call to " + fn
return true
}
if fn == "throw" {
v.budget -= inlineExtraThrowCost
break
}
}
// Special case for reflect.noescpae. It does just type
// conversions to appease the escape analysis, and doesn't
// generate code.
if name.Class == ir.PFUNC && types.IsReflectPkg(name.Sym().Pkg) {
if name.Sym().Name == "noescape" {
cheap = true
}
}
// Special case for coverage counter updates; although
// these correspond to real operations, we treat them as
// zero cost for the moment. This is due to the existence
// of tests that are sensitive to inlining-- if the
// insertion of coverage instrumentation happens to tip a
// given function over the threshold and move it from
// "inlinable" to "not-inlinable", this can cause changes
// in allocation behavior, which can then result in test
// failures (a good example is the TestAllocations in
// crypto/ed25519).
if isAtomicCoverageCounterUpdate(n) {
return false
}
}
if n.X.Op() == ir.OMETHEXPR {
if meth := ir.MethodExprName(n.X); meth != nil {
if fn := meth.Func; fn != nil {
s := fn.Sym()
if types.IsRuntimePkg(s.Pkg) && s.Name == "heapBits.nextArena" {
// Special case: explicitly allow mid-stack inlining of
// runtime.heapBits.next even though it calls slow-path
// runtime.heapBits.nextArena.
cheap = true
}
// Special case: on architectures that can do unaligned loads,
// explicitly mark encoding/binary methods as cheap,
// because in practice they are, even though our inlining
// budgeting system does not see that. See issue 42958.
if base.Ctxt.Arch.CanMergeLoads && s.Pkg.Path == "encoding/binary" {
switch s.Name {
case "littleEndian.Uint64", "littleEndian.Uint32", "littleEndian.Uint16",
"bigEndian.Uint64", "bigEndian.Uint32", "bigEndian.Uint16",
"littleEndian.PutUint64", "littleEndian.PutUint32", "littleEndian.PutUint16",
"bigEndian.PutUint64", "bigEndian.PutUint32", "bigEndian.PutUint16",
"littleEndian.AppendUint64", "littleEndian.AppendUint32", "littleEndian.AppendUint16",
"bigEndian.AppendUint64", "bigEndian.AppendUint32", "bigEndian.AppendUint16":
cheap = true
}
}
}
}
}
if cheap {
break // treat like any other node, that is, cost of 1
}
// Determine if the callee edge is for an inlinable hot callee or not.
if v.profile != nil && v.curFunc != nil {
if fn := inlCallee(n.X, v.profile); fn != nil && typecheck.HaveInlineBody(fn) {
lineOffset := pgo.NodeLineOffset(n, fn)
csi := pgo.CallSiteInfo{LineOffset: lineOffset, Caller: v.curFunc}
if _, o := candHotEdgeMap[csi]; o {
if base.Debug.PGODebug > 0 {
fmt.Printf("hot-callsite identified at line=%v for func=%v\n", ir.Line(n), ir.PkgFuncName(v.curFunc))
}
}
}
}
if ir.IsIntrinsicCall(n) {
// Treat like any other node.
break
}
if fn := inlCallee(n.X, v.profile); fn != nil && typecheck.HaveInlineBody(fn) {
v.budget -= fn.Inl.Cost
break
}
// Call cost for non-leaf inlining.
v.budget -= v.extraCallCost
case ir.OCALLMETH:
base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
// Things that are too hairy, irrespective of the budget
case ir.OCALL, ir.OCALLINTER:
// Call cost for non-leaf inlining.
v.budget -= v.extraCallCost
case ir.OPANIC:
n := n.(*ir.UnaryExpr)
if n.X.Op() == ir.OCONVIFACE && n.X.(*ir.ConvExpr).Implicit() {
// Hack to keep reflect.flag.mustBe inlinable for TestIntendedInlining.
// Before CL 284412, these conversions were introduced later in the
// compiler, so they didn't count against inlining budget.
v.budget++
}
v.budget -= inlineExtraPanicCost
case ir.ORECOVER:
// recover matches the argument frame pointer to find
// the right panic value, so it needs an argument frame.
v.reason = "call to recover"
return true
case ir.OCLOSURE:
if base.Debug.InlFuncsWithClosures == 0 {
v.reason = "not inlining functions with closures"
return true
}
// TODO(danscales): Maybe make budget proportional to number of closure
// variables, e.g.:
//v.budget -= int32(len(n.(*ir.ClosureExpr).Func.ClosureVars) * 3)
// TODO(austin): However, if we're able to inline this closure into
// v.curFunc, then we actually pay nothing for the closure captures. We
// should try to account for that if we're going to account for captures.
v.budget -= 15
case ir.OGO,
ir.ODEFER,
ir.ODCLTYPE, // can't print yet
ir.OTAILCALL:
v.reason = "unhandled op " + n.Op().String()
return true
case ir.OAPPEND:
v.budget -= inlineExtraAppendCost
case ir.OADDR:
n := n.(*ir.AddrExpr)
// Make "&s.f" cost 0 when f's offset is zero.
if dot, ok := n.X.(*ir.SelectorExpr); ok && (dot.Op() == ir.ODOT || dot.Op() == ir.ODOTPTR) {
if _, ok := dot.X.(*ir.Name); ok && dot.Selection.Offset == 0 {
v.budget += 2 // undo ir.OADDR+ir.ODOT/ir.ODOTPTR
}
}
case ir.ODEREF:
// *(*X)(unsafe.Pointer(&x)) is low-cost
n := n.(*ir.StarExpr)
ptr := n.X
for ptr.Op() == ir.OCONVNOP {
ptr = ptr.(*ir.ConvExpr).X
}
if ptr.Op() == ir.OADDR {
v.budget += 1 // undo half of default cost of ir.ODEREF+ir.OADDR
}
case ir.OCONVNOP:
// This doesn't produce code, but the children might.
v.budget++ // undo default cost
case ir.ODCLCONST, ir.OFALL, ir.OTYPE:
// These nodes don't produce code; omit from inlining budget.
return false
case ir.OIF:
n := n.(*ir.IfStmt)
if ir.IsConst(n.Cond, constant.Bool) {
// This if and the condition cost nothing.
if doList(n.Init(), v.do) {
return true
}
if ir.BoolVal(n.Cond) {
return doList(n.Body, v.do)
} else {
return doList(n.Else, v.do)
}
}
case ir.ONAME:
n := n.(*ir.Name)
if n.Class == ir.PAUTO {
v.usedLocals.Add(n)
}
case ir.OBLOCK:
// The only OBLOCK we should see at this point is an empty one.
// In any event, let the visitList(n.List()) below take care of the statements,
// and don't charge for the OBLOCK itself. The ++ undoes the -- below.
v.budget++
case ir.OMETHVALUE, ir.OSLICELIT:
v.budget-- // Hack for toolstash -cmp.
case ir.OMETHEXPR:
v.budget++ // Hack for toolstash -cmp.
case ir.OAS2:
n := n.(*ir.AssignListStmt)
// Unified IR unconditionally rewrites:
//
// a, b = f()
//
// into:
//
// DCL tmp1
// DCL tmp2
// tmp1, tmp2 = f()
// a, b = tmp1, tmp2
//
// so that it can insert implicit conversions as necessary. To
// minimize impact to the existing inlining heuristics (in
// particular, to avoid breaking the existing inlinability regress
// tests), we need to compensate for this here.
//
// See also identical logic in isBigFunc.
if init := n.Rhs[0].Init(); len(init) == 1 {
if _, ok := init[0].(*ir.AssignListStmt); ok {
// 4 for each value, because each temporary variable now
// appears 3 times (DCL, LHS, RHS), plus an extra DCL node.
//
// 1 for the extra "tmp1, tmp2 = f()" assignment statement.
v.budget += 4*int32(len(n.Lhs)) + 1
}
}
case ir.OAS:
// Special case for coverage counter updates and coverage
// function registrations. Although these correspond to real
// operations, we treat them as zero cost for the moment. This
// is primarily due to the existence of tests that are
// sensitive to inlining-- if the insertion of coverage
// instrumentation happens to tip a given function over the
// threshold and move it from "inlinable" to "not-inlinable",
// this can cause changes in allocation behavior, which can
// then result in test failures (a good example is the
// TestAllocations in crypto/ed25519).
n := n.(*ir.AssignStmt)
if n.X.Op() == ir.OINDEX && isIndexingCoverageCounter(n.X) {
return false
}
}
v.budget--
// When debugging, don't stop early, to get full cost of inlining this function
if v.budget < 0 && base.Flag.LowerM < 2 && !logopt.Enabled() {
v.reason = "too expensive"
return true
}
return ir.DoChildren(n, v.do)
}
func isBigFunc(fn *ir.Func) bool {
budget := inlineBigFunctionNodes
return ir.Any(fn, func(n ir.Node) bool {
// See logic in hairyVisitor.doNode, explaining unified IR's
// handling of "a, b = f()" assignments.
if n, ok := n.(*ir.AssignListStmt); ok && n.Op() == ir.OAS2 {
if init := n.Rhs[0].Init(); len(init) == 1 {
if _, ok := init[0].(*ir.AssignListStmt); ok {
budget += 4*len(n.Lhs) + 1
}
}
}
budget--
return budget <= 0
})
}
// inlcopylist (together with inlcopy) recursively copies a list of nodes, except
// that it keeps the same ONAME, OTYPE, and OLITERAL nodes. It is used for copying
// the body and dcls of an inlineable function.
func inlcopylist(ll []ir.Node) []ir.Node {
s := make([]ir.Node, len(ll))
for i, n := range ll {
s[i] = inlcopy(n)
}
return s
}
// inlcopy is like DeepCopy(), but does extra work to copy closures.
func inlcopy(n ir.Node) ir.Node {
var edit func(ir.Node) ir.Node
edit = func(x ir.Node) ir.Node {
switch x.Op() {
case ir.ONAME, ir.OTYPE, ir.OLITERAL, ir.ONIL:
return x
}
m := ir.Copy(x)
ir.EditChildren(m, edit)
if x.Op() == ir.OCLOSURE {
x := x.(*ir.ClosureExpr)
// Need to save/duplicate x.Func.Nname,
// x.Func.Nname.Ntype, x.Func.Dcl, x.Func.ClosureVars, and
// x.Func.Body for iexport and local inlining.
oldfn := x.Func
newfn := ir.NewFunc(oldfn.Pos())
m.(*ir.ClosureExpr).Func = newfn
newfn.Nname = ir.NewNameAt(oldfn.Nname.Pos(), oldfn.Nname.Sym())
// XXX OK to share fn.Type() ??
newfn.Nname.SetType(oldfn.Nname.Type())
newfn.Body = inlcopylist(oldfn.Body)
// Make shallow copy of the Dcl and ClosureVar slices
newfn.Dcl = append([]*ir.Name(nil), oldfn.Dcl...)
newfn.ClosureVars = append([]*ir.Name(nil), oldfn.ClosureVars...)
}
return m
}
return edit(n)
}
// InlineCalls/inlnode walks fn's statements and expressions and substitutes any
// calls made to inlineable functions. This is the external entry point.
func InlineCalls(fn *ir.Func, profile *pgo.Profile) {
savefn := ir.CurFunc
ir.CurFunc = fn
bigCaller := isBigFunc(fn)
if bigCaller && base.Flag.LowerM > 1 {
fmt.Printf("%v: function %v considered 'big'; reducing max cost of inlinees\n", ir.Line(fn), fn)
}
var inlCalls []*ir.InlinedCallExpr
var edit func(ir.Node) ir.Node
edit = func(n ir.Node) ir.Node {
return inlnode(n, bigCaller, &inlCalls, edit, profile)
}
ir.EditChildren(fn, edit)
// If we inlined any calls, we want to recursively visit their
// bodies for further inlining. However, we need to wait until
// *after* the original function body has been expanded, or else
// inlCallee can have false positives (e.g., #54632).
for len(inlCalls) > 0 {
call := inlCalls[0]
inlCalls = inlCalls[1:]
ir.EditChildren(call, edit)
}
ir.CurFunc = savefn
}
// inlnode recurses over the tree to find inlineable calls, which will
// be turned into OINLCALLs by mkinlcall. When the recursion comes
// back up will examine left, right, list, rlist, ninit, ntest, nincr,
// nbody and nelse and use one of the 4 inlconv/glue functions above
// to turn the OINLCALL into an expression, a statement, or patch it
// in to this nodes list or rlist as appropriate.
// NOTE it makes no sense to pass the glue functions down the
// recursion to the level where the OINLCALL gets created because they
// have to edit /this/ n, so you'd have to push that one down as well,
// but then you may as well do it here. so this is cleaner and
// shorter and less complicated.
// The result of inlnode MUST be assigned back to n, e.g.
//
// n.Left = inlnode(n.Left)
func inlnode(n ir.Node, bigCaller bool, inlCalls *[]*ir.InlinedCallExpr, edit func(ir.Node) ir.Node, profile *pgo.Profile) ir.Node {
if n == nil {
return n
}
switch n.Op() {
case ir.ODEFER, ir.OGO:
n := n.(*ir.GoDeferStmt)
switch call := n.Call; call.Op() {
case ir.OCALLMETH:
base.FatalfAt(call.Pos(), "OCALLMETH missed by typecheck")
case ir.OCALLFUNC:
call := call.(*ir.CallExpr)
call.NoInline = true
}
case ir.OTAILCALL:
n := n.(*ir.TailCallStmt)
n.Call.NoInline = true // Not inline a tail call for now. Maybe we could inline it just like RETURN fn(arg)?
// TODO do them here (or earlier),
// so escape analysis can avoid more heapmoves.
case ir.OCLOSURE:
return n
case ir.OCALLMETH:
base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
case ir.OCALLFUNC:
n := n.(*ir.CallExpr)
if n.X.Op() == ir.OMETHEXPR {
// Prevent inlining some reflect.Value methods when using checkptr,
// even when package reflect was compiled without it (#35073).
if meth := ir.MethodExprName(n.X); meth != nil {
s := meth.Sym()
if base.Debug.Checkptr != 0 && types.IsReflectPkg(s.Pkg) && (s.Name == "Value.UnsafeAddr" || s.Name == "Value.Pointer") {
return n
}
}
}
}
lno := ir.SetPos(n)
ir.EditChildren(n, edit)
// with all the branches out of the way, it is now time to
// transmogrify this node itself unless inhibited by the
// switch at the top of this function.
switch n.Op() {
case ir.OCALLMETH:
base.FatalfAt(n.Pos(), "OCALLMETH missed by typecheck")
case ir.OCALLFUNC:
call := n.(*ir.CallExpr)
if call.NoInline {
break
}
if base.Flag.LowerM > 3 {
fmt.Printf("%v:call to func %+v\n", ir.Line(n), call.X)
}
if ir.IsIntrinsicCall(call) {
break
}
if fn := inlCallee(call.X, profile); fn != nil && typecheck.HaveInlineBody(fn) {
n = mkinlcall(call, fn, bigCaller, inlCalls)
}
}
base.Pos = lno
return n
}
// inlCallee takes a function-typed expression and returns the underlying function ONAME
// that it refers to if statically known. Otherwise, it returns nil.
func inlCallee(fn ir.Node, profile *pgo.Profile) *ir.Func {
fn = ir.StaticValue(fn)
switch fn.Op() {
case ir.OMETHEXPR:
fn := fn.(*ir.SelectorExpr)
n := ir.MethodExprName(fn)
// Check that receiver type matches fn.X.
// TODO(mdempsky): Handle implicit dereference
// of pointer receiver argument?
if n == nil || !types.Identical(n.Type().Recv().Type, fn.X.Type()) {
return nil
}
return n.Func
case ir.ONAME:
fn := fn.(*ir.Name)
if fn.Class == ir.PFUNC {
return fn.Func
}
case ir.OCLOSURE:
fn := fn.(*ir.ClosureExpr)
c := fn.Func
CanInline(c, profile)
return c
}
return nil
}
var inlgen int
// SSADumpInline gives the SSA back end a chance to dump the function
// when producing output for debugging the compiler itself.
var SSADumpInline = func(*ir.Func) {}
// InlineCall allows the inliner implementation to be overridden.
// If it returns nil, the function will not be inlined.
var InlineCall = func(call *ir.CallExpr, fn *ir.Func, inlIndex int) *ir.InlinedCallExpr {
base.Fatalf("inline.InlineCall not overridden")
panic("unreachable")
}
// inlineCostOK returns true if call n from caller to callee is cheap enough to
// inline. bigCaller indicates that caller is a big function.
//
// If inlineCostOK returns false, it also returns the max cost that the callee
// exceeded.
func inlineCostOK(n *ir.CallExpr, caller, callee *ir.Func, bigCaller bool) (bool, int32) {
maxCost := int32(inlineMaxBudget)
if bigCaller {
// We use this to restrict inlining into very big functions.
// See issue 26546 and 17566.
maxCost = inlineBigFunctionMaxCost
}
if callee.Inl.Cost <= maxCost {
// Simple case. Function is already cheap enough.
return true, 0
}
// We'll also allow inlining of hot functions below inlineHotMaxBudget,
// but only in small functions.
lineOffset := pgo.NodeLineOffset(n, caller)
csi := pgo.CallSiteInfo{LineOffset: lineOffset, Caller: caller}
if _, ok := candHotEdgeMap[csi]; !ok {
// Cold
return false, maxCost
}
// Hot
if bigCaller {
if base.Debug.PGODebug > 0 {
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))
}
return false, maxCost
}
if callee.Inl.Cost > inlineHotMaxBudget {
return false, inlineHotMaxBudget
}
if base.Debug.PGODebug > 0 {
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))
}
return true, 0
}
// If n is a OCALLFUNC node, and fn is an ONAME node for a
// function with an inlinable body, return an OINLCALL node that can replace n.
// The returned node's Ninit has the parameter assignments, the Nbody is the
// inlined function body, and (List, Rlist) contain the (input, output)
// parameters.
// The result of mkinlcall MUST be assigned back to n, e.g.
//
// n.Left = mkinlcall(n.Left, fn, isddd)
func mkinlcall(n *ir.CallExpr, fn *ir.Func, bigCaller bool, inlCalls *[]*ir.InlinedCallExpr) ir.Node {
if fn.Inl == nil {
if logopt.Enabled() {
logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", ir.FuncName(ir.CurFunc),
fmt.Sprintf("%s cannot be inlined", ir.PkgFuncName(fn)))
}
return n
}
if ok, maxCost := inlineCostOK(n, ir.CurFunc, fn, bigCaller); !ok {
if logopt.Enabled() {
logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", ir.FuncName(ir.CurFunc),
fmt.Sprintf("cost %d of %s exceeds max caller cost %d", fn.Inl.Cost, ir.PkgFuncName(fn), maxCost))
}
return n
}
if fn == ir.CurFunc {
// Can't recursively inline a function into itself.
if logopt.Enabled() {
logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", fmt.Sprintf("recursive call to %s", ir.FuncName(ir.CurFunc)))
}
return n
}
if base.Flag.Cfg.Instrumenting && types.IsNoInstrumentPkg(fn.Sym().Pkg) {
// Runtime package must not be instrumented.
// Instrument skips runtime package. However, some runtime code can be
// inlined into other packages and instrumented there. To avoid this,
// we disable inlining of runtime functions when instrumenting.
// The example that we observed is inlining of LockOSThread,
// which lead to false race reports on m contents.
return n
}
if base.Flag.Race && types.IsNoRacePkg(fn.Sym().Pkg) {
return n
}
parent := base.Ctxt.PosTable.Pos(n.Pos()).Base().InliningIndex()
sym := fn.Linksym()
// Check if we've already inlined this function at this particular
// call site, in order to stop inlining when we reach the beginning
// of a recursion cycle again. We don't inline immediately recursive
// functions, but allow inlining if there is a recursion cycle of
// many functions. Most likely, the inlining will stop before we
// even hit the beginning of the cycle again, but this catches the
// unusual case.
for inlIndex := parent; inlIndex >= 0; inlIndex = base.Ctxt.InlTree.Parent(inlIndex) {
if base.Ctxt.InlTree.InlinedFunction(inlIndex) == sym {
if base.Flag.LowerM > 1 {
fmt.Printf("%v: cannot inline %v into %v: repeated recursive cycle\n", ir.Line(n), fn, ir.FuncName(ir.CurFunc))
}
return n
}
}
typecheck.AssertFixedCall(n)
inlIndex := base.Ctxt.InlTree.Add(parent, n.Pos(), sym, ir.FuncName(fn))
closureInitLSym := func(n *ir.CallExpr, fn *ir.Func) {
// The linker needs FuncInfo metadata for all inlined
// functions. This is typically handled by gc.enqueueFunc
// calling ir.InitLSym for all function declarations in
// typecheck.Target.Decls (ir.UseClosure adds all closures to
// Decls).
//
// However, non-trivial closures in Decls are ignored, and are
// insteaded enqueued when walk of the calling function
// discovers them.
//
// This presents a problem for direct calls to closures.
// Inlining will replace the entire closure definition with its
// body, which hides the closure from walk and thus suppresses
// symbol creation.
//
// Explicitly create a symbol early in this edge case to ensure
// we keep this metadata.
//
// TODO: Refactor to keep a reference so this can all be done
// by enqueueFunc.
if n.Op() != ir.OCALLFUNC {
// Not a standard call.
return
}
if n.X.Op() != ir.OCLOSURE {
// Not a direct closure call.
return
}
clo := n.X.(*ir.ClosureExpr)
if ir.IsTrivialClosure(clo) {
// enqueueFunc will handle trivial closures anyways.
return
}
ir.InitLSym(fn, true)
}
closureInitLSym(n, fn)
if base.Flag.GenDwarfInl > 0 {
if !sym.WasInlined() {
base.Ctxt.DwFixups.SetPrecursorFunc(sym, fn)
sym.Set(obj.AttrWasInlined, true)
}
}
if base.Flag.LowerM != 0 {
fmt.Printf("%v: inlining call to %v\n", ir.Line(n), fn)
}
if base.Flag.LowerM > 2 {
fmt.Printf("%v: Before inlining: %+v\n", ir.Line(n), n)
}
res := InlineCall(n, fn, inlIndex)
if res == nil {
base.FatalfAt(n.Pos(), "inlining call to %v failed", fn)
}
if base.Flag.LowerM > 2 {
fmt.Printf("%v: After inlining %+v\n\n", ir.Line(res), res)
}
*inlCalls = append(*inlCalls, res)
return res
}
// CalleeEffects appends any side effects from evaluating callee to init.
func CalleeEffects(init *ir.Nodes, callee ir.Node) {
for {
init.Append(ir.TakeInit(callee)...)
switch callee.Op() {
case ir.ONAME, ir.OCLOSURE, ir.OMETHEXPR:
return // done
case ir.OCONVNOP:
conv := callee.(*ir.ConvExpr)
callee = conv.X
case ir.OINLCALL:
ic := callee.(*ir.InlinedCallExpr)
init.Append(ic.Body.Take()...)
callee = ic.SingleResult()
default:
base.FatalfAt(callee.Pos(), "unexpected callee expression: %v", callee)
}
}
}
func pruneUnusedAutos(ll []*ir.Name, vis *hairyVisitor) []*ir.Name {
s := make([]*ir.Name, 0, len(ll))
for _, n := range ll {
if n.Class == ir.PAUTO {
if !vis.usedLocals.Has(n) {
continue
}
}
s = append(s, n)
}
return s
}
// numNonClosures returns the number of functions in list which are not closures.
func numNonClosures(list []*ir.Func) int {
count := 0
for _, fn := range list {
if fn.OClosure == nil {
count++
}
}
return count
}
func doList(list []ir.Node, do func(ir.Node) bool) bool {
for _, x := range list {
if x != nil {
if do(x) {
return true
}
}
}
return false
}
// isIndexingCoverageCounter returns true if the specified node 'n' is indexing
// into a coverage counter array.
func isIndexingCoverageCounter(n ir.Node) bool {
if n.Op() != ir.OINDEX {
return false
}
ixn := n.(*ir.IndexExpr)
if ixn.X.Op() != ir.ONAME || !ixn.X.Type().IsArray() {
return false
}
nn := ixn.X.(*ir.Name)
return nn.CoverageCounter()
}
// isAtomicCoverageCounterUpdate examines the specified node to
// determine whether it represents a call to sync/atomic.AddUint32 to
// increment a coverage counter.
func isAtomicCoverageCounterUpdate(cn *ir.CallExpr) bool {
if cn.X.Op() != ir.ONAME {
return false
}
name := cn.X.(*ir.Name)
if name.Class != ir.PFUNC {
return false
}
fn := name.Sym().Name
if name.Sym().Pkg.Path != "sync/atomic" ||
(fn != "AddUint32" && fn != "StoreUint32") {
return false
}
if len(cn.Args) != 2 || cn.Args[0].Op() != ir.OADDR {
return false
}
adn := cn.Args[0].(*ir.AddrExpr)
v := isIndexingCoverageCounter(adn.X)
return v
}