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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"
"internal/buildcfg"
"strconv"
"cmd/compile/internal/base"
"cmd/compile/internal/inline/inlheur"
"cmd/compile/internal/ir"
"cmd/compile/internal/logopt"
"cmd/compile/internal/pgoir"
"cmd/compile/internal/typecheck"
"cmd/compile/internal/types"
"cmd/internal/obj"
"cmd/internal/pgo"
)
// 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[*pgoir.IRNode]struct{})
// List of all hot call sites. CallSiteInfo.Callee is always nil.
// TODO(prattmic): Make this non-global.
candHotEdgeMap = make(map[pgoir.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 *pgoir.Profile) {
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.NamedCallEdge
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 := pgoir.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
// considered hot).
func hotNodesFromCDF(p *pgoir.Profile) (float64, []pgo.NamedCallEdge) {
cum := int64(0)
for i, n := range p.NamedEdgeMap.ByWeight {
w := p.NamedEdgeMap.Weight[n]
cum += w
if pgo.WeightInPercentage(cum, p.TotalWeight) > 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.TotalWeight), p.NamedEdgeMap.ByWeight[:i+1]
}
}
return 0, p.NamedEdgeMap.ByWeight
}
// CanInlineFuncs computes whether a batch of functions are inlinable.
func CanInlineFuncs(funcs []*ir.Func, profile *pgoir.Profile) {
if profile != nil {
PGOInlinePrologue(profile)
}
if base.Flag.LowerL == 0 {
return
}
ir.VisitFuncsBottomUp(funcs, func(funcs []*ir.Func, recursive bool) {
numfns := numNonClosures(funcs)
for _, fn := range funcs {
if !recursive || numfns > 1 {
// We allow inlining if there is no
// recursion, or the recursion cycle is
// across more than one function.
CanInline(fn, profile)
} else {
if base.Flag.LowerM > 1 && fn.OClosure == nil {
fmt.Printf("%v: cannot inline %v: recursive\n", ir.Line(fn), fn.Nname)
}
}
if inlheur.Enabled() {
analyzeFuncProps(fn, profile)
}
}
})
}
// 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.Funcs); i++ {
fn := typecheck.Target.Funcs[i]
if fn.IsHiddenClosure() {
continue
}
markLiveFuncs(fn)
}
for i := 0; i < len(typecheck.Target.Funcs); i++ {
fn := typecheck.Target.Funcs[i]
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)
}
}
}
// inlineBudget determines the max budget for function 'fn' prior to
// analyzing the hairiness of the body of 'fn'. We pass in the pgo
// profile if available (which can change the budget), also a
// 'relaxed' flag, which expands the budget slightly to allow for the
// possibility that a call to the function might have its score
// adjusted downwards. If 'verbose' is set, then print a remark where
// we boost the budget due to PGO.
func inlineBudget(fn *ir.Func, profile *pgoir.Profile, relaxed bool, verbose bool) int32 {
// 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 = inlineHotMaxBudget
if verbose {
fmt.Printf("hot-node enabled increased budget=%v for func=%v\n", budget, ir.PkgFuncName(fn))
}
}
}
}
if relaxed {
budget += inlheur.BudgetExpansion(inlineMaxBudget)
}
return budget
}
// 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 *pgoir.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.
}
// Used a "relaxed" inline budget if the new inliner is enabled.
relaxed := inlheur.Enabled()
// Compute the inline budget for this func.
budget := inlineBudget(fn, profile, relaxed, base.Debug.PGODebug > 0)
// 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 25459 for more context.
visitor := hairyVisitor{
curFunc: fn,
isBigFunc: IsBigFunc(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.Func.Dcl, &visitor),
HaveDcl: true,
CanDelayResults: canDelayResults(fn),
}
if base.Flag.LowerM != 0 || logopt.Enabled() {
noteInlinableFunc(n, fn, budget-visitor.budget)
}
}
// noteInlinableFunc issues a message to the user that the specified
// function is inlinable.
func noteInlinableFunc(n *ir.Name, fn *ir.Func, cost int32) {
if base.Flag.LowerM > 1 {
fmt.Printf("%v: can inline %v with cost %d as: %v { %v }\n", ir.Line(fn), n, cost, fn.Type(), ir.Nodes(fn.Body))
} else if base.Flag.LowerM != 0 {
fmt.Printf("%v: can inline %v\n", ir.Line(fn), n)
}
// JSON optimization log output.
if logopt.Enabled() {
logopt.LogOpt(fn.Pos(), "canInlineFunction", "inline", ir.FuncName(fn), fmt.Sprintf("cost: %d", cost))
}
}
// 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
}
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() {
if sym := 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
isBigFunc bool
budget int32
maxBudget int32
reason string
extraCallCost int32
usedLocals ir.NameSet
do func(ir.Node) bool
profile *pgoir.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
}
opSwitch:
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.Fun.Op() == ir.ONAME {
name := n.Fun.(*ir.Name)
if name.Class == ir.PFUNC {
switch fn := types.RuntimeSymName(name.Sym()); fn {
case "getcallerpc", "getcallersp":
v.reason = "call to " + fn
return true
case "throw":
v.budget -= inlineExtraThrowCost
break opSwitch
case "panicrangeexit":
cheap = true
}
// Special case for reflect.noescape. It does just type
// conversions to appease the escape analysis, and doesn't
// generate code.
if types.ReflectSymName(name.Sym()) == "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.Fun.Op() == ir.OMETHEXPR {
if meth := ir.MethodExprName(n.Fun); meth != nil {
if fn := meth.Func; fn != nil {
s := fn.Sym()
if types.RuntimeSymName(s) == "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 n.Fun.Op() == ir.ONAME {
name := n.Fun.(*ir.Name)
if name.Class == ir.PFUNC {
// Special case: on architectures that can do unaligned loads,
// explicitly mark internal/byteorder 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 && name.Sym().Pkg.Path == "internal/byteorder" {
switch name.Sym().Name {
case "LeUint64", "LeUint32", "LeUint16",
"BeUint64", "BeUint32", "BeUint16",
"LePutUint64", "LePutUint32", "LePutUint16",
"BePutUint64", "BePutUint32", "BePutUint16",
"LeAppendUint64", "LeAppendUint32", "LeAppendUint16",
"BeAppendUint64", "BeAppendUint32", "BeAppendUint16":
cheap = true
}
}
}
}
if cheap {
break // treat like any other node, that is, cost of 1
}
if ir.IsIntrinsicCall(n) {
// Treat like any other node.
break
}
if callee := inlCallee(v.curFunc, n.Fun, v.profile); callee != nil && typecheck.HaveInlineBody(callee) {
// Check whether we'd actually inline this call. Set
// log == false since we aren't actually doing inlining
// yet.
if ok, _ := canInlineCallExpr(v.curFunc, n, callee, v.isBigFunc, false); ok {
// mkinlcall would inline this call [1], so use
// the cost of the inline body as the cost of
// the call, as that is what will actually
// appear in the code.
//
// [1] This is almost a perfect match to the
// mkinlcall logic, except that
// canInlineCallExpr considers inlining cycles
// by looking at what has already been inlined.
// Since we haven't done any inlining yet we
// will miss those.
v.budget -= callee.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:
base.FatalfAt(n.Pos(), "ORECOVER missed typecheck")
case ir.ORECOVERFP:
// 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.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.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 len(n.Rhs) > 0 {
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)
}
// IsBigFunc reports whether fn is a "big" function.
//
// Note: The criteria for "big" is heuristic and subject to change.
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 && len(n.Rhs) > 0 {
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
})
}
// TryInlineCall returns an inlined call expression for call, or nil
// if inlining is not possible.
func TryInlineCall(callerfn *ir.Func, call *ir.CallExpr, bigCaller bool, profile *pgoir.Profile) *ir.InlinedCallExpr {
if base.Flag.LowerL == 0 {
return nil
}
if call.Op() != ir.OCALLFUNC {
return nil
}
if call.GoDefer || call.NoInline {
return nil
}
// Prevent inlining some reflect.Value methods when using checkptr,
// even when package reflect was compiled without it (#35073).
if base.Debug.Checkptr != 0 && call.Fun.Op() == ir.OMETHEXPR {
if method := ir.MethodExprName(call.Fun); method != nil {
switch types.ReflectSymName(method.Sym()) {
case "Value.UnsafeAddr", "Value.Pointer":
return nil
}
}
}
if base.Flag.LowerM > 3 {
fmt.Printf("%v:call to func %+v\n", ir.Line(call), call.Fun)
}
if ir.IsIntrinsicCall(call) {
return nil
}
if fn := inlCallee(callerfn, call.Fun, profile); fn != nil && typecheck.HaveInlineBody(fn) {
return mkinlcall(callerfn, call, fn, bigCaller)
}
return nil
}
// 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(caller *ir.Func, fn ir.Node, profile *pgoir.Profile) (res *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
if len(c.ClosureVars) != 0 && c.ClosureVars[0].Outer.Curfn != caller {
return nil // inliner doesn't support inlining across closure frames
}
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(callerfn *ir.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.
//
// In addition to the "cost OK" boolean, it also returns the "max
// cost" limit used to make the decision (which may differ depending
// on func size), and the score assigned to this specific callsite.
func inlineCostOK(n *ir.CallExpr, caller, callee *ir.Func, bigCaller bool) (bool, int32, int32) {
maxCost := int32(inlineMaxBudget)
if bigCaller {
// We use this to restrict inlining into very big functions.
// See issue 26546 and 17566.
maxCost = inlineBigFunctionMaxCost
}
metric := callee.Inl.Cost
if inlheur.Enabled() {
score, ok := inlheur.GetCallSiteScore(caller, n)
if ok {
metric = int32(score)
}
}
if metric <= maxCost {
// Simple case. Function is already cheap enough.
return true, 0, metric
}
// We'll also allow inlining of hot functions below inlineHotMaxBudget,
// but only in small functions.
lineOffset := pgoir.NodeLineOffset(n, caller)
csi := pgoir.CallSiteInfo{LineOffset: lineOffset, Caller: caller}
if _, ok := candHotEdgeMap[csi]; !ok {
// Cold
return false, maxCost, metric
}
// 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, metric
}
if metric > inlineHotMaxBudget {
return false, inlineHotMaxBudget, metric
}
if !base.PGOHash.MatchPosWithInfo(n.Pos(), "inline", nil) {
// De-selected by PGO Hash.
return false, maxCost, metric
}
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, metric
}
// canInlineCallExpr returns true if the call n from caller to callee
// can be inlined, plus the score computed for the call expr in
// question. bigCaller indicates that caller is a big function. log
// indicates that the 'cannot inline' reason should be logged.
//
// Preconditions: CanInline(callee) has already been called.
func canInlineCallExpr(callerfn *ir.Func, n *ir.CallExpr, callee *ir.Func, bigCaller bool, log bool) (bool, int32) {
if callee.Inl == nil {
// callee is never inlinable.
if log && logopt.Enabled() {
logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", ir.FuncName(callerfn),
fmt.Sprintf("%s cannot be inlined", ir.PkgFuncName(callee)))
}
return false, 0
}
ok, maxCost, callSiteScore := inlineCostOK(n, callerfn, callee, bigCaller)
if !ok {
// callee cost too high for this call site.
if log && logopt.Enabled() {
logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", ir.FuncName(callerfn),
fmt.Sprintf("cost %d of %s exceeds max caller cost %d", callee.Inl.Cost, ir.PkgFuncName(callee), maxCost))
}
return false, 0
}
if callee == callerfn {
// Can't recursively inline a function into itself.
if log && logopt.Enabled() {
logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", fmt.Sprintf("recursive call to %s", ir.FuncName(callerfn)))
}
return false, 0
}
if base.Flag.Cfg.Instrumenting && types.IsNoInstrumentPkg(callee.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.
if log && logopt.Enabled() {
logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", ir.FuncName(callerfn),
fmt.Sprintf("call to runtime function %s in instrumented build", ir.PkgFuncName(callee)))
}
return false, 0
}
if base.Flag.Race && types.IsNoRacePkg(callee.Sym().Pkg) {
if log && logopt.Enabled() {
logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", ir.FuncName(callerfn),
fmt.Sprintf(`call to into "no-race" package function %s in race build`, ir.PkgFuncName(callee)))
}
return false, 0
}
// 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.
parent := base.Ctxt.PosTable.Pos(n.Pos()).Base().InliningIndex()
sym := callee.Linksym()
for inlIndex := parent; inlIndex >= 0; inlIndex = base.Ctxt.InlTree.Parent(inlIndex) {
if base.Ctxt.InlTree.InlinedFunction(inlIndex) == sym {
if log {
if base.Flag.LowerM > 1 {
fmt.Printf("%v: cannot inline %v into %v: repeated recursive cycle\n", ir.Line(n), callee, ir.FuncName(callerfn))
}
if logopt.Enabled() {
logopt.LogOpt(n.Pos(), "cannotInlineCall", "inline", ir.FuncName(callerfn),
fmt.Sprintf("repeated recursive cycle to %s", ir.PkgFuncName(callee)))
}
}
return false, 0
}
}
return true, callSiteScore
}
// mkinlcall returns an OINLCALL node that can replace OCALLFUNC n, or
// nil if it cannot be inlined. callerfn is the function that contains
// n, and fn is the function being called.
//
// The result of mkinlcall MUST be assigned back to n, e.g.
//
// n.Left = mkinlcall(n.Left, fn, isddd)
func mkinlcall(callerfn *ir.Func, n *ir.CallExpr, fn *ir.Func, bigCaller bool) *ir.InlinedCallExpr {
ok, score := canInlineCallExpr(callerfn, n, fn, bigCaller, true)
if !ok {
return nil
}
typecheck.AssertFixedCall(n)
parent := base.Ctxt.PosTable.Pos(n.Pos()).Base().InliningIndex()
sym := fn.Linksym()
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
// instead 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.Fun.Op() != ir.OCLOSURE {
// Not a direct closure call.
return
}
clo := n.Fun.(*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 {
if buildcfg.Experiment.NewInliner {
fmt.Printf("%v: inlining call to %v with score %d\n",
ir.Line(n), fn, score)
} else {
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(callerfn, 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)
}
if inlheur.Enabled() {
inlheur.UpdateCallsiteTable(callerfn, n, 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) {
// TODO(mdempsky): Simplify code after confident that this
// never happens anymore.
base.FatalfAt(n.Pos(), "unused auto: %v", 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)
// CoverageAuxVar implies either a coverage counter or a package
// ID; since the cover tool never emits code to index into ID vars
// this is effectively testing whether nn is a coverage counter.
return nn.CoverageAuxVar()
}
// 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.Fun.Op() != ir.ONAME {
return false
}
name := cn.Fun.(*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
}
func PostProcessCallSites(profile *pgoir.Profile) {
if base.Debug.DumpInlCallSiteScores != 0 {
budgetCallback := func(fn *ir.Func, prof *pgoir.Profile) (int32, bool) {
v := inlineBudget(fn, prof, false, false)
return v, v == inlineHotMaxBudget
}
inlheur.DumpInlCallSiteScores(profile, budgetCallback)
}
}
func analyzeFuncProps(fn *ir.Func, p *pgoir.Profile) {
canInline := func(fn *ir.Func) { CanInline(fn, p) }
budgetForFunc := func(fn *ir.Func) int32 {
return inlineBudget(fn, p, true, false)
}
inlheur.AnalyzeFunc(fn, canInline, budgetForFunc, inlineMaxBudget)
}