cmd/compile: escape package path for PGO symbol matching

Symbol names in the final executable apply escaping to the final
component of a package path (main in example.com becomes
example%2ecom.main).

ir.PkgFuncName does not perform this escaping, meaning we'd fail to
match functions that are escaped in the profile.

Add ir.LinkFuncName which does perform escaping and use it for PGO.

Fixes #59887.

Change-Id: I10634d63d99d0a6fd2f72b929ab35ea227e1336f
Reviewed-on: https://go-review.googlesource.com/c/go/+/490555
Reviewed-by: Cherry Mui <[email protected]>
Auto-Submit: Michael Pratt <[email protected]>
Run-TryBot: Michael Pratt <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: prattmic

src/cmd/compile/internal/inline/inl.go

@@ -163,7 +163,7 @@ func pgoInlineEpilogue(p *pgo.Profile, decls []ir.Node) {
 	if base.Debug.PGOInline >= 2 {
 		ir.VisitFuncsBottomUp(decls, func(list []*ir.Func, recursive bool) {
 			for _, f := range list {
-				name := ir.PkgFuncName(f)
+				name := ir.LinkFuncName(f)
 				if n, ok := p.WeightedCG.IRNodes[name]; ok {
 					p.RedirectEdges(n, inlinedCallSites)
 				}
@@ -352,7 +352,7 @@ func CanInline(fn *ir.Func, profile *pgo.Profile) {
 	// Update the budget for profile-guided inlining.
 	budget := int32(inlineMaxBudget)
 	if profile != nil {
-		if n, ok := profile.WeightedCG.IRNodes[ir.PkgFuncName(fn)]; ok {
+		if n, ok := profile.WeightedCG.IRNodes[ir.LinkFuncName(fn)]; ok {
 			if _, ok := candHotCalleeMap[n]; ok {
 				budget = int32(inlineHotMaxBudget)
 				if base.Debug.PGOInline > 0 {

src/cmd/compile/internal/ir/func.go

@@ -8,6 +8,7 @@ import (
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
+	"cmd/internal/objabi"
 	"cmd/internal/src"
 	"fmt"
 )
@@ -263,18 +264,20 @@ func (f *Func) SetWBPos(pos src.XPos) {
 	}
 }
 
-// FuncName returns the name (without the package) of the function n.
+// FuncName returns the name (without the package) of the function f.
 func FuncName(f *Func) string {
 	if f == nil || f.Nname == nil {
 		return "<nil>"
 	}
 	return f.Sym().Name
 }
 
-// PkgFuncName returns the name of the function referenced by n, with package prepended.
-// This differs from the compiler's internal convention where local functions lack a package
-// because the ultimate consumer of this is a human looking at an IDE; package is only empty
-// if the compilation package is actually the empty string.
+// PkgFuncName returns the name of the function referenced by f, with package
+// prepended.
+//
+// This differs from the compiler's internal convention where local functions
+// lack a package. This is primarily useful when the ultimate consumer of this
+// is a human looking at message.
 func PkgFuncName(f *Func) string {
 	if f == nil || f.Nname == nil {
 		return "<nil>"
@@ -285,6 +288,18 @@ func PkgFuncName(f *Func) string {
 	return pkg.Path + "." + s.Name
 }
 
+// LinkFuncName returns the name of the function f, as it will appear in the
+// symbol table of the final linked binary.
+func LinkFuncName(f *Func) string {
+	if f == nil || f.Nname == nil {
+		return "<nil>"
+	}
+	s := f.Sym()
+	pkg := s.Pkg
+
+	return objabi.PathToPrefix(pkg.Path) + "." + s.Name
+}
+
 // IsEqOrHashFunc reports whether f is type eq/hash function.
 func IsEqOrHashFunc(f *Func) bool {
 	if f == nil || f.Nname == nil {

src/cmd/compile/internal/pgo/irgraph.go

@@ -270,7 +270,7 @@ func (p *Profile) VisitIR(fn *ir.Func) {
 	if g.InEdges == nil {
 		g.InEdges = make(map[*IRNode][]*IREdge)
 	}
-	name := ir.PkgFuncName(fn)
+	name := ir.LinkFuncName(fn)
 	node := new(IRNode)
 	node.AST = fn
 	if g.IRNodes[name] == nil {
@@ -308,7 +308,7 @@ func (p *Profile) addIREdge(caller *IRNode, callername string, call ir.Node, cal
 	// Create an IRNode for the callee.
 	calleenode := new(IRNode)
 	calleenode.AST = callee
-	calleename := ir.PkgFuncName(callee)
+	calleename := ir.LinkFuncName(callee)
 
 	// Create key for NodeMapKey.
 	nodeinfo := NodeMapKey{
@@ -395,7 +395,7 @@ func (p *Profile) PrintWeightedCallGraphDOT(edgeThreshold float64) {
 	funcs := make(map[string]struct{})
 	ir.VisitFuncsBottomUp(typecheck.Target.Decls, func(list []*ir.Func, recursive bool) {
 		for _, f := range list {
-			name := ir.PkgFuncName(f)
+			name := ir.LinkFuncName(f)
 			funcs[name] = struct{}{}
 		}
 	})
@@ -405,15 +405,15 @@ func (p *Profile) PrintWeightedCallGraphDOT(edgeThreshold float64) {
 	for name := range funcs {
 		if n, ok := p.WeightedCG.IRNodes[name]; ok {
 			for _, e := range p.WeightedCG.OutEdges[n] {
-				if _, ok := nodes[ir.PkgFuncName(e.Src.AST)]; !ok {
-					nodes[ir.PkgFuncName(e.Src.AST)] = e.Src.AST
+				if _, ok := nodes[ir.LinkFuncName(e.Src.AST)]; !ok {
+					nodes[ir.LinkFuncName(e.Src.AST)] = e.Src.AST
 				}
-				if _, ok := nodes[ir.PkgFuncName(e.Dst.AST)]; !ok {
-					nodes[ir.PkgFuncName(e.Dst.AST)] = e.Dst.AST
+				if _, ok := nodes[ir.LinkFuncName(e.Dst.AST)]; !ok {
+					nodes[ir.LinkFuncName(e.Dst.AST)] = e.Dst.AST
 				}
 			}
-			if _, ok := nodes[ir.PkgFuncName(n.AST)]; !ok {
-				nodes[ir.PkgFuncName(n.AST)] = n.AST
+			if _, ok := nodes[ir.LinkFuncName(n.AST)]; !ok {
+				nodes[ir.LinkFuncName(n.AST)] = n.AST
 			}
 		}
 	}
@@ -424,16 +424,16 @@ func (p *Profile) PrintWeightedCallGraphDOT(edgeThreshold float64) {
 			nodeweight := WeightInPercentage(n.Flat, p.TotalNodeWeight)
 			color := "black"
 			if ast.Inl != nil {
-				fmt.Printf("\"%v\" [color=%v,label=\"%v,freq=%.2f,inl_cost=%d\"];\n", ir.PkgFuncName(ast), color, ir.PkgFuncName(ast), nodeweight, ast.Inl.Cost)
+				fmt.Printf("\"%v\" [color=%v,label=\"%v,freq=%.2f,inl_cost=%d\"];\n", ir.LinkFuncName(ast), color, ir.LinkFuncName(ast), nodeweight, ast.Inl.Cost)
 			} else {
-				fmt.Printf("\"%v\" [color=%v, label=\"%v,freq=%.2f\"];\n", ir.PkgFuncName(ast), color, ir.PkgFuncName(ast), nodeweight)
+				fmt.Printf("\"%v\" [color=%v, label=\"%v,freq=%.2f\"];\n", ir.LinkFuncName(ast), color, ir.LinkFuncName(ast), nodeweight)
 			}
 		}
 	}
 	// Print edges.
 	ir.VisitFuncsBottomUp(typecheck.Target.Decls, func(list []*ir.Func, recursive bool) {
 		for _, f := range list {
-			name := ir.PkgFuncName(f)
+			name := ir.LinkFuncName(f)
 			if n, ok := p.WeightedCG.IRNodes[name]; ok {
 				for _, e := range p.WeightedCG.OutEdges[n] {
 					edgepercent := WeightInPercentage(e.Weight, p.TotalEdgeWeight)
@@ -443,7 +443,7 @@ func (p *Profile) PrintWeightedCallGraphDOT(edgeThreshold float64) {
 						fmt.Printf("edge [color=black, style=solid];\n")
 					}
 
-					fmt.Printf("\"%v\" -> \"%v\" [label=\"%.2f\"];\n", ir.PkgFuncName(n.AST), ir.PkgFuncName(e.Dst.AST), edgepercent)
+					fmt.Printf("\"%v\" -> \"%v\" [label=\"%.2f\"];\n", ir.LinkFuncName(n.AST), ir.LinkFuncName(e.Dst.AST), edgepercent)
 				}
 			}
 		}