go/types/objectpath: reduce allocations with sync.Pool

go/types/objectpath/objectpath.go

@@ -28,11 +28,30 @@ import (
 	"go/types"
 	"strconv"
 	"strings"
+	"sync"
 
 	"golang.org/x/tools/internal/aliases"
 	"golang.org/x/tools/internal/typesinternal"
 )
 
+// pathBufPool reduces allocations by reusing path buffers.
+var pathBufPool = sync.Pool{
+	New: func() interface{} {
+		buf := make([]byte, 0, 128)
+		return &buf
+	},
+}
+
+// smallInts contains pre-computed string representations of integers 0-99
+// to avoid strconv.AppendInt allocations for common method/field indices.
+var smallInts [100]string
+
+func init() {
+	for i := range smallInts {
+		smallInts[i] = strconv.Itoa(i)
+	}
+}
+
 // TODO(adonovan): think about generic aliases.
 
 // A Path is an opaque name that identifies a types.Object
@@ -268,7 +287,12 @@ func (enc *Encoder) For(obj types.Object) (Path, error) {
 	// In the presence of path aliases, these give
 	// the best paths because non-types may
 	// refer to types, but not the reverse.
-	empty := make([]byte, 0, 48) // initial space
+
+	// Get a buffer from the pool to reduce allocations.
+	bufPtr := pathBufPool.Get().(*[]byte)
+	empty := (*bufPtr)[:0]
+	defer pathBufPool.Put(bufPtr)
+
 	objs := enc.scopeObjects(scope)
 	for _, o := range objs {
 		tname, ok := o.(*types.TypeName)
@@ -344,7 +368,12 @@ func (enc *Encoder) For(obj types.Object) (Path, error) {
 
 func appendOpArg(path []byte, op byte, arg int) []byte {
 	path = append(path, op)
-	path = strconv.AppendInt(path, int64(arg), 10)
+	// Use pre-computed strings for small integers to avoid allocations.
+	if arg >= 0 && arg < len(smallInts) {
+		path = append(path, smallInts[arg]...)
+	} else {
+		path = strconv.AppendInt(path, int64(arg), 10)
+	}
 	return path
 }
 
@@ -443,6 +472,16 @@ func (enc *Encoder) concreteMethod(meth *types.Func) (Path, bool) {
 	// panic(fmt.Sprintf("couldn't find method %s on type %s; methods: %#v", meth, named, enc.namedMethods(named)))
 }
 
+// finderPool reduces allocations by reusing finder structs.
+var finderPool = sync.Pool{
+	New: func() interface{} {
+		return &finder{
+			seenTParamNames: make(map[*types.TypeName]bool),
+			seenMethods:     make(map[*types.Func]bool),
+		}
+	},
+}
+
 // find finds obj within type T, returning the path to it, or nil if not found.
 //
 // The seen map is used to short circuit cycles through type parameters. If
@@ -455,7 +494,14 @@ func (enc *Encoder) concreteMethod(meth *types.Func) (Path, bool) {
 //
 // See golang/go#68046 for details.
 func find(obj types.Object, T types.Type, path []byte) []byte {
-	return (&finder{obj: obj}).find(T, path)
+	f := finderPool.Get().(*finder)
+	f.obj = obj
+	// Clear maps but keep allocated backing storage
+	clear(f.seenTParamNames)
+	clear(f.seenMethods)
+	result := f.find(T, path)
+	finderPool.Put(f)
+	return result
 }
 
 // finder closes over search state for a call to find.
@@ -561,7 +607,13 @@ func (f *finder) find(T types.Type, path []byte) []byte {
 }
 
 func findTypeParam(obj types.Object, list *types.TypeParamList, path []byte, op byte) []byte {
-	return (&finder{obj: obj}).findTypeParam(list, path, op)
+	f := finderPool.Get().(*finder)
+	f.obj = obj
+	clear(f.seenTParamNames)
+	clear(f.seenMethods)
+	result := f.findTypeParam(list, path, op)
+	finderPool.Put(f)
+	return result
 }
 
 func (f *finder) findTypeParam(list *types.TypeParamList, path []byte, op byte) []byte {

go/types/objectpath/objectpath_bench_test.go

@@ -0,0 +1,188 @@
+// Copyright 2025 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.
+
+package objectpath_test
+
+import (
+	"go/ast"
+	"go/build"
+	"go/importer"
+	"go/parser"
+	"go/token"
+	"go/types"
+	"path/filepath"
+	"testing"
+
+	"golang.org/x/tools/go/types/objectpath"
+)
+
+// testData holds pre-loaded type information for benchmarks.
+var testData struct {
+	pkg     *types.Package
+	objects []types.Object
+	methods []*types.Func
+	fields  []*types.Var
+	paths   []objectpath.Path
+}
+
+func init() {
+	// Load net/http for realistic benchmarks - it has interfaces,
+	// structs with many fields, and methods.
+	pkg, err := build.Default.Import("net/http", "", 0)
+	if err != nil {
+		panic("failed to import net/http: " + err.Error())
+	}
+
+	fset := token.NewFileSet()
+	var files []*ast.File
+	for _, filename := range pkg.GoFiles {
+		f, err := parser.ParseFile(fset, filepath.Join(pkg.Dir, filename), nil, 0)
+		if err != nil {
+			panic("failed to parse: " + err.Error())
+		}
+		files = append(files, f)
+	}
+
+	conf := types.Config{Importer: importer.Default()}
+	tpkg, err := conf.Check("net/http", fset, files, nil)
+	if err != nil {
+		panic("failed to type-check: " + err.Error())
+	}
+
+	testData.pkg = tpkg
+	scope := tpkg.Scope()
+
+	// Collect diverse objects for comprehensive benchmarking
+	for _, name := range scope.Names() {
+		obj := scope.Lookup(name)
+		testData.objects = append(testData.objects, obj)
+
+		// Collect methods from named types
+		if named, ok := obj.Type().(*types.Named); ok {
+			for i := 0; i < named.NumMethods(); i++ {
+				m := named.Method(i)
+				testData.methods = append(testData.methods, m)
+				testData.objects = append(testData.objects, m)
+			}
+
+			// Collect fields from struct types
+			if st, ok := named.Underlying().(*types.Struct); ok {
+				for i := 0; i < st.NumFields(); i++ {
+					f := st.Field(i)
+					testData.fields = append(testData.fields, f)
+					testData.objects = append(testData.objects, f)
+				}
+			}
+		}
+	}
+
+	// Pre-encode paths for decode benchmarks
+	enc := new(objectpath.Encoder)
+	for _, obj := range testData.objects {
+		if path, err := enc.For(obj); err == nil {
+			testData.paths = append(testData.paths, path)
+		}
+	}
+}
+
+// BenchmarkEncoderFor measures the cost of encoding object paths.
+func BenchmarkEncoderFor(b *testing.B) {
+	if len(testData.objects) == 0 {
+		b.Skip("no test objects available")
+	}
+	for b.Loop() {
+		enc := new(objectpath.Encoder)
+		for _, obj := range testData.objects {
+			_, _ = enc.For(obj)
+		}
+	}
+}
+
+// BenchmarkEncoderFor_SingleEncoder measures encoding with encoder reuse.
+func BenchmarkEncoderFor_SingleEncoder(b *testing.B) {
+	if len(testData.objects) == 0 {
+		b.Skip("no test objects available")
+	}
+	enc := new(objectpath.Encoder)
+	for b.Loop() {
+		for _, obj := range testData.objects {
+			_, _ = enc.For(obj)
+		}
+	}
+}
+
+// BenchmarkEncoderFor_Methods focuses on method path encoding.
+func BenchmarkEncoderFor_Methods(b *testing.B) {
+	if len(testData.methods) == 0 {
+		b.Skip("no methods available")
+	}
+	for b.Loop() {
+		enc := new(objectpath.Encoder)
+		for _, m := range testData.methods {
+			_, _ = enc.For(m)
+		}
+	}
+}
+
+// BenchmarkEncoderFor_Fields focuses on struct field path encoding.
+func BenchmarkEncoderFor_Fields(b *testing.B) {
+	if len(testData.fields) == 0 {
+		b.Skip("no fields available")
+	}
+	for b.Loop() {
+		enc := new(objectpath.Encoder)
+		for _, f := range testData.fields {
+			_, _ = enc.For(f)
+		}
+	}
+}
+
+// BenchmarkObject measures decoding paths back to objects.
+func BenchmarkObject(b *testing.B) {
+	if len(testData.paths) == 0 {
+		b.Skip("no paths available")
+	}
+	for b.Loop() {
+		for _, path := range testData.paths {
+			_, _ = objectpath.Object(testData.pkg, path)
+		}
+	}
+}
+
+// BenchmarkRoundTrip measures encode + decode cycles.
+func BenchmarkRoundTrip(b *testing.B) {
+	if len(testData.objects) == 0 {
+		b.Skip("no test objects available")
+	}
+	for b.Loop() {
+		enc := new(objectpath.Encoder)
+		for _, obj := range testData.objects {
+			path, err := enc.For(obj)
+			if err != nil {
+				continue
+			}
+			_, _ = objectpath.Object(testData.pkg, path)
+		}
+	}
+}
+
+// BenchmarkEncoderFor_Repeated measures many sequential encoding calls.
+func BenchmarkEncoderFor_Repeated(b *testing.B) {
+	if len(testData.objects) == 0 {
+		b.Skip("no test objects available")
+	}
+	// Use a subset to get more iterations
+	objects := testData.objects
+	if len(objects) > 100 {
+		objects = objects[:100]
+	}
+	for b.Loop() {
+		enc := new(objectpath.Encoder)
+		for j := 0; j < 10; j++ {
+			for _, obj := range objects {
+				_, _ = enc.For(obj)
+			}
+		}
+	}
+}