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go/types, types2: eliminate methodList in favor of just using Named.mu

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In order to clean up context after fully expanding a type (in subsequent
CLs), we must use a common mutex. Eliminate the lazy methodList type,
which keeps a sync.Once per method, in favor of Named.mu.

Updates #52728

Change-Id: I2d13319276df1330ee53046ef1823b0167a258d8
Reviewed-on: https://go-review.googlesource.com/c/go/+/404883
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
This commit is contained in:
Robert Findley 2022-05-07 18:59:14 -04:00
parent 846f971daa
commit 1323b0e8f0
10 changed files with 112 additions and 289 deletions
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8
src/cmd/compile/internal/types2/decl.go
View File

@ -646,8 +646,8 @@ func (check *Checker) collectMethods(obj *TypeName) {
// Checker.Files may be called multiple times; additional package files
// may add methods to already type-checked types. Add pre-existing methods
// so that we can detect redeclarations.
for i := 0; i < base.methods.Len(); i++ {
m := base.methods.At(i, nil)
for i := 0; i < base.NumMethods(); i++ {
m := base.Method(i)
assert(m.name != "_")
assert(mset.insert(m) == nil)
}
@ -679,8 +679,8 @@ func (check *Checker) collectMethods(obj *TypeName) {
func (check *Checker) checkFieldUniqueness(base *Named) {
if t, _ := base.under().(*Struct); t != nil {
var mset objset
for i := 0; i < base.methods.Len(); i++ {
m := base.methods.At(i, nil)
for i := 0; i < base.NumMethods(); i++ {
m := base.Method(i)
assert(m.name != "_")
assert(mset.insert(m) == nil)
}

79
src/cmd/compile/internal/types2/methodlist.go
View File

@ -1,79 +0,0 @@
// Copyright 2022 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 types2
import "sync"
// methodList holds a list of methods that may be lazily resolved by a provided
// resolution method.
type methodList struct {
methods []*Func
// guards synchronizes the instantiation of lazy methods. For lazy method
// lists, guards is non-nil and of the length passed to newLazyMethodList.
// For non-lazy method lists, guards is nil.
guards *[]sync.Once
}
// newMethodList creates a non-lazy method list holding the given methods.
func newMethodList(methods []*Func) *methodList {
return &methodList{methods: methods}
}
// newLazyMethodList creates a lazy method list of the given length. Methods
// may be resolved lazily for a given index by providing a resolver function.
func newLazyMethodList(length int) *methodList {
guards := make([]sync.Once, length)
return &methodList{
methods: make([]*Func, length),
guards: &guards,
}
}
// isLazy reports whether the receiver is a lazy method list.
func (l *methodList) isLazy() bool {
return l != nil && l.guards != nil
}
// Add appends a method to the method list if not not already present. Add
// panics if the receiver is lazy.
func (l *methodList) Add(m *Func) {
assert(!l.isLazy())
if i, _ := lookupMethod(l.methods, m.pkg, m.name, false); i < 0 {
l.methods = append(l.methods, m)
}
}
// Lookup looks up the method identified by pkg and name in the receiver.
// Lookup panics if the receiver is lazy. If foldCase is true, method names
// are considered equal if they are equal with case folding.
func (l *methodList) Lookup(pkg *Package, name string, foldCase bool) (int, *Func) {
assert(!l.isLazy())
if l == nil {
return -1, nil
}
return lookupMethod(l.methods, pkg, name, foldCase)
}
// Len returns the length of the method list.
func (l *methodList) Len() int {
if l == nil {
return 0
}
return len(l.methods)
}
// At returns the i'th method of the method list. At panics if i is out of
// bounds, or if the receiver is lazy and resolve is nil.
func (l *methodList) At(i int, resolve func() *Func) *Func {
if !l.isLazy() {
return l.methods[i]
}
assert(resolve != nil)
(*l.guards)[i].Do(func() {
l.methods[i] = resolve()
})
return l.methods[i]
}

40
src/cmd/compile/internal/types2/methodlist_test.go
View File

@ -1,40 +0,0 @@
// Copyright 2022 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 types2
import (
"testing"
)
func TestLazyMethodList(t *testing.T) {
l := newLazyMethodList(2)
if got := l.Len(); got != 2 {
t.Fatalf("Len() = %d, want 2", got)
}
f0 := NewFunc(nopos, nil, "f0", nil)
f1 := NewFunc(nopos, nil, "f1", nil)
// Verify that methodList.At is idempotent, by calling it repeatedly with a
// resolve func that returns different pointer values (f0 or f1).
steps := []struct {
index int
resolve *Func // the *Func returned by the resolver
want *Func // the actual *Func returned by methodList.At
}{
{0, f0, f0},
{0, f1, f0},
{1, f1, f1},
{1, f0, f1},
}
for i, step := range steps {
got := l.At(step.index, func() *Func { return step.resolve })
if got != step.want {
t.Errorf("step %d: At(%d, ...) = %s, want %s", i, step.index, got.Name(), step.want.Name())
}
}
}

69
src/cmd/compile/internal/types2/named.go
View File

@ -96,14 +96,16 @@ type Named struct {
underlying Type // possibly a *Named during setup; never a *Named once set up completely
tparams *TypeParamList // type parameters, or nil
// methods declared for this type (not the method set of this type).
// methods declared for this type (not the method set of this type)
// Signatures are type-checked lazily.
// For non-instantiated types, this is a fully populated list of methods. For
// instantiated types, this is a 'lazy' list, and methods are individually
// expanded when they are first accessed.
methods *methodList
// instantiated types, methods are individually expanded when they are first
// accessed.
methods []*Func
// number of expanded methods (only valid for instantiated named types)
expandedMethods int // expandedMethods <= len(orig.methods)
// loader may be provided to lazily load type parameters, underlying, and methods.
// loader may be provided to lazily load type parameters, underlying type, and methods.
loader func(*Named) (tparams []*TypeParam, underlying Type, methods []*Func)
}
@ -112,7 +114,8 @@ type namedState uint32
const (
unresolved namedState = iota // tparams, underlying type and methods might be unavailable
resolved
resolved // resolve has run; methods might be incomplete (for instances)
complete // all data is known
)
// NewNamed returns a new named type for the given type name, underlying type, and associated methods.
@ -122,7 +125,7 @@ func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
if _, ok := underlying.(*Named); ok {
panic("underlying type must not be *Named")
}
return (*Checker)(nil).newNamed(obj, nil, underlying, newMethodList(methods))
return (*Checker)(nil).newNamed(obj, nil, underlying, methods)
}
// resolve resolves the type parameters, methods, and underlying type of n.
@ -156,8 +159,12 @@ func (n *Named) resolve(ctxt *Context) *Named {
n.tparams = n.orig.tparams
n.underlying = underlying
n.fromRHS = n.orig.fromRHS // for cycle detection
n.methods = newLazyMethodList(n.orig.methods.Len())
if len(n.orig.methods) == 0 {
n.setState(complete)
} else {
n.setState(resolved)
}
return n
}
@ -170,17 +177,18 @@ func (n *Named) resolve(ctxt *Context) *Named {
// also make the API more future-proof towards further extensions.
if n.loader != nil {
assert(n.underlying == nil)
assert(n.TypeArgs().Len() == 0) // instances are created by instantiation, in which case n.loader is nil
tparams, underlying, methods := n.loader(n)
n.tparams = bindTParams(tparams)
n.underlying = underlying
n.fromRHS = underlying // for cycle detection
n.methods = newMethodList(methods)
n.methods = methods
n.loader = nil
}
n.setState(resolved)
n.setState(complete)
return n
}
@ -196,7 +204,7 @@ func (n *Named) setState(state namedState) {
}
// newNamed is like NewNamed but with a *Checker receiver and additional orig argument.
func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, methods *methodList) *Named {
func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, methods []*Func) *Named {
typ := &Named{check: check, obj: obj, orig: orig, fromRHS: underlying, underlying: underlying, methods: methods}
if typ.orig == nil {
typ.orig = typ
@ -262,14 +270,38 @@ func (t *Named) TypeArgs() *TypeList { return t.targs }
// For an ordinary or instantiated type t, the receiver base type of these
// methods will be the named type t. For an uninstantiated generic type t, each
// method receiver will be instantiated with its receiver type parameters.
func (t *Named) NumMethods() int { return t.resolve(nil).methods.Len() }
func (t *Named) NumMethods() int { return len(t.orig.resolve(nil).methods) }
// Method returns the i'th method of named type t for 0 <= i < t.NumMethods().
func (t *Named) Method(i int) *Func {
t.resolve(nil)
return t.methods.At(i, func() *Func {
return t.expandMethod(i)
})
if t.state() >= complete {
return t.methods[i]
}
assert(t.TypeArgs().Len() > 0) // only instances should have incomplete methods
t.mu.Lock()
defer t.mu.Unlock()
if len(t.methods) != len(t.orig.methods) {
assert(len(t.methods) == 0)
t.methods = make([]*Func, len(t.orig.methods))
}
if t.methods[i] == nil {
t.methods[i] = t.expandMethod(i)
t.expandedMethods++
// Check if we've created all methods at this point. If we have, mark the
// type as fully expanded.
if t.expandedMethods == len(t.orig.methods) {
t.setState(complete)
}
}
return t.methods[i]
}
// expandMethod substitutes type arguments in the i'th method for an
@ -351,10 +383,9 @@ func (t *Named) SetUnderlying(underlying Type) {
func (t *Named) AddMethod(m *Func) {
assert(t.targs.Len() == 0)
t.resolve(nil)
if t.methods == nil {
t.methods = newMethodList(nil)
if i, _ := lookupMethod(t.methods, m.pkg, m.name, false); i < 0 {
t.methods = append(t.methods, m)
}
t.methods.Add(m)
}
func (t *Named) Underlying() Type { return t.resolve(nil).underlying }
@ -462,7 +493,7 @@ func (n *Named) lookupMethod(pkg *Package, name string, foldCase bool) (int, *Fu
// If n is an instance, we may not have yet instantiated all of its methods.
// Look up the method index in orig, and only instantiate method at the
// matching index (if any).
i, _ := n.orig.methods.Lookup(pkg, name, foldCase)
i, _ := lookupMethod(n.orig.methods, pkg, name, foldCase)
if i < 0 {
return -1, nil
}

2
src/cmd/compile/internal/types2/sizeof_test.go
View File

@ -31,7 +31,7 @@ func TestSizeof(t *testing.T) {
{Interface{}, 40, 80},
{Map{}, 16, 32},
{Chan{}, 12, 24},
{Named{}, 56, 104},
{Named{}, 68, 128},
{TypeParam{}, 28, 48},
{term{}, 12, 24},

8
src/go/types/decl.go
View File

@ -722,8 +722,8 @@ func (check *Checker) collectMethods(obj *TypeName) {
// Checker.Files may be called multiple times; additional package files
// may add methods to already type-checked types. Add pre-existing methods
// so that we can detect redeclarations.
for i := 0; i < base.methods.Len(); i++ {
m := base.methods.At(i, nil)
for i := 0; i < base.NumMethods(); i++ {
m := base.Method(i)
assert(m.name != "_")
assert(mset.insert(m) == nil)
}
@ -749,8 +749,8 @@ func (check *Checker) collectMethods(obj *TypeName) {
func (check *Checker) checkFieldUniqueness(base *Named) {
if t, _ := base.under().(*Struct); t != nil {
var mset objset
for i := 0; i < base.methods.Len(); i++ {
m := base.methods.At(i, nil)
for i := 0; i < base.NumMethods(); i++ {
m := base.Method(i)
assert(m.name != "_")
assert(mset.insert(m) == nil)
}

79
src/go/types/methodlist.go
View File

@ -1,79 +0,0 @@
// Copyright 2022 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 types
import "sync"
// methodList holds a list of methods that may be lazily resolved by a provided
// resolution method.
type methodList struct {
methods []*Func
// guards synchronizes the instantiation of lazy methods. For lazy method
// lists, guards is non-nil and of the length passed to newLazyMethodList.
// For non-lazy method lists, guards is nil.
guards *[]sync.Once
}
// newMethodList creates a non-lazy method list holding the given methods.
func newMethodList(methods []*Func) *methodList {
return &methodList{methods: methods}
}
// newLazyMethodList creates a lazy method list of the given length. Methods
// may be resolved lazily for a given index by providing a resolver function.
func newLazyMethodList(length int) *methodList {
guards := make([]sync.Once, length)
return &methodList{
methods: make([]*Func, length),
guards: &guards,
}
}
// isLazy reports whether the receiver is a lazy method list.
func (l *methodList) isLazy() bool {
return l != nil && l.guards != nil
}
// Add appends a method to the method list if not not already present. Add
// panics if the receiver is lazy.
func (l *methodList) Add(m *Func) {
assert(!l.isLazy())
if i, _ := lookupMethod(l.methods, m.pkg, m.name, false); i < 0 {
l.methods = append(l.methods, m)
}
}
// Lookup looks up the method identified by pkg and name in the receiver.
// Lookup panics if the receiver is lazy. If foldCase is true, method names
// are considered equal if they are equal with case folding.
func (l *methodList) Lookup(pkg *Package, name string, foldCase bool) (int, *Func) {
assert(!l.isLazy())
if l == nil {
return -1, nil
}
return lookupMethod(l.methods, pkg, name, foldCase)
}
// Len returns the length of the method list.
func (l *methodList) Len() int {
if l == nil {
return 0
}
return len(l.methods)
}
// At returns the i'th method of the method list. At panics if i is out of
// bounds, or if the receiver is lazy and resolve is nil.
func (l *methodList) At(i int, resolve func() *Func) *Func {
if !l.isLazy() {
return l.methods[i]
}
assert(resolve != nil)
(*l.guards)[i].Do(func() {
l.methods[i] = resolve()
})
return l.methods[i]
}

41
src/go/types/methodlist_test.go
View File

@ -1,41 +0,0 @@
// Copyright 2022 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 types
import (
"go/token"
"testing"
)
func TestLazyMethodList(t *testing.T) {
l := newLazyMethodList(2)
if got := l.Len(); got != 2 {
t.Fatalf("Len() = %d, want 2", got)
}
f0 := NewFunc(token.NoPos, nil, "f0", nil)
f1 := NewFunc(token.NoPos, nil, "f1", nil)
// Verify that methodList.At is idempotent, by calling it repeatedly with a
// resolve func that returns different pointer values (f0 or f1).
steps := []struct {
index int
resolve *Func // the *Func returned by the resolver
want *Func // the actual *Func returned by methodList.At
}{
{0, f0, f0},
{0, f1, f0},
{1, f1, f1},
{1, f0, f1},
}
for i, step := range steps {
got := l.At(step.index, func() *Func { return step.resolve })
if got != step.want {
t.Errorf("step %d: At(%d, ...) = %s, want %s", i, step.index, got.Name(), step.want.Name())
}
}
}

69
src/go/types/named.go
View File

@ -96,14 +96,16 @@ type Named struct {
underlying Type // possibly a *Named during setup; never a *Named once set up completely
tparams *TypeParamList // type parameters, or nil
// methods declared for this type (not the method set of this type).
// methods declared for this type (not the method set of this type)
// Signatures are type-checked lazily.
// For non-instantiated types, this is a fully populated list of methods. For
// instantiated types, this is a 'lazy' list, and methods are individually
// expanded when they are first accessed.
methods *methodList
// instantiated types, methods are individually expanded when they are first
// accessed.
methods []*Func
// number of expanded methods (only valid for instantiated named types)
expandedMethods int // expandedMethods <= len(orig.methods)
// loader may be provided to lazily load type parameters, underlying, and methods.
// loader may be provided to lazily load type parameters, underlying type, and methods.
loader func(*Named) (tparams []*TypeParam, underlying Type, methods []*Func)
}
@ -112,7 +114,8 @@ type namedState uint32
const (
unresolved namedState = iota // tparams, underlying type and methods might be unavailable
resolved
resolved // resolve has run; methods might be incomplete (for instances)
complete // all data is known
)
// NewNamed returns a new named type for the given type name, underlying type, and associated methods.
@ -122,7 +125,7 @@ func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named {
if _, ok := underlying.(*Named); ok {
panic("underlying type must not be *Named")
}
return (*Checker)(nil).newNamed(obj, nil, underlying, newMethodList(methods))
return (*Checker)(nil).newNamed(obj, nil, underlying, methods)
}
// resolve resolves the type parameters, methods, and underlying type of n.
@ -156,8 +159,12 @@ func (n *Named) resolve(ctxt *Context) *Named {
n.tparams = n.orig.tparams
n.underlying = underlying
n.fromRHS = n.orig.fromRHS // for cycle detection
n.methods = newLazyMethodList(n.orig.methods.Len())
if len(n.orig.methods) == 0 {
n.setState(complete)
} else {
n.setState(resolved)
}
return n
}
@ -170,17 +177,18 @@ func (n *Named) resolve(ctxt *Context) *Named {
// also make the API more future-proof towards further extensions.
if n.loader != nil {
assert(n.underlying == nil)
assert(n.TypeArgs().Len() == 0) // instances are created by instantiation, in which case n.loader is nil
tparams, underlying, methods := n.loader(n)
n.tparams = bindTParams(tparams)
n.underlying = underlying
n.fromRHS = underlying // for cycle detection
n.methods = newMethodList(methods)
n.methods = methods
n.loader = nil
}
n.setState(resolved)
n.setState(complete)
return n
}
@ -196,7 +204,7 @@ func (n *Named) setState(state namedState) {
}
// newNamed is like NewNamed but with a *Checker receiver and additional orig argument.
func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, methods *methodList) *Named {
func (check *Checker) newNamed(obj *TypeName, orig *Named, underlying Type, methods []*Func) *Named {
typ := &Named{check: check, obj: obj, orig: orig, fromRHS: underlying, underlying: underlying, methods: methods}
if typ.orig == nil {
typ.orig = typ
@ -264,14 +272,38 @@ func (t *Named) TypeArgs() *TypeList { return t.targs }
// For an ordinary or instantiated type t, the receiver base type of these
// methods will be the named type t. For an uninstantiated generic type t, each
// method receiver will be instantiated with its receiver type parameters.
func (t *Named) NumMethods() int { return t.resolve(nil).methods.Len() }
func (t *Named) NumMethods() int { return len(t.orig.resolve(nil).methods) }
// Method returns the i'th method of named type t for 0 <= i < t.NumMethods().
func (t *Named) Method(i int) *Func {
t.resolve(nil)
return t.methods.At(i, func() *Func {
return t.expandMethod(i)
})
if t.state() >= complete {
return t.methods[i]
}
assert(t.TypeArgs().Len() > 0) // only instances should have incomplete methods
t.mu.Lock()
defer t.mu.Unlock()
if len(t.methods) != len(t.orig.methods) {
assert(len(t.methods) == 0)
t.methods = make([]*Func, len(t.orig.methods))
}
if t.methods[i] == nil {
t.methods[i] = t.expandMethod(i)
t.expandedMethods++
// Check if we've created all methods at this point. If we have, mark the
// type as fully expanded.
if t.expandedMethods == len(t.orig.methods) {
t.setState(complete)
}
}
return t.methods[i]
}
// expandMethod substitutes type arguments in the i'th method for an
@ -353,10 +385,9 @@ func (t *Named) SetUnderlying(underlying Type) {
func (t *Named) AddMethod(m *Func) {
assert(t.targs.Len() == 0)
t.resolve(nil)
if t.methods == nil {
t.methods = newMethodList(nil)
if i, _ := lookupMethod(t.methods, m.pkg, m.name, false); i < 0 {
t.methods = append(t.methods, m)
}
t.methods.Add(m)
}
func (t *Named) Underlying() Type { return t.resolve(nil).underlying }
@ -464,7 +495,7 @@ func (n *Named) lookupMethod(pkg *Package, name string, foldCase bool) (int, *Fu
// If n is an instance, we may not have yet instantiated all of its methods.
// Look up the method index in orig, and only instantiate method at the
// matching index (if any).
i, _ := n.orig.methods.Lookup(pkg, name, foldCase)
i, _ := lookupMethod(n.orig.methods, pkg, name, foldCase)
if i < 0 {
return -1, nil
}

2
src/go/types/sizeof_test.go
View File

@ -30,7 +30,7 @@ func TestSizeof(t *testing.T) {
{Interface{}, 40, 80},
{Map{}, 16, 32},
{Chan{}, 12, 24},
{Named{}, 56, 104},
{Named{}, 68, 128},
{TypeParam{}, 28, 48},
{term{}, 12, 24},