internal/runtime: type hash

internal/runtime/z_face.go

@@ -116,6 +116,7 @@ func NewNamed(pkgPath string, name string, kind abi.Kind, size uintptr, methods,
 	}
 	ret := allocUncommonType(kind, size, methods, abi.TFlagUninited|abi.TFlagNamed|abi.TFlagUncommon, pkgPath)
 	ret.Str_ = name
+	ret.Hash = 9157 + hashString(pkgPath) + hashString(name)
 	if ptrMethods == 0 {
 		ret.PtrToThis_ = newPointer(ret)
 	} else {
@@ -210,7 +211,6 @@ func Func(in, out []*Type, variadic bool) *FuncType {
 		Type: Type{
 			Size_:       2 * unsafe.Sizeof(uintptr(0)),
 			PtrBytes:    2 * pointerSize,
-			Hash:        uint32(abi.Func), // TODO(xsw): hash
 			Align_:      uint8(pointerAlign),
 			FieldAlign_: uint8(pointerAlign),
 			Kind_:       uint8(abi.Func),
@@ -218,9 +218,13 @@ func Func(in, out []*Type, variadic bool) *FuncType {
 		In:  in,
 		Out: out,
 	}
+	var hash uint32 = 9091
 	if variadic {
+		hash *= 8863
 		ret.TFlag |= abi.TFlagVariadic
 	}
+	hash += 3*hashTuple(in) + 5*hashTuple(out)
+	ret.Hash = hash
 	ret.Str_ = funcStr(ret)
 	rtypeList.addType(&ret.Type)
 	return ret
@@ -243,7 +247,7 @@ func NewNamedInterface(pkgPath, name string) *InterfaceType {
 			Type: Type{
 				Size_:       unsafe.Sizeof(eface{}),
 				PtrBytes:    2 * pointerSize,
-				Hash:        uint32(abi.Interface), // TODO(xsw): hash
+				Hash:        9157 + hashString(pkgPath) + hashString(name),
 				Align_:      uint8(pointerAlign),
 				FieldAlign_: uint8(pointerAlign),
 				Kind_:       uint8(abi.Interface),
@@ -277,7 +281,6 @@ func Interface(pkgPath string, methods []Imethod) *InterfaceType {
 		Type: Type{
 			Size_:       unsafe.Sizeof(eface{}),
 			PtrBytes:    2 * pointerSize,
-			Hash:        uint32(abi.Interface), // TODO(xsw): hash
 			Align_:      uint8(pointerAlign),
 			FieldAlign_: uint8(pointerAlign),
 			Kind_:       uint8(abi.Interface),
@@ -291,6 +294,14 @@ func Interface(pkgPath string, methods []Imethod) *InterfaceType {
 		ret.Equal = interequal
 	}
 	ret.Str_ = interfaceStr(ret)
+	var hash uint32 = 9103
+	// Hash methods.
+	for _, m := range methods {
+		// Use shallow hash on method signature to
+		// avoid anonymous interface cycles.
+		hash += 3*hashString(m.Name()) + 5*shallowHash(&m.Typ_.Type)
+	}
+	ret.Hash = hash
 	rtypeList.addType(&ret.Type)
 	return ret
 }
@@ -541,4 +552,88 @@ func funcStr(ft *abi.FuncType) string {
 	return string(repr)
 }
 
+func hashTuple(tuple []*Type) uint32 {
+	// See go/types.identicalTypes for rationale.
+	n := len(tuple)
+	hash := 9137 + 2*uint32(n)
+	for i := 0; i < n; i++ {
+		hash += 3 * tuple[i].Hash
+	}
+	return hash
+}
+
+// shallowHash computes a hash of t without looking at any of its
+// element Types, to avoid potential anonymous cycles in the types of
+// interface methods.
+//
+// When an unnamed non-empty interface type appears anywhere among the
+// arguments or results of an interface method, there is a potential
+// for endless recursion. Consider:
+//
+//	type X interface { m() []*interface { X } }
+//
+// The problem is that the Methods of the interface in m's result type
+// include m itself; there is no mention of the named type X that
+// might help us break the cycle.
+// (See comment in go/types.identical, case *Interface, for more.)
+func shallowHash(t *abi.Type) uint32 {
+	// t is the type of an interface method (Signature),
+	// its params or results (Tuples), or their immediate
+	// elements (mostly Slice, Pointer, Basic, Named),
+	// so there's no need to optimize anything else.
+
+	if t.HasName() {
+		return 9157 + hashString(t.Uncommon().PkgPath_) + hashString(t.Str_)
+	}
+
+	switch t.Kind() {
+	case abi.Bool, abi.Int, abi.Int8, abi.Int16, abi.Int32, abi.Int64,
+		abi.Uint, abi.Uint8, abi.Uint16, abi.Uint32, abi.Uint64, abi.Uintptr,
+		abi.Float32, abi.Float64, abi.Complex64, abi.Complex128, abi.String, abi.UnsafePointer:
+		return 45212177 * uint32(t.Kind())
+
+	case abi.Func:
+		t := t.FuncType()
+		var hash uint32 = 604171
+		if t.Variadic() {
+			hash *= 971767
+		}
+		// The Signature/Tuple recursion is always finite
+		// and invariably shallow.
+		return hash + 1062599*shallowHashTuple(t.In) + 1282529*shallowHashTuple(t.Out)
+
+	case abi.Array:
+		return 1524181 + 2*uint32(t.ArrayType().Len)
+
+	case abi.Slice:
+		return 2690201
+
+	case abi.Struct:
+		return 3326489
+
+	case abi.Pointer:
+		return 4393139
+
+	case abi.Interface:
+		return 2124679 // no recursion here
+
+	case abi.Map:
+		return 9109
+
+	case abi.Chan:
+		return 9127
+	}
+
+	panic("shallowHash:" + t.String())
+}
+
+func shallowHashTuple(tuple []*Type) uint32 {
+	n := len(tuple)
+	hash := 9137 + 2*uint32(n)
+	for i := 0; i < n; i++ {
+		hash += 53471161 * shallowHash(tuple[i])
+	}
+	return hash
+}
+
 // -----------------------------------------------------------------------------

internal/runtime/z_type.go

@@ -79,7 +79,7 @@ func Basic(_kind Kind) *Type {
 		tyBasic[kind] = &Type{
 			Size_:       size,
 			PtrBytes:    bytes,
-			Hash:        uint32(kind), // TODO(xsw): hash
+			Hash:        uint32(kind),
 			Align_:      uint8(align),
 			FieldAlign_: uint8(align),
 			Kind_:       uint8(_kind),
@@ -154,13 +154,13 @@ func Struct(pkgPath string, size uintptr, fields ...abi.StructField) *Type {
 	ret := &abi.StructType{
 		Type: Type{
 			Size_: size,
-			Hash:  uint32(abi.Struct), // TODO(xsw): hash
 			Kind_: uint8(abi.Struct),
 			Str_:  structStr(fields),
 		},
 		PkgPath_: pkgPath,
 		Fields:   fields,
 	}
+	var hash uint32 = 9059
 	var comparable bool = true
 	var typalign uint8
 	for _, f := range fields {
@@ -172,7 +172,14 @@ func Struct(pkgPath string, size uintptr, fields ...abi.StructField) *Type {
 			ret.PtrBytes = f.Offset + f.Typ.PtrBytes
 		}
 		comparable = comparable && (ft.Equal != nil)
+		if f.Embedded_ {
+			hash += 8861
 		}
+		hash += hashString(f.Tag_)
+		hash += hashString(f.Name_)
+		hash += f.Typ.Hash
+	}
+	ret.Hash = hash
 	ret.Align_ = typalign
 	ret.FieldAlign_ = typalign
 	if comparable {
@@ -220,7 +227,7 @@ func newPointer(elem *Type) *Type {
 		Type: Type{
 			Size_:       unsafe.Sizeof(uintptr(0)),
 			PtrBytes:    pointerSize,
-			Hash:        uint32(abi.Pointer), // TODO(xsw): hash
+			Hash:        9067 + 2*elem.Hash,
 			Align_:      pointerAlign,
 			FieldAlign_: pointerAlign,
 			Kind_:       uint8(abi.Pointer),
@@ -259,7 +266,7 @@ func SliceOf(elem *Type) *Type {
 		Type: Type{
 			Size_:       unsafe.Sizeof([]int{}),
 			PtrBytes:    pointerSize,
-			Hash:        uint32(abi.Slice),
+			Hash:        9049 + 2*elem.Hash,
 			Align_:      pointerAlign,
 			FieldAlign_: pointerAlign,
 			Kind_:       uint8(abi.Slice),
@@ -279,7 +286,7 @@ func ArrayOf(length uintptr, elem *Type) *Type {
 	ret := &abi.ArrayType{
 		Type: Type{
 			Size_:       length * elem.Size_,
-			Hash:        uint32(abi.Array),
+			Hash:        9043 + 2*uint32(length) + 3*elem.Hash,
 			Align_:      elem.Align_,
 			FieldAlign_: elem.FieldAlign_,
 			Kind_:       uint8(abi.Array),
@@ -326,7 +333,7 @@ func ChanOf(dir int, strChan string, elem *Type) *Type {
 		Type: Type{
 			Size_:       pointerSize,
 			PtrBytes:    pointerSize,
-			Hash:        uint32(abi.Chan),
+			Hash:        9127 + 2*uint32(dir) + 3*elem.Hash,
 			Align_:      pointerAlign,
 			TFlag:       abi.TFlagRegularMemory,
 			FieldAlign_: pointerAlign,
@@ -349,7 +356,7 @@ func MapOf(key, elem *Type, bucket *Type, flags int) *Type {
 		Type: Type{
 			Size_:       unsafe.Sizeof(uintptr(0)),
 			PtrBytes:    pointerSize,
-			Hash:        uint32(abi.Map),
+			Hash:        9109 + 2*key.Hash + 3*elem.Hash,
 			Align_:      pointerAlign,
 			FieldAlign_: pointerAlign,
 			Kind_:       uint8(abi.Map),
@@ -567,4 +574,14 @@ func (r *rtypes) addType(typ *Type) {
 
 var rtypeList rtypes
 
+// hashString computes the Fowler–Noll–Vo hash of s.
+func hashString(s string) uint32 {
+	var h uint32
+	for i := 0; i < len(s); i++ {
+		h ^= uint32(s[i])
+		h *= 16777619
+	}
+	return h
+}
+
 // -----------------------------------------------------------------------------