internal/abi: move direct/indirect flag from Kind to TFlag

This info makes more sense in the flags instead of as a high
bit of the kind. This makes kind access simpler because we now
don't need to mask anything.

Cleaned up most direct field accesses to use methods instead.
(reflect making new types is the only remaining direct accessor.)

IfaceIndir -> !IsDirectIface everywhere.

gocore has been updated to handle the new location. So has delve.
TODO: any other tools need updating?

Change-Id: I123f97a4d4bdd0bff1641ee7e276d1cc0bd7e8eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/681936
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: David Chase <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: randall77

src/cmd/compile/internal/reflectdata/reflect.go

@@ -491,6 +491,9 @@ func dcommontype(c rttype.Cursor, t *types.Type) {
 			exported = types.IsExported(t.Elem().Sym().Name)
 		}
 	}
+	if types.IsDirectIface(t) {
+		tflag |= abi.TFlagDirectIface
+	}
 
 	if tflag != abi.TFlag(uint8(tflag)) {
 		// this should optimize away completely
@@ -511,9 +514,6 @@ func dcommontype(c rttype.Cursor, t *types.Type) {
 	c.Field("FieldAlign_").WriteUint8(uint8(t.Alignment()))
 
 	kind := kinds[t.Kind()]
-	if types.IsDirectIface(t) {
-		kind |= abi.KindDirectIface
-	}
 	c.Field("Kind_").WriteUint8(uint8(kind))
 
 	c.Field("Equal").WritePtr(eqfunc)

src/cmd/compile/internal/test/inl_test.go

@@ -47,7 +47,6 @@ func TestIntendedInlining(t *testing.T) {
 			"getMCache",
 			"heapSetTypeNoHeader",
 			"heapSetTypeSmallHeader",
-			"isDirectIface",
 			"itabHashFunc",
 			"nextslicecap",
 			"noescape",
@@ -109,6 +108,7 @@ func TestIntendedInlining(t *testing.T) {
 			"(*Buffer).tryGrowByReslice",
 		},
 		"internal/abi": {
+			"(*Type).IsDirectIface",
 			"UseInterfaceSwitchCache",
 		},
 		"internal/runtime/math": {

src/cmd/link/internal/ld/decodesym.go

@@ -38,7 +38,7 @@ func uncommonSize(arch *sys.Arch) int    { return int(abi.UncommonSize()) }
 
 // Type.commonType.kind
 func decodetypeKind(arch *sys.Arch, p []byte) abi.Kind {
-	return abi.Kind(p[2*arch.PtrSize+7]) & abi.KindMask //  0x13 / 0x1f
+	return abi.Kind(p[2*arch.PtrSize+7]) //  0x13
 }
 
 // Type.commonType.size

src/internal/abi/type.go

@@ -24,7 +24,7 @@ type Type struct {
 	TFlag       TFlag   // extra type information flags
 	Align_      uint8   // alignment of variable with this type
 	FieldAlign_ uint8   // alignment of struct field with this type
-	Kind_       Kind    // enumeration for C
+	Kind_       Kind    // what kind of type this is (string, int, ...)
 	// function for comparing objects of this type
 	// (ptr to object A, ptr to object B) -> ==?
 	Equal func(unsafe.Pointer, unsafe.Pointer) bool
@@ -78,12 +78,6 @@ const (
 	UnsafePointer
 )
 
-const (
-	// TODO (khr, drchase) why aren't these in TFlag?  Investigate, fix if possible.
-	KindDirectIface Kind = 1 << 5
-	KindMask        Kind = (1 << 5) - 1
-)
-
 // TFlag is used by a Type to signal what extra type information is
 // available in the memory directly following the Type value.
 type TFlag uint8
@@ -125,6 +119,15 @@ const (
 	// has type **byte instead of *byte. The runtime will store a
 	// pointer to the GC pointer bitmask in *GCData.
 	TFlagGCMaskOnDemand TFlag = 1 << 4
+
+	// TFlagDirectIface means that a value of this type is stored directly
+	// in the data field of an interface, instead of indirectly. Normally
+	// this means the type is pointer-ish.
+	TFlagDirectIface TFlag = 1 << 5
+
+	// Leaving this breadcrumb behind for dlv. It should not be used, and no
+	// Kind should be big enough to set this bit.
+	KindDirectIface Kind = 1 << 5
 )
 
 // NameOff is the offset to a name from moduledata.types.  See resolveNameOff in runtime.
@@ -190,7 +193,7 @@ func TypeFor[T any]() *Type {
 	return (*PtrType)(unsafe.Pointer(TypeOf((*T)(nil)))).Elem
 }
 
-func (t *Type) Kind() Kind { return t.Kind_ & KindMask }
+func (t *Type) Kind() Kind { return t.Kind_ }
 
 func (t *Type) HasName() bool {
 	return t.TFlag&TFlagNamed != 0
@@ -199,14 +202,9 @@ func (t *Type) HasName() bool {
 // Pointers reports whether t contains pointers.
 func (t *Type) Pointers() bool { return t.PtrBytes != 0 }
 
-// IfaceIndir reports whether t is stored indirectly in an interface value.
-func (t *Type) IfaceIndir() bool {
-	return t.Kind_&KindDirectIface == 0
-}
-
-// isDirectIface reports whether t is stored directly in an interface value.
+// IsDirectIface reports whether t is stored directly in an interface value.
 func (t *Type) IsDirectIface() bool {
-	return t.Kind_&KindDirectIface != 0
+	return t.TFlag&TFlagDirectIface != 0
 }
 
 func (t *Type) GcSlice(begin, end uintptr) []byte {

src/internal/reflectlite/export_test.go

@@ -70,7 +70,7 @@ func Zero(typ Type) Value {
 	}
 	t := typ.common()
 	fl := flag(t.Kind())
-	if t.IfaceIndir() {
+	if !t.IsDirectIface() {
 		return Value{t, unsafe_New(t), fl | flagIndir}
 	}
 	return Value{t, nil, fl}

src/internal/reflectlite/value.go

@@ -52,7 +52,7 @@ type Value struct {
 	//	- flagIndir: val holds a pointer to the data
 	//	- flagAddr: v.CanAddr is true (implies flagIndir and ptr is non-nil)
 	//	- flagMethod: v is a method value.
-	// If ifaceIndir(typ), code can assume that flagIndir is set.
+	// If !typ.IsDirectIface(), code can assume that flagIndir is set.
 	//
 	// The remaining 22+ bits give a method number for method values.
 	// If flag.kind() != Func, code can assume that flagMethod is unset.
@@ -118,7 +118,7 @@ func packEface(v Value) any {
 	e := (*abi.EmptyInterface)(unsafe.Pointer(&i))
 	// First, fill in the data portion of the interface.
 	switch {
-	case t.IfaceIndir():
+	case !t.IsDirectIface():
 		if v.flag&flagIndir == 0 {
 			panic("bad indir")
 		}
@@ -155,7 +155,7 @@ func unpackEface(i any) Value {
 		return Value{}
 	}
 	f := flag(t.Kind())
-	if t.IfaceIndir() {
+	if !t.IsDirectIface() {
 		f |= flagIndir
 	}
 	return Value{t, e.Data, f}

src/internal/runtime/maps/map.go

@@ -859,7 +859,7 @@ func mapKeyError2(t *abi.Type, p unsafe.Pointer) error {
 			return unhashableTypeError{t}
 		}
 
-		if t.Kind_&abi.KindDirectIface != 0 {
+		if t.IsDirectIface() {
 			return mapKeyError2(t, unsafe.Pointer(pdata))
 		} else {
 			return mapKeyError2(t, *pdata)

src/reflect/abi.go

@@ -166,7 +166,7 @@ func (a *abiSeq) addRcvr(rcvr *abi.Type) (*abiStep, bool) {
 	// The receiver is always one word.
 	a.valueStart = append(a.valueStart, len(a.steps))
 	var ok, ptr bool
-	if rcvr.IfaceIndir() || rcvr.Pointers() {
+	if !rcvr.IsDirectIface() || rcvr.Pointers() {
 		ok = a.assignIntN(0, goarch.PtrSize, 1, 0b1)
 		ptr = true
 	} else {

src/reflect/badlinkname.go

@@ -27,7 +27,7 @@ import (
 //
 //go:linkname unusedIfaceIndir reflect.ifaceIndir
 func unusedIfaceIndir(t *abi.Type) bool {
-	return t.Kind_&abi.KindDirectIface == 0
+	return !t.IsDirectIface()
 }
 
 //go:linkname valueInterface

src/reflect/export_noswiss_test.go

@@ -7,7 +7,6 @@
 package reflect
 
 import (
-	"internal/abi"
 	"unsafe"
 )
 
@@ -17,7 +16,7 @@ func MapBucketOf(x, y Type) Type {
 
 func CachedBucketOf(m Type) Type {
 	t := m.(*rtype)
-	if Kind(t.t.Kind_&abi.KindMask) != Map {
+	if Kind(t.t.Kind()) != Map {
 		panic("not map")
 	}
 	tt := (*mapType)(unsafe.Pointer(t))