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cmd/compile: don't allow go:notinheap on the heap or stack

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Right now we just prevent such types from being on the heap. This CL
makes it so they cannot appear on the stack either. The distinction
between heap and stack is pretty vague at the language level (e.g. it
is affected by -N), and we don't need the flexibility anyway.

Once go:notinheap types cannot be in either place, we don't need to
consider pointers to such types to be pointers, at least according to
the garbage collector and stack copying. (This is the big win of this
CL, in my opinion.)

The distinction between HasPointers and HasHeapPointer no longer
exists. There is only HasPointers.

This CL is cleanup before possible use of go:notinheap to fix #40954.

Update #13386

Change-Id: Ibd895aadf001c0385078a6d4809c3f374991231a
Reviewed-on: https://go-review.googlesource.com/c/go/+/249917
Run-TryBot: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
This commit is contained in:
Keith Randall 2020-08-21 20:20:12 -07:00
parent 95df156e6a
commit d9a6bdf7ef
16 changed files with 54 additions and 68 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
src/cmd/compile/internal/gc/escape.go
View File

@ -1029,6 +1029,9 @@ func (e *Escape) newLoc(n *Node, transient bool) *EscLocation {
if e.curfn == nil {
Fatalf("e.curfn isn't set")
}
if n != nil && n.Type != nil && n.Type.NotInHeap() {
yyerrorl(n.Pos, "%v is go:notinheap; stack allocation disallowed", n.Type)
}
n = canonicalNode(n)
loc := &EscLocation{

10
src/cmd/compile/internal/gc/pgen_test.go
View File

@ -20,7 +20,7 @@ func typeWithoutPointers() *types.Type {
func typeWithPointers() *types.Type {
t := types.New(TSTRUCT)
f := &types.Field{Type: types.New(TPTR)}
f := &types.Field{Type: types.NewPtr(types.New(TINT))}
t.SetFields([]*types.Field{f})
return t
}
@ -181,14 +181,6 @@ func TestStackvarSort(t *testing.T) {
nodeWithClass(Node{Type: &types.Type{}, Sym: &types.Sym{Name: "xyz"}}, PAUTO),
nodeWithClass(Node{Type: typeWithoutPointers(), Sym: &types.Sym{}}, PAUTO),
}
// haspointers updates Type.Haspointers as a side effect, so
// exercise this function on all inputs so that reflect.DeepEqual
// doesn't produce false positives.
for i := range want {
want[i].Type.HasPointers()
inp[i].Type.HasPointers()
}
sort.Sort(byStackVar(inp))
if !reflect.DeepEqual(want, inp) {
t.Error("sort failed")

14
src/cmd/compile/internal/gc/plive.go
View File

@ -436,7 +436,7 @@ func (lv *Liveness) regEffects(v *ssa.Value) (uevar, kill liveRegMask) {
case ssa.LocalSlot:
return mask
case *ssa.Register:
if ptrOnly && !v.Type.HasHeapPointer() {
if ptrOnly && !v.Type.HasPointers() {
return mask
}
regs[0] = loc
@ -451,7 +451,7 @@ func (lv *Liveness) regEffects(v *ssa.Value) (uevar, kill liveRegMask) {
if loc1 == nil {
continue
}
if ptrOnly && !v.Type.FieldType(i).HasHeapPointer() {
if ptrOnly && !v.Type.FieldType(i).HasPointers() {
continue
}
regs[nreg] = loc1.(*ssa.Register)
@ -568,13 +568,13 @@ func onebitwalktype1(t *types.Type, off int64, bv bvec) {
if t.Align > 0 && off&int64(t.Align-1) != 0 {
Fatalf("onebitwalktype1: invalid initial alignment: type %v has alignment %d, but offset is %v", t, t.Align, off)
}
if !t.HasPointers() {
// Note: this case ensures that pointers to go:notinheap types
// are not considered pointers by garbage collection and stack copying.
return
}
switch t.Etype {
case TINT8, TUINT8, TINT16, TUINT16,
TINT32, TUINT32, TINT64, TUINT64,
TINT, TUINT, TUINTPTR, TBOOL,
TFLOAT32, TFLOAT64, TCOMPLEX64, TCOMPLEX128:
case TPTR, TUNSAFEPTR, TFUNC, TCHAN, TMAP:
if off&int64(Widthptr-1) != 0 {
Fatalf("onebitwalktype1: invalid alignment, %v", t)

2
src/cmd/compile/internal/gc/range.go
View File

@ -586,7 +586,7 @@ func arrayClear(n, v1, v2, a *Node) bool {
n.Nbody.Append(nod(OAS, hn, tmp))
var fn *Node
if a.Type.Elem().HasHeapPointer() {
if a.Type.Elem().HasPointers() {
// memclrHasPointers(hp, hn)
Curfn.Func.setWBPos(stmt.Pos)
fn = mkcall("memclrHasPointers", nil, nil, hp, hn)

23
src/cmd/compile/internal/gc/walk.go
View File

@ -1156,6 +1156,9 @@ opswitch:
}
case ONEW:
if n.Type.Elem().NotInHeap() {
yyerror("%v is go:notinheap; heap allocation disallowed", n.Type.Elem())
}
if n.Esc == EscNone {
if n.Type.Elem().Width >= maxImplicitStackVarSize {
Fatalf("large ONEW with EscNone: %v", n)
@ -1324,6 +1327,9 @@ opswitch:
l = r
}
t := n.Type
if t.Elem().NotInHeap() {
yyerror("%v is go:notinheap; heap allocation disallowed", t.Elem())
}
if n.Esc == EscNone {
if !isSmallMakeSlice(n) {
Fatalf("non-small OMAKESLICE with EscNone: %v", n)
@ -1365,10 +1371,6 @@ opswitch:
// When len and cap can fit into int, use makeslice instead of
// makeslice64, which is faster and shorter on 32 bit platforms.
if t.Elem().NotInHeap() {
yyerror("%v is go:notinheap; heap allocation disallowed", t.Elem())
}
len, cap := l, r
fnname := "makeslice64"
@ -1403,7 +1405,7 @@ opswitch:
t := n.Type
if t.Elem().NotInHeap() {
Fatalf("%v is go:notinheap; heap allocation disallowed", t.Elem())
yyerror("%v is go:notinheap; heap allocation disallowed", t.Elem())
}
length := conv(n.Left, types.Types[TINT])
@ -2012,9 +2014,6 @@ func walkprint(nn *Node, init *Nodes) *Node {
}
func callnew(t *types.Type) *Node {
if t.NotInHeap() {
yyerror("%v is go:notinheap; heap allocation disallowed", t)
}
dowidth(t)
n := nod(ONEWOBJ, typename(t), nil)
n.Type = types.NewPtr(t)
@ -2589,7 +2588,7 @@ func mapfast(t *types.Type) int {
}
switch algtype(t.Key()) {
case AMEM32:
if !t.Key().HasHeapPointer() {
if !t.Key().HasPointers() {
return mapfast32
}
if Widthptr == 4 {
@ -2597,7 +2596,7 @@ func mapfast(t *types.Type) int {
}
Fatalf("small pointer %v", t.Key())
case AMEM64:
if !t.Key().HasHeapPointer() {
if !t.Key().HasPointers() {
return mapfast64
}
if Widthptr == 8 {
@ -2744,7 +2743,7 @@ func appendslice(n *Node, init *Nodes) *Node {
nodes.Append(nod(OAS, s, nt))
var ncopy *Node
if elemtype.HasHeapPointer() {
if elemtype.HasPointers() {
// copy(s[len(l1):], l2)
nptr1 := nod(OSLICE, s, nil)
nptr1.Type = s.Type
@ -3082,7 +3081,7 @@ func walkappend(n *Node, init *Nodes, dst *Node) *Node {
// Also works if b is a string.
//
func copyany(n *Node, init *Nodes, runtimecall bool) *Node {
if n.Left.Type.Elem().HasHeapPointer() {
if n.Left.Type.Elem().HasPointers() {
Curfn.Func.setWBPos(n.Pos)
fn := writebarrierfn("typedslicecopy", n.Left.Type.Elem(), n.Right.Type.Elem())
n.Left = cheapexpr(n.Left, init)

2
src/cmd/compile/internal/ssa/decompose.go
View File

@ -139,7 +139,7 @@ func decomposeStringPhi(v *Value) {
func decomposeSlicePhi(v *Value) {
types := &v.Block.Func.Config.Types
ptrType := types.BytePtr
ptrType := v.Type.Elem().PtrTo()
lenType := types.Int
ptr := v.Block.NewValue0(v.Pos, OpPhi, ptrType)

4
src/cmd/compile/internal/ssa/gen/dec.rules
View File

@ -66,14 +66,14 @@
(Load <typ.Int>
(OffPtr <typ.IntPtr> [2*config.PtrSize] ptr)
mem))
(Store dst (SliceMake ptr len cap) mem) =>
(Store {t} dst (SliceMake ptr len cap) mem) =>
(Store {typ.Int}
(OffPtr <typ.IntPtr> [2*config.PtrSize] dst)
cap
(Store {typ.Int}
(OffPtr <typ.IntPtr> [config.PtrSize] dst)
len
(Store {typ.BytePtr} dst ptr mem)))
(Store {t.Elem().PtrTo()} dst ptr mem)))
// interface ops
(ITab (IMake itab _)) => itab

2
src/cmd/compile/internal/ssa/nilcheck.go
View File

@ -235,7 +235,7 @@ func nilcheckelim2(f *Func) {
continue
}
if v.Type.IsMemory() || v.Type.IsTuple() && v.Type.FieldType(1).IsMemory() {
if v.Op == OpVarKill || v.Op == OpVarLive || (v.Op == OpVarDef && !v.Aux.(GCNode).Typ().HasHeapPointer()) {
if v.Op == OpVarKill || v.Op == OpVarLive || (v.Op == OpVarDef && !v.Aux.(GCNode).Typ().HasPointers()) {
// These ops don't really change memory.
continue
// Note: OpVarDef requires that the defined variable not have pointers.

7
src/cmd/compile/internal/ssa/rewritedec.go
View File

@ -328,9 +328,10 @@ func rewriteValuedec_OpStore(v *Value) bool {
v.AddArg3(v0, len, v1)
return true
}
// match: (Store dst (SliceMake ptr len cap) mem)
// result: (Store {typ.Int} (OffPtr <typ.IntPtr> [2*config.PtrSize] dst) cap (Store {typ.Int} (OffPtr <typ.IntPtr> [config.PtrSize] dst) len (Store {typ.BytePtr} dst ptr mem)))
// match: (Store {t} dst (SliceMake ptr len cap) mem)
// result: (Store {typ.Int} (OffPtr <typ.IntPtr> [2*config.PtrSize] dst) cap (Store {typ.Int} (OffPtr <typ.IntPtr> [config.PtrSize] dst) len (Store {t.Elem().PtrTo()} dst ptr mem)))
for {
t := auxToType(v.Aux)
dst := v_0
if v_1.Op != OpSliceMake {
break
@ -350,7 +351,7 @@ func rewriteValuedec_OpStore(v *Value) bool {
v2.AuxInt = int64ToAuxInt(config.PtrSize)
v2.AddArg(dst)
v3 := b.NewValue0(v.Pos, OpStore, types.TypeMem)
v3.Aux = typeToAux(typ.BytePtr)
v3.Aux = typeToAux(t.Elem().PtrTo())
v3.AddArg3(dst, ptr, mem)
v1.AddArg3(v2, len, v3)
v.AddArg3(v0, cap, v1)

2
src/cmd/compile/internal/ssa/writebarrier.go
View File

@ -31,7 +31,7 @@ func needwb(v *Value, zeroes map[ID]ZeroRegion) bool {
if !ok {
v.Fatalf("store aux is not a type: %s", v.LongString())
}
if !t.HasHeapPointer() {
if !t.HasPointers() {
return false
}
if IsStackAddr(v.Args[0]) {

24
src/cmd/compile/internal/types/type.go
View File

@ -1398,14 +1398,9 @@ func (t *Type) IsUntyped() bool {
return false
}
// TODO(austin): We probably only need HasHeapPointer. See
// golang.org/cl/73412 for discussion.
// HasPointers reports whether t contains a heap pointer.
// Note that this function ignores pointers to go:notinheap types.
func (t *Type) HasPointers() bool {
return t.hasPointers1(false)
}
func (t *Type) hasPointers1(ignoreNotInHeap bool) bool {
switch t.Etype {
case TINT, TUINT, TINT8, TUINT8, TINT16, TUINT16, TINT32, TUINT32, TINT64,
TUINT64, TUINTPTR, TFLOAT32, TFLOAT64, TCOMPLEX64, TCOMPLEX128, TBOOL, TSSA:
@ -1415,34 +1410,27 @@ func (t *Type) hasPointers1(ignoreNotInHeap bool) bool {
if t.NumElem() == 0 { // empty array has no pointers
return false
}
return t.Elem().hasPointers1(ignoreNotInHeap)
return t.Elem().HasPointers()
case TSTRUCT:
for _, t1 := range t.Fields().Slice() {
if t1.Type.hasPointers1(ignoreNotInHeap) {
if t1.Type.HasPointers() {
return true
}
}
return false
case TPTR, TSLICE:
return !(ignoreNotInHeap && t.Elem().NotInHeap())
return !t.Elem().NotInHeap()
case TTUPLE:
ttup := t.Extra.(*Tuple)
return ttup.first.hasPointers1(ignoreNotInHeap) || ttup.second.hasPointers1(ignoreNotInHeap)
return ttup.first.HasPointers() || ttup.second.HasPointers()
}
return true
}
// HasHeapPointer reports whether t contains a heap pointer.
// This is used for write barrier insertion, so it ignores
// pointers to go:notinheap types.
func (t *Type) HasHeapPointer() bool {
return t.hasPointers1(true)
}
func (t *Type) Symbol() *obj.LSym {
return TypeLinkSym(t)
}

7
src/runtime/export_test.go
View File

@ -981,9 +981,8 @@ func MapHashCheck(m interface{}, k interface{}) (uintptr, uintptr) {
}
func MSpanCountAlloc(bits []byte) int {
s := mspan{
nelems: uintptr(len(bits) * 8),
gcmarkBits: (*gcBits)(unsafe.Pointer(&bits[0])),
}
s := (*mspan)(mheap_.spanalloc.alloc())
s.nelems = uintptr(len(bits) * 8)
s.gcmarkBits = (*gcBits)(unsafe.Pointer(&bits[0]))
return s.countAlloc()
}

3
src/runtime/mgcmark.go
View File

@ -837,7 +837,8 @@ func scanstack(gp *g, gcw *gcWork) {
x := state.head
state.head = x.next
if stackTraceDebug {
for _, obj := range x.obj[:x.nobj] {
for i := 0; i < x.nobj; i++ {
obj := &x.obj[i]
if obj.typ == nil { // reachable
continue
}

2
src/runtime/mgcstack.go
View File

@ -167,8 +167,6 @@ func (obj *stackObject) setType(typ *_type) {
// A stackScanState keeps track of the state used during the GC walk
// of a goroutine.
//
//go:notinheap
type stackScanState struct {
cache pcvalueCache

5
src/runtime/runtime2.go
View File

@ -909,15 +909,12 @@ type _defer struct {
// A _panic holds information about an active panic.
//
// This is marked go:notinheap because _panic values must only ever
// live on the stack.
// A _panic value must only ever live on the stack.
//
// The argp and link fields are stack pointers, but don't need special
// handling during stack growth: because they are pointer-typed and
// _panic values only live on the stack, regular stack pointer
// adjustment takes care of them.
//
//go:notinheap
type _panic struct {
argp unsafe.Pointer // pointer to arguments of deferred call run during panic; cannot move - known to liblink
arg interface{} // argument to panic

12
test/notinheap2.go
View File

@ -13,12 +13,14 @@ type nih struct {
next *nih
}
// Globals and stack variables are okay.
// Global variables are okay.
var x nih
// Stack variables are not okay.
func f() {
var y nih
var y nih // ERROR "nih is go:notinheap; stack allocation disallowed"
x = y
}
@ -26,11 +28,17 @@ func f() {
var y *nih
var z []nih
var w []nih
var n int
func g() {
y = new(nih) // ERROR "heap allocation disallowed"
z = make([]nih, 1) // ERROR "heap allocation disallowed"
z = append(z, x) // ERROR "heap allocation disallowed"
// Test for special case of OMAKESLICECOPY
x := make([]nih, n) // ERROR "heap allocation disallowed"
copy(x, z)
z = x
}
// Writes don't produce write barriers.