[dev.regabi] cmd/compile: remove gc ↔ ssa cycle hacks

The cycle hacks existed because gc needed to import ssa
which need to know about gc.Node. But now that's ir.Node,
and there's no cycle anymore.

Don't know how much it matters but LocalSlot is now
one word shorter than before, because it holds a pointer
instead of an interface for the *Node. That won't last long.

Now that they're not necessary for interface satisfaction,
IsSynthetic and IsAutoTmp can move to top-level ir functions.

Change-Id: Ie511e93466cfa2b17d9a91afc4bd8d53fdb80453
Reviewed-on: https://go-review.googlesource.com/c/go/+/272931
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

16 files changed, 73 insertions, 126 deletions

diff --git a/src/cmd/compile/fmtmap_test.go b/src/cmd/compile/fmtmap_test.go
index 404e89d0f2..432d26a7b8 100644
--- a/src/cmd/compile/fmtmap_test.go
+++ b/src/cmd/compile/fmtmap_test.go
@@ -81,7 +81,6 @@ var knownFormats = map[string]string{
 	"cmd/compile/internal/gc.initKind %d":             "",
 	"cmd/compile/internal/gc.itag %v":                 "",
 	"cmd/compile/internal/ir.Class %d":                "",
-	"cmd/compile/internal/ir.Class %s":                "",
 	"cmd/compile/internal/ir.Class %v":                "",
 	"cmd/compile/internal/ir.FmtMode %d":              "",
 	"cmd/compile/internal/ir.Nodes %#v":               "",
@@ -92,7 +91,6 @@ var knownFormats = map[string]string{
 	"cmd/compile/internal/ir.Op %v":                   "",
 	"cmd/compile/internal/ssa.BranchPrediction %d":    "",
 	"cmd/compile/internal/ssa.Edge %v":                "",
-	"cmd/compile/internal/ssa.GCNode %v":              "",
 	"cmd/compile/internal/ssa.ID %d":                  "",
 	"cmd/compile/internal/ssa.ID %v":                  "",
 	"cmd/compile/internal/ssa.LocalSlot %s":           "",
diff --git a/src/cmd/compile/internal/gc/order.go b/src/cmd/compile/internal/gc/order.go
index 25bdbd5a41..3bd49e8094 100644
--- a/src/cmd/compile/internal/gc/order.go
+++ b/src/cmd/compile/internal/gc/order.go
@@ -195,7 +195,7 @@ func (o *Order) safeExpr(n *ir.Node) *ir.Node {
 // because we emit explicit VARKILL instructions marking the end of those
 // temporaries' lifetimes.
 func isaddrokay(n *ir.Node) bool {
-	return islvalue(n) && (n.Op != ir.ONAME || n.Class() == ir.PEXTERN || n.IsAutoTmp())
+	return islvalue(n) && (n.Op != ir.ONAME || n.Class() == ir.PEXTERN || ir.IsAutoTmp(n))
 }
 
 // addrTemp ensures that n is okay to pass by address to runtime routines.
@@ -550,10 +550,10 @@ func (o *Order) mapAssign(n *ir.Node) {
 		for i, m := range n.List.Slice() {
 			switch {
 			case m.Op == ir.OINDEXMAP:
-				if !m.Left.IsAutoTmp() {
+				if !ir.IsAutoTmp(m.Left) {
 					m.Left = o.copyExpr(m.Left, m.Left.Type, false)
 				}
-				if !m.Right.IsAutoTmp() {
+				if !ir.IsAutoTmp(m.Right) {
 					m.Right = o.copyExpr(m.Right, m.Right.Type, false)
 				}
 				fallthrough
@@ -952,11 +952,11 @@ func (o *Order) stmt(n *ir.Node) {
 				// r->left is c, r->right is x, both are always evaluated.
 				r.Left = o.expr(r.Left, nil)
 
-				if !r.Left.IsAutoTmp() {
+				if !ir.IsAutoTmp(r.Left) {
 					r.Left = o.copyExpr(r.Left, r.Left.Type, false)
 				}
 				r.Right = o.expr(r.Right, nil)
-				if !r.Right.IsAutoTmp() {
+				if !ir.IsAutoTmp(r.Right) {
 					r.Right = o.copyExpr(r.Right, r.Right.Type, false)
 				}
 			}
diff --git a/src/cmd/compile/internal/gc/pgen.go b/src/cmd/compile/internal/gc/pgen.go
index 38f416c1c3..6e7922ca54 100644
--- a/src/cmd/compile/internal/gc/pgen.go
+++ b/src/cmd/compile/internal/gc/pgen.go
@@ -121,7 +121,7 @@ func (s *ssafn) AllocFrame(f *ssa.Func) {
 
 	for _, l := range f.RegAlloc {
 		if ls, ok := l.(ssa.LocalSlot); ok {
-			ls.N.(*ir.Node).Name.SetUsed(true)
+			ls.N.Name.SetUsed(true)
 		}
 	}
 
@@ -517,7 +517,7 @@ func createSimpleVars(fnsym *obj.LSym, apDecls []*ir.Node) ([]*ir.Node, []*dwarf
 	var decls []*ir.Node
 	selected := make(map[*ir.Node]bool)
 	for _, n := range apDecls {
-		if n.IsAutoTmp() {
+		if ir.IsAutoTmp(n) {
 			continue
 		}
 
@@ -580,7 +580,7 @@ func createSimpleVar(fnsym *obj.LSym, n *ir.Node) *dwarf.Var {
 // createComplexVars creates recomposed DWARF vars with location lists,
 // suitable for describing optimized code.
 func createComplexVars(fnsym *obj.LSym, fn *ir.Func) ([]*ir.Node, []*dwarf.Var, map[*ir.Node]bool) {
-	debugInfo := fn.DebugInfo
+	debugInfo := fn.DebugInfo.(*ssa.FuncDebug)
 
 	// Produce a DWARF variable entry for each user variable.
 	var decls []*ir.Node
@@ -588,10 +588,10 @@ func createComplexVars(fnsym *obj.LSym, fn *ir.Func) ([]*ir.Node, []*dwarf.Var,
 	ssaVars := make(map[*ir.Node]bool)
 
 	for varID, dvar := range debugInfo.Vars {
-		n := dvar.(*ir.Node)
+		n := dvar
 		ssaVars[n] = true
 		for _, slot := range debugInfo.VarSlots[varID] {
-			ssaVars[debugInfo.Slots[slot].N.(*ir.Node)] = true
+			ssaVars[debugInfo.Slots[slot].N] = true
 		}
 
 		if dvar := createComplexVar(fnsym, fn, ssa.VarID(varID)); dvar != nil {
@@ -727,7 +727,7 @@ func preInliningDcls(fnsym *obj.LSym) []*ir.Node {
 // stack pointer, suitable for use in a DWARF location entry. This has nothing
 // to do with its offset in the user variable.
 func stackOffset(slot ssa.LocalSlot) int32 {
-	n := slot.N.(*ir.Node)
+	n := slot.N
 	var off int64
 	switch n.Class() {
 	case ir.PAUTO:
@@ -746,8 +746,8 @@ func stackOffset(slot ssa.LocalSlot) int32 {
 
 // createComplexVar builds a single DWARF variable entry and location list.
 func createComplexVar(fnsym *obj.LSym, fn *ir.Func, varID ssa.VarID) *dwarf.Var {
-	debug := fn.DebugInfo
-	n := debug.Vars[varID].(*ir.Node)
+	debug := fn.DebugInfo.(*ssa.FuncDebug)
+	n := debug.Vars[varID]
 
 	var abbrev int
 	switch n.Class() {
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 658ea28fbe..5cee3fab85 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -3080,7 +3080,7 @@ func (s *state) assign(left *ir.Node, right *ssa.Value, deref bool, skip skipMas
 	// If this assignment clobbers an entire local variable, then emit
 	// OpVarDef so liveness analysis knows the variable is redefined.
 	if base := clobberBase(left); base.Op == ir.ONAME && base.Class() != ir.PEXTERN && skip == 0 {
-		s.vars[memVar] = s.newValue1Apos(ssa.OpVarDef, types.TypeMem, base, s.mem(), !base.IsAutoTmp())
+		s.vars[memVar] = s.newValue1Apos(ssa.OpVarDef, types.TypeMem, base, s.mem(), !ir.IsAutoTmp(base))
 	}
 
 	// Left is not ssa-able. Compute its address.
@@ -3103,7 +3103,7 @@ func (s *state) assign(left *ir.Node, right *ssa.Value, deref bool, skip skipMas
 		return
 	}
 	// Treat as a store.
-	s.storeType(t, addr, right, skip, !left.IsAutoTmp())
+	s.storeType(t, addr, right, skip, !ir.IsAutoTmp(left))
 }
 
 // zeroVal returns the zero value for type t.
@@ -4860,7 +4860,7 @@ func (s *state) addr(n *ir.Node) *ssa.Value {
 			s.Fatalf("addr of undeclared ONAME %v. declared: %v", n, s.decladdrs)
 			return nil
 		case ir.PAUTO:
-			return s.newValue2Apos(ssa.OpLocalAddr, t, n, s.sp, s.mem(), !n.IsAutoTmp())
+			return s.newValue2Apos(ssa.OpLocalAddr, t, n, s.sp, s.mem(), !ir.IsAutoTmp(n))
 
 		case ir.PPARAMOUT: // Same as PAUTO -- cannot generate LEA early.
 			// ensure that we reuse symbols for out parameters so
@@ -6063,7 +6063,7 @@ func (s *state) addNamedValue(n *ir.Node, v *ssa.Value) {
 		// Don't track our marker nodes (memVar etc.).
 		return
 	}
-	if n.IsAutoTmp() {
+	if ir.IsAutoTmp(n) {
 		// Don't track temporary variables.
 		return
 	}
@@ -6476,12 +6476,13 @@ func genssa(f *ssa.Func, pp *Progs) {
 	}
 
 	if base.Ctxt.Flag_locationlists {
-		e.curfn.Func.DebugInfo = ssa.BuildFuncDebug(base.Ctxt, f, base.Debug.LocationLists > 1, stackOffset)
+		debugInfo := ssa.BuildFuncDebug(base.Ctxt, f, base.Debug.LocationLists > 1, stackOffset)
+		e.curfn.Func.DebugInfo = debugInfo
 		bstart := s.bstart
 		// Note that at this moment, Prog.Pc is a sequence number; it's
 		// not a real PC until after assembly, so this mapping has to
 		// be done later.
-		e.curfn.Func.DebugInfo.GetPC = func(b, v ssa.ID) int64 {
+		debugInfo.GetPC = func(b, v ssa.ID) int64 {
 			switch v {
 			case ssa.BlockStart.ID:
 				if b == f.Entry.ID {
@@ -6820,7 +6821,7 @@ func AutoVar(v *ssa.Value) (*ir.Node, int64) {
 	if v.Type.Size() > loc.Type.Size() {
 		v.Fatalf("spill/restore type %s doesn't fit in slot type %s", v.Type, loc.Type)
 	}
-	return loc.N.(*ir.Node), loc.Off
+	return loc.N, loc.Off
 }
 
 func AddrAuto(a *obj.Addr, v *ssa.Value) {
@@ -6975,7 +6976,7 @@ func (e *ssafn) StringData(s string) *obj.LSym {
 	return data
 }
 
-func (e *ssafn) Auto(pos src.XPos, t *types.Type) ssa.GCNode {
+func (e *ssafn) Auto(pos src.XPos, t *types.Type) *ir.Node {
 	n := tempAt(pos, e.curfn, t) // Note: adds new auto to e.curfn.Func.Dcl list
 	return n
 }
@@ -6990,7 +6991,7 @@ func (e *ssafn) SplitString(name ssa.LocalSlot) (ssa.LocalSlot, ssa.LocalSlot) {
 }
 
 func (e *ssafn) SplitInterface(name ssa.LocalSlot) (ssa.LocalSlot, ssa.LocalSlot) {
-	n := name.N.(*ir.Node)
+	n := name.N
 	u := types.Types[types.TUINTPTR]
 	t := types.NewPtr(types.Types[types.TUINT8])
 	// Split this interface up into two separate variables.
@@ -7047,7 +7048,7 @@ func (e *ssafn) SplitStruct(name ssa.LocalSlot, i int) ssa.LocalSlot {
 }
 
 func (e *ssafn) SplitArray(name ssa.LocalSlot) ssa.LocalSlot {
-	n := name.N.(*ir.Node)
+	n := name.N
 	at := name.Type
 	if at.NumElem() != 1 {
 		e.Fatalf(n.Pos, "bad array size")
@@ -7062,7 +7063,7 @@ func (e *ssafn) DerefItab(it *obj.LSym, offset int64) *obj.LSym {
 
 // SplitSlot returns a slot representing the data of parent starting at offset.
 func (e *ssafn) SplitSlot(parent *ssa.LocalSlot, suffix string, offset int64, t *types.Type) ssa.LocalSlot {
-	node := parent.N.(*ir.Node)
+	node := parent.N
 
 	if node.Class() != ir.PAUTO || node.Name.Addrtaken() {
 		// addressed things and non-autos retain their parents (i.e., cannot truly be split)
@@ -7070,7 +7071,7 @@ func (e *ssafn) SplitSlot(parent *ssa.LocalSlot, suffix string, offset int64, t
 	}
 
 	s := &types.Sym{Name: node.Sym.Name + suffix, Pkg: ir.LocalPkg}
-	n := ir.NewNameAt(parent.N.(*ir.Node).Pos, s)
+	n := ir.NewNameAt(parent.N.Pos, s)
 	s.Def = ir.AsTypesNode(n)
 	ir.AsNode(s.Def).Name.SetUsed(true)
 	n.Type = t
diff --git a/src/cmd/compile/internal/gc/typecheck.go b/src/cmd/compile/internal/gc/typecheck.go
index 78fdf100ad..318f315f16 100644
--- a/src/cmd/compile/internal/gc/typecheck.go
+++ b/src/cmd/compile/internal/gc/typecheck.go
@@ -1960,7 +1960,7 @@ func typecheck1(n *ir.Node, top int) (res *ir.Node) {
 		typecheckas(n)
 
 		// Code that creates temps does not bother to set defn, so do it here.
-		if n.Left.Op == ir.ONAME && n.Left.IsAutoTmp() {
+		if n.Left.Op == ir.ONAME && ir.IsAutoTmp(n.Left) {
 			n.Left.Name.Defn = n
 		}
 
diff --git a/src/cmd/compile/internal/ir/node.go b/src/cmd/compile/internal/ir/node.go
index e6ed178f49..cac9e6eb3e 100644
--- a/src/cmd/compile/internal/ir/node.go
+++ b/src/cmd/compile/internal/ir/node.go
@@ -13,7 +13,6 @@ import (
 	"unsafe"
 
 	"cmd/compile/internal/base"
-	"cmd/compile/internal/ssa"
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"cmd/internal/objabi"
@@ -156,14 +155,14 @@ func (n *Node) SetTChanDir(dir types.ChanDir) {
 	n.aux = uint8(dir)
 }
 
-func (n *Node) IsSynthetic() bool {
+func IsSynthetic(n *Node) bool {
 	name := n.Sym.Name
 	return name[0] == '.' || name[0] == '~'
 }
 
 // IsAutoTmp indicates if n was created by the compiler as a temporary,
 // based on the setting of the .AutoTemp flag in n's Name.
-func (n *Node) IsAutoTmp() bool {
+func IsAutoTmp(n *Node) bool {
 	if n == nil || n.Op != ONAME {
 		return false
 	}
@@ -683,7 +682,7 @@ type Func struct {
 	Closgen int
 
 	FieldTrack map[*types.Sym]struct{}
-	DebugInfo  *ssa.FuncDebug
+	DebugInfo  interface{}
 	LSym       *obj.LSym
 
 	Inl *Inline
@@ -1550,21 +1549,3 @@ func IsBlank(n *Node) bool {
 func IsMethod(n *Node) bool {
 	return n.Type.Recv() != nil
 }
-
-func (n *Node) Typ() *types.Type {
-	return n.Type
-}
-
-func (n *Node) StorageClass() ssa.StorageClass {
-	switch n.Class() {
-	case PPARAM:
-		return ssa.ClassParam
-	case PPARAMOUT:
-		return ssa.ClassParamOut
-	case PAUTO:
-		return ssa.ClassAuto
-	default:
-		base.Fatalf("untranslatable storage class for %v: %s", n, n.Class())
-		return 0
-	}
-}
diff --git a/src/cmd/compile/internal/ir/sizeof_test.go b/src/cmd/compile/internal/ir/sizeof_test.go
index c5169b9092..1ec89c338d 100644
--- a/src/cmd/compile/internal/ir/sizeof_test.go
+++ b/src/cmd/compile/internal/ir/sizeof_test.go
@@ -20,7 +20,7 @@ func TestSizeof(t *testing.T) {
 		_32bit uintptr     // size on 32bit platforms
 		_64bit uintptr     // size on 64bit platforms
 	}{
-		{Func{}, 132, 240},
+		{Func{}, 136, 248},
 		{Name{}, 32, 56},
 		{Param{}, 24, 48},
 		{Node{}, 76, 128},
diff --git a/src/cmd/compile/internal/ssa/config.go b/src/cmd/compile/internal/ssa/config.go
index 0fe0337ddf..62abbdc223 100644
--- a/src/cmd/compile/internal/ssa/config.go
+++ b/src/cmd/compile/internal/ssa/config.go
@@ -5,6 +5,7 @@
 package ssa
 
 import (
+	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"cmd/internal/objabi"
@@ -138,7 +139,7 @@ type Frontend interface {
 
 	// Auto returns a Node for an auto variable of the given type.
 	// The SSA compiler uses this function to allocate space for spills.
-	Auto(src.XPos, *types.Type) GCNode
+	Auto(src.XPos, *types.Type) *ir.Node
 
 	// Given the name for a compound type, returns the name we should use
 	// for the parts of that compound type.
@@ -178,24 +179,6 @@ type Frontend interface {
 	MyImportPath() string
 }
 
-// interface used to hold a *gc.Node (a stack variable).
-// We'd use *gc.Node directly but that would lead to an import cycle.
-type GCNode interface {
-	Typ() *types.Type
-	String() string
-	IsSynthetic() bool
-	IsAutoTmp() bool
-	StorageClass() StorageClass
-}
-
-type StorageClass uint8
-
-const (
-	ClassAuto     StorageClass = iota // local stack variable
-	ClassParam                        // argument
-	ClassParamOut                     // return value
-)
-
 const go116lateCallExpansion = true
 
 // LateCallExpansionEnabledWithin returns true if late call expansion should be tested
diff --git a/src/cmd/compile/internal/ssa/deadstore.go b/src/cmd/compile/internal/ssa/deadstore.go
index 0664013b39..0f1cd4bc9f 100644
--- a/src/cmd/compile/internal/ssa/deadstore.go
+++ b/src/cmd/compile/internal/ssa/deadstore.go
@@ -5,6 +5,7 @@
 package ssa
 
 import (
+	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
 	"cmd/internal/src"
 )
@@ -136,9 +137,9 @@ func dse(f *Func) {
 // reaches stores then we delete all the stores. The other operations will then
 // be eliminated by the dead code elimination pass.
 func elimDeadAutosGeneric(f *Func) {
-	addr := make(map[*Value]GCNode) // values that the address of the auto reaches
-	elim := make(map[*Value]GCNode) // values that could be eliminated if the auto is
-	used := make(map[GCNode]bool)   // used autos that must be kept
+	addr := make(map[*Value]*ir.Node) // values that the address of the auto reaches
+	elim := make(map[*Value]*ir.Node) // values that could be eliminated if the auto is
+	used := make(map[*ir.Node]bool)   // used autos that must be kept
 
 	// visit the value and report whether any of the maps are updated
 	visit := func(v *Value) (changed bool) {
@@ -146,8 +147,8 @@ func elimDeadAutosGeneric(f *Func) {
 		switch v.Op {
 		case OpAddr, OpLocalAddr:
 			// Propagate the address if it points to an auto.
-			n, ok := v.Aux.(GCNode)
-			if !ok || n.StorageClass() != ClassAuto {
+			n, ok := v.Aux.(*ir.Node)
+			if !ok || n.Class() != ir.PAUTO {
 				return
 			}
 			if addr[v] == nil {
@@ -157,8 +158,8 @@ func elimDeadAutosGeneric(f *Func) {
 			return
 		case OpVarDef, OpVarKill:
 			// v should be eliminated if we eliminate the auto.
-			n, ok := v.Aux.(GCNode)
-			if !ok || n.StorageClass() != ClassAuto {
+			n, ok := v.Aux.(*ir.Node)
+			if !ok || n.Class() != ir.PAUTO {
 				return
 			}
 			if elim[v] == nil {
@@ -173,8 +174,8 @@ func elimDeadAutosGeneric(f *Func) {
 			// for open-coded defers from being removed (since they
 			// may not be used by the inline code, but will be used by
 			// panic processing).
-			n, ok := v.Aux.(GCNode)
-			if !ok || n.StorageClass() != ClassAuto {
+			n, ok := v.Aux.(*ir.Node)
+			if !ok || n.Class() != ir.PAUTO {
 				return
 			}
 			if !used[n] {
@@ -221,7 +222,7 @@ func elimDeadAutosGeneric(f *Func) {
 		}
 
 		// Propagate any auto addresses through v.
-		node := GCNode(nil)
+		var node *ir.Node
 		for _, a := range args {
 			if n, ok := addr[a]; ok && !used[n] {
 				if node == nil {
@@ -298,15 +299,15 @@ func elimUnreadAutos(f *Func) {
 	// Loop over all ops that affect autos taking note of which
 	// autos we need and also stores that we might be able to
 	// eliminate.
-	seen := make(map[GCNode]bool)
+	seen := make(map[*ir.Node]bool)
 	var stores []*Value
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
-			n, ok := v.Aux.(GCNode)
+			n, ok := v.Aux.(*ir.Node)
 			if !ok {
 				continue
 			}
-			if n.StorageClass() != ClassAuto {
+			if n.Class() != ir.PAUTO {
 				continue
 			}
 
@@ -334,7 +335,7 @@ func elimUnreadAutos(f *Func) {
 
 	// Eliminate stores to unread autos.
 	for _, store := range stores {
-		n, _ := store.Aux.(GCNode)
+		n, _ := store.Aux.(*ir.Node)
 		if seen[n] {
 			continue
 		}
diff --git a/src/cmd/compile/internal/ssa/debug.go b/src/cmd/compile/internal/ssa/debug.go
index 6353f72897..9de5f427c0 100644
--- a/src/cmd/compile/internal/ssa/debug.go
+++ b/src/cmd/compile/internal/ssa/debug.go
@@ -5,6 +5,7 @@
 package ssa
 
 import (
+	"cmd/compile/internal/ir"
 	"cmd/internal/dwarf"
 	"cmd/internal/obj"
 	"encoding/hex"
@@ -24,7 +25,7 @@ type FuncDebug struct {
 	// Slots is all the slots used in the debug info, indexed by their SlotID.
 	Slots []LocalSlot
 	// The user variables, indexed by VarID.
-	Vars []GCNode
+	Vars []*ir.Node
 	// The slots that make up each variable, indexed by VarID.
 	VarSlots [][]SlotID
 	// The location list data, indexed by VarID. Must be processed by PutLocationList.
@@ -165,7 +166,7 @@ func (s *debugState) logf(msg string, args ...interface{}) {
 type debugState struct {
 	// See FuncDebug.
 	slots    []LocalSlot
-	vars     []GCNode
+	vars     []*ir.Node
 	varSlots [][]SlotID
 	lists    [][]byte
 
@@ -189,7 +190,7 @@ type debugState struct {
 	// The pending location list entry for each user variable, indexed by VarID.
 	pendingEntries []pendingEntry
 
-	varParts           map[GCNode][]SlotID
+	varParts           map[*ir.Node][]SlotID
 	blockDebug         []BlockDebug
 	pendingSlotLocs    []VarLoc
 	liveSlots          []liveSlot
@@ -346,7 +347,7 @@ func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingEnabled bool, stackOffset fu
 	}
 
 	if state.varParts == nil {
-		state.varParts = make(map[GCNode][]SlotID)
+		state.varParts = make(map[*ir.Node][]SlotID)
 	} else {
 		for n := range state.varParts {
 			delete(state.varParts, n)
@@ -360,7 +361,7 @@ func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingEnabled bool, stackOffset fu
 	state.vars = state.vars[:0]
 	for i, slot := range f.Names {
 		state.slots = append(state.slots, slot)
-		if slot.N.IsSynthetic() {
+		if ir.IsSynthetic(slot.N) {
 			continue
 		}
 
@@ -379,8 +380,8 @@ func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingEnabled bool, stackOffset fu
 	for _, b := range f.Blocks {
 		for _, v := range b.Values {
 			if v.Op == OpVarDef || v.Op == OpVarKill {
-				n := v.Aux.(GCNode)
-				if n.IsSynthetic() {
+				n := v.Aux.(*ir.Node)
+				if ir.IsSynthetic(n) {
 					continue
 				}
 
@@ -425,7 +426,7 @@ func BuildFuncDebug(ctxt *obj.Link, f *Func, loggingEnabled bool, stackOffset fu
 	state.initializeCache(f, len(state.varParts), len(state.slots))
 
 	for i, slot := range f.Names {
-		if slot.N.IsSynthetic() {
+		if ir.IsSynthetic(slot.N) {
 			continue
 		}
 		for _, value := range f.NamedValues[slot] {
@@ -717,8 +718,8 @@ func (state *debugState) processValue(v *Value, vSlots []SlotID, vReg *Register)
 
 	switch {
 	case v.Op == OpVarDef, v.Op == OpVarKill:
-		n := v.Aux.(GCNode)
-		if n.IsSynthetic() {
+		n := v.Aux.(*ir.Node)
+		if ir.IsSynthetic(n) {
 			break
 		}
 
diff --git a/src/cmd/compile/internal/ssa/export_test.go b/src/cmd/compile/internal/ssa/export_test.go
index bfe94ff160..3d142a2272 100644
--- a/src/cmd/compile/internal/ssa/export_test.go
+++ b/src/cmd/compile/internal/ssa/export_test.go
@@ -5,6 +5,7 @@
 package ssa
 
 import (
+	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"cmd/internal/obj/arm64"
@@ -65,36 +66,13 @@ type TestFrontend struct {
 	ctxt *obj.Link
 }
 
-type TestAuto struct {
-	t *types.Type
-	s string
-}
-
-func (d *TestAuto) Typ() *types.Type {
-	return d.t
-}
-
-func (d *TestAuto) String() string {
-	return d.s
-}
-
-func (d *TestAuto) StorageClass() StorageClass {
-	return ClassAuto
-}
-
-func (d *TestAuto) IsSynthetic() bool {
-	return false
-}
-
-func (d *TestAuto) IsAutoTmp() bool {
-	return true
-}
-
 func (TestFrontend) StringData(s string) *obj.LSym {
 	return nil
 }
-func (TestFrontend) Auto(pos src.XPos, t *types.Type) GCNode {
-	return &TestAuto{t: t, s: "aTestAuto"}
+func (TestFrontend) Auto(pos src.XPos, t *types.Type) *ir.Node {
+	n := ir.NewNameAt(pos, &types.Sym{Name: "aFakeAuto"})
+	n.SetClass(ir.PAUTO)
+	return n
 }
 func (d TestFrontend) SplitString(s LocalSlot) (LocalSlot, LocalSlot) {
 	return LocalSlot{N: s.N, Type: testTypes.BytePtr, Off: s.Off}, LocalSlot{N: s.N, Type: testTypes.Int, Off: s.Off + 8}
diff --git a/src/cmd/compile/internal/ssa/location.go b/src/cmd/compile/internal/ssa/location.go
index a333982389..2f456c9f89 100644
--- a/src/cmd/compile/internal/ssa/location.go
+++ b/src/cmd/compile/internal/ssa/location.go
@@ -5,6 +5,7 @@
 package ssa
 
 import (
+	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
 	"fmt"
 )
@@ -59,7 +60,7 @@ func (r *Register) GCNum() int16 {
 //                           { N: len, Type: int, Off: 0, SplitOf: parent, SplitOffset: 8}
 //                           parent = &{N: s, Type: string}
 type LocalSlot struct {
-	N    GCNode      // an ONAME *gc.Node representing a stack location.
+	N    *ir.Node    // an ONAME *gc.Node representing a stack location.
 	Type *types.Type // type of slot
 	Off  int64       // offset of slot in N
 
diff --git a/src/cmd/compile/internal/ssa/nilcheck.go b/src/cmd/compile/internal/ssa/nilcheck.go
index d1bad529e7..e0ae0454ef 100644
--- a/src/cmd/compile/internal/ssa/nilcheck.go
+++ b/src/cmd/compile/internal/ssa/nilcheck.go
@@ -5,6 +5,7 @@
 package ssa
 
 import (
+	"cmd/compile/internal/ir"
 	"cmd/internal/objabi"
 	"cmd/internal/src"
 )
@@ -235,7 +236,7 @@ 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().HasPointers()) {
+				if v.Op == OpVarKill || v.Op == OpVarLive || (v.Op == OpVarDef && !v.Aux.(*ir.Node).Type.HasPointers()) {
 					// These ops don't really change memory.
 					continue
 					// Note: OpVarDef requires that the defined variable not have pointers.
diff --git a/src/cmd/compile/internal/ssa/regalloc.go b/src/cmd/compile/internal/ssa/regalloc.go
index 4ed884c3e7..9841883939 100644
--- a/src/cmd/compile/internal/ssa/regalloc.go
+++ b/src/cmd/compile/internal/ssa/regalloc.go
@@ -114,6 +114,7 @@
 package ssa
 
 import (
+	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
 	"cmd/internal/objabi"
 	"cmd/internal/src"
@@ -1248,7 +1249,7 @@ func (s *regAllocState) regalloc(f *Func) {
 					// This forces later liveness analysis to make the
 					// value live at this point.
 					v.SetArg(0, s.makeSpill(a, b))
-				} else if _, ok := a.Aux.(GCNode); ok && vi.rematerializeable {
+				} else if _, ok := a.Aux.(*ir.Node); ok && vi.rematerializeable {
 					// Rematerializeable value with a gc.Node. This is the address of
 					// a stack object (e.g. an LEAQ). Keep the object live.
 					// Change it to VarLive, which is what plive expects for locals.
diff --git a/src/cmd/compile/internal/ssa/sizeof_test.go b/src/cmd/compile/internal/ssa/sizeof_test.go
index 60ada011e3..a27002ee3a 100644
--- a/src/cmd/compile/internal/ssa/sizeof_test.go
+++ b/src/cmd/compile/internal/ssa/sizeof_test.go
@@ -22,7 +22,7 @@ func TestSizeof(t *testing.T) {
 	}{
 		{Value{}, 72, 112},
 		{Block{}, 164, 304},
-		{LocalSlot{}, 32, 48},
+		{LocalSlot{}, 28, 40},
 		{valState{}, 28, 40},
 	}
 
diff --git a/src/cmd/compile/internal/ssa/stackalloc.go b/src/cmd/compile/internal/ssa/stackalloc.go
index 406a3c3ea5..eee0a21a66 100644
--- a/src/cmd/compile/internal/ssa/stackalloc.go
+++ b/src/cmd/compile/internal/ssa/stackalloc.go
@@ -7,6 +7,7 @@
 package ssa
 
 import (
+	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
 	"cmd/internal/src"
 	"fmt"
@@ -156,7 +157,7 @@ func (s *stackAllocState) stackalloc() {
 		if v.Aux == nil {
 			f.Fatalf("%s has nil Aux\n", v.LongString())
 		}
-		loc := LocalSlot{N: v.Aux.(GCNode), Type: v.Type, Off: v.AuxInt}
+		loc := LocalSlot{N: v.Aux.(*ir.Node), Type: v.Type, Off: v.AuxInt}
 		if f.pass.debug > stackDebug {
 			fmt.Printf("stackalloc %s to %s\n", v, loc)
 		}