cmd/compile: change Func.{Enter,Exit} from NodeList to slice

Introduces a new types Nodes that can be used to replace NodeList.

Update #14473.

Change-Id: Id77c5dcae0cbeb898ba12dd46bd400aad408871c
Reviewed-on: https://go-review.googlesource.com/19969Reviewed-by: David Crawshaw <crawshaw@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/cgen.go

@@ -2621,7 +2621,7 @@ func cgen_ret(n *Node) {
 	if hasdefer {
 		Ginscall(Deferreturn, 0)
 	}
-	Genlist(Curfn.Func.Exit)
+	Genslice(Curfn.Func.Exit.Slice())
 	p := Thearch.Gins(obj.ARET, nil, nil)
 	if n != nil && n.Op == ORETJMP {
 		p.To.Type = obj.TYPE_MEM

src/cmd/compile/internal/gc/closure.go

@@ -223,7 +223,7 @@ func capturevars(xfunc *Node) {
 	lineno = xfunc.Lineno
 
 	func_ := xfunc.Func.Closure
-	func_.Func.Enter = nil
+	func_.Func.Enter.Set(nil)
 	for _, v := range func_.Func.Cvars() {
 		if v.Type == nil {
 			// if v->type is nil, it means v looked like it was
@@ -265,7 +265,7 @@ func capturevars(xfunc *Node) {
 		}
 
 		typecheck(&outer, Erv)
-		func_.Func.Enter = list(func_.Func.Enter, outer)
+		func_.Func.Enter.Append(outer)
 	}
 
 	lineno = int32(lno)
@@ -350,9 +350,7 @@ func transformclosure(xfunc *Node) {
 		xfunc.Type = f.Type // update type of ODCLFUNC
 	} else {
 		// The closure is not called, so it is going to stay as closure.
-		nvar := 0
-
-		var body *NodeList
+		var body []*Node
 		offset := int64(Widthptr)
 		var addr *Node
 		var cv *Node
@@ -360,7 +358,6 @@ func transformclosure(xfunc *Node) {
 			if v.Op == OXXX {
 				continue
 			}
-			nvar++
 
 			// cv refers to the field inside of closure OSTRUCTLIT.
 			cv = Nod(OCLOSUREVAR, nil, nil)
@@ -378,7 +375,7 @@ func transformclosure(xfunc *Node) {
 				v.Class = PAUTO
 				v.Ullman = 1
 				xfunc.Func.Dcl = append(xfunc.Func.Dcl, v)
-				body = list(body, Nod(OAS, v, cv))
+				body = append(body, Nod(OAS, v, cv))
 			} else {
 				// Declare variable holding addresses taken from closure
 				// and initialize in entry prologue.
@@ -392,14 +389,16 @@ func transformclosure(xfunc *Node) {
 				if v.Name.Byval {
 					cv = Nod(OADDR, cv, nil)
 				}
-				body = list(body, Nod(OAS, addr, cv))
+				body = append(body, Nod(OAS, addr, cv))
 			}
 		}
 
-		typechecklist(body, Etop)
-		walkstmtlist(body)
-		xfunc.Func.Enter = body
-		xfunc.Func.Needctxt = nvar > 0
+		if len(body) > 0 {
+			typecheckslice(body, Etop)
+			walkstmtslice(body)
+			xfunc.Func.Enter.Set(body)
+			xfunc.Func.Needctxt = true
+		}
 	}
 
 	lineno = int32(lno)
@@ -443,7 +442,7 @@ func walkclosure(func_ *Node, init **NodeList) *Node {
 	clos := Nod(OCOMPLIT, nil, Nod(OIND, typ, nil))
 	clos.Esc = func_.Esc
 	clos.Right.Implicit = true
-	clos.List = concat(list1(Nod(OCFUNC, func_.Func.Closure.Func.Nname, nil)), func_.Func.Enter)
+	clos.List = concat(list1(Nod(OCFUNC, func_.Func.Closure.Func.Nname, nil)), func_.Func.Enter.NodeList())
 
 	// Force type conversion from *struct to the func type.
 	clos = Nod(OCONVNOP, clos, nil)

src/cmd/compile/internal/gc/fmt.go

@@ -1729,10 +1729,42 @@ func Hconv(l *NodeList, flag int) string {
 	return buf.String()
 }
 
+func Hconvslice(l []*Node, flag int) string {
+	if len(l) == 0 && fmtmode == FDbg {
+		return "<nil>"
+	}
+
+	sf := flag
+	sm, sb := setfmode(&flag)
+	sep := "; "
+	if fmtmode == FDbg {
+		sep = "\n"
+	} else if flag&obj.FmtComma != 0 {
+		sep = ", "
+	}
+
+	var buf bytes.Buffer
+	for i, n := range l {
+		buf.WriteString(Nconv(n, 0))
+		if i+1 < len(l) {
+			buf.WriteString(sep)
+		}
+	}
+
+	flag = sf
+	fmtbody = sb
+	fmtmode = sm
+	return buf.String()
+}
+
 func dumplist(s string, l *NodeList) {
 	fmt.Printf("%s%v\n", s, Hconv(l, obj.FmtSign))
 }
 
+func dumpslice(s string, l []*Node) {
+	fmt.Printf("%s%v\n", s, Hconvslice(l, obj.FmtSign))
+}
+
 func Dump(s string, n *Node) {
 	fmt.Printf("%s [%p]%v\n", s, n, Nconv(n, obj.FmtSign))
 }

src/cmd/compile/internal/gc/gen.go

@@ -219,6 +219,12 @@ func Genlist(l *NodeList) {
 	}
 }
 
+func Genslice(l []*Node) {
+	for _, n := range l {
+		gen(n)
+	}
+}
+
 // generate code to start new proc running call n.
 func cgen_proc(n *Node, proc int) {
 	switch n.Left.Op {

src/cmd/compile/internal/gc/pgen.go

@@ -471,7 +471,7 @@ func compile(fn *Node) {
 		}
 	}
 
-	Genlist(Curfn.Func.Enter)
+	Genslice(Curfn.Func.Enter.Slice())
 	Genlist(Curfn.Nbody)
 	gclean()
 	checklabels()

src/cmd/compile/internal/gc/racewalk.go

@@ -58,7 +58,7 @@ func instrument(fn *Node) {
 		instrumentlist(fn.Nbody, nil)
 
 		// nothing interesting for race detector in fn->enter
-		instrumentlist(fn.Func.Exit, nil)
+		instrumentslice(fn.Func.Exit.Slice(), nil)
 	}
 
 	if flag_race != 0 {
@@ -71,18 +71,18 @@ func instrument(fn *Node) {
 		nodpc.Type = Types[TUINTPTR]
 		nodpc.Xoffset = int64(-Widthptr)
 		nd := mkcall("racefuncenter", nil, nil, nodpc)
-		fn.Func.Enter = concat(list1(nd), fn.Func.Enter)
+		fn.Func.Enter.Set(append([]*Node{nd}, fn.Func.Enter.Slice()...))
 		nd = mkcall("racefuncexit", nil, nil)
-		fn.Func.Exit = list(fn.Func.Exit, nd)
+		fn.Func.Exit.Append(nd)
 	}
 
 	if Debug['W'] != 0 {
 		s := fmt.Sprintf("after instrument %v", fn.Func.Nname.Sym)
 		dumplist(s, fn.Nbody)
 		s = fmt.Sprintf("enter %v", fn.Func.Nname.Sym)
-		dumplist(s, fn.Func.Enter)
+		dumpslice(s, fn.Func.Enter.Slice())
 		s = fmt.Sprintf("exit %v", fn.Func.Nname.Sym)
-		dumplist(s, fn.Func.Exit)
+		dumpslice(s, fn.Func.Exit.Slice())
 	}
 }
 
@@ -100,6 +100,18 @@ func instrumentlist(l *NodeList, init **NodeList) {
 	}
 }
 
+func instrumentslice(l []*Node, init **NodeList) {
+	for i := range l {
+		var instr *NodeList
+		instrumentnode(&l[i], &instr, 0, 0)
+		if init == nil {
+			l[i].Ninit = concat(l[i].Ninit, instr)
+		} else {
+			*init = concat(*init, instr)
+		}
+	}
+}
+
 // walkexpr and walkstmt combined
 // walks the tree and adds calls to the
 // instrumentation code to top-level (statement) nodes' init

src/cmd/compile/internal/gc/syntax.go

@@ -149,8 +149,8 @@ type Param struct {
 // Func holds Node fields used only with function-like nodes.
 type Func struct {
 	Shortname  *Node
-	Enter      *NodeList
-	Exit       *NodeList
+	Enter      Nodes
+	Exit       Nodes
 	cvars      *[]*Node // closure params
 	Dcl        []*Node  // autodcl for this func/closure
 	Inldcl     *[]*Node // copy of dcl for use in inlining
@@ -506,3 +506,55 @@ func count(l *NodeList) int {
 	}
 	return int(n)
 }
+
+// Nodes is a pointer to a slice of *Node.
+// For fields that are not used in most nodes, this is used instead of
+// a slice to save space.
+type Nodes struct{ slice *[]*Node }
+
+// Slice returns the entries in Nodes as a slice.
+// Changes to the slice entries (as in s[i] = n) will be reflected in
+// the Nodes.
+func (n *Nodes) Slice() []*Node {
+	if n.slice == nil {
+		return nil
+	}
+	return *n.slice
+}
+
+// NodeList returns the entries in Nodes as a NodeList.
+// Changes to the NodeList entries (as in l.N = n) will *not* be
+// reflect in the Nodes.
+// This wastes memory and should be used as little as possible.
+func (n *Nodes) NodeList() *NodeList {
+	if n.slice == nil {
+		return nil
+	}
+	var ret *NodeList
+	for _, n := range *n.slice {
+		ret = list(ret, n)
+	}
+	return ret
+}
+
+// Set sets Nodes to a slice.
+// This takes ownership of the slice.
+func (n *Nodes) Set(s []*Node) {
+	if len(s) == 0 {
+		n.slice = nil
+	} else {
+		n.slice = &s
+	}
+}
+
+// Append appends entries to Nodes.
+// If a slice is passed in, this will take ownership of it.
+func (n *Nodes) Append(a ...*Node) {
+	if n.slice == nil {
+		if len(a) > 0 {
+			n.slice = &a
+		}
+	} else {
+		*n.slice = append(*n.slice, a...)
+	}
+}

src/cmd/compile/internal/gc/typecheck.go

@@ -40,6 +40,12 @@ func typechecklist(l *NodeList, top int) {
 	}
 }
 
+func typecheckslice(l []*Node, top int) {
+	for i := range l {
+		typecheck(&l[i], top)
+	}
+}
+
 var _typekind = []string{
 	TINT:        "int",
 	TUINT:       "uint",

src/cmd/compile/internal/gc/walk.go

@@ -71,9 +71,9 @@ func walk(fn *Node) {
 	}
 
 	heapmoves()
-	if Debug['W'] != 0 && Curfn.Func.Enter != nil {
+	if Debug['W'] != 0 && len(Curfn.Func.Enter.Slice()) > 0 {
 		s := fmt.Sprintf("enter %v", Curfn.Func.Nname.Sym)
-		dumplist(s, Curfn.Func.Enter)
+		dumpslice(s, Curfn.Func.Enter.Slice())
 	}
 }
 
@@ -83,6 +83,12 @@ func walkstmtlist(l *NodeList) {
 	}
 }
 
+func walkstmtslice(l []*Node) {
+	for i := range l {
+		walkstmt(&l[i])
+	}
+}
+
 func samelist(a *NodeList, b *NodeList) bool {
 	for ; a != nil && b != nil; a, b = a.Next, b.Next {
 		if a.N != b.N {
@@ -320,7 +326,7 @@ func walkstmt(np **Node) {
 			ll := ascompatee(n.Op, rl, n.List, &n.Ninit)
 			n.List = reorder3(ll)
 			for lr := n.List; lr != nil; lr = lr.Next {
-				lr.N = applywritebarrier(lr.N, &n.Ninit)
+				lr.N = applywritebarrier(lr.N)
 			}
 			break
 		}
@@ -588,9 +594,9 @@ opswitch:
 			// transformclosure already did all preparation work.
 
 			// Prepend captured variables to argument list.
-			n.List = concat(n.Left.Func.Enter, n.List)
+			n.List = concat(n.Left.Func.Enter.NodeList(), n.List)
 
-			n.Left.Func.Enter = nil
+			n.Left.Func.Enter.Set(nil)
 
 			// Replace OCLOSURE with ONAME/PFUNC.
 			n.Left = n.Left.Func.Closure.Func.Nname
@@ -724,7 +730,7 @@ opswitch:
 			r := convas(Nod(OAS, n.Left, n.Right), init)
 			r.Dodata = n.Dodata
 			n = r
-			n = applywritebarrier(n, init)
+			n = applywritebarrier(n)
 		}
 
 	case OAS2:
@@ -735,7 +741,7 @@ opswitch:
 		ll := ascompatee(OAS, n.List, n.Rlist, init)
 		ll = reorder3(ll)
 		for lr := ll; lr != nil; lr = lr.Next {
-			lr.N = applywritebarrier(lr.N, init)
+			lr.N = applywritebarrier(lr.N)
 		}
 		n = liststmt(ll)
 
@@ -750,7 +756,7 @@ opswitch:
 
 		ll := ascompatet(n.Op, n.List, &r.Type, 0, init)
 		for lr := ll; lr != nil; lr = lr.Next {
-			lr.N = applywritebarrier(lr.N, init)
+			lr.N = applywritebarrier(lr.N)
 		}
 		n = liststmt(concat(list1(r), ll))
 
@@ -2133,7 +2139,7 @@ func needwritebarrier(l *Node, r *Node) bool {
 
 // TODO(rsc): Perhaps componentgen should run before this.
 
-func applywritebarrier(n *Node, init **NodeList) *Node {
+func applywritebarrier(n *Node) *Node {
 	if n.Left != nil && n.Right != nil && needwritebarrier(n.Left, n.Right) {
 		if Debug_wb > 1 {
 			Warnl(int(n.Lineno), "marking %v for barrier", Nconv(n.Left, 0))
@@ -2542,12 +2548,12 @@ func vmatch1(l *Node, r *Node) bool {
 // walk through argin parameters.
 // generate and return code to allocate
 // copies of escaped parameters to the heap.
-func paramstoheap(argin **Type, out int) *NodeList {
+func paramstoheap(argin **Type, out int) []*Node {
 	var savet Iter
 	var v *Node
 	var as *Node
 
-	var nn *NodeList
+	var nn []*Node
 	for t := Structfirst(&savet, argin); t != nil; t = structnext(&savet) {
 		v = t.Nname
 		if v != nil && v.Sym != nil && v.Sym.Name[0] == '~' && v.Sym.Name[1] == 'r' { // unnamed result
@@ -2560,7 +2566,7 @@ func paramstoheap(argin **Type, out int) *NodeList {
 			// Defer might stop a panic and show the
 			// return values as they exist at the time of panic.
 			// Make sure to zero them on entry to the function.
-			nn = list(nn, Nod(OAS, nodarg(t, 1), nil))
+			nn = append(nn, Nod(OAS, nodarg(t, 1), nil))
 		}
 
 		if v == nil || v.Class&PHEAP == 0 {
@@ -2574,13 +2580,13 @@ func paramstoheap(argin **Type, out int) *NodeList {
 		if prealloc[v] == nil {
 			prealloc[v] = callnew(v.Type)
 		}
-		nn = list(nn, Nod(OAS, v.Name.Heapaddr, prealloc[v]))
+		nn = append(nn, Nod(OAS, v.Name.Heapaddr, prealloc[v]))
 		if v.Class&^PHEAP != PPARAMOUT {
 			as = Nod(OAS, v, v.Name.Param.Stackparam)
 			v.Name.Param.Stackparam.Typecheck = 1
 			typecheck(&as, Etop)
-			as = applywritebarrier(as, &nn)
-			nn = list(nn, as)
+			as = applywritebarrier(as)
+			nn = append(nn, as)
 		}
 	}
 
@@ -2588,17 +2594,17 @@ func paramstoheap(argin **Type, out int) *NodeList {
 }
 
 // walk through argout parameters copying back to stack
-func returnsfromheap(argin **Type) *NodeList {
+func returnsfromheap(argin **Type) []*Node {
 	var savet Iter
 	var v *Node
 
-	var nn *NodeList
+	var nn []*Node
 	for t := Structfirst(&savet, argin); t != nil; t = structnext(&savet) {
 		v = t.Nname
 		if v == nil || v.Class != PHEAP|PPARAMOUT {
 			continue
 		}
-		nn = list(nn, Nod(OAS, v.Name.Param.Stackparam, v))
+		nn = append(nn, Nod(OAS, v.Name.Param.Stackparam, v))
 	}
 
 	return nn
@@ -2611,11 +2617,11 @@ func heapmoves() {
 	lno := lineno
 	lineno = Curfn.Lineno
 	nn := paramstoheap(getthis(Curfn.Type), 0)
-	nn = concat(nn, paramstoheap(getinarg(Curfn.Type), 0))
-	nn = concat(nn, paramstoheap(Getoutarg(Curfn.Type), 1))
-	Curfn.Func.Enter = concat(Curfn.Func.Enter, nn)
+	nn = append(nn, paramstoheap(getinarg(Curfn.Type), 0)...)
+	nn = append(nn, paramstoheap(Getoutarg(Curfn.Type), 1)...)
+	Curfn.Func.Enter.Append(nn...)
 	lineno = Curfn.Func.Endlineno
-	Curfn.Func.Exit = returnsfromheap(Getoutarg(Curfn.Type))
+	Curfn.Func.Exit.Append(returnsfromheap(Getoutarg(Curfn.Type))...)
 	lineno = lno
 }