cmd/compile: convert cgen/gen/pgen and friends to nodeListSeq

Added Seq method to nodeListIterator. Added new functions nodeSeqLen,
nodeSeqFirst, nodeSeqSecond. Allow nil as source argument to setNodeSeq.

Change-Id: Ifc1cd4d7207b7a125b3830c92c4d6d6f00eedd54
Reviewed-on: https://go-review.googlesource.com/20195Reviewed-by: David Crawshaw <crawshaw@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

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

@@ -1753,7 +1753,7 @@ func Bvgen(n, res *Node, wantTrue bool) {
 func bvgenjump(n, res *Node, wantTrue, geninit bool) {
 	init := n.Ninit
 	if !geninit {
-		n.Ninit = nil
+		setNodeSeq(&n.Ninit, nil)
 	}
 	p1 := Gbranch(obj.AJMP, nil, 0)
 	p2 := Pc
@@ -1763,7 +1763,7 @@ func bvgenjump(n, res *Node, wantTrue, geninit bool) {
 	Bgen(n, wantTrue, 0, p2)
 	Thearch.Gmove(Nodbool(false), res)
 	Patch(p3, Pc)
-	n.Ninit = init
+	setNodeSeq(&n.Ninit, init)
 }
 
 // bgenx is the backend for Bgen and Bvgen.
@@ -1921,11 +1921,11 @@ func bgenx(n, res *Node, wantTrue bool, likely int, to *obj.Prog) {
 		if Isfloat[nr.Type.Etype] {
 			// Brcom is not valid on floats when NaN is involved.
 			ll := n.Ninit // avoid re-genning Ninit
-			n.Ninit = nil
+			setNodeSeq(&n.Ninit, nil)
 			if genval {
 				bgenx(n, res, true, likely, to)
 				Thearch.Gins(Thearch.Optoas(OXOR, Types[TUINT8]), Nodintconst(1), res) // res = !res
-				n.Ninit = ll
+				setNodeSeq(&n.Ninit, ll)
 				return
 			}
 			p1 := Gbranch(obj.AJMP, nil, 0)
@@ -1934,7 +1934,7 @@ func bgenx(n, res *Node, wantTrue bool, likely int, to *obj.Prog) {
 			bgenx(n, res, true, -likely, p2)
 			Patch(Gbranch(obj.AJMP, nil, 0), to)
 			Patch(p2, Pc)
-			n.Ninit = ll
+			setNodeSeq(&n.Ninit, ll)
 			return
 		}
 
@@ -2621,7 +2621,7 @@ func cgen_ret(n *Node) {
 	if hasdefer {
 		Ginscall(Deferreturn, 0)
 	}
-	Genslice(Curfn.Func.Exit.Slice())
+	Genlist(Curfn.Func.Exit)
 	p := Thearch.Gins(obj.ARET, nil, nil)
 	if n != nil && n.Op == ORETJMP {
 		p.To.Type = obj.TYPE_MEM
@@ -2803,13 +2803,13 @@ func cgen_append(n, res *Node) {
 		Dump("cgen_append-n", n)
 		Dump("cgen_append-res", res)
 	}
-	if res.Op != ONAME && !samesafeexpr(res, n.List.N) {
+	if res.Op != ONAME && !samesafeexpr(res, nodeSeqFirst(n.List)) {
 		Dump("cgen_append-n", n)
 		Dump("cgen_append-res", res)
 		Fatalf("append not lowered")
 	}
-	for l := n.List; l != nil; l = l.Next {
-		if l.N.Ullman >= UINF {
+	for it := nodeSeqIterate(n.List); !it.Done(); it.Next() {
+		if it.N().Ullman >= UINF {
 			Fatalf("append with function call arguments")
 		}
 	}
@@ -2818,7 +2818,7 @@ func cgen_append(n, res *Node) {
 	//
 	// If res and src are the same, we can avoid writing to base and cap
 	// unless we grow the underlying array.
-	needFullUpdate := !samesafeexpr(res, n.List.N)
+	needFullUpdate := !samesafeexpr(res, nodeSeqFirst(n.List))
 
 	// Copy src triple into base, len, cap.
 	base := temp(Types[Tptr])
@@ -2826,7 +2826,7 @@ func cgen_append(n, res *Node) {
 	cap := temp(Types[TUINT])
 
 	var src Node
-	Igen(n.List.N, &src, nil)
+	Igen(nodeSeqFirst(n.List), &src, nil)
 	src.Type = Types[Tptr]
 	Thearch.Gmove(&src, base)
 	src.Type = Types[TUINT]
@@ -2839,7 +2839,7 @@ func cgen_append(n, res *Node) {
 	var rlen Node
 	Regalloc(&rlen, Types[TUINT], nil)
 	Thearch.Gmove(len, &rlen)
-	Thearch.Ginscon(Thearch.Optoas(OADD, Types[TUINT]), int64(count(n.List)-1), &rlen)
+	Thearch.Ginscon(Thearch.Optoas(OADD, Types[TUINT]), int64(nodeSeqLen(n.List)-1), &rlen)
 	p := Thearch.Ginscmp(OLE, Types[TUINT], &rlen, cap, +1)
 	// Note: rlen and src are Regrealloc'ed below at the target of the
 	// branch we just emitted; do not reuse these Go variables for
@@ -2909,7 +2909,7 @@ func cgen_append(n, res *Node) {
 	dst.Xoffset += int64(Widthptr)
 	Regalloc(&r1, Types[TUINT], nil)
 	Thearch.Gmove(len, &r1)
-	Thearch.Ginscon(Thearch.Optoas(OADD, Types[TUINT]), int64(count(n.List)-1), &r1)
+	Thearch.Ginscon(Thearch.Optoas(OADD, Types[TUINT]), int64(nodeSeqLen(n.List)-1), &r1)
 	Thearch.Gmove(&r1, &dst)
 	Regfree(&r1)
 	dst.Xoffset += int64(Widthptr)
@@ -2947,7 +2947,9 @@ func cgen_append(n, res *Node) {
 	// is not going to use a write barrier.
 	i := 0
 	var r2 Node
-	for l := n.List.Next; l != nil; l = l.Next {
+	it := nodeSeqIterate(n.List)
+	it.Next()
+	for ; !it.Done(); it.Next() {
 		Regalloc(&r1, Types[Tptr], nil)
 		Thearch.Gmove(base, &r1)
 		Regalloc(&r2, Types[TUINT], nil)
@@ -2968,7 +2970,7 @@ func cgen_append(n, res *Node) {
 
 		r1.Op = OINDREG
 		r1.Type = res.Type.Type
-		cgen_wb(l.N, &r1, needwritebarrier(&r1, l.N))
+		cgen_wb(it.N(), &r1, needwritebarrier(&r1, it.N()))
 		Regfree(&r1)
 		i++
 	}

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

@@ -215,15 +215,9 @@ func stmtlabel(n *Node) *Label {
 }
 
 // compile statements
-func Genlist(l *NodeList) {
-	for ; l != nil; l = l.Next {
-		gen(l.N)
-	}
-}
-
-func Genslice(l []*Node) {
-	for _, n := range l {
-		gen(n)
+func Genlist(l nodesOrNodeList) {
+	for it := nodeSeqIterate(l); !it.Done(); it.Next() {
+		gen(it.N())
 	}
 }
 
@@ -445,8 +439,8 @@ func cgen_dottype(n *Node, res, resok *Node, wb bool) {
 		call := Nod(OCALLFUNC, fn, nil)
 		r1.Type = byteptr
 		r2.Type = byteptr
-		call.List = list(list(list1(&r1), &r2), typename(n.Left.Type))
-		call.List = ascompatte(OCALLFUNC, call, false, getinarg(fn.Type), call.List, 0, nil)
+		setNodeSeq(&call.List, list(list(list1(&r1), &r2), typename(n.Left.Type)))
+		setNodeSeq(&call.List, ascompatte(OCALLFUNC, call, false, getinarg(fn.Type), call.List, 0, nil))
 		gen(call)
 		Regfree(&r1)
 		Regfree(&r2)
@@ -531,8 +525,8 @@ func Cgen_As2dottype(n, res, resok *Node) {
 	fn := syslook("panicdottype", 0)
 	dowidth(fn.Type)
 	call := Nod(OCALLFUNC, fn, nil)
-	call.List = list(list(list1(&r1), &r2), typename(n.Left.Type))
-	call.List = ascompatte(OCALLFUNC, call, false, getinarg(fn.Type), call.List, 0, nil)
+	setNodeSeq(&call.List, list(list(list1(&r1), &r2), typename(n.Left.Type)))
+	setNodeSeq(&call.List, ascompatte(OCALLFUNC, call, false, getinarg(fn.Type), call.List, 0, nil))
 	gen(call)
 	Regfree(&r1)
 	Regfree(&r2)
@@ -644,7 +638,7 @@ func gen(n *Node) {
 		goto ret
 	}
 
-	if n.Ninit != nil {
+	if nodeSeqLen(n.Ninit) > 0 {
 		Genlist(n.Ninit)
 	}
 
@@ -779,7 +773,7 @@ func gen(n *Node) {
 		gen(n.Right)                     // contin:	incr
 		Patch(p1, Pc)                    // test:
 		Bgen(n.Left, false, -1, breakpc) //		if(!test) goto break
-		Genslice(n.Nbody.Slice())        //		body
+		Genlist(n.Nbody)                 //		body
 		gjmp(continpc)
 		Patch(breakpc, Pc) // done:
 		continpc = scontin
@@ -794,7 +788,7 @@ func gen(n *Node) {
 		p2 := gjmp(nil)                         // p2:		goto else
 		Patch(p1, Pc)                           // test:
 		Bgen(n.Left, false, int(-n.Likely), p2) //		if(!test) goto p2
-		Genslice(n.Nbody.Slice())               //		then
+		Genlist(n.Nbody)                        //		then
 		p3 := gjmp(nil)                         //		goto done
 		Patch(p2, Pc)                           // else:
 		Genlist(n.Rlist)                        //		else
@@ -811,9 +805,9 @@ func gen(n *Node) {
 			lab.Breakpc = breakpc
 		}
 
-		Patch(p1, Pc)             // test:
-		Genslice(n.Nbody.Slice()) //		switch(test) body
-		Patch(breakpc, Pc)        // done:
+		Patch(p1, Pc)      // test:
+		Genlist(n.Nbody)   //		switch(test) body
+		Patch(breakpc, Pc) // done:
 		breakpc = sbreak
 		if lab != nil {
 			lab.Breakpc = nil
@@ -830,9 +824,9 @@ func gen(n *Node) {
 			lab.Breakpc = breakpc
 		}
 
-		Patch(p1, Pc)             // test:
-		Genslice(n.Nbody.Slice()) //		select() body
-		Patch(breakpc, Pc)        // done:
+		Patch(p1, Pc)      // test:
+		Genlist(n.Nbody)   //		select() body
+		Patch(breakpc, Pc) // done:
 		breakpc = sbreak
 		if lab != nil {
 			lab.Breakpc = nil
@@ -851,7 +845,7 @@ func gen(n *Node) {
 		Cgen_as_wb(n.Left, n.Right, true)
 
 	case OAS2DOTTYPE:
-		cgen_dottype(n.Rlist.N, n.List.N, n.List.Next.N, needwritebarrier(n.List.N, n.Rlist.N))
+		cgen_dottype(nodeSeqFirst(n.Rlist), nodeSeqFirst(n.List), nodeSeqSecond(n.List), needwritebarrier(nodeSeqFirst(n.List), nodeSeqFirst(n.Rlist)))
 
 	case OCALLMETH:
 		cgen_callmeth(n, 0)

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

@@ -491,8 +491,8 @@ func compile(fn *Node) {
 		ssafn.Free()
 		return
 	}
-	Genslice(Curfn.Func.Enter.Slice())
-	Genslice(Curfn.Nbody.Slice())
+	Genlist(Curfn.Func.Enter)
+	Genlist(Curfn.Nbody)
 	gclean()
 	checklabels()
 	if nerrors != 0 {

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

@@ -520,6 +520,9 @@ type nodeSeqIterator interface {
 	P() **Node
 	// Return the number of items remaining in the iteration.
 	Len() int
+	// Return the remaining items as a sequence.
+	// This will have the same type as that passed to nodeSeqIterate.
+	Seq() nodesOrNodeList
 }
 
 // nodeListIterator is a type that implements nodeSeqIterator using a
@@ -548,6 +551,10 @@ func (nli *nodeListIterator) Len() int {
 	return count(nli.l)
 }
 
+func (nli *nodeListIterator) Seq() nodesOrNodeList {
+	return nli.l
+}
+
 // nodesIterator implements nodeSeqIterator using a Nodes.
 type nodesIterator struct {
 	n Nodes
@@ -574,7 +581,13 @@ func (ni *nodesIterator) Len() int {
 	return len(ni.n.Slice())
 }
 
-// nodeSeqIterate returns an iterator over either a *Nodelist or a *Nodes.
+func (ni *nodesIterator) Seq() nodesOrNodeList {
+	var r Nodes
+	r.Set(ni.n.Slice()[ni.i:])
+	return r
+}
+
+// nodeSeqIterate returns an iterator over either a *NodeList or a Nodes.
 func nodeSeqIterate(ns nodesOrNodeList) nodeSeqIterator {
 	switch ns := ns.(type) {
 	case *NodeList:
@@ -586,12 +599,64 @@ func nodeSeqIterate(ns nodesOrNodeList) nodeSeqIterator {
 	}
 }
 
+// nodeSeqLen returns the length of either a *NodeList or a Nodes.
+func nodeSeqLen(ns nodesOrNodeList) int {
+	switch ns := ns.(type) {
+	case *NodeList:
+		return count(ns)
+	case Nodes:
+		return len(ns.Slice())
+	default:
+		panic("can't happen")
+	}
+}
+
+// nodeSeqFirst returns the first element of either a *NodeList or a Nodes.
+// It panics if the sequence is empty.
+func nodeSeqFirst(ns nodesOrNodeList) *Node {
+	switch ns := ns.(type) {
+	case *NodeList:
+		return ns.N
+	case Nodes:
+		return ns.Slice()[0]
+	default:
+		panic("can't happen")
+	}
+}
+
+// nodeSeqSecond returns the second element of either a *NodeList or a Nodes.
+// It panics if the sequence has fewer than two elements.
+func nodeSeqSecond(ns nodesOrNodeList) *Node {
+	switch ns := ns.(type) {
+	case *NodeList:
+		return ns.Next.N
+	case Nodes:
+		return ns.Slice()[1]
+	default:
+		panic("can't happen")
+	}
+}
+
 // setNodeSeq implements *a = b.
 // a must have type **NodeList, *Nodes, or *[]*Node.
-// b must have type *NodeList, Nodes, or []*Node.
+// b must have type *NodeList, Nodes, []*Node, or nil.
 // This is an interim function during the transition from NodeList to Nodes.
 // TODO(iant): Remove when transition is complete.
 func setNodeSeq(a nodesOrNodeListPtr, b nodesOrNodeList) {
+	if b == nil {
+		switch a := a.(type) {
+		case **NodeList:
+			*a = nil
+		case *Nodes:
+			a.Set(nil)
+		case *[]*Node:
+			*a = nil
+		default:
+			panic("can't happen")
+		}
+		return
+	}
+
 	// Simplify b to either *Nodelist or []*Node.
 	if n, ok := b.(Nodes); ok {
 		b = n.Slice()

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

@@ -1717,7 +1717,7 @@ func ascompatet(op Op, nl *NodeList, nr **Type, fp int, init **NodeList) *NodeLi
 }
 
 // package all the arguments that match a ... T parameter into a []T.
-func mkdotargslice(lr0 *NodeList, nn *NodeList, l *Type, fp int, init **NodeList, ddd *Node) *NodeList {
+func mkdotargslice(lr0 nodesOrNodeList, nn *NodeList, l *Type, fp int, init **NodeList, ddd *Node) *NodeList {
 	esc := uint16(EscUnknown)
 	if ddd != nil {
 		esc = ddd.Esc
@@ -1728,7 +1728,7 @@ func mkdotargslice(lr0 *NodeList, nn *NodeList, l *Type, fp int, init **NodeList
 	tslice.Bound = -1
 
 	var n *Node
-	if count(lr0) == 0 {
+	if nodeSeqLen(lr0) == 0 {
 		n = nodnil()
 		n.Type = tslice
 	} else {
@@ -1736,7 +1736,7 @@ func mkdotargslice(lr0 *NodeList, nn *NodeList, l *Type, fp int, init **NodeList
 		if ddd != nil && prealloc[ddd] != nil {
 			prealloc[n] = prealloc[ddd] // temporary to use
 		}
-		n.List = lr0
+		setNodeSeq(&n.List, lr0)
 		n.Esc = esc
 		typecheck(&n, Erv)
 		if n.Type == nil {
@@ -1772,14 +1772,14 @@ func dumptypes(nl **Type, what string) string {
 	return fmt_
 }
 
-func dumpnodetypes(l *NodeList, what string) string {
+func dumpnodetypes(l nodesOrNodeList, what string) string {
 	var r *Node
 
 	fmt_ := ""
 	fmt_ += "\t"
 	first := 1
-	for ; l != nil; l = l.Next {
-		r = l.N
+	for it := nodeSeqIterate(l); !it.Done(); it.Next() {
+		r = it.N()
 		if first != 0 {
 			first = 0
 		} else {
@@ -1798,14 +1798,14 @@ func dumpnodetypes(l *NodeList, what string) string {
 // a type list. called in
 //	return expr-list
 //	func(expr-list)
-func ascompatte(op Op, call *Node, isddd bool, nl **Type, lr *NodeList, fp int, init **NodeList) *NodeList {
+func ascompatte(op Op, call *Node, isddd bool, nl **Type, lr nodesOrNodeList, fp int, init **NodeList) *NodeList {
 	var savel Iter
 
 	lr0 := lr
 	l := Structfirst(&savel, nl)
 	var r *Node
-	if lr != nil {
-		r = lr.N
+	if nodeSeqLen(lr) > 0 {
+		r = nodeSeqFirst(lr)
 	}
 	var nn *NodeList
 
@@ -1814,7 +1814,8 @@ func ascompatte(op Op, call *Node, isddd bool, nl **Type, lr *NodeList, fp int,
 	var l2 string
 	var ll *Type
 	var l1 string
-	if r != nil && lr.Next == nil && r.Type.Etype == TSTRUCT && r.Type.Funarg {
+	var lrit nodeSeqIterator
+	if r != nil && nodeSeqLen(lr) <= 1 && r.Type.Etype == TSTRUCT && r.Type.Funarg {
 		// optimization - can do block copy
 		if eqtypenoname(r.Type, *nl) {
 			a := nodarg(*nl, fp)
@@ -1835,15 +1836,16 @@ func ascompatte(op Op, call *Node, isddd bool, nl **Type, lr *NodeList, fp int,
 
 		a = Nod(OAS2, nil, nil)
 		a.List = alist
-		a.Rlist = lr
+		setNodeSeq(&a.Rlist, lr)
 		typecheck(&a, Etop)
 		walkstmt(&a)
 		*init = list(*init, a)
 		lr = alist
-		r = lr.N
+		r = nodeSeqFirst(lr)
 		l = Structfirst(&savel, nl)
 	}
 
+	lrit = nodeSeqIterate(lr)
 loop:
 	if l != nil && l.Isddd {
 		// the ddd parameter must be last
@@ -1857,7 +1859,7 @@ loop:
 		// only if we are assigning a single ddd
 		// argument to a ddd parameter then it is
 		// passed thru unencapsulated
-		if r != nil && lr.Next == nil && isddd && Eqtype(l.Type, r.Type) {
+		if r != nil && lrit.Len() <= 1 && isddd && Eqtype(l.Type, r.Type) {
 			a = Nod(OAS, nodarg(l, fp), r)
 			a = convas(a, init)
 			nn = list(nn, a)
@@ -1867,7 +1869,7 @@ loop:
 		// normal case -- make a slice of all
 		// remaining arguments and pass it to
 		// the ddd parameter.
-		nn = mkdotargslice(lr, nn, l, fp, init, call.Right)
+		nn = mkdotargslice(lrit.Seq(), nn, l, fp, init, call.Right)
 
 		goto ret
 	}
@@ -1892,15 +1894,15 @@ loop:
 
 	l = structnext(&savel)
 	r = nil
-	lr = lr.Next
-	if lr != nil {
-		r = lr.N
+	lrit.Next()
+	if !lrit.Done() {
+		r = lrit.N()
 	}
 	goto loop
 
 ret:
-	for lr = nn; lr != nil; lr = lr.Next {
-		lr.N.Typecheck = 1
+	for lrit = nodeSeqIterate(nn); !lrit.Done(); lrit.Next() {
+		lrit.N().Typecheck = 1
 	}
 	return nn
 }