cmd/compile: move auto label gen variables to local function

This still depends on Curfn, but it's progress.

Updates #15756

Change-Id: Ic32fe56f44fcfbc023e7668d4dee07f8b47bf3a4
Reviewed-on: https://go-review.googlesource.com/26661
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -766,7 +766,9 @@ func mkinlcall1(n *Node, fn *Node, isddd bool) *Node {
 		ninit.Append(as)
 	}
 
-	retlabel := newlabel_inl()
+	retlabel := autolabel("i")
+	retlabel.Etype = 1 // flag 'safe' for escape analysis (no backjumps)
+
 	inlgen++
 
 	subst := inlsubst{
@@ -876,15 +878,6 @@ func argvar(t *Type, i int) *Node {
 	return n
 }
 
-var newlabel_inl_label int
-
-func newlabel_inl() *Node {
-	newlabel_inl_label++
-	n := newname(LookupN(".inlret", newlabel_inl_label))
-	n.Etype = 1 // flag 'safe' for escape analysis (no backjumps)
-	return n
-}
-
 // The inlsubst type implements the actual inlining of a single
 // function call.
 type inlsubst struct {

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

@@ -23,7 +23,7 @@ func TestSizeof(t *testing.T) {
 		_64bit uintptr     // size on 64bit platforms
 	}{
 		{Flow{}, 52, 88},
-		{Func{}, 92, 160},
+		{Func{}, 96, 168},
 		{Name{}, 52, 80},
 		{Node{}, 92, 144},
 		{Sym{}, 60, 112},

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

@@ -246,6 +246,20 @@ func LookupN(prefix string, n int) *Sym {
 	return LookupBytes(b)
 }
 
+// autolabel generates a new Name node for use with
+// an automatically generated label.
+// prefix is a short mnemonic (e.g. "s" for switch)
+// to help with debugging.
+func autolabel(prefix string) *Node {
+	fn := Curfn
+	if Curfn == nil {
+		Fatalf("autolabel outside function")
+	}
+	n := fn.Func.Label
+	fn.Func.Label++
+	return newname(LookupN("."+prefix, int(n)))
+}
+
 var initSyms []*Sym
 
 var nopkg = &Pkg{

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

@@ -4,10 +4,7 @@
 
 package gc
 
-import (
-	"sort"
-	"strconv"
-)
+import "sort"
 
 const (
 	// expression switch
@@ -361,7 +358,7 @@ func casebody(sw *Node, typeswvar *Node) {
 		n.Op = OCASE
 		needvar := n.List.Len() != 1 || n.List.First().Op == OLITERAL
 
-		jmp := Nod(OGOTO, newCaseLabel(), nil)
+		jmp := Nod(OGOTO, autolabel("s"), nil)
 		if n.List.Len() == 0 {
 			if def != nil {
 				Yyerror("more than one default case")
@@ -424,16 +421,6 @@ func casebody(sw *Node, typeswvar *Node) {
 	lineno = lno
 }
 
-// nSwitchLabel is the number of switch labels generated.
-// This should be per-function, but it is a global counter for now.
-var nSwitchLabel int
-
-func newCaseLabel() *Node {
-	label := strconv.Itoa(nSwitchLabel)
-	nSwitchLabel++
-	return newname(Lookup(label))
-}
-
 // caseClauses generates a slice of caseClauses
 // corresponding to the clauses in the switch statement sw.
 // Kind is the kind of switch statement.
@@ -590,7 +577,7 @@ func (s *typeSwitch) walk(sw *Node) {
 		i.Nbody.Set1(typenil)
 	} else {
 		// Jump to default case.
-		lbl := newCaseLabel()
+		lbl := autolabel("s")
 		i.Nbody.Set1(Nod(OGOTO, lbl, nil))
 		// Wrap default case with label.
 		blk := Nod(OBLOCK, nil, nil)

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

@@ -290,6 +290,8 @@ type Func struct {
 	InlCost int32
 	Depth   int32
 
+	Label int32 // largest auto-generated label in this function
+
 	Endlineno int32
 	WBLineno  int32 // line number of first write barrier