cmd/compile: remove OCASE and rename OXCASE to OCASE

We used to use OXCASE to represent general, possibly multi-valued
cases, and then desugar these during walk into single-value cases
represented by OCASE.

In CL 194660, we switched to eliminated the desugaring step and
instead handle the multi-valued cases directly, which eliminates the
need for an OCASE Op. Instead, we can simply remove OCASE, and rename
OXCASE to just OCASE.

Passes toolstash-check.

Change-Id: I3cc184340f9081d37453927cca1c059267fdbc12
Reviewed-on: https://go-review.googlesource.com/c/go/+/196117
Reviewed-by: Keith Randall <khr@golang.org>

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

@@ -1035,7 +1035,7 @@ func (n *Node) stmtfmt(s fmt.State, mode fmtMode) {
 
 		mode.Fprintf(s, " { %v }", n.List)
 
-	case OXCASE:
+	case OCASE:
 		if n.List.Len() != 0 {
 			mode.Fprintf(s, "case %.v", n.List)
 		} else {
@@ -1043,22 +1043,6 @@ func (n *Node) stmtfmt(s fmt.State, mode fmtMode) {
 		}
 		mode.Fprintf(s, ": %v", n.Nbody)
 
-	case OCASE:
-		switch {
-		case n.Left != nil:
-			// single element
-			mode.Fprintf(s, "case %v", n.Left)
-		case n.List.Len() > 0:
-			// range
-			if n.List.Len() != 2 {
-				Fatalf("bad OCASE list length %d", n.List.Len())
-			}
-			mode.Fprintf(s, "case %v..%v", n.List.First(), n.List.Second())
-		default:
-			fmt.Fprint(s, "default")
-		}
-		mode.Fprintf(s, ": %v", n.Nbody)
-
 	case OBREAK, OCONTINUE, OGOTO, OFALL:
 		if n.Sym != nil {
 			mode.Fprintf(s, "%#v %v", n.Op, n.Sym)
@@ -1192,7 +1176,6 @@ var opprec = []int{
 	ORETURN:     -1,
 	OSELECT:     -1,
 	OSWITCH:     -1,
-	OXCASE:      -1,
 
 	OEND: 0,
 }

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

@@ -1079,8 +1079,8 @@ func (w *exportWriter) stmt(n *Node) {
 		w.exprsOrNil(n.Left, nil)
 		w.stmtList(n.List)
 
-	case OCASE, OXCASE:
+	case OCASE:
-		w.op(OXCASE)
+		w.op(OCASE)
 		w.pos(n.Pos)
 		w.stmtList(n.List)
 		w.stmtList(n.Nbody)

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

@@ -1003,20 +1003,14 @@ func (r *importReader) node() *Node {
 		n.List.Set(r.stmtList())
 		return n
 
-	// case OCASE, OXCASE:
+	case OCASE:
-	// 	unreachable - mapped to OXCASE case below by exporter
+		n := nodl(r.pos(), OCASE, nil, nil)
-
-	case OXCASE:
-		n := nodl(r.pos(), OXCASE, nil, nil)
 		n.List.Set(r.exprList())
 		// TODO(gri) eventually we must declare variables for type switch
 		// statements (type switch statements are not yet exported)
 		n.Nbody.Set(r.stmtList())
 		return n
 
-	// case OFALL:
-	// 	unreachable - mapped to OXFALL case below by exporter
-
 	case OFALL:
 		n := nodl(r.pos(), OFALL, nil, nil)
 		return n

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

@@ -1188,7 +1188,7 @@ func (p *noder) caseClauses(clauses []*syntax.CaseClause, tswitch *Node, rbrace
 		}
 		p.openScope(clause.Pos())
 
-		n := p.nod(clause, OXCASE, nil, nil)
+		n := p.nod(clause, OCASE, nil, nil)
 		if clause.Cases != nil {
 			n.List.Set(p.exprList(clause.Cases))
 		}
@@ -1244,7 +1244,7 @@ func (p *noder) commClauses(clauses []*syntax.CommClause, rbrace syntax.Pos) []*
 		}
 		p.openScope(clause.Pos())
 
-		n := p.nod(clause, OXCASE, nil, nil)
+		n := p.nod(clause, OCASE, nil, nil)
 		if clause.Comm != nil {
 			n.List.Set1(p.stmt(clause.Comm))
 		}

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

@@ -1,4 +1,4 @@
-// Code generated by "stringer -type=Op -trimprefix=O"; DO NOT EDIT.
+// Code generated by "stringer -type Op -trimprefix O"; DO NOT EDIT.
 
 package gc
 
@@ -121,8 +121,7 @@ func _() {
 	_ = x[OSIZEOF-110]
 	_ = x[OBLOCK-111]
 	_ = x[OBREAK-112]
-	_ = x[OCASE-113]
+	_ = x[OCASE-114]
-	_ = x[OXCASE-114]
 	_ = x[OCONTINUE-115]
 	_ = x[ODEFER-116]
 	_ = x[OEMPTY-117]
@@ -164,13 +163,24 @@ func _() {
 	_ = x[OEND-153]
 }
 
-const _Op_name = "XXXNAMENONAMETYPEPACKLITERALADDSUBORXORADDSTRADDRANDANDAPPENDBYTES2STRBYTES2STRTMPRUNES2STRSTR2BYTESSTR2BYTESTMPSTR2RUNESASAS2AS2DOTTYPEAS2FUNCAS2MAPRAS2RECVASOPCALLCALLFUNCCALLMETHCALLINTERCALLPARTCAPCLOSECLOSURECOMPLITMAPLITSTRUCTLITARRAYLITSLICELITPTRLITCONVCONVIFACECONVNOPCOPYDCLDCLFUNCDCLFIELDDCLCONSTDCLTYPEDELETEDOTDOTPTRDOTMETHDOTINTERXDOTDOTTYPEDOTTYPE2EQNELTLEGEGTDEREFINDEXINDEXMAPKEYSTRUCTKEYLENMAKEMAKECHANMAKEMAPMAKESLICEMULDIVMODLSHRSHANDANDNOTNEWNEWOBJNOTBITNOTPLUSNEGORORPANICPRINTPRINTNPARENSENDSLICESLICEARRSLICESTRSLICE3SLICE3ARRSLICEHEADERRECOVERRECVRUNESTRSELRECVSELRECV2IOTAREALIMAGCOMPLEXALIGNOFOFFSETOFSIZEOFBLOCKBREAKCASEXCASECONTINUEDEFEREMPTYFALLFORFORUNTILGOTOIFLABELGORANGERETURNSELECTSWITCHTYPESWTCHANTMAPTSTRUCTTINTERTFUNCTARRAYDDDDDDARGINLCALLEFACEITABIDATASPTRCLOSUREVARCFUNCCHECKNILVARDEFVARKILLVARLIVERESULTINLMARKRETJMPGETGEND"
+const (
+	_Op_name_0 = "XXXNAMENONAMETYPEPACKLITERALADDSUBORXORADDSTRADDRANDANDAPPENDBYTES2STRBYTES2STRTMPRUNES2STRSTR2BYTESSTR2BYTESTMPSTR2RUNESASAS2AS2DOTTYPEAS2FUNCAS2MAPRAS2RECVASOPCALLCALLFUNCCALLMETHCALLINTERCALLPARTCAPCLOSECLOSURECOMPLITMAPLITSTRUCTLITARRAYLITSLICELITPTRLITCONVCONVIFACECONVNOPCOPYDCLDCLFUNCDCLFIELDDCLCONSTDCLTYPEDELETEDOTDOTPTRDOTMETHDOTINTERXDOTDOTTYPEDOTTYPE2EQNELTLEGEGTDEREFINDEXINDEXMAPKEYSTRUCTKEYLENMAKEMAKECHANMAKEMAPMAKESLICEMULDIVMODLSHRSHANDANDNOTNEWNEWOBJNOTBITNOTPLUSNEGORORPANICPRINTPRINTNPARENSENDSLICESLICEARRSLICESTRSLICE3SLICE3ARRSLICEHEADERRECOVERRECVRUNESTRSELRECVSELRECV2IOTAREALIMAGCOMPLEXALIGNOFOFFSETOFSIZEOFBLOCKBREAK"
+	_Op_name_1 = "CASECONTINUEDEFEREMPTYFALLFORFORUNTILGOTOIFLABELGORANGERETURNSELECTSWITCHTYPESWTCHANTMAPTSTRUCTTINTERTFUNCTARRAYDDDDDDARGINLCALLEFACEITABIDATASPTRCLOSUREVARCFUNCCHECKNILVARDEFVARKILLVARLIVERESULTINLMARKRETJMPGETGEND"
+)
 
-var _Op_index = [...]uint16{0, 3, 7, 13, 17, 21, 28, 31, 34, 36, 39, 45, 49, 55, 61, 70, 82, 91, 100, 112, 121, 123, 126, 136, 143, 150, 157, 161, 165, 173, 181, 190, 198, 201, 206, 213, 220, 226, 235, 243, 251, 257, 261, 270, 277, 281, 284, 291, 299, 307, 314, 320, 323, 329, 336, 344, 348, 355, 363, 365, 367, 369, 371, 373, 375, 380, 385, 393, 396, 405, 408, 412, 420, 427, 436, 439, 442, 445, 448, 451, 454, 460, 463, 469, 472, 478, 482, 485, 489, 494, 499, 505, 510, 514, 519, 527, 535, 541, 550, 561, 568, 572, 579, 586, 594, 598, 602, 606, 613, 620, 628, 634, 639, 644, 648, 653, 661, 666, 671, 675, 678, 686, 690, 692, 697, 699, 704, 710, 716, 722, 728, 733, 737, 744, 750, 755, 761, 764, 770, 777, 782, 786, 791, 795, 805, 810, 818, 824, 831, 838, 844, 851, 857, 861, 864}
+var (
+	_Op_index_0 = [...]uint16{0, 3, 7, 13, 17, 21, 28, 31, 34, 36, 39, 45, 49, 55, 61, 70, 82, 91, 100, 112, 121, 123, 126, 136, 143, 150, 157, 161, 165, 173, 181, 190, 198, 201, 206, 213, 220, 226, 235, 243, 251, 257, 261, 270, 277, 281, 284, 291, 299, 307, 314, 320, 323, 329, 336, 344, 348, 355, 363, 365, 367, 369, 371, 373, 375, 380, 385, 393, 396, 405, 408, 412, 420, 427, 436, 439, 442, 445, 448, 451, 454, 460, 463, 469, 472, 478, 482, 485, 489, 494, 499, 505, 510, 514, 519, 527, 535, 541, 550, 561, 568, 572, 579, 586, 594, 598, 602, 606, 613, 620, 628, 634, 639, 644}
+	_Op_index_1 = [...]uint8{0, 4, 12, 17, 22, 26, 29, 37, 41, 43, 48, 50, 55, 61, 67, 73, 79, 84, 88, 95, 101, 106, 112, 115, 121, 128, 133, 137, 142, 146, 156, 161, 169, 175, 182, 189, 195, 202, 208, 212, 215}
+)
 
 func (i Op) String() string {
-	if i >= Op(len(_Op_index)-1) {
+	switch {
+	case 0 <= i && i <= 112:
+		return _Op_name_0[_Op_index_0[i]:_Op_index_0[i+1]]
+	case 114 <= i && i <= 153:
+		i -= 114
+		return _Op_name_1[_Op_index_1[i]:_Op_index_1[i+1]]
+	default:
 		return "Op(" + strconv.FormatInt(int64(i), 10) + ")"
 	}
-	return _Op_name[_Op_index[i]:_Op_index[i+1]]
 }

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

@@ -779,7 +779,7 @@ func (o *Order) stmt(n *Node) {
 		t := o.markTemp()
 
 		for _, n2 := range n.List.Slice() {
-			if n2.Op != OXCASE {
+			if n2.Op != OCASE {
 				Fatalf("order select case %v", n2.Op)
 			}
 			r := n2.Left
@@ -938,7 +938,7 @@ func (o *Order) stmt(n *Node) {
 		t := o.markTemp()
 		n.Left = o.expr(n.Left, nil)
 		for _, ncas := range n.List.Slice() {
-			if ncas.Op != OXCASE {
+			if ncas.Op != OCASE {
 				Fatalf("order switch case %v", ncas.Op)
 			}
 			o.exprListInPlace(ncas.List)

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

@@ -12,7 +12,7 @@ func typecheckselect(sel *Node) {
 	lno := setlineno(sel)
 	typecheckslice(sel.Ninit.Slice(), ctxStmt)
 	for _, ncase := range sel.List.Slice() {
-		if ncase.Op != OXCASE {
+		if ncase.Op != OCASE {
 			setlineno(ncase)
 			Fatalf("typecheckselect %v", ncase.Op)
 		}

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

@@ -434,7 +434,7 @@ func allCaseExprsAreSideEffectFree(sw *Node) bool {
 	// enough.
 
 	for _, ncase := range sw.List.Slice() {
-		if ncase.Op != OXCASE {
+		if ncase.Op != OCASE {
 			Fatalf("switch string(byteslice) bad op: %v", ncase.Op)
 		}
 		for _, v := range ncase.List.Slice() {

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

@@ -704,8 +704,8 @@ const (
 	// statements
 	OBLOCK    // { List } (block of code)
 	OBREAK    // break [Sym]
-	OCASE     // case Left or List[0]..List[1]: Nbody (select case after processing; Left==nil and List==nil means default)
+	_         // For toolstash -cmp. TODO(mdempsky): Remove.
-	OXCASE    // case List: Nbody (select case before processing; List==nil means default)
+	OCASE     // case List: Nbody (List==nil means default)
 	OCONTINUE // continue [Sym]
 	ODEFER    // defer Left (Left must be call)
 	OEMPTY    // no-op (empty statement)
@@ -727,8 +727,8 @@ const (
 	OGO     // go Left (Left must be call)
 	ORANGE  // for List = range Right { Nbody }
 	ORETURN // return List
-	OSELECT // select { List } (List is list of OXCASE or OCASE)
+	OSELECT // select { List } (List is list of OCASE)
-	OSWITCH // switch Ninit; Left { List } (List is a list of OXCASE or OCASE)
+	OSWITCH // switch Ninit; Left { List } (List is a list of OCASE)
 	OTYPESW // Left = Right.(type) (appears as .Left of OSWITCH)
 
 	// types

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

@@ -2014,7 +2014,7 @@ func typecheck1(n *Node, top int) (res *Node) {
 		n.Type = nil
 		return n
 
-	case OXCASE:
+	case OCASE:
 		ok |= ctxStmt
 		typecheckslice(n.List.Slice(), ctxExpr)
 		typecheckslice(n.Nbody.Slice(), ctxStmt)

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

@@ -209,13 +209,8 @@ func walkstmt(n *Node) *Node {
 	case OBLOCK:
 		walkstmtlist(n.List.Slice())
 
-	case OXCASE:
-		yyerror("case statement out of place")
-		n.Op = OCASE
-		fallthrough
-
 	case OCASE:
-		n.Right = walkstmt(n.Right)
+		yyerror("case statement out of place")
 
 	case ODEFER:
 		Curfn.Func.SetHasDefer(true)