cmd/6g, cmd/internal/gc: use Etype instead of Ostk

Change-Id: Ifda5d84b28717986c93b63767298180a6d6236c0
Reviewed-on: https://go-review.googlesource.com/10140Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/6g/ggen.go

@@ -306,7 +306,7 @@ func dodiv(op int, nl *gc.Node, nr *gc.Node, res *gc.Node) {
  * known to be dead.
  */
 func savex(dr int, x *gc.Node, oldx *gc.Node, res *gc.Node, t *gc.Type) {
-	r := int(reg[dr])
+	r := reg[dr]
 
 	// save current ax and dx if they are live
 	// and not the destination
@@ -318,7 +318,7 @@ func savex(dr int, x *gc.Node, oldx *gc.Node, res *gc.Node, t *gc.Type) {
 		x.Type = gc.Types[gc.TINT64]
 		gmove(x, oldx)
 		x.Type = t
-		oldx.Ostk = int32(r) // squirrel away old r value
+		oldx.Etype = r // squirrel away old r value
 		reg[dr] = 1
 	}
 }
@@ -326,7 +326,7 @@ func savex(dr int, x *gc.Node, oldx *gc.Node, res *gc.Node, t *gc.Type) {
 func restx(x *gc.Node, oldx *gc.Node) {
 	if oldx.Op != 0 {
 		x.Type = gc.Types[gc.TINT64]
-		reg[x.Reg] = uint8(oldx.Ostk)
+		reg[x.Reg] = oldx.Etype
 		gmove(oldx, x)
 		gc.Regfree(oldx)
 	}

src/cmd/internal/gc/syntax.go

@@ -27,7 +27,7 @@ type Node struct {
 	Nointerface bool
 	Ullman      uint8 // sethi/ullman number
 	Addable     bool  // addressable
-	Etype       uint8 // op for OASOP, etype for OTYPE, exclam for export
+	Etype       uint8 // op for OASOP, etype for OTYPE, exclam for export, 6g saved reg
 	Bounded     bool  // bounds check unnecessary
 	Class       uint8 // PPARAM, PAUTO, PEXTERN, etc
 	Embedded    uint8 // ODCLFIELD embedded type
@@ -97,7 +97,6 @@ type Node struct {
 	Lineno   int32
 	Xoffset  int64
 	Stkdelta int64 // offset added by stack frame compaction phase.
-	Ostk     int32 // 6g only
 	Iota     int32
 	Walkgen  uint32
 	Esclevel Level