cmd/compile: eliminate iota_

Change-Id: Iad9c1961aedcc754ad2f6010a49f94c5a0a4bfee
Reviewed-on: https://go-review.googlesource.com/32487
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

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

@@ -288,7 +288,7 @@ func variter(vl []*Node, t *Node, el []*Node) []*Node {
 
 // declare constants from grammar
 // new_name_list [[type] = expr_list]
-func constiter(vl []*Node, t *Node, cl []*Node) []*Node {
+func constiter(vl []*Node, t *Node, cl []*Node, iotaVal int64) []*Node {
 	var lno src.XPos // default is to leave line number alone in listtreecopy
 	if len(cl) == 0 {
 		if t != nil {
@@ -301,31 +301,29 @@ func constiter(vl []*Node, t *Node, cl []*Node) []*Node {
 		lastconst = cl
 		lasttype = t
 	}
-	clcopy := listtreecopy(cl, lno)
 
 	var vv []*Node
-	for _, v := range vl {
-		if len(clcopy) == 0 {
+	for i, v := range vl {
+		if i >= len(cl) {
 			yyerror("missing value in const declaration")
 			break
 		}
 
-		c := clcopy[0]
-		clcopy = clcopy[1:]
+		c := treecopy(cl[i], lno)
 
 		v.Op = OLITERAL
 		declare(v, dclcontext)
 
 		v.Name.Param.Ntype = t
 		v.Name.Defn = c
+		v.SetIota(iotaVal)
 
 		vv = append(vv, nod(ODCLCONST, v, nil))
 	}
 
-	if len(clcopy) != 0 {
+	if len(cl) > len(vl) {
 		yyerror("extra expression in const declaration")
 	}
-	iota_ += 1
 	return vv
 }
 
@@ -401,9 +399,7 @@ func oldname(s *Sym) *Node {
 		// Maybe a top-level declaration will come along later to
 		// define s. resolve will check s.Def again once all input
 		// source has been processed.
-		n = newnoname(s)
-		n.SetIota(iota_) // save current iota value in const declarations
-		return n
+		return newnoname(s)
 	}
 
 	if Curfn != nil && n.Op == ONAME && n.Name.Funcdepth > 0 && n.Name.Funcdepth != funcdepth {

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

@@ -223,8 +223,6 @@ var dclcontext Class // PEXTERN/PAUTO
 
 var statuniqgen int // name generator for static temps
 
-var iota_ int64
-
 var lastconst []*Node
 
 var lasttype *Node

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

@@ -679,7 +679,6 @@ func findpkg(name string) (file string, ok bool) {
 // but does not make them visible to user code.
 func loadsys() {
 	block = 1
-	iota_ = -1000000
 
 	importpkg = Runtimepkg
 	typecheckok = true

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

@@ -85,7 +85,6 @@ type linkname struct {
 
 func (p *noder) node() {
 	block = 1
-	iota_ = -1000000
 	imported_unsafe = false
 
 	p.lineno(p.file.PkgName)
@@ -134,22 +133,18 @@ func (p *noder) decls(decls []syntax.Decl) (l []*Node) {
 		case *syntax.ConstDecl:
 			// Tricky to handle golang.org/issue/15550 correctly.
 
-			prevIota := iota_
-
 			if decl.Group == nil || decl.Group != lastConstGroup {
 				iotaVal = 0
 				lastConstRHS = nil
 			}
 
-			iota_ = iotaVal
 			lastconst = lastConstRHS
 
-			l = append(l, p.constDecl(decl)...)
+			l = append(l, p.constDecl(decl, iotaVal)...)
 
 			lastConstRHS = lastconst
 			lastconst = nil
 
-			iota_ = prevIota
 			iotaVal++
 
 			lastConstGroup = decl.Group
@@ -227,7 +222,7 @@ func (p *noder) varDecl(decl *syntax.VarDecl) []*Node {
 	return variter(names, typ, exprs)
 }
 
-func (p *noder) constDecl(decl *syntax.ConstDecl) []*Node {
+func (p *noder) constDecl(decl *syntax.ConstDecl, iotaVal int64) []*Node {
 	names := p.declNames(decl.NameList)
 	typ := p.typeExprOrNil(decl.Type)
 
@@ -236,7 +231,7 @@ func (p *noder) constDecl(decl *syntax.ConstDecl) []*Node {
 		exprs = p.exprList(decl.Values)
 	}
 
-	return constiter(names, typ, exprs)
+	return constiter(names, typ, exprs, iotaVal)
 }
 
 func (p *noder) typeDecl(decl *syntax.TypeDecl) *Node {

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

@@ -476,28 +476,13 @@ func treecopy(n *Node, pos src.XPos) *Node {
 		}
 		return &m
 
-	case ONONAME:
-		if n.Sym == lookup("iota") {
-			// Not sure yet whether this is the real iota,
-			// but make a copy of the Node* just in case,
-			// so that all the copies of this const definition
-			// don't have the same iota value.
-			m := *n
-			if pos.IsKnown() {
-				m.Pos = pos
-			}
-			m.SetIota(iota_)
-			return &m
-		}
-		return n
-
 	case OPACK:
 		// OPACK nodes are never valid in const value declarations,
 		// but allow them like any other declared symbol to avoid
 		// crashing (golang.org/issue/11361).
 		fallthrough
 
-	case ONAME, OLITERAL, OTYPE:
+	case ONAME, ONONAME, OLITERAL, OTYPE:
 		return n
 
 	}

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

@@ -43,7 +43,7 @@ type Node struct {
 	// - ODOT, ODOTPTR, and OINDREGSP use it to indicate offset relative to their base address.
 	// - OSTRUCTKEY uses it to store the named field's offset.
 	// - OXCASE and OXFALL use it to validate the use of fallthrough.
-	// - ONONAME uses it to store the current value of iota, see Node.Iota
+	// - Named OLITERALs use it to to store their ambient iota value.
 	// Possibly still more uses. If you find any, document them.
 	Xoffset int64
 

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

@@ -36,8 +36,11 @@ func resolve(n *Node) *Node {
 		if r != nil {
 			if r.Op != OIOTA {
 				n = r
-			} else if n.Iota() >= 0 {
-				n = nodintconst(n.Iota())
+			} else if len(typecheckdefstack) > 0 {
+				x := typecheckdefstack[len(typecheckdefstack)-1]
+				if x.Op == OLITERAL {
+					n = nodintconst(x.Iota())
+				}
 			}
 		}
 	}