[dev.regabi] cmd/compile: add ir.PkgName

OPACK was using a whole Node and Name and Param
to hold about three fields. Give it its own implementation.

Passes buildall w/ toolstash -cmp.

Change-Id: I85a28b43d37183b2062d337b0b1b2eea52884e8c
Reviewed-on: https://go-review.googlesource.com/c/go/+/274093
Trust: Russ Cox <rsc@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

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

@@ -955,8 +955,9 @@ func clearImports() {
 			// leave s->block set to cause redeclaration
 			// errors if a conflicting top-level name is
 			// introduced by a different file.
-			if !n.Name().Used() && base.SyntaxErrors() == 0 {
-				unused = append(unused, importedPkg{n.Pos(), n.Name().Pkg.Path, s.Name})
+			p := n.(*ir.PkgName)
+			if !p.Used && base.SyntaxErrors() == 0 {
+				unused = append(unused, importedPkg{p.Pos(), p.Pkg.Path, s.Name})
 			}
 			s.Def = nil
 			continue
@@ -964,9 +965,9 @@ func clearImports() {
 		if IsAlias(s) {
 			// throw away top-level name left over
 			// from previous import . "x"
-			if n.Name() != nil && n.Name().Pack != nil && !n.Name().Pack.Name().Used() && base.SyntaxErrors() == 0 {
-				unused = append(unused, importedPkg{n.Name().Pack.Pos(), n.Name().Pack.Name().Pkg.Path, ""})
-				n.Name().Pack.Name().SetUsed(true)
+			if name := n.Name(); name != nil && name.PkgName != nil && !name.PkgName.Used && base.SyntaxErrors() == 0 {
+				unused = append(unused, importedPkg{name.PkgName.Pos(), name.PkgName.Pkg.Path, ""})
+				name.PkgName.Used = true
 			}
 			s.Def = nil
 			continue

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

@@ -356,9 +356,7 @@ func (p *noder) importDecl(imp *syntax.ImportDecl) {
 		my = lookup(ipkg.Name)
 	}
 
-	pack := p.nod(imp, ir.OPACK, nil, nil)
-	pack.SetSym(my)
-	pack.Name().Pkg = ipkg
+	pack := ir.NewPkgName(p.pos(imp), my, ipkg)
 
 	switch my.Name {
 	case ".":
@@ -685,8 +683,9 @@ func (p *noder) expr(expr syntax.Expr) ir.Node {
 		// parser.new_dotname
 		obj := p.expr(expr.X)
 		if obj.Op() == ir.OPACK {
-			obj.Name().SetUsed(true)
-			return importName(obj.Name().Pkg.Lookup(expr.Sel.Value))
+			pack := obj.(*ir.PkgName)
+			pack.Used = true
+			return importName(pack.Pkg.Lookup(expr.Sel.Value))
 		}
 		n := nodSym(ir.OXDOT, obj, p.name(expr.Sel))
 		n.SetPos(p.pos(expr)) // lineno may have been changed by p.expr(expr.X)
@@ -910,8 +909,8 @@ func (p *noder) packname(expr syntax.Expr) *types.Sym {
 	switch expr := expr.(type) {
 	case *syntax.Name:
 		name := p.name(expr)
-		if n := oldname(name); n.Name() != nil && n.Name().Pack != nil {
-			n.Name().Pack.Name().SetUsed(true)
+		if n := oldname(name); n.Name() != nil && n.Name().PkgName != nil {
+			n.Name().PkgName.Used = true
 		}
 		return name
 	case *syntax.SelectorExpr:
@@ -926,8 +925,9 @@ func (p *noder) packname(expr syntax.Expr) *types.Sym {
 			base.Errorf("%v is not a package", name)
 			pkg = ir.LocalPkg
 		} else {
-			def.Name().SetUsed(true)
-			pkg = def.Name().Pkg
+			def := def.(*ir.PkgName)
+			def.Used = true
+			pkg = def.Pkg
 		}
 		return pkg.Lookup(expr.Sel.Value)
 	}
@@ -1675,8 +1675,8 @@ func safeArg(name string) bool {
 
 func mkname(sym *types.Sym) ir.Node {
 	n := oldname(sym)
-	if n.Name() != nil && n.Name().Pack != nil {
-		n.Name().Pack.Name().SetUsed(true)
+	if n.Name() != nil && n.Name().PkgName != nil {
+		n.Name().PkgName.Used = true
 	}
 	return n
 }

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

@@ -102,7 +102,7 @@ func autolabel(prefix string) *types.Sym {
 
 // find all the exported symbols in package opkg
 // and make them available in the current package
-func importdot(opkg *types.Pkg, pack ir.Node) {
+func importdot(opkg *types.Pkg, pack *ir.PkgName) {
 	n := 0
 	for _, s := range opkg.Syms {
 		if s.Def == nil {
@@ -124,7 +124,7 @@ func importdot(opkg *types.Pkg, pack ir.Node) {
 			ir.Dump("s1def", ir.AsNode(s1.Def))
 			base.Fatalf("missing Name")
 		}
-		ir.AsNode(s1.Def).Name().Pack = pack
+		ir.AsNode(s1.Def).Name().PkgName = pack
 		s1.Origpkg = opkg
 		n++
 	}

src/cmd/compile/internal/ir/name.go

@@ -9,13 +9,13 @@ import (
 	"cmd/compile/internal/types"
 	"cmd/internal/objabi"
 	"cmd/internal/src"
+	"fmt"
 	"go/constant"
 )
 
-// Name holds Node fields used only by named nodes (ONAME, OTYPE, OPACK, OLABEL, some OLITERAL).
+// Name holds Node fields used only by named nodes (ONAME, OTYPE, some OLITERAL).
 type Name struct {
-	Pack Node       // real package for import . names
-	Pkg  *types.Pkg // pkg for OPACK nodes
+	PkgName *PkgName // real package for import . names
 	// For a local variable (not param) or extern, the initializing assignment (OAS or OAS2).
 	// For a closure var, the ONAME node of the outer captured variable
 	Defn Node
@@ -374,3 +374,23 @@ const (
 	// Careful: Class is stored in three bits in Node.flags.
 	_ = uint((1 << 3) - iota) // static assert for iota <= (1 << 3)
 )
+
+// A Pack is an identifier referring to an imported package.
+type PkgName struct {
+	miniNode
+	sym  *types.Sym
+	Pkg  *types.Pkg
+	Used bool
+}
+
+func (p *PkgName) String() string                { return fmt.Sprint(p) }
+func (p *PkgName) Format(s fmt.State, verb rune) { FmtNode(p, s, verb) }
+func (p *PkgName) RawCopy() Node                 { c := *p; return &c }
+func (p *PkgName) Sym() *types.Sym               { return p.sym }
+
+func NewPkgName(pos src.XPos, sym *types.Sym, pkg *types.Pkg) *PkgName {
+	p := &PkgName{sym: sym, Pkg: pkg}
+	p.op = OPACK
+	p.pos = pos
+	return p
+}

src/cmd/compile/internal/ir/node.go

@@ -1339,12 +1339,7 @@ func NodAt(pos src.XPos, op Op, nleft, nright Node) Node {
 		n.SetFunc(&x.f)
 		n.Func().Decl = n
 	case OPACK:
-		var x struct {
-			n node
-			m Name
-		}
-		n = &x.n
-		n.SetName(&x.m)
+		return NewPkgName(pos, nil, nil)
 	case OEMPTY:
 		return NewEmptyStmt(pos)
 	case OBREAK, OCONTINUE, OFALL, OGOTO:
@@ -1462,7 +1457,6 @@ var okForNod = [OEND]bool{
 	OOFFSETOF:      true,
 	OOR:            true,
 	OOROR:          true,
-	OPACK:          true,
 	OPANIC:         true,
 	OPAREN:         true,
 	OPLUS:          true,

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

@@ -21,7 +21,7 @@ func TestSizeof(t *testing.T) {
 		_64bit uintptr     // size on 64bit platforms
 	}{
 		{Func{}, 152, 280},
-		{Name{}, 44, 80},
+		{Name{}, 36, 64},
 		{Param{}, 44, 88},
 		{node{}, 88, 152},
 	}