cmd/compile: break out constants for local and global dictionary prefixes

Create constant LocalDictName for the pname/refix for dictionary
parameters or local variables, and constant GlobalDictPrefix for the
prefix for names of global dictionaries. I wanted to make sure these
constants were set up as we add more reference to dictionaries for
debugging, etc.

Change-Id: Ide801f842383300a2699c96943ec06decaecc358
Reviewed-on: https://go-review.googlesource.com/c/go/+/351450
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

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

@@ -401,10 +401,7 @@ func (g *irgen) buildClosure(outer *ir.Func, x ir.Node) ir.Node {
 	var dictVar *ir.Name
 	var dictAssign *ir.AssignStmt
 	if outer != nil {
-		// Note: for now this is a compile-time constant, so we don't really need a closure
-		// to capture it (a wrapper function would work just as well). But eventually it
-		// will be a read of a subdictionary from the parent dictionary.
-		dictVar = ir.NewNameAt(pos, typecheck.LookupNum(".dict", g.dnum))
+		dictVar = ir.NewNameAt(pos, typecheck.LookupNum(typecheck.LocalDictName, g.dnum))
 		g.dnum++
 		dictVar.Class = ir.PAUTO
 		typed(types.Types[types.TUINTPTR], dictVar)
@@ -723,7 +720,7 @@ func (g *irgen) genericSubst(newsym *types.Sym, nameNode *ir.Name, shapes []*typ
 	newf.Dcl = make([]*ir.Name, 0, len(gf.Dcl)+1)
 
 	// Create the needed dictionary param
-	dictionarySym := newsym.Pkg.Lookup(".dict")
+	dictionarySym := newsym.Pkg.Lookup(typecheck.LocalDictName)
 	dictionaryType := types.Types[types.TUINTPTR]
 	dictionaryName := ir.NewNameAt(gf.Pos(), dictionarySym)
 	typed(dictionaryType, dictionaryName)
@@ -731,7 +728,7 @@ func (g *irgen) genericSubst(newsym *types.Sym, nameNode *ir.Name, shapes []*typ
 	dictionaryName.Curfn = newf
 	newf.Dcl = append(newf.Dcl, dictionaryName)
 	for _, n := range gf.Dcl {
-		if n.Sym().Name == ".dict" {
+		if n.Sym().Name == typecheck.LocalDictName {
 			panic("already has dictionary")
 		}
 		newf.Dcl = append(newf.Dcl, subst.localvar(n))
@@ -1127,7 +1124,7 @@ func (subst *subster) node(n ir.Node) ir.Node {
 			// Copy that closure variable to a local one.
 			// Note: this allows the dictionary to be captured by child closures.
 			// See issue 47723.
-			ldict := ir.NewNameAt(x.Pos(), newfn.Sym().Pkg.Lookup(".dict"))
+			ldict := ir.NewNameAt(x.Pos(), newfn.Sym().Pkg.Lookup(typecheck.LocalDictName))
 			typed(types.Types[types.TUINTPTR], ldict)
 			ldict.Class = ir.PAUTO
 			ldict.Curfn = newfn

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

@@ -2196,7 +2196,7 @@ func (w *exportWriter) localIdent(s *types.Sym) {
 		return
 	}
 
-	if i := strings.LastIndex(name, "."); i >= 0 && !strings.HasPrefix(name, ".dict") { // TODO: just use autotmp names for dictionaries?
+	if i := strings.LastIndex(name, "."); i >= 0 && !strings.HasPrefix(name, LocalDictName) {
 		base.Fatalf("unexpected dot in identifier: %v", name)
 	}
 
@@ -2232,3 +2232,6 @@ func (w *intWriter) uint64(x uint64) {
 // information (e.g. length field for OSLICELIT).
 const go117ExportTypes = true
 const Go117ExportTypes = go117ExportTypes
+
+// The name used for dictionary parameters or local variables.
+const LocalDictName = ".dict"

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

@@ -14,6 +14,7 @@ import (
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/ir"
 	"cmd/compile/internal/types"
+	"cmd/internal/objabi"
 	"cmd/internal/src"
 )
 
@@ -987,7 +988,7 @@ func MakeDictSym(gf *types.Sym, targs []*types.Type, hasBrackets bool) *types.Sy
 		}
 	}
 	name := makeInstName1(gf.Name, targs, hasBrackets)
-	name = ".dict." + name
+	name = fmt.Sprintf("%s.%s", objabi.GlobalDictPrefix, name)
 	return gf.Pkg.Lookup(name)
 }
 

src/cmd/internal/obj/objfile.go

@@ -340,7 +340,7 @@ func (w *writer) Sym(s *LSym) {
 	if strings.HasPrefix(s.Name, "go.itab.") && s.Type == objabi.SRODATA {
 		flag2 |= goobj.SymFlagItab
 	}
-	if strings.HasPrefix(s.Name, w.ctxt.Pkgpath) && strings.HasPrefix(s.Name[len(w.ctxt.Pkgpath):], "..dict") {
+	if strings.HasPrefix(s.Name, w.ctxt.Pkgpath) && strings.HasPrefix(s.Name[len(w.ctxt.Pkgpath):], ".") && strings.HasPrefix(s.Name[len(w.ctxt.Pkgpath)+1:], objabi.GlobalDictPrefix) {
 		flag2 |= goobj.SymFlagDict
 	}
 	name := s.Name

src/cmd/internal/objabi/util.go

@@ -13,7 +13,8 @@ import (
 
 const (
 	ElfRelocOffset   = 256
-	MachoRelocOffset = 2048 // reserve enough space for ELF relocations
+	MachoRelocOffset = 2048    // reserve enough space for ELF relocations
+	GlobalDictPrefix = ".dict" // prefix for names of global dictionaries
 )
 
 // HeaderString returns the toolchain configuration string written in