[dev.typeparams] cmd/compile: cleanup unified IR file format a little

This CL makes two changes:

1. It moves object symbols and code tags into a new "relocName"
relocation, which should eventually allow getting rid of objStub.

2. It moves the type parameter data into the relocObjDict relocation,
so everything related to writing out dictionaries is contained there.

Change-Id: If0f7ff7d9384e8664957c3180bf6f20e97bcff6e
Reviewed-on: https://go-review.googlesource.com/c/go/+/336051
Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>

7 files changed, 124 insertions, 116 deletions

diff --git a/src/cmd/compile/internal/noder/linker.go b/src/cmd/compile/internal/noder/linker.go
index eefb5083e5..2bc7f7c608 100644
--- a/src/cmd/compile/internal/noder/linker.go
+++ b/src/cmd/compile/internal/noder/linker.go
@@ -110,7 +110,7 @@ func (l *linker) relocPkg(pr *pkgReader, idx int) int {
 }
 
 func (l *linker) relocObj(pr *pkgReader, idx int) int {
-	path, name, tag, _ := pr.peekObj(idx)
+	path, name, tag := pr.peekObj(idx)
 	sym := types.NewPkg(path, "").Lookup(name)
 
 	if newidx, ok := l.decls[sym]; ok {
@@ -127,7 +127,7 @@ func (l *linker) relocObj(pr *pkgReader, idx int) int {
 		pr = pri.pr
 		idx = pri.idx
 
-		path2, name2, tag2, _ := pr.peekObj(idx)
+		path2, name2, tag2 := pr.peekObj(idx)
 		sym2 := types.NewPkg(path2, "").Lookup(name2)
 		assert(sym == sym2)
 		assert(tag2 != objStub)
@@ -135,13 +135,16 @@ func (l *linker) relocObj(pr *pkgReader, idx int) int {
 
 	w := l.pw.newEncoderRaw(relocObj)
 	wext := l.pw.newEncoderRaw(relocObjExt)
+	wname := l.pw.newEncoderRaw(relocName)
 	wdict := l.pw.newEncoderRaw(relocObjDict)
 
 	l.decls[sym] = w.idx
 	assert(wext.idx == w.idx)
+	assert(wname.idx == w.idx)
 	assert(wdict.idx == w.idx)
 
 	l.relocCommon(pr, &w, relocObj, idx)
+	l.relocCommon(pr, &wname, relocName, idx)
 	l.relocCommon(pr, &wdict, relocObjDict, idx)
 
 	var obj *ir.Name
@@ -279,33 +282,15 @@ func (pr *pkgDecoder) peekPkgPath(idx int) string {
 	return path
 }
 
-func (pr *pkgDecoder) peekObj(idx int) (string, string, codeObj, []int) {
-	r := pr.newDecoder(relocObj, idx, syncObject1)
+func (pr *pkgDecoder) peekObj(idx int) (string, string, codeObj) {
+	r := pr.newDecoder(relocName, idx, syncObject1)
 	r.sync(syncSym)
 	r.sync(syncPkg)
 	path := pr.peekPkgPath(r.reloc(relocPkg))
 	name := r.string()
 	assert(name != "")
 
-	r.sync(syncTypeParamBounds)
-	r.len() // implicits
-	bounds := make([]int, r.len())
-	for i := range bounds {
-		r.sync(syncType)
-		if r.bool() {
-			r.len()
-		} else {
-			r.reloc(relocType)
-		}
-
-		// TODO(mdempsky): This result now needs to include the 'derived'
-		// bool too, but none of the callers currently depend on it
-		// anyway. Either fix it to be meaningful, or just get rid of it
-		// altogether.
-		bounds[i] = -1
-	}
-
 	tag := codeObj(r.code(syncCodeObj))
 
-	return path, name, tag, bounds
+	return path, name, tag
 }
diff --git a/src/cmd/compile/internal/noder/reader.go b/src/cmd/compile/internal/noder/reader.go
index de708769ba..44d1c4f28b 100644
--- a/src/cmd/compile/internal/noder/reader.go
+++ b/src/cmd/compile/internal/noder/reader.go
@@ -534,18 +534,10 @@ func (r *reader) obj() ir.Node {
 }
 
 func (pr *pkgReader) objIdx(idx int, implicits, explicits []*types.Type) ir.Node {
-	r := pr.newReader(relocObj, idx, syncObject1)
-	r.ext = pr.newReader(relocObjExt, idx, syncObject1)
-
-	_, sym := r.qualifiedIdent()
-
-	dict := &readerDict{}
-	r.dict = dict
-	r.ext.dict = dict
-
-	r.typeParamBounds(sym, implicits, explicits)
+	rname := pr.newReader(relocName, idx, syncObject1)
+	_, sym := rname.qualifiedIdent()
+	tag := codeObj(rname.code(syncCodeObj))
 
-	tag := codeObj(r.code(syncCodeObj))
 	if tag == objStub {
 		assert(!sym.IsBlank())
 		switch sym.Pkg {
@@ -556,30 +548,19 @@ func (pr *pkgReader) objIdx(idx int, implicits, explicits []*types.Type) ir.Node
 			return pri.pr.objIdx(pri.idx, nil, explicits)
 		}
 		if haveLegacyImports {
-			assert(!r.hasTypeParams())
+			assert(len(explicits) == 0)
 			return typecheck.Resolve(ir.NewIdent(src.NoXPos, sym))
 		}
 		base.Fatalf("unresolved stub: %v", sym)
 	}
 
-	{
-		rdict := pr.newReader(relocObjDict, idx, syncObject1)
-		r.dict.derived = make([]derivedInfo, rdict.len())
-		r.dict.derivedTypes = make([]*types.Type, len(r.dict.derived))
-		for i := range r.dict.derived {
-			r.dict.derived[i] = derivedInfo{rdict.reloc(relocType), rdict.bool()}
-		}
-		r.dict.funcs = make([]objInfo, rdict.len())
-		r.dict.funcsObj = make([]ir.Node, len(r.dict.funcs))
-		for i := range r.dict.funcs {
-			objIdx := rdict.reloc(relocObj)
-			targs := make([]typeInfo, rdict.len())
-			for j := range targs {
-				targs[j] = rdict.typInfo()
-			}
-			r.dict.funcs[i] = objInfo{idx: objIdx, explicits: targs}
-		}
-	}
+	dict := pr.objDictIdx(sym, idx, implicits, explicits)
+
+	r := pr.newReader(relocObj, idx, syncObject1)
+	r.ext = pr.newReader(relocObjExt, idx, syncObject1)
+
+	r.dict = dict
+	r.ext.dict = dict
 
 	sym = r.mangle(sym)
 	if !sym.IsBlank() && sym.Def != nil {
@@ -692,8 +673,10 @@ func (r *reader) mangle(sym *types.Sym) *types.Sym {
 	return sym.Pkg.Lookup(buf.String())
 }
 
-func (r *reader) typeParamBounds(sym *types.Sym, implicits, explicits []*types.Type) {
-	r.sync(syncTypeParamBounds)
+func (pr *pkgReader) objDictIdx(sym *types.Sym, idx int, implicits, explicits []*types.Type) *readerDict {
+	r := pr.newReader(relocObjDict, idx, syncObject1)
+
+	var dict readerDict
 
 	nimplicits := r.len()
 	nexplicits := r.len()
@@ -702,12 +685,11 @@ func (r *reader) typeParamBounds(sym *types.Sym, implicits, explicits []*types.T
 		base.Fatalf("%v has %v+%v params, but instantiated with %v+%v args", sym, nimplicits, nexplicits, len(implicits), len(explicits))
 	}
 
-	r.dict.targs = append(implicits[:nimplicits:nimplicits], explicits...)
-	r.dict.implicits = nimplicits
+	dict.targs = append(implicits[:nimplicits:nimplicits], explicits...)
+	dict.implicits = nimplicits
 
 	// For stenciling, we can just skip over the type parameters.
-
-	for range r.dict.targs[r.dict.implicits:] {
+	for range dict.targs[dict.implicits:] {
 		// Skip past bounds without actually evaluating them.
 		r.sync(syncType)
 		if r.bool() {
@@ -716,6 +698,25 @@ func (r *reader) typeParamBounds(sym *types.Sym, implicits, explicits []*types.T
 			r.reloc(relocType)
 		}
 	}
+
+	dict.derived = make([]derivedInfo, r.len())
+	dict.derivedTypes = make([]*types.Type, len(dict.derived))
+	for i := range dict.derived {
+		dict.derived[i] = derivedInfo{r.reloc(relocType), r.bool()}
+	}
+
+	dict.funcs = make([]objInfo, r.len())
+	dict.funcsObj = make([]ir.Node, len(dict.funcs))
+	for i := range dict.funcs {
+		objIdx := r.reloc(relocObj)
+		targs := make([]typeInfo, r.len())
+		for j := range targs {
+			targs[j] = r.typInfo()
+		}
+		dict.funcs[i] = objInfo{idx: objIdx, explicits: targs}
+	}
+
+	return &dict
 }
 
 func (r *reader) typeParamNames() {
@@ -790,7 +791,11 @@ func (r *reader) selector() (origPkg *types.Pkg, sym *types.Sym) {
 }
 
 func (r *reader) hasTypeParams() bool {
-	return r.dict != nil && len(r.dict.targs) != 0
+	return r.dict.hasTypeParams()
+}
+
+func (dict *readerDict) hasTypeParams() bool {
+	return dict != nil && len(dict.targs) != 0
 }
 
 // @@@ Compiler extensions
diff --git a/src/cmd/compile/internal/noder/reader2.go b/src/cmd/compile/internal/noder/reader2.go
index a2339145fa..297fa59439 100644
--- a/src/cmd/compile/internal/noder/reader2.go
+++ b/src/cmd/compile/internal/noder/reader2.go
@@ -358,29 +358,22 @@ func (r *reader2) obj() (types2.Object, []types2.Type) {
 }
 
 func (pr *pkgReader2) objIdx(idx int) (*types2.Package, string) {
-	r := pr.newReader(relocObj, idx, syncObject1)
-	r.dict = &reader2Dict{}
+	rname := pr.newReader(relocName, idx, syncObject1)
 
-	objPkg, objName := r.qualifiedIdent()
+	objPkg, objName := rname.qualifiedIdent()
 	assert(objName != "")
 
-	r.typeParamBounds()
-	tag := codeObj(r.code(syncCodeObj))
+	tag := codeObj(rname.code(syncCodeObj))
 
 	if tag == objStub {
 		assert(objPkg == nil)
 		return objPkg, objName
 	}
 
-	{
-		rdict := r.p.newReader(relocObjDict, idx, syncObject1)
-		r.dict.derived = make([]derivedInfo, rdict.len())
-		r.dict.derivedTypes = make([]types2.Type, len(r.dict.derived))
-		for i := range r.dict.derived {
-			r.dict.derived[i] = derivedInfo{rdict.reloc(relocType), rdict.bool()}
-		}
-		// function references follow, but reader2 doesn't need those
-	}
+	dict := pr.objDictIdx(idx)
+
+	r := pr.newReader(relocObj, idx, syncObject1)
+	r.dict = dict
 
 	objPkg.Scope().InsertLazy(objName, func() types2.Object {
 		switch tag {
@@ -439,17 +432,29 @@ func (r *reader2) value() (types2.Type, constant.Value) {
 	return r.typ(), r.rawValue()
 }
 
-func (r *reader2) typeParamBounds() {
-	r.sync(syncTypeParamBounds)
+func (pr *pkgReader2) objDictIdx(idx int) *reader2Dict {
+	r := pr.newReader(relocObjDict, idx, syncObject1)
+
+	var dict reader2Dict
 
 	if implicits := r.len(); implicits != 0 {
 		base.Fatalf("unexpected object with %v implicit type parameter(s)", implicits)
 	}
 
-	r.dict.bounds = make([]typeInfo, r.len())
-	for i := range r.dict.bounds {
-		r.dict.bounds[i] = r.typInfo()
+	dict.bounds = make([]typeInfo, r.len())
+	for i := range dict.bounds {
+		dict.bounds[i] = r.typInfo()
+	}
+
+	dict.derived = make([]derivedInfo, r.len())
+	dict.derivedTypes = make([]types2.Type, len(dict.derived))
+	for i := range dict.derived {
+		dict.derived[i] = derivedInfo{r.reloc(relocType), r.bool()}
 	}
+
+	// function references follow, but reader2 doesn't need those
+
+	return &dict
 }
 
 func (r *reader2) typeParamNames() []*types2.TypeName {
diff --git a/src/cmd/compile/internal/noder/reloc.go b/src/cmd/compile/internal/noder/reloc.go
index 4eb6bcdb1c..669a6182e6 100644
--- a/src/cmd/compile/internal/noder/reloc.go
+++ b/src/cmd/compile/internal/noder/reloc.go
@@ -31,6 +31,7 @@ const (
 	relocMeta
 	relocPosBase
 	relocPkg
+	relocName
 	relocType
 	relocObj
 	relocObjExt
diff --git a/src/cmd/compile/internal/noder/sync.go b/src/cmd/compile/internal/noder/sync.go
index aef98dbd78..7af558f8b2 100644
--- a/src/cmd/compile/internal/noder/sync.go
+++ b/src/cmd/compile/internal/noder/sync.go
@@ -183,4 +183,5 @@ const (
 	syncTypeParamNames
 	syncTypeParamBounds
 	syncImplicitTypes
+	syncObjectName
 )
diff --git a/src/cmd/compile/internal/noder/unified.go b/src/cmd/compile/internal/noder/unified.go
index e8c203ae46..9f80ca000d 100644
--- a/src/cmd/compile/internal/noder/unified.go
+++ b/src/cmd/compile/internal/noder/unified.go
@@ -263,7 +263,7 @@ func readPackage(pr *pkgReader, importpkg *types.Pkg) {
 		idx := r.reloc(relocObj)
 		assert(r.len() == 0)
 
-		path, name, code, _ := r.p.peekObj(idx)
+		path, name, code := r.p.peekObj(idx)
 		if code != objStub {
 			objReader[types.NewPkg(path, "").Lookup(name)] = pkgReaderIndex{pr, idx, nil}
 		}
@@ -298,7 +298,7 @@ func writeNewExport(out io.Writer) {
 			idx := r.reloc(relocObj)
 			assert(r.len() == 0)
 
-			xpath, xname, xtag, _ := pr.peekObj(idx)
+			xpath, xname, xtag := pr.peekObj(idx)
 			assert(xpath == pr.pkgPath)
 			assert(xtag != objStub)
 
diff --git a/src/cmd/compile/internal/noder/writer.go b/src/cmd/compile/internal/noder/writer.go
index 48884056f3..bf60246d64 100644
--- a/src/cmd/compile/internal/noder/writer.go
+++ b/src/cmd/compile/internal/noder/writer.go
@@ -505,60 +505,45 @@ func (pw *pkgWriter) objIdx(obj types2.Object) int {
 
 	w := pw.newWriter(relocObj, syncObject1)
 	w.ext = pw.newWriter(relocObjExt, syncObject1)
+	wname := pw.newWriter(relocName, syncObject1)
 	wdict := pw.newWriter(relocObjDict, syncObject1)
 
 	pw.globalsIdx[obj] = w.idx // break cycles
 	assert(w.ext.idx == w.idx)
+	assert(wname.idx == w.idx)
 	assert(wdict.idx == w.idx)
 
 	w.dict = dict
 	w.ext.dict = dict
 
-	// Ident goes first so importer can avoid unnecessary work if
-	// they've already resolved this object.
-	w.qualifiedIdent(obj)
-
-	w.typeParamBounds(objTypeParams(obj))
-
-	w.doObj(obj)
-
+	code := w.doObj(obj)
 	w.flush()
 	w.ext.flush()
 
-	// Done writing out the object description; write out the list of
-	// derived types and instantiated functions found along the way.
-	wdict.len(len(dict.derived))
-	for _, typ := range dict.derived {
-		wdict.reloc(relocType, typ.idx)
-		wdict.bool(typ.needed)
-	}
-	wdict.len(len(dict.funcs))
-	for _, fn := range dict.funcs {
-		wdict.reloc(relocObj, fn.idx)
-		wdict.len(len(fn.explicits))
-		for _, targ := range fn.explicits {
-			wdict.typInfo(targ)
-		}
-	}
+	wname.qualifiedIdent(obj)
+	wname.code(code)
+	wname.flush()
+
+	wdict.objDict(obj, w.dict)
 	wdict.flush()
 
 	return w.idx
 }
 
-func (w *writer) doObj(obj types2.Object) {
+func (w *writer) doObj(obj types2.Object) codeObj {
 	if obj.Pkg() != w.p.curpkg {
-		w.code(objStub)
-		return
+		return objStub
 	}
 
 	switch obj := obj.(type) {
 	default:
 		w.p.unexpected("object", obj)
+		panic("unreachable")
 
 	case *types2.Const:
-		w.code(objConst)
 		w.pos(obj)
 		w.value(obj.Type(), obj.Val())
+		return objConst
 
 	case *types2.Func:
 		decl, ok := w.p.funDecls[obj]
@@ -584,28 +569,26 @@ func (w *writer) doObj(obj types2.Object) {
 			sig = types2.NewSignature(nil, types2.NewTuple(params...), sig.Results(), sig.Variadic())
 		}
 
-		w.code(objFunc)
 		w.pos(obj)
 		w.typeParamNames(sig.TParams())
 		w.signature(sig)
 		w.pos(decl)
 		w.ext.funcExt(obj)
+		return objFunc
 
 	case *types2.TypeName:
 		decl, ok := w.p.typDecls[obj]
 		assert(ok)
 
 		if obj.IsAlias() {
-			w.code(objAlias)
 			w.pos(obj)
 			w.typ(obj.Type())
-			break
+			return objAlias
 		}
 
 		named := obj.Type().(*types2.Named)
 		assert(named.TArgs() == nil)
 
-		w.code(objType)
 		w.pos(obj)
 		w.typeParamNames(named.TParams())
 		w.ext.typeExt(obj)
@@ -616,11 +599,13 @@ func (w *writer) doObj(obj types2.Object) {
 			w.method(named.Method(i))
 		}
 
+		return objType
+
 	case *types2.Var:
-		w.code(objVar)
 		w.pos(obj)
 		w.typ(obj.Type())
 		w.ext.varExt(obj)
+		return objVar
 	}
 }
 
@@ -638,15 +623,41 @@ func (w *writer) value(typ types2.Type, val constant.Value) {
 	w.rawValue(val)
 }
 
-func (w *writer) typeParamBounds(tparams []*types2.TypeName) {
-	w.sync(syncTypeParamBounds)
+// objDict writes the dictionary needed for reading the given object.
+func (w *writer) objDict(obj types2.Object, dict *writerDict) {
+	// TODO(mdempsky): Split objDict into multiple entries? reader.go
+	// doesn't care about the type parameter bounds, and reader2.go
+	// doesn't care about referenced functions.
+
+	w.dict = dict // TODO(mdempsky): This is a bit sketchy.
 
-	w.len(len(w.dict.implicits))
+	w.len(len(dict.implicits))
 
+	tparams := objTypeParams(obj)
 	w.len(len(tparams))
 	for _, tparam := range tparams {
 		w.typ(tparam.Type().(*types2.TypeParam).Bound())
 	}
+
+	nderived := len(dict.derived)
+	w.len(nderived)
+	for _, typ := range dict.derived {
+		w.reloc(relocType, typ.idx)
+		w.bool(typ.needed)
+	}
+
+	nfuncs := len(dict.funcs)
+	w.len(nfuncs)
+	for _, fn := range dict.funcs {
+		w.reloc(relocObj, fn.idx)
+		w.len(len(fn.explicits))
+		for _, targ := range fn.explicits {
+			w.typInfo(targ)
+		}
+	}
+
+	assert(len(dict.derived) == nderived)
+	assert(len(dict.funcs) == nfuncs)
 }
 
 func (w *writer) typeParamNames(tparams []*types2.TypeName) {