[dev.unified] cmd/compile: remove package height

After CL 410654, symbols are now sorted by package path, package height
is not necessary anymore.

Updates #51734

Change-Id: I976edd2e574dda68eb5c76cf95645b9dce051393
Reviewed-on: https://go-review.googlesource.com/c/go/+/410342
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

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

@@ -75,11 +75,6 @@ func Main(archInit func(*ssagen.ArchInfo)) {
 
 	types.LocalPkg = types.NewPkg(base.Ctxt.Pkgpath, "")
 
-	// We won't know localpkg's height until after import
-	// processing. In the mean time, set to MaxPkgHeight to ensure
-	// height comparisons at least work until then.
-	types.LocalPkg.Height = types.MaxPkgHeight
-
 	// pseudo-package, for scoping
 	types.BuiltinPkg = types.NewPkg("go.builtin", "") // TODO(gri) name this package go.builtin?
 	types.BuiltinPkg.Prefix = "go.builtin"            // not go%2ebuiltin

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

@@ -219,7 +219,6 @@ type typeDelayInfo struct {
 
 func (g *irgen) generate(noders []*noder) {
 	types.LocalPkg.Name = g.self.Name()
-	types.LocalPkg.Height = g.self.Height()
 	typecheck.TypecheckAllowed = true
 
 	// Prevent size calculations until we set the underlying type

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

@@ -288,7 +288,7 @@ func (r *reader) doPkg() *types.Pkg {
 	}
 
 	name := r.String()
-	height := r.Len()
+	_ = r.Len() // was package height, but not necessary anymore.
 
 	pkg := types.NewPkg(path, "")
 
@@ -298,12 +298,6 @@ func (r *reader) doPkg() *types.Pkg {
 		base.Assertf(pkg.Name == name, "package %q has name %q, but want %q", pkg.Path, pkg.Name, name)
 	}
 
-	if pkg.Height == 0 {
-		pkg.Height = height
-	} else {
-		base.Assertf(pkg.Height == height, "package %q has height %v, but want %v", pkg.Path, pkg.Height, height)
-	}
-
 	return pkg
 }
 

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

@@ -82,7 +82,6 @@ func unified(noders []*noder) {
 	base.Flag.Lang = fmt.Sprintf("go1.%d", goversion.Version)
 	types.ParseLangFlag()
 
-	types.LocalPkg.Height = 0 // reset so pkgReader.pkgIdx doesn't complain
 	target := typecheck.Target
 
 	typecheck.TypecheckAllowed = true

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

@@ -241,7 +241,7 @@ func (pw *pkgWriter) pkgIdx(pkg *types2.Package) pkgbits.Index {
 		base.Assertf(path != "builtin" && path != "unsafe", "unexpected path for user-defined package: %q", path)
 		w.String(path)
 		w.String(pkg.Name())
-		w.Len(pkg.Height())
+		w.Len(0) // was package height, but not necessary anymore.
 
 		w.Len(len(pkg.Imports()))
 		for _, imp := range pkg.Imports() {

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

@@ -405,7 +405,7 @@ func (w *exportWriter) writeIndex(index map[*types.Sym]uint64, mainIndex bool) {
 		w.string(exportPath(pkg))
 		if mainIndex {
 			w.string(pkg.Name)
-			w.uint64(uint64(pkg.Height))
+			w.uint64(0) // was package height, but not necessary anymore.
 		}
 
 		// Sort symbols within a package by name.

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

@@ -175,10 +175,9 @@ func ReadImports(pkg *types.Pkg, data string) {
 	for nPkgs := ird.uint64(); nPkgs > 0; nPkgs-- {
 		pkg := p.pkgAt(ird.uint64())
 		pkgName := p.stringAt(ird.uint64())
-		pkgHeight := int(ird.uint64())
+		_ = int(ird.uint64()) // was package height, but not necessary anymore.
 		if pkg.Name == "" {
 			pkg.Name = pkgName
-			pkg.Height = pkgHeight
 			types.NumImport[pkgName]++
 
 			// TODO(mdempsky): This belongs somewhere else.
@@ -187,9 +186,6 @@ func ReadImports(pkg *types.Pkg, data string) {
 			if pkg.Name != pkgName {
 				base.Fatalf("conflicting package names %v and %v for path %q", pkg.Name, pkgName, pkg.Path)
 			}
-			if pkg.Height != pkgHeight {
-				base.Fatalf("conflicting package heights %v and %v for path %q", pkg.Height, pkgHeight, pkg.Path)
-			}
 		}
 
 		for nSyms := ird.uint64(); nSyms > 0; nSyms-- {

src/cmd/compile/internal/types/pkg.go

@@ -16,9 +16,6 @@ import (
 // pkgMap maps a package path to a package.
 var pkgMap = make(map[string]*Pkg)
 
-// MaxPkgHeight is a height greater than any likely package height.
-const MaxPkgHeight = 1e9
-
 type Pkg struct {
 	Path    string // string literal used in import statement, e.g. "runtime/internal/sys"
 	Name    string // package name, e.g. "sys"
@@ -26,12 +23,6 @@ type Pkg struct {
 	Syms    map[string]*Sym
 	Pathsym *obj.LSym
 
-	// Height is the package's height in the import graph. Leaf
-	// packages (i.e., packages with no imports) have height 0,
-	// and all other packages have height 1 plus the maximum
-	// height of their imported packages.
-	Height int
-
 	Direct bool // imported directly
 }