[dev.link] cmd/link: assign special indices for builtin functions

Compiler-generated function references (e.g. call to
runtime.newobject) appear frequently. We assign special indices
for them, so they don't need to be referenced by name.

Change-Id: I2072594cbc56c9e1037a26e4aae12e68c2436e9f
Reviewed-on: https://go-review.googlesource.com/c/go/+/202085
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>

src/cmd/internal/goobj/readnew.go

@@ -49,7 +49,8 @@ func (r *objReader) readNew() {
 		case goobj2.PkgIdxNone:
 			i = int(s.SymIdx) + rr.NSym()
 		case goobj2.PkgIdxBuiltin:
-			panic("PkgIdxBuiltin is unused")
+			name, abi := goobj2.BuiltinName(int(s.SymIdx))
+			return SymID{name, int64(abi)}
 		case goobj2.PkgIdxSelf:
 			i = int(s.SymIdx)
 		default:

src/cmd/internal/goobj2/builtin.go

+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package goobj2
+
+// Builtin (compiler-generated) function references appear
+// frequently. We assign special indices for them, so they
+// don't need to be referenced by name.
+
+// NBuiltin returns the number of listed builtin
+// symbols.
+func NBuiltin() int {
+	return len(builtins)
+}
+
+// BuiltinName returns the name and ABI of the i-th
+// builtin symbol.
+func BuiltinName(i int) (string, int) {
+	return builtins[i].name, builtins[i].abi
+}
+
+// BuiltinIdx returns the index of the builtin with the
+// given name and abi, or -1 if it is not a builtin.
+func BuiltinIdx(name string, abi int) int {
+	i, ok := builtinMap[name]
+	if !ok {
+		return -1
+	}
+	if builtins[i].abi != abi {
+		return -1
+	}
+	return i
+}
+
+//go:generate go run mkbuiltin.go
+
+var builtinMap map[string]int
+
+func init() {
+	builtinMap = make(map[string]int, len(builtins))
+	for i, b := range builtins {
+		builtinMap[b.name] = i
+	}
+}

src/cmd/internal/goobj2/builtinlist.go

+// Code generated by mkbuiltin.go. DO NOT EDIT.
+
+package goobj2
+
+var builtins = [...]struct {
+	name string
+	abi  int
+}{
+	{"runtime.newobject", 1},
+	{"runtime.panicdivide", 1},
+	{"runtime.panicshift", 1},
+	{"runtime.panicmakeslicelen", 1},
+	{"runtime.throwinit", 1},
+	{"runtime.panicwrap", 1},
+	{"runtime.gopanic", 1},
+	{"runtime.gorecover", 1},
+	{"runtime.goschedguarded", 1},
+	{"runtime.goPanicIndex", 1},
+	{"runtime.goPanicIndexU", 1},
+	{"runtime.goPanicSliceAlen", 1},
+	{"runtime.goPanicSliceAlenU", 1},
+	{"runtime.goPanicSliceAcap", 1},
+	{"runtime.goPanicSliceAcapU", 1},
+	{"runtime.goPanicSliceB", 1},
+	{"runtime.goPanicSliceBU", 1},
+	{"runtime.goPanicSlice3Alen", 1},
+	{"runtime.goPanicSlice3AlenU", 1},
+	{"runtime.goPanicSlice3Acap", 1},
+	{"runtime.goPanicSlice3AcapU", 1},
+	{"runtime.goPanicSlice3B", 1},
+	{"runtime.goPanicSlice3BU", 1},
+	{"runtime.goPanicSlice3C", 1},
+	{"runtime.goPanicSlice3CU", 1},
+	{"runtime.printbool", 1},
+	{"runtime.printfloat", 1},
+	{"runtime.printint", 1},
+	{"runtime.printhex", 1},
+	{"runtime.printuint", 1},
+	{"runtime.printcomplex", 1},
+	{"runtime.printstring", 1},
+	{"runtime.printpointer", 1},
+	{"runtime.printiface", 1},
+	{"runtime.printeface", 1},
+	{"runtime.printslice", 1},
+	{"runtime.printnl", 1},
+	{"runtime.printsp", 1},
+	{"runtime.printlock", 1},
+	{"runtime.printunlock", 1},
+	{"runtime.concatstring2", 1},
+	{"runtime.concatstring3", 1},
+	{"runtime.concatstring4", 1},
+	{"runtime.concatstring5", 1},
+	{"runtime.concatstrings", 1},
+	{"runtime.cmpstring", 1},
+	{"runtime.intstring", 1},
+	{"runtime.slicebytetostring", 1},
+	{"runtime.slicebytetostringtmp", 1},
+	{"runtime.slicerunetostring", 1},
+	{"runtime.stringtoslicebyte", 1},
+	{"runtime.stringtoslicerune", 1},
+	{"runtime.slicecopy", 1},
+	{"runtime.slicestringcopy", 1},
+	{"runtime.decoderune", 1},
+	{"runtime.countrunes", 1},
+	{"runtime.convI2I", 1},
+	{"runtime.convT16", 1},
+	{"runtime.convT32", 1},
+	{"runtime.convT64", 1},
+	{"runtime.convTstring", 1},
+	{"runtime.convTslice", 1},
+	{"runtime.convT2E", 1},
+	{"runtime.convT2Enoptr", 1},
+	{"runtime.convT2I", 1},
+	{"runtime.convT2Inoptr", 1},
+	{"runtime.assertE2I", 1},
+	{"runtime.assertE2I2", 1},
+	{"runtime.assertI2I", 1},
+	{"runtime.assertI2I2", 1},
+	{"runtime.panicdottypeE", 1},
+	{"runtime.panicdottypeI", 1},
+	{"runtime.panicnildottype", 1},
+	{"runtime.ifaceeq", 1},
+	{"runtime.efaceeq", 1},
+	{"runtime.fastrand", 1},
+	{"runtime.makemap64", 1},
+	{"runtime.makemap", 1},
+	{"runtime.makemap_small", 1},
+	{"runtime.mapaccess1", 1},
+	{"runtime.mapaccess1_fast32", 1},
+	{"runtime.mapaccess1_fast64", 1},
+	{"runtime.mapaccess1_faststr", 1},
+	{"runtime.mapaccess1_fat", 1},
+	{"runtime.mapaccess2", 1},
+	{"runtime.mapaccess2_fast32", 1},
+	{"runtime.mapaccess2_fast64", 1},
+	{"runtime.mapaccess2_faststr", 1},
+	{"runtime.mapaccess2_fat", 1},
+	{"runtime.mapassign", 1},
+	{"runtime.mapassign_fast32", 1},
+	{"runtime.mapassign_fast32ptr", 1},
+	{"runtime.mapassign_fast64", 1},
+	{"runtime.mapassign_fast64ptr", 1},
+	{"runtime.mapassign_faststr", 1},
+	{"runtime.mapiterinit", 1},
+	{"runtime.mapdelete", 1},
+	{"runtime.mapdelete_fast32", 1},
+	{"runtime.mapdelete_fast64", 1},
+	{"runtime.mapdelete_faststr", 1},
+	{"runtime.mapiternext", 1},
+	{"runtime.mapclear", 1},
+	{"runtime.makechan64", 1},
+	{"runtime.makechan", 1},
+	{"runtime.chanrecv1", 1},
+	{"runtime.chanrecv2", 1},
+	{"runtime.chansend1", 1},
+	{"runtime.closechan", 1},
+	{"runtime.writeBarrier", 0},
+	{"runtime.typedmemmove", 1},
+	{"runtime.typedmemclr", 1},
+	{"runtime.typedslicecopy", 1},
+	{"runtime.selectnbsend", 1},
+	{"runtime.selectnbrecv", 1},
+	{"runtime.selectnbrecv2", 1},
+	{"runtime.selectsetpc", 1},
+	{"runtime.selectgo", 1},
+	{"runtime.block", 1},
+	{"runtime.makeslice", 1},
+	{"runtime.makeslice64", 1},
+	{"runtime.growslice", 1},
+	{"runtime.memmove", 1},
+	{"runtime.memclrNoHeapPointers", 1},
+	{"runtime.memclrHasPointers", 1},
+	{"runtime.memequal", 1},
+	{"runtime.memequal0", 1},
+	{"runtime.memequal8", 1},
+	{"runtime.memequal16", 1},
+	{"runtime.memequal32", 1},
+	{"runtime.memequal64", 1},
+	{"runtime.memequal128", 1},
+	{"runtime.f32equal", 1},
+	{"runtime.f64equal", 1},
+	{"runtime.c64equal", 1},
+	{"runtime.c128equal", 1},
+	{"runtime.strequal", 1},
+	{"runtime.interequal", 1},
+	{"runtime.nilinterequal", 1},
+	{"runtime.memhash", 1},
+	{"runtime.memhash0", 1},
+	{"runtime.memhash8", 1},
+	{"runtime.memhash16", 1},
+	{"runtime.memhash32", 1},
+	{"runtime.memhash64", 1},
+	{"runtime.memhash128", 1},
+	{"runtime.f32hash", 1},
+	{"runtime.f64hash", 1},
+	{"runtime.c64hash", 1},
+	{"runtime.c128hash", 1},
+	{"runtime.strhash", 1},
+	{"runtime.interhash", 1},
+	{"runtime.nilinterhash", 1},
+	{"runtime.int64div", 1},
+	{"runtime.uint64div", 1},
+	{"runtime.int64mod", 1},
+	{"runtime.uint64mod", 1},
+	{"runtime.float64toint64", 1},
+	{"runtime.float64touint64", 1},
+	{"runtime.float64touint32", 1},
+	{"runtime.int64tofloat64", 1},
+	{"runtime.uint64tofloat64", 1},
+	{"runtime.uint32tofloat64", 1},
+	{"runtime.complex128div", 1},
+	{"runtime.racefuncenter", 1},
+	{"runtime.racefuncenterfp", 1},
+	{"runtime.racefuncexit", 1},
+	{"runtime.raceread", 1},
+	{"runtime.racewrite", 1},
+	{"runtime.racereadrange", 1},
+	{"runtime.racewriterange", 1},
+	{"runtime.msanread", 1},
+	{"runtime.msanwrite", 1},
+	{"runtime.checkptrAlignment", 1},
+	{"runtime.checkptrArithmetic", 1},
+	{"runtime.x86HasPOPCNT", 0},
+	{"runtime.x86HasSSE41", 0},
+	{"runtime.arm64HasATOMICS", 0},
+	{"runtime.gcWriteBarrier", 0},
+	{"runtime.deferproc", 1},
+	{"runtime.deferprocStack", 1},
+	{"runtime.deferreturn", 1},
+	{"runtime.newproc", 1},
+	{"runtime.morestack", 0},
+	{"runtime.morestackc", 0},
+	{"runtime.morestack_noctxt", 0},
+}

src/cmd/internal/goobj2/mkbuiltin.go

+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+// Generate builtinlist.go from cmd/compile/internal/gc/builtin/runtime.go.
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/ast"
+	"go/format"
+	"go/parser"
+	"go/token"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+)
+
+var stdout = flag.Bool("stdout", false, "write to stdout instead of builtinlist.go")
+
+func main() {
+	flag.Parse()
+
+	var b bytes.Buffer
+	fmt.Fprintln(&b, "// Code generated by mkbuiltin.go. DO NOT EDIT.")
+	fmt.Fprintln(&b)
+	fmt.Fprintln(&b, "package goobj2")
+
+	mkbuiltin(&b)
+
+	out, err := format.Source(b.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+	if *stdout {
+		_, err = os.Stdout.Write(out)
+	} else {
+		err = ioutil.WriteFile("builtinlist.go", out, 0666)
+	}
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func mkbuiltin(w io.Writer) {
+	pkg := "runtime"
+	fset := token.NewFileSet()
+	path := filepath.Join("..", "..", "compile", "internal", "gc", "builtin", "runtime.go")
+	f, err := parser.ParseFile(fset, path, nil, 0)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	decls := make(map[string]bool)
+
+	fmt.Fprintf(w, "var builtins = [...]struct{ name string; abi int }{\n")
+	for _, decl := range f.Decls {
+		switch decl := decl.(type) {
+		case *ast.FuncDecl:
+			if decl.Recv != nil {
+				log.Fatal("methods unsupported")
+			}
+			if decl.Body != nil {
+				log.Fatal("unexpected function body")
+			}
+			declName := pkg + "." + decl.Name.Name
+			decls[declName] = true
+			fmt.Fprintf(w, "{%q, 1},\n", declName) // functions are ABIInternal (1)
+		case *ast.GenDecl:
+			if decl.Tok == token.IMPORT {
+				continue
+			}
+			if decl.Tok != token.VAR {
+				log.Fatal("unhandled declaration kind", decl.Tok)
+			}
+			for _, spec := range decl.Specs {
+				spec := spec.(*ast.ValueSpec)
+				if len(spec.Values) != 0 {
+					log.Fatal("unexpected values")
+				}
+				for _, name := range spec.Names {
+					declName := pkg + "." + name.Name
+					decls[declName] = true
+					fmt.Fprintf(w, "{%q, 0},\n", declName) // variables are ABI0
+				}
+			}
+		default:
+			log.Fatal("unhandled decl type", decl)
+		}
+	}
+
+	// The list above only contains ones that are used by the frontend.
+	// The backend may create more references of builtin functions.
+	// Add them.
+	for _, b := range extra {
+		name := pkg + "." + b.name
+		if decls[name] {
+			log.Fatalf("%q already added -- mkbuiltin.go out of sync?", name)
+		}
+		fmt.Fprintf(w, "{%q, %d},\n", name, b.abi)
+	}
+	fmt.Fprintln(w, "}")
+}
+
+var extra = [...]struct {
+	name string
+	abi  int
+}{
+	{"gcWriteBarrier", 0}, // asm function, ABI0
+	{"deferproc", 1},
+	{"deferprocStack", 1},
+	{"deferreturn", 1},
+	{"newproc", 1},
+	{"morestack", 0},        // asm function, ABI0
+	{"morestackc", 0},       // asm function, ABI0
+	{"morestack_noctxt", 0}, // asm function, ABI0
+}

src/cmd/internal/obj/sym.go

@@ -210,6 +210,17 @@ func (ctxt *Link) NumberSyms(asm bool) {
 		if rs.PkgIdx != goobj2.PkgIdxInvalid {
 			return
 		}
+		if !ctxt.Flag_linkshared {
+			// Assign special index for builtin symbols.
+			// Don't do it when linking against shared libraries, as the runtime
+			// may be in a different library.
+			if i := goobj2.BuiltinIdx(rs.Name, int(rs.ABI())); i != -1 {
+				rs.PkgIdx = goobj2.PkgIdxBuiltin
+				rs.SymIdx = int32(i)
+				rs.Set(AttrIndexed, true)
+				return
+			}
+		}
 		pkg := rs.Pkg
 		if pkg == "" || pkg == "\"\"" || pkg == "_" || !rs.Indexed() {
 			rs.PkgIdx = goobj2.PkgIdxNone

src/cmd/link/internal/loader/loader.go

@@ -91,11 +91,12 @@ func makeBitmap(n int) bitmap {
 
 // A Loader loads new object files and resolves indexed symbol references.
 type Loader struct {
-	start    map[*oReader]Sym // map from object file to its start index
-	objs     []objIdx         // sorted by start index (i.e. objIdx.i)
-	max      Sym              // current max index
-	extStart Sym              // from this index on, the symbols are externally defined
-	extSyms  []nameVer        // externally defined symbols
+	start       map[*oReader]Sym // map from object file to its start index
+	objs        []objIdx         // sorted by start index (i.e. objIdx.i)
+	max         Sym              // current max index
+	extStart    Sym              // from this index on, the symbols are externally defined
+	extSyms     []nameVer        // externally defined symbols
+	builtinSyms []Sym            // global index of builtin symbols
 
 	symsByName    [2]map[string]Sym // map symbol name to index, two maps are for ABI0 and ABIInternal
 	extStaticSyms map[nameVer]Sym   // externally defined static symbols, keyed by name
@@ -111,6 +112,7 @@ type Loader struct {
 }
 
 func NewLoader() *Loader {
+	nbuiltin := goobj2.NBuiltin()
 	return &Loader{
 		start:         make(map[*oReader]Sym),
 		objs:          []objIdx{{nil, 0}},
@@ -119,6 +121,7 @@ func NewLoader() *Loader {
 		overwrite:     make(map[Sym]Sym),
 		itablink:      make(map[Sym]struct{}),
 		extStaticSyms: make(map[nameVer]Sym),
+		builtinSyms:   make([]Sym, nbuiltin),
 	}
 }
 
@@ -272,7 +275,7 @@ func (l *Loader) resolve(r *oReader, s goobj2.SymRef) Sym {
 		v := abiToVer(osym.ABI, r.version)
 		return l.Lookup(name, v)
 	case goobj2.PkgIdxBuiltin:
-		panic("PkgIdxBuiltin not used")
+		return l.builtinSyms[s.SymIdx]
 	case goobj2.PkgIdxSelf:
 		rr = r
 	default:
@@ -575,6 +578,12 @@ func (l *Loader) Preload(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, lib *
 		if added && strings.HasPrefix(name, "go.itablink.") {
 			l.itablink[istart+Sym(i)] = struct{}{}
 		}
+		if added && strings.HasPrefix(name, "runtime.") {
+			if bi := goobj2.BuiltinIdx(name, v); bi != -1 {
+				// This is a definition of a builtin symbol. Record where it is.
+				l.builtinSyms[bi] = istart + Sym(i)
+			}
+		}
 	}
 
 	// The caller expects us consuming all the data