[dev.link] cmd/link: delete old object file format support

There are more cleanups to do, but I want to keep this CL mostly
a pure deletion.

Change-Id: I30f4891a2ea54545fd6b83041746ab65895537e1
Reviewed-on: https://go-review.googlesource.com/c/go/+/206558
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jeremy Faller <jeremy@golang.org>

1 files changed, 1 insertions, 300 deletions

diff --git a/src/cmd/link/internal/ld/deadcode.go b/src/cmd/link/internal/ld/deadcode.go
index e79207e2b8..4a53d7947b 100644
--- a/src/cmd/link/internal/ld/deadcode.go
+++ b/src/cmd/link/internal/ld/deadcode.go
@@ -6,11 +6,7 @@ package ld
 
 import (
 	"cmd/internal/objabi"
-	"cmd/internal/sys"
 	"cmd/link/internal/sym"
-	"fmt"
-	"strings"
-	"unicode"
 )
 
 // deadcode marks all reachable symbols.
@@ -46,84 +42,7 @@ import (
 //
 // Any unreached text symbols are removed from ctxt.Textp.
 func deadcode(ctxt *Link) {
-	if ctxt.Debugvlog != 0 {
-		ctxt.Logf("deadcode\n")
-	}
-
-	if *flagNewobj {
-		deadcode2(ctxt)
-		return
-	}
-
-	d := &deadcodepass{
-		ctxt:        ctxt,
-		ifaceMethod: make(map[methodsig]bool),
-	}
-
-	// First, flood fill any symbols directly reachable in the call
-	// graph from *flagEntrySymbol. Ignore all methods not directly called.
-	d.init()
-	d.flood()
-
-	callSym := ctxt.Syms.ROLookup("reflect.Value.Call", sym.SymVerABIInternal)
-	methSym := ctxt.Syms.ROLookup("reflect.Value.Method", sym.SymVerABIInternal)
-	reflectSeen := false
-
-	if ctxt.DynlinkingGo() {
-		// Exported methods may satisfy interfaces we don't know
-		// about yet when dynamically linking.
-		reflectSeen = true
-	}
-
-	for {
-		if !reflectSeen {
-			if d.reflectMethod || (callSym != nil && callSym.Attr.Reachable()) || (methSym != nil && methSym.Attr.Reachable()) {
-				// Methods might be called via reflection. Give up on
-				// static analysis, mark all exported methods of
-				// all reachable types as reachable.
-				reflectSeen = true
-			}
-		}
-
-		// Mark all methods that could satisfy a discovered
-		// interface as reachable. We recheck old marked interfaces
-		// as new types (with new methods) may have been discovered
-		// in the last pass.
-		var rem []methodref
-		for _, m := range d.markableMethods {
-			if (reflectSeen && m.isExported()) || d.ifaceMethod[m.m] {
-				d.markMethod(m)
-			} else {
-				rem = append(rem, m)
-			}
-		}
-		d.markableMethods = rem
-
-		if len(d.markQueue) == 0 {
-			// No new work was discovered. Done.
-			break
-		}
-		d.flood()
-	}
-
-	// Remove all remaining unreached R_METHODOFF relocations.
-	for _, m := range d.markableMethods {
-		for _, r := range m.r {
-			d.cleanupReloc(r)
-		}
-	}
-
-	if ctxt.BuildMode != BuildModeShared {
-		// Keep a itablink if the symbol it points at is being kept.
-		// (When BuildModeShared, always keep itablinks.)
-		for _, s := range ctxt.Syms.Allsym {
-			if strings.HasPrefix(s.Name, "go.itablink.") {
-				s.Attr.Set(sym.AttrReachable, len(s.R) == 1 && s.R[0].Sym.Attr.Reachable())
-			}
-		}
-	}
-
-	addToTextp(ctxt)
+	deadcode2(ctxt)
 }
 
 func addToTextp(ctxt *Link) {
@@ -188,221 +107,3 @@ func addToTextp(ctxt *Link) {
 		ctxt.Textp = textp
 	}
 }
-
-// methodref holds the relocations from a receiver type symbol to its
-// method. There are three relocations, one for each of the fields in
-// the reflect.method struct: mtyp, ifn, and tfn.
-type methodref struct {
-	m   methodsig
-	src *sym.Symbol   // receiver type symbol
-	r   [3]*sym.Reloc // R_METHODOFF relocations to fields of runtime.method
-}
-
-func (m methodref) ifn() *sym.Symbol { return m.r[1].Sym }
-
-func (m methodref) isExported() bool {
-	for _, r := range m.m {
-		return unicode.IsUpper(r)
-	}
-	panic("methodref has no signature")
-}
-
-// deadcodepass holds state for the deadcode flood fill.
-type deadcodepass struct {
-	ctxt            *Link
-	markQueue       []*sym.Symbol      // symbols to flood fill in next pass
-	ifaceMethod     map[methodsig]bool // methods declared in reached interfaces
-	markableMethods []methodref        // methods of reached types
-	reflectMethod   bool
-}
-
-func (d *deadcodepass) cleanupReloc(r *sym.Reloc) {
-	if r.Sym.Attr.Reachable() {
-		r.Type = objabi.R_ADDROFF
-	} else {
-		if d.ctxt.Debugvlog > 1 {
-			d.ctxt.Logf("removing method %s\n", r.Sym.Name)
-		}
-		r.Sym = nil
-		r.Siz = 0
-	}
-}
-
-// mark appends a symbol to the mark queue for flood filling.
-func (d *deadcodepass) mark(s, parent *sym.Symbol) {
-	if s == nil || s.Attr.Reachable() {
-		return
-	}
-	if s.Attr.ReflectMethod() {
-		d.reflectMethod = true
-	}
-	if *flagDumpDep {
-		p := "_"
-		if parent != nil {
-			p = parent.Name
-		}
-		fmt.Printf("%s -> %s\n", p, s.Name)
-	}
-	s.Attr |= sym.AttrReachable
-	if d.ctxt.Reachparent != nil {
-		d.ctxt.Reachparent[s] = parent
-	}
-	d.markQueue = append(d.markQueue, s)
-}
-
-// markMethod marks a method as reachable.
-func (d *deadcodepass) markMethod(m methodref) {
-	for _, r := range m.r {
-		d.mark(r.Sym, m.src)
-		r.Type = objabi.R_ADDROFF
-	}
-}
-
-// init marks all initial symbols as reachable.
-// In a typical binary, this is *flagEntrySymbol.
-func (d *deadcodepass) init() {
-	var names []string
-
-	if d.ctxt.BuildMode == BuildModeShared {
-		// Mark all symbols defined in this library as reachable when
-		// building a shared library.
-		for _, s := range d.ctxt.Syms.Allsym {
-			if s.Type != 0 && s.Type != sym.SDYNIMPORT {
-				d.mark(s, nil)
-			}
-		}
-	} else {
-		// In a normal binary, start at main.main and the init
-		// functions and mark what is reachable from there.
-
-		if d.ctxt.linkShared && (d.ctxt.BuildMode == BuildModeExe || d.ctxt.BuildMode == BuildModePIE) {
-			names = append(names, "main.main", "main..inittask")
-		} else {
-			// The external linker refers main symbol directly.
-			if d.ctxt.LinkMode == LinkExternal && (d.ctxt.BuildMode == BuildModeExe || d.ctxt.BuildMode == BuildModePIE) {
-				if d.ctxt.HeadType == objabi.Hwindows && d.ctxt.Arch.Family == sys.I386 {
-					*flagEntrySymbol = "_main"
-				} else {
-					*flagEntrySymbol = "main"
-				}
-			}
-			names = append(names, *flagEntrySymbol)
-			if d.ctxt.BuildMode == BuildModePlugin {
-				names = append(names, objabi.PathToPrefix(*flagPluginPath)+"..inittask", objabi.PathToPrefix(*flagPluginPath)+".main", "go.plugin.tabs")
-
-				// We don't keep the go.plugin.exports symbol,
-				// but we do keep the symbols it refers to.
-				exports := d.ctxt.Syms.ROLookup("go.plugin.exports", 0)
-				if exports != nil {
-					for i := range exports.R {
-						d.mark(exports.R[i].Sym, nil)
-					}
-				}
-			}
-		}
-		for _, s := range dynexp {
-			d.mark(s, nil)
-		}
-	}
-
-	for _, name := range names {
-		// Mark symbol as an data/ABI0 symbol.
-		d.mark(d.ctxt.Syms.ROLookup(name, 0), nil)
-		// Also mark any Go functions (internal ABI).
-		d.mark(d.ctxt.Syms.ROLookup(name, sym.SymVerABIInternal), nil)
-	}
-}
-
-// flood fills symbols reachable from the markQueue symbols.
-// As it goes, it collects methodref and interface method declarations.
-func (d *deadcodepass) flood() {
-	for len(d.markQueue) > 0 {
-		s := d.markQueue[0]
-		d.markQueue = d.markQueue[1:]
-		if s.Type == sym.STEXT {
-			if d.ctxt.Debugvlog > 1 {
-				d.ctxt.Logf("marktext %s\n", s.Name)
-			}
-		}
-
-		if strings.HasPrefix(s.Name, "type.") && s.Name[5] != '.' {
-			if len(s.P) == 0 {
-				// Probably a bug. The undefined symbol check
-				// later will give a better error than deadcode.
-				continue
-			}
-			if decodetypeKind(d.ctxt.Arch, s.P)&kindMask == kindInterface {
-				for _, sig := range decodeIfaceMethods(d.ctxt.Arch, s) {
-					if d.ctxt.Debugvlog > 1 {
-						d.ctxt.Logf("reached iface method: %s\n", sig)
-					}
-					d.ifaceMethod[sig] = true
-				}
-			}
-		}
-
-		mpos := 0 // 0-3, the R_METHODOFF relocs of runtime.uncommontype
-		var methods []methodref
-		for i := range s.R {
-			r := &s.R[i]
-			if r.Sym == nil {
-				continue
-			}
-			if r.Type == objabi.R_WEAKADDROFF {
-				// An R_WEAKADDROFF relocation is not reason
-				// enough to mark the pointed-to symbol as
-				// reachable.
-				continue
-			}
-			if r.Sym.Type == sym.SABIALIAS {
-				// Patch this relocation through the
-				// ABI alias before marking.
-				r.Sym = resolveABIAlias(r.Sym)
-			}
-			if r.Type != objabi.R_METHODOFF {
-				d.mark(r.Sym, s)
-				continue
-			}
-			// Collect rtype pointers to methods for
-			// later processing in deadcode.
-			if mpos == 0 {
-				m := methodref{src: s}
-				m.r[0] = r
-				methods = append(methods, m)
-			} else {
-				methods[len(methods)-1].r[mpos] = r
-			}
-			mpos++
-			if mpos == len(methodref{}.r) {
-				mpos = 0
-			}
-		}
-		if len(methods) > 0 {
-			// Decode runtime type information for type methods
-			// to help work out which methods can be called
-			// dynamically via interfaces.
-			methodsigs := decodetypeMethods(d.ctxt.Arch, s)
-			if len(methods) != len(methodsigs) {
-				panic(fmt.Sprintf("%q has %d method relocations for %d methods", s.Name, len(methods), len(methodsigs)))
-			}
-			for i, m := range methodsigs {
-				name := string(m)
-				name = name[:strings.Index(name, "(")]
-				if !strings.HasSuffix(methods[i].ifn().Name, name) {
-					panic(fmt.Sprintf("%q relocation for %q does not match method %q", s.Name, methods[i].ifn().Name, name))
-				}
-				methods[i].m = m
-			}
-			d.markableMethods = append(d.markableMethods, methods...)
-		}
-
-		if s.FuncInfo != nil {
-			for i := range s.FuncInfo.Funcdata {
-				d.mark(s.FuncInfo.Funcdata[i], s)
-			}
-		}
-		d.mark(s.Gotype, s)
-		d.mark(s.Sub, s)
-		d.mark(s.Outer, s)
-	}
-}