cmd/internal/obj: use map for symbol table

Change-Id: I105c1e7730c1e7ccf36297b9cbf96dc0a4868013
Reviewed-on: https://go-review.googlesource.com/7621
Reviewed-by: Rob Pike <r@golang.org>

src/cmd/internal/obj/link.go

@@ -115,7 +115,6 @@ type LSym struct {
 	Locals      int32
 	Value       int64
 	Size        int64
-	Hash        *LSym
 	Allsym      *LSym
 	Next        *LSym
 	Sub         *LSym
@@ -181,7 +180,7 @@ type Link struct {
 	Goroot             string
 	Goroot_final       string
 	Enforce_data_order int32
-	Hash               [LINKHASH]*LSym
+	Hash               map[SymVer]*LSym
 	Allsym             *LSym
 	Nsymbol            int32
 	Hist               *Hist
@@ -226,6 +225,11 @@ type Link struct {
 	Filesyms           *LSym
 }
 
+type SymVer struct {
+	Name    string
+	Version int
+}
+
 type Plist struct {
 	Name    *LSym
 	Firstpc *Prog
@@ -539,10 +543,6 @@ const (
 	A_PARAM
 )
 
-const (
-	LINKHASH = 100003
-)
-
 // Pcdata iterator.
 //	for(pciterinit(ctxt, &it, &pcd); !it.done; pciternext(&it)) { it.value holds in [it.pc, it.nextpc) }
 

src/cmd/internal/obj/sym.go

@@ -126,6 +126,7 @@ func Linknew(arch *LinkArch) *Link {
 	linksetexp()
 
 	ctxt := new(Link)
+	ctxt.Hash = make(map[SymVer]*LSym)
 	ctxt.Arch = arch
 	ctxt.Version = HistVersion
 	ctxt.Goroot = Getgoroot()
@@ -241,26 +242,14 @@ func linknewsym(ctxt *Link, symb string, v int) *LSym {
 }
 
 func _lookup(ctxt *Link, symb string, v int, creat int) *LSym {
-	h := uint32(v)
-	for i := 0; i < len(symb); i++ {
-		c := int(symb[i])
-		h = h + h + h + uint32(c)
-	}
-	h &= 0xffffff
-	h %= LINKHASH
-	for s := ctxt.Hash[h]; s != nil; s = s.Hash {
-		if int(s.Version) == v && s.Name == symb {
+	s := ctxt.Hash[SymVer{symb, v}]
+	if s != nil || creat == 0 {
 		return s
 	}
-	}
-	if creat == 0 {
-		return nil
-	}
 
-	s := linknewsym(ctxt, symb, v)
+	s = linknewsym(ctxt, symb, v)
 	s.Extname = s.Name
-	s.Hash = ctxt.Hash[h]
-	ctxt.Hash[h] = s
+	ctxt.Hash[SymVer{symb, v}] = s
 
 	return s
 }