cmd/link: replace interface{} fields with concrete types

The LSym.Section and Section.Elfsect fields were defined as interface{} but
always had the same concrete type (*Section and *ElfShdr respectively) so just
define them with that type. Reduces size of LSym from 328 to 320 bytes and
reduces best-of-10 maxresident size from 246028k to 238036k when linking
libstd.so.

Change-Id: Ie7112c53e4c2c7ce5fe233b81372aa5633f572e8
Reviewed-on: https://go-review.googlesource.com/10410
Reviewed-by: Minux Ma <minux@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/link/internal/amd64/asm.go

@@ -405,9 +405,9 @@ func machoreloc1(r *ld.Reloc, sectoff int64) int {
 		v = uint32(rs.Dynid)
 		v |= 1 << 27 // external relocation
 	} else {
-		v = uint32((rs.Sect.(*ld.Section)).Extnum)
+		v = uint32(rs.Sect.Extnum)
 		if v == 0 {
-			ld.Diag("reloc %d to symbol %s in non-macho section %s type=%d", r.Type, rs.Name, (rs.Sect.(*ld.Section)).Name, rs.Type)
+			ld.Diag("reloc %d to symbol %s in non-macho section %s type=%d", r.Type, rs.Name, rs.Sect.Name, rs.Type)
 			return -1
 		}
 	}

src/cmd/link/internal/arm/asm.go

@@ -279,9 +279,9 @@ func machoreloc1(r *ld.Reloc, sectoff int64) int {
 		v = uint32(rs.Dynid)
 		v |= 1 << 27 // external relocation
 	} else {
-		v = uint32((rs.Sect.(*ld.Section)).Extnum)
+		v = uint32(rs.Sect.Extnum)
 		if v == 0 {
-			ld.Diag("reloc %d to symbol %s in non-macho section %s type=%d", r.Type, rs.Name, (rs.Sect.(*ld.Section)).Name, rs.Type)
+			ld.Diag("reloc %d to symbol %s in non-macho section %s type=%d", r.Type, rs.Name, rs.Sect.Name, rs.Type)
 			return -1
 		}
 	}

src/cmd/link/internal/arm64/asm.go

@@ -107,9 +107,9 @@ func machoreloc1(r *ld.Reloc, sectoff int64) int {
 		v = uint32(rs.Dynid)
 		v |= 1 << 27 // external relocation
 	} else {
-		v = uint32((rs.Sect.(*ld.Section)).Extnum)
+		v = uint32(rs.Sect.Extnum)
 		if v == 0 {
-			ld.Diag("reloc %d to symbol %s in non-macho section %s type=%d", r.Type, rs.Name, (rs.Sect.(*ld.Section)).Name, rs.Type)
+			ld.Diag("reloc %d to symbol %s in non-macho section %s type=%d", r.Type, rs.Name, rs.Sect.Name, rs.Type)
 			return -1
 		}
 	}

src/cmd/link/internal/ld/data.go

@@ -522,7 +522,7 @@ func relocsym(s *LSym) {
 				} else if HEADTYPE == obj.Hdarwin {
 					if r.Type == obj.R_CALL {
 						if rs.Type != obj.SHOSTOBJ {
-							o += int64(uint64(Symaddr(rs)) - (rs.Sect.(*Section)).Vaddr)
+							o += int64(uint64(Symaddr(rs)) - rs.Sect.Vaddr)
 						}
 						o -= int64(r.Off) // relative to section offset, not symbol
 					} else {
@@ -534,7 +534,7 @@ func relocsym(s *LSym) {
 					o += int64(r.Siz)
 					// GNU ld always add VirtualAddress of the .text section to the
 					// relocated address, compensate that.
-					o -= int64(s.Sect.(*Section).Vaddr - PEBASE)
+					o -= int64(s.Sect.Vaddr - PEBASE)
 				} else {
 					Diag("unhandled pcrel relocation for %s", headstring)
 				}
@@ -1681,7 +1681,7 @@ func address() {
 	for sym := datap; sym != nil; sym = sym.Next {
 		Ctxt.Cursym = sym
 		if sym.Sect != nil {
-			sym.Value += int64((sym.Sect.(*Section)).Vaddr)
+			sym.Value += int64(sym.Sect.Vaddr)
 		}
 		for sub = sym.Sub; sub != nil; sub = sub.Sub {
 			sub.Value += sym.Value

src/cmd/link/internal/ld/elf.go

@@ -1517,7 +1517,7 @@ func elfshreloc(sect *Section) *ElfShdr {
 		sh.entsize += uint64(Thearch.Regsize)
 	}
 	sh.link = uint32(elfshname(".symtab").shnum)
-	sh.info = uint32((sect.Elfsect.(*ElfShdr)).shnum)
+	sh.info = uint32(sect.Elfsect.shnum)
 	sh.off = sect.Reloff
 	sh.size = sect.Rellen
 	sh.addralign = uint64(Thearch.Regsize)

src/cmd/link/internal/ld/lib.go

@@ -162,7 +162,7 @@ type Section struct {
 	Length  uint64
 	Next    *Section
 	Seg     *Segment
-	Elfsect interface{}
+	Elfsect *ElfShdr
 	Reloff  uint64
 	Rellen  uint64
 }

src/cmd/link/internal/ld/link.go

@@ -78,7 +78,7 @@ type LSym struct {
 	File        string
 	Dynimplib   string
 	Dynimpvers  string
-	Sect        interface{}
+	Sect        *Section
 	Autom       *Auto
 	Pcln        *Pcln
 	P           []byte

src/cmd/link/internal/ld/macho.go

@@ -706,7 +706,7 @@ func machosymtab() {
 				Diag("missing section for %s", s.Name)
 				Adduint8(Ctxt, symtab, 0)
 			} else {
-				Adduint8(Ctxt, symtab, uint8((o.Sect.(*Section)).Extnum))
+				Adduint8(Ctxt, symtab, uint8(o.Sect.Extnum))
 			}
 			Adduint16(Ctxt, symtab, 0) // desc
 			adduintxx(Ctxt, symtab, uint64(Symaddr(s)), Thearch.Ptrsize)

src/cmd/link/internal/ld/symtab.go

@@ -132,12 +132,12 @@ func putelfsym(x *LSym, s string, t int, addr int64, size int64, ver int, go_ *L
 			Diag("missing section in putelfsym")
 			return
 		}
-		if xo.Sect.(*Section).Elfsect == nil {
+		if xo.Sect.Elfsect == nil {
 			Ctxt.Cursym = x
 			Diag("missing ELF section in putelfsym")
 			return
 		}
-		elfshnum = xo.Sect.(*Section).Elfsect.(*ElfShdr).shnum
+		elfshnum = xo.Sect.Elfsect.shnum
 	}
 
 	// One pass for each binding: STB_LOCAL, STB_GLOBAL,
@@ -163,7 +163,7 @@ func putelfsym(x *LSym, s string, t int, addr int64, size int64, ver int, go_ *L
 
 	off := putelfstr(s)
 	if Linkmode == LinkExternal && elfshnum != SHN_UNDEF {
-		addr -= int64(xo.Sect.(*Section).Vaddr)
+		addr -= int64(xo.Sect.Vaddr)
 	}
 	other := STV_DEFAULT
 	if x.Type&obj.SHIDDEN != 0 {

src/cmd/link/internal/x86/asm.go

@@ -276,9 +276,9 @@ func machoreloc1(r *ld.Reloc, sectoff int64) int {
 		v = uint32(rs.Dynid)
 		v |= 1 << 27 // external relocation
 	} else {
-		v = uint32((rs.Sect.(*ld.Section)).Extnum)
+		v = uint32(rs.Sect.Extnum)
 		if v == 0 {
-			ld.Diag("reloc %d to symbol %s in non-macho section %s type=%d", r.Type, rs.Name, (rs.Sect.(*ld.Section)).Name, rs.Type)
+			ld.Diag("reloc %d to symbol %s in non-macho section %s type=%d", r.Type, rs.Name, rs.Sect.Name, rs.Type)
 			return -1
 		}
 	}