cmd/link: eliminate a bunch of open coded elf64/rela switches

We already have variables to track whether the target platform is
64-bit vs 32-bit or RELA vs REL, so no point in repeating the list of
obscure architecture characters everywhere.

Passes toolstash/buildall.

Change-Id: I6a07f74188ac592ef229a7c65848a9ba93013cdb
Reviewed-on: https://go-review.googlesource.com/21569
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Michael Hudson-Doyle <michael.hudson@canonical.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

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

@@ -2169,18 +2169,10 @@ func dwarfaddshstrings(shstrtab *LSym) {
 	elfstrdbg[ElfStrDebugStr] = Addstring(shstrtab, ".debug_str")
 	elfstrdbg[ElfStrGDBScripts] = Addstring(shstrtab, ".debug_gdb_scripts")
 	if Linkmode == LinkExternal {
-		switch Thearch.Thechar {
-		case '0', '6', '7', '9', 'z':
-			elfstrdbg[ElfStrRelDebugInfo] = Addstring(shstrtab, ".rela.debug_info")
-			elfstrdbg[ElfStrRelDebugAranges] = Addstring(shstrtab, ".rela.debug_aranges")
-			elfstrdbg[ElfStrRelDebugLine] = Addstring(shstrtab, ".rela.debug_line")
-			elfstrdbg[ElfStrRelDebugFrame] = Addstring(shstrtab, ".rela.debug_frame")
-		default:
-			elfstrdbg[ElfStrRelDebugInfo] = Addstring(shstrtab, ".rel.debug_info")
-			elfstrdbg[ElfStrRelDebugAranges] = Addstring(shstrtab, ".rel.debug_aranges")
-			elfstrdbg[ElfStrRelDebugLine] = Addstring(shstrtab, ".rel.debug_line")
-			elfstrdbg[ElfStrRelDebugFrame] = Addstring(shstrtab, ".rel.debug_frame")
-		}
+		elfstrdbg[ElfStrRelDebugInfo] = Addstring(shstrtab, elfRelType+".debug_info")
+		elfstrdbg[ElfStrRelDebugAranges] = Addstring(shstrtab, elfRelType+".debug_aranges")
+		elfstrdbg[ElfStrRelDebugLine] = Addstring(shstrtab, elfRelType+".debug_line")
+		elfstrdbg[ElfStrRelDebugFrame] = Addstring(shstrtab, elfRelType+".debug_frame")
 
 		infosym = Linklookup(Ctxt, ".debug_info", 0)
 		infosym.Attr |= AttrHidden
@@ -2222,10 +2214,9 @@ func dwarfaddelfsectionsyms() {
 
 func dwarfaddelfrelocheader(elfstr int, shdata *ElfShdr, off int64, size int64) {
 	sh := newElfShdr(elfstrdbg[elfstr])
-	switch Thearch.Thechar {
-	case '0', '6', '7', '9', 'z':
+	if elfRelType == ".rela" {
 		sh.type_ = SHT_RELA
-	default:
+	} else {
 		sh.type_ = SHT_REL
 	}
 

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

@@ -1885,10 +1885,9 @@ func doelf() {
 
 		s.Type = obj.SELFROSECT
 		s.Attr |= AttrReachable
-		switch Thearch.Thechar {
-		case '0', '6', '7', '9', 'z':
+		if elf64 {
 			s.Size += ELF64SYMSIZE
-		default:
+		} else {
 			s.Size += ELF32SYMSIZE
 		}
 
@@ -1967,10 +1966,9 @@ func doelf() {
 		elfwritedynentsym(s, DT_HASH, Linklookup(Ctxt, ".hash", 0))
 
 		elfwritedynentsym(s, DT_SYMTAB, Linklookup(Ctxt, ".dynsym", 0))
-		switch Thearch.Thechar {
-		case '0', '6', '7', '9', 'z':
+		if elf64 {
 			Elfwritedynent(s, DT_SYMENT, ELF64SYMSIZE)
-		default:
+		} else {
 			Elfwritedynent(s, DT_SYMENT, ELF32SYMSIZE)
 		}
 		elfwritedynentsym(s, DT_STRTAB, Linklookup(Ctxt, ".dynstr", 0))

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

@@ -66,8 +66,7 @@ func putelfstr(s string) int {
 }
 
 func putelfsyment(off int, addr int64, size int64, info int, shndx int, other int) {
-	switch Thearch.Thechar {
-	case '0', '6', '7', '9', 'z':
+	if elf64 {
 		Thearch.Lput(uint32(off))
 		Cput(uint8(info))
 		Cput(uint8(other))
@@ -75,8 +74,7 @@ func putelfsyment(off int, addr int64, size int64, info int, shndx int, other in
 		Thearch.Vput(uint64(addr))
 		Thearch.Vput(uint64(size))
 		Symsize += ELF64SYMSIZE
-
-	default:
+	} else {
 		Thearch.Lput(uint32(off))
 		Thearch.Lput(uint32(addr))
 		Thearch.Lput(uint32(size))