[WebAssembly] Implement getRelocationValueString()

[sbc100]

Summary

And use it in llvm-objdump.

Split out from larger change: https://reviews.llvm.org/D44184

[yurydelendik]

Looks good

llvm/trunk/lib/Object/WasmObjectFile.cpp

void WasmObjectFile::moveRelocationNext(DataRefImpl &Rel) const {
   Rel.d.b++;
 }
 
 uint64_t WasmObjectFile::getRelocationOffset(DataRefImpl Ref) const {
   const wasm::WasmRelocation &Rel = getWasmRelocation(Ref);
   return Rel.Offset;
 }
 
-symbol_iterator WasmObjectFile::getRelocationSymbol(DataRefImpl Rel) const {
-  llvm_unreachable("not yet implemented");
-  SymbolRef Ref;
-  return symbol_iterator(Ref);
+symbol_iterator WasmObjectFile::getRelocationSymbol(DataRefImpl Ref) const {
+  const wasm::WasmRelocation &Rel = getWasmRelocation(Ref);
+  if (Rel.Type == wasm::R_WEBASSEMBLY_TYPE_INDEX_LEB)
+    return symbol_end();
+  DataRefImpl Sym;
+  Sym.d.a = Rel.Index;
+  Sym.d.b = 0;
+  return symbol_iterator(SymbolRef(Sym, this));
 }
 
 uint64_t WasmObjectFile::getRelocationType(DataRefImpl Ref) const {
   const wasm::WasmRelocation &Rel = getWasmRelocation(Ref);
   return Rel.Type;
 }
 
 void WasmObjectFile::getRelocationTypeName(

llvm/trunk/test/Object/objdump-relocations.test

 ELF-MIPSEL: R_MIPS_HI16 _gp_disp
 ELF-MIPSEL: R_MIPS_LO16 _gp_disp
 ELF-MIPSEL: R_MIPS_GOT16 $.str
 ELF-MIPSEL: R_MIPS_LO16 $.str
 ELF-MIPSEL: R_MIPS_CALL16 puts
 ELF-MIPSEL: R_MIPS_CALL16 SomeOtherFunction
 
 WASM:      CODE
-WASM-NEXT: R_WEBASSEMBLY_MEMORY_ADDR_SLEB 1+0
-WASM-NEXT: R_WEBASSEMBLY_FUNCTION_INDEX_LEB 2+0
-WASM-NEXT: R_WEBASSEMBLY_FUNCTION_INDEX_LEB 3+0
+WASM-NEXT: R_WEBASSEMBLY_MEMORY_ADDR_SLEB .L.str+0
+WASM-NEXT: R_WEBASSEMBLY_FUNCTION_INDEX_LEB puts+0
+WASM-NEXT: R_WEBASSEMBLY_FUNCTION_INDEX_LEB SomeOtherFunction+0
 
 ELF-complex-x86-64: .text
 ELF-complex-x86-64-NEXT: R_X86_64_8 .data-4
 ELF-complex-x86-64-NEXT: R_X86_64_16 .data-4
 ELF-complex-x86-64-NEXT: R_X86_64_32 .data-4
 ELF-complex-x86-64-NEXT: R_X86_64_32S .data-4
 ELF-complex-x86-64-NEXT: R_X86_64_64 .data-4
 ELF-complex-x86-64-NEXT: R_X86_64_PC32 .data-4-P
 ELF-complex-x86-64-NEXT: R_X86_64_32 .data+0
 ELF-complex-x86-64-NEXT: R_X86_64_32 .data+4

llvm/trunk/test/tools/llvm-objdump/WebAssembly/relocations.test

 ; RUN: llc -mtriple=wasm32-unknown-unknown-wasm -filetype=obj %s -o - | llvm-objdump -r - | FileCheck %s
 
 @foo1 = hidden global i32 1, align 4
 @foo2 = hidden global i32 1, align 4
 @bar = hidden global i32* @foo2, align 4
 
 ; CHECK:      RELOCATION RECORDS FOR [DATA]:
-; CHECK-NEXT: 00000018 R_WEBASSEMBLY_MEMORY_ADDR_I32 1+0
+; CHECK-NEXT: 00000018 R_WEBASSEMBLY_MEMORY_ADDR_I32 foo2+0

llvm/trunk/tools/llvm-objdump/llvm-objdump.cpp

static void printRelocationTargetName(const MachOObjectFile *O,
 
   fmt << S;
 }
 
 static std::error_code getRelocationValueString(const WasmObjectFile *Obj,
                                                 const RelocationRef &RelRef,
                                                 SmallVectorImpl<char> &Result) {
   const wasm::WasmRelocation& Rel = Obj->getWasmRelocation(RelRef);
+  symbol_iterator SI = RelRef.getSymbol();
   std::string fmtbuf;
   raw_string_ostream fmt(fmtbuf);
-  fmt << Rel.Index << (Rel.Addend < 0 ? "" : "+") << Rel.Addend;
+  Expected<StringRef> SymNameOrErr = SI->getName();
+  if (!SymNameOrErr) {
+    fmt << Rel.Index;
+  } else {
+    StringRef SymName = *SymNameOrErr;
+    Result.append(SymName.begin(), SymName.end());
+  }
+  fmt << (Rel.Addend < 0 ? "" : "+") << Rel.Addend;
   fmt.flush();
   Result.append(fmtbuf.begin(), fmtbuf.end());
   return std::error_code();
 }
 
 static std::error_code getRelocationValueString(const MachOObjectFile *Obj,
                                                 const RelocationRef &RelRef,
                                                 SmallVectorImpl<char> &Result) {