[llvm-readobj] [COFF] Print the symbol index for relocations

There can be multiple local symbols with the same name (for e.g.
comdat sections), and thus the symbol name itself isn't enough
to disambiguate symbols.

Differential Revision: https://reviews.llvm.org/D56140

llvm-svn: 350288

llvm/include/llvm/Object/COFF.h

@@ -1022,6 +1022,8 @@ public:
 
   ArrayRef<uint8_t> getSymbolAuxData(COFFSymbolRef Symbol) const;
 
+  uint32_t getSymbolIndex(COFFSymbolRef Symbol) const;
+
   size_t getSymbolTableEntrySize() const {
     if (COFFHeader)
       return sizeof(coff_symbol16);

llvm/lib/Object/COFFObjectFile.cpp

@@ -1065,6 +1065,16 @@ COFFObjectFile::getSymbolAuxData(COFFSymbolRef Symbol) const {
   return makeArrayRef(Aux, Symbol.getNumberOfAuxSymbols() * SymbolSize);
 }
 
+uint32_t COFFObjectFile::getSymbolIndex(COFFSymbolRef Symbol) const {
+  uintptr_t Offset =
+      reinterpret_cast<uintptr_t>(Symbol.getRawPtr()) - getSymbolTable();
+  assert(Offset % getSymbolTableEntrySize() == 0 &&
+         "Symbol did not point to the beginning of a symbol");
+  size_t Index = Offset / getSymbolTableEntrySize();
+  assert(Index < getNumberOfSymbols());
+  return Index;
+}
+
 std::error_code COFFObjectFile::getSectionName(const coff_section *Sec,
                                                StringRef &Res) const {
   StringRef Name;

llvm/test/MC/COFF/cross-section-relative.s

@@ -87,21 +87,25 @@ t6:
 // READOBJ-NEXT:      Offset: 0x0
 // READOBJ-NEXT:      Type: IMAGE_REL_AMD64_REL32 (4)
 // READOBJ-NEXT:      Symbol: g3
+// READOBJ-NEXT:      SymbolIndex: 12
 // READOBJ-NEXT:    }
 // READOBJ-NEXT:    Relocation {
 // READOBJ-NEXT:      Offset: 0x4
 // READOBJ-NEXT:      Type: IMAGE_REL_AMD64_ADDR32NB (3)
 // READOBJ-NEXT:      Symbol: g3
+// READOBJ-NEXT:      SymbolIndex: 12
 // READOBJ-NEXT:    }
 // READOBJ-NEXT:    Relocation {
 // READOBJ-NEXT:      Offset: 0x20
 // READOBJ-NEXT:      Type: IMAGE_REL_AMD64_REL32 (4)
 // READOBJ-NEXT:      Symbol: g3
+// READOBJ-NEXT:      SymbolIndex: 12
 // READOBJ-NEXT:    }
 // READOBJ-NEXT:    Relocation {
 // READOBJ-NEXT:      Offset: 0x28
 // READOBJ-NEXT:      Type: IMAGE_REL_AMD64_REL32 (4)
 // READOBJ-NEXT:      Symbol: foobar
+// READOBJ-NEXT:      SymbolIndex: 20
 // READOBJ-NEXT:    }
 // READOBJ-NEXT:  }
 // READOBJ-NEXT:]

llvm/test/Object/yaml2obj-readobj.test

@@ -13,16 +13,19 @@ RUN:   | FileCheck %s --check-prefix COFF-I386
 // COFF-I386-NEXT:       Offset: 0xE
 // COFF-I386-NEXT:       Type: IMAGE_REL_I386_DIR32 (6)
 // COFF-I386-NEXT:       Symbol: L_.str
+// COFF-I386-NEXT:       SymbolIndex: 5
 // COFF-I386-NEXT:     }
 // COFF-I386-NEXT:     Relocation {
 // COFF-I386-NEXT:       Offset: 0x13
 // COFF-I386-NEXT:       Type: IMAGE_REL_I386_REL32 (20)
 // COFF-I386-NEXT:       Symbol: _puts
+// COFF-I386-NEXT:       SymbolIndex: 6
 // COFF-I386-NEXT:     }
 // COFF-I386-NEXT:     Relocation {
 // COFF-I386-NEXT:       Offset: 0x18
 // COFF-I386-NEXT:       Type: IMAGE_REL_I386_REL32 (20)
 // COFF-I386-NEXT:       Symbol: _SomeOtherFunction
+// COFF-I386-NEXT:       SymbolIndex: 7
 // COFF-I386-NEXT:     }
 // COFF-I386-NEXT:   }
 // COFF-I386-NEXT: ]

llvm/test/tools/llvm-readobj/relocations.test

@@ -21,9 +21,9 @@ RUN:   | FileCheck %s -check-prefix WASM
 
 COFF:      Relocations [
 COFF-NEXT:   Section (1) .text {
-COFF-NEXT:     0x4 IMAGE_REL_I386_DIR32 .data
-COFF-NEXT:     0x9 IMAGE_REL_I386_REL32 _puts
-COFF-NEXT:     0xE IMAGE_REL_I386_REL32 _SomeOtherFunction
+COFF-NEXT:     0x4 IMAGE_REL_I386_DIR32 .data (4)
+COFF-NEXT:     0x9 IMAGE_REL_I386_REL32 _puts (7)
+COFF-NEXT:     0xE IMAGE_REL_I386_REL32 _SomeOtherFunction (8)
 COFF-NEXT:   }
 COFF-NEXT: ]
 

llvm/tools/llvm-readobj/COFFDumper.cpp

@@ -1365,10 +1365,12 @@ void COFFDumper::printRelocation(const SectionRef &Section,
   StringRef SymbolName;
   Reloc.getTypeName(RelocName);
   symbol_iterator Symbol = Reloc.getSymbol();
+  int64_t SymbolIndex = -1;
   if (Symbol != Obj->symbol_end()) {
     Expected<StringRef> SymbolNameOrErr = Symbol->getName();
     error(errorToErrorCode(SymbolNameOrErr.takeError()));
     SymbolName = *SymbolNameOrErr;
+    SymbolIndex = Obj->getSymbolIndex(Obj->getCOFFSymbol(*Symbol));
   }
 
   if (opts::ExpandRelocs) {
@@ -1376,11 +1378,13 @@ void COFFDumper::printRelocation(const SectionRef &Section,
     W.printHex("Offset", Offset);
     W.printNumber("Type", RelocName, RelocType);
     W.printString("Symbol", SymbolName.empty() ? "-" : SymbolName);
+    W.printNumber("SymbolIndex", SymbolIndex);
   } else {
     raw_ostream& OS = W.startLine();
     OS << W.hex(Offset)
        << " " << RelocName
        << " " << (SymbolName.empty() ? "-" : SymbolName)
+       << " (" << SymbolIndex << ")"
        << "\n";
   }
 }