Add support for the notion of "hidden" relocations. On MachO, these are relocation entries that are used as additional information for other, real relocations, rather than being relocations themselves.

I'm not familiar enough with ELF or COFF to know if they should have any relocations marked hidden.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@142961 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Object/MachO.h

@@ -88,6 +88,7 @@ protected:
                                                  int64_t &Res) const;
   virtual error_code getRelocationValueString(DataRefImpl Rel,
                                            SmallVectorImpl<char> &Result) const;
+  virtual error_code getRelocationHidden(DataRefImpl Rel, bool &Result) const;
 
 private:
   MachOObject *MachOObj;

include/llvm/Object/ObjectFile.h

@@ -101,6 +101,11 @@ public:
   error_code getSymbol(SymbolRef &Result) const;
   error_code getType(uint32_t &Result) const;
 
+  /// @brief Indicates whether this relocation should hidden when listing
+  /// relocations, usually because it is the trailing part of a multipart
+  /// relocation that will be printed as part of the leading relocation.
+  error_code getHidden(bool &Result) const;
+
   /// @brief Get a string that represents the type of this relocation.
   ///
   /// This is for display purposes only.
@@ -286,6 +291,10 @@ protected:
                                                  int64_t &Res) const = 0;
   virtual error_code getRelocationValueString(DataRefImpl Rel,
                                        SmallVectorImpl<char> &Result) const = 0;
+  virtual error_code getRelocationHidden(DataRefImpl Rel, bool &Result) const {
+    Result = false;
+    return object_error::success;
+  }
 
 public:
 
@@ -483,6 +492,10 @@ inline error_code RelocationRef::getValueString(SmallVectorImpl<char> &Result)
   return OwningObject->getRelocationValueString(RelocationPimpl, Result);
 }
 
+inline error_code RelocationRef::getHidden(bool &Result) const {
+  return OwningObject->getRelocationHidden(RelocationPimpl, Result);
+}
+
 } // end namespace object
 } // end namespace llvm
 

lib/Object/MachOObjectFile.cpp

@@ -952,6 +952,38 @@ error_code MachOObjectFile::getRelocationValueString(DataRefImpl Rel,
   return object_error::success;
 }
 
+error_code MachOObjectFile::getRelocationHidden(DataRefImpl Rel,
+                                                bool &Result) const {
+  InMemoryStruct<macho::RelocationEntry> RE;
+  getRelocation(Rel, RE);
+
+  unsigned Type = (RE->Word1 >> 28) & 0xF;
+  unsigned Arch = getArch();
+
+  Result = false;
+
+  // On arches that use the generic relocations, GENERIC_RELOC_PAIR
+  // is always hidden.
+  if (Arch == Triple::x86 || Arch == Triple::arm) {
+    if (Type == 1) Result = true;
+  } else if (Arch == Triple::x86_64) {
+    // On x86_64, X86_64_RELOC_UNSIGNED is hidden only when it follows
+    // an X864_64_RELOC_SUBTRACTOR.
+    if (Type == 0 && Rel.d.a > 0) {
+      DataRefImpl RelPrev = Rel;
+      RelPrev.d.a--;
+      InMemoryStruct<macho::RelocationEntry> REPrev;
+      getRelocation(RelPrev, REPrev);
+
+      unsigned PrevType = (REPrev->Word1 >> 28) & 0xF;
+
+      if (PrevType == 5) Result = true;
+    }
+  }
+
+  return object_error::success;
+}
+
 /*===-- Miscellaneous -----------------------------------------------------===*/
 
 uint8_t MachOObjectFile::getBytesInAddress() const {

tools/llvm-objdump/llvm-objdump.cpp

@@ -301,9 +301,15 @@ static void DisassembleObject(const ObjectFile *Obj, bool InlineRelocs) {
 
         // Print relocation for instruction.
         while (rel_cur != rel_end) {
+          bool hidden = false;
           uint64_t addr;
           SmallString<16> name;
           SmallString<32> val;
+
+          // If this relocation is hidden, skip it.
+          if (error(rel_cur->getHidden(hidden))) goto skip_print_rel;
+          if (hidden) goto skip_print_rel;
+
           if (error(rel_cur->getAddress(addr))) goto skip_print_rel;
           // Stop when rel_cur's address is past the current instruction.
           if (addr >= Index + Size) break;
@@ -336,9 +342,12 @@ static void PrintRelocations(const ObjectFile *o) {
                              ri != re; ri.increment(ec)) {
       if (error(ec)) return;
 
+      bool hidden;
       uint64_t address;
       SmallString<32> relocname;
       SmallString<32> valuestr;
+      if (error(ri->getHidden(hidden))) continue;
+      if (hidden) continue;
       if (error(ri->getTypeName(relocname))) continue;
       if (error(ri->getAddress(address))) continue;
       if (error(ri->getValueString(valuestr))) continue;