Cleanup relocation sorting for ELF.

We want the order to be deterministic on all platforms. NAKAMURA Takumi
fixed that in r181864. This patch is just two small cleanups:

* Move the function to the cpp file. It is only passed to array_pod_sort.
* Remove the ppc implementation which is now redundant

llvm-svn: 181910

include/llvm/MC/MCELFObjectWriter.h

@@ -42,18 +42,6 @@ struct ELFRelocationEntry {
                      const MCSymbol *Sym, uint64_t Addend, const MCFixup &Fixup)
     : r_offset(RelocOffset), Index(Idx), Type(RelType), Symbol(Sym),
       r_addend(Addend), Fixup(&Fixup) {}
-
-  // Support lexicographic sorting.
-  bool operator<(const ELFRelocationEntry &RE) const {
-    if (RE.r_offset != r_offset)
-      return RE.r_offset < r_offset;
-    if (Type != RE.Type)
-      return Type < RE.Type;
-    if (Index != RE.Index)
-      return Index < RE.Index;
-    llvm_unreachable("ELFRelocs might be unstable!");
-    return 0;
-  }
 };
 
 class MCELFObjectTargetWriter {

lib/MC/MCELFObjectTargetWriter.cpp

@@ -39,9 +39,23 @@ const MCSymbol *MCELFObjectTargetWriter::undefinedExplicitRelSym(const MCValue &
   return &Symbol.AliasedSymbol();
 }
 
+// ELF doesn't require relocations to be in any order. We sort by the r_offset,
+// just to match gnu as for easier comparison. The use type and index is an
+// arbitrary way of making the sort deterministic.
+static int cmpRel(const void *AP, const void *BP) {
+  const ELFRelocationEntry &A = *(const ELFRelocationEntry *)AP;
+  const ELFRelocationEntry &B = *(const ELFRelocationEntry *)BP;
+  if (A.r_offset != B.r_offset)
+    return B.r_offset - A.r_offset;
+  if (B.Type != A.Type)
+    return A.Type - B.Type;
+  if (B.Index != A.Index)
+    return B.Index - A.Index;
+  llvm_unreachable("ELFRelocs might be unstable!");
+}
+
 void
 MCELFObjectTargetWriter::sortRelocs(const MCAssembler &Asm,
                                     std::vector<ELFRelocationEntry> &Relocs) {
-  // Sort by the r_offset, just like gnu as does.
+  array_pod_sort(Relocs.begin(), Relocs.end(), cmpRel);
-  array_pod_sort(Relocs.begin(), Relocs.end());
 }

lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp

@@ -33,25 +33,9 @@ namespace {
     virtual const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
                                                     const MCFixup &Fixup,
                                                     bool IsPCRel) const;
-
-    virtual void sortRelocs(const MCAssembler &Asm,
-                            std::vector<ELFRelocationEntry> &Relocs);
-  };
-
-  class PPCELFRelocationEntry : public ELFRelocationEntry {
-  public:
-    PPCELFRelocationEntry(const ELFRelocationEntry &RE);
-    bool operator<(const PPCELFRelocationEntry &RE) const {
-      return (RE.r_offset < r_offset ||
-              (RE.r_offset == r_offset && RE.Type > Type));
-    }
   };
 }
 
-PPCELFRelocationEntry::PPCELFRelocationEntry(const ELFRelocationEntry &RE)
-  : ELFRelocationEntry(RE.r_offset, RE.Index, RE.Type, RE.Symbol,
-                       RE.r_addend, *RE.Fixup) {}
-
 PPCELFObjectWriter::PPCELFObjectWriter(bool Is64Bit, uint8_t OSABI)
   : MCELFObjectTargetWriter(Is64Bit, OSABI,
                             Is64Bit ?  ELF::EM_PPC64 : ELF::EM_PPC,
@@ -239,34 +223,6 @@ const MCSymbol *PPCELFObjectWriter::undefinedExplicitRelSym(const MCValue &Targe
   return NULL;
 }
 
-// The standard sorter only sorts on the r_offset field, but PowerPC can
-// have multiple relocations at the same offset.  Sort secondarily on the
-// relocation type to avoid nondeterminism.
-void PPCELFObjectWriter::sortRelocs(const MCAssembler &Asm,
-                                    std::vector<ELFRelocationEntry> &Relocs) {
-
-  // Copy to a temporary vector of relocation entries having a different
-  // sort function.
-  std::vector<PPCELFRelocationEntry> TmpRelocs;
-  
-  for (std::vector<ELFRelocationEntry>::iterator R = Relocs.begin();
-       R != Relocs.end(); ++R) {
-    TmpRelocs.push_back(PPCELFRelocationEntry(*R));
-  }
-
-  // Sort in place by ascending r_offset and descending r_type.
-  array_pod_sort(TmpRelocs.begin(), TmpRelocs.end());
-
-  // Copy back to the original vector.
-  unsigned I = 0;
-  for (std::vector<PPCELFRelocationEntry>::iterator R = TmpRelocs.begin();
-       R != TmpRelocs.end(); ++R, ++I) {
-    Relocs[I] = ELFRelocationEntry(R->r_offset, R->Index, R->Type,
-                                   R->Symbol, R->r_addend, *R->Fixup);
-  }
-}
-
-
 MCObjectWriter *llvm::createPPCELFObjectWriter(raw_ostream &OS,
                                                bool Is64Bit,
                                                uint8_t OSABI) {