Completely rewrite ELFObjectWriter::RecordRelocation.

I started trying to fix a small issue, but this code has seen a small fix too
many.

The old code was fairly convoluted. Some of the issues it had:

* It failed to check if a symbol difference was in the some section when
  converting a relocation to pcrel.
* It failed to check if the relocation was already pcrel.
* The pcrel value computation was wrong in some cases (relocation-pc.s)
* It was missing quiet a few cases where it should not convert symbol
  relocations to section relocations, leaving the backends to patch it up.
* It would not propagate the fact that it had changed a relocation to pcrel,
  requiring a quiet nasty work around in ARM.
* It was missing comments.

llvm-svn: 205076
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
index 4e6af63..f1452ab 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
@@ -177,7 +177,7 @@
   }
 
   void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
-                  uint64_t Value) const {
+                  uint64_t Value, bool IsPCRel) const {
     unsigned NumBytes = getFixupKindInfo(Fixup.getKind()).TargetSize / 8;
     Value = adjustFixupValue(Fixup.getKind(), Value);
     if (!Value) return;           // Doesn't change encoding.
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
index 824dee0..19c717f 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
@@ -97,10 +97,6 @@
 { "fixup_arm_movw_lo16",     0,            20,  0 },
 { "fixup_t2_movt_hi16",      0,            20,  0 },
 { "fixup_t2_movw_lo16",      0,            20,  0 },
-{ "fixup_arm_movt_hi16_pcrel", 0,          20,  MCFixupKindInfo::FKF_IsPCRel },
-{ "fixup_arm_movw_lo16_pcrel", 0,          20,  MCFixupKindInfo::FKF_IsPCRel },
-{ "fixup_t2_movt_hi16_pcrel", 0,           20,  MCFixupKindInfo::FKF_IsPCRel },
-{ "fixup_t2_movw_lo16_pcrel", 0,           20,  MCFixupKindInfo::FKF_IsPCRel },
     };
     const static MCFixupKindInfo InfosBE[ARM::NumTargetFixupKinds] = {
 // This table *must* be in the order that the fixup_* kinds are defined in
@@ -138,10 +134,6 @@
 { "fixup_arm_movw_lo16",     12,           20,  0 },
 { "fixup_t2_movt_hi16",      12,           20,  0 },
 { "fixup_t2_movw_lo16",      12,           20,  0 },
-{ "fixup_arm_movt_hi16_pcrel", 12,         20,  MCFixupKindInfo::FKF_IsPCRel },
-{ "fixup_arm_movw_lo16_pcrel", 12,         20,  MCFixupKindInfo::FKF_IsPCRel },
-{ "fixup_t2_movt_hi16_pcrel", 12,          20,  MCFixupKindInfo::FKF_IsPCRel },
-{ "fixup_t2_movw_lo16_pcrel", 12,          20,  MCFixupKindInfo::FKF_IsPCRel },
     };
 
     if (Kind < FirstTargetFixupKind)
@@ -161,7 +153,7 @@
 
 
   void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
-                  uint64_t Value) const override;
+                  uint64_t Value, bool IsPCRel) const override;
 
   bool mayNeedRelaxation(const MCInst &Inst) const override;
 
@@ -315,7 +307,7 @@
 }
 
 static unsigned adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
-                                 MCContext *Ctx = NULL) {
+                                 bool IsPCRel, MCContext *Ctx) {
   unsigned Kind = Fixup.getKind();
   switch (Kind) {
   default:
@@ -325,11 +317,10 @@
   case FK_Data_4:
     return Value;
   case ARM::fixup_arm_movt_hi16:
-    Value >>= 16;
+    if (!IsPCRel)
+      Value >>= 16;
     // Fallthrough
-  case ARM::fixup_arm_movw_lo16:
-  case ARM::fixup_arm_movt_hi16_pcrel:
-  case ARM::fixup_arm_movw_lo16_pcrel: {
+  case ARM::fixup_arm_movw_lo16: {
     unsigned Hi4 = (Value & 0xF000) >> 12;
     unsigned Lo12 = Value & 0x0FFF;
     // inst{19-16} = Hi4;
@@ -338,12 +329,10 @@
     return Value;
   }
   case ARM::fixup_t2_movt_hi16:
-    Value >>= 16;
+    if (!IsPCRel)
+      Value >>= 16;
     // Fallthrough
-  case ARM::fixup_t2_movw_lo16:
-  case ARM::fixup_t2_movt_hi16_pcrel:  //FIXME: Shouldn't this be shifted like
-                                       // the other hi16 fixup?
-  case ARM::fixup_t2_movw_lo16_pcrel: {
+  case ARM::fixup_t2_movw_lo16: {
     unsigned Hi4 = (Value & 0xF000) >> 12;
     unsigned i = (Value & 0x800) >> 11;
     unsigned Mid3 = (Value & 0x700) >> 8;
@@ -629,7 +618,7 @@
   // Try to get the encoded value for the fixup as-if we're mapping it into
   // the instruction. This allows adjustFixupValue() to issue a diagnostic
   // if the value aren't invalid.
-  (void)adjustFixupValue(Fixup, Value, &Asm.getContext());
+  (void)adjustFixupValue(Fixup, Value, false, &Asm.getContext());
 }
 
 /// getFixupKindNumBytes - The number of bytes the fixup may change.
@@ -670,12 +659,8 @@
   case ARM::fixup_arm_thumb_blx:
   case ARM::fixup_arm_movt_hi16:
   case ARM::fixup_arm_movw_lo16:
-  case ARM::fixup_arm_movt_hi16_pcrel:
-  case ARM::fixup_arm_movw_lo16_pcrel:
   case ARM::fixup_t2_movt_hi16:
   case ARM::fixup_t2_movw_lo16:
-  case ARM::fixup_t2_movt_hi16_pcrel:
-  case ARM::fixup_t2_movw_lo16_pcrel:
     return 4;
   }
 }
@@ -720,21 +705,18 @@
   case ARM::fixup_arm_thumb_blx:
   case ARM::fixup_arm_movt_hi16:
   case ARM::fixup_arm_movw_lo16:
-  case ARM::fixup_arm_movt_hi16_pcrel:
-  case ARM::fixup_arm_movw_lo16_pcrel:
   case ARM::fixup_t2_movt_hi16:
   case ARM::fixup_t2_movw_lo16:
-  case ARM::fixup_t2_movt_hi16_pcrel:
-  case ARM::fixup_t2_movw_lo16_pcrel:
     // Instruction size is 4 bytes.
     return 4;
   }
 }
 
 void ARMAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
-                               unsigned DataSize, uint64_t Value) const {
+                               unsigned DataSize, uint64_t Value,
+                               bool IsPCRel) const {
   unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
-  Value = adjustFixupValue(Fixup, Value);
+  Value = adjustFixupValue(Fixup, Value, IsPCRel, nullptr);
   if (!Value) return;           // Doesn't change encoding.
 
   unsigned Offset = Fixup.getOffset();
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
index 44c5731..a4661b1 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMELFObjectWriter.cpp
@@ -36,10 +36,8 @@
 
     unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                           bool IsPCRel) const override;
-    const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
-                                   const MCValue &Target, const MCFragment &F,
-                                   const MCFixup &Fixup,
-                                   bool IsPCRel) const override;
+
+    bool needsRelocateWithSymbol(unsigned Type) const override;
   };
 }
 
@@ -50,90 +48,18 @@
 
 ARMELFObjectWriter::~ARMELFObjectWriter() {}
 
-// In ARM, _MergedGlobals and other most symbols get emitted directly.
-// I.e. not as an offset to a section symbol.
-// This code is an approximation of what ARM/gcc does.
+bool ARMELFObjectWriter::needsRelocateWithSymbol(unsigned Type) const {
+  // FIXME: This is extremelly conservative. This really needs to use a
+  // whitelist with a clear explanation for why each realocation needs to
+  // point to the symbol, not to the section.
+  switch (Type) {
+  default:
+    return true;
 
-STATISTIC(PCRelCount, "Total number of PIC Relocations");
-STATISTIC(NonPCRelCount, "Total number of non-PIC relocations");
-
-const MCSymbol *ARMELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
-                                                   const MCValue &Target,
-                                                   const MCFragment &F,
-                                                   const MCFixup &Fixup,
-                                                   bool IsPCRel) const {
-  const MCSymbol &Symbol = Target.getSymA()->getSymbol().AliasedSymbol();
-  bool EmitThisSym = false;
-
-  const MCSectionELF &Section =
-    static_cast<const MCSectionELF&>(Symbol.getSection());
-  bool InNormalSection = true;
-  unsigned RelocType = 0;
-  RelocType = GetRelocTypeInner(Target, Fixup, IsPCRel);
-  assert(!Target.getSymB() ||
-         Target.getSymB()->getKind() == MCSymbolRefExpr::VK_None);
-
-  DEBUG(
-      MCSymbolRefExpr::VariantKind Kind = Fixup.getAccessVariant();
-      dbgs() << "considering symbol "
-        << Section.getSectionName() << "/"
-        << Symbol.getName() << "/"
-        << " Rel:" << (unsigned)RelocType
-        << " Kind: " << (int)Kind
-        << " Tmp:"
-        << Symbol.isAbsolute() << "/" << Symbol.isDefined() << "/"
-        << Symbol.isVariable() << "/" << Symbol.isTemporary()
-        << " Counts:" << PCRelCount << "/" << NonPCRelCount << "\n");
-
-  if (IsPCRel) { ++PCRelCount;
-    switch (RelocType) {
-    default:
-      // Most relocation types are emitted as explicit symbols
-      InNormalSection =
-        StringSwitch<bool>(Section.getSectionName())
-        .Case(".data.rel.ro.local", false)
-        .Case(".data.rel", false)
-        .Case(".bss", false)
-        .Default(true);
-      EmitThisSym = true;
-      break;
-    case ELF::R_ARM_ABS32:
-      // But things get strange with R_ARM_ABS32
-      // In this case, most things that go in .rodata show up
-      // as section relative relocations
-      InNormalSection =
-        StringSwitch<bool>(Section.getSectionName())
-        .Case(".data.rel.ro.local", false)
-        .Case(".data.rel", false)
-        .Case(".rodata", false)
-        .Case(".bss", false)
-        .Default(true);
-      EmitThisSym = false;
-      break;
-    }
-  } else {
-    NonPCRelCount++;
-    InNormalSection =
-      StringSwitch<bool>(Section.getSectionName())
-      .Case(".data.rel.ro.local", false)
-      .Case(".rodata", false)
-      .Case(".data.rel", false)
-      .Case(".bss", false)
-      .Default(true);
-
-    switch (RelocType) {
-    default: EmitThisSym = true; break;
-    case ELF::R_ARM_ABS32: EmitThisSym = false; break;
-    case ELF::R_ARM_PREL31: EmitThisSym = false; break;
-    }
+  case ELF::R_ARM_PREL31:
+  case ELF::R_ARM_ABS32:
+    return false;
   }
-
-  if (EmitThisSym)
-    return &Symbol;
-  if (! Symbol.isTemporary() && InNormalSection) {
-    return &Symbol;
-  }
-  return NULL;
 }
 
 // Need to examine the Fixup when determining whether to 
@@ -191,19 +117,15 @@
       Type = ELF::R_ARM_THM_JUMP24;
       break;
     case ARM::fixup_arm_movt_hi16:
-    case ARM::fixup_arm_movt_hi16_pcrel:
       Type = ELF::R_ARM_MOVT_PREL;
       break;
     case ARM::fixup_arm_movw_lo16:
-    case ARM::fixup_arm_movw_lo16_pcrel:
       Type = ELF::R_ARM_MOVW_PREL_NC;
       break;
     case ARM::fixup_t2_movt_hi16:
-    case ARM::fixup_t2_movt_hi16_pcrel:
       Type = ELF::R_ARM_THM_MOVT_PREL;
       break;
     case ARM::fixup_t2_movw_lo16:
-    case ARM::fixup_t2_movw_lo16_pcrel:
       Type = ELF::R_ARM_THM_MOVW_PREL_NC;
       break;
     case ARM::fixup_arm_thumb_bl:
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMFixupKinds.h b/llvm/lib/Target/ARM/MCTargetDesc/ARMFixupKinds.h
index 0085feb..bfd9e33 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMFixupKinds.h
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMFixupKinds.h
@@ -100,15 +100,6 @@
   fixup_t2_movt_hi16, // :upper16:
   fixup_t2_movw_lo16, // :lower16:
 
-  // It is possible to create an "immediate" that happens to be pcrel.
-  // movw r0, :lower16:Foo-(Bar+8) and movt  r0, :upper16:Foo-(Bar+8)
-  // result in different reloc tags than the above two.
-  // Needed to support ELF::R_ARM_MOVT_PREL and ELF::R_ARM_MOVW_PREL_NC
-  fixup_arm_movt_hi16_pcrel, // :upper16:
-  fixup_arm_movw_lo16_pcrel, // :lower16:
-  fixup_t2_movt_hi16_pcrel, // :upper16:
-  fixup_t2_movw_lo16_pcrel, // :lower16:
-
   // Marker
   LastTargetFixupKind,
   NumTargetFixupKinds = LastTargetFixupKind - FirstTargetFixupKind
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
index 260201c..12cd336 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
@@ -975,19 +975,6 @@
   return (Reg << 8) | Imm8;
 }
 
-// FIXME: This routine assumes that a binary
-// expression will always result in a PCRel expression
-// In reality, its only true if one or more subexpressions
-// is itself a PCRel (i.e. "." in asm or some other pcrel construct)
-// but this is good enough for now.
-static bool EvaluateAsPCRel(const MCExpr *Expr) {
-  switch (Expr->getKind()) {
-  default: llvm_unreachable("Unexpected expression type");
-  case MCExpr::SymbolRef: return false;
-  case MCExpr::Binary: return true;
-  }
-}
-
 uint32_t
 ARMMCCodeEmitter::getHiLo16ImmOpValue(const MCInst &MI, unsigned OpIdx,
                                       SmallVectorImpl<MCFixup> &Fixups,
@@ -1023,24 +1010,12 @@
     switch (ARM16Expr->getKind()) {
     default: llvm_unreachable("Unsupported ARMFixup");
     case ARMMCExpr::VK_ARM_HI16:
-      if (!isTargetMachO(STI) && EvaluateAsPCRel(E))
-        Kind = MCFixupKind(isThumb2(STI)
-                           ? ARM::fixup_t2_movt_hi16_pcrel
-                           : ARM::fixup_arm_movt_hi16_pcrel);
-      else
-        Kind = MCFixupKind(isThumb2(STI)
-                           ? ARM::fixup_t2_movt_hi16
-                           : ARM::fixup_arm_movt_hi16);
+      Kind = MCFixupKind(isThumb2(STI) ? ARM::fixup_t2_movt_hi16
+                                       : ARM::fixup_arm_movt_hi16);
       break;
     case ARMMCExpr::VK_ARM_LO16:
-      if (!isTargetMachO(STI) && EvaluateAsPCRel(E))
-        Kind = MCFixupKind(isThumb2(STI)
-                           ? ARM::fixup_t2_movw_lo16_pcrel
-                           : ARM::fixup_arm_movw_lo16_pcrel);
-      else
-        Kind = MCFixupKind(isThumb2(STI)
-                           ? ARM::fixup_t2_movw_lo16
-                           : ARM::fixup_arm_movw_lo16);
+      Kind = MCFixupKind(isThumb2(STI) ? ARM::fixup_t2_movw_lo16
+                                       : ARM::fixup_arm_movw_lo16);
       break;
     }
     Fixups.push_back(MCFixup::Create(0, E, Kind, MI.getLoc()));
@@ -1050,14 +1025,8 @@
   // it's just a plain immediate expression, and those evaluate to
   // the lower 16 bits of the expression regardless of whether
   // we have a movt or a movw.
-  if (!isTargetMachO(STI) && EvaluateAsPCRel(E))
-    Kind = MCFixupKind(isThumb2(STI)
-                       ? ARM::fixup_t2_movw_lo16_pcrel
-                       : ARM::fixup_arm_movw_lo16_pcrel);
-  else
-    Kind = MCFixupKind(isThumb2(STI)
-                       ? ARM::fixup_t2_movw_lo16
-                       : ARM::fixup_arm_movw_lo16);
+  Kind = MCFixupKind(isThumb2(STI) ? ARM::fixup_t2_movw_lo16
+                                   : ARM::fixup_arm_movw_lo16);
   Fixups.push_back(MCFixup::Create(0, E, Kind, MI.getLoc()));
   return 0;
 }
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
index 4c8702c..3bf5cf1 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMMachObjectWriter.cpp
@@ -123,23 +123,19 @@
   //      0 - arm instructions
   //      1 - thumb instructions
   case ARM::fixup_arm_movt_hi16:
-  case ARM::fixup_arm_movt_hi16_pcrel:
     RelocType = unsigned(MachO::ARM_RELOC_HALF);
     Log2Size = 1;
     return true;
   case ARM::fixup_t2_movt_hi16:
-  case ARM::fixup_t2_movt_hi16_pcrel:
     RelocType = unsigned(MachO::ARM_RELOC_HALF);
     Log2Size = 3;
     return true;
 
   case ARM::fixup_arm_movw_lo16:
-  case ARM::fixup_arm_movw_lo16_pcrel:
     RelocType = unsigned(MachO::ARM_RELOC_HALF);
     Log2Size = 0;
     return true;
   case ARM::fixup_t2_movw_lo16:
-  case ARM::fixup_t2_movw_lo16_pcrel:
     RelocType = unsigned(MachO::ARM_RELOC_HALF);
     Log2Size = 2;
     return true;
@@ -206,7 +202,6 @@
   switch ((unsigned)Fixup.getKind()) {
   default: break;
   case ARM::fixup_arm_movt_hi16:
-  case ARM::fixup_arm_movt_hi16_pcrel:
     MovtBit = 1;
     // The thumb bit shouldn't be set in the 'other-half' bit of the
     // relocation, but it will be set in FixedValue if the base symbol
@@ -215,13 +210,11 @@
       FixedValue &= 0xfffffffe;
     break;
   case ARM::fixup_t2_movt_hi16:
-  case ARM::fixup_t2_movt_hi16_pcrel:
     if (A_SD->getFlags() & SF_ThumbFunc)
       FixedValue &= 0xfffffffe;
     MovtBit = 1;
     // Fallthrough
   case ARM::fixup_t2_movw_lo16:
-  case ARM::fixup_t2_movw_lo16_pcrel:
     ThumbBit = 1;
     break;
   }
@@ -465,15 +458,11 @@
     switch ((unsigned)Fixup.getKind()) {
     default: break;
     case ARM::fixup_arm_movw_lo16:
-    case ARM::fixup_arm_movw_lo16_pcrel:
     case ARM::fixup_t2_movw_lo16:
-    case ARM::fixup_t2_movw_lo16_pcrel:
       Value = (FixedValue >> 16) & 0xffff;
       break;
     case ARM::fixup_arm_movt_hi16:
-    case ARM::fixup_arm_movt_hi16_pcrel:
     case ARM::fixup_t2_movt_hi16:
-    case ARM::fixup_t2_movt_hi16_pcrel:
       Value = FixedValue & 0xffff;
       break;
     }
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
index 190aa14..541f8b6 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
@@ -116,7 +116,8 @@
 /// data fragment, at the offset specified by the fixup and following the
 /// fixup kind as appropriate.
 void MipsAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
-                                unsigned DataSize, uint64_t Value) const {
+                                unsigned DataSize, uint64_t Value,
+                                bool IsPCRel) const {
   MCFixupKind Kind = Fixup.getKind();
   Value = adjustFixupValue(Fixup, Value);
 
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.h b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.h
index e827fdf..cc5207a 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.h
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.h
@@ -40,7 +40,7 @@
   MCObjectWriter *createObjectWriter(raw_ostream &OS) const;
 
   void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
-                  uint64_t Value) const;
+                  uint64_t Value, bool IsPCRel) const;
 
   const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const;
 
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsBaseInfo.h b/llvm/lib/Target/Mips/MCTargetDesc/MipsBaseInfo.h
index 7a55efd..d2323dc 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsBaseInfo.h
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsBaseInfo.h
@@ -120,34 +120,6 @@
     FormMask = 15
   };
 }
-
-inline static std::pair<const MCSymbolRefExpr*, int64_t>
-MipsGetSymAndOffset(const MCFixup &Fixup) {
-  MCFixupKind FixupKind = Fixup.getKind();
-
-  if ((FixupKind < FirstTargetFixupKind) ||
-      (FixupKind >= MCFixupKind(Mips::LastTargetFixupKind)))
-    return std::make_pair((const MCSymbolRefExpr*)0, (int64_t)0);
-
-  const MCExpr *Expr = Fixup.getValue();
-  MCExpr::ExprKind Kind = Expr->getKind();
-
-  if (Kind == MCExpr::Binary) {
-    const MCBinaryExpr *BE = static_cast<const MCBinaryExpr*>(Expr);
-    const MCExpr *LHS = BE->getLHS();
-    const MCConstantExpr *CE = dyn_cast<MCConstantExpr>(BE->getRHS());
-
-    if ((LHS->getKind() != MCExpr::SymbolRef) || !CE)
-      return std::make_pair((const MCSymbolRefExpr*)0, (int64_t)0);
-
-    return std::make_pair(cast<MCSymbolRefExpr>(LHS), CE->getValue());
-  }
-
-  if (Kind != MCExpr::SymbolRef)
-    return std::make_pair((const MCSymbolRefExpr*)0, (int64_t)0);
-
-  return std::make_pair(cast<MCSymbolRefExpr>(Expr), 0);
-}
 }
 
 #endif
diff --git a/llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp b/llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp
index ce76336..f933962 100644
--- a/llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp
+++ b/llvm/lib/Target/Mips/MCTargetDesc/MipsELFObjectWriter.cpp
@@ -21,17 +21,6 @@
 using namespace llvm;
 
 namespace {
-  struct RelEntry {
-    RelEntry(const ELFRelocationEntry &R, const MCSymbol *S, int64_t O) :
-      Reloc(R), Sym(S), Offset(O) {}
-    ELFRelocationEntry Reloc;
-    const MCSymbol *Sym;
-    int64_t Offset;
-  };
-
-  typedef std::list<RelEntry> RelLs;
-  typedef RelLs::iterator RelLsIter;
-
   class MipsELFObjectWriter : public MCELFObjectTargetWriter {
   public:
     MipsELFObjectWriter(bool _is64Bit, uint8_t OSABI,
@@ -41,13 +30,7 @@
 
     unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                           bool IsPCRel) const override;
-    virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
-                                           const MCValue &Target,
-                                           const MCFragment &F,
-                                           const MCFixup &Fixup,
-                                           bool IsPCRel) const;
-    virtual void sortRelocs(const MCAssembler &Asm,
-                            std::vector<ELFRelocationEntry> &Relocs);
+    bool needsRelocateWithSymbol(unsigned Type) const override;
   };
 }
 
@@ -59,21 +42,6 @@
 
 MipsELFObjectWriter::~MipsELFObjectWriter() {}
 
-const MCSymbol *MipsELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
-                                                    const MCValue &Target,
-                                                    const MCFragment &F,
-                                                    const MCFixup &Fixup,
-                                                    bool IsPCRel) const {
-  assert(Target.getSymA() && "SymA cannot be 0.");
-  const MCSymbol &Sym = Target.getSymA()->getSymbol().AliasedSymbol();
-
-  if (Sym.getSection().getKind().isMergeableCString() ||
-      Sym.getSection().getKind().isMergeableConst())
-    return &Sym;
-
-  return NULL;
-}
-
 unsigned MipsELFObjectWriter::GetRelocType(const MCValue &Target,
                                            const MCFixup &Fixup,
                                            bool IsPCRel) const {
@@ -229,91 +197,23 @@
   return Type;
 }
 
-// Return true if R is either a GOT16 against a local symbol or HI16.
-static bool NeedsMatchingLo(const MCAssembler &Asm, const RelEntry &R) {
-  if (!R.Sym)
+bool
+MipsELFObjectWriter::needsRelocateWithSymbol(unsigned Type) const {
+  // FIXME: This is extremelly conservative. This really needs to use a
+  // whitelist with a clear explanation for why each realocation needs to
+  // point to the symbol, not to the section.
+  switch (Type) {
+  default:
+    return true;
+
+  case ELF::R_MIPS_26:
+  case ELF::R_MIPS_LO16:
+  case ELF::R_MIPS_HI16:
+  case ELF::R_MIPS_32:
+  case ELF::R_MIPS_64:
+  case ELF::R_MIPS_GPREL16:
     return false;
-
-  MCSymbolData &SD = Asm.getSymbolData(R.Sym->AliasedSymbol());
-
-  return ((R.Reloc.Type == ELF::R_MIPS_GOT16) && !SD.isExternal()) ||
-    (R.Reloc.Type == ELF::R_MIPS_HI16);
-}
-
-static bool HasMatchingLo(const MCAssembler &Asm, RelLsIter I, RelLsIter Last) {
-  if (I == Last)
-    return false;
-
-  RelLsIter Hi = I++;
-
-  return (I->Reloc.Type == ELF::R_MIPS_LO16) && (Hi->Sym == I->Sym) &&
-    (Hi->Offset == I->Offset);
-}
-
-static bool HasSameSymbol(const RelEntry &R0, const RelEntry &R1) {
-  return R0.Sym == R1.Sym;
-}
-
-static int CompareOffset(const RelEntry &R0, const RelEntry &R1) {
-  return (R0.Offset > R1.Offset) ? 1 : ((R0.Offset == R1.Offset) ? 0 : -1);
-}
-
-void MipsELFObjectWriter::sortRelocs(const MCAssembler &Asm,
-                                     std::vector<ELFRelocationEntry> &Relocs) {
-  // Call the default function first. Relocations are sorted in descending
-  // order of r_offset.
-  MCELFObjectTargetWriter::sortRelocs(Asm, Relocs);
-
-  RelLs RelocLs;
-  std::vector<RelLsIter> Unmatched;
-
-  // Fill RelocLs. Traverse Relocs backwards so that relocations in RelocLs
-  // are in ascending order of r_offset.
-  for (std::vector<ELFRelocationEntry>::reverse_iterator R = Relocs.rbegin();
-       R != Relocs.rend(); ++R) {
-     std::pair<const MCSymbolRefExpr*, int64_t> P =
-       MipsGetSymAndOffset(*R->Fixup);
-     RelocLs.push_back(RelEntry(*R, P.first ? &P.first->getSymbol() : 0,
-                                P.second));
   }
-
-  // Get list of unmatched HI16 and GOT16.
-  for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R)
-    if (NeedsMatchingLo(Asm, *R) && !HasMatchingLo(Asm, R, --RelocLs.end()))
-      Unmatched.push_back(R);
-
-  // Insert unmatched HI16 and GOT16 immediately before their matching LO16.
-  for (std::vector<RelLsIter>::iterator U = Unmatched.begin();
-       U != Unmatched.end(); ++U) {
-    RelLsIter LoPos = RelocLs.end(), HiPos = *U;
-    bool MatchedLo = false;
-
-    for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R) {
-      if ((R->Reloc.Type == ELF::R_MIPS_LO16) && HasSameSymbol(*HiPos, *R) &&
-          (CompareOffset(*R, *HiPos) >= 0) &&
-          ((LoPos == RelocLs.end()) || ((CompareOffset(*R, *LoPos) < 0)) ||
-           (!MatchedLo && !CompareOffset(*R, *LoPos))))
-        LoPos = R;
-
-      MatchedLo = NeedsMatchingLo(Asm, *R) &&
-        HasMatchingLo(Asm, R, --RelocLs.end());
-    }
-
-    // If a matching LoPos was found, move HiPos and insert it before LoPos.
-    // Make the offsets of HiPos and LoPos match.
-    if (LoPos != RelocLs.end()) {
-      HiPos->Offset = LoPos->Offset;
-      RelocLs.insert(LoPos, *HiPos);
-      RelocLs.erase(HiPos);
-    }
-  }
-
-  // Put the sorted list back in reverse order.
-  assert(Relocs.size() == RelocLs.size());
-  unsigned I = RelocLs.size();
-
-  for (RelLsIter R = RelocLs.begin(); R != RelocLs.end(); ++R)
-    Relocs[--I] = R->Reloc;
 }
 
 MCObjectWriter *llvm::createMipsELFObjectWriter(raw_ostream &OS,
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
index f99bc7e..f7309bb 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
@@ -110,7 +110,7 @@
   }
 
   void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
-                  uint64_t Value) const {
+                  uint64_t Value, bool IsPCRel) const {
     Value = adjustFixupValue(Fixup.getKind(), Value);
     if (!Value) return;           // Doesn't change encoding.
 
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
index b5c5e19..d19f6a0 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFObjectWriter.cpp
@@ -30,14 +30,6 @@
                                        bool IsPCRel) const;
     unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                           bool IsPCRel) const override;
-    virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
-                                           const MCValue &Target,
-                                           const MCFragment &F,
-                                           const MCFixup &Fixup,
-                                           bool IsPCRel) const;
-    virtual const MCSymbol *undefinedExplicitRelSym(const MCValue &Target,
-                                                    const MCFixup &Fixup,
-                                                    bool IsPCRel) const;
   };
 }
 
@@ -386,54 +378,6 @@
   return getRelocTypeInner(Target, Fixup, IsPCRel);
 }
 
-const MCSymbol *PPCELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
-                                                   const MCValue &Target,
-                                                   const MCFragment &F,
-                                                   const MCFixup &Fixup,
-                                                   bool IsPCRel) const {
-  assert(Target.getSymA() && "SymA cannot be 0");
-  MCSymbolRefExpr::VariantKind Modifier = Fixup.getAccessVariant();
-
-  bool EmitThisSym;
-  switch (Modifier) {
-  // GOT references always need a relocation, even if the
-  // target symbol is local.
-  case MCSymbolRefExpr::VK_GOT:
-  case MCSymbolRefExpr::VK_PPC_GOT_LO:
-  case MCSymbolRefExpr::VK_PPC_GOT_HI:
-  case MCSymbolRefExpr::VK_PPC_GOT_HA:
-    EmitThisSym = true;
-    break;
-  default:
-    EmitThisSym = false;
-    break;
-  } 
-
-  if (EmitThisSym)
-    return &Target.getSymA()->getSymbol().AliasedSymbol();
-  return NULL;
-}
-
-const MCSymbol *PPCELFObjectWriter::undefinedExplicitRelSym(const MCValue &Target,
-                                                            const MCFixup &Fixup,
-                                                            bool IsPCRel) const {
-  assert(Target.getSymA() && "SymA cannot be 0");
-  const MCSymbol &Symbol = Target.getSymA()->getSymbol().AliasedSymbol();
-
-  unsigned RelocType = getRelocTypeInner(Target, Fixup, IsPCRel);
-
-  // The .odp creation emits a relocation against the symbol ".TOC." which
-  // create a R_PPC64_TOC relocation. However the relocation symbol name
-  // in final object creation should be NULL, since the symbol does not
-  // really exist, it is just the reference to TOC base for the current
-  // object file.
-  bool EmitThisSym = RelocType != ELF::R_PPC64_TOC;
-
-  if (EmitThisSym && !Symbol.isTemporary())
-    return &Symbol;
-  return NULL;
-}
-
 MCObjectWriter *llvm::createPPCELFObjectWriter(raw_ostream &OS,
                                                bool Is64Bit,
                                                bool IsLittleEndian,
diff --git a/llvm/lib/Target/R600/MCTargetDesc/AMDGPUAsmBackend.cpp b/llvm/lib/Target/R600/MCTargetDesc/AMDGPUAsmBackend.cpp
index 29d0acf..a6bb59f 100644
--- a/llvm/lib/Target/R600/MCTargetDesc/AMDGPUAsmBackend.cpp
+++ b/llvm/lib/Target/R600/MCTargetDesc/AMDGPUAsmBackend.cpp
@@ -27,11 +27,10 @@
                                         const MCAsmLayout &Layout) {
     //XXX: Implement if necessary.
   }
-  virtual void RecordRelocation(const MCAssembler &Asm,
-                                const MCAsmLayout &Layout,
-                                const MCFragment *Fragment,
-                                const MCFixup &Fixup,
-                                MCValue Target, uint64_t &FixedValue) {
+  void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
+                        const MCFragment *Fragment, const MCFixup &Fixup,
+                        MCValue Target, bool &IsPCRel,
+                        uint64_t &FixedValue) override {
     assert(!"Not implemented");
   }
 
@@ -46,7 +45,7 @@
 
   virtual unsigned getNumFixupKinds() const { return 0; };
   virtual void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
-                          uint64_t Value) const;
+                          uint64_t Value, bool IsPCRel) const;
   virtual bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
                                     const MCRelaxableFragment *DF,
                                     const MCAsmLayout &Layout) const {
@@ -71,7 +70,8 @@
 }
 
 void AMDGPUAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
-                                  unsigned DataSize, uint64_t Value) const {
+                                  unsigned DataSize, uint64_t Value,
+                                  bool IsPCRel) const {
 
   uint16_t *Dst = (uint16_t*)(Data + Fixup.getOffset());
   assert(Fixup.getKind() == FK_PCRel_4);
diff --git a/llvm/lib/Target/Sparc/MCTargetDesc/SparcAsmBackend.cpp b/llvm/lib/Target/Sparc/MCTargetDesc/SparcAsmBackend.cpp
index bf39515..39c9996 100644
--- a/llvm/lib/Target/Sparc/MCTargetDesc/SparcAsmBackend.cpp
+++ b/llvm/lib/Target/Sparc/MCTargetDesc/SparcAsmBackend.cpp
@@ -229,7 +229,7 @@
       SparcAsmBackend(T), OSType(OSType) { }
 
     void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
-                    uint64_t Value) const {
+                    uint64_t Value, bool IsPCRel) const {
 
       Value = adjustFixupValue(Fixup.getKind(), Value);
       if (!Value) return;           // Doesn't change encoding.
diff --git a/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp b/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp
index bb93b90..5ba82f1 100644
--- a/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp
+++ b/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp
@@ -30,12 +30,6 @@
   protected:
     unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                           bool IsPCRel) const override;
-
-    virtual const MCSymbol *ExplicitRelSym(const MCAssembler &Asm,
-                                           const MCValue &Target,
-                                           const MCFragment &F,
-                                           const MCFixup &Fixup,
-                                           bool IsPCRel) const;
   };
 }
 
@@ -110,23 +104,6 @@
   return ELF::R_SPARC_NONE;
 }
 
-const MCSymbol *SparcELFObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
-                                                     const MCValue &Target,
-                                                     const MCFragment &F,
-                                                     const MCFixup &Fixup,
-                                                     bool IsPCRel) const {
-
-  if (!Target.getSymA())
-    return NULL;
-  switch((unsigned)Fixup.getKind()) {
-  default: break;
-  case Sparc::fixup_sparc_got22:
-  case Sparc::fixup_sparc_got10:
-    return &Target.getSymA()->getSymbol().AliasedSymbol();
-  }
-  return NULL;
-}
-
 MCObjectWriter *llvm::createSparcELFObjectWriter(raw_ostream &OS,
                                                  bool Is64Bit,
                                                  uint8_t OSABI) {
diff --git a/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp b/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp
index 047a976..6e7268d 100644
--- a/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp
+++ b/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp
@@ -48,7 +48,7 @@
   }
   const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const override;
   void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
-                  uint64_t Value) const override;
+                  uint64_t Value, bool IsPCRel) const override;
   bool mayNeedRelaxation(const MCInst &Inst) const override {
     return false;
   }
@@ -85,7 +85,8 @@
 }
 
 void SystemZMCAsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
-                                     unsigned DataSize, uint64_t Value) const {
+                                     unsigned DataSize, uint64_t Value,
+                                     bool IsPCRel) const {
   MCFixupKind Kind = Fixup.getKind();
   unsigned Offset = Fixup.getOffset();
   unsigned Size = (getFixupKindInfo(Kind).TargetSize + 7) / 8;
diff --git a/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCObjectWriter.cpp b/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCObjectWriter.cpp
index 76e1d24..54c6987 100644
--- a/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCObjectWriter.cpp
+++ b/llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCObjectWriter.cpp
@@ -26,9 +26,6 @@
   // Override MCELFObjectTargetWriter.
   unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
                         bool IsPCRel) const override;
-  const MCSymbol *ExplicitRelSym(const MCAssembler &Asm, const MCValue &Target,
-                                 const MCFragment &F, const MCFixup &Fixup,
-                                 bool IsPCRel) const override;
 };
 } // end anonymous namespace
 
@@ -111,21 +108,6 @@
   }
 }
 
-const MCSymbol *SystemZObjectWriter::ExplicitRelSym(const MCAssembler &Asm,
-                                                    const MCValue &Target,
-                                                    const MCFragment &F,
-                                                    const MCFixup &Fixup,
-                                                    bool IsPCRel) const {
-  // The addend in a PC-relative R_390_* relocation is always applied to
-  // the PC-relative part of the address.  If some kind of indirection
-  // is applied to the symbol first, we can't use an addend there too.
-  if (!Target.isAbsolute() &&
-      Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None &&
-      IsPCRel)
-    return &Target.getSymA()->getSymbol().AliasedSymbol();
-  return NULL;
-}
-
 MCObjectWriter *llvm::createSystemZObjectWriter(raw_ostream &OS,
                                                 uint8_t OSABI) {
   MCELFObjectTargetWriter *MOTW = new SystemZObjectWriter(OSABI);
diff --git a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
index 3063ec6..23763f7 100644
--- a/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
+++ b/llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
@@ -100,7 +100,7 @@
   }
 
   void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
-                  uint64_t Value) const override {
+                  uint64_t Value, bool IsPCRel) const override {
     unsigned Size = 1 << getFixupKindLog2Size(Fixup.getKind());
 
     assert(Fixup.getOffset() + Size <= DataSize &&