diff --git a/include/llvm/MC/MCInstrDesc.h b/include/llvm/MC/MCInstrDesc.h
index c6165d6ffa5..e55a9d454c9 100644
--- a/include/llvm/MC/MCInstrDesc.h
+++ b/include/llvm/MC/MCInstrDesc.h
@@ -16,6 +16,8 @@
 #define LLVM_MC_MCINSTRDESC_H
 
 #include "llvm/Support/DataTypes.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCInst.h"
 
 namespace llvm {
 
@@ -258,6 +260,17 @@ public:
     return isBranch() & isBarrier() & !isIndirectBranch();
   }
 
+  /// Return true if this is a branch or an instruction which directly
+  /// writes to the program counter. Considered 'may' affect rather than
+  /// 'does' affect as things like predication are not taken into account.
+  bool mayAffectControlFlow(const MCInst &MI, const MCRegisterInfo &RI) const {
+    if (isBranch() || isCall() || isReturn() || isIndirectBranch())
+      return true;
+    unsigned PC = RI.getProgramCounter();
+    if (PC == 0) return false;
+    return hasDefOfPhysReg(MI, PC, RI);
+  }
+
   /// isPredicable - Return true if this instruction has a predicate operand
   /// that controls execution. It may be set to 'always', or may be set to other
   /// values. There are various methods in TargetInstrInfo that can be used to
@@ -502,13 +515,26 @@ public:
 
   /// hasImplicitDefOfPhysReg - Return true if this instruction implicitly
   /// defines the specified physical register.
-  bool hasImplicitDefOfPhysReg(unsigned Reg) const {
+  bool hasImplicitDefOfPhysReg(unsigned Reg,
+                               const MCRegisterInfo *MRI = 0) const {
     if (const uint16_t *ImpDefs = ImplicitDefs)
       for (; *ImpDefs; ++ImpDefs)
-        if (*ImpDefs == Reg) return true;
+        if (*ImpDefs == Reg || (MRI && MRI->isSubRegister(Reg, *ImpDefs)))
+            return true;
     return false;
   }
 
+  /// Return true if this instruction defines the specified physical
+  /// register, either explicitly or implicitly.
+  bool hasDefOfPhysReg(const MCInst &MI, unsigned Reg,
+                       const MCRegisterInfo &RI) const {
+    for (int i = 0, e = NumDefs; i != e; ++i)
+      if (MI.getOperand(i).isReg() &&
+          RI.isSubRegisterEq(Reg, MI.getOperand(i).getReg()))
+        return true;
+    return hasImplicitDefOfPhysReg(Reg, &RI);
+  }
+
   /// getSchedClass - Return the scheduling class for this instruction.  The
   /// scheduling class is an index into the InstrItineraryData table.  This
   /// returns zero if there is no known scheduling information for the
diff --git a/include/llvm/MC/MCRegisterInfo.h b/include/llvm/MC/MCRegisterInfo.h
index c793533fab6..b76c3b1eabc 100644
--- a/include/llvm/MC/MCRegisterInfo.h
+++ b/include/llvm/MC/MCRegisterInfo.h
@@ -152,6 +152,7 @@ private:
   const MCRegisterDesc *Desc;                 // Pointer to the descriptor array
   unsigned NumRegs;                           // Number of entries in the array
   unsigned RAReg;                             // Return address register
+  unsigned PCReg;                             // Program counter register
   const MCRegisterClass *Classes;             // Pointer to the regclass array
   unsigned NumClasses;                        // Number of entries in the array
   unsigned NumRegUnits;                       // Number of regunits.
@@ -232,6 +233,7 @@ public:
   /// InitMCRegisterInfo - Initialize MCRegisterInfo, called by TableGen
   /// auto-generated routines. *DO NOT USE*.
   void InitMCRegisterInfo(const MCRegisterDesc *D, unsigned NR, unsigned RA,
+                          unsigned PC,
                           const MCRegisterClass *C, unsigned NC,
                           const uint16_t (*RURoots)[2],
                           unsigned NRU,
@@ -243,6 +245,7 @@ public:
     Desc = D;
     NumRegs = NR;
     RAReg = RA;
+    PCReg = PC;
     Classes = C;
     DiffLists = DL;
     RegStrings = Strings;
@@ -297,6 +300,11 @@ public:
     return RAReg;
   }
 
+  /// Return the register which is the program counter.
+  unsigned getProgramCounter() const {
+    return PCReg;
+  }
+
   const MCRegisterDesc &operator[](unsigned RegNo) const {
     assert(RegNo < NumRegs &&
            "Attempting to access record for invalid register number!");
diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index e0991ef9eb8..42742bf3b66 100644
--- a/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -45,7 +45,7 @@ using namespace llvm;
 
 ARMBaseRegisterInfo::ARMBaseRegisterInfo(const ARMBaseInstrInfo &tii,
                                          const ARMSubtarget &sti)
-  : ARMGenRegisterInfo(ARM::LR), TII(tii), STI(sti),
+  : ARMGenRegisterInfo(ARM::LR, 0, 0, ARM::PC), TII(tii), STI(sti),
     FramePtr((STI.isTargetDarwin() || STI.isThumb()) ? ARM::R7 : ARM::R11),
     BasePtr(ARM::R6) {
 }
diff --git a/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp b/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
index c4dacfe8ce5..372f58c1906 100644
--- a/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
+++ b/lib/Target/ARM/MCTargetDesc/ARMMCTargetDesc.cpp
@@ -146,7 +146,7 @@ static MCInstrInfo *createARMMCInstrInfo() {
 
 static MCRegisterInfo *createARMMCRegisterInfo(StringRef Triple) {
   MCRegisterInfo *X = new MCRegisterInfo();
-  InitARMMCRegisterInfo(X, ARM::LR);
+  InitARMMCRegisterInfo(X, ARM::LR, 0, 0, ARM::PC);
   return X;
 }
 
diff --git a/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp b/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
index f66b203f0d5..5e84530cd72 100644
--- a/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
+++ b/lib/Target/X86/MCTargetDesc/X86MCTargetDesc.cpp
@@ -257,7 +257,8 @@ static MCRegisterInfo *createX86MCRegisterInfo(StringRef TT) {
   MCRegisterInfo *X = new MCRegisterInfo();
   InitX86MCRegisterInfo(X, RA,
                         X86_MC::getDwarfRegFlavour(TT, false),
-                        X86_MC::getDwarfRegFlavour(TT, true));
+                        X86_MC::getDwarfRegFlavour(TT, true),
+                        RA);
   X86_MC::InitLLVM2SEHRegisterMapping(X);
   return X;
 }
diff --git a/lib/Target/X86/X86RegisterInfo.cpp b/lib/Target/X86/X86RegisterInfo.cpp
index 1934b28fede..6b36101a12e 100644
--- a/lib/Target/X86/X86RegisterInfo.cpp
+++ b/lib/Target/X86/X86RegisterInfo.cpp
@@ -56,10 +56,12 @@ EnableBasePointer("x86-use-base-pointer", cl::Hidden, cl::init(true),
 
 X86RegisterInfo::X86RegisterInfo(X86TargetMachine &tm,
                                  const TargetInstrInfo &tii)
-  : X86GenRegisterInfo(tm.getSubtarget<X86Subtarget>().is64Bit()
-                         ? X86::RIP : X86::EIP,
+  : X86GenRegisterInfo((tm.getSubtarget<X86Subtarget>().is64Bit()
+                         ? X86::RIP : X86::EIP),
                        X86_MC::getDwarfRegFlavour(tm.getTargetTriple(), false),
-                       X86_MC::getDwarfRegFlavour(tm.getTargetTriple(), true)),
+                       X86_MC::getDwarfRegFlavour(tm.getTargetTriple(), true),
+                       (tm.getSubtarget<X86Subtarget>().is64Bit()
+                         ? X86::RIP : X86::EIP)),
                        TM(tm), TII(tii) {
   X86_MC::InitLLVM2SEHRegisterMapping(this);
 
diff --git a/utils/TableGen/RegisterInfoEmitter.cpp b/utils/TableGen/RegisterInfoEmitter.cpp
index 66adb61a328..cf225117e1b 100644
--- a/utils/TableGen/RegisterInfoEmitter.cpp
+++ b/utils/TableGen/RegisterInfoEmitter.cpp
@@ -921,9 +921,9 @@ RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
   // MCRegisterInfo initialization routine.
   OS << "static inline void Init" << TargetName
      << "MCRegisterInfo(MCRegisterInfo *RI, unsigned RA, "
-     << "unsigned DwarfFlavour = 0, unsigned EHFlavour = 0) {\n"
+     << "unsigned DwarfFlavour = 0, unsigned EHFlavour = 0, unsigned PC = 0) {\n"
      << "  RI->InitMCRegisterInfo(" << TargetName << "RegDesc, "
-     << Regs.size()+1 << ", RA, " << TargetName << "MCRegisterClasses, "
+     << Regs.size()+1 << ", RA, PC, " << TargetName << "MCRegisterClasses, "
      << RegisterClasses.size() << ", "
      << TargetName << "RegUnitRoots, "
      << RegBank.getNumNativeRegUnits() << ", "
@@ -958,7 +958,7 @@ RegisterInfoEmitter::runTargetHeader(raw_ostream &OS, CodeGenTarget &Target,
 
   OS << "struct " << ClassName << " : public TargetRegisterInfo {\n"
      << "  explicit " << ClassName
-     << "(unsigned RA, unsigned D = 0, unsigned E = 0);\n"
+     << "(unsigned RA, unsigned D = 0, unsigned E = 0, unsigned PC = 0);\n"
      << "  virtual bool needsStackRealignment(const MachineFunction &) const\n"
      << "     { return false; }\n";
   if (!RegBank.getSubRegIndices().empty()) {
@@ -1267,12 +1267,12 @@ RegisterInfoEmitter::runTargetDesc(raw_ostream &OS, CodeGenTarget &Target,
   EmitRegMappingTables(OS, Regs, true);
 
   OS << ClassName << "::\n" << ClassName
-     << "(unsigned RA, unsigned DwarfFlavour, unsigned EHFlavour)\n"
+     << "(unsigned RA, unsigned DwarfFlavour, unsigned EHFlavour, unsigned PC)\n"
      << "  : TargetRegisterInfo(" << TargetName << "RegInfoDesc"
      << ", RegisterClasses, RegisterClasses+" << RegisterClasses.size() <<",\n"
      << "             SubRegIndexNameTable, SubRegIndexLaneMaskTable) {\n"
      << "  InitMCRegisterInfo(" << TargetName << "RegDesc, "
-     << Regs.size()+1 << ", RA,\n                     " << TargetName
+     << Regs.size()+1 << ", RA, PC,\n                     " << TargetName
      << "MCRegisterClasses, " << RegisterClasses.size() << ",\n"
      << "                     " << TargetName << "RegUnitRoots,\n"
      << "                     " << RegBank.getNumNativeRegUnits() << ",\n"