[X86] Refactoring of X86TargetLowering::EmitLoweredSelect. nfc.

[aivchenk]

Summary

Attempt to reduce the mess (276 lines of code in this function)
by putting the functionality of emitting cascaded selects into
a separate function and by extracting the common piece of code
(creating PHIs in the sink block).

[aaboud]

Few minor comments. below.
If I understood the code well, this is a non functional change, is that correct?

lib/Target/X86/X86ISelLowering.cpp

25596 ↗

(On Diff #107512)

How about adding the "static" keyword?

25611 ↗

(On Diff #107512)

You would need this comment before line 25608 above, as it explains the map define at that line.

25724 ↗

(On Diff #107512)

[Style]: Any reason you break the comment line before reaching 80 characters?

25781 ↗

(On Diff #107512)

Calling this helper function for one CMOV is not need (you will not be using half of the code that exist in the helper function), and it is even confusing.
You could simply create a single PHI node here and make the code much more readable.

25784 ↗

(On Diff #107512)

[Style]: Please, use capital letter, "The second ..."

25927 ↗

(On Diff #107512)

You may simply call:

ThisMBB->erase(MIItBegin, MIItEnd);

[aivchenk]

Addressed Amjad's comments

[aivchenk]

Oh, and yes, it is not a functional change (I put "nfc" in the topic)

[craig.topper]

lib/Target/X86/X86ISelLowering.cpp

25612 ↗

(On Diff #109312)

Maybe put a blank line before this return

25710 ↗

(On Diff #109312)

The addLiveIn for jcc1MBB was only conditional on cascadedCMOV in the original code. Should it really be inside this if now?

25871 ↗

(On Diff #109312)

Comment should say ThisMBB not ThiMBB

25879 ↗

(On Diff #109312)

Space after 'always'.

[aivchenk]

Thanks for your comments, especially about addLiveIn one, I missed that

[craig.topper]

This looks ok to me now. @RKSimon, do you want to look at this too?

[RKSimon]

LGTM too

llvm/trunk/lib/Target/X86/X86ISelLowering.h

private:
     EmitVAARG64WithCustomInserter(MachineInstr &MI,
                                   MachineBasicBlock *MBB) const;
 
     /// Utility function to emit the xmm reg save portion of va_start.
     MachineBasicBlock *
     EmitVAStartSaveXMMRegsWithCustomInserter(MachineInstr &BInstr,
                                              MachineBasicBlock *BB) const;
 
+    MachineBasicBlock *EmitLoweredCascadedSelect(MachineInstr &MI1,
+                                                 MachineInstr &MI2,
+                                                 MachineBasicBlock *BB) const;
+
     MachineBasicBlock *EmitLoweredSelect(MachineInstr &I,
                                          MachineBasicBlock *BB) const;
 
     MachineBasicBlock *EmitLoweredAtomicFP(MachineInstr &I,
                                            MachineBasicBlock *BB) const;
 
     MachineBasicBlock *EmitLoweredCatchRet(MachineInstr &MI,
                                            MachineBasicBlock *BB) const;

llvm/trunk/lib/Target/X86/X86ISelLowering.cpp

static bool isCMOVPseudo(MachineInstr &MI) {
   case X86::CMOV_V64I1:
     return true;
 
   default:
     return false;
   }
 }
 
-MachineBasicBlock *
-X86TargetLowering::EmitLoweredSelect(MachineInstr &MI,
-                                     MachineBasicBlock *BB) const {
-  const TargetInstrInfo *TII = Subtarget.getInstrInfo();
-  DebugLoc DL = MI.getDebugLoc();
+// Helper function, which inserts PHI functions into SinkMBB:
+//   %Result(i) = phi [ %FalseValue(i), FalseMBB ], [ %TrueValue(i), TrueMBB ],
+// where %FalseValue(i) and %TrueValue(i) are taken from the consequent CMOVs
+// in [MIItBegin, MIItEnd) range. It returns the last MachineInstrBuilder for
+// the last PHI function inserted.
+static MachineInstrBuilder createPHIsForCMOVsInSinkBB(
+    MachineBasicBlock::iterator MIItBegin, MachineBasicBlock::iterator MIItEnd,
+    MachineBasicBlock *TrueMBB, MachineBasicBlock *FalseMBB,
+    MachineBasicBlock *SinkMBB) {
+  MachineFunction *MF = TrueMBB->getParent();
+  const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
+  DebugLoc DL = MIItBegin->getDebugLoc();
 
-  // To "insert" a SELECT_CC instruction, we actually have to insert the
-  // diamond control-flow pattern.  The incoming instruction knows the
-  // destination vreg to set, the condition code register to branch on, the
-  // true/false values to select between, and a branch opcode to use.
-  const BasicBlock *LLVM_BB = BB->getBasicBlock();
-  MachineFunction::iterator It = ++BB->getIterator();
+  X86::CondCode CC = X86::CondCode(MIItBegin->getOperand(3).getImm());
+  X86::CondCode OppCC = X86::GetOppositeBranchCondition(CC);
 
-  //  thisMBB:
-  //  ...
-  //   TrueVal = ...
-  //   cmpTY ccX, r1, r2
-  //   bCC copy1MBB
-  //   fallthrough --> copy0MBB
-  MachineBasicBlock *thisMBB = BB;
-  MachineFunction *F = BB->getParent();
+  MachineBasicBlock::iterator SinkInsertionPoint = SinkMBB->begin();
 
-  // This code lowers all pseudo-CMOV instructions. Generally it lowers these
-  // as described above, by inserting a BB, and then making a PHI at the join
-  // point to select the true and false operands of the CMOV in the PHI.
-  //
-  // The code also handles two different cases of multiple CMOV opcodes
-  // in a row.
-  //
-  // Case 1:
-  // In this case, there are multiple CMOVs in a row, all which are based on
-  // the same condition setting (or the exact opposite condition setting).
-  // In this case we can lower all the CMOVs using a single inserted BB, and
-  // then make a number of PHIs at the join point to model the CMOVs. The only
-  // trickiness here, is that in a case like:
-  //
-  // t2 = CMOV cond1 t1, f1
-  // t3 = CMOV cond1 t2, f2
-  //
-  // when rewriting this into PHIs, we have to perform some renaming on the
-  // temps since you cannot have a PHI operand refer to a PHI result earlier
-  // in the same block.  The "simple" but wrong lowering would be:
-  //
-  // t2 = PHI t1(BB1), f1(BB2)
-  // t3 = PHI t2(BB1), f2(BB2)
-  //
-  // but clearly t2 is not defined in BB1, so that is incorrect. The proper
-  // renaming is to note that on the path through BB1, t2 is really just a
-  // copy of t1, and do that renaming, properly generating:
-  //
-  // t2 = PHI t1(BB1), f1(BB2)
-  // t3 = PHI t1(BB1), f2(BB2)
-  //
-  // Case 2, we lower cascaded CMOVs such as
+  // As we are creating the PHIs, we have to be careful if there is more than
+  // one.  Later CMOVs may reference the results of earlier CMOVs, but later
+  // PHIs have to reference the individual true/false inputs from earlier PHIs.
+  // That also means that PHI construction must work forward from earlier to
+  // later, and that the code must maintain a mapping from earlier PHI's
+  // destination registers, and the registers that went into the PHI.
+  DenseMap<unsigned, std::pair<unsigned, unsigned>> RegRewriteTable;
+  MachineInstrBuilder MIB;
+
+  for (MachineBasicBlock::iterator MIIt = MIItBegin; MIIt != MIItEnd; ++MIIt) {
+    unsigned DestReg = MIIt->getOperand(0).getReg();
+    unsigned Op1Reg = MIIt->getOperand(1).getReg();
+    unsigned Op2Reg = MIIt->getOperand(2).getReg();
+
+    // If this CMOV we are generating is the opposite condition from
+    // the jump we generated, then we have to swap the operands for the
+    // PHI that is going to be generated.
+    if (MIIt->getOperand(3).getImm() == OppCC)
+      std::swap(Op1Reg, Op2Reg);
+
+    if (RegRewriteTable.find(Op1Reg) != RegRewriteTable.end())
+      Op1Reg = RegRewriteTable[Op1Reg].first;
+
+    if (RegRewriteTable.find(Op2Reg) != RegRewriteTable.end())
+      Op2Reg = RegRewriteTable[Op2Reg].second;
+
+    MIB = BuildMI(*SinkMBB, SinkInsertionPoint, DL, TII->get(X86::PHI), DestReg)
+              .addReg(Op1Reg)
+              .addMBB(FalseMBB)
+              .addReg(Op2Reg)
+              .addMBB(TrueMBB);
+
+    // Add this PHI to the rewrite table.
+    RegRewriteTable[DestReg] = std::make_pair(Op1Reg, Op2Reg);
+  }
+
+  return MIB;
+}
+
+// Lower cascaded selects in form of (SecondCmov (FirstCMOV F, T, cc1), T, cc2).
+MachineBasicBlock *
+X86TargetLowering::EmitLoweredCascadedSelect(MachineInstr &FirstCMOV,
+                                             MachineInstr &SecondCascadedCMOV,
+                                             MachineBasicBlock *ThisMBB) const {
+  const TargetInstrInfo *TII = Subtarget.getInstrInfo();
+  DebugLoc DL = FirstCMOV.getDebugLoc();
+
+  // We lower cascaded CMOVs such as
   //
-  //   (CMOV (CMOV F, T, cc1), T, cc2)
+  //   (SecondCascadedCMOV (FirstCMOV F, T, cc1), T, cc2)
   //
-  // to two successive branches.  For that, we look for another CMOV as the
-  // following instruction.
+  // to two successive branches.
   //
   // Without this, we would add a PHI between the two jumps, which ends up
   // creating a few copies all around. For instance, for
   //
   //    (sitofp (zext (fcmp une)))
   //
   // we would generate:
   //
X86TargetLowering::EmitLoweredCascadedSelect(MachineInstr &FirstCMOV,
   //         ucomiss %xmm1, %xmm0
   //         movss  <1.0f>, %xmm0
   //         jne     .LBB5_4
   //         jp      .LBB5_4
   //         xorps   %xmm0, %xmm0
   // .LBB5_4:
   //         retq
   //
-  MachineInstr *CascadedCMOV = nullptr;
-  MachineInstr *LastCMOV = &MI;
+
+  // We lower cascaded CMOV into two successive branches to the same block.
+  // EFLAGS is used by both, so mark it as live in the second.
+  const BasicBlock *LLVM_BB = ThisMBB->getBasicBlock();
+  MachineFunction *F = ThisMBB->getParent();
+  MachineBasicBlock *FirstInsertedMBB = F->CreateMachineBasicBlock(LLVM_BB);
+  MachineBasicBlock *SecondInsertedMBB = F->CreateMachineBasicBlock(LLVM_BB);
+  MachineBasicBlock *SinkMBB = F->CreateMachineBasicBlock(LLVM_BB);
+
+  MachineFunction::iterator It = ++ThisMBB->getIterator();
+  F->insert(It, FirstInsertedMBB);
+  F->insert(It, SecondInsertedMBB);
+  F->insert(It, SinkMBB);
+
+  // For a cascaded CMOV, we lower it to two successive branches to
+  // the same block (SinkMBB).  EFLAGS is used by both, so mark it as live in
+  // the FirstInsertedMBB.
+  FirstInsertedMBB->addLiveIn(X86::EFLAGS);
+
+  // If the EFLAGS register isn't dead in the terminator, then claim that it's
+  // live into the sink and copy blocks.
+  const TargetRegisterInfo *TRI = Subtarget.getRegisterInfo();
+  if (!SecondCascadedCMOV.killsRegister(X86::EFLAGS) &&
+      !checkAndUpdateEFLAGSKill(SecondCascadedCMOV, ThisMBB, TRI)) {
+    SecondInsertedMBB->addLiveIn(X86::EFLAGS);
+    SinkMBB->addLiveIn(X86::EFLAGS);
+  }
+
+  // Transfer the remainder of ThisMBB and its successor edges to SinkMBB.
+  SinkMBB->splice(SinkMBB->begin(), ThisMBB,
+                  std::next(MachineBasicBlock::iterator(FirstCMOV)),
+                  ThisMBB->end());
+  SinkMBB->transferSuccessorsAndUpdatePHIs(ThisMBB);
+
+  // Fallthrough block for ThisMBB.
+  ThisMBB->addSuccessor(FirstInsertedMBB);
+  // The true block target of the first branch is always SinkMBB.
+  ThisMBB->addSuccessor(SinkMBB);
+  // Fallthrough block for FirstInsertedMBB.
+  FirstInsertedMBB->addSuccessor(SecondInsertedMBB);
+  // The true block for the branch of FirstInsertedMBB.
+  FirstInsertedMBB->addSuccessor(SinkMBB);
+  // This is fallthrough.
+  SecondInsertedMBB->addSuccessor(SinkMBB);
+
+  // Create the conditional branch instructions.
+  X86::CondCode FirstCC = X86::CondCode(FirstCMOV.getOperand(3).getImm());
+  unsigned Opc = X86::GetCondBranchFromCond(FirstCC);
+  BuildMI(ThisMBB, DL, TII->get(Opc)).addMBB(SinkMBB);
+
+  X86::CondCode SecondCC =
+      X86::CondCode(SecondCascadedCMOV.getOperand(3).getImm());
+  unsigned Opc2 = X86::GetCondBranchFromCond(SecondCC);
+  BuildMI(FirstInsertedMBB, DL, TII->get(Opc2)).addMBB(SinkMBB);
+
+  //  SinkMBB:
+  //   %Result = phi [ %FalseValue, SecondInsertedMBB ], [ %TrueValue, ThisMBB ]
+  unsigned DestReg = FirstCMOV.getOperand(0).getReg();
+  unsigned Op1Reg = FirstCMOV.getOperand(1).getReg();
+  unsigned Op2Reg = FirstCMOV.getOperand(2).getReg();
+  MachineInstrBuilder MIB =
+      BuildMI(*SinkMBB, SinkMBB->begin(), DL, TII->get(X86::PHI), DestReg)
+          .addReg(Op1Reg)
+          .addMBB(SecondInsertedMBB)
+          .addReg(Op2Reg)
+          .addMBB(ThisMBB);
+
+  // The second SecondInsertedMBB provides the same incoming value as the
+  // FirstInsertedMBB (the True operand of the SELECT_CC/CMOV nodes).
+  MIB.addReg(FirstCMOV.getOperand(2).getReg()).addMBB(FirstInsertedMBB);
+  // Copy the PHI result to the register defined by the second CMOV.
+  BuildMI(*SinkMBB, std::next(MachineBasicBlock::iterator(MIB.getInstr())), DL,
+          TII->get(TargetOpcode::COPY),
+          SecondCascadedCMOV.getOperand(0).getReg())
+      .addReg(FirstCMOV.getOperand(0).getReg());
+
+  // Now remove the CMOVs.
+  FirstCMOV.eraseFromParent();
+  SecondCascadedCMOV.eraseFromParent();
+
+  return SinkMBB;
+}
+
+MachineBasicBlock *
+X86TargetLowering::EmitLoweredSelect(MachineInstr &MI,
+                                     MachineBasicBlock *ThisMBB) const {
+  const TargetInstrInfo *TII = Subtarget.getInstrInfo();
+  DebugLoc DL = MI.getDebugLoc();
+
+  // To "insert" a SELECT_CC instruction, we actually have to insert the
+  // diamond control-flow pattern.  The incoming instruction knows the
+  // destination vreg to set, the condition code register to branch on, the
+  // true/false values to select between and a branch opcode to use.
+
+  //  ThisMBB:
+  //  ...
+  //   TrueVal = ...
+  //   cmpTY ccX, r1, r2
+  //   bCC copy1MBB
+  //   fallthrough --> FalseMBB
+
+  // This code lowers all pseudo-CMOV instructions. Generally it lowers these
+  // as described above, by inserting a BB, and then making a PHI at the join
+  // point to select the true and false operands of the CMOV in the PHI.
+  //
+  // The code also handles two different cases of multiple CMOV opcodes
+  // in a row.
+  //
+  // Case 1:
+  // In this case, there are multiple CMOVs in a row, all which are based on
+  // the same condition setting (or the exact opposite condition setting).
+  // In this case we can lower all the CMOVs using a single inserted BB, and
+  // then make a number of PHIs at the join point to model the CMOVs. The only
+  // trickiness here, is that in a case like:
+  //
+  // t2 = CMOV cond1 t1, f1
+  // t3 = CMOV cond1 t2, f2
+  //
+  // when rewriting this into PHIs, we have to perform some renaming on the
+  // temps since you cannot have a PHI operand refer to a PHI result earlier
+  // in the same block.  The "simple" but wrong lowering would be:
+  //
+  // t2 = PHI t1(BB1), f1(BB2)
+  // t3 = PHI t2(BB1), f2(BB2)
+  //
+  // but clearly t2 is not defined in BB1, so that is incorrect. The proper
+  // renaming is to note that on the path through BB1, t2 is really just a
+  // copy of t1, and do that renaming, properly generating:
+  //
+  // t2 = PHI t1(BB1), f1(BB2)
+  // t3 = PHI t1(BB1), f2(BB2)
+  //
+  // Case 2:
+  // CMOV ((CMOV F, T, cc1), T, cc2) is checked here and handled by a separate
+  // function - EmitLoweredCascadedSelect.
+
   X86::CondCode CC = X86::CondCode(MI.getOperand(3).getImm());
   X86::CondCode OppCC = X86::GetOppositeBranchCondition(CC);
+  MachineInstr *LastCMOV = &MI;
   MachineBasicBlock::iterator NextMIIt =
       std::next(MachineBasicBlock::iterator(MI));
 
   // Check for case 1, where there are multiple CMOVs with the same condition
   // first.  Of the two cases of multiple CMOV lowerings, case 1 reduces the
   // number of jumps the most.
 
   if (isCMOVPseudo(MI)) {
     // See if we have a string of CMOVS with the same condition.
-    while (NextMIIt != BB->end() && isCMOVPseudo(*NextMIIt) &&
+    while (NextMIIt != ThisMBB->end() && isCMOVPseudo(*NextMIIt) &&
            (NextMIIt->getOperand(3).getImm() == CC ||
             NextMIIt->getOperand(3).getImm() == OppCC)) {
       LastCMOV = &*NextMIIt;
       ++NextMIIt;
     }
   }
 
   // This checks for case 2, but only do this if we didn't already find
   // case 1, as indicated by LastCMOV == MI.
-  if (LastCMOV == &MI && NextMIIt != BB->end() &&
+  if (LastCMOV == &MI && NextMIIt != ThisMBB->end() &&
       NextMIIt->getOpcode() == MI.getOpcode() &&
       NextMIIt->getOperand(2).getReg() == MI.getOperand(2).getReg() &&
       NextMIIt->getOperand(1).getReg() == MI.getOperand(0).getReg() &&
       NextMIIt->getOperand(1).isKill()) {
-    CascadedCMOV = &*NextMIIt;
+    return EmitLoweredCascadedSelect(MI, *NextMIIt, ThisMBB);
   }
 
-  MachineBasicBlock *jcc1MBB = nullptr;
-
-  // If we have a cascaded CMOV, we lower it to two successive branches to
-  // the same block.  EFLAGS is used by both, so mark it as live in the second.
-  if (CascadedCMOV) {
-    jcc1MBB = F->CreateMachineBasicBlock(LLVM_BB);
-    F->insert(It, jcc1MBB);
-    jcc1MBB->addLiveIn(X86::EFLAGS);
-  }
+  const BasicBlock *LLVM_BB = ThisMBB->getBasicBlock();
+  MachineFunction *F = ThisMBB->getParent();
+  MachineBasicBlock *FalseMBB = F->CreateMachineBasicBlock(LLVM_BB);
+  MachineBasicBlock *SinkMBB = F->CreateMachineBasicBlock(LLVM_BB);
 
-  MachineBasicBlock *copy0MBB = F->CreateMachineBasicBlock(LLVM_BB);
-  MachineBasicBlock *sinkMBB = F->CreateMachineBasicBlock(LLVM_BB);
-  F->insert(It, copy0MBB);
-  F->insert(It, sinkMBB);
+  MachineFunction::iterator It = ++ThisMBB->getIterator();
+  F->insert(It, FalseMBB);
+  F->insert(It, SinkMBB);
 
   // If the EFLAGS register isn't dead in the terminator, then claim that it's
   // live into the sink and copy blocks.
   const TargetRegisterInfo *TRI = Subtarget.getRegisterInfo();
-
-  MachineInstr *LastEFLAGSUser = CascadedCMOV ? CascadedCMOV : LastCMOV;
-  if (!LastEFLAGSUser->killsRegister(X86::EFLAGS) &&
-      !checkAndUpdateEFLAGSKill(LastEFLAGSUser, BB, TRI)) {
-    copy0MBB->addLiveIn(X86::EFLAGS);
-    sinkMBB->addLiveIn(X86::EFLAGS);
-  }
-
-  // Transfer the remainder of BB and its successor edges to sinkMBB.
-  sinkMBB->splice(sinkMBB->begin(), BB,
-                  std::next(MachineBasicBlock::iterator(LastCMOV)), BB->end());
-  sinkMBB->transferSuccessorsAndUpdatePHIs(BB);
-
-  // Add the true and fallthrough blocks as its successors.
-  if (CascadedCMOV) {
-    // The fallthrough block may be jcc1MBB, if we have a cascaded CMOV.
-    BB->addSuccessor(jcc1MBB);
-
-    // In that case, jcc1MBB will itself fallthrough the copy0MBB, and
-    // jump to the sinkMBB.
-    jcc1MBB->addSuccessor(copy0MBB);
-    jcc1MBB->addSuccessor(sinkMBB);
-  } else {
-    BB->addSuccessor(copy0MBB);
-  }
-
-  // The true block target of the first (or only) branch is always sinkMBB.
-  BB->addSuccessor(sinkMBB);
+  if (!LastCMOV->killsRegister(X86::EFLAGS) &&
+      !checkAndUpdateEFLAGSKill(LastCMOV, ThisMBB, TRI)) {
+    FalseMBB->addLiveIn(X86::EFLAGS);
+    SinkMBB->addLiveIn(X86::EFLAGS);
+  }
+
+  // Transfer the remainder of ThisMBB and its successor edges to SinkMBB.
+  SinkMBB->splice(SinkMBB->begin(), ThisMBB,
+                  std::next(MachineBasicBlock::iterator(LastCMOV)),
+                  ThisMBB->end());
+  SinkMBB->transferSuccessorsAndUpdatePHIs(ThisMBB);
+
+  // Fallthrough block for ThisMBB.
+  ThisMBB->addSuccessor(FalseMBB);
+  // The true block target of the first (or only) branch is always a SinkMBB.
+  ThisMBB->addSuccessor(SinkMBB);
+  // Fallthrough block for FalseMBB.
+  FalseMBB->addSuccessor(SinkMBB);
 
   // Create the conditional branch instruction.
   unsigned Opc = X86::GetCondBranchFromCond(CC);
-  BuildMI(BB, DL, TII->get(Opc)).addMBB(sinkMBB);
-
-  if (CascadedCMOV) {
-    unsigned Opc2 = X86::GetCondBranchFromCond(
-        (X86::CondCode)CascadedCMOV->getOperand(3).getImm());
-    BuildMI(jcc1MBB, DL, TII->get(Opc2)).addMBB(sinkMBB);
-  }
+  BuildMI(ThisMBB, DL, TII->get(Opc)).addMBB(SinkMBB);
 
-  //  copy0MBB:
-  //   %FalseValue = ...
-  //   # fallthrough to sinkMBB
-  copy0MBB->addSuccessor(sinkMBB);
-
-  //  sinkMBB:
-  //   %Result = phi [ %FalseValue, copy0MBB ], [ %TrueValue, thisMBB ]
+  //  SinkMBB:
+  //   %Result = phi [ %FalseValue, FalseMBB ], [ %TrueValue, ThisMBB ]
   //  ...
   MachineBasicBlock::iterator MIItBegin = MachineBasicBlock::iterator(MI);
   MachineBasicBlock::iterator MIItEnd =
       std::next(MachineBasicBlock::iterator(LastCMOV));
-  MachineBasicBlock::iterator SinkInsertionPoint = sinkMBB->begin();
-  DenseMap<unsigned, std::pair<unsigned, unsigned>> RegRewriteTable;
-  MachineInstrBuilder MIB;
-
-  // As we are creating the PHIs, we have to be careful if there is more than
-  // one.  Later CMOVs may reference the results of earlier CMOVs, but later
-  // PHIs have to reference the individual true/false inputs from earlier PHIs.
-  // That also means that PHI construction must work forward from earlier to
-  // later, and that the code must maintain a mapping from earlier PHI's
-  // destination registers, and the registers that went into the PHI.
-
-  for (MachineBasicBlock::iterator MIIt = MIItBegin; MIIt != MIItEnd; ++MIIt) {
-    unsigned DestReg = MIIt->getOperand(0).getReg();
-    unsigned Op1Reg = MIIt->getOperand(1).getReg();
-    unsigned Op2Reg = MIIt->getOperand(2).getReg();
-
-    // If this CMOV we are generating is the opposite condition from
-    // the jump we generated, then we have to swap the operands for the
-    // PHI that is going to be generated.
-    if (MIIt->getOperand(3).getImm() == OppCC)
-        std::swap(Op1Reg, Op2Reg);
-
-    if (RegRewriteTable.find(Op1Reg) != RegRewriteTable.end())
-      Op1Reg = RegRewriteTable[Op1Reg].first;
-
-    if (RegRewriteTable.find(Op2Reg) != RegRewriteTable.end())
-      Op2Reg = RegRewriteTable[Op2Reg].second;
-
-    MIB = BuildMI(*sinkMBB, SinkInsertionPoint, DL,
-                  TII->get(X86::PHI), DestReg)
-          .addReg(Op1Reg).addMBB(copy0MBB)
-          .addReg(Op2Reg).addMBB(thisMBB);
-
-    // Add this PHI to the rewrite table.
-    RegRewriteTable[DestReg] = std::make_pair(Op1Reg, Op2Reg);
-  }
-
-  // If we have a cascaded CMOV, the second Jcc provides the same incoming
-  // value as the first Jcc (the True operand of the SELECT_CC/CMOV nodes).
-  if (CascadedCMOV) {
-    MIB.addReg(MI.getOperand(2).getReg()).addMBB(jcc1MBB);
-    // Copy the PHI result to the register defined by the second CMOV.
-    BuildMI(*sinkMBB, std::next(MachineBasicBlock::iterator(MIB.getInstr())),
-            DL, TII->get(TargetOpcode::COPY),
-            CascadedCMOV->getOperand(0).getReg())
-        .addReg(MI.getOperand(0).getReg());
-    CascadedCMOV->eraseFromParent();
-  }
+  createPHIsForCMOVsInSinkBB(MIItBegin, MIItEnd, ThisMBB, FalseMBB, SinkMBB);
 
   // Now remove the CMOV(s).
-  for (MachineBasicBlock::iterator MIIt = MIItBegin; MIIt != MIItEnd; )
-    (MIIt++)->eraseFromParent();
+  ThisMBB->erase(MIItBegin, MIItEnd);
 
-  return sinkMBB;
+  return SinkMBB;
 }
 
 MachineBasicBlock *
 X86TargetLowering::EmitLoweredAtomicFP(MachineInstr &MI,
                                        MachineBasicBlock *BB) const {
   // Combine the following atomic floating-point modification pattern:
   //   a.store(reg OP a.load(acquire), release)
   // Transform them into: