Refactor UpdatePredRedefs and StepForward to avoid duplication. NFC

Note, this is a reapplication of r236515 with a fix to not assert on non-register operands, but instead only handle them until the subsequent commit.  Original commit message follows.

The code was basically the same here already.  Just added an out parameter for a vector of seen defs so that UpdatePredRedefs can call StepForward first, then do its own post processing on the seen defs.

Will be used in the next commit to also handle regmasks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236538 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/LivePhysRegs.h

@@ -93,7 +93,8 @@ public:
   }
 
   /// \brief Removes physical registers clobbered by the regmask operand @p MO.
-  void removeRegsInMask(const MachineOperand &MO);
+  void removeRegsInMask(const MachineOperand &MO,
+        SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> *Clobbers);
 
   /// \brief Returns true if register @p Reg is contained in the set. This also
   /// works if only the super register of @p Reg has been defined, because we
@@ -109,7 +110,11 @@ public:
   /// instruction(bundle): Remove killed-uses, add defs. This is the not
   /// recommended way, because it depends on accurate kill flags. If possible
   /// use stepBackwards() instead of this function.
-  void stepForward(const MachineInstr &MI);
+  /// The clobbers set will be the list of registers either defined or clobbered
+  /// by a regmask.  The operand will identify whether this is a regmask or
+  /// register operand.
+  void stepForward(const MachineInstr &MI,
+        SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> &Clobbers);
 
   /// \brief Adds all live-in registers of basic block @p MBB.
   void addLiveIns(const MachineBasicBlock *MBB) {

lib/CodeGen/IfConversion.cpp

@@ -975,26 +975,18 @@ void IfConverter::RemoveExtraEdges(BBInfo &BBI) {
 /// Behaves like LiveRegUnits::StepForward() but also adds implicit uses to all
 /// values defined in MI which are not live/used by MI.
 static void UpdatePredRedefs(MachineInstr *MI, LivePhysRegs &Redefs) {
-  for (ConstMIBundleOperands Ops(MI); Ops.isValid(); ++Ops) {
-    if (!Ops->isReg() || !Ops->isKill())
-      continue;
-    unsigned Reg = Ops->getReg();
-    if (Reg == 0)
-      continue;
-    Redefs.removeReg(Reg);
-  }
-  for (MIBundleOperands Ops(MI); Ops.isValid(); ++Ops) {
-    if (!Ops->isReg() || !Ops->isDef())
-      continue;
-    unsigned Reg = Ops->getReg();
-    if (Reg == 0 || Redefs.contains(Reg))
-      continue;
-    Redefs.addReg(Reg);
+  SmallVector<std::pair<unsigned, const MachineOperand*>, 4> Clobbers;
+  Redefs.stepForward(*MI, Clobbers);
 
-    MachineOperand &Op = *Ops;
-    MachineInstr *MI = Op.getParent();
-    MachineInstrBuilder MIB(*MI->getParent()->getParent(), MI);
-    MIB.addReg(Reg, RegState::Implicit | RegState::Undef);
+  // Now add the implicit uses for each of the clobbered values.
+  for (auto Reg : Clobbers) {
+    const MachineOperand &Op = *Reg.second;
+    // FIXME: Const cast here is nasty, but better than making StepForward
+    // take a mutable instruction instead of const.
+    MachineInstr *OpMI = const_cast<MachineInstr*>(Op.getParent());
+    MachineInstrBuilder MIB(*OpMI->getParent()->getParent(), OpMI);
+    if (Op.isReg())
+      MIB.addReg(Reg.first, RegState::Implicit | RegState::Undef);
   }
 }
 
@@ -1374,7 +1366,8 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI, IfcvtKind Kind,
 
   for (MachineBasicBlock::const_iterator I = BBI1->BB->begin(), E = DI1; I != E;
        ++I) {
-    Redefs.stepForward(*I);
+    SmallVector<std::pair<unsigned, const MachineOperand*>, 4> IgnoredClobbers;
+    Redefs.stepForward(*I, IgnoredClobbers);
   }
   BBI.BB->splice(BBI.BB->end(), BBI1->BB, BBI1->BB->begin(), DI1);
   BBI2->BB->erase(BBI2->BB->begin(), DI2);

lib/CodeGen/LivePhysRegs.cpp

@@ -22,12 +22,17 @@ using namespace llvm;
 
 /// \brief Remove all registers from the set that get clobbered by the register
 /// mask.
-void LivePhysRegs::removeRegsInMask(const MachineOperand &MO) {
+/// The clobbers set will be the list of live registers clobbered
+/// by the regmask.
+void LivePhysRegs::removeRegsInMask(const MachineOperand &MO,
+        SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> *Clobbers) {
   SparseSet<unsigned>::iterator LRI = LiveRegs.begin();
   while (LRI != LiveRegs.end()) {
-    if (MO.clobbersPhysReg(*LRI))
+    if (MO.clobbersPhysReg(*LRI)) {
+      if (Clobbers)
+        Clobbers->push_back(std::make_pair(*LRI, &MO));
       LRI = LiveRegs.erase(LRI);
-    else
+    } else
       ++LRI;
   }
 }
@@ -45,7 +50,7 @@ void LivePhysRegs::stepBackward(const MachineInstr &MI) {
         continue;
       removeReg(Reg);
     } else if (O->isRegMask())
-      removeRegsInMask(*O);
+      removeRegsInMask(*O, nullptr);
   }
 
   // Add uses to the set.
@@ -63,8 +68,8 @@ void LivePhysRegs::stepBackward(const MachineInstr &MI) {
 /// killed-uses, add defs. This is the not recommended way, because it depends
 /// on accurate kill flags. If possible use stepBackwards() instead of this
 /// function.
-void LivePhysRegs::stepForward(const MachineInstr &MI) {
-  SmallVector<unsigned, 4> Defs;
+void LivePhysRegs::stepForward(const MachineInstr &MI,
+        SmallVectorImpl<std::pair<unsigned, const MachineOperand*>> &Clobbers) {
   // Remove killed registers from the set.
   for (ConstMIBundleOperands O(&MI); O.isValid(); ++O) {
     if (O->isReg()) {
@@ -73,7 +78,7 @@ void LivePhysRegs::stepForward(const MachineInstr &MI) {
         continue;
       if (O->isDef()) {
         if (!O->isDead())
-          Defs.push_back(Reg);
+          Clobbers.push_back(std::make_pair(Reg, &*O));
       } else {
         if (!O->isKill())
           continue;
@@ -81,12 +86,12 @@ void LivePhysRegs::stepForward(const MachineInstr &MI) {
         removeReg(Reg);
       }
     } else if (O->isRegMask())
-      removeRegsInMask(*O);
+      removeRegsInMask(*O, &Clobbers);
   }
 
   // Add defs to the set.
-  for (unsigned i = 0, e = Defs.size(); i != e; ++i)
-    addReg(Defs[i]);
+  for (auto Reg : Clobbers)
+    addReg(Reg.first);
 }
 
 /// Prin the currently live registers to OS.