[CodeGen] Introduce a VirtRegOrUnit class to hold virtual reg or physical reg unit. NFC (#123768)

LiveIntervals and MachineVerifier were previously using Register to
store this, but reg units are different than physical registers. One
important difference is that 0 is a valid reg unit number, but it is not
a valid phyiscal register.

This patch introduces a new VirtRegOrUnit class that is distinct from
Register. It can be be converted to/from a virtual Register or a
MCRegUnit. I've made all conversions explicit and used assertions to
check the validity.

I also fixed a place in MachineVerifier that was ignoring reg unit 0.

Author: topperc

llvm/include/llvm/CodeGen/Register.h

@@ -160,6 +160,37 @@ template <> struct DenseMapInfo<Register> {
   }
 };
 
+/// Wrapper class representing a virtual register or register unit.
+class VirtRegOrUnit {
+  unsigned VRegOrUnit;
+
+public:
+  constexpr explicit VirtRegOrUnit(MCRegUnit Unit) : VRegOrUnit(Unit) {
+    assert(!Register::isVirtualRegister(VRegOrUnit));
+  }
+  constexpr explicit VirtRegOrUnit(Register Reg) : VRegOrUnit(Reg.id()) {
+    assert(Reg.isVirtual());
+  }
+
+  constexpr bool isVirtualReg() const {
+    return Register::isVirtualRegister(VRegOrUnit);
+  }
+
+  constexpr MCRegUnit asMCRegUnit() const {
+    assert(!isVirtualReg() && "Not a register unit");
+    return VRegOrUnit;
+  }
+
+  constexpr Register asVirtualReg() const {
+    assert(isVirtualReg() && "Not a virtual register");
+    return Register(VRegOrUnit);
+  }
+
+  constexpr bool operator==(const VirtRegOrUnit &Other) const {
+    return VRegOrUnit == Other.VRegOrUnit;
+  }
+};
+
 } // namespace llvm
 
 #endif // LLVM_CODEGEN_REGISTER_H

llvm/include/llvm/CodeGen/TargetRegisterInfo.h

@@ -466,9 +466,9 @@ class TargetRegisterInfo : public MCRegisterInfo {
   }
 
   /// Returns true if Reg contains RegUnit.
-  bool hasRegUnit(MCRegister Reg, Register RegUnit) const {
+  bool hasRegUnit(MCRegister Reg, MCRegUnit RegUnit) const {
     for (MCRegUnit Unit : regunits(Reg))
-      if (Register(Unit) == RegUnit)
+      if (Unit == RegUnit)
         return true;
     return false;
   }

llvm/lib/CodeGen/LiveIntervals.cpp

@@ -1080,10 +1080,10 @@ class LiveIntervals::HMEditor {
           for (LiveInterval::SubRange &S : LI.subranges()) {
             if ((S.LaneMask & LaneMask).none())
               continue;
-            updateRange(S, Reg, S.LaneMask);
+            updateRange(S, VirtRegOrUnit(Reg), S.LaneMask);
           }
         }
-        updateRange(LI, Reg, LaneBitmask::getNone());
+        updateRange(LI, VirtRegOrUnit(Reg), LaneBitmask::getNone());
         // If main range has a hole and we are moving a subrange use across
         // the hole updateRange() cannot properly handle it since it only
         // gets the LiveRange and not the whole LiveInterval. As a result
@@ -1110,7 +1110,7 @@ class LiveIntervals::HMEditor {
       // precomputed live range.
       for (MCRegUnit Unit : TRI.regunits(Reg.asMCReg()))
         if (LiveRange *LR = getRegUnitLI(Unit))
-          updateRange(*LR, Unit, LaneBitmask::getNone());
+          updateRange(*LR, VirtRegOrUnit(Unit), LaneBitmask::getNone());
     }
     if (hasRegMask)
       updateRegMaskSlots();
@@ -1119,24 +1119,25 @@ class LiveIntervals::HMEditor {
 private:
   /// Update a single live range, assuming an instruction has been moved from
   /// OldIdx to NewIdx.
-  void updateRange(LiveRange &LR, Register Reg, LaneBitmask LaneMask) {
+  void updateRange(LiveRange &LR, VirtRegOrUnit VRegOrUnit,
+                   LaneBitmask LaneMask) {
     if (!Updated.insert(&LR).second)
       return;
     LLVM_DEBUG({
       dbgs() << "     ";
-      if (Reg.isVirtual()) {
-        dbgs() << printReg(Reg);
+      if (VRegOrUnit.isVirtualReg()) {
+        dbgs() << printReg(VRegOrUnit.asVirtualReg());
         if (LaneMask.any())
           dbgs() << " L" << PrintLaneMask(LaneMask);
       } else {
-        dbgs() << printRegUnit(Reg, &TRI);
+        dbgs() << printRegUnit(VRegOrUnit.asMCRegUnit(), &TRI);
       }
       dbgs() << ":\t" << LR << '\n';
     });
     if (SlotIndex::isEarlierInstr(OldIdx, NewIdx))
       handleMoveDown(LR);
     else
-      handleMoveUp(LR, Reg, LaneMask);
+      handleMoveUp(LR, VRegOrUnit, LaneMask);
     LLVM_DEBUG(dbgs() << "        -->\t" << LR << '\n');
     assert(LR.verify());
   }
@@ -1316,7 +1317,8 @@ class LiveIntervals::HMEditor {
 
   /// Update LR to reflect an instruction has been moved upwards from OldIdx
   /// to NewIdx (NewIdx < OldIdx).
-  void handleMoveUp(LiveRange &LR, Register Reg, LaneBitmask LaneMask) {
+  void handleMoveUp(LiveRange &LR, VirtRegOrUnit VRegOrUnit,
+                    LaneBitmask LaneMask) {
     LiveRange::iterator E = LR.end();
     // Segment going into OldIdx.
     LiveRange::iterator OldIdxIn = LR.find(OldIdx.getBaseIndex());
@@ -1340,7 +1342,7 @@ class LiveIntervals::HMEditor {
       SlotIndex DefBeforeOldIdx
         = std::max(OldIdxIn->start.getDeadSlot(),
                    NewIdx.getRegSlot(OldIdxIn->end.isEarlyClobber()));
-      OldIdxIn->end = findLastUseBefore(DefBeforeOldIdx, Reg, LaneMask);
+      OldIdxIn->end = findLastUseBefore(DefBeforeOldIdx, VRegOrUnit, LaneMask);
 
       // Did we have a Def at OldIdx? If not we are done now.
       OldIdxOut = std::next(OldIdxIn);
@@ -1498,11 +1500,12 @@ class LiveIntervals::HMEditor {
   }
 
   // Return the last use of reg between NewIdx and OldIdx.
-  SlotIndex findLastUseBefore(SlotIndex Before, Register Reg,
+  SlotIndex findLastUseBefore(SlotIndex Before, VirtRegOrUnit VRegOrUnit,
                               LaneBitmask LaneMask) {
-    if (Reg.isVirtual()) {
+    if (VRegOrUnit.isVirtualReg()) {
       SlotIndex LastUse = Before;
-      for (MachineOperand &MO : MRI.use_nodbg_operands(Reg)) {
+      for (MachineOperand &MO :
+           MRI.use_nodbg_operands(VRegOrUnit.asVirtualReg())) {
         if (MO.isUndef())
           continue;
         unsigned SubReg = MO.getSubReg();
@@ -1545,7 +1548,7 @@ class LiveIntervals::HMEditor {
       // Check if MII uses Reg.
       for (MIBundleOperands MO(*MII); MO.isValid(); ++MO)
         if (MO->isReg() && !MO->isUndef() && MO->getReg().isPhysical() &&
-            TRI.hasRegUnit(MO->getReg(), Reg))
+            TRI.hasRegUnit(MO->getReg(), VRegOrUnit.asMCRegUnit()))
           return Idx.getRegSlot();
     }
     // Didn't reach Before. It must be the first instruction in the block.