[NFC][Regalloc] VirtRegAuxInfo::Hint does not need to be a field

It is only used in weightCalcHelper, and cleared upon its finishing its
job there.

The patch further cleans up style guide discrepancies, and simplifies
CopyHint by removing duplicate 'IsPhys' information (it's what the Reg
field would report).

Author: mtrofin

llvm/include/llvm/CodeGen/CalcSpillWeights.h

@@ -49,7 +49,6 @@ class VirtRegMap;
     VirtRegMap *const VRM;
     const MachineLoopInfo &Loops;
     const MachineBlockFrequencyInfo &MBFI;
-    DenseMap<unsigned, float> Hint;
 
   public:
     VirtRegAuxInfo(MachineFunction &MF, LiveIntervals &LIS, VirtRegMap *VRM,

llvm/lib/CodeGen/CalcSpillWeights.cpp

@@ -150,10 +150,10 @@ float VirtRegAuxInfo::weightCalcHelper(LiveInterval &LI, SlotIndex *Start,
   MachineLoop *Loop = nullptr;
   bool IsExiting = false;
   float TotalWeight = 0;
-  unsigned NumInstr = 0; // Number of instructions using li
+  unsigned NumInstr = 0; // Number of instructions using LI
   SmallPtrSet<MachineInstr *, 8> Visited;
 
-  std::pair<unsigned, unsigned> TargetHint = MRI.getRegAllocationHint(LI.reg());
+  std::pair<Register, Register> TargetHint = MRI.getRegAllocationHint(LI.reg());
 
   if (LI.isSpillable() && VRM) {
     Register Reg = LI.reg();
@@ -192,22 +192,21 @@ float VirtRegAuxInfo::weightCalcHelper(LiveInterval &LI, SlotIndex *Start,
 
   // CopyHint is a sortable hint derived from a COPY instruction.
   struct CopyHint {
-    unsigned Reg;
-    float Weight;
-    bool IsPhys;
-    CopyHint(unsigned R, float W, bool P) :
-      Reg(R), Weight(W), IsPhys(P) {}
-    bool operator<(const CopyHint &rhs) const {
+    const Register Reg;
+    const float Weight;
+    CopyHint(Register R, float W) : Reg(R), Weight(W) {}
+    bool operator<(const CopyHint &Rhs) const {
       // Always prefer any physreg hint.
-      if (IsPhys != rhs.IsPhys)
-        return (IsPhys && !rhs.IsPhys);
-      if (Weight != rhs.Weight)
-        return (Weight > rhs.Weight);
-      return Reg < rhs.Reg; // Tie-breaker.
+      if (Reg.isPhysical() != Rhs.Reg.isPhysical())
+        return Reg.isPhysical();
+      if (Weight != Rhs.Weight)
+        return (Weight > Rhs.Weight);
+      return Reg.id() < Rhs.Reg.id(); // Tie-breaker.
     }
   };
-  std::set<CopyHint> CopyHints;
 
+  std::set<CopyHint> CopyHints;
+  DenseMap<unsigned, float> Hint;
   for (MachineRegisterInfo::reg_instr_nodbg_iterator
            I = MRI.reg_instr_nodbg_begin(LI.reg()),
            E = MRI.reg_instr_nodbg_end();
@@ -250,28 +249,25 @@ float VirtRegAuxInfo::weightCalcHelper(LiveInterval &LI, SlotIndex *Start,
     // Get allocation hints from copies.
     if (!MI->isCopy())
       continue;
-    Register hint = copyHint(MI, LI.reg(), TRI, MRI);
-    if (!hint)
+    Register HintReg = copyHint(MI, LI.reg(), TRI, MRI);
+    if (!HintReg)
       continue;
     // Force hweight onto the stack so that x86 doesn't add hidden precision,
     // making the comparison incorrectly pass (i.e., 1 > 1 == true??).
     //
     // FIXME: we probably shouldn't use floats at all.
-    volatile float HWeight = Hint[hint] += Weight;
-    if (Register::isVirtualRegister(hint) || MRI.isAllocatable(hint))
-      CopyHints.insert(
-          CopyHint(hint, HWeight, Register::isPhysicalRegister(hint)));
+    volatile float HWeight = Hint[HintReg] += Weight;
+    if (HintReg.isVirtual() || MRI.isAllocatable(HintReg))
+      CopyHints.insert(CopyHint(HintReg, HWeight));
   }
 
-  Hint.clear();
-
   // Pass all the sorted copy hints to mri.
   if (ShouldUpdateLI && CopyHints.size()) {
     // Remove a generic hint if previously added by target.
     if (TargetHint.first == 0 && TargetHint.second)
       MRI.clearSimpleHint(LI.reg());
 
-    std::set<unsigned> HintedRegs;
+    std::set<Register> HintedRegs;
     for (auto &Hint : CopyHints) {
       if (!HintedRegs.insert(Hint.Reg).second ||
           (TargetHint.first != 0 && Hint.Reg == TargetHint.second))