[AMDGPU] Use MCRegUnit, insert explicit casts to/from unsigned (NFC)

The casts are currently no-op because `MCRegUnit` is a typedef'ed to
`unsigned`, but this will change soon enough and explicit cast will be
required.

Author: s-barannikov

llvm/lib/Target/AMDGPU/AMDGPUInsertDelayAlu.cpp

@@ -221,7 +221,7 @@ class AMDGPUInsertDelayAlu {
   };
 
   // A map from regunits to the delay info for that regunit.
-  struct DelayState : DenseMap<unsigned, DelayInfo> {
+  struct DelayState : DenseMap<MCRegUnit, DelayInfo> {
     // Merge another DelayState into this one by merging the delay info for each
     // regunit.
     void merge(const DelayState &RHS) {
@@ -359,7 +359,8 @@ class AMDGPUInsertDelayAlu {
     bool Changed = false;
     MachineInstr *LastDelayAlu = nullptr;
 
-    MCRegUnit LastSGPRFromVALU = 0;
+    // FIXME: 0 is a valid register unit.
+    MCRegUnit LastSGPRFromVALU = static_cast<MCRegUnit>(0);
     // Iterate over the contents of bundles, but don't emit any instructions
     // inside a bundle.
     for (auto &MI : MBB.instrs()) {
@@ -379,7 +380,8 @@ class AMDGPUInsertDelayAlu {
         if (It != State.end()) {
           DelayInfo Info = It->getSecond();
           State.advanceByVALUNum(Info.VALUNum);
-          LastSGPRFromVALU = 0;
+          // FIXME: 0 is a valid register unit.
+          LastSGPRFromVALU = static_cast<MCRegUnit>(0);
         }
       }
 

llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp

@@ -643,7 +643,7 @@ int GCNHazardRecognizer::getWaitStatesSinceSetReg(IsHazardFn IsHazard,
 static void addRegUnits(const SIRegisterInfo &TRI, BitVector &BV,
                         MCRegister Reg) {
   for (MCRegUnit Unit : TRI.regunits(Reg))
-    BV.set(Unit);
+    BV.set(static_cast<unsigned>(Unit));
 }
 
 static void addRegsToSet(const SIRegisterInfo &TRI,

llvm/lib/Target/AMDGPU/SIPostRABundler.cpp

@@ -110,7 +110,7 @@ void SIPostRABundler::collectUsedRegUnits(const MachineInstr &MI,
            "subregister indexes should not be present after RA");
 
     for (MCRegUnit Unit : TRI->regunits(Reg))
-      UsedRegUnits.set(Unit);
+      UsedRegUnits.set(static_cast<unsigned>(Unit));
   }
 }
 

llvm/lib/Target/AMDGPU/SIRegisterInfo.cpp

@@ -340,10 +340,12 @@ SIRegisterInfo::SIRegisterInfo(const GCNSubtarget &ST)
          "getNumCoveredRegs() will not work with generated subreg masks!");
 
   RegPressureIgnoredUnits.resize(getNumRegUnits());
-  RegPressureIgnoredUnits.set(*regunits(MCRegister::from(AMDGPU::M0)).begin());
+  RegPressureIgnoredUnits.set(
+      static_cast<unsigned>(*regunits(MCRegister::from(AMDGPU::M0)).begin()));
   for (auto Reg : AMDGPU::VGPR_16RegClass) {
     if (AMDGPU::isHi16Reg(Reg, *this))
-      RegPressureIgnoredUnits.set(*regunits(Reg).begin());
+      RegPressureIgnoredUnits.set(
+          static_cast<unsigned>(*regunits(Reg).begin()));
   }
 
   // HACK: Until this is fully tablegen'd.
@@ -3784,7 +3786,7 @@ unsigned SIRegisterInfo::getRegPressureSetLimit(const MachineFunction &MF,
 const int *SIRegisterInfo::getRegUnitPressureSets(MCRegUnit RegUnit) const {
   static const int Empty[] = { -1 };
 
-  if (RegPressureIgnoredUnits[RegUnit])
+  if (RegPressureIgnoredUnits[static_cast<unsigned>(RegUnit)])
     return Empty;
 
   return AMDGPUGenRegisterInfo::getRegUnitPressureSets(RegUnit);