[LiveDebugValues][NVPTX] handle vregs in VarLocBasedImpl, enable pass for NVPTX

This patch handles virtual registers in the VarLocBasedImpl of the LiveDebugVariables pass, allowing it to be used on architectures that depend on virtual registers in debugging, like NVPTX.  It enables the pass for NVPTX.

Author: willghatch

llvm/lib/CodeGen/LiveDebugValues/LiveDebugValues.cpp

@@ -102,14 +102,6 @@ LiveDebugValues::LiveDebugValues() : MachineFunctionPass(ID) {
 }
 
 bool LiveDebugValues::runOnMachineFunction(MachineFunction &MF) {
-  // Except for Wasm, all targets should be only using physical register at this
-  // point. Wasm only use virtual registers throught its pipeline, but its
-  // virtual registers don't participate  in this LiveDebugValues analysis; only
-  // its target indices do.
-  assert(MF.getTarget().getTargetTriple().isWasm() ||
-         MF.getProperties().hasProperty(
-             MachineFunctionProperties::Property::NoVRegs));
-
   bool InstrRefBased = MF.useDebugInstrRef();
   // Allow the user to force selection of InstrRef LDV.
   InstrRefBased |= ForceInstrRefLDV;

llvm/lib/CodeGen/LiveDebugValues/VarLocBasedImpl.cpp

@@ -239,6 +239,10 @@ struct LocIndex {
   /// becomes a problem.
   static constexpr u32_location_t kWasmLocation = kFirstInvalidRegLocation + 2;
 
+  /// The first location that is reserved for VarLocs with locations of kind
+  /// VirtualRegisterKind.
+  static constexpr u32_location_t kFirstVirtualRegLocation = 1 << 31;
+
   LocIndex(u32_location_t Location, u32_index_t Index)
       : Location(Location), Index(Index) {}
 
@@ -810,9 +814,10 @@ class VarLocBasedLDV : public LDVImpl {
         VL.getDescribingRegs(Locations);
         assert(all_of(Locations,
                       [](auto RegNo) {
-                        return RegNo < LocIndex::kFirstInvalidRegLocation;
+                        return (RegNo < LocIndex::kFirstInvalidRegLocation) ||
+                               (LocIndex::kFirstVirtualRegLocation <= RegNo);
                       }) &&
-               "Physreg out of range?");
+               "Physical or virtual register out of range?");
         if (VL.containsSpillLocs())
           Locations.push_back(LocIndex::kSpillLocation);
         if (VL.containsWasmLocs())
@@ -1240,9 +1245,15 @@ void VarLocBasedLDV::getUsedRegs(const VarLocSet &CollectFrom,
       LocIndex::rawIndexForReg(LocIndex::kFirstRegLocation);
   uint64_t FirstInvalidIndex =
       LocIndex::rawIndexForReg(LocIndex::kFirstInvalidRegLocation);
+  uint64_t FirstVirtualRegIndex =
+      LocIndex::rawIndexForReg(LocIndex::kFirstVirtualRegLocation);
   for (auto It = CollectFrom.find(FirstRegIndex),
-            End = CollectFrom.find(FirstInvalidIndex);
-       It != End;) {
+            PhysEnd = CollectFrom.find(FirstInvalidIndex);
+       It != CollectFrom.end();) {
+    if (It == PhysEnd) {
+      It = CollectFrom.find(FirstVirtualRegIndex);
+      continue;
+    }
     // We found a VarLoc ID for a VarLoc that lives in a register. Figure out
     // which register and add it to UsedRegs.
     uint32_t FoundReg = LocIndex::fromRawInteger(*It).Location;

llvm/lib/Target/NVPTX/NVPTXTargetMachine.cpp

@@ -309,7 +309,6 @@ void NVPTXPassConfig::addIRPasses() {
   disablePass(&MachineCopyPropagationID);
   disablePass(&TailDuplicateID);
   disablePass(&StackMapLivenessID);
-  disablePass(&LiveDebugValuesID);
   disablePass(&PostRAMachineSinkingID);
   disablePass(&PostRASchedulerID);
   disablePass(&FuncletLayoutID);