[CodeGen][NVPTX] Add a TRI function get the Dwarf register number for a virtual register. (#129017)

NVPTX needs to be able to get the Dwarf register number for a virtual
register. The interface we have for this today is on MCRegisterInfo and
take a MCRegister argument. It shouldn't be legal to convert a Register
containing a virtual register to an MCRegister.

This patch adds a getDwarfRegNumForVirtReg function that takes a
Register to TRI and splits the NVPTX override of getDwarfRegNum.

Author: topperc

llvm/include/llvm/CodeGen/TargetRegisterInfo.h

@@ -1111,6 +1111,10 @@ class TargetRegisterInfo : public MCRegisterInfo {
   prependOffsetExpression(const DIExpression *Expr, unsigned PrependFlags,
                           const StackOffset &Offset) const;
 
+  virtual int64_t getDwarfRegNumForVirtReg(Register RegNum, bool isEH) const {
+    llvm_unreachable("getDwarfRegNumForVirtReg does not exist on this target");
+  }
+
   /// Spill the register so it can be used by the register scavenger.
   /// Return true if the register was spilled, false otherwise.
   /// If this function does not spill the register, the scavenger

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp

@@ -106,7 +106,7 @@ bool DwarfExpression::addMachineReg(const TargetRegisterInfo &TRI,
       return true;
     }
     // Try getting dwarf register for virtual register anyway, eg. for NVPTX.
-    int64_t Reg = TRI.getDwarfRegNum(MachineReg, false);
+    int64_t Reg = TRI.getDwarfRegNumForVirtReg(MachineReg, false);
     if (Reg > 0) {
       DwarfRegs.push_back(Register::createRegister(Reg, nullptr));
       return true;

llvm/lib/Target/NVPTX/NVPTXRegisterInfo.cpp

@@ -170,15 +170,18 @@ void NVPTXRegisterInfo::addToDebugRegisterMap(
 }
 
 int64_t NVPTXRegisterInfo::getDwarfRegNum(MCRegister RegNum, bool isEH) const {
-  if (RegNum.isPhysical()) {
-    StringRef Name = NVPTXInstPrinter::getRegisterName(RegNum.id());
-    // In NVPTXFrameLowering.cpp, we do arrange for %Depot to be accessible from
-    // %SP. Using the %Depot register doesn't provide any debug info in
-    // cuda-gdb, but switching it to %SP does.
-    if (RegNum.id() == NVPTX::VRDepot)
-      Name = "%SP";
-    return encodeRegisterForDwarf(Name);
-  }
+  StringRef Name = NVPTXInstPrinter::getRegisterName(RegNum.id());
+  // In NVPTXFrameLowering.cpp, we do arrange for %Depot to be accessible from
+  // %SP. Using the %Depot register doesn't provide any debug info in
+  // cuda-gdb, but switching it to %SP does.
+  if (RegNum.id() == NVPTX::VRDepot)
+    Name = "%SP";
+  return encodeRegisterForDwarf(Name);
+}
+
+int64_t NVPTXRegisterInfo::getDwarfRegNumForVirtReg(Register RegNum,
+                                                    bool isEH) const {
+  assert(RegNum.isVirtual());
   uint64_t lookup = debugRegisterMap.lookup(RegNum.id());
   if (lookup)
     return lookup;

llvm/lib/Target/NVPTX/NVPTXRegisterInfo.h

@@ -72,6 +72,7 @@ class NVPTXRegisterInfo : public NVPTXGenRegisterInfo {
                              StringRef RegisterName) const;
   void clearDebugRegisterMap() const;
   int64_t getDwarfRegNum(MCRegister RegNum, bool isEH) const override;
+  int64_t getDwarfRegNumForVirtReg(Register RegNum, bool isEH) const override;
 };
 
 StringRef getNVPTXRegClassName(const TargetRegisterClass *RC);