Store the LocationKind of an entry value buffer independently from the main LocationKind (NFC)

[aprantl]

Summary

This patch hides the logic for setting the location kind of an entry value inside the begin/finalize/cancel functions. This way we get rid the strange workaround that is currently in setLocation().

In the future, this will allow us to set the location kind of the entry value independently from the location kind of the main expression.

[vsk]

I believe we have test coverage for this path via test/DebugInfo/MIR/AArch64/dbgcall-site-indirect-param-with-offset.mir. Do you think we need anything more?

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp

403

No need to set IsEmittingEntryValue here?

[aprantl]

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp

403

That's a funny copy&paste error!

[aprantl]

Address review feedback.

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h

protected:
   /// The kind of location description being produced.
   enum { Unknown = 0, Register, Memory, Implicit };
 
   /// Additional location flags which may be combined with any location kind.
   /// Currently, entry values are not supported for the Memory location kind.
   enum { EntryValue = 1 << 0, Indirect = 1 << 1, CallSiteParamValue = 1 << 2 };
 
   unsigned LocationKind : 3;
+  unsigned SavedLocationKind : 3;
   unsigned LocationFlags : 3;
   unsigned DwarfVersion : 4;
 
 public:
   /// Set the location (\p Loc) and \ref DIExpression (\p DIExpr) to describe.
   void setLocation(const MachineLocation &Loc, const DIExpression *DIExpr);
 
   bool isUnknownLocation() const { return LocationKind == Unknown; }
protected:
   /// Cancel the emission of an entry value.
   void cancelEntryValue();
 
   ~DwarfExpression() = default;
 
 public:
   DwarfExpression(unsigned DwarfVersion, DwarfCompileUnit &CU)
       : CU(CU), SubRegisterSizeInBits(0), SubRegisterOffsetInBits(0),
-        LocationKind(Unknown), LocationFlags(Unknown),
-        DwarfVersion(DwarfVersion) {}
+        LocationKind(Unknown), SavedLocationKind(Unknown),
+        LocationFlags(Unknown), DwarfVersion(DwarfVersion) {}
 
   /// This needs to be called last to commit any pending changes.
   void finalize();
 
   /// Emit a signed constant.
   void addSignedConstant(int64_t Value);
 
   /// Emit an unsigned constant.

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp

void DwarfExpression::setEntryValueFlags(const MachineLocation &Loc) {
   LocationFlags |= EntryValue;
   if (Loc.isIndirect())
     LocationFlags |= Indirect;
 }
 
 void DwarfExpression::setLocation(const MachineLocation &Loc,
                                   const DIExpression *DIExpr) {
   if (Loc.isIndirect())
-    // Do not treat entry value descriptions of indirect parameters as memory
-    // locations. This allows DwarfExpression::addReg() to add DW_OP_regN to an
-    // entry value description.
-    if (!DIExpr->isEntryValue())
-      setMemoryLocationKind();
 
   if (DIExpr->isEntryValue())
     setEntryValueFlags(Loc);
 }
 
 void DwarfExpression::beginEntryValueExpression(
     DIExpressionCursor &ExprCursor) {
   auto Op = ExprCursor.take();
   (void)Op;
   assert(Op && Op->getOp() == dwarf::DW_OP_LLVM_entry_value);
-  assert(!isMemoryLocation() &&
-         "We don't support entry values of memory locations yet");
   assert(!IsEmittingEntryValue && "Already emitting entry value?");
   assert(Op->getArg(0) == 1 &&
          "Can currently only emit entry values covering a single operation");
 
+  SavedLocationKind = LocationKind;
+  LocationKind = Register;
   IsEmittingEntryValue = true;
   enableTemporaryBuffer();
 }
 
 void DwarfExpression::finalizeEntryValue() {
   assert(IsEmittingEntryValue && "Entry value not open?");
   disableTemporaryBuffer();
 
   emitOp(CU.getDwarf5OrGNULocationAtom(dwarf::DW_OP_entry_value));
 
   // Emit the entry value's size operand.
   unsigned Size = getTemporaryBufferSize();
   emitUnsigned(Size);
 
   // Emit the entry value's DWARF block operand.
   commitTemporaryBuffer();
 
+  LocationKind = SavedLocationKind;
   IsEmittingEntryValue = false;
 }
 
 void DwarfExpression::cancelEntryValue() {
   assert(IsEmittingEntryValue && "Entry value not open?");
   disableTemporaryBuffer();
 
   // The temporary buffer can't be emptied, so for now just assert that nothing
   // has been emitted to it.
   assert(getTemporaryBufferSize() == 0 &&
          "Began emitting entry value block before cancelling entry value");
 
+  LocationKind = SavedLocationKind;
   IsEmittingEntryValue = false;
 }
 
 unsigned DwarfExpression::getOrCreateBaseType(unsigned BitSize,
                                               dwarf::TypeKind Encoding) {
   // Reuse the base_type if we already have one in this CU otherwise we
   // create a new one.
   unsigned I = 0, E = CU.ExprRefedBaseTypes.size();