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

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.

Differential Revision: https://reviews.llvm.org/D96554

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp

@@ -365,11 +365,7 @@ void DwarfExpression::setEntryValueFlags(const MachineLocation &Loc) {
 void DwarfExpression::setLocation(const MachineLocation &Loc,
                                   const DIExpression *DIExpr) {
   if (Loc.isIndirect())
-    // Do not treat entry value descriptions of indirect parameters as memory
+    setMemoryLocationKind();
-    // locations. This allows DwarfExpression::addReg() to add DW_OP_regN to an
-    // entry value description.
-    if (!DIExpr->isEntryValue())
-      setMemoryLocationKind();
 
   if (DIExpr->isEntryValue())
     setEntryValueFlags(Loc);
@@ -380,12 +376,12 @@ void DwarfExpression::beginEntryValueExpression(
   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();
 }
@@ -403,6 +399,7 @@ void DwarfExpression::finalizeEntryValue() {
   // Emit the entry value's DWARF block operand.
   commitTemporaryBuffer();
 
+  LocationKind = SavedLocationKind;
   IsEmittingEntryValue = false;
 }
 
@@ -415,6 +412,7 @@ void DwarfExpression::cancelEntryValue() {
   assert(getTemporaryBufferSize() == 0 &&
          "Began emitting entry value block before cancelling entry value");
 
+  LocationKind = SavedLocationKind;
   IsEmittingEntryValue = false;
 }
 

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h

@@ -148,6 +148,7 @@ protected:
   enum { EntryValue = 1 << 0, Indirect = 1 << 1, CallSiteParamValue = 1 << 2 };
 
   unsigned LocationKind : 3;
+  unsigned SavedLocationKind : 3;
   unsigned LocationFlags : 3;
   unsigned DwarfVersion : 4;
 
@@ -284,8 +285,8 @@ protected:
 public:
   DwarfExpression(unsigned DwarfVersion, DwarfCompileUnit &CU)
       : CU(CU), SubRegisterSizeInBits(0), SubRegisterOffsetInBits(0),
-        LocationKind(Unknown), LocationFlags(Unknown),
+        LocationKind(Unknown), SavedLocationKind(Unknown),
-        DwarfVersion(DwarfVersion) {}
+        LocationFlags(Unknown), DwarfVersion(DwarfVersion) {}
 
   /// This needs to be called last to commit any pending changes.
   void finalize();