[llvm] [RemoveDIs][DebugInfo] Add DPValue checks to the verifier, prepare DPValue for parsing support (PR #79810)

[Jeremy Morse via llvm-commits]

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@@ -6152,6 +6175,80 @@ static DISubprogram *getSubprogram(Metadata *LocalScope) {
   return nullptr;
 }
 
+void Verifier::visit(DPValue &DPV) {
+  CheckDI(DPV.getType() == DPValue::LocationType::Value ||
+              DPV.getType() == DPValue::LocationType::Declare ||
+              DPV.getType() == DPValue::LocationType::Assign,
+          "invalid #dbg record type", &DPV, DPV.getType());
+  StringRef Kind;
+  switch (DPV.getType()) {
+  case DPValue::LocationType::Value:
+    Kind = "value";
+    break;
+  case DPValue::LocationType::Declare:
+    Kind = "declare";
+    break;
+  case DPValue::LocationType::Assign:
+    Kind = "assign";
+    break;
+  default:
+    llvm_unreachable("Tried to print a DPValue with an invalid LocationType!");
+  };
+  auto *MD = DPV.getRawLocation();
+  CheckDI(isa<ValueAsMetadata>(MD) || isa<DIArgList>(MD) ||
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jmorse wrote:

IMO this wants a comment explaining what kind of value-references we accept, for future readers (mostly so that we can explain the empty-MDNode situation)

https://github.com/llvm/llvm-project/pull/79810