[clang] [llvm] Adapted MemRegion::getDescriptiveName to handle ElementRegions (PR #85104)

[via cfe-commits]

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@@ -720,14 +720,20 @@ std::string MemRegion::getDescriptiveName(bool UseQuotes) const {
       CI->getValue().toString(Idx);
       ArrayIndices = (llvm::Twine("[") + Idx.str() + "]" + ArrayIndices).str();
     }
-    // If not a ConcreteInt, try to obtain the variable
-    // name by calling 'getDescriptiveName' recursively.
-    else {
-      std::string Idx = ER->getDescriptiveName(false);
-      if (!Idx.empty()) {
-        ArrayIndices = (llvm::Twine("[") + Idx + "]" + ArrayIndices).str();
+    // Index is a SymbolVal.
+    else if (auto SI = ER->getIndex().getAs<nonloc::SymbolVal>()) {
+      if (SymbolRef SR = SI->getAsSymbol()) {
+        if (const MemRegion *OR = SR->getOriginRegion()) {
+          std::string Idx = OR->getDescriptiveName(false);
+          ArrayIndices = (llvm::Twine("[") + Idx + "]" + ArrayIndices).str();
+        }
       }
     }
+    // Index is neither a ConcreteInt nor SymbolVal, give up and return.
+    else {
+      assert(false && "we should have a descriptive name");
+      return "";
+    }
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T-Gruber wrote:

Hi @NagyDonat, thank you for the hint. I improved the implementation based on your suggestion and also added 3 more test cases to the unittest. 

https://github.com/llvm/llvm-project/pull/85104