[clang] [clang][StaticAnalyzer] Fix crash in SimpleSValBuilder with unsigned __int128 and negative literals (PR #150225)

[Balazs Benics via cfe-commits]

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@@ -217,12 +217,27 @@ SVal SimpleSValBuilder::MakeSymIntVal(const SymExpr *LHS,
     // Change a+(-N) into a-N, and a-(-N) into a+N
     // Adjust addition/subtraction of negative value, to
     // subtraction/addition of the negated value.
-    APSIntType resultIntTy = BasicVals.getAPSIntType(resultTy);
-    if (isNegationValuePreserving(RHS, resultIntTy)) {
-      ConvertedRHS = BasicVals.getValue(-resultIntTy.convert(RHS));
-      op = (op == BO_Add) ? BO_Sub : BO_Add;
-    } else {
+    // Check if resultTy is valid before using it
+    if (resultTy.isNull()) {
       ConvertedRHS = BasicVals.Convert(resultTy, RHS);
+    } else {
+      APSIntType resultIntTy = BasicVals.getAPSIntType(resultTy);
+      if (isNegationValuePreserving(RHS, resultIntTy)) {
+      // For large unsigned types, we need to be careful about the conversion
+      // to avoid issues with very large intermediate values
+      if (resultIntTy.isUnsigned() && resultIntTy.getBitWidth() > 64) {
+        // For large unsigned types, convert the absolute value directly
+        // instead of converting the negative value and then negating
+        llvm::APSInt AbsRHS = RHS;
+        AbsRHS.negate();
+        ConvertedRHS = BasicVals.Convert(resultTy, AbsRHS);
+      } else {
+        ConvertedRHS = BasicVals.getValue(-resultIntTy.convert(RHS));
+      }
+        op = (op == BO_Add) ? BO_Sub : BO_Add;
+      } else {
+        ConvertedRHS = BasicVals.Convert(resultTy, RHS);
+      }
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steakhal wrote:

I've not checked this part. I'll come back once we  finished with the rest.

https://github.com/llvm/llvm-project/pull/150225