[clang] [LifetimeSafety] Implement multi-level origins (PR #168344)

[Utkarsh Saxena via cfe-commits]

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@@ -127,24 +177,46 @@ void FactsGenerator::VisitCXXNullPtrLiteralExpr(
     const CXXNullPtrLiteralExpr *N) {
   /// TODO: Handle nullptr expr as a special 'null' loan. Uninitialized
   /// pointers can use the same type of loan.
-  FactMgr.getOriginMgr().getOrCreate(*N);
+  getTree(*N);
 }
 
 void FactsGenerator::VisitImplicitCastExpr(const ImplicitCastExpr *ICE) {
-  if (!hasOrigin(ICE))
+  OriginTree *Dest = getTree(*ICE);
+  if (!Dest)
+    return;
+  OriginTree *SrcTree = getTree(*ICE->getSubExpr());
+
+  if (ICE->getCastKind() == CK_LValueToRValue) {
+    // TODO: Decide what to do for x-values here.
+    if (!ICE->getSubExpr()->isLValue())
+      return;
+
+    assert(SrcTree && "LValue being cast to RValue has no origin tree");
+    // The result of an LValue-to-RValue cast on a reference-to-pointer like
+    // has the inner origin. Get rid of the outer origin.
+    flow(getTree(*ICE), SrcTree->Pointee, /*Kill=*/true);
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usx95 wrote:

Added `getOuterOriginID`​ and `peelOuterOrigin`​members

https://github.com/llvm/llvm-project/pull/168344