[clang] [clang][dataflow] Check for backedges directly (instead of loop statements). (PR #68923)

[Yitzhak Mandelbaum via cfe-commits]

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@@ -502,14 +490,15 @@ runTypeErasedDataflowAnalysis(
         PostVisitCFG) {
   PrettyStackTraceAnalysis CrashInfo(CFCtx, "runTypeErasedDataflowAnalysis");
 
-  PostOrderCFGView POV(&CFCtx.getCFG());
-  ForwardDataflowWorklist Worklist(CFCtx.getCFG(), &POV);
+  const clang::CFG &CFG = CFCtx.getCFG();
+  PostOrderCFGView POV(&CFG);
+  ForwardDataflowWorklist Worklist(CFG, &POV);
 
   std::vector<std::optional<TypeErasedDataflowAnalysisState>> BlockStates(
-      CFCtx.getCFG().size());
+      CFG.size());
 
   // The entry basic block doesn't contain statements so it can be skipped.
-  const CFGBlock &Entry = CFCtx.getCFG().getEntry();
+  const CFGBlock &Entry = CFG.getEntry();
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ymand wrote:

it was originally part of this patch, but I ended up undoing some of the new changes. I considered separating this out, but I think for such small NFC changes you run the real risk that you simply won't follow up. That is, it's a great idea, but if we try to make this the norm, I think the result will be many lost small cleanup opportunities. Maybe that's worth it, for review clarity. I don't really know where to draw the line.

https://github.com/llvm/llvm-project/pull/68923