[clang] [analyzer] Suppress out of bounds reports after weak loop assumptions (PR #109804)

[Donát Nagy via cfe-commits]

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@@ -323,12 +342,13 @@ class ExprEngine {
 
   /// ProcessBranch - Called by CoreEngine.  Used to generate successor
   ///  nodes by processing the 'effects' of a branch condition.
-  void processBranch(const Stmt *Condition,
-                     NodeBuilderContext& BuilderCtx,
-                     ExplodedNode *Pred,
-                     ExplodedNodeSet &Dst,
-                     const CFGBlock *DstT,
-                     const CFGBlock *DstF);
+  /// If the branch condition is a loop condition, IterationsFinishedInLoop is
+  /// the number of already finished iterations (0, 1, 2...); otherwise it's
+  /// std::nullopt.
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NagyDonat wrote:

> Can't IterationsFinishedInLoop be a state trait? 

We could introduce it, but we'd need to maintain a nested stack of loops (1 iteration in that `while`, then 2 iterations in the `for`, then 1 iteration in this other `for` in the function called there...) to correctly monitor the number of iterations.

This would make the heuristic introduced in this commit slightly more accurate, but I think that for practical purposes the current code is already good enough, so I didn't invest time into implementing this loop iteration count stack. (However it would be a nice follow-up commit if I have time.)

https://github.com/llvm/llvm-project/pull/109804