[llvm] [StructurizeCFG] Fix a crash caused by not updating `Predicates` properly (PR #124051)

[Matt Arsenault via llvm-commits]

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@@ -971,6 +971,10 @@ void StructurizeCFG::changeExit(RegionNode *Node, BasicBlock *NewExit,
     SubRegion->replaceExit(NewExit);
   } else {
     BasicBlock *BB = Node->getNodeAs<BasicBlock>();
+    for (BasicBlock *Succ : successors(BB)) {
+      if (Succ != NewExit)
+        Predicates[Succ].erase(BB);
+    }
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arsenm wrote:

What makes you think it's on purpose? 

The predicates collects branch conditions used in the CFG, so it makes sense to me that you would need to adjust those when the CFG changes 

https://github.com/llvm/llvm-project/pull/124051