[llvm] [VPlan] Don't apply predication discount to non-originally-predicated blocks (PR #160449)

[Florian Hahn via llvm-commits]

================
@@ -366,6 +351,10 @@ struct VPCostContext {
   /// has already been pre-computed.
   bool skipCostComputation(Instruction *UI, bool IsVector) const;
 
+  /// \returns how much the cost of a predicated block should be divided by.
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fhahn wrote:

```suggestion
  /// \returns how much the cost of a predicated block should be divided by. Forwards to LoopVectorizationCostModel::getPredBlockCostDivisor.
```

https://github.com/llvm/llvm-project/pull/160449