[llvm] [LoopUnroll] Enhance the use of Optimization Remarks and LLVM_DEBUG (PR #178476)

[Justin Fargnoli via llvm-commits]

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@@ -707,20 +713,29 @@ UnrollCostEstimator::UnrollCostEstimator(
     LoopSize = BEInsns + 1;
 }
 
-bool UnrollCostEstimator::canUnroll() const {
-  switch (Convergence) {
-  case ConvergenceKind::ExtendedLoop:
-    LLVM_DEBUG(dbgs() << "  Convergence prevents unrolling.\n");
+bool UnrollCostEstimator::canUnroll(OptimizationRemarkEmitter *ORE,
+                                    const Loop *L) const {
+  // Helper to emit debug output and a missed optimization remark.
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justinfargnoli wrote:

```suggestion
```

https://github.com/llvm/llvm-project/pull/178476