[llvm] [VPlan] Only use selectVectorizationFactor for cross-check (NFCI). (PR #103033)

[via llvm-commits]

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@@ -7031,11 +7030,10 @@ LoopVectorizationPlanner::plan(ElementCount UserVF, unsigned UserIC) {
         if (!hasPlanWithVF(UserVF)) {
           LLVM_DEBUG(dbgs()
                      << "LV: No VPlan could be built for " << UserVF << ".\n");
-          return std::nullopt;
         }
 
         LLVM_DEBUG(printPlans(dbgs()));
-        return {{UserVF, 0, 0}};
+        return;
       } else
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ayalz wrote:

Just noting another else-after-return, below, but perhaps there it overall looks better(?):
```
    return false;
  } else if (!VectorizeLoop && InterleaveLoop) {
```

https://github.com/llvm/llvm-project/pull/103033