[llvm] [VPlan] Move initial skeleton construction earlier (NFC). (PR #150848)

[via llvm-commits]

================
@@ -8918,10 +8920,13 @@ VPlanPtr LoopVectorizationPlanner::tryToBuildVPlan(VFRange &Range) {
   assert(EnableVPlanNativePath && "VPlan-native path is not enabled.");
 
   auto Plan = VPlanTransforms::buildPlainCFG(OrigLoop, *LI);
-  VPlanTransforms::prepareForVectorization(
-      *Plan, Legal->getWidestInductionType(), PSE, true, false, OrigLoop,
-      getDebugLocFromInstOrOperands(Legal->getPrimaryInduction()), false,
-      Range);
+
+  VPlanTransforms::addInitialSkeleton(
+      *Plan, Legal->getWidestInductionType(),
+      getDebugLocFromInstOrOperands(Legal->getPrimaryInduction()), PSE,
+      OrigLoop);
+  VPlanTransforms::handleEarlyExitsAndAddMiddleCheck(*Plan, true, false, false,
----------------
ayalz wrote:

+1
```suggestion
  VPlanTransforms::handleEarlyExitsAndAddMiddleCheck(*Plan, true /* requires scalar epilog check */, false /*fold tail by masking */, false /*has uncountable exit */,
```

https://github.com/llvm/llvm-project/pull/150848