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

[Florian Hahn via llvm-commits]

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@@ -10018,11 +10012,8 @@ bool LoopVectorizePass::processLoop(Loop *L) {
       InnerLoopUnroller Unroller(L, PSE, LI, DT, TLI, TTI, AC, ORE, IC, &LVL,
                                  &CM, BFI, PSI, Checks);
 
-      ElementCount BestVF = LVP.getBestVF();
-      assert(BestVF.isScalar() &&
-             "VPlan cost model and legacy cost model disagreed");
-      VPlan &BestPlan = LVP.getBestPlanFor(BestVF);
-      LVP.executePlan(BestVF, IC, BestPlan, Unroller, DT, false);
+      VPlan &BestPlan = LVP.getBestPlanFor(VF.Width);
+      LVP.executePlan(VF.Width, IC, BestPlan, Unroller, DT, false);
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fhahn wrote:

Left as explicitly passing `.Width` for now. The only users of `.Cost` are `selectInterleaveCount`, which only uses it to check if the loop is effectively empty (should not need to check the cost for that using VPlan) and `areRuntimeChecksProfitable` which may be sunk into `getBestVF`

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