[llvm] [VPlan] Unify inner and outer loop paths (NFCI). (PR #192868)

[Ramkumar Ramachandra via llvm-commits]

================
@@ -7707,40 +7704,58 @@ void LoopVectorizationPlanner::buildVPlansWithVPRecipes(ElementCount MinVF,
   RUN_VPLAN_PASS(VPlanTransforms::createLoopRegions, *VPlan0);
   if (CM.foldTailByMasking())
     RUN_VPLAN_PASS(VPlanTransforms::foldTailByMasking, *VPlan0);
-  RUN_VPLAN_PASS(VPlanTransforms::introduceMasksAndLinearize, *VPlan0);
+  // introduceMasksAndLinearize does not support nested loop regions yet.
+  if (IsInnerLoop)
+    RUN_VPLAN_PASS(VPlanTransforms::introduceMasksAndLinearize, *VPlan0);
 
   auto MaxVFTimes2 = MaxVF * 2;
   for (ElementCount VF = MinVF; ElementCount::isKnownLT(VF, MaxVFTimes2);) {
     VFRange SubRange = {VF, MaxVFTimes2};
-    if (auto Plan = tryToBuildVPlanWithVPRecipes(
-            std::unique_ptr<VPlan>(VPlan0->duplicate()), SubRange, &LVer)) {
-      // Now optimize the initial VPlan.
-      VPlanTransforms::hoistPredicatedLoads(*Plan, PSE, OrigLoop);
-      VPlanTransforms::sinkPredicatedStores(*Plan, PSE, OrigLoop);
-      RUN_VPLAN_PASS(VPlanTransforms::truncateToMinimalBitwidths, *Plan,
-                     CM.getMinimalBitwidths());
-      RUN_VPLAN_PASS(VPlanTransforms::optimize, *Plan);
-      // TODO: try to put addExplicitVectorLength close to addActiveLaneMask
-      if (CM.foldTailWithEVL()) {
-        RUN_VPLAN_PASS(VPlanTransforms::addExplicitVectorLength, *Plan,
-                       CM.getMaxSafeElements());
-        RUN_VPLAN_PASS(VPlanTransforms::optimizeEVLMasks, *Plan);
-      }
+    auto Plan = tryToBuildVPlanWithVPRecipes(
+        std::unique_ptr<VPlan>(VPlan0->duplicate()), SubRange,
+        LVer ? &*LVer : nullptr);
+    VF = SubRange.End;
 
-      if (auto P = VPlanTransforms::narrowInterleaveGroups(*Plan, TTI))
-        VPlans.push_back(std::move(P));
+    if (!Plan)
+      continue;
 
-      RUN_VPLAN_PASS_NO_VERIFY(printOptimizedVPlan, *Plan);
-      assert(verifyVPlanIsValid(*Plan) && "VPlan is invalid");
-      VPlans.push_back(std::move(Plan));
+    VPlanTransforms::hoistPredicatedLoads(*Plan, PSE, OrigLoop);
+    VPlanTransforms::sinkPredicatedStores(*Plan, PSE, OrigLoop);
+    RUN_VPLAN_PASS(VPlanTransforms::truncateToMinimalBitwidths, *Plan,
+                   CM.getMinimalBitwidths());
+    RUN_VPLAN_PASS(VPlanTransforms::optimize, *Plan);
+    // TODO: try to put addExplicitVectorLength close to addActiveLaneMask
+    if (CM.foldTailWithEVL()) {
+      RUN_VPLAN_PASS(VPlanTransforms::addExplicitVectorLength, *Plan,
+                     CM.getMaxSafeElements());
+      RUN_VPLAN_PASS(VPlanTransforms::optimizeEVLMasks, *Plan);
     }
-    VF = SubRange.End;
+
+    if (auto P = VPlanTransforms::narrowInterleaveGroups(*Plan, TTI))
+      VPlans.push_back(std::move(P));
+
+    RUN_VPLAN_PASS_NO_VERIFY(printOptimizedVPlan, *Plan);
+    assert(verifyVPlanIsValid(*Plan) && "VPlan is invalid");
+    VPlans.push_back(std::move(Plan));
   }
 }
 
 VPlanPtr LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(
----------------
artagnon wrote:

```suggestion
VPlanPtr LoopVectorizationPlanner::tryToBuildVPlan(
```

to match buildVPlans?

https://github.com/llvm/llvm-project/pull/192868