[llvm] [LV] Use ExtractLane(LastActiveLane, V) live outs when tail-folding. (WIP) (PR #149042)

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``````````bash
git-clang-format --diff HEAD~1 HEAD --extensions h,cpp -- llvm/lib/Transforms/Vectorize/LoopVectorizationLegality.cpp llvm/lib/Transforms/Vectorize/LoopVectorize.cpp llvm/lib/Transforms/Vectorize/VPlan.h llvm/lib/Transforms/Vectorize/VPlanAnalysis.cpp llvm/lib/Transforms/Vectorize/VPlanPredicator.cpp llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp llvm/lib/Transforms/Vectorize/VPlanUnroll.cpp
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View the diff from clang-format here.
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``````````diff
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index dbd97cdad..21b4bf661 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -8447,7 +8447,7 @@ static void addScalarResumePhis(VPRecipeBuilder &Builder, VPlan &Plan,
 /// users in the original exit block using the VPIRInstruction wrapping to the
 /// LCSSA phi.
 static bool addExitUsersForFirstOrderRecurrences(VPlan &Plan, VFRange &Range) {
-   using namespace llvm::VPlanPatternMatch;
+  using namespace llvm::VPlanPatternMatch;
 
   VPRegionBlock *VectorRegion = Plan.getVectorLoopRegion();
   auto *ScalarPHVPBB = Plan.getScalarPreheader();
@@ -8471,10 +8471,10 @@ static bool addExitUsersForFirstOrderRecurrences(VPlan &Plan, VFRange &Range) {
     // recurrences.
 
     if (any_of(FOR->users(), [FOR](VPUser *U) {
-               return match(U, m_VPInstruction<VPInstruction::ExtractLane>(
-                       m_VPValue(), m_Specific(FOR)));
+          return match(U, m_VPInstruction<VPInstruction::ExtractLane>(
+                              m_VPValue(), m_Specific(FOR)));
         }))
-    return false;
+      return false;
 
     // This is the second phase of vectorizing first-order recurrences, creating
     // extract for users outside the loop. An overview of the transformation is
diff --git a/llvm/lib/Transforms/Vectorize/VPlanPredicator.cpp b/llvm/lib/Transforms/Vectorize/VPlanPredicator.cpp
index 9a1e25ee2..efa4bbf19 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanPredicator.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanPredicator.cpp
@@ -303,7 +303,9 @@ VPlanTransforms::introduceMasksAndLinearize(VPlan &Plan, bool FoldTail) {
     PrevVPBB = VPBB;
   }
 
-  // If we folded the tail and introduced a header mask, any extract of the last element must be updated to only extract the last-active-lane of the header mask.
+  // If we folded the tail and introduced a header mask, any extract of the last
+  // element must be updated to only extract the last-active-lane of the header
+  // mask.
   if (FoldTail) {
     assert(Plan.getExitBlocks().size() == 1 &&
            "only a single-exit block is supported currently");

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https://github.com/llvm/llvm-project/pull/149042