[llvm] [LV][NFC] Fix "vectorization is possible but not beneficial" message (PR #228024)

[David Sherwood via llvm-commits]

https://github.com/david-arm created https://github.com/llvm/llvm-project/pull/228024

None

>From 674eac3d8bdc640a17d7ca26385a955540e41f29 Mon Sep 17 00:00:00 2001
From: David Sherwood <david.sherwood at arm.com>
Date: Thu, 1 Oct 2026 10:26:08 +0000
Subject: [PATCH] [LV][NFC] Fix "vectorization is possible but not beneficial"
 message

---
 llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h   | 5 +++++
 llvm/lib/Transforms/Vectorize/LoopVectorize.cpp            | 7 ++++++-
 .../Transforms/LoopVectorize/AArch64/early_exit_costs.ll   | 2 +-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h b/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
index 733b8647a06e3..2a38d125e68d9 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorizationPlanner.h
@@ -946,6 +946,11 @@ class LoopVectorizationPlanner {
   /// Destroy the cost model.
   void clearCostModel();
 
+  bool hasVectorPlan() const {
+    return any_of(
+        VPlans, [&](const VPlanPtr &Plan) { return !Plan->hasScalarVFOnly(); });
+  }
+
   /// Build VPlans for the specified \p UserVF and \p UserIC if they are
   /// non-zero or all applicable candidate VFs otherwise. If vectorization and
   /// interleaving should be avoided up-front, no plans are generated.
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 45edf702d7092..ffe94ecd075ef 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7985,7 +7985,12 @@ bool LoopVectorizePass::processLoop(Loop *L) {
   std::pair<StringRef, std::string> VecDiagMsg, IntDiagMsg;
   bool VectorizeLoop = true, InterleaveLoop = true;
   if (VF.Width.isScalar()) {
-    LLVM_DEBUG(dbgs() << "LV: Vectorization is possible but not beneficial.\n");
+    if (LVP.hasVectorPlan())
+      LLVM_DEBUG(dbgs() << "LV: Vectorization is not possible. Failed to "
+                           "create any vector vplans.\n");
+    else
+      LLVM_DEBUG(
+          dbgs() << "LV: Vectorization is possible but not beneficial.\n");
     VecDiagMsg = {
         "VectorizationNotBeneficial",
         "the cost-model indicates that vectorization is not beneficial"};
diff --git a/llvm/test/Transforms/LoopVectorize/AArch64/early_exit_costs.ll b/llvm/test/Transforms/LoopVectorize/AArch64/early_exit_costs.ll
index 8dd7ca8971724..1a33b66c3e577 100644
--- a/llvm/test/Transforms/LoopVectorize/AArch64/early_exit_costs.ll
+++ b/llvm/test/Transforms/LoopVectorize/AArch64/early_exit_costs.ll
@@ -91,7 +91,7 @@ loop.end:
 define i64 @vectorization_not_profitable_due_to_trunc(ptr dereferenceable(800) %src) {
 ; CHECK-LABEL: LV: Checking a loop in 'vectorization_not_profitable_due_to_trunc'
 ; CHECK: LV: Selecting VF: 1.
-; CHECK: LV: Vectorization is possible but not beneficial.
+; CHECK: LV: Vectorization is not possible. Failed to create any vector vplans.
 entry:
   br label %loop.header