3 files changed, 16 insertions, 4 deletions
diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 6dd04ae..f156cb8 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -8536,8 +8536,10 @@ void LoopVectorizationPlanner::buildVPlansWithVPRecipes(ElementCount MinVF,
             *Plan, CM.getMinimalBitwidths(), PSE.getSE()->getContext());
       VPlanTransforms::optimize(*Plan, *PSE.getSE());
       // TODO: try to put it close to addActiveLaneMask().
-      if (CM.foldTailWithEVL())
-        VPlanTransforms::addExplicitVectorLength(*Plan);
+      // Discard the plan if it is not EVL-compatible
+      if (CM.foldTailWithEVL() &&
+          !VPlanTransforms::tryAddExplicitVectorLength(*Plan))
+        break;
       assert(verifyVPlanIsValid(*Plan) && "VPlan is invalid");
       VPlans.push_back(std::move(Plan));
     }
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
index 7ff8d8e..422579e 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp
@@ -1318,8 +1318,16 @@ void VPlanTransforms::addActiveLaneMask(
 /// %NextEVLIV = add IVSize (cast i32 %VPEVVL to IVSize), %EVLPhi
 /// ...
 ///
-void VPlanTransforms::addExplicitVectorLength(VPlan &Plan) {
+bool VPlanTransforms::tryAddExplicitVectorLength(VPlan &Plan) {
   VPBasicBlock *Header = Plan.getVectorLoopRegion()->getEntryBasicBlock();
+  // The transform updates all users of inductions to work based on EVL, instead
+  // of the VF directly. At the moment, widened inductions cannot be updated, so
+  // bail out if the plan contains any.
+  if (any_of(Header->phis(), [](VPRecipeBase &Phi) {
+        return (isa<VPWidenIntOrFpInductionRecipe>(&Phi) ||
+                isa<VPWidenPointerInductionRecipe>(&Phi));
+      }))
+    return false;
   auto *CanonicalIVPHI = Plan.getCanonicalIV();
   VPValue *StartV = CanonicalIVPHI->getStartValue();
 
@@ -1377,6 +1385,7 @@ void VPlanTransforms::addExplicitVectorLength(VPlan &Plan) {
   CanonicalIVIncrement->setOperand(0, CanonicalIVPHI);
   // TODO: support unroll factor > 1.
   Plan.setUF(1);
+  return true;
 }
 
 void VPlanTransforms::dropPoisonGeneratingRecipes(
diff --git a/llvm/lib/Transforms/Vectorize/VPlanTransforms.h b/llvm/lib/Transforms/Vectorize/VPlanTransforms.h
index 0cbc707..96b8a66 100644
--- a/llvm/lib/Transforms/Vectorize/VPlanTransforms.h
+++ b/llvm/lib/Transforms/Vectorize/VPlanTransforms.h
@@ -104,7 +104,8 @@ struct VPlanTransforms {
   /// VPCanonicalIVPHIRecipe with a VPEVLBasedIVPHIRecipe.
   /// VPCanonicalIVPHIRecipe is only used to control the loop after
   /// this transformation.
-  static void addExplicitVectorLength(VPlan &Plan);
+  /// \returns true if the transformation succeeds, or false if it doesn't.
+  static bool tryAddExplicitVectorLength(VPlan &Plan);
 };
 
 } // namespace llvm