[VPlan] Add helper to run VPlan passes, verify after run (NFC).

Add new runPass helpers to run a VPlan transformation. This makes it
easier to add additional checks/functionality for each transform run. In
this patch, an option is added to run the verifier after each VPlan
transform.

Follow-ups will use the same helper to also support printing VPlans
after each transform.

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -355,6 +355,16 @@ cl::opt<bool> EnableVPlanNativePath(
     "enable-vplan-native-path", cl::Hidden,
     cl::desc("Enable VPlan-native vectorization path with "
              "support for outer loop vectorization."));
+
+cl::opt<bool>
+    VerifyEachVPlan("vplan-verify-each",
+#ifdef EXPENSIVE_CHECKS
+                    cl::init(true),
+#else
+                    cl::init(false),
+#endif
+                    cl::Hidden,
+                    cl::desc("Verfiy VPlans after VPlan transforms."));
 } // namespace llvm
 
 // This flag enables the stress testing of the VPlan H-CFG construction in the
@@ -7649,8 +7659,8 @@ DenseMap<const SCEV *, Value *> LoopVectorizationPlanner::executePlan(
 
   // TODO: Move to VPlan transform stage once the transition to the VPlan-based
   // cost model is complete for better cost estimates.
-  VPlanTransforms::unrollByUF(BestVPlan, BestUF,
-                              OrigLoop->getHeader()->getContext());
+  VPlanTransforms::runPass(VPlanTransforms::unrollByUF, BestVPlan, BestUF,
+                           OrigLoop->getHeader()->getContext());
   VPlanTransforms::optimizeForVFAndUF(BestVPlan, BestVF, BestUF, PSE);
   VPlanTransforms::convertToConcreteRecipes(BestVPlan);
 
@@ -8887,13 +8897,14 @@ void LoopVectorizationPlanner::buildVPlansWithVPRecipes(ElementCount MinVF,
     if (auto Plan = tryToBuildVPlanWithVPRecipes(SubRange)) {
       // Now optimize the initial VPlan.
       if (!Plan->hasVF(ElementCount::getFixed(1)))
-        VPlanTransforms::truncateToMinimalBitwidths(*Plan,
-                                                    CM.getMinimalBitwidths());
+        VPlanTransforms::runPass(VPlanTransforms::truncateToMinimalBitwidths,
+                                 *Plan, CM.getMinimalBitwidths());
       VPlanTransforms::optimize(*Plan);
       // TODO: try to put it close to addActiveLaneMask().
       // Discard the plan if it is not EVL-compatible
-      if (CM.foldTailWithEVL() && !VPlanTransforms::tryAddExplicitVectorLength(
-                                      *Plan, CM.getMaxSafeElements()))
+      if (CM.foldTailWithEVL() &&
+          !VPlanTransforms::runPass(VPlanTransforms::tryAddExplicitVectorLength,
+                                    *Plan, CM.getMaxSafeElements()))
         break;
       assert(verifyVPlanIsValid(*Plan) && "VPlan is invalid");
       VPlans.push_back(std::move(Plan));
@@ -9393,8 +9404,9 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
 
   if (auto *UncountableExitingBlock =
           Legal->getUncountableEarlyExitingBlock()) {
-    VPlanTransforms::handleUncountableEarlyExit(
-        *Plan, *PSE.getSE(), OrigLoop, UncountableExitingBlock, RecipeBuilder);
+    VPlanTransforms::runPass(VPlanTransforms::handleUncountableEarlyExit, *Plan,
+                             *PSE.getSE(), OrigLoop, UncountableExitingBlock,
+                             RecipeBuilder);
   }
   DenseMap<VPValue *, VPValue *> IVEndValues;
   addScalarResumePhis(RecipeBuilder, *Plan, IVEndValues);
@@ -9419,8 +9431,9 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
   // Interleave memory: for each Interleave Group we marked earlier as relevant
   // for this VPlan, replace the Recipes widening its memory instructions with a
   // single VPInterleaveRecipe at its insertion point.
-  VPlanTransforms::createInterleaveGroups(
-      *Plan, InterleaveGroups, RecipeBuilder, CM.isScalarEpilogueAllowed());
+  VPlanTransforms::runPass(VPlanTransforms::createInterleaveGroups, *Plan,
+                           InterleaveGroups, RecipeBuilder,
+                           CM.isScalarEpilogueAllowed());
 
   for (ElementCount VF : Range)
     Plan->addVF(VF);
@@ -9462,13 +9475,16 @@ LoopVectorizationPlanner::tryToBuildVPlanWithVPRecipes(VFRange &Range) {
     }
   }
 
-  VPlanTransforms::dropPoisonGeneratingRecipes(*Plan, [this](BasicBlock *BB) {
+  auto BlockNeedsPredication = [this](BasicBlock *BB) {
     return Legal->blockNeedsPredication(BB);
-  });
+  };
+  VPlanTransforms::runPass(VPlanTransforms::dropPoisonGeneratingRecipes, *Plan,
+                           BlockNeedsPredication);
 
   // Sink users of fixed-order recurrence past the recipe defining the previous
   // value and introduce FirstOrderRecurrenceSplice VPInstructions.
-  if (!VPlanTransforms::adjustFixedOrderRecurrences(*Plan, Builder))
+  if (!VPlanTransforms::runPass(VPlanTransforms::adjustFixedOrderRecurrences,
+                                *Plan, Builder))
     return nullptr;
 
   if (useActiveLaneMask(Style)) {
@@ -9817,10 +9833,10 @@ void LoopVectorizationPlanner::adjustRecipesForReductions(
       PhiR->setOperand(0, Plan->getOrAddLiveIn(RdxDesc.getSentinelValue()));
     }
   }
-
-  VPlanTransforms::clearReductionWrapFlags(*Plan);
   for (VPRecipeBase *R : ToDelete)
     R->eraseFromParent();
+
+  VPlanTransforms::runPass(VPlanTransforms::clearReductionWrapFlags, *Plan);
 }
 
 void VPDerivedIVRecipe::execute(VPTransformState &State) {
@@ -10184,7 +10200,7 @@ static void preparePlanForMainVectorLoop(VPlan &MainPlan, VPlan &EpiPlan) {
     VPIRInst->eraseFromParent();
     ResumePhi->eraseFromParent();
   }
-  VPlanTransforms::removeDeadRecipes(MainPlan);
+  VPlanTransforms::runPass(VPlanTransforms::removeDeadRecipes, MainPlan);
 
   using namespace VPlanPatternMatch;
   VPBasicBlock *MainScalarPH = MainPlan.getScalarPreheader();

llvm/lib/Transforms/Vectorize/VPlan.cpp

@@ -52,6 +52,7 @@ using namespace llvm::VPlanPatternMatch;
 namespace llvm {
 extern cl::opt<bool> EnableVPlanNativePath;
 }
+
 extern cl::opt<unsigned> ForceTargetInstructionCost;
 
 static cl::opt<bool> PrintVPlansInDotFormat(

llvm/lib/Transforms/Vectorize/VPlanTransforms.cpp

@@ -19,6 +19,7 @@
 #include "VPlanDominatorTree.h"
 #include "VPlanPatternMatch.h"
 #include "VPlanUtils.h"
+#include "VPlanVerifier.h"
 #include "llvm/ADT/PostOrderIterator.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SetVector.h"
@@ -1439,19 +1440,19 @@ void VPlanTransforms::truncateToMinimalBitwidths(
 }
 
 void VPlanTransforms::optimize(VPlan &Plan) {
-  removeRedundantCanonicalIVs(Plan);
-  removeRedundantInductionCasts(Plan);
+  runPass(removeRedundantCanonicalIVs, Plan);
+  runPass(removeRedundantInductionCasts, Plan);
 
   simplifyRecipes(Plan, Plan.getCanonicalIV()->getScalarType());
-  removeDeadRecipes(Plan);
-  legalizeAndOptimizeInductions(Plan);
-  removeRedundantExpandSCEVRecipes(Plan);
+  runPass(removeDeadRecipes, Plan);
+  runPass(legalizeAndOptimizeInductions, Plan);
+  runPass(removeRedundantExpandSCEVRecipes, Plan);
   simplifyRecipes(Plan, Plan.getCanonicalIV()->getScalarType());
-  removeDeadRecipes(Plan);
+  runPass(removeDeadRecipes, Plan);
 
-  createAndOptimizeReplicateRegions(Plan);
-  mergeBlocksIntoPredecessors(Plan);
-  licm(Plan);
+  runPass(createAndOptimizeReplicateRegions, Plan);
+  runPass(mergeBlocksIntoPredecessors, Plan);
+  runPass(licm, Plan);
 }
 
 // Add a VPActiveLaneMaskPHIRecipe and related recipes to \p Plan and replace
@@ -1871,7 +1872,8 @@ bool VPlanTransforms::tryAddExplicitVectorLength(
 }
 
 void VPlanTransforms::dropPoisonGeneratingRecipes(
-    VPlan &Plan, function_ref<bool(BasicBlock *)> BlockNeedsPredication) {
+    VPlan &Plan,
+    const std::function<bool(BasicBlock *)> &BlockNeedsPredication) {
   // Collect recipes in the backward slice of `Root` that may generate a poison
   // value that is used after vectorization.
   SmallPtrSet<VPRecipeBase *, 16> Visited;
@@ -1971,7 +1973,7 @@ void VPlanTransforms::createInterleaveGroups(
     VPlan &Plan,
     const SmallPtrSetImpl<const InterleaveGroup<Instruction> *>
         &InterleaveGroups,
-    VPRecipeBuilder &RecipeBuilder, bool ScalarEpilogueAllowed) {
+    VPRecipeBuilder &RecipeBuilder, const bool &ScalarEpilogueAllowed) {
   if (InterleaveGroups.empty())
     return;
 

llvm/lib/Transforms/Vectorize/VPlanTransforms.h

@@ -14,7 +14,9 @@
 #define LLVM_TRANSFORMS_VECTORIZE_VPLANTRANSFORMS_H
 
 #include "VPlan.h"
+#include "VPlanVerifier.h"
 #include "llvm/ADT/STLFunctionalExtras.h"
+#include "llvm/Support/CommandLine.h"
 
 namespace llvm {
 
@@ -27,7 +29,29 @@ class TargetLibraryInfo;
 class VPBuilder;
 class VPRecipeBuilder;
 
+extern cl::opt<bool> VerifyEachVPlan;
+
 struct VPlanTransforms {
+  /// Helper to run a VPlan transform \p Transform on \p VPlan, forwarding extra
+  /// arguments to the transform. Returns the boolean returned by the transform.
+  template <typename... ArgsTy>
+  static bool runPass(bool (*Transform)(VPlan &, ArgsTy...), VPlan &Plan,
+                      typename std::remove_reference<ArgsTy>::type &...Args) {
+    bool Res = Transform(Plan, Args...);
+    if (VerifyEachVPlan)
+      verifyVPlanIsValid(Plan);
+    return Res;
+  }
+  /// Helper to run a VPlan transform \p Transform on \p VPlan, forwarding extra
+  /// arguments to the transform.
+  template <typename... ArgsTy>
+  static void runPass(void (*Fn)(VPlan &, ArgsTy...), VPlan &Plan,
+                      typename std::remove_reference<ArgsTy>::type &...Args) {
+    Fn(Plan, Args...);
+    if (VerifyEachVPlan)
+      verifyVPlanIsValid(Plan);
+  }
+
   /// Replaces the VPInstructions in \p Plan with corresponding
   /// widen recipes.
   static void
@@ -100,7 +124,8 @@ struct VPlanTransforms {
   /// TODO: Replace BlockNeedsPredication callback with retrieving info from
   ///       VPlan directly.
   static void dropPoisonGeneratingRecipes(
-      VPlan &Plan, function_ref<bool(BasicBlock *)> BlockNeedsPredication);
+      VPlan &Plan,
+      const std::function<bool(BasicBlock *)> &BlockNeedsPredication);
 
   /// Add a VPEVLBasedIVPHIRecipe and related recipes to \p Plan and
   /// replaces all uses except the canonical IV increment of
@@ -119,7 +144,7 @@ struct VPlanTransforms {
       VPlan &Plan,
       const SmallPtrSetImpl<const InterleaveGroup<Instruction> *>
           &InterleaveGroups,
-      VPRecipeBuilder &RecipeBuilder, bool ScalarEpilogueAllowed);
+      VPRecipeBuilder &RecipeBuilder, const bool &ScalarEpilogueAllowed);
 
   /// Remove dead recipes from \p Plan.
   static void removeDeadRecipes(VPlan &Plan);