llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp - llvm-project.git - Git at Google

 //===-- VPlanVerifier.cpp -------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// This file defines the class VPlanVerifier, which contains utility functions
 /// to check the consistency and invariants of a VPlan.
 ///
 //===----------------------------------------------------------------------===//

 #include "VPlanVerifier.h"
 #include "VPlan.h"
 #include "VPlanCFG.h"
 #include "VPlanDominatorTree.h"
 #include "llvm/ADT/DepthFirstIterator.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/TypeSwitch.h"
 #include "llvm/Support/CommandLine.h"

 #define DEBUG_TYPE "loop-vectorize"

 using namespace llvm;

 namespace {
 class VPlanVerifier {
   const VPDominatorTree &VPDT;

   SmallPtrSet<BasicBlock *, 8> WrappedIRBBs;

   // Verify that phi-like recipes are at the beginning of \p VPBB, with no
   // other recipes in between. Also check that only header blocks contain
   // VPHeaderPHIRecipes.
   bool verifyPhiRecipes(const VPBasicBlock *VPBB);

   /// Verify that \p EVL is used correctly. The user must be either in
   /// EVL-based recipes as a last operand or VPInstruction::Add which is
   /// incoming value into EVL's recipe.
   bool verifyEVLRecipe(const VPInstruction &EVL) const;

   bool verifyVPBasicBlock(const VPBasicBlock *VPBB);

   bool verifyBlock(const VPBlockBase *VPB);

   /// Helper function that verifies the CFG invariants of the VPBlockBases
   /// within
   /// \p Region. Checks in this function are generic for VPBlockBases. They are
   /// not specific for VPBasicBlocks or VPRegionBlocks.
   bool verifyBlocksInRegion(const VPRegionBlock *Region);

   /// Verify the CFG invariants of VPRegionBlock \p Region and its nested
   /// VPBlockBases. Do not recurse inside nested VPRegionBlocks.
   bool verifyRegion(const VPRegionBlock *Region);

   /// Verify the CFG invariants of VPRegionBlock \p Region and its nested
   /// VPBlockBases. Recurse inside nested VPRegionBlocks.
   bool verifyRegionRec(const VPRegionBlock *Region);

 public:
   VPlanVerifier(VPDominatorTree &VPDT) : VPDT(VPDT) {}

   bool verify(const VPlan &Plan);
 };
 } // namespace

 bool VPlanVerifier::verifyPhiRecipes(const VPBasicBlock *VPBB) {
   auto RecipeI = VPBB->begin();
   auto End = VPBB->end();
   unsigned NumActiveLaneMaskPhiRecipes = 0;
   const VPRegionBlock *ParentR = VPBB->getParent();
   bool IsHeaderVPBB = ParentR && !ParentR->isReplicator() &&
                       ParentR->getEntryBasicBlock() == VPBB;
   while (RecipeI != End && RecipeI->isPhi()) {
     if (isa<VPActiveLaneMaskPHIRecipe>(RecipeI))
       NumActiveLaneMaskPhiRecipes++;

     if (IsHeaderVPBB && !isa<VPHeaderPHIRecipe, VPWidenPHIRecipe>(*RecipeI)) {
       errs() << "Found non-header PHI recipe in header VPBB";
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
       errs() << ": ";
       RecipeI->dump();
 #endif
       return false;
     }

     if (!IsHeaderVPBB && isa<VPHeaderPHIRecipe>(*RecipeI)) {
       errs() << "Found header PHI recipe in non-header VPBB";
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
       errs() << ": ";
       RecipeI->dump();
 #endif
       return false;
     }

     RecipeI++;
   }

   if (NumActiveLaneMaskPhiRecipes > 1) {
     errs() << "There should be no more than one VPActiveLaneMaskPHIRecipe";
     return false;
   }

   while (RecipeI != End) {
     if (RecipeI->isPhi() && !isa<VPBlendRecipe>(&*RecipeI)) {
       errs() << "Found phi-like recipe after non-phi recipe";

 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
       errs() << ": ";
       RecipeI->dump();
       errs() << "after\n";
       std::prev(RecipeI)->dump();
 #endif
       return false;
     }
     RecipeI++;
   }
   return true;
 }

 bool VPlanVerifier::verifyEVLRecipe(const VPInstruction &EVL) const {
   if (EVL.getOpcode() != VPInstruction::ExplicitVectorLength) {
     errs() << "verifyEVLRecipe should only be called on "
               "VPInstruction::ExplicitVectorLength\n";
     return false;
   }
   auto VerifyEVLUse = [&](const VPRecipeBase &R,
                           const unsigned ExpectedIdx) -> bool {
     SmallVector<const VPValue *> Ops(R.operands());
     unsigned UseCount = count(Ops, &EVL);
     if (UseCount != 1 || Ops[ExpectedIdx] != &EVL) {
       errs() << "EVL is used as non-last operand in EVL-based recipe\n";
       return false;
     }
     return true;
   };
   for (const VPUser *U : EVL.users()) {
     if (!TypeSwitch<const VPUser *, bool>(U)
              .Case<VPWidenStoreEVLRecipe>([&](const VPWidenStoreEVLRecipe *S) {
                return VerifyEVLUse(*S, 2);
              })
              .Case<VPWidenLoadEVLRecipe>([&](const VPWidenLoadEVLRecipe *L) {
                return VerifyEVLUse(*L, 1);
              })
              .Case<VPWidenEVLRecipe>([&](const VPWidenEVLRecipe *W) {
                return VerifyEVLUse(
                    *W, Instruction::isUnaryOp(W->getOpcode()) ? 1 : 2);
              })
              .Case<VPReductionEVLRecipe>([&](const VPReductionEVLRecipe *R) {
                return VerifyEVLUse(*R, 2);
              })
              .Case<VPScalarCastRecipe>(
                  [&](const VPScalarCastRecipe *S) { return true; })
              .Case<VPInstruction>([&](const VPInstruction *I) {
                if (I->getOpcode() != Instruction::Add) {
                  errs()
                      << "EVL is used as an operand in non-VPInstruction::Add\n";
                  return false;
                }
                if (I->getNumUsers() != 1) {
                  errs() << "EVL is used in VPInstruction:Add with multiple "
                            "users\n";
                  return false;
                }
                if (!isa<VPEVLBasedIVPHIRecipe>(*I->users().begin())) {
                  errs() << "Result of VPInstruction::Add with EVL operand is "
                            "not used by VPEVLBasedIVPHIRecipe\n";
                  return false;
                }
                return true;
              })
              .Default([&](const VPUser *U) {
                errs() << "EVL has unexpected user\n";
                return false;
              })) {
       return false;
     }
   }
   return true;
 }

 bool VPlanVerifier::verifyVPBasicBlock(const VPBasicBlock *VPBB) {
   if (!verifyPhiRecipes(VPBB))
     return false;

   // Verify that defs in VPBB dominate all their uses. The current
   // implementation is still incomplete.
   DenseMap<const VPRecipeBase *, unsigned> RecipeNumbering;
   unsigned Cnt = 0;
   for (const VPRecipeBase &R : *VPBB)
     RecipeNumbering[&R] = Cnt++;

   for (const VPRecipeBase &R : *VPBB) {
     if (isa<VPIRInstruction>(&R) ^ isa<VPIRBasicBlock>(VPBB)) {
       errs() << "VPIRInstructions ";
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
       R.dump();
       errs() << " ";
 #endif
       errs() << "not in a VPIRBasicBlock!\n";
       return false;
     }
     for (const VPValue *V : R.definedValues()) {
       for (const VPUser *U : V->users()) {
         auto *UI = dyn_cast<VPRecipeBase>(U);
         // TODO: check dominance of incoming values for phis properly.
         if (!UI ||
             isa<VPHeaderPHIRecipe, VPWidenPHIRecipe, VPPredInstPHIRecipe>(UI))
           continue;

         // If the user is in the same block, check it comes after R in the
         // block.
         if (UI->getParent() == VPBB) {
           if (RecipeNumbering[UI] < RecipeNumbering[&R]) {
             errs() << "Use before def!\n";
             return false;
           }
           continue;
         }

         if (!VPDT.dominates(VPBB, UI->getParent())) {
           errs() << "Use before def!\n";
           return false;
         }
       }
     }
     if (const auto *EVL = dyn_cast<VPInstruction>(&R)) {
       if (EVL->getOpcode() == VPInstruction::ExplicitVectorLength &&
           !verifyEVLRecipe(*EVL)) {
         errs() << "EVL VPValue is not used correctly\n";
         return false;
       }
     }
   }

   auto *IRBB = dyn_cast<VPIRBasicBlock>(VPBB);
   if (!IRBB)
     return true;

   if (!WrappedIRBBs.insert(IRBB->getIRBasicBlock()).second) {
     errs() << "Same IR basic block used by multiple wrapper blocks!\n";
     return false;
   }

   VPBlockBase *MiddleBB =
       IRBB->getPlan()->getVectorLoopRegion()->getSingleSuccessor();
   if (IRBB != IRBB->getPlan()->getPreheader() &&
       IRBB->getSinglePredecessor() != MiddleBB) {
     errs() << "VPIRBasicBlock can only be used as pre-header or a successor of "
               "middle-block at the moment!\n";
     return false;
   }
   return true;
 }

 /// Utility function that checks whether \p VPBlockVec has duplicate
 /// VPBlockBases.
 static bool hasDuplicates(const SmallVectorImpl<VPBlockBase *> &VPBlockVec) {
   SmallDenseSet<const VPBlockBase *, 8> VPBlockSet;
   for (const auto *Block : VPBlockVec) {
     if (!VPBlockSet.insert(Block).second)
       return true;
   }
   return false;
 }

 bool VPlanVerifier::verifyBlock(const VPBlockBase *VPB) {
   auto *VPBB = dyn_cast<VPBasicBlock>(VPB);
   // Check block's condition bit.
   if (VPB->getNumSuccessors() > 1 ||
       (VPBB && VPBB->getParent() && VPBB->isExiting() &&
        !VPBB->getParent()->isReplicator())) {
     if (!VPBB || !VPBB->getTerminator()) {
       errs() << "Block has multiple successors but doesn't "
                 "have a proper branch recipe!\n";
       return false;
     }
   } else {
     if (VPBB && VPBB->getTerminator()) {
       errs() << "Unexpected branch recipe!\n";
       return false;
     }
   }

   // Check block's successors.
   const auto &Successors = VPB->getSuccessors();
   // There must be only one instance of a successor in block's successor list.
   // TODO: This won't work for switch statements.
   if (hasDuplicates(Successors)) {
     errs() << "Multiple instances of the same successor.\n";
     return false;
   }

   for (const VPBlockBase *Succ : Successors) {
     // There must be a bi-directional link between block and successor.
     const auto &SuccPreds = Succ->getPredecessors();
     if (!is_contained(SuccPreds, VPB)) {
       errs() << "Missing predecessor link.\n";
       return false;
     }
   }

   // Check block's predecessors.
   const auto &Predecessors = VPB->getPredecessors();
   // There must be only one instance of a predecessor in block's predecessor
   // list.
   // TODO: This won't work for switch statements.
   if (hasDuplicates(Predecessors)) {
     errs() << "Multiple instances of the same predecessor.\n";
     return false;
   }

   for (const VPBlockBase *Pred : Predecessors) {
     // Block and predecessor must be inside the same region.
     if (Pred->getParent() != VPB->getParent()) {
       errs() << "Predecessor is not in the same region.\n";
       return false;
     }

     // There must be a bi-directional link between block and predecessor.
     const auto &PredSuccs = Pred->getSuccessors();
     if (!is_contained(PredSuccs, VPB)) {
       errs() << "Missing successor link.\n";
       return false;
     }
   }
   return !VPBB || verifyVPBasicBlock(VPBB);
 }

 bool VPlanVerifier::verifyBlocksInRegion(const VPRegionBlock *Region) {
   for (const VPBlockBase *VPB : vp_depth_first_shallow(Region->getEntry())) {
     // Check block's parent.
     if (VPB->getParent() != Region) {
       errs() << "VPBlockBase has wrong parent\n";
       return false;
     }

     if (!verifyBlock(VPB))
       return false;
   }
   return true;
 }

 bool VPlanVerifier::verifyRegion(const VPRegionBlock *Region) {
   const VPBlockBase *Entry = Region->getEntry();
   const VPBlockBase *Exiting = Region->getExiting();

   // Entry and Exiting shouldn't have any predecessor/successor, respectively.
   if (Entry->getNumPredecessors() != 0) {
     errs() << "region entry block has predecessors\n";
     return false;
   }
   if (Exiting->getNumSuccessors() != 0) {
     errs() << "region exiting block has successors\n";
     return false;
   }

   return verifyBlocksInRegion(Region);
 }

 bool VPlanVerifier::verifyRegionRec(const VPRegionBlock *Region) {
   // Recurse inside nested regions and check all blocks inside the region.
   return verifyRegion(Region) &&
          all_of(vp_depth_first_shallow(Region->getEntry()),
                 [this](const VPBlockBase *VPB) {
                   const auto *SubRegion = dyn_cast<VPRegionBlock>(VPB);
                   return !SubRegion || verifyRegionRec(SubRegion);
                 });
 }

 bool VPlanVerifier::verify(const VPlan &Plan) {
   if (any_of(vp_depth_first_shallow(Plan.getEntry()),
              [this](const VPBlockBase *VPB) { return !verifyBlock(VPB); }))
     return false;

   const VPRegionBlock *TopRegion = Plan.getVectorLoopRegion();
   if (!verifyRegionRec(TopRegion))
     return false;

   if (TopRegion->getParent()) {
     errs() << "VPlan Top Region should have no parent.\n";
     return false;
   }

   const VPBasicBlock *Entry = dyn_cast<VPBasicBlock>(TopRegion->getEntry());
   if (!Entry) {
     errs() << "VPlan entry block is not a VPBasicBlock\n";
     return false;
   }

   if (!isa<VPCanonicalIVPHIRecipe>(&*Entry->begin())) {
     errs() << "VPlan vector loop header does not start with a "
               "VPCanonicalIVPHIRecipe\n";
     return false;
   }

   const VPBasicBlock *Exiting = dyn_cast<VPBasicBlock>(TopRegion->getExiting());
   if (!Exiting) {
     errs() << "VPlan exiting block is not a VPBasicBlock\n";
     return false;
   }

   if (Exiting->empty()) {
     errs() << "VPlan vector loop exiting block must end with BranchOnCount or "
               "BranchOnCond VPInstruction but is empty\n";
     return false;
   }

   auto *LastInst = dyn_cast<VPInstruction>(std::prev(Exiting->end()));
   if (!LastInst || (LastInst->getOpcode() != VPInstruction::BranchOnCount &&
                     LastInst->getOpcode() != VPInstruction::BranchOnCond)) {
     errs() << "VPlan vector loop exit must end with BranchOnCount or "
               "BranchOnCond VPInstruction\n";
     return false;
   }

   for (const auto &KV : Plan.getLiveOuts())
     if (KV.second->getNumOperands() != 1) {
       errs() << "live outs must have a single operand\n";
       return false;
     }

   return true;
 }

 bool llvm::verifyVPlanIsValid(const VPlan &Plan) {
   VPDominatorTree VPDT;
   VPDT.recalculate(const_cast<VPlan &>(Plan));
   VPlanVerifier Verifier(VPDT);
   return Verifier.verify(Plan);
 }
	//===-- VPlanVerifier.cpp -------------------------------------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//
	///
	/// \file
	/// This file defines the class VPlanVerifier, which contains utility functions
	/// to check the consistency and invariants of a VPlan.
	///
	//===----------------------------------------------------------------------===//

	#include "VPlanVerifier.h"
	#include "VPlan.h"
	#include "VPlanCFG.h"
	#include "VPlanDominatorTree.h"
	#include "llvm/ADT/DepthFirstIterator.h"
	#include "llvm/ADT/SmallPtrSet.h"
	#include "llvm/ADT/TypeSwitch.h"
	#include "llvm/Support/CommandLine.h"

	#define DEBUG_TYPE "loop-vectorize"

	using namespace llvm;

	namespace {
	class VPlanVerifier {
	const VPDominatorTree &VPDT;

	SmallPtrSet<BasicBlock *, 8> WrappedIRBBs;

	// Verify that phi-like recipes are at the beginning of \p VPBB, with no
	// other recipes in between. Also check that only header blocks contain
	// VPHeaderPHIRecipes.
	bool verifyPhiRecipes(const VPBasicBlock *VPBB);

	/// Verify that \p EVL is used correctly. The user must be either in
	/// EVL-based recipes as a last operand or VPInstruction::Add which is
	/// incoming value into EVL's recipe.
	bool verifyEVLRecipe(const VPInstruction &EVL) const;

	bool verifyVPBasicBlock(const VPBasicBlock *VPBB);

	bool verifyBlock(const VPBlockBase *VPB);

	/// Helper function that verifies the CFG invariants of the VPBlockBases
	/// within
	/// \p Region. Checks in this function are generic for VPBlockBases. They are
	/// not specific for VPBasicBlocks or VPRegionBlocks.
	bool verifyBlocksInRegion(const VPRegionBlock *Region);

	/// Verify the CFG invariants of VPRegionBlock \p Region and its nested
	/// VPBlockBases. Do not recurse inside nested VPRegionBlocks.
	bool verifyRegion(const VPRegionBlock *Region);

	/// Verify the CFG invariants of VPRegionBlock \p Region and its nested
	/// VPBlockBases. Recurse inside nested VPRegionBlocks.
	bool verifyRegionRec(const VPRegionBlock *Region);

	public:
	VPlanVerifier(VPDominatorTree &VPDT) : VPDT(VPDT) {}

	bool verify(const VPlan &Plan);
	};
	} // namespace

	bool VPlanVerifier::verifyPhiRecipes(const VPBasicBlock *VPBB) {
	auto RecipeI = VPBB->begin();
	auto End = VPBB->end();
	unsigned NumActiveLaneMaskPhiRecipes = 0;
	const VPRegionBlock *ParentR = VPBB->getParent();
	bool IsHeaderVPBB = ParentR && !ParentR->isReplicator() &&
	ParentR->getEntryBasicBlock() == VPBB;
	while (RecipeI != End && RecipeI->isPhi()) {
	if (isa<VPActiveLaneMaskPHIRecipe>(RecipeI))
	NumActiveLaneMaskPhiRecipes++;

	if (IsHeaderVPBB && !isa<VPHeaderPHIRecipe, VPWidenPHIRecipe>(*RecipeI)) {
	errs() << "Found non-header PHI recipe in header VPBB";
	#if !defined(NDEBUG) \|\| defined(LLVM_ENABLE_DUMP)
	errs() << ": ";
	RecipeI->dump();
	#endif
	return false;
	}

	if (!IsHeaderVPBB && isa<VPHeaderPHIRecipe>(*RecipeI)) {
	errs() << "Found header PHI recipe in non-header VPBB";
	#if !defined(NDEBUG) \|\| defined(LLVM_ENABLE_DUMP)
	errs() << ": ";
	RecipeI->dump();
	#endif
	return false;
	}

	RecipeI++;
	}

	if (NumActiveLaneMaskPhiRecipes > 1) {
	errs() << "There should be no more than one VPActiveLaneMaskPHIRecipe";
	return false;
	}

	while (RecipeI != End) {
	if (RecipeI->isPhi() && !isa<VPBlendRecipe>(&*RecipeI)) {
	errs() << "Found phi-like recipe after non-phi recipe";

	#if !defined(NDEBUG) \|\| defined(LLVM_ENABLE_DUMP)
	errs() << ": ";
	RecipeI->dump();
	errs() << "after\n";
	std::prev(RecipeI)->dump();
	#endif
	return false;
	}
	RecipeI++;
	}
	return true;
	}

	bool VPlanVerifier::verifyEVLRecipe(const VPInstruction &EVL) const {
	if (EVL.getOpcode() != VPInstruction::ExplicitVectorLength) {
	errs() << "verifyEVLRecipe should only be called on "
	"VPInstruction::ExplicitVectorLength\n";
	return false;
	}
	auto VerifyEVLUse = [&](const VPRecipeBase &R,
	const unsigned ExpectedIdx) -> bool {
	SmallVector<const VPValue *> Ops(R.operands());
	unsigned UseCount = count(Ops, &EVL);
	if (UseCount != 1 \|\| Ops[ExpectedIdx] != &EVL) {
	errs() << "EVL is used as non-last operand in EVL-based recipe\n";
	return false;
	}
	return true;
	};
	for (const VPUser *U : EVL.users()) {
	if (!TypeSwitch<const VPUser *, bool>(U)
	.Case<VPWidenStoreEVLRecipe>([&](const VPWidenStoreEVLRecipe *S) {
	return VerifyEVLUse(*S, 2);
	})
	.Case<VPWidenLoadEVLRecipe>([&](const VPWidenLoadEVLRecipe *L) {
	return VerifyEVLUse(*L, 1);
	})
	.Case<VPWidenEVLRecipe>([&](const VPWidenEVLRecipe *W) {
	return VerifyEVLUse(
	*W, Instruction::isUnaryOp(W->getOpcode()) ? 1 : 2);
	})
	.Case<VPReductionEVLRecipe>([&](const VPReductionEVLRecipe *R) {
	return VerifyEVLUse(*R, 2);
	})
	.Case<VPScalarCastRecipe>(
	[&](const VPScalarCastRecipe *S) { return true; })
	.Case<VPInstruction>([&](const VPInstruction *I) {
	if (I->getOpcode() != Instruction::Add) {
	errs()
	<< "EVL is used as an operand in non-VPInstruction::Add\n";
	return false;
	}
	if (I->getNumUsers() != 1) {
	errs() << "EVL is used in VPInstruction:Add with multiple "
	"users\n";
	return false;
	}
	if (!isa<VPEVLBasedIVPHIRecipe>(*I->users().begin())) {
	errs() << "Result of VPInstruction::Add with EVL operand is "
	"not used by VPEVLBasedIVPHIRecipe\n";
	return false;
	}
	return true;
	})
	.Default([&](const VPUser *U) {
	errs() << "EVL has unexpected user\n";
	return false;
	})) {
	return false;
	}
	}
	return true;
	}

	bool VPlanVerifier::verifyVPBasicBlock(const VPBasicBlock *VPBB) {
	if (!verifyPhiRecipes(VPBB))
	return false;

	// Verify that defs in VPBB dominate all their uses. The current
	// implementation is still incomplete.
	DenseMap<const VPRecipeBase *, unsigned> RecipeNumbering;
	unsigned Cnt = 0;
	for (const VPRecipeBase &R : *VPBB)
	RecipeNumbering[&R] = Cnt++;

	for (const VPRecipeBase &R : *VPBB) {
	if (isa<VPIRInstruction>(&R) ^ isa<VPIRBasicBlock>(VPBB)) {
	errs() << "VPIRInstructions ";
	#if !defined(NDEBUG) \|\| defined(LLVM_ENABLE_DUMP)
	R.dump();
	errs() << " ";
	#endif
	errs() << "not in a VPIRBasicBlock!\n";
	return false;
	}
	for (const VPValue *V : R.definedValues()) {
	for (const VPUser *U : V->users()) {
	auto *UI = dyn_cast<VPRecipeBase>(U);
	// TODO: check dominance of incoming values for phis properly.
	if (!UI \|\|
	isa<VPHeaderPHIRecipe, VPWidenPHIRecipe, VPPredInstPHIRecipe>(UI))
	continue;

	// If the user is in the same block, check it comes after R in the
	// block.
	if (UI->getParent() == VPBB) {
	if (RecipeNumbering[UI] < RecipeNumbering[&R]) {
	errs() << "Use before def!\n";
	return false;
	}
	continue;
	}

	if (!VPDT.dominates(VPBB, UI->getParent())) {
	errs() << "Use before def!\n";
	return false;
	}
	}
	}
	if (const auto *EVL = dyn_cast<VPInstruction>(&R)) {
	if (EVL->getOpcode() == VPInstruction::ExplicitVectorLength &&
	!verifyEVLRecipe(*EVL)) {
	errs() << "EVL VPValue is not used correctly\n";
	return false;
	}
	}
	}

	auto *IRBB = dyn_cast<VPIRBasicBlock>(VPBB);
	if (!IRBB)
	return true;

	if (!WrappedIRBBs.insert(IRBB->getIRBasicBlock()).second) {
	errs() << "Same IR basic block used by multiple wrapper blocks!\n";
	return false;
	}

	VPBlockBase *MiddleBB =
	IRBB->getPlan()->getVectorLoopRegion()->getSingleSuccessor();
	if (IRBB != IRBB->getPlan()->getPreheader() &&
	IRBB->getSinglePredecessor() != MiddleBB) {
	errs() << "VPIRBasicBlock can only be used as pre-header or a successor of "
	"middle-block at the moment!\n";
	return false;
	}
	return true;
	}

	/// Utility function that checks whether \p VPBlockVec has duplicate
	/// VPBlockBases.
	static bool hasDuplicates(const SmallVectorImpl<VPBlockBase *> &VPBlockVec) {
	SmallDenseSet<const VPBlockBase *, 8> VPBlockSet;
	for (const auto *Block : VPBlockVec) {
	if (!VPBlockSet.insert(Block).second)
	return true;
	}
	return false;
	}

	bool VPlanVerifier::verifyBlock(const VPBlockBase *VPB) {
	auto *VPBB = dyn_cast<VPBasicBlock>(VPB);
	// Check block's condition bit.
	if (VPB->getNumSuccessors() > 1 \|\|
	(VPBB && VPBB->getParent() && VPBB->isExiting() &&
	!VPBB->getParent()->isReplicator())) {
	if (!VPBB \|\| !VPBB->getTerminator()) {
	errs() << "Block has multiple successors but doesn't "
	"have a proper branch recipe!\n";
	return false;
	}
	} else {
	if (VPBB && VPBB->getTerminator()) {
	errs() << "Unexpected branch recipe!\n";
	return false;
	}
	}

	// Check block's successors.
	const auto &Successors = VPB->getSuccessors();
	// There must be only one instance of a successor in block's successor list.
	// TODO: This won't work for switch statements.
	if (hasDuplicates(Successors)) {
	errs() << "Multiple instances of the same successor.\n";
	return false;
	}

	for (const VPBlockBase *Succ : Successors) {
	// There must be a bi-directional link between block and successor.
	const auto &SuccPreds = Succ->getPredecessors();
	if (!is_contained(SuccPreds, VPB)) {
	errs() << "Missing predecessor link.\n";
	return false;
	}
	}

	// Check block's predecessors.
	const auto &Predecessors = VPB->getPredecessors();
	// There must be only one instance of a predecessor in block's predecessor
	// list.
	// TODO: This won't work for switch statements.
	if (hasDuplicates(Predecessors)) {
	errs() << "Multiple instances of the same predecessor.\n";
	return false;
	}

	for (const VPBlockBase *Pred : Predecessors) {
	// Block and predecessor must be inside the same region.
	if (Pred->getParent() != VPB->getParent()) {
	errs() << "Predecessor is not in the same region.\n";
	return false;
	}

	// There must be a bi-directional link between block and predecessor.
	const auto &PredSuccs = Pred->getSuccessors();
	if (!is_contained(PredSuccs, VPB)) {
	errs() << "Missing successor link.\n";
	return false;
	}
	}
	return !VPBB \|\| verifyVPBasicBlock(VPBB);
	}

	bool VPlanVerifier::verifyBlocksInRegion(const VPRegionBlock *Region) {
	for (const VPBlockBase *VPB : vp_depth_first_shallow(Region->getEntry())) {
	// Check block's parent.
	if (VPB->getParent() != Region) {
	errs() << "VPBlockBase has wrong parent\n";
	return false;
	}

	if (!verifyBlock(VPB))
	return false;
	}
	return true;
	}

	bool VPlanVerifier::verifyRegion(const VPRegionBlock *Region) {
	const VPBlockBase *Entry = Region->getEntry();
	const VPBlockBase *Exiting = Region->getExiting();

	// Entry and Exiting shouldn't have any predecessor/successor, respectively.
	if (Entry->getNumPredecessors() != 0) {
	errs() << "region entry block has predecessors\n";
	return false;
	}
	if (Exiting->getNumSuccessors() != 0) {
	errs() << "region exiting block has successors\n";
	return false;
	}

	return verifyBlocksInRegion(Region);
	}

	bool VPlanVerifier::verifyRegionRec(const VPRegionBlock *Region) {
	// Recurse inside nested regions and check all blocks inside the region.
	return verifyRegion(Region) &&
	all_of(vp_depth_first_shallow(Region->getEntry()),
	[this](const VPBlockBase *VPB) {
	const auto *SubRegion = dyn_cast<VPRegionBlock>(VPB);
	return !SubRegion \|\| verifyRegionRec(SubRegion);
	});
	}

	bool VPlanVerifier::verify(const VPlan &Plan) {
	if (any_of(vp_depth_first_shallow(Plan.getEntry()),
	[this](const VPBlockBase *VPB) { return !verifyBlock(VPB); }))
	return false;

	const VPRegionBlock *TopRegion = Plan.getVectorLoopRegion();
	if (!verifyRegionRec(TopRegion))
	return false;

	if (TopRegion->getParent()) {
	errs() << "VPlan Top Region should have no parent.\n";
	return false;
	}

	const VPBasicBlock *Entry = dyn_cast<VPBasicBlock>(TopRegion->getEntry());
	if (!Entry) {
	errs() << "VPlan entry block is not a VPBasicBlock\n";
	return false;
	}

	if (!isa<VPCanonicalIVPHIRecipe>(&*Entry->begin())) {
	errs() << "VPlan vector loop header does not start with a "
	"VPCanonicalIVPHIRecipe\n";
	return false;
	}

	const VPBasicBlock *Exiting = dyn_cast<VPBasicBlock>(TopRegion->getExiting());
	if (!Exiting) {
	errs() << "VPlan exiting block is not a VPBasicBlock\n";
	return false;
	}

	if (Exiting->empty()) {
	errs() << "VPlan vector loop exiting block must end with BranchOnCount or "
	"BranchOnCond VPInstruction but is empty\n";
	return false;
	}

	auto *LastInst = dyn_cast<VPInstruction>(std::prev(Exiting->end()));
	if (!LastInst \|\| (LastInst->getOpcode() != VPInstruction::BranchOnCount &&
	LastInst->getOpcode() != VPInstruction::BranchOnCond)) {
	errs() << "VPlan vector loop exit must end with BranchOnCount or "
	"BranchOnCond VPInstruction\n";
	return false;
	}

	for (const auto &KV : Plan.getLiveOuts())
	if (KV.second->getNumOperands() != 1) {
	errs() << "live outs must have a single operand\n";
	return false;
	}

	return true;
	}

	bool llvm::verifyVPlanIsValid(const VPlan &Plan) {
	VPDominatorTree VPDT;
	VPDT.recalculate(const_cast<VPlan &>(Plan));
	VPlanVerifier Verifier(VPDT);
	return Verifier.verify(Plan);
	}