llvm/lib/IR/UseListOrder.cpp - toolchain/llvm-project - Gitiles

 //===- UseListOrder.cpp - Implement Use List Order functions --------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // Implement use list order functions to modify use-list order and verify it
 // doesn't change after serialization.
 //
 //===----------------------------------------------------------------------===//

 #include "llvm/IR/UseListOrder.h"

 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/AsmParser/Parser.h"
 #include "llvm/Bitcode/ReaderWriter.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/FileUtilities.h"
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/Support/SourceMgr.h"

 #include <random>
 #include <vector>

 #define DEBUG_TYPE "use-list-order"

 using namespace llvm;

 static cl::opt<bool> PreserveBitcodeUseListOrder(
     "preserve-bc-use-list-order",
     cl::desc("Experimental support to preserve bitcode use-list order."),
     cl::init(false), cl::Hidden);

 bool llvm::shouldPreserveBitcodeUseListOrder() {
   return PreserveBitcodeUseListOrder;
 }

 static void shuffleValueUseLists(Value *V, std::minstd_rand0 &Gen,
                                  DenseSet<Value *> &Seen) {
   if (!Seen.insert(V).second)
     return;

   if (auto *C = dyn_cast<Constant>(V))
     if (!isa<GlobalValue>(C))
       for (Value *Op : C->operands())
         shuffleValueUseLists(Op, Gen, Seen);

   if (V->use_empty() || std::next(V->use_begin()) == V->use_end())
     // Nothing to shuffle for 0 or 1 users.
     return;

   // Generate random numbers between 10 and 99, which will line up nicely in
   // debug output.  We're not worried about collisons here.
   DEBUG(dbgs() << "V = "; V->dump());
   std::uniform_int_distribution<short> Dist(10, 99);
   SmallDenseMap<const Use *, short, 16> Order;
   for (const Use &U : V->uses()) {
     auto I = Dist(Gen);
     Order[&U] = I;
     DEBUG(dbgs() << " - order: " << I << ", U = "; U.getUser()->dump());
   }

   DEBUG(dbgs() << " => shuffle\n");
   V->sortUseList(
       [&Order](const Use &L, const Use &R) { return Order[&L] < Order[&R]; });

   DEBUG({
     for (const Use &U : V->uses())
       DEBUG(dbgs() << " - order: " << Order.lookup(&U) << ", U = ";
             U.getUser()->dump());
   });
 }

 void llvm::shuffleUseLists(Module &M, unsigned SeedOffset) {
   DEBUG(dbgs() << "*** shuffle-use-lists ***\n");
   std::minstd_rand0 Gen(std::minstd_rand0::default_seed + SeedOffset);
   DenseSet<Value *> Seen;

   // Shuffle the use-list of each value that would be serialized to an IR file
   // (bitcode or assembly).
   auto shuffle = [&](Value *V) { shuffleValueUseLists(V, Gen, Seen); };

   // Globals.
   for (GlobalVariable &G : M.globals())
     shuffle(&G);
   for (GlobalAlias &A : M.aliases())
     shuffle(&A);
   for (Function &F : M)
     shuffle(&F);

   // Constants used by globals.
   for (GlobalVariable &G : M.globals())
     if (G.hasInitializer())
       shuffle(G.getInitializer());
   for (GlobalAlias &A : M.aliases())
     shuffle(A.getAliasee());
   for (Function &F : M)
     if (F.hasPrefixData())
       shuffle(F.getPrefixData());

   // Function bodies.
   for (Function &F : M) {
     for (Argument &A : F.args())
       shuffle(&A);
     for (BasicBlock &BB : F)
       shuffle(&BB);
     for (BasicBlock &BB : F)
       for (Instruction &I : BB)
         shuffle(&I);

     // Constants used by instructions.
     for (BasicBlock &BB : F)
       for (Instruction &I : BB)
         for (Value *Op : I.operands())
           if ((isa<Constant>(Op) && !isa<GlobalValue>(*Op)) ||
               isa<InlineAsm>(Op))
             shuffle(Op);
   }

   DEBUG(dbgs() << "\n");
 }

 namespace {

 struct TempFile {
   std::string Filename;
   FileRemover Remover;
   bool init(const std::string &Ext);
   bool writeBitcode(const Module &M) const;
   bool writeAssembly(const Module &M) const;
   std::unique_ptr<Module> readBitcode(LLVMContext &Context) const;
   std::unique_ptr<Module> readAssembly(LLVMContext &Context) const;
 };

 struct ValueMapping {
   DenseMap<const Value *, unsigned> IDs;
   std::vector<const Value *> Values;

   /// \brief Construct a value mapping for module.
   ///
   /// Creates mapping from every value in \c M to an ID.  This mapping includes
   /// un-referencable values.
   ///
   /// Every \a Value that gets serialized in some way should be represented
   /// here.  The order needs to be deterministic, but it's unnecessary to match
   /// the value-ids in the bitcode writer.
   ///
   /// All constants that are referenced by other values are included in the
   /// mapping, but others -- which wouldn't be serialized -- are not.
   ValueMapping(const Module &M);

   /// \brief Map a value.
   ///
   /// Maps a value.  If it's a constant, maps all of its operands first.
   void map(const Value *V);
   unsigned lookup(const Value *V) const { return IDs.lookup(V); }
 };

 } // end namespace

 bool TempFile::init(const std::string &Ext) {
   SmallVector<char, 64> Vector;
   DEBUG(dbgs() << " - create-temp-file\n");
   if (auto EC = sys::fs::createTemporaryFile("use-list-order", Ext, Vector)) {
     DEBUG(dbgs() << "error: " << EC.message() << "\n");
     return true;
   }
   assert(!Vector.empty());

   Filename.assign(Vector.data(), Vector.data() + Vector.size());
   Remover.setFile(Filename);
   DEBUG(dbgs() << " - filename = " << Filename << "\n");
   return false;
 }

 bool TempFile::writeBitcode(const Module &M) const {
   DEBUG(dbgs() << " - write bitcode\n");
   std::string ErrorInfo;
   raw_fd_ostream OS(Filename.c_str(), ErrorInfo, sys::fs::F_None);
   if (!ErrorInfo.empty()) {
     DEBUG(dbgs() << "error: " << ErrorInfo << "\n");
     return true;
   }

   WriteBitcodeToFile(&M, OS);
   return false;
 }

 bool TempFile::writeAssembly(const Module &M) const {
   DEBUG(dbgs() << " - write assembly\n");
   std::string ErrorInfo;
   raw_fd_ostream OS(Filename.c_str(), ErrorInfo, sys::fs::F_Text);
   if (!ErrorInfo.empty()) {
     DEBUG(dbgs() << "error: " << ErrorInfo << "\n");
     return true;
   }

   OS << M;
   return false;
 }

 std::unique_ptr<Module> TempFile::readBitcode(LLVMContext &Context) const {
   DEBUG(dbgs() << " - read bitcode\n");
   ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOr =
       MemoryBuffer::getFile(Filename);
   if (!BufferOr) {
     DEBUG(dbgs() << "error: " << BufferOr.getError().message() << "\n");
     return nullptr;
   }

   std::unique_ptr<MemoryBuffer> Buffer = std::move(BufferOr.get());
   ErrorOr<Module *> ModuleOr = parseBitcodeFile(Buffer.release(), Context);
   if (!ModuleOr) {
     DEBUG(dbgs() << "error: " << ModuleOr.getError().message() << "\n");
     return nullptr;
   }
   return std::unique_ptr<Module>(ModuleOr.get());
 }

 std::unique_ptr<Module> TempFile::readAssembly(LLVMContext &Context) const {
   DEBUG(dbgs() << " - read assembly\n");
   SMDiagnostic Err;
   std::unique_ptr<Module> M(ParseAssemblyFile(Filename, Err, Context));
   if (!M.get())
     DEBUG(dbgs() << "error: "; Err.print("verify-use-list-order", dbgs()));
   return M;
 }

 ValueMapping::ValueMapping(const Module &M) {
   // Every value should be mapped, including things like void instructions and
   // basic blocks that are kept out of the ValueEnumerator.
   //
   // The current mapping order makes it easier to debug the tables.  It happens
   // to be similar to the ID mapping when writing ValueEnumerator, but they
   // aren't (and needn't be) in sync.

   // Globals.
   for (const GlobalVariable &G : M.globals())
     map(&G);
   for (const GlobalAlias &A : M.aliases())
     map(&A);
   for (const Function &F : M)
     map(&F);

   // Constants used by globals.
   for (const GlobalVariable &G : M.globals())
     if (G.hasInitializer())
       map(G.getInitializer());
   for (const GlobalAlias &A : M.aliases())
     map(A.getAliasee());
   for (const Function &F : M)
     if (F.hasPrefixData())
       map(F.getPrefixData());

   // Function bodies.
   for (const Function &F : M) {
     for (const Argument &A : F.args())
       map(&A);
     for (const BasicBlock &BB : F)
       map(&BB);
     for (const BasicBlock &BB : F)
       for (const Instruction &I : BB)
         map(&I);

     // Constants used by instructions.
     for (const BasicBlock &BB : F)
       for (const Instruction &I : BB)
         for (const Value *Op : I.operands())
           if ((isa<Constant>(Op) && !isa<GlobalValue>(*Op)) ||
               isa<InlineAsm>(Op))
             map(Op);
   }
 }

 void ValueMapping::map(const Value *V) {
   if (IDs.lookup(V))
     return;

   if (auto *C = dyn_cast<Constant>(V))
     if (!isa<GlobalValue>(C))
       for (const Value *Op : C->operands())
         map(Op);

   Values.push_back(V);
   IDs[V] = Values.size();
 }

 #ifndef NDEBUG
 static void dumpMapping(const ValueMapping &VM) {
   dbgs() << "value-mapping (size = " << VM.Values.size() << "):\n";
   for (unsigned I = 0, E = VM.Values.size(); I != E; ++I) {
     dbgs() << " - id = " << I << ", value = ";
     VM.Values[I]->dump();
   }
 }

 static void debugValue(const ValueMapping &M, unsigned I, StringRef Desc) {
   const Value *V = M.Values[I];
   dbgs() << " - " << Desc << " value = ";
   V->dump();
   for (const Use &U : V->uses()) {
     dbgs() << "   => use: op = " << U.getOperandNo()
            << ", user-id = " << M.IDs.lookup(U.getUser()) << ", user = ";
     U.getUser()->dump();
   }
 }

 static void debugUserMismatch(const ValueMapping &L, const ValueMapping &R,
                               unsigned I) {
   dbgs() << " - fail: user mismatch: ID = " << I << "\n";
   debugValue(L, I, "LHS");
   debugValue(R, I, "RHS");

   dbgs() << "\nlhs-";
   dumpMapping(L);
   dbgs() << "\nrhs-";
   dumpMapping(R);
 }

 static void debugSizeMismatch(const ValueMapping &L, const ValueMapping &R) {
   dbgs() << " - fail: map size: " << L.Values.size()
          << " != " << R.Values.size() << "\n";
   dbgs() << "\nlhs-";
   dumpMapping(L);
   dbgs() << "\nrhs-";
   dumpMapping(R);
 }
 #endif

 static bool matches(const ValueMapping &LM, const ValueMapping &RM) {
   DEBUG(dbgs() << "compare value maps\n");
   if (LM.Values.size() != RM.Values.size()) {
     DEBUG(debugSizeMismatch(LM, RM));
     return false;
   }

   // This mapping doesn't include dangling constant users, since those don't
   // get serialized.  However, checking if users are constant and calling
   // isConstantUsed() on every one is very expensive.  Instead, just check if
   // the user is mapped.
   auto skipUnmappedUsers =
       [&](Value::const_use_iterator &U, Value::const_use_iterator E,
           const ValueMapping &M) {
     while (U != E && !M.lookup(U->getUser()))
       ++U;
   };

   // Iterate through all values, and check that both mappings have the same
   // users.
   for (unsigned I = 0, E = LM.Values.size(); I != E; ++I) {
     const Value *L = LM.Values[I];
     const Value *R = RM.Values[I];
     auto LU = L->use_begin(), LE = L->use_end();
     auto RU = R->use_begin(), RE = R->use_end();
     skipUnmappedUsers(LU, LE, LM);
     skipUnmappedUsers(RU, RE, RM);

     while (LU != LE) {
       if (RU == RE) {
         DEBUG(debugUserMismatch(LM, RM, I));
         return false;
       }
       if (LM.lookup(LU->getUser()) != RM.lookup(RU->getUser())) {
         DEBUG(debugUserMismatch(LM, RM, I));
         return false;
       }
       if (LU->getOperandNo() != RU->getOperandNo()) {
         DEBUG(debugUserMismatch(LM, RM, I));
         return false;
       }
       skipUnmappedUsers(++LU, LE, LM);
       skipUnmappedUsers(++RU, RE, RM);
     }
     if (RU != RE) {
       DEBUG(debugUserMismatch(LM, RM, I));
       return false;
     }
   }

   return true;
 }

 bool llvm::verifyBitcodeUseListOrder(const Module &M) {
   DEBUG(dbgs() << "*** verify-use-list-order: bitcode ***\n");
   TempFile F;
   if (F.init("bc"))
     return false;

   if (F.writeBitcode(M))
     return false;

   LLVMContext Context;
   std::unique_ptr<Module> OtherM = F.readBitcode(Context);
   if (!OtherM)
     return false;

   return matches(ValueMapping(M), ValueMapping(*OtherM));
 }

 bool llvm::verifyAssemblyUseListOrder(const Module &M) {
   DEBUG(dbgs() << "*** verify-use-list-order: assembly ***\n");
   TempFile F;
   if (F.init("ll"))
     return false;

   if (F.writeAssembly(M))
     return false;

   LLVMContext Context;
   std::unique_ptr<Module> OtherM = F.readAssembly(Context);
   if (!OtherM)
     return false;

   return matches(ValueMapping(M), ValueMapping(*OtherM));
 }
	//===- UseListOrder.cpp - Implement Use List Order functions --------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// Implement use list order functions to modify use-list order and verify it
	// doesn't change after serialization.
	//
	//===----------------------------------------------------------------------===//

	#include "llvm/IR/UseListOrder.h"

	#include "llvm/ADT/DenseMap.h"
	#include "llvm/ADT/DenseSet.h"
	#include "llvm/AsmParser/Parser.h"
	#include "llvm/Bitcode/ReaderWriter.h"
	#include "llvm/IR/LLVMContext.h"
	#include "llvm/IR/Module.h"
	#include "llvm/Support/CommandLine.h"
	#include "llvm/Support/Debug.h"
	#include "llvm/Support/FileSystem.h"
	#include "llvm/Support/FileUtilities.h"
	#include "llvm/Support/MemoryBuffer.h"
	#include "llvm/Support/SourceMgr.h"

	#include <random>
	#include <vector>

	#define DEBUG_TYPE "use-list-order"

	using namespace llvm;

	static cl::opt<bool> PreserveBitcodeUseListOrder(
	"preserve-bc-use-list-order",
	cl::desc("Experimental support to preserve bitcode use-list order."),
	cl::init(false), cl::Hidden);

	bool llvm::shouldPreserveBitcodeUseListOrder() {
	return PreserveBitcodeUseListOrder;
	}

	static void shuffleValueUseLists(Value *V, std::minstd_rand0 &Gen,
	DenseSet<Value *> &Seen) {
	if (!Seen.insert(V).second)
	return;

	if (auto *C = dyn_cast<Constant>(V))
	if (!isa<GlobalValue>(C))
	for (Value *Op : C->operands())
	shuffleValueUseLists(Op, Gen, Seen);

	if (V->use_empty() \|\| std::next(V->use_begin()) == V->use_end())
	// Nothing to shuffle for 0 or 1 users.
	return;

	// Generate random numbers between 10 and 99, which will line up nicely in
	// debug output. We're not worried about collisons here.
	DEBUG(dbgs() << "V = "; V->dump());
	std::uniform_int_distribution<short> Dist(10, 99);
	SmallDenseMap<const Use *, short, 16> Order;
	for (const Use &U : V->uses()) {
	auto I = Dist(Gen);
	Order[&U] = I;
	DEBUG(dbgs() << " - order: " << I << ", U = "; U.getUser()->dump());
	}

	DEBUG(dbgs() << " => shuffle\n");
	V->sortUseList(
	[&Order](const Use &L, const Use &R) { return Order[&L] < Order[&R]; });

	DEBUG({
	for (const Use &U : V->uses())
	DEBUG(dbgs() << " - order: " << Order.lookup(&U) << ", U = ";
	U.getUser()->dump());
	});
	}

	void llvm::shuffleUseLists(Module &M, unsigned SeedOffset) {
	DEBUG(dbgs() << "* shuffle-use-lists *\n");
	std::minstd_rand0 Gen(std::minstd_rand0::default_seed + SeedOffset);
	DenseSet<Value *> Seen;

	// Shuffle the use-list of each value that would be serialized to an IR file
	// (bitcode or assembly).
	auto shuffle = [&](Value *V) { shuffleValueUseLists(V, Gen, Seen); };

	// Globals.
	for (GlobalVariable &G : M.globals())
	shuffle(&G);
	for (GlobalAlias &A : M.aliases())
	shuffle(&A);
	for (Function &F : M)
	shuffle(&F);

	// Constants used by globals.
	for (GlobalVariable &G : M.globals())
	if (G.hasInitializer())
	shuffle(G.getInitializer());
	for (GlobalAlias &A : M.aliases())
	shuffle(A.getAliasee());
	for (Function &F : M)
	if (F.hasPrefixData())
	shuffle(F.getPrefixData());

	// Function bodies.
	for (Function &F : M) {
	for (Argument &A : F.args())
	shuffle(&A);
	for (BasicBlock &BB : F)
	shuffle(&BB);
	for (BasicBlock &BB : F)
	for (Instruction &I : BB)
	shuffle(&I);

	// Constants used by instructions.
	for (BasicBlock &BB : F)
	for (Instruction &I : BB)
	for (Value *Op : I.operands())
	if ((isa<Constant>(Op) && !isa<GlobalValue>(*Op)) \|\|
	isa<InlineAsm>(Op))
	shuffle(Op);
	}

	DEBUG(dbgs() << "\n");
	}

	namespace {

	struct TempFile {
	std::string Filename;
	FileRemover Remover;
	bool init(const std::string &Ext);
	bool writeBitcode(const Module &M) const;
	bool writeAssembly(const Module &M) const;
	std::unique_ptr<Module> readBitcode(LLVMContext &Context) const;
	std::unique_ptr<Module> readAssembly(LLVMContext &Context) const;
	};

	struct ValueMapping {
	DenseMap<const Value *, unsigned> IDs;
	std::vector<const Value *> Values;

	/// \brief Construct a value mapping for module.
	///
	/// Creates mapping from every value in \c M to an ID. This mapping includes
	/// un-referencable values.
	///
	/// Every \a Value that gets serialized in some way should be represented
	/// here. The order needs to be deterministic, but it's unnecessary to match
	/// the value-ids in the bitcode writer.
	///
	/// All constants that are referenced by other values are included in the
	/// mapping, but others -- which wouldn't be serialized -- are not.
	ValueMapping(const Module &M);

	/// \brief Map a value.
	///
	/// Maps a value. If it's a constant, maps all of its operands first.
	void map(const Value *V);
	unsigned lookup(const Value *V) const { return IDs.lookup(V); }
	};

	} // end namespace

	bool TempFile::init(const std::string &Ext) {
	SmallVector<char, 64> Vector;
	DEBUG(dbgs() << " - create-temp-file\n");
	if (auto EC = sys::fs::createTemporaryFile("use-list-order", Ext, Vector)) {
	DEBUG(dbgs() << "error: " << EC.message() << "\n");
	return true;
	}
	assert(!Vector.empty());

	Filename.assign(Vector.data(), Vector.data() + Vector.size());
	Remover.setFile(Filename);
	DEBUG(dbgs() << " - filename = " << Filename << "\n");
	return false;
	}

	bool TempFile::writeBitcode(const Module &M) const {
	DEBUG(dbgs() << " - write bitcode\n");
	std::string ErrorInfo;
	raw_fd_ostream OS(Filename.c_str(), ErrorInfo, sys::fs::F_None);
	if (!ErrorInfo.empty()) {
	DEBUG(dbgs() << "error: " << ErrorInfo << "\n");
	return true;
	}

	WriteBitcodeToFile(&M, OS);
	return false;
	}

	bool TempFile::writeAssembly(const Module &M) const {
	DEBUG(dbgs() << " - write assembly\n");
	std::string ErrorInfo;
	raw_fd_ostream OS(Filename.c_str(), ErrorInfo, sys::fs::F_Text);
	if (!ErrorInfo.empty()) {
	DEBUG(dbgs() << "error: " << ErrorInfo << "\n");
	return true;
	}

	OS << M;
	return false;
	}

	std::unique_ptr<Module> TempFile::readBitcode(LLVMContext &Context) const {
	DEBUG(dbgs() << " - read bitcode\n");
	ErrorOr<std::unique_ptr<MemoryBuffer>> BufferOr =
	MemoryBuffer::getFile(Filename);
	if (!BufferOr) {
	DEBUG(dbgs() << "error: " << BufferOr.getError().message() << "\n");
	return nullptr;
	}

	std::unique_ptr<MemoryBuffer> Buffer = std::move(BufferOr.get());
	ErrorOr<Module *> ModuleOr = parseBitcodeFile(Buffer.release(), Context);
	if (!ModuleOr) {
	DEBUG(dbgs() << "error: " << ModuleOr.getError().message() << "\n");
	return nullptr;
	}
	return std::unique_ptr<Module>(ModuleOr.get());
	}

	std::unique_ptr<Module> TempFile::readAssembly(LLVMContext &Context) const {
	DEBUG(dbgs() << " - read assembly\n");
	SMDiagnostic Err;
	std::unique_ptr<Module> M(ParseAssemblyFile(Filename, Err, Context));
	if (!M.get())
	DEBUG(dbgs() << "error: "; Err.print("verify-use-list-order", dbgs()));
	return M;
	}

	ValueMapping::ValueMapping(const Module &M) {
	// Every value should be mapped, including things like void instructions and
	// basic blocks that are kept out of the ValueEnumerator.
	//
	// The current mapping order makes it easier to debug the tables. It happens
	// to be similar to the ID mapping when writing ValueEnumerator, but they
	// aren't (and needn't be) in sync.

	// Globals.
	for (const GlobalVariable &G : M.globals())
	map(&G);
	for (const GlobalAlias &A : M.aliases())
	map(&A);
	for (const Function &F : M)
	map(&F);

	// Constants used by globals.
	for (const GlobalVariable &G : M.globals())
	if (G.hasInitializer())
	map(G.getInitializer());
	for (const GlobalAlias &A : M.aliases())
	map(A.getAliasee());
	for (const Function &F : M)
	if (F.hasPrefixData())
	map(F.getPrefixData());

	// Function bodies.
	for (const Function &F : M) {
	for (const Argument &A : F.args())
	map(&A);
	for (const BasicBlock &BB : F)
	map(&BB);
	for (const BasicBlock &BB : F)
	for (const Instruction &I : BB)
	map(&I);

	// Constants used by instructions.
	for (const BasicBlock &BB : F)
	for (const Instruction &I : BB)
	for (const Value *Op : I.operands())
	if ((isa<Constant>(Op) && !isa<GlobalValue>(*Op)) \|\|
	isa<InlineAsm>(Op))
	map(Op);
	}
	}

	void ValueMapping::map(const Value *V) {
	if (IDs.lookup(V))
	return;

	if (auto *C = dyn_cast<Constant>(V))
	if (!isa<GlobalValue>(C))
	for (const Value *Op : C->operands())
	map(Op);

	Values.push_back(V);
	IDs[V] = Values.size();
	}

	#ifndef NDEBUG
	static void dumpMapping(const ValueMapping &VM) {
	dbgs() << "value-mapping (size = " << VM.Values.size() << "):\n";
	for (unsigned I = 0, E = VM.Values.size(); I != E; ++I) {
	dbgs() << " - id = " << I << ", value = ";
	VM.Values[I]->dump();
	}
	}

	static void debugValue(const ValueMapping &M, unsigned I, StringRef Desc) {
	const Value *V = M.Values[I];
	dbgs() << " - " << Desc << " value = ";
	V->dump();
	for (const Use &U : V->uses()) {
	dbgs() << " => use: op = " << U.getOperandNo()
	<< ", user-id = " << M.IDs.lookup(U.getUser()) << ", user = ";
	U.getUser()->dump();
	}
	}

	static void debugUserMismatch(const ValueMapping &L, const ValueMapping &R,
	unsigned I) {
	dbgs() << " - fail: user mismatch: ID = " << I << "\n";
	debugValue(L, I, "LHS");
	debugValue(R, I, "RHS");

	dbgs() << "\nlhs-";
	dumpMapping(L);
	dbgs() << "\nrhs-";
	dumpMapping(R);
	}

	static void debugSizeMismatch(const ValueMapping &L, const ValueMapping &R) {
	dbgs() << " - fail: map size: " << L.Values.size()
	<< " != " << R.Values.size() << "\n";
	dbgs() << "\nlhs-";
	dumpMapping(L);
	dbgs() << "\nrhs-";
	dumpMapping(R);
	}
	#endif

	static bool matches(const ValueMapping &LM, const ValueMapping &RM) {
	DEBUG(dbgs() << "compare value maps\n");
	if (LM.Values.size() != RM.Values.size()) {
	DEBUG(debugSizeMismatch(LM, RM));
	return false;
	}

	// This mapping doesn't include dangling constant users, since those don't
	// get serialized. However, checking if users are constant and calling
	// isConstantUsed() on every one is very expensive. Instead, just check if
	// the user is mapped.
	auto skipUnmappedUsers =
	[&](Value::const_use_iterator &U, Value::const_use_iterator E,
	const ValueMapping &M) {
	while (U != E && !M.lookup(U->getUser()))
	++U;
	};

	// Iterate through all values, and check that both mappings have the same
	// users.
	for (unsigned I = 0, E = LM.Values.size(); I != E; ++I) {
	const Value *L = LM.Values[I];
	const Value *R = RM.Values[I];
	auto LU = L->use_begin(), LE = L->use_end();
	auto RU = R->use_begin(), RE = R->use_end();
	skipUnmappedUsers(LU, LE, LM);
	skipUnmappedUsers(RU, RE, RM);

	while (LU != LE) {
	if (RU == RE) {
	DEBUG(debugUserMismatch(LM, RM, I));
	return false;
	}
	if (LM.lookup(LU->getUser()) != RM.lookup(RU->getUser())) {
	DEBUG(debugUserMismatch(LM, RM, I));
	return false;
	}
	if (LU->getOperandNo() != RU->getOperandNo()) {
	DEBUG(debugUserMismatch(LM, RM, I));
	return false;
	}
	skipUnmappedUsers(++LU, LE, LM);
	skipUnmappedUsers(++RU, RE, RM);
	}
	if (RU != RE) {
	DEBUG(debugUserMismatch(LM, RM, I));
	return false;
	}
	}

	return true;
	}

	bool llvm::verifyBitcodeUseListOrder(const Module &M) {
	DEBUG(dbgs() << "* verify-use-list-order: bitcode *\n");
	TempFile F;
	if (F.init("bc"))
	return false;

	if (F.writeBitcode(M))
	return false;

	LLVMContext Context;
	std::unique_ptr<Module> OtherM = F.readBitcode(Context);
	if (!OtherM)
	return false;

	return matches(ValueMapping(M), ValueMapping(*OtherM));
	}

	bool llvm::verifyAssemblyUseListOrder(const Module &M) {
	DEBUG(dbgs() << "* verify-use-list-order: assembly *\n");
	TempFile F;
	if (F.init("ll"))
	return false;

	if (F.writeAssembly(M))
	return false;

	LLVMContext Context;
	std::unique_ptr<Module> OtherM = F.readAssembly(Context);
	if (!OtherM)
	return false;

	return matches(ValueMapping(M), ValueMapping(*OtherM));
	}