[llvm] r303850 - [GVNSink] GVNSink pass

Zachary Turner via llvm-commits llvm-commits at lists.llvm.org
Fri May 26 18:35:43 PDT 2017


Is this being addressed?

This asserts on MSVC in a debug build because it uses debug iterators that
check this kind of thing.


On Thu, May 25, 2017 at 9:05 AM Benjamin Kramer via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> On Thu, May 25, 2017 at 2:51 PM, James Molloy via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
> > Author: jamesm
> > Date: Thu May 25 07:51:11 2017
> > New Revision: 303850
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=303850&view=rev
> > Log:
> > [GVNSink] GVNSink pass
> >
> > This patch provides an initial prototype for a pass that sinks
> instructions based on GVN information, similar to GVNHoist. It is not yet
> ready for commiting but I've uploaded it to gather some initial thoughts.
> >
> > This pass attempts to sink instructions into successors, reducing static
> > instruction count and enabling if-conversion.
> > We use a variant of global value numbering to decide what can be sunk.
> > Consider:
> >
> > [ %a1 = add i32 %b, 1  ]   [ %c1 = add i32 %d, 1  ]
> > [ %a2 = xor i32 %a1, 1 ]   [ %c2 = xor i32 %c1, 1 ]
> >                  \           /
> >            [ %e = phi i32 %a2, %c2 ]
> >            [ add i32 %e, 4         ]
> >
> > GVN would number %a1 and %c1 differently because they compute different
> > results - the VN of an instruction is a function of its opcode and the
> > transitive closure of its operands. This is the key property for hoisting
> > and CSE.
> >
> > What we want when sinking however is for a numbering that is a function
> of
> > the *uses* of an instruction, which allows us to answer the question "if
> I
> > replace %a1 with %c1, will it contribute in an equivalent way to all
> > successive instructions?". The (new) PostValueTable class in GVN
> provides this
> > mapping.
> >
> > This pass has some shown really impressive improvements especially for
> codesize already on internal benchmarks, so I have high hopes it can
> replace all the sinking logic in SimplifyCFG.
> >
> > Differential revision: https://reviews.llvm.org/D24805
> >
> > Added:
> >     llvm/trunk/lib/Transforms/Scalar/GVNSink.cpp
> >     llvm/trunk/test/Transforms/GVNSink/
> >     llvm/trunk/test/Transforms/GVNSink/dither.ll
> >     llvm/trunk/test/Transforms/GVNSink/indirect-call.ll
> >     llvm/trunk/test/Transforms/GVNSink/sink-common-code.ll
> >     llvm/trunk/test/Transforms/GVNSink/struct.ll
> > Modified:
> >     llvm/trunk/include/llvm/InitializePasses.h
> >     llvm/trunk/include/llvm/Transforms/Scalar.h
> >     llvm/trunk/include/llvm/Transforms/Scalar/GVN.h
> >     llvm/trunk/include/llvm/Transforms/Utils/Local.h
> >     llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp
> >     llvm/trunk/lib/Transforms/Scalar/CMakeLists.txt
> >     llvm/trunk/lib/Transforms/Scalar/Scalar.cpp
> >     llvm/trunk/lib/Transforms/Utils/Local.cpp
> >     llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
> >
> > Modified: llvm/trunk/include/llvm/InitializePasses.h
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/InitializePasses.h?rev=303850&r1=303849&r2=303850&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/include/llvm/InitializePasses.h (original)
> > +++ llvm/trunk/include/llvm/InitializePasses.h Thu May 25 07:51:11 2017
> > @@ -144,6 +144,7 @@ void initializeGCMachineCodeAnalysisPass
> >  void initializeGCModuleInfoPass(PassRegistry&);
> >  void initializeGCOVProfilerLegacyPassPass(PassRegistry&);
> >  void initializeGVNHoistLegacyPassPass(PassRegistry&);
> > +void initializeGVNSinkLegacyPassPass(PassRegistry&);
> >  void initializeGVNLegacyPassPass(PassRegistry&);
> >  void initializeGlobalDCELegacyPassPass(PassRegistry&);
> >  void initializeGlobalMergePass(PassRegistry&);
> >
> > Modified: llvm/trunk/include/llvm/Transforms/Scalar.h
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Scalar.h?rev=303850&r1=303849&r2=303850&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/include/llvm/Transforms/Scalar.h (original)
> > +++ llvm/trunk/include/llvm/Transforms/Scalar.h Thu May 25 07:51:11 2017
> > @@ -356,6 +356,13 @@ FunctionPass *createGVNHoistPass();
> >
> >
> //===----------------------------------------------------------------------===//
> >  //
> > +// GVNSink - This pass uses an "inverted" value numbering to decide the
> > +// similarity of expressions and sinks similar expressions into
> successors.
> > +//
> > +FunctionPass *createGVNSinkPass();
> > +
> >
> +//===----------------------------------------------------------------------===//
> > +//
> >  // MergedLoadStoreMotion - This pass merges loads and stores in
> diamonds. Loads
> >  // are hoisted into the header, while stores sink into the footer.
> >  //
> >
> > Modified: llvm/trunk/include/llvm/Transforms/Scalar/GVN.h
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Scalar/GVN.h?rev=303850&r1=303849&r2=303850&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/include/llvm/Transforms/Scalar/GVN.h (original)
> > +++ llvm/trunk/include/llvm/Transforms/Scalar/GVN.h Thu May 25 07:51:11
> 2017
> > @@ -238,7 +238,12 @@ struct GVNHoistPass : PassInfoMixin<GVNH
> >    /// \brief Run the pass over the function.
> >    PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
> >  };
> > -
> > +/// \brief Uses an "inverted" value numbering to decide the similarity
> of
> > +/// expressions and sinks similar expressions into successors.
> > +struct GVNSinkPass : PassInfoMixin<GVNSinkPass> {
> > +  /// \brief Run the pass over the function.
> > +  PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
> > +};
> >  }
> >
> >  #endif
> >
> > Modified: llvm/trunk/include/llvm/Transforms/Utils/Local.h
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/Local.h?rev=303850&r1=303849&r2=303850&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/include/llvm/Transforms/Utils/Local.h (original)
> > +++ llvm/trunk/include/llvm/Transforms/Utils/Local.h Thu May 25 07:51:11
> 2017
> > @@ -410,6 +410,14 @@ bool recognizeBSwapOrBitReverseIdiom(
> >  void maybeMarkSanitizerLibraryCallNoBuiltin(CallInst *CI,
> >                                              const TargetLibraryInfo
> *TLI);
> >
> >
> +//===----------------------------------------------------------------------===//
> > +//  Transform predicates
> > +//
> > +
> > +/// Given an instruction, is it legal to set operand OpIdx to a
> non-constant
> > +/// value?
> > +bool canReplaceOperandWithVariable(const Instruction *I, unsigned
> OpIdx);
> > +
> >  } // End llvm namespace
> >
> >  #endif
> >
> > Modified: llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp?rev=303850&r1=303849&r2=303850&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp (original)
> > +++ llvm/trunk/lib/Transforms/IPO/PassManagerBuilder.cpp Thu May 25
> 07:51:11 2017
> > @@ -155,6 +155,10 @@ static cl::opt<bool>
> >                               cl::Hidden,
> >                               cl::desc("Enable the simple loop unswitch
> pass."));
> >
> > +static cl::opt<bool> EnableGVNSink(
> > +    "enable-gvn-sink", cl::init(false), cl::Hidden,
> > +    cl::desc("Enable the GVN sinking pass (default = on)"));
> > +
> >  PassManagerBuilder::PassManagerBuilder() {
> >      OptLevel = 2;
> >      SizeLevel = 0;
> > @@ -307,6 +311,11 @@ void PassManagerBuilder::addFunctionSimp
> >    MPM.add(createEarlyCSEPass());              // Catch trivial
> redundancies
> >    if (EnableGVNHoist)
> >      MPM.add(createGVNHoistPass());
> > +  if (EnableGVNSink) {
> > +    MPM.add(createGVNSinkPass());
> > +    MPM.add(createCFGSimplificationPass());
> > +  }
> > +
> >    // Speculative execution if the target has divergent branches;
> otherwise nop.
> >    MPM.add(createSpeculativeExecutionIfHasBranchDivergencePass());
> >    MPM.add(createJumpThreadingPass());         // Thread jumps.
> >
> > Modified: llvm/trunk/lib/Transforms/Scalar/CMakeLists.txt
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/CMakeLists.txt?rev=303850&r1=303849&r2=303850&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Transforms/Scalar/CMakeLists.txt (original)
> > +++ llvm/trunk/lib/Transforms/Scalar/CMakeLists.txt Thu May 25 07:51:11
> 2017
> > @@ -13,6 +13,7 @@ add_llvm_library(LLVMScalarOpts
> >    GuardWidening.cpp
> >    GVN.cpp
> >    GVNHoist.cpp
> > +  GVNSink.cpp
> >    IVUsersPrinter.cpp
> >    InductiveRangeCheckElimination.cpp
> >    IndVarSimplify.cpp
> >
> > Added: llvm/trunk/lib/Transforms/Scalar/GVNSink.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/GVNSink.cpp?rev=303850&view=auto
> >
> ==============================================================================
> > --- llvm/trunk/lib/Transforms/Scalar/GVNSink.cpp (added)
> > +++ llvm/trunk/lib/Transforms/Scalar/GVNSink.cpp Thu May 25 07:51:11 2017
> > @@ -0,0 +1,870 @@
> > +//===- GVNSink.cpp - sink expressions into successors
> -------------------===//
> > +//
> > +//                     The LLVM Compiler Infrastructure
> > +//
> > +// This file is distributed under the University of Illinois Open Source
> > +// License. See LICENSE.TXT for details.
> > +//
> >
> +//===----------------------------------------------------------------------===//
> > +//
> > +/// \file GVNSink.cpp
> > +/// This pass attempts to sink instructions into successors, reducing
> static
> > +/// instruction count and enabling if-conversion.
> > +///
> > +/// We use a variant of global value numbering to decide what can be
> sunk.
> > +/// Consider:
> > +///
> > +/// [ %a1 = add i32 %b, 1  ]   [ %c1 = add i32 %d, 1  ]
> > +/// [ %a2 = xor i32 %a1, 1 ]   [ %c2 = xor i32 %c1, 1 ]
> > +///                  \           /
> > +///            [ %e = phi i32 %a2, %c2 ]
> > +///            [ add i32 %e, 4         ]
> > +///
> > +///
> > +/// GVN would number %a1 and %c1 differently because they compute
> different
> > +/// results - the VN of an instruction is a function of its opcode and
> the
> > +/// transitive closure of its operands. This is the key property for
> hoisting
> > +/// and CSE.
> > +///
> > +/// What we want when sinking however is for a numbering that is a
> function of
> > +/// the *uses* of an instruction, which allows us to answer the
> question "if I
> > +/// replace %a1 with %c1, will it contribute in an equivalent way to all
> > +/// successive instructions?". The PostValueTable class in GVN provides
> this
> > +/// mapping.
> > +///
> >
> +//===----------------------------------------------------------------------===//
> > +
> > +#include "llvm/ADT/DenseMap.h"
> > +#include "llvm/ADT/DenseMapInfo.h"
> > +#include "llvm/ADT/DenseSet.h"
> > +#include "llvm/ADT/Hashing.h"
> > +#include "llvm/ADT/Optional.h"
> > +#include "llvm/ADT/PostOrderIterator.h"
> > +#include "llvm/ADT/SCCIterator.h"
> > +#include "llvm/ADT/SmallPtrSet.h"
> > +#include "llvm/ADT/Statistic.h"
> > +#include "llvm/ADT/StringExtras.h"
> > +#include "llvm/Analysis/GlobalsModRef.h"
> > +#include "llvm/Analysis/MemorySSA.h"
> > +#include "llvm/Analysis/PostDominators.h"
> > +#include "llvm/Analysis/TargetTransformInfo.h"
> > +#include "llvm/Analysis/ValueTracking.h"
> > +#include "llvm/IR/Instructions.h"
> > +#include "llvm/IR/Verifier.h"
> > +#include "llvm/Support/MathExtras.h"
> > +#include "llvm/Transforms/Scalar.h"
> > +#include "llvm/Transforms/Scalar/GVN.h"
> > +#include "llvm/Transforms/Scalar/GVNExpression.h"
> > +#include "llvm/Transforms/Utils/BasicBlockUtils.h"
> > +#include "llvm/Transforms/Utils/Local.h"
> > +#include <unordered_set>
> > +using namespace llvm;
> > +
> > +#define DEBUG_TYPE "gvn-sink"
> > +
> > +STATISTIC(NumRemoved, "Number of instructions removed");
> > +
> > +namespace {
> > +
> > +static bool isMemoryInst(const Instruction *I) {
> > +  return isa<LoadInst>(I) || isa<StoreInst>(I) ||
> > +         (isa<InvokeInst>(I) &&
> !cast<InvokeInst>(I)->doesNotAccessMemory()) ||
> > +         (isa<CallInst>(I) &&
> !cast<CallInst>(I)->doesNotAccessMemory());
> > +}
> > +
> > +/// Iterates through instructions in a set of blocks in reverse order
> from the
> > +/// first non-terminator. For example (assume all blocks have size n):
> > +///   LockstepReverseIterator I([B1, B2, B3]);
> > +///   *I-- = [B1[n], B2[n], B3[n]];
> > +///   *I-- = [B1[n-1], B2[n-1], B3[n-1]];
> > +///   *I-- = [B1[n-2], B2[n-2], B3[n-2]];
> > +///   ...
> > +///
> > +/// It continues until all blocks have been exhausted. Use \c
> getActiveBlocks()
> > +/// to
> > +/// determine which blocks are still going and the order they appear in
> the
> > +/// list returned by operator*.
> > +class LockstepReverseIterator {
> > +  ArrayRef<BasicBlock *> Blocks;
> > +  SmallPtrSet<BasicBlock *, 4> ActiveBlocks;
> > +  SmallVector<Instruction *, 4> Insts;
> > +  bool Fail;
> > +
> > +public:
> > +  LockstepReverseIterator(ArrayRef<BasicBlock *> Blocks) :
> Blocks(Blocks) {
> > +    reset();
> > +  }
> > +
> > +  void reset() {
> > +    Fail = false;
> > +    ActiveBlocks.clear();
> > +    for (BasicBlock *BB : Blocks)
> > +      ActiveBlocks.insert(BB);
> > +    Insts.clear();
> > +    for (BasicBlock *BB : Blocks) {
> > +      if (BB->size() <= 1) {
> > +        // Block wasn't big enough - only contained a terminator.
> > +        ActiveBlocks.erase(BB);
> > +        continue;
> > +      }
> > +      Insts.push_back(BB->getTerminator()->getPrevNode());
> > +    }
> > +    if (Insts.empty())
> > +      Fail = true;
> > +  }
> > +
> > +  bool isValid() const { return !Fail; }
> > +  ArrayRef<Instruction *> operator*() const { return Insts; }
> > +  SmallPtrSet<BasicBlock *, 4> &getActiveBlocks() { return
> ActiveBlocks; }
> > +
> > +  void restrictToBlocks(SmallPtrSetImpl<BasicBlock *> &Blocks) {
> > +    for (auto II = Insts.begin(); II != Insts.end();) {
> > +      if (std::find(Blocks.begin(), Blocks.end(), (*II)->getParent()) ==
> > +          Blocks.end()) {
> > +        ActiveBlocks.erase((*II)->getParent());
> > +        II = Insts.erase(II);
> > +      } else {
> > +        ++II;
> > +      }
> > +    }
> > +  }
> > +
> > +  void operator--() {
> > +    if (Fail)
> > +      return;
> > +    SmallVector<Instruction *, 4> NewInsts;
> > +    for (auto *Inst : Insts) {
> > +      if (Inst == &Inst->getParent()->front())
> > +        ActiveBlocks.erase(Inst->getParent());
> > +      else
> > +        NewInsts.push_back(Inst->getPrevNode());
> > +    }
> > +    if (NewInsts.empty()) {
> > +      Fail = true;
> > +      return;
> > +    }
> > +    Insts = NewInsts;
> > +  }
> > +};
> > +
> >
> +//===----------------------------------------------------------------------===//
> > +
> > +/// Candidate solution for sinking. There may be different ways to
> > +/// sink instructions, differing in the number of instructions sunk,
> > +/// the number of predecessors sunk from and the number of PHIs
> > +/// required.
> > +struct SinkingInstructionCandidate {
> > +  unsigned NumBlocks;
> > +  unsigned NumInstructions;
> > +  unsigned NumPHIs;
> > +  unsigned NumMemoryInsts;
> > +  int Cost = -1;
> > +  SmallVector<BasicBlock *, 4> Blocks;
> > +
> > +  void calculateCost(unsigned NumOrigPHIs, unsigned NumOrigBlocks) {
> > +    unsigned NumExtraPHIs = NumPHIs - NumOrigPHIs;
> > +    unsigned SplitEdgeCost = (NumOrigBlocks > NumBlocks) ? 2 : 0;
> > +    Cost = (NumInstructions * (NumBlocks - 1)) -
> > +           (NumExtraPHIs *
> > +            NumExtraPHIs) // PHIs are expensive, so make sure they're
> worth it.
> > +           - SplitEdgeCost;
> > +  }
> > +  bool operator>=(const SinkingInstructionCandidate &Other) const {
> > +    return Cost >= Other.Cost;
> > +  }
> > +};
> > +
> > +llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
> > +                              const SinkingInstructionCandidate &C) {
> > +  OS << "<Candidate Cost=" << C.Cost << " #Blocks=" << C.NumBlocks
> > +     << " #Insts=" << C.NumInstructions << " #PHIs=" << C.NumPHIs <<
> ">";
> > +  return OS;
> > +}
> > +
> >
> +//===----------------------------------------------------------------------===//
> > +
> > +/// Describes a PHI node that may or may not exist. These track the PHIs
> > +/// that must be created if we sunk a sequence of instructions. It
> provides
> > +/// a hash function for efficient equality comparisons.
> > +class ModelledPHI {
> > +  SmallVector<Value *, 4> Values;
> > +  SmallVector<BasicBlock *, 4> Blocks;
> > +
> > +public:
> > +  ModelledPHI() {}
> > +  ModelledPHI(const PHINode *PN) {
> > +    for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I)
> > +      Blocks.push_back(PN->getIncomingBlock(I));
> > +    std::sort(Blocks.begin(), Blocks.end());
> > +
> > +    // This assumes the PHI is already well-formed and there aren't
> conflicting
> > +    // incoming values for the same block.
> > +    for (auto *B : Blocks)
> > +      Values.push_back(PN->getIncomingValueForBlock(B));
> > +  }
> > +  /// Create a dummy ModelledPHI that will compare unequal to any other
> ModelledPHI
> > +  /// without the same ID.
> > +  /// \note This is specifically for DenseMapInfo - do not use this!
> > +  static ModelledPHI createDummy(unsigned ID) {
> > +    ModelledPHI M;
> > +    M.Values.push_back(reinterpret_cast<Value*>(ID));
> > +    return M;
> > +  }
> > +
> > +  /// Create a PHI from an array of incoming values and incoming blocks.
> > +  template <typename VArray, typename BArray>
> > +  ModelledPHI(const VArray &V, const BArray &B) {
> > +    std::copy(V.begin(), V.end(), std::back_inserter(Values));
> > +    std::copy(B.begin(), B.end(), std::back_inserter(Blocks));
> > +  }
> > +
> > +  /// Create a PHI from [I[OpNum] for I in Insts].
> > +  template <typename BArray>
> > +  ModelledPHI(ArrayRef<Instruction *> Insts, unsigned OpNum, const
> BArray &B) {
> > +    std::copy(B.begin(), B.end(), std::back_inserter(Blocks));
> > +    for (auto *I : Insts)
> > +      Values.push_back(I->getOperand(OpNum));
> > +  }
> > +
> > +  /// Restrict the PHI's contents down to only \c NewBlocks.
> > +  /// \c NewBlocks must be a subset of \c this->Blocks.
> > +  void restrictToBlocks(const SmallPtrSetImpl<BasicBlock *> &NewBlocks)
> {
> > +    auto BI = Blocks.begin();
> > +    auto VI = Values.begin();
> > +    while (BI != Blocks.end()) {
> > +      assert(VI != Values.end());
> > +      if (std::find(NewBlocks.begin(), NewBlocks.end(), *BI) ==
> > +          NewBlocks.end()) {
> > +        BI = Blocks.erase(BI);
> > +        VI = Values.erase(VI);
> > +      } else {
> > +        ++BI;
> > +        ++VI;
> > +      }
> > +    }
> > +    assert(Blocks.size() == NewBlocks.size());
> > +  }
> > +
> > +  ArrayRef<Value *> getValues() const { return Values; }
> > +
> > +  bool areAllIncomingValuesSame() const {
> > +    return all_of(Values, [&](Value *V) { return V == Values[0]; });
> > +  }
> > +  bool areAllIncomingValuesSameType() const {
> > +    return all_of(
> > +        Values, [&](Value *V) { return V->getType() ==
> Values[0]->getType(); });
> > +  }
> > +  bool areAnyIncomingValuesConstant() const {
> > +    return any_of(Values, [&](Value *V) { return isa<Constant>(V); });
> > +  }
> > +  // Hash functor
> > +  unsigned hash() const {
> > +      return (unsigned)hash_combine_range(Values.begin(), Values.end());
> > +  }
> > +  bool operator==(const ModelledPHI &Other) const {
> > +    return Values == Other.Values && Blocks == Other.Blocks;
> > +  }
> > +};
> > +
> > +template <typename ModelledPHI> struct DenseMapInfo {
> > +  static inline ModelledPHI &getEmptyKey() {
> > +    static ModelledPHI Dummy = ModelledPHI::createDummy(0);
> > +    return Dummy;
> > +  }
> > +  static inline ModelledPHI &getTombstoneKey() {
> > +    static ModelledPHI Dummy = ModelledPHI::createDummy(1);
> > +    return Dummy;
> > +  }
> > +  static unsigned getHashValue(const ModelledPHI &V) { return V.hash();
> }
> > +  static bool isEqual(const ModelledPHI &LHS, const ModelledPHI &RHS) {
> > +    return LHS == RHS;
> > +  }
> > +};
> > +
> > +typedef DenseSet<ModelledPHI, DenseMapInfo<ModelledPHI>> ModelledPHISet;
> > +
> >
> +//===----------------------------------------------------------------------===//
> > +//                             ValueTable
> >
> +//===----------------------------------------------------------------------===//
> > +// This is a value number table where the value number is a function of
> the
> > +// *uses* of a value, rather than its operands. Thus, if VN(A) == VN(B)
> we know
> > +// that the program would be equivalent if we replaced A with PHI(A, B).
> >
> +//===----------------------------------------------------------------------===//
> > +
> > +/// A GVN expression describing how an instruction is used. The operands
> > +/// field of BasicExpression is used to store uses, not operands.
> > +///
> > +/// This class also contains fields for discriminators used when
> determining
> > +/// equivalence of instructions with sideeffects.
> > +class InstructionUseExpr : public GVNExpression::BasicExpression {
> > +  unsigned MemoryUseOrder = -1;
> > +  bool Volatile = false;
> > +
> > +public:
> > +  InstructionUseExpr(Instruction *I, ArrayRecycler<Value *> &R,
> > +                     BumpPtrAllocator &A)
> > +      : GVNExpression::BasicExpression(I->getNumUses()) {
> > +    allocateOperands(R, A);
> > +    setOpcode(I->getOpcode());
> > +    setType(I->getType());
> > +
> > +    for (auto &U : I->uses())
> > +      op_push_back(U.getUser());
> > +    std::sort(op_begin(), op_end());
> > +  }
> > +  void setMemoryUseOrder(unsigned MUO) { MemoryUseOrder = MUO; }
> > +  void setVolatile(bool V) { Volatile = V; }
> > +
> > +  virtual hash_code getHashValue() const {
> > +    return hash_combine(GVNExpression::BasicExpression::getHashValue(),
> > +                        MemoryUseOrder, Volatile);
> > +  }
> > +
> > +  template <typename Function> hash_code getHashValue(Function MapFn) {
> > +    hash_code H =
> > +        hash_combine(getOpcode(), getType(), MemoryUseOrder, Volatile);
> > +    for (auto *V : operands())
> > +      H = hash_combine(H, MapFn(V));
> > +    return H;
> > +  }
> > +};
> > +
> > +class ValueTable {
> > +  DenseMap<Value *, uint32_t> ValueNumbering;
> > +  DenseMap<GVNExpression::Expression *, uint32_t> ExpressionNumbering;
> > +  DenseMap<size_t, uint32_t> HashNumbering;
> > +  BumpPtrAllocator Allocator;
> > +  ArrayRecycler<Value *> Recycler;
> > +  uint32_t nextValueNumber;
> > +
> > +  /// Create an expression for I based on its opcode and its uses. If I
> > +  /// touches or reads memory, the expression is also based upon its
> memory
> > +  /// order - see \c getMemoryUseOrder().
> > +  InstructionUseExpr *createExpr(Instruction *I) {
> > +    InstructionUseExpr *E =
> > +        new (Allocator) InstructionUseExpr(I, Recycler, Allocator);
> > +    if (isMemoryInst(I))
> > +      E->setMemoryUseOrder(getMemoryUseOrder(I));
> > +
> > +    if (CmpInst *C = dyn_cast<CmpInst>(I)) {
> > +      CmpInst::Predicate Predicate = C->getPredicate();
> > +      E->setOpcode((C->getOpcode() << 8) | Predicate);
> > +    }
> > +    return E;
> > +  }
> > +
> > +  /// Helper to compute the value number for a memory instruction
> > +  /// (LoadInst/StoreInst), including checking the memory ordering and
> > +  /// volatility.
> > +  template <class Inst> InstructionUseExpr *createMemoryExpr(Inst *I) {
> > +    if (isStrongerThanUnordered(I->getOrdering()) || I->isAtomic())
> > +      return nullptr;
> > +    InstructionUseExpr *E = createExpr(I);
> > +    E->setVolatile(I->isVolatile());
> > +    return E;
> > +  }
> > +
> > +public:
> > +  /// Returns the value number for the specified value, assigning
> > +  /// it a new number if it did not have one before.
> > +  uint32_t lookupOrAdd(Value *V) {
> > +    auto VI = ValueNumbering.find(V);
> > +    if (VI != ValueNumbering.end())
> > +      return VI->second;
> > +
> > +    if (!isa<Instruction>(V)) {
> > +      ValueNumbering[V] = nextValueNumber;
> > +      return nextValueNumber++;
> > +    }
> > +
> > +    Instruction *I = cast<Instruction>(V);
> > +    InstructionUseExpr *exp = nullptr;
> > +    switch (I->getOpcode()) {
> > +    case Instruction::Load:
> > +      exp = createMemoryExpr(cast<LoadInst>(I));
> > +      break;
> > +    case Instruction::Store:
> > +      exp = createMemoryExpr(cast<StoreInst>(I));
> > +      break;
> > +    case Instruction::Call:
> > +    case Instruction::Invoke:
> > +    case Instruction::Add:
> > +    case Instruction::FAdd:
> > +    case Instruction::Sub:
> > +    case Instruction::FSub:
> > +    case Instruction::Mul:
> > +    case Instruction::FMul:
> > +    case Instruction::UDiv:
> > +    case Instruction::SDiv:
> > +    case Instruction::FDiv:
> > +    case Instruction::URem:
> > +    case Instruction::SRem:
> > +    case Instruction::FRem:
> > +    case Instruction::Shl:
> > +    case Instruction::LShr:
> > +    case Instruction::AShr:
> > +    case Instruction::And:
> > +    case Instruction::Or:
> > +    case Instruction::Xor:
> > +    case Instruction::ICmp:
> > +    case Instruction::FCmp:
> > +    case Instruction::Trunc:
> > +    case Instruction::ZExt:
> > +    case Instruction::SExt:
> > +    case Instruction::FPToUI:
> > +    case Instruction::FPToSI:
> > +    case Instruction::UIToFP:
> > +    case Instruction::SIToFP:
> > +    case Instruction::FPTrunc:
> > +    case Instruction::FPExt:
> > +    case Instruction::PtrToInt:
> > +    case Instruction::IntToPtr:
> > +    case Instruction::BitCast:
> > +    case Instruction::Select:
> > +    case Instruction::ExtractElement:
> > +    case Instruction::InsertElement:
> > +    case Instruction::ShuffleVector:
> > +    case Instruction::InsertValue:
> > +    case Instruction::GetElementPtr:
> > +      exp = createExpr(I);
> > +      break;
> > +    default:
> > +      break;
> > +    }
> > +
> > +    if (!exp) {
> > +      ValueNumbering[V] = nextValueNumber;
> > +      return nextValueNumber++;
> > +    }
> > +
> > +    uint32_t e = ExpressionNumbering[exp];
> > +    if (!e) {
> > +      hash_code H = exp->getHashValue([=](Value *V) { return
> lookupOrAdd(V); });
> > +      auto I = HashNumbering.find(H);
> > +      if (I != HashNumbering.end()) {
> > +        e = I->second;
> > +      } else {
> > +        e = nextValueNumber++;
> > +        HashNumbering[H] = e;
> > +        ExpressionNumbering[exp] = e;
> > +      }
> > +    }
> > +    ValueNumbering[V] = e;
> > +    return e;
> > +  }
> > +
> > +  /// Returns the value number of the specified value. Fails if the
> value has
> > +  /// not yet been numbered.
> > +  uint32_t lookup(Value *V) const {
> > +    auto VI = ValueNumbering.find(V);
> > +    assert(VI != ValueNumbering.end() && "Value not numbered?");
> > +    return VI->second;
> > +  }
> > +
> > +  /// Removes all value numberings and resets the value table.
> > +  void clear() {
> > +    ValueNumbering.clear();
> > +    ExpressionNumbering.clear();
> > +    HashNumbering.clear();
> > +    Recycler.clear(Allocator);
> > +    nextValueNumber = 1;
> > +  }
> > +
> > +  ValueTable() : nextValueNumber(1) {}
> > +
> > +  /// \c Inst uses or touches memory. Return an ID describing the
> memory state
> > +  /// at \c Inst such that if getMemoryUseOrder(I1) ==
> getMemoryUseOrder(I2),
> > +  /// the exact same memory operations happen after I1 and I2.
> > +  ///
> > +  /// This is a very hard problem in general, so we use domain-specific
> > +  /// knowledge that we only ever check for equivalence between blocks
> sharing a
> > +  /// single immediate successor that is common, and when determining
> if I1 ==
> > +  /// I2 we will have already determined that next(I1) == next(I2). This
> > +  /// inductive property allows us to simply return the value number of
> the next
> > +  /// instruction that defines memory.
> > +  uint32_t getMemoryUseOrder(Instruction *Inst) {
> > +    auto *BB = Inst->getParent();
> > +    for (auto I = std::next(Inst->getIterator()), E = BB->end();
> > +         I != E && !I->isTerminator(); ++I) {
> > +      if (!isMemoryInst(&*I))
> > +        continue;
> > +      if (isa<LoadInst>(&*I))
> > +        continue;
> > +      CallInst *CI = dyn_cast<CallInst>(&*I);
> > +      if (CI && CI->onlyReadsMemory())
> > +        continue;
> > +      InvokeInst *II = dyn_cast<InvokeInst>(&*I);
> > +      if (II && II->onlyReadsMemory())
> > +        continue;
> > +      return lookupOrAdd(&*I);
> > +    }
> > +    return 0;
> > +  }
> > +};
> > +
> >
> +//===----------------------------------------------------------------------===//
> > +
> > +class GVNSink {
> > +public:
> > +  GVNSink() : VN() {}
> > +  bool run(Function &F) {
> > +    DEBUG(dbgs() << "GVNSink: running on function @" << F.getName() <<
> "\n");
> > +
> > +    unsigned NumSunk = 0;
> > +    ReversePostOrderTraversal<Function*> RPOT(&F);
> > +    for (auto *N : RPOT)
> > +      NumSunk += sinkBB(N);
> > +
> > +    return NumSunk > 0;
> > +  }
> > +
> > +private:
> > +  ValueTable VN;
> > +
> > +  bool isInstructionBlacklisted(Instruction *I) {
> > +    // These instructions may change or break semantics if moved.
> > +    if (isa<PHINode>(I) || I->isEHPad() || isa<AllocaInst>(I) ||
> > +        I->getType()->isTokenTy())
> > +      return true;
> > +    return false;
> > +  }
> > +
> > +  /// The main heuristic function. Analyze the set of instructions
> pointed to by
> > +  /// LRI and return a candidate solution if these instructions can be
> sunk, or
> > +  /// None otherwise.
> > +  Optional<SinkingInstructionCandidate> analyzeInstructionForSinking(
> > +      LockstepReverseIterator &LRI, unsigned &InstNum, unsigned
> &MemoryInstNum,
> > +      ModelledPHISet &NeededPHIs, SmallPtrSetImpl<Value *>
> &PHIContents);
> > +
> > +  /// Create a ModelledPHI for each PHI in BB, adding to PHIs.
> > +  void analyzeInitialPHIs(BasicBlock *BB, ModelledPHISet &PHIs,
> > +                          SmallPtrSetImpl<Value *> &PHIContents) {
> > +    for (auto &I : *BB) {
> > +      auto *PN = dyn_cast<PHINode>(&I);
> > +      if (!PN)
> > +        return;
> > +
> > +      auto MPHI = ModelledPHI(PN);
> > +      PHIs.insert(MPHI);
> > +      for (auto *V : MPHI.getValues())
> > +        PHIContents.insert(V);
> > +    }
> > +  }
> > +
> > +  /// The main instruction sinking driver. Set up state and try and sink
> > +  /// instructions into BBEnd from its predecessors.
> > +  unsigned sinkBB(BasicBlock *BBEnd);
> > +
> > +  /// Perform the actual mechanics of sinking an instruction from
> Blocks into
> > +  /// BBEnd, which is their only successor.
> > +  void sinkLastInstruction(ArrayRef<BasicBlock *> Blocks, BasicBlock
> *BBEnd);
> > +
> > +  /// Remove PHIs that all have the same incoming value.
> > +  void foldPointlessPHINodes(BasicBlock *BB) {
> > +    auto I = BB->begin();
> > +    while (PHINode *PN = dyn_cast<PHINode>(I++)) {
> > +      if (!all_of(PN->incoming_values(),
> > +                  [&](const Value *V) { return V ==
> PN->getIncomingValue(0); }))
> > +        continue;
> > +      if (PN->getIncomingValue(0) != PN)
> > +        PN->replaceAllUsesWith(PN->getIncomingValue(0));
> > +      else
> > +        PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
> > +      PN->eraseFromParent();
> > +    }
> > +  }
> > +};
> > +
> > +Optional<SinkingInstructionCandidate>
> GVNSink::analyzeInstructionForSinking(
> > +  LockstepReverseIterator &LRI, unsigned &InstNum, unsigned
> &MemoryInstNum,
> > +  ModelledPHISet &NeededPHIs, SmallPtrSetImpl<Value *> &PHIContents) {
> > +  auto Insts = *LRI;
> > +  DEBUG(dbgs() << " -- Analyzing instruction set: [\n"; for (auto *I
> > +                                                             : Insts) {
> > +    I->dump();
> > +  } dbgs() << " ]\n";);
> > +
> > +  DenseMap<uint32_t, unsigned> VNums;
> > +  for (auto *I : Insts) {
> > +    uint32_t N = VN.lookupOrAdd(I);
> > +    DEBUG(dbgs() << " VN=" << utohexstr(N) << " for" << *I << "\n");
> > +    if (N == ~0U)
> > +      return None;
> > +    VNums[N]++;
> > +  }
> > +  unsigned VNumToSink =
> > +      std::max_element(VNums.begin(), VNums.end(),
> > +                       [](const std::pair<uint32_t, unsigned> &I,
> > +                          const std::pair<uint32_t, unsigned> &J) {
> > +                         return I.second < J.second;
> > +                       })
> > +          ->first;
> > +
> > +  if (VNums[VNumToSink] == 1)
> > +    // Can't sink anything!
> > +    return None;
> > +
> > +  // Now restrict the number of incoming blocks down to only those with
> > +  // VNumToSink.
> > +  auto &ActivePreds = LRI.getActiveBlocks();
> > +  unsigned InitialActivePredSize = ActivePreds.size();
> > +  SmallVector<Instruction *, 4> NewInsts;
> > +  for (auto *I : Insts) {
> > +    if (VN.lookup(I) != VNumToSink)
> > +      ActivePreds.erase(I->getParent());
> > +    else
> > +      NewInsts.push_back(I);
> > +  }
> > +  for (auto *I : NewInsts)
> > +    if (isInstructionBlacklisted(I))
> > +      return None;
> > +
> > +  // If we've restricted the incoming blocks, restrict all needed PHIs
> also
> > +  // to that set.
> > +  bool RecomputePHIContents = false;
> > +  if (ActivePreds.size() != InitialActivePredSize) {
> > +    ModelledPHISet NewNeededPHIs;
> > +    for (auto P : NeededPHIs) {
> > +      P.restrictToBlocks(ActivePreds);
> > +      NewNeededPHIs.insert(P);
> > +    }
> > +    NeededPHIs = NewNeededPHIs;
> > +    LRI.restrictToBlocks(ActivePreds);
> > +    RecomputePHIContents = true;
> > +  }
> > +
> > +  // The sunk instruction's results.
> > +  ModelledPHI NewPHI(NewInsts, ActivePreds);
> > +
> > +  // Does sinking this instruction render previous PHIs redundant?
> > +  if (NeededPHIs.find(NewPHI) != NeededPHIs.end()) {
> > +    NeededPHIs.erase(NewPHI);
> > +    RecomputePHIContents = true;
> > +  }
> > +
> > +  if (RecomputePHIContents) {
> > +    // The needed PHIs have changed, so recompute the set of all needed
> > +    // values.
> > +    PHIContents.clear();
> > +    for (auto &PHI : NeededPHIs)
> > +      PHIContents.insert(PHI.getValues().begin(),
> PHI.getValues().end());
> > +  }
> > +
> > +  // Is this instruction required by a later PHI that doesn't match
> this PHI?
> > +  // if so, we can't sink this instruction.
> > +  for (auto *V : NewPHI.getValues())
> > +    if (PHIContents.count(V))
> > +      // V exists in this PHI, but the whole PHI is different to NewPHI
> > +      // (else it would have been removed earlier). We cannot continue
> > +      // because this isn't representable.
> > +      return None;
> > +
> > +  // Which operands need PHIs?
> > +  // FIXME: If any of these fail, we should partition up the candidates
> to
> > +  // try and continue making progress.
> > +  Instruction *I0 = NewInsts[0];
> > +  for (unsigned OpNum = 0, E = I0->getNumOperands(); OpNum != E;
> ++OpNum) {
> > +    ModelledPHI PHI(NewInsts, OpNum, ActivePreds);
> > +    if (PHI.areAllIncomingValuesSame())
> > +      continue;
> > +    if (!canReplaceOperandWithVariable(I0, OpNum))
> > +      // We can 't create a PHI from this instruction!
> > +      return None;
> > +    if (NeededPHIs.count(PHI))
> > +      continue;
> > +    if (!PHI.areAllIncomingValuesSameType())
> > +      return None;
> > +    // Don't create indirect calls! The called value is the final
> operand.
> > +    if ((isa<CallInst>(I0) || isa<InvokeInst>(I0)) && OpNum == E - 1 &&
> > +        PHI.areAnyIncomingValuesConstant())
> > +      return None;
> > +
> > +    NeededPHIs.reserve(NeededPHIs.size());
> > +    NeededPHIs.insert(PHI);
> > +    PHIContents.insert(PHI.getValues().begin(), PHI.getValues().end());
> > +  }
> > +
> > +  if (isMemoryInst(NewInsts[0]))
> > +    ++MemoryInstNum;
> > +
> > +  SinkingInstructionCandidate Cand;
> > +  Cand.NumInstructions = ++InstNum;
> > +  Cand.NumMemoryInsts = MemoryInstNum;
> > +  Cand.NumBlocks = ActivePreds.size();
> > +  Cand.NumPHIs = NeededPHIs.size();
> > +  for (auto *C : ActivePreds)
> > +    Cand.Blocks.push_back(C);
> > +
> > +  return Cand;
> > +}
> > +
> > +unsigned GVNSink::sinkBB(BasicBlock *BBEnd) {
> > +  DEBUG(dbgs() << "GVNSink: running on basic block ";
> > +        BBEnd->printAsOperand(dbgs()); dbgs() << "\n");
> > +  SmallVector<BasicBlock *, 4> Preds;
> > +  for (auto *B : predecessors(BBEnd)) {
> > +    auto *T = B->getTerminator();
> > +    if (isa<BranchInst>(T) || isa<SwitchInst>(T))
> > +      Preds.push_back(B);
> > +    else
> > +      return 0;
> > +  }
> > +  if (Preds.size() < 2)
> > +    return 0;
> > +  std::sort(Preds.begin(), Preds.end());
> > +
> > +  unsigned NumOrigPreds = Preds.size();
> > +  // We can only sink instructions through unconditional branches.
> > +  for (auto I = Preds.begin(); I != Preds.end();) {
> > +    if ((*I)->getTerminator()->getNumSuccessors() != 1)
> > +      I = Preds.erase(I);
> > +    else
> > +      ++I;
> > +  }
> > +
> > +  LockstepReverseIterator LRI(Preds);
> > +  SmallVector<SinkingInstructionCandidate, 4> Candidates;
> > +  unsigned InstNum = 0, MemoryInstNum = 0;
> > +  ModelledPHISet NeededPHIs;
> > +  SmallPtrSet<Value *, 4> PHIContents;
> > +  analyzeInitialPHIs(BBEnd, NeededPHIs, PHIContents);
> > +  unsigned NumOrigPHIs = NeededPHIs.size();
> > +
> > +  while (LRI.isValid()) {
> > +    auto Cand = analyzeInstructionForSinking(LRI, InstNum,
> MemoryInstNum,
> > +                                             NeededPHIs, PHIContents);
> > +    if (!Cand)
> > +      break;
> > +    Cand->calculateCost(NumOrigPHIs, Preds.size());
> > +    Candidates.emplace_back(*Cand);
> > +    --LRI;
> > +  }
> > +
> > +  std::stable_sort(
> > +      Candidates.begin(), Candidates.end(),
> > +      [](const SinkingInstructionCandidate &A,
> > +         const SinkingInstructionCandidate &B) { return A >= B; });
>
> std::stable_sort requires a strict weak ordering, so the predicate
> should never return true if A and B are equal. This code violates
> that.
>
> > +  DEBUG(dbgs() << " -- Sinking candidates:\n"; for (auto &C
> > +                                                    : Candidates) dbgs()
> > +                                               << "  " << C << "\n";);
> > +
> > +  // Pick the top candidate, as long it is positive!
> > +  if (Candidates.empty() || Candidates.front().Cost <= 0)
> > +    return 0;
> > +  auto C = Candidates.front();
> > +
> > +  DEBUG(dbgs() << " -- Sinking: " << C << "\n");
> > +  BasicBlock *InsertBB = BBEnd;
> > +  if (C.Blocks.size() < NumOrigPreds) {
> > +    DEBUG(dbgs() << " -- Splitting edge to ";
> BBEnd->printAsOperand(dbgs());
> > +          dbgs() << "\n");
> > +    InsertBB = SplitBlockPredecessors(BBEnd, C.Blocks,
> ".gvnsink.split");
> > +    if (!InsertBB) {
> > +      DEBUG(dbgs() << " -- FAILED to split edge!\n");
> > +      // Edge couldn't be split.
> > +      return 0;
> > +    }
> > +  }
> > +
> > +  for (unsigned I = 0; I < C.NumInstructions; ++I)
> > +    sinkLastInstruction(C.Blocks, InsertBB);
> > +
> > +  return C.NumInstructions;
> > +}
> > +
> > +void GVNSink::sinkLastInstruction(ArrayRef<BasicBlock *> Blocks,
> > +                                  BasicBlock *BBEnd) {
> > +  SmallVector<Instruction *, 4> Insts;
> > +  for (BasicBlock *BB : Blocks)
> > +    Insts.push_back(BB->getTerminator()->getPrevNode());
> > +  Instruction *I0 = Insts.front();
> > +
> > +  SmallVector<Value *, 4> NewOperands;
> > +  for (unsigned O = 0, E = I0->getNumOperands(); O != E; ++O) {
> > +    bool NeedPHI = any_of(Insts, [&I0, O](const Instruction *I) {
> > +      return I->getOperand(O) != I0->getOperand(O);
> > +    });
> > +    if (!NeedPHI) {
> > +      NewOperands.push_back(I0->getOperand(O));
> > +      continue;
> > +    }
> > +
> > +    // Create a new PHI in the successor block and populate it.
> > +    auto *Op = I0->getOperand(O);
> > +    assert(!Op->getType()->isTokenTy() && "Can't PHI tokens!");
> > +    auto *PN = PHINode::Create(Op->getType(), Insts.size(),
> > +                               Op->getName() + ".sink",
> &BBEnd->front());
> > +    for (auto *I : Insts)
> > +      PN->addIncoming(I->getOperand(O), I->getParent());
> > +    NewOperands.push_back(PN);
> > +  }
> > +
> > +  // Arbitrarily use I0 as the new "common" instruction; remap its
> operands
> > +  // and move it to the start of the successor block.
> > +  for (unsigned O = 0, E = I0->getNumOperands(); O != E; ++O)
> > +    I0->getOperandUse(O).set(NewOperands[O]);
> > +  I0->moveBefore(&*BBEnd->getFirstInsertionPt());
> > +
> > +  // Update metadata and IR flags.
> > +  for (auto *I : Insts)
> > +    if (I != I0) {
> > +      combineMetadataForCSE(I0, I);
> > +      I0->andIRFlags(I);
> > +    }
> > +
> > +  for (auto *I : Insts)
> > +    if (I != I0)
> > +      I->replaceAllUsesWith(I0);
> > +  foldPointlessPHINodes(BBEnd);
> > +
> > +  // Finally nuke all instructions apart from the common instruction.
> > +  for (auto *I : Insts)
> > +    if (I != I0)
> > +      I->eraseFromParent();
> > +
> > +  NumRemoved += Insts.size() - 1;
> > +}
> > +
> >
> +////////////////////////////////////////////////////////////////////////////////
> > +// Pass machinery / boilerplate
> > +
> > +class GVNSinkLegacyPass : public FunctionPass {
> > +public:
> > +  static char ID;
> > +
> > +  GVNSinkLegacyPass() : FunctionPass(ID) {
> > +    initializeGVNSinkLegacyPassPass(*PassRegistry::getPassRegistry());
> > +  }
> > +
> > +  bool runOnFunction(Function &F) override {
> > +    if (skipFunction(F))
> > +      return false;
> > +    GVNSink G;
> > +    return G.run(F);
> > +  }
> > +
> > +  void getAnalysisUsage(AnalysisUsage &AU) const override {
> > +    AU.addPreserved<GlobalsAAWrapperPass>();
> > +  }
> > +};
> > +} // namespace
> > +
> > +PreservedAnalyses GVNSinkPass::run(Function &F, FunctionAnalysisManager
> &AM) {
> > +  GVNSink G;
> > +  if (!G.run(F))
> > +    return PreservedAnalyses::all();
> > +
> > +  PreservedAnalyses PA;
> > +  PA.preserve<GlobalsAA>();
> > +  return PA;
> > +}
> > +
> > +char GVNSinkLegacyPass::ID = 0;
> > +INITIALIZE_PASS_BEGIN(GVNSinkLegacyPass, "gvn-sink",
> > +                      "Early GVN sinking of Expressions", false, false)
> > +INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
> > +INITIALIZE_PASS_DEPENDENCY(PostDominatorTreeWrapperPass)
> > +INITIALIZE_PASS_END(GVNSinkLegacyPass, "gvn-sink",
> > +                    "Early GVN sinking of Expressions", false, false)
> > +
> > +FunctionPass *llvm::createGVNSinkPass() { return new
> GVNSinkLegacyPass(); }
> >
> > Modified: llvm/trunk/lib/Transforms/Scalar/Scalar.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/Scalar.cpp?rev=303850&r1=303849&r2=303850&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Transforms/Scalar/Scalar.cpp (original)
> > +++ llvm/trunk/lib/Transforms/Scalar/Scalar.cpp Thu May 25 07:51:11 2017
> > @@ -48,6 +48,7 @@ void llvm::initializeScalarOpts(PassRegi
> >    initializeEarlyCSELegacyPassPass(Registry);
> >    initializeEarlyCSEMemSSALegacyPassPass(Registry);
> >    initializeGVNHoistLegacyPassPass(Registry);
> > +  initializeGVNSinkLegacyPassPass(Registry);
> >    initializeFlattenCFGPassPass(Registry);
> >    initializeInductiveRangeCheckEliminationPass(Registry);
> >    initializeIndVarSimplifyLegacyPassPass(Registry);
> >
> > Modified: llvm/trunk/lib/Transforms/Utils/Local.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/Local.cpp?rev=303850&r1=303849&r2=303850&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Transforms/Utils/Local.cpp (original)
> > +++ llvm/trunk/lib/Transforms/Utils/Local.cpp Thu May 25 07:51:11 2017
> > @@ -2109,3 +2109,48 @@ void llvm::maybeMarkSanitizerLibraryCall
> >        !F->doesNotAccessMemory())
> >      CI->addAttribute(AttributeList::FunctionIndex,
> Attribute::NoBuiltin);
> >  }
> > +
> > +bool llvm::canReplaceOperandWithVariable(const Instruction *I, unsigned
> OpIdx) {
> > +  // We can't have a PHI with a metadata type.
> > +  if (I->getOperand(OpIdx)->getType()->isMetadataTy())
> > +    return false;
> > +
> > +  // Early exit.
> > +  if (!isa<Constant>(I->getOperand(OpIdx)))
> > +    return true;
> > +
> > +  switch (I->getOpcode()) {
> > +  default:
> > +    return true;
> > +  case Instruction::Call:
> > +  case Instruction::Invoke:
> > +    // Many arithmetic intrinsics have no issue taking a
> > +    // variable, however it's hard to distingish these from
> > +    // specials such as @llvm.frameaddress that require a constant.
> > +    if (isa<IntrinsicInst>(I))
> > +      return false;
> > +
> > +    // Constant bundle operands may need to retain their constant-ness
> for
> > +    // correctness.
> > +    if (ImmutableCallSite(I).isBundleOperand(OpIdx))
> > +      return false;
> > +    return true;
> > +  case Instruction::ShuffleVector:
> > +    // Shufflevector masks are constant.
> > +    return OpIdx != 2;
> > +  case Instruction::ExtractValue:
> > +  case Instruction::InsertValue:
> > +    // All operands apart from the first are constant.
> > +    return OpIdx == 0;
> > +  case Instruction::Alloca:
> > +    return false;
> > +  case Instruction::GetElementPtr:
> > +    if (OpIdx == 0)
> > +      return true;
> > +    gep_type_iterator It = gep_type_begin(I);
> > +    for (auto E = std::next(It, OpIdx); It != E; ++It)
> > +      if (It.isStruct())
> > +        return false;
> > +    return true;
> > +  }
> > +}
> >
> > Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=303850&r1=303849&r2=303850&view=diff
> >
> ==============================================================================
> > --- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
> > +++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu May 25 07:51:11
> 2017
> > @@ -1376,53 +1376,6 @@ HoistTerminator:
> >    return true;
> >  }
> >
> > -// Is it legal to place a variable in operand \c OpIdx of \c I?
> > -// FIXME: This should be promoted to Instruction.
> > -static bool canReplaceOperandWithVariable(const Instruction *I,
> > -                                          unsigned OpIdx) {
> > -  // We can't have a PHI with a metadata type.
> > -  if (I->getOperand(OpIdx)->getType()->isMetadataTy())
> > -    return false;
> > -
> > -  // Early exit.
> > -  if (!isa<Constant>(I->getOperand(OpIdx)))
> > -    return true;
> > -
> > -  switch (I->getOpcode()) {
> > -  default:
> > -    return true;
> > -  case Instruction::Call:
> > -  case Instruction::Invoke:
> > -    // FIXME: many arithmetic intrinsics have no issue taking a
> > -    // variable, however it's hard to distingish these from
> > -    // specials such as @llvm.frameaddress that require a constant.
> > -    if (isa<IntrinsicInst>(I))
> > -      return false;
> > -
> > -    // Constant bundle operands may need to retain their constant-ness
> for
> > -    // correctness.
> > -    if (ImmutableCallSite(I).isBundleOperand(OpIdx))
> > -      return false;
> > -
> > -    return true;
> > -
> > -  case Instruction::ShuffleVector:
> > -    // Shufflevector masks are constant.
> > -    return OpIdx != 2;
> > -  case Instruction::ExtractValue:
> > -  case Instruction::InsertValue:
> > -    // All operands apart from the first are constant.
> > -    return OpIdx == 0;
> > -  case Instruction::Alloca:
> > -    return false;
> > -  case Instruction::GetElementPtr:
> > -    if (OpIdx == 0)
> > -      return true;
> > -    gep_type_iterator It = std::next(gep_type_begin(I), OpIdx - 1);
> > -    return It.isSequential();
> > -  }
> > -}
> > -
> >  // All instructions in Insts belong to different blocks that all
> unconditionally
> >  // branch to a common successor. Analyze each instruction and return
> true if it
> >  // would be possible to sink them into their successor, creating one
> common
> >
> > Added: llvm/trunk/test/Transforms/GVNSink/dither.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVNSink/dither.ll?rev=303850&view=auto
> >
> ==============================================================================
> > --- llvm/trunk/test/Transforms/GVNSink/dither.ll (added)
> > +++ llvm/trunk/test/Transforms/GVNSink/dither.ll Thu May 25 07:51:11 2017
> > @@ -0,0 +1,42 @@
> > +; RUN: opt < %s -S -gvn-sink | FileCheck %s
> > +
> > +; Because %tmp17 has flipped operands to its equivalents %tmp14 and
> %tmp7, we
> > +; can't sink the zext as we'd need a shuffling PHI in between.
> > +;
> > +; Just sinking the zext isn't profitable, so ensure nothing is sunk.
> > +
> > +; CHECK-LABEL: @hoge
> > +; CHECK-NOT: bb18.gvnsink.split
> > +define void @hoge() {
> > +bb:
> > +  br i1 undef, label %bb4, label %bb11
> > +
> > +bb4:                                              ; preds = %bb3
> > +  br i1 undef, label %bb6, label %bb8
> > +
> > +bb6:                                              ; preds = %bb5
> > +  %tmp = zext i16 undef to i64
> > +  %tmp7 = add i64 %tmp, undef
> > +  br label %bb18
> > +
> > +bb8:                                              ; preds = %bb5
> > +  %tmp9 = zext i16 undef to i64
> > +  br label %bb18
> > +
> > +bb11:                                             ; preds = %bb10
> > +  br i1 undef, label %bb12, label %bb15
> > +
> > +bb12:                                             ; preds = %bb11
> > +  %tmp13 = zext i16 undef to i64
> > +  %tmp14 = add i64 %tmp13, undef
> > +  br label %bb18
> > +
> > +bb15:                                             ; preds = %bb11
> > +  %tmp16 = zext i16 undef to i64
> > +  %tmp17 = add i64 undef, %tmp16
> > +  br label %bb18
> > +
> > +bb18:                                             ; preds = %bb15,
> %bb12, %bb8, %bb6
> > +  %tmp19 = phi i64 [ %tmp7, %bb6 ], [ undef, %bb8 ], [ %tmp14, %bb12 ],
> [ %tmp17, %bb15 ]
> > +  unreachable
> > +}
> >
> > Added: llvm/trunk/test/Transforms/GVNSink/indirect-call.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVNSink/indirect-call.ll?rev=303850&view=auto
> >
> ==============================================================================
> > --- llvm/trunk/test/Transforms/GVNSink/indirect-call.ll (added)
> > +++ llvm/trunk/test/Transforms/GVNSink/indirect-call.ll Thu May 25
> 07:51:11 2017
> > @@ -0,0 +1,70 @@
> > +; RUN: opt < %s -gvn-sink -simplifycfg -simplifycfg-sink-common=false
> -S | FileCheck %s
> > +
> > +declare i8 @ext(i1)
> > +
> > +define zeroext i1 @test1(i1 zeroext %flag, i32 %blksA, i32 %blksB, i32
> %nblks, i8(i1)* %ext) {
> > +entry:
> > +  %cmp = icmp uge i32 %blksA, %nblks
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +; CHECK-LABEL: test1
> > +; CHECK: call i8 @ext
> > +; CHECK: call i8 %ext
> > +if.then:
> > +  %frombool1 = call i8 @ext(i1 %cmp)
> > +  br label %if.end
> > +
> > +if.else:
> > +  %frombool3 = call i8 %ext(i1 %cmp)
> > +  br label %if.end
> > +
> > +if.end:
> > +  %obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.else ]
> > +  %tobool4 = icmp ne i8 %obeys.0, 0
> > +  ret i1 %tobool4
> > +}
> > +
> > +define zeroext i1 @test2(i1 zeroext %flag, i32 %blksA, i32 %blksB, i32
> %nblks, i8(i1)* %ext) {
> > +entry:
> > +  %cmp = icmp uge i32 %blksA, %nblks
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +; CHECK-LABEL: test2
> > +; CHECK: call i8 %ext
> > +; CHECK-NOT: call
> > +if.then:
> > +  %frombool1 = call i8 %ext(i1 %cmp)
> > +  br label %if.end
> > +
> > +if.else:
> > +  %frombool3 = call i8 %ext(i1 %cmp)
> > +  br label %if.end
> > +
> > +if.end:
> > +  %obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.else ]
> > +  %tobool4 = icmp ne i8 %obeys.0, 0
> > +  ret i1 %tobool4
> > +}
> > +
> > +define zeroext i1 @test3(i1 zeroext %flag, i32 %blksA, i32 %blksB, i32
> %nblks, i8(i1)* %ext1, i8(i1)* %ext2) {
> > +entry:
> > +  %cmp = icmp uge i32 %blksA, %nblks
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +; CHECK-LABEL: test3
> > +; CHECK: %[[x:.*]] = select i1 %flag, i8 (i1)* %ext1, i8 (i1)* %ext2
> > +; CHECK: call i8 %[[x]](i1 %cmp)
> > +; CHECK-NOT: call
> > +if.then:
> > +  %frombool1 = call i8 %ext1(i1 %cmp)
> > +  br label %if.end
> > +
> > +if.else:
> > +  %frombool3 = call i8 %ext2(i1 %cmp)
> > +  br label %if.end
> > +
> > +if.end:
> > +  %obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.else ]
> > +  %tobool4 = icmp ne i8 %obeys.0, 0
> > +  ret i1 %tobool4
> > +}
> >
> > Added: llvm/trunk/test/Transforms/GVNSink/sink-common-code.ll
> > URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/GVNSink/sink-common-code.ll?rev=303850&view=auto
> >
> ==============================================================================
> > --- llvm/trunk/test/Transforms/GVNSink/sink-common-code.ll (added)
> > +++ llvm/trunk/test/Transforms/GVNSink/sink-common-code.ll Thu May 25
> 07:51:11 2017
> > @@ -0,0 +1,694 @@
> > +; RUN: opt < %s -gvn-sink -simplifycfg -simplifycfg-sink-common=false
> -S | FileCheck %s
> > +
> > +define zeroext i1 @test1(i1 zeroext %flag, i32 %blksA, i32 %blksB, i32
> %nblks) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +; CHECK-LABEL: test1
> > +; CHECK: add
> > +; CHECK: select
> > +; CHECK: icmp
> > +; CHECK-NOT: br
> > +if.then:
> > +  %cmp = icmp uge i32 %blksA, %nblks
> > +  %frombool1 = zext i1 %cmp to i8
> > +  br label %if.end
> > +
> > +if.else:
> > +  %add = add i32 %nblks, %blksB
> > +  %cmp2 = icmp ule i32 %add, %blksA
> > +  %frombool3 = zext i1 %cmp2 to i8
> > +  br label %if.end
> > +
> > +if.end:
> > +  %obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.else ]
> > +  %tobool4 = icmp ne i8 %obeys.0, 0
> > +  ret i1 %tobool4
> > +}
> > +
> > +define zeroext i1 @test2(i1 zeroext %flag, i32 %blksA, i32 %blksB, i32
> %nblks) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +; CHECK-LABEL: test2
> > +; CHECK: add
> > +; CHECK: select
> > +; CHECK: icmp
> > +; CHECK-NOT: br
> > +if.then:
> > +  %cmp = icmp uge i32 %blksA, %nblks
> > +  %frombool1 = zext i1 %cmp to i8
> > +  br label %if.end
> > +
> > +if.else:
> > +  %add = add i32 %nblks, %blksB
> > +  %cmp2 = icmp uge i32 %blksA, %add
> > +  %frombool3 = zext i1 %cmp2 to i8
> > +  br label %if.end
> > +
> > +if.end:
> > +  %obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.else ]
> > +  %tobool4 = icmp ne i8 %obeys.0, 0
> > +  ret i1 %tobool4
> > +}
> > +
> > +declare i32 @foo(i32, i32) nounwind readnone
> > +
> > +define i32 @test3(i1 zeroext %flag, i32 %x, i32 %y) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %x0 = call i32 @foo(i32 %x, i32 0) nounwind readnone
> > +  %y0 = call i32 @foo(i32 %x, i32 1) nounwind readnone
> > +  br label %if.end
> > +
> > +if.else:
> > +  %x1 = call i32 @foo(i32 %y, i32 0) nounwind readnone
> > +  %y1 = call i32 @foo(i32 %y, i32 1) nounwind readnone
> > +  br label %if.end
> > +
> > +if.end:
> > +  %xx = phi i32 [ %x0, %if.then ], [ %x1, %if.else ]
> > +  %yy = phi i32 [ %y0, %if.then ], [ %y1, %if.else ]
> > +  %ret = add i32 %xx, %yy
> > +  ret i32 %ret
> > +}
> > +
> > +; CHECK-LABEL: test3
> > +; CHECK: select
> > +; CHECK: call
> > +; CHECK: call
> > +; CHECK: add
> > +; CHECK-NOT: br
> > +
> > +define i32 @test4(i1 zeroext %flag, i32 %x, i32* %y) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %a = add i32 %x, 5
> > +  store i32 %a, i32* %y
> > +  br label %if.end
> > +
> > +if.else:
> > +  %b = add i32 %x, 7
> > +  store i32 %b, i32* %y
> > +  br label %if.end
> > +
> > +if.end:
> > +  ret i32 1
> > +}
> > +
> > +; CHECK-LABEL: test4
> > +; CHECK: select
> > +; CHECK: store
> > +; CHECK-NOT: store
> > +
> > +define i32 @test5(i1 zeroext %flag, i32 %x, i32* %y) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %a = add i32 %x, 5
> > +  store volatile i32 %a, i32* %y
> > +  br label %if.end
> > +
> > +if.else:
> > +  %b = add i32 %x, 7
> > +  store i32 %b, i32* %y
> > +  br label %if.end
> > +
> > +if.end:
> > +  ret i32 1
> > +}
> > +
> > +; CHECK-LABEL: test5
> > +; CHECK: store volatile
> > +; CHECK: store
> > +
> > +define i32 @test6(i1 zeroext %flag, i32 %x, i32* %y) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %a = add i32 %x, 5
> > +  store volatile i32 %a, i32* %y
> > +  br label %if.end
> > +
> > +if.else:
> > +  %b = add i32 %x, 7
> > +  store volatile i32 %b, i32* %y
> > +  br label %if.end
> > +
> > +if.end:
> > +  ret i32 1
> > +}
> > +
> > +; CHECK-LABEL: test6
> > +; CHECK: select
> > +; CHECK: store volatile
> > +; CHECK-NOT: store
> > +
> > +define i32 @test7(i1 zeroext %flag, i32 %x, i32* %y) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %z = load volatile i32, i32* %y
> > +  %a = add i32 %z, 5
> > +  store volatile i32 %a, i32* %y
> > +  br label %if.end
> > +
> > +if.else:
> > +  %w = load volatile i32, i32* %y
> > +  %b = add i32 %w, 7
> > +  store volatile i32 %b, i32* %y
> > +  br label %if.end
> > +
> > +if.end:
> > +  ret i32 1
> > +}
> > +
> > +; CHECK-LABEL: test7
> > +; CHECK-DAG: select
> > +; CHECK-DAG: load volatile
> > +; CHECK: store volatile
> > +; CHECK-NOT: load
> > +; CHECK-NOT: store
> > +
> > +; The extra store in %if.then means %z and %w are not equivalent.
> > +define i32 @test9(i1 zeroext %flag, i32 %x, i32* %y, i32* %p) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  store i32 7, i32* %p
> > +  %z = load volatile i32, i32* %y
> > +  store i32 6, i32* %p
> > +  %a = add i32 %z, 5
> > +  store volatile i32 %a, i32* %y
> > +  br label %if.end
> > +
> > +if.else:
> > +  %w = load volatile i32, i32* %y
> > +  %b = add i32 %w, 7
> > +  store volatile i32 %b, i32* %y
> > +  br label %if.end
> > +
> > +if.end:
> > +  ret i32 1
> > +}
> > +
> > +; CHECK-LABEL: test9
> > +; CHECK: add
> > +; CHECK: add
> > +
> > +%struct.anon = type { i32, i32 }
> > +
> > +; The GEP indexes a struct type so cannot have a variable last index.
> > +define i32 @test10(i1 zeroext %flag, i32 %x, i32* %y, %struct.anon* %s)
> {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %dummy = add i32 %x, 5
> > +  %gepa = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0,
> i32 0
> > +  store volatile i32 %x, i32* %gepa
> > +  br label %if.end
> > +
> > +if.else:
> > +  %dummy1 = add i32 %x, 6
> > +  %gepb = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0,
> i32 1
> > +  store volatile i32 %x, i32* %gepb
> > +  br label %if.end
> > +
> > +if.end:
> > +  ret i32 1
> > +}
> > +
> > +; CHECK-LABEL: test10
> > +; CHECK: getelementptr
> > +; CHECK: store volatile
> > +; CHECK: getelementptr
> > +; CHECK: store volatile
> > +
> > +; The shufflevector's mask operand cannot be merged in a PHI.
> > +define i32 @test11(i1 zeroext %flag, i32 %w, <2 x i32> %x, <2 x i32>
> %y) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %dummy = add i32 %w, 5
> > +  %sv1 = shufflevector <2 x i32> %x, <2 x i32> %y, <2 x i32> <i32 0,
> i32 1>
> > +  br label %if.end
> > +
> > +if.else:
> > +  %dummy1 = add i32 %w, 6
> > +  %sv2 = shufflevector <2 x i32> %x, <2 x i32> %y, <2 x i32> <i32 1,
> i32 0>
> > +  br label %if.end
> > +
> > +if.end:
> > +  %p = phi <2 x i32> [ %sv1, %if.then ], [ %sv2, %if.else ]
> > +  ret i32 1
> > +}
> > +
> > +; CHECK-LABEL: test11
> > +; CHECK: shufflevector
> > +; CHECK: shufflevector
> > +
> > +; We can't common an intrinsic!
> > +define i32 @test12(i1 zeroext %flag, i32 %w, i32 %x, i32 %y) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %dummy = add i32 %w, 5
> > +  %sv1 = call i32 @llvm.ctlz.i32(i32 %x)
> > +  br label %if.end
> > +
> > +if.else:
> > +  %dummy1 = add i32 %w, 6
> > +  %sv2 = call i32 @llvm.cttz.i32(i32 %x)
> > +  br label %if.end
> > +
> > +if.end:
> > +  %p = phi i32 [ %sv1, %if.then ], [ %sv2, %if.else ]
> > +  ret i32 1
> > +}
> > +
> > +declare i32 @llvm.ctlz.i32(i32 %x) readnone
> > +declare i32 @llvm.cttz.i32(i32 %x) readnone
> > +
> > +; CHECK-LABEL: test12
> > +; CHECK: call i32 @llvm.ctlz
> > +; CHECK: call i32 @llvm.cttz
> > +
> > +; The TBAA metadata should be properly combined.
> > +define i32 @test13(i1 zeroext %flag, i32 %x, i32* %y) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %z = load volatile i32, i32* %y
> > +  %a = add i32 %z, 5
> > +  store volatile i32 %a, i32* %y, !tbaa !3
> > +  br label %if.end
> > +
> > +if.else:
> > +  %w = load volatile i32, i32* %y
> > +  %b = add i32 %w, 7
> > +  store volatile i32 %b, i32* %y, !tbaa !4
> > +  br label %if.end
> > +
> > +if.end:
> > +  ret i32 1
> > +}
> > +
> > +!0 = !{ !"an example type tree" }
> > +!1 = !{ !"int", !0 }
> > +!2 = !{ !"float", !0 }
> > +!3 = !{ !"const float", !2, i64 0 }
> > +!4 = !{ !"special float", !2, i64 1 }
> > +
> > +; CHECK-LABEL: test13
> > +; CHECK-DAG: select
> > +; CHECK-DAG: load volatile
> > +; CHECK: store volatile {{.*}}, !tbaa !0
> > +; CHECK-NOT: load
> > +; CHECK-NOT: store
> > +
> > +; The call should be commoned.
> > +define i32 @test13a(i1 zeroext %flag, i32 %w, i32 %x, i32 %y) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %sv1 = call i32 @bar(i32 %x)
> > +  br label %if.end
> > +
> > +if.else:
> > +  %sv2 = call i32 @bar(i32 %y)
> > +  br label %if.end
> > +
> > +if.end:
> > +  %p = phi i32 [ %sv1, %if.then ], [ %sv2, %if.else ]
> > +  ret i32 1
> > +}
> > +declare i32 @bar(i32)
> > +
> > +; CHECK-LABEL: test13a
> > +; CHECK: %[[x:.*]] = select i1 %flag
> > +; CHECK: call i32 @bar(i32 %[[x]])
> > +
> > +; The load should be commoned.
> > +define i32 @test14(i1 zeroext %flag, i32 %w, i32 %x, i32 %y,
> %struct.anon* %s) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %dummy = add i32 %x, 1
> > +  %gepa = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0,
> i32 1
> > +  %sv1 = load i32, i32* %gepa
> > +  %cmp1 = icmp eq i32 %sv1, 56
> > +  br label %if.end
> > +
> > +if.else:
> > +  %dummy2 = add i32 %x, 4
> > +  %gepb = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0,
> i32 1
> > +  %sv2 = load i32, i32* %gepb
> > +  %cmp2 = icmp eq i32 %sv2, 57
> > +  br label %if.end
> > +
> > +if.end:
> > +  %p = phi i1 [ %cmp1, %if.then ], [ %cmp2, %if.else ]
> > +  ret i32 1
> > +}
> > +
> > +; CHECK-LABEL: test14
> > +; CHECK: getelementptr
> > +; CHECK: load
> > +; CHECK-NOT: load
> > +
> > +; The load should be commoned.
> > +define i32 @test15(i1 zeroext %flag, i32 %w, i32 %x, i32 %y,
> %struct.anon* %s) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %dummy = add i32 %x, 1
> > +  %gepa = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0,
> i32 0
> > +  %sv1 = load i32, i32* %gepa
> > +  %ext1 = zext i32 %sv1 to i64
> > +  %cmp1 = icmp eq i64 %ext1, 56
> > +  br label %if.end
> > +
> > +if.else:
> > +  %dummy2 = add i32 %x, 4
> > +  %gepb = getelementptr inbounds %struct.anon, %struct.anon* %s, i32 0,
> i32 1
> > +  %sv2 = load i32, i32* %gepb
> > +  %ext2 = zext i32 %sv2 to i64
> > +  %cmp2 = icmp eq i64 %ext2, 56
> > +  br label %if.end
> > +
> > +if.end:
> > +  %p = phi i1 [ %cmp1, %if.then ], [ %cmp2, %if.else ]
> > +  ret i32 1
> > +}
> > +
> > +; CHECK-LABEL: test15
> > +; CHECK: getelementptr
> > +; CHECK: load
> > +; CHECK-NOT: load
> > +
> > +define zeroext i1 @test_crash(i1 zeroext %flag, i32* %i4, i32* %m, i32*
> %n) {
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %tmp1 = load i32, i32* %i4
> > +  %tmp2 = add i32 %tmp1, -1
> > +  store i32 %tmp2, i32* %i4
> > +  br label %if.end
> > +
> > +if.else:
> > +  %tmp3 = load i32, i32* %m
> > +  %tmp4 = load i32, i32* %n
> > +  %tmp5 = add i32 %tmp3, %tmp4
> > +  store i32 %tmp5, i32* %i4
> > +  br label %if.end
> > +
> > +if.end:
> > +  ret i1 true
> > +}
> > +
> > +; CHECK-LABEL: test_crash
> > +; No checks for test_crash - just ensure it doesn't crash!
> > +
> > +define zeroext i1 @test16(i1 zeroext %flag, i1 zeroext %flag2, i32
> %blksA, i32 %blksB, i32 %nblks) {
> > +
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %cmp = icmp uge i32 %blksA, %nblks
> > +  %frombool1 = zext i1 %cmp to i8
> > +  br label %if.end
> > +
> > +if.else:
> > +  br i1 %flag2, label %if.then2, label %if.end
> > +
> > +if.then2:
> > +  %add = add i32 %nblks, %blksB
> > +  %cmp2 = icmp ule i32 %add, %blksA
> > +  %frombool3 = zext i1 %cmp2 to i8
> > +  br label %if.end
> > +
> > +if.end:
> > +  %obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.then2
> ], [ 0, %if.else ]
> > +  %tobool4 = icmp ne i8 %obeys.0, 0
> > +  ret i1 %tobool4
> > +}
> > +
> > +; CHECK-LABEL: test16
> > +; CHECK: zext
> > +; CHECK: zext
> > +
> > +define zeroext i1 @test16a(i1 zeroext %flag, i1 zeroext %flag2, i32
> %blksA, i32 %blksB, i32 %nblks, i8* %p) {
> > +
> > +entry:
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %cmp = icmp uge i32 %blksA, %nblks
> > +  %frombool1 = zext i1 %cmp to i8
> > +  %b1 = sext i8 %frombool1 to i32
> > +  %b2 = trunc i32 %b1 to i8
> > +  store i8 %b2, i8* %p
> > +  br label %if.end
> > +
> > +if.else:
> > +  br i1 %flag2, label %if.then2, label %if.end
> > +
> > +if.then2:
> > +  %add = add i32 %nblks, %blksB
> > +  %cmp2 = icmp ule i32 %add, %blksA
> > +  %frombool3 = zext i1 %cmp2 to i8
> > +  %a1 = sext i8 %frombool3 to i32
> > +  %a2 = trunc i32 %a1 to i8
> > +  store i8 %a2, i8* %p
> > +  br label %if.end
> > +
> > +if.end:
> > +  ret i1 true
> > +}
> > +
> > +; CHECK-LABEL: test16a
> > +; CHECK: zext
> > +; CHECK-NOT: zext
> > +
> > +define zeroext i1 @test17(i32 %flag, i32 %blksA, i32 %blksB, i32
> %nblks) {
> > +entry:
> > +  switch i32 %flag, label %if.end [
> > +    i32 0, label %if.then
> > +    i32 1, label %if.then2
> > +  ]
> > +
> > +if.then:
> > +  %cmp = icmp uge i32 %blksA, %nblks
> > +  %frombool1 = call i8 @i1toi8(i1 %cmp)
> > +  %a1 = sext i8 %frombool1 to i32
> > +  %a2 = trunc i32 %a1 to i8
> > +  br label %if.end
> > +
> > +if.then2:
> > +  %add = add i32 %nblks, %blksB
> > +  %cmp2 = icmp ule i32 %add, %blksA
> > +  %frombool3 = call i8 @i1toi8(i1 %cmp2)
> > +  %b1 = sext i8 %frombool3 to i32
> > +  %b2 = trunc i32 %b1 to i8
> > +  br label %if.end
> > +
> > +if.end:
> > +  %obeys.0 = phi i8 [ %a2, %if.then ], [ %b2, %if.then2 ], [ 0, %entry ]
> > +  %tobool4 = icmp ne i8 %obeys.0, 0
> > +  ret i1 %tobool4
> > +}
> > +declare i8 @i1toi8(i1)
> > +
> > +; FIXME: DISABLED - we don't consider this profitable. We should
> > +;  - Consider argument setup/return mov'ing for calls, like InlineCost
> does.
> > +;  - Consider the removal of the %obeys.0 PHI (zero PHI movement
> overall)
> > +
> > +; DISABLED-CHECK-LABEL: test17
> > +; DISABLED-CHECK: if.then:
> > +; DISABLED-CHECK-NEXT: icmp uge
> > +; DISABLED-CHECK-NEXT: br label %[[x:.*]]
> > +
> > +; DISABLED-CHECK: if.then2:
> > +; DISABLED-CHECK-NEXT: add
> > +; DISABLED-CHECK-NEXT: icmp ule
> > +; DISABLED-CHECK-NEXT: br label %[[x]]
> > +
> > +; DISABLED-CHECK: [[x]]:
> > +; DISABLED-CHECK-NEXT: %[[y:.*]] = phi i1 [ %cmp
> > +; DISABLED-CHECK-NEXT: %[[z:.*]] = call i8 @i1toi8(i1 %[[y]])
> > +; DISABLED-CHECK-NEXT: br label %if.end
> > +
> > +; DISABLED-CHECK: if.end:
> > +; DISABLED-CHECK-NEXT: phi i8
> > +; DISABLED-CHECK-DAG: [ %[[z]], %[[x]] ]
> > +; DISABLED-CHECK-DAG: [ 0, %entry ]
> > +
> > +define zeroext i1 @test18(i32 %flag, i32 %blksA, i32 %blksB, i32
> %nblks) {
> > +entry:
> > +  switch i32 %flag, label %if.then3 [
> > +    i32 0, label %if.then
> > +    i32 1, label %if.then2
> > +  ]
> > +
> > +if.then:
> > +  %cmp = icmp uge i32 %blksA, %nblks
> > +  %frombool1 = zext i1 %cmp to i8
> > +  br label %if.end
> > +
> > +if.then2:
> > +  %add = add i32 %nblks, %blksB
> > +  %cmp2 = icmp ule i32 %add, %blksA
> > +  %frombool3 = zext i1 %cmp2 to i8
> > +  br label %if.end
> > +
> > +if.then3:
> > +  %add2 = add i32 %nblks, %blksA
> > +  %cmp3 = icmp ule i32 %add2, %blksA
> > +  %frombool4 = zext i1 %cmp3 to i8
> > +  br label %if.end
> > +
> > +if.end:
> > +  %obeys.0 = phi i8 [ %frombool1, %if.then ], [ %frombool3, %if.then2
> ], [ %frombool4, %if.then3 ]
> > +  %tobool4 = icmp ne i8 %obeys.0, 0
> > +  ret i1 %tobool4
> > +}
> > +
> > +; CHECK-LABEL: test18
> > +; CHECK: if.end:
> > +; CHECK-NEXT: %[[x:.*]] = phi i1
> > +; CHECK-DAG: [ %cmp, %if.then ]
> > +; CHECK-DAG: [ %cmp2, %if.then2 ]
> > +; CHECK-DAG: [ %cmp3, %if.then3 ]
> > +; CHECK-NEXT: zext i1 %[[x]] to i8
> > +
> > +; The phi is confusing - both add instructions are used by it, but
> > +; not on their respective unconditional arcs. It should not be
> > +; optimized.
> > +define void @test_pr30292(i1 %cond, i1 %cond2, i32 %a, i32 %b) {
> > +entry:
> > +  %add1 = add i32 %a, 1
> > +  br label %succ
> > +
> > +one:
> > +  br i1 %cond, label %two, label %succ
> > +
> > +two:
> > +  call void @g()
> > +  %add2 = add i32 %a, 1
> > +  br label %succ
> > +
> > +succ:
> > +  %p = phi i32 [ 0, %entry ], [ %add1, %one ], [ %add2, %two ]
> > +  br label %one
> > +}
> > +declare void @g()
> > +
> > +; CHECK-LABEL: test_pr30292
> > +; CHECK: phi i32 [ 0, %entry ], [ %add1, %succ ], [ %add2, %two ]
> > +
> > +define zeroext i1 @test_pr30244(i1 zeroext %flag, i1 zeroext %flag2,
> i32 %blksA, i32 %blksB, i32 %nblks) {
> > +
> > +entry:
> > +  %p = alloca i8
> > +  br i1 %flag, label %if.then, label %if.else
> > +
> > +if.then:
> > +  %cmp = icmp uge i32 %blksA, %nblks
> > +  %frombool1 = zext i1 %cmp to i8
> > +  store i8 %frombool1, i8* %p
> > +  br label %if.end
> > +
> > +if.else:
> > +  br i1 %flag2, label %if.then2, label %if.end
> > +
> > +if.then2:
> > +  %add = add i32 %nblks, %blksB
> > +  %cmp2 = icmp ule i32 %add, %blksA
> > +  %frombool3 = zext i1 %cmp2 to i8
> > +  store i8 %frombool3, i8* %p
> > +  br label %if.end
> > +
> > +if.end:
> > +  ret i1 tr
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