redgpu/ispc: Intel® Implicit SPMD Program Compiler

src/gen/GlobalsLocalization.cpp
672 строки25 KB
Arina Neshlyaeva
Fixed getInitializer assertion for GV
28 апр 2021, 10:59
28 апр 2021, 10:592b5c562
/*
  Copyright (c) 2014, 2016-2021, Intel Corporation
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      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.

    * Neither the name of Intel Corporation nor the names of its
      contributors may be used to endorse or promote products derived from
      this software without specific prior written permission.


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   IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
   TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
   PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
   OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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*/

/** @file GlobalsLocalization.cpp
    @brief Localize global variables used in kernels
*/

#ifdef ISPC_GENX_ENABLED
#define DEBUG_TYPE "localize_globals"

#include "GlobalsLocalization.h"

#include <iterator>

#include <llvm/ADT/PostOrderIterator.h>
#include <llvm/ADT/SCCIterator.h>
#include <llvm/ADT/STLExtras.h>
#include <llvm/ADT/SetVector.h>
#include <llvm/ADT/Statistic.h>
#include <llvm/Analysis/CallGraph.h>
#include <llvm/Analysis/CallGraphSCCPass.h>
#include <llvm/Analysis/PostDominators.h>
#include <llvm/GenXIntrinsics/GenXIntrOpts.h>
#include <llvm/GenXIntrinsics/GenXIntrinsics.h>
#include <llvm/GenXIntrinsics/GenXMetadata.h>
#if ISPC_LLVM_VERSION < ISPC_LLVM_11_0
#include <llvm/IR/CallSite.h>
#endif
#include <llvm/IR/CFG.h>
#include <llvm/IR/DebugInfo.h>
#include <llvm/IR/Dominators.h>
#include <llvm/IR/Function.h>
#include <llvm/IR/IRBuilder.h>
#include <llvm/IR/InstIterator.h>
#include <llvm/IR/Intrinsics.h>
#include <llvm/IR/Module.h>
#include <llvm/InitializePasses.h>
#include <llvm/Pass.h>
#include <llvm/Support/CommandLine.h>
#include <llvm/Support/Debug.h>
#include <llvm/Support/raw_ostream.h>
#include <llvm/Transforms/Scalar.h>

using namespace llvm;

using LocalizationLimitT = int32_t;
static constexpr auto LocalizeAll = std::numeric_limits<LocalizationLimitT>::max();
static cl::opt<LocalizationLimitT>
    LocalizationLimit("localization-limit", cl::desc("maximum size (in bytes) used to localize global variables"),
                      cl::init(LocalizeAll));

namespace llvm {
void initializeGlobalsLocalizationPass(PassRegistry &);
} // namespace llvm

/// Localizing global variables
/// ^^^^^^^^^^^^^^^^^^^^^^^^^^^
///
/// General idea of localizing global variables into locals. Globals used in
/// different kernels get a seperate copy and they are always invisiable to
/// other kernels and we can safely localize all globals used (including
/// indirectly) in a kernel. For example,
///
/// .. code-block:: text
///
///   @gv1 = global <8 x float> zeroinitializer, align 32
///   @gv2 = global <8 x float> zeroinitializer, align 32
///   @gv3 = global <8 x float> zeroinitializer, align 32
///
///   define dllexport void @f0() {
///     call @f1()
///     call @f2()
///     call @f3()
///   }
///
///   define internal void @f1() {
///     ; ...
///     store <8 x float> %splat1, <8 x float>* @gv1, align 32
///   }
///
///   define internal void @f2() {
///     ; ...
///     store <8 x float> %splat2, <8 x float>* @gv2, align 32
///   }
///
///   define internal void @f3() {
///     %1 = <8 x float>* @gv1, align 32
///     %2 = <8 x float>* @gv2, align 32
///     %3 = fadd <8 x float> %1, <8 x float> %2
///     store <8 x float> %3, <8 x float>* @gv3, align 32
///   }
///
/// will be transformed into
///
/// .. code-block:: text
///
///   define dllexport void @f0() {
///     %v1 = alloca <8 x float>, align 32
///     %v2 = alloca <8 x float>, align 32
///     %v3 = alloca <8 x float>, align 32
///
///     %0 = load <8 x float> * %v1, align 32
///     %1 = { <8 x float> } call @f1_transformed(<8 x float> %0)
///     %2 = extractvalue { <8 x float> } %1, 0
///     store <8  x float> %2, <8 x float>* %v1, align 32
///
///     %3 = load <8 x float> * %v2, align 32
///     %4 = { <8 x float> } call @f2_transformed(<8 x float> %3)
///     %5 = extractvalue { <8 x float> } %4, 0
///     store <8  x float> %5, <8 x float>* %v1, align 32
///
///     %6 = load <8 x float> * %v1, align 32
///     %7 = load <8 x float> * %v2, align 32
///     %8 = load <8 x float> * %v3, align 32
///
///     %9 = { <8 x float>, <8 x float>, <8 x float> }
///          call @f3_transformed(<8 x float> %6, <8 x float> %7, <8 x float>
///          %8)
///
///     %10 = extractvalue { <8 x float>, <8 x float>, <8 x float> } %9, 0
///     store <8  x float> %10, <8 x float>* %v1, align 32
///     %11 = extractvalue { <8 x float>, <8 x float>, <8 x float> } %9, 1
///     store <8  x float> %11, <8 x float>* %v2, align 32
///     %12 = extractvalue { <8 x float>, <8 x float>, <8 x float> } %9, 2
///     store <8  x float> %12, <8 x float>* %v3, align 32
///   }
///
/// All callees will be updated accordingly, E.g. f1_transformed becomes
///
/// .. code-block:: text
///
///   define internal { <8 x float> } @f1_transformed(<8 x float> %v1) {
///     %0 = alloca <8 x float>, align 32
///     store <8 x float> %v1, <8 x float>* %0, align 32
///     ; ...
///     store <8 x float> %splat1, <8 x float>* @0, align 32
///     ; ...
///     %1 = load <8 x float>* %0, align 32
///     %2 = insertvalue { <8 x float> } undef, <8 x float> %1, 0
///     ret { <8 x float> } %2
///   }
///
namespace {

// \brief Collect necessary information for global variable localization.
class LocalizationInfo {
  public:
    typedef SetVector<GlobalVariable *> GlobalSetTy;

    explicit LocalizationInfo(Function *F) : Fn(F) {}
    LocalizationInfo() : Fn(0) {}

    Function *getFunction() const { return Fn; }
    bool empty() const { return Globals.empty(); }
    GlobalSetTy &getGlobals() { return Globals; }

    // \brief Add a global.
    void addGlobal(GlobalVariable *GV) { Globals.insert(GV); }

    // \brief Add all globals from callee.
    void addGlobals(LocalizationInfo &LI) { Globals.insert(LI.getGlobals().begin(), LI.getGlobals().end()); }

    void setArgIndex(GlobalVariable *GV, unsigned ArgIndex) {
        assert(!IndexMap.count(GV));
        IndexMap[GV] = ArgIndex;
    }
    unsigned getArgIndex(GlobalVariable *GV) const {
        assert(IndexMap.count(GV));
        return IndexMap.lookup(GV);
    }

  private:
    // \brief The function being analyzed.
    Function *Fn;

    // \brief Global variables that are used directly or indirectly.
    GlobalSetTy Globals;

    // This map keeps track of argument index for a global variable.
    SmallDenseMap<GlobalVariable *, unsigned> IndexMap;
};

struct GlobalsLocalization : public CallGraphSCCPass {
    static char ID;

    GlobalsLocalization() : CallGraphSCCPass(ID) {
        initializeGlobalsLocalizationPass(*PassRegistry::getPassRegistry());
    }

    virtual void getAnalysisUsage(AnalysisUsage &AU) const { CallGraphSCCPass::getAnalysisUsage(AU); }

    virtual bool runOnSCC(CallGraphSCC &SCC);

    virtual bool doInitialization(CallGraph &CG);
    virtual bool doFinalization(CallGraph &CG);

  private:
    CallGraphNode *ProcessNode(CallGraphNode *CGN);

    // Fix argument passing for kernels.
    CallGraphNode *TransformKernel(Function *F);

    // \brief Create allocas for globals and replace their uses.
    void LocalizeGlobals(LocalizationInfo &LI);

    // \brief Compute the localized global variables for each function.
    void AnalyzeGlobals(CallGraph &CG);

    // \brief Returns the localization info associated to a function.
    LocalizationInfo &getLocalizationInfo(Function *F) {
        if (!GlobalInfo.count(F)) {
            LocalizationInfo *LI = new LocalizationInfo(F);
            LocalizationInfoObjs.push_back(LI);
            GlobalInfo[F] = LI;
            return *LI;
        }
        return *GlobalInfo[F];
    }

    void addDirectGlobal(Function *F, GlobalVariable *GV) { getLocalizationInfo(F).addGlobal(GV); }

    // \brief Add all globals from callee to caller.
    void addIndirectGlobal(Function *F, Function *Callee) {
        getLocalizationInfo(F).addGlobals(getLocalizationInfo(Callee));
    }

    // This map captures all global variables to be localized.
    SmallDenseMap<Function *, LocalizationInfo *> GlobalInfo;

    // Kernels in the module being processed.
    SmallPtrSet<Function *, 8> Kernels;

    // Already visited functions.
    SmallPtrSet<Function *, 8> AlreadyVisited;

    // LocalizationInfo objects created.
    SmallVector<LocalizationInfo *, 8> LocalizationInfoObjs;
};

} // namespace

template <typename Range> using iterator_t = decltype(std::begin(std::declval<Range &>()));

template <typename Range> using range_pointer_t = typename std::iterator_traits<iterator_t<Range>>::pointer;

template <typename Range> using range_reference_t = typename std::iterator_traits<iterator_t<Range>>::reference;

/* Returns the first iterator (let's name it RetIt) such that
 * std::accumulate(First, RetIt, 0) > Bound (not full truth, read below).
 *
 * Arguments:
 * \p First, \p Last - considered range
 * \p Bound - considered Bound
 * \p Op - functor that returns T, takes T and decltype(*First)
 *    respectively as arguments. It is meant to increment current partial sum.
 *    First argument is previous partial sum, second argument is upcoming value
 *    from the range, new partial sum is returned.
 *
 * Arguments of \p PlusEqualOp may not be equal, so the range may possibly point
 * not to T type. In this case partial sum is calculated for transformed range
 * (transformation is hidden in \p Op).
 */
template <typename ForwardIt, typename PlusEqualOp, typename T>
ForwardIt upperPartialSumBound(ForwardIt First, ForwardIt Last, T Bound, PlusEqualOp Op) {
    T CurSum = 0;
    for (; First != Last; ++First) {
        CurSum = Op(CurSum, *First);
        if (CurSum > Bound)
            return First;
    }
    return Last;
}

// Currently weight of the global defines by its size
static int calcGVWeight(const GlobalVariable &GV, const DataLayout &DL) {
    return DL.getTypeAllocSize(GV.getValueType());
}

/* selectGlobalsToLocalize - chooses which globals to localize
 * Returns vector of pointers to such globals.
 *
 * Algorithm: exclude globals that definitely should not be localized
 * sort globals by weight, choose first smallest ones, sum of which is under \p
 * Bound
 *
 * \p Globals - range of globals to choose from
 * \p Bound - bound not to overcome
 * \p ExcludePred - functor : GVRef -> bool, true if global should not be
 * localized \p WeightCalculator - functor : GVRef -> decltype(Bound), returns
 * weight of global
 */
template <typename ForwardRange, typename ExcludePredT, typename T, typename WeightCalculatorT>
auto selectGlobalsToLocalize(ForwardRange Globals, T Bound, ExcludePredT ExcludePred,
                             WeightCalculatorT WeightCalculator) -> std::vector<range_pointer_t<ForwardRange>> {
    assert(Bound >= 0 && "bound must be nonnegative");
    using GVPtr = range_pointer_t<ForwardRange>;
    using GVRef = range_reference_t<ForwardRange>;
    if (Bound == 0)
        return std::vector<GVPtr>();

    // filter out those, that we must exclude
    auto Unexcluded = make_filter_range(Globals, [ExcludePred](GVRef GV) { return !ExcludePred(GV); });
    using GVWithWeightT = std::pair<GVPtr, int>;

    if (Bound == LocalizeAll) {
        std::vector<GVPtr> ToLocalize;
        transform(Unexcluded, std::back_inserter(ToLocalize), [](GVRef GV) { return &GV; });
        return ToLocalize;
    }

    std::vector<GVWithWeightT> ToLocalizeWithWeight;
    transform(Unexcluded, std::back_inserter(ToLocalizeWithWeight),
              [WeightCalculator](GVRef GV) { return std::make_pair(&GV, WeightCalculator(GV)); });

    // sort globals by weight
    std::sort(ToLocalizeWithWeight.begin(), ToLocalizeWithWeight.end(),
              [](GVWithWeightT LHS, GVWithWeightT RHS) { return LHS.second < RHS.second; });

    // filter max number of lightest ones, which weight sum is under the bound
    auto FirstNotToLocalize =
        upperPartialSumBound(ToLocalizeWithWeight.begin(), ToLocalizeWithWeight.end(), Bound,
                             [](decltype(Bound) Base, GVWithWeightT Inc) { return Base + Inc.second; });

    // collect them back to ToLocalize
    std::vector<GVPtr> ToLocalize;
    ToLocalize.reserve(FirstNotToLocalize - ToLocalizeWithWeight.begin());
    std::transform(ToLocalizeWithWeight.begin(), FirstNotToLocalize, std::back_inserter(ToLocalize),
                   [](GVWithWeightT GV) { return GV.first; });

    return ToLocalize;
}

bool GlobalsLocalization::doInitialization(CallGraph &CG) {
    // Analyze global variable usages and for each function attaches global
    // variables to be copy-in and copy-out.
    AnalyzeGlobals(CG);

    auto getValue = [](Metadata *M) -> Value * {
        if (auto VM = dyn_cast<ValueAsMetadata>(M))
            return VM->getValue();
        return nullptr;
    };

    // Collect all kernels from named metadata.
    if (NamedMDNode *Named = CG.getModule().getNamedMetadata(genx::FunctionMD::GenXKernels)) {
        assert(Named);
        for (unsigned I = 0, E = Named->getNumOperands(); I != E; ++I) {
            MDNode *Node = Named->getOperand(I);
            if (Function *F = dyn_cast_or_null<Function>(getValue(Node->getOperand(0))))
                Kernels.insert(F);
        }
    }

    // no change.
    return false;
}

bool GlobalsLocalization::doFinalization(CallGraph &CG) {
    bool Changed = false;
    for (Module::global_iterator I = CG.getModule().global_begin(); I != CG.getModule().global_end();
         /*empty*/) {
        GlobalVariable *GV = &*I++;
        if (GV->use_empty()) {
            GV->eraseFromParent();
            Changed = true;
        }
    }

    for (LocalizationInfo *Obj : LocalizationInfoObjs)
        delete Obj;

    return Changed;
}

bool GlobalsLocalization::runOnSCC(CallGraphSCC &SCC) {
    bool Changed = false, LocalChange;

    // Iterate until we stop transforming from this SCC.
    do {
        LocalChange = false;
        for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
            if (CallGraphNode *CGN = ProcessNode(*I)) {
                LocalChange = true;
                SCC.ReplaceNode(*I, CGN);
            }
        }
        Changed |= LocalChange;
    } while (LocalChange);

    return Changed;
}

// Sometimes we can get phi with GEP (or maybe some other inst) as an argument.
// While GEP's arguments are constants, its OK as GEP is a constant to.
// But when we replace constants with lokals, GEP becomes a normal instruction,
// a normal instruction, that is placed before phi - wrong IR, we need to fix
// it. Here it is fixed.
static void fixPhiUseIssue(Instruction *Inst) {
    auto PhiUse = cast<PHINode>(Inst->use_begin()->getUser());
    auto InstOpNoInPhi = Inst->use_begin()->getOperandNo();
    assert(Inst->getParent() == PhiUse->getParent());
    Inst->removeFromParent();
    Inst->insertBefore(PhiUse->getIncomingBlock(InstOpNoInPhi)->getTerminator());
}

// Replace uses of global variables with the corresponding allocas with a
// specified function.
//
// Returns vector of instructions with phi use, that should be later fixed.
static std::vector<Instruction *> replaceUsesWithinFunction(SmallDenseMap<Value *, Value *> &GlobalsToReplace,
                                                            Function *F) {
    std::vector<Instruction *> PhiUseIssueInsts;
    for (auto I = inst_begin(F), E = inst_end(F); I != E; ++I) {
        Instruction *Inst = &*I;
        for (unsigned i = 0, e = Inst->getNumOperands(); i < e; ++i) {
            auto Iter = GlobalsToReplace.find(Inst->getOperand(i));
            if (Iter != GlobalsToReplace.end())
                Inst->setOperand(i, Iter->second);
        }
        if (Inst->getNumUses() == 1) {
            auto PhiUse = dyn_cast<PHINode>(Inst->use_begin()->getUser());
            if (PhiUse && Inst->getParent() == PhiUse->getParent()) {
                PhiUseIssueInsts.push_back(Inst);
            }
        }
    }
    return PhiUseIssueInsts;
}

// \brief Create allocas for globals directly used in this kernel and
// replace all uses.
void GlobalsLocalization::LocalizeGlobals(LocalizationInfo &LI) {
    const LocalizationInfo::GlobalSetTy &Globals = LI.getGlobals();
    typedef LocalizationInfo::GlobalSetTy::const_iterator IteratorTy;

    SmallDenseMap<Value *, Value *> GlobalsToReplace;
    Function *Fn = LI.getFunction();
    for (IteratorTy I = Globals.begin(), E = Globals.end(); I != E; ++I) {
        GlobalVariable *GV = (*I);
        LLVM_DEBUG(dbgs() << "Localizing global: " << *GV);

        Instruction &FirstI = *Fn->getEntryBlock().begin();
        Type *ElemTy = GV->getType()->getElementType();
        AllocaInst *Alloca = new AllocaInst(ElemTy, 0, GV->getName() + ".local", &FirstI);
        Alloca->setAlignment(llvm::MaybeAlign(GV->getAlignment()).valueOrOne());

        if (GV->hasInitializer() && !isa<UndefValue>(GV->getInitializer()))
            new StoreInst(GV->getInitializer(), Alloca, &FirstI);

        GlobalsToReplace.insert(std::make_pair(GV, Alloca));
    }

    // Replaces all globals uses within this function.
    auto PhiUseIssueInsts = replaceUsesWithinFunction(GlobalsToReplace, Fn);

    for (auto InstWithPhiUse : PhiUseIssueInsts) {
        fixPhiUseIssue(InstWithPhiUse);
    }

    for (IteratorTy I = Globals.begin(), E = Globals.end(); I != E; ++I) {
        GlobalVariable *GV = (*I);
        if (GV->user_empty())
            GV->eraseFromParent();
    }
}

CallGraphNode *GlobalsLocalization::ProcessNode(CallGraphNode *CGN) {
    Function *F = CGN->getFunction();

    // nothing to do for declarations or already visited functions.
    if (!F || F->isDeclaration() || AlreadyVisited.count(F))
        return 0;

    // Variables to be localized.
    LocalizationInfo &LI = getLocalizationInfo(F);

    // This is a kernel.
    if (Kernels.count(F)) {
        // Localize globals for kernels.
        if (!LI.getGlobals().empty())
            LocalizeGlobals(LI);

        // No changes to this kernel's prototype.
        return 0;
    }
    return 0;
}

static void breakConstantVector(unsigned i, Instruction *CurInst, Instruction *InsertPt) {
    ConstantVector *CV = cast<ConstantVector>(CurInst->getOperand(i));

    // Splat case.
    if (auto S = dyn_cast_or_null<ConstantExpr>(CV->getSplatValue())) {
        // Turn element into an instruction
        auto Inst = S->getAsInstruction();
        Inst->setDebugLoc(CurInst->getDebugLoc());
        Inst->insertBefore(InsertPt);

        // Splat this value.
        IRBuilder<> Builder(InsertPt);
        Value *NewVal = Builder.CreateVectorSplat(CV->getNumOperands(), Inst);

        // Update i-th operand with newly created splat.
        CurInst->setOperand(i, NewVal);
    }

    SmallVector<Value *, 8> Vals;
    bool HasConstExpr = false;
    for (unsigned j = 0, N = CV->getNumOperands(); j < N; ++j) {
        Value *Elt = CV->getOperand(j);
        if (auto CE = dyn_cast<ConstantExpr>(Elt)) {
            auto Inst = CE->getAsInstruction();
            Inst->setDebugLoc(CurInst->getDebugLoc());
            Inst->insertBefore(InsertPt);
            Vals.push_back(Inst);
            HasConstExpr = true;
        } else
            Vals.push_back(Elt);
    }

    if (HasConstExpr) {
        Value *Val = UndefValue::get(CV->getType());
        IRBuilder<> Builder(InsertPt);
        for (unsigned j = 0, N = CV->getNumOperands(); j < N; ++j)
            Val = Builder.CreateInsertElement(Val, Vals[j], j);
        CurInst->setOperand(i, Val);
    }
}

static void breakConstantExprs(Function *F) {
    for (po_iterator<BasicBlock *> i = po_begin(&F->getEntryBlock()), e = po_end(&F->getEntryBlock()); i != e; ++i) {
        BasicBlock *BB = *i;
        // The effect of this loop is that we process the instructions in reverse
        // order, and we re-process anything inserted before the instruction
        // being processed.
        for (Instruction *CurInst = BB->getTerminator(); CurInst;) {
            PHINode *PN = dyn_cast<PHINode>(CurInst);
            for (unsigned i = 0, e = CurInst->getNumOperands(); i < e; ++i) {
                auto InsertPt = PN ? PN->getIncomingBlock(i)->getTerminator() : CurInst;
                Value *Op = CurInst->getOperand(i);
                if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op)) {
                    Instruction *NewInst = CE->getAsInstruction();
                    NewInst->setDebugLoc(CurInst->getDebugLoc());
                    NewInst->insertBefore(CurInst);
                    CurInst->setOperand(i, NewInst);
                } else if (isa<ConstantVector>(Op))
                    breakConstantVector(i, CurInst, InsertPt);
            }
            CurInst = CurInst == &BB->front() ? nullptr : CurInst->getPrevNode();
        }
    }
}

// For each function, compute the list of globals that need to be passed as
// copy-in and copy-out arguments.
void GlobalsLocalization::AnalyzeGlobals(CallGraph &CG) {
    Module &M = CG.getModule();

    // No global variables.
    if (M.global_empty())
        return;

    // Store functions in a SetVector to keep order and make searching efficient.
    SetVector<Function *> Funcs;
    for (auto I = scc_begin(&CG), IE = scc_end(&CG); I != IE; ++I) {
        const std::vector<CallGraphNode *> &SCCNodes = *I;
        for (const CallGraphNode *Node : SCCNodes) {
            Function *F = Node->getFunction();
            if (F != nullptr && !F->isDeclaration()) {
                Funcs.insert(F);
                breakConstantExprs(F);
            }
        }
    }
    auto PrintIndexChecker = [](Use &IUI) {
        CallInst *CI = dyn_cast<CallInst>(IUI.getUser());
        if (!CI)
            return false;
        Function *Callee = CI->getCalledFunction();
        if (!Callee)
            return false;
        unsigned IntrinID = GenXIntrinsic::getAnyIntrinsicID(Callee);
        return (IntrinID == GenXIntrinsic::genx_print_format_index);
    };
    auto UsesPrintChecker = [PrintIndexChecker](const Use &UI) {
        auto *User = UI.getUser();
        return std::any_of(User->use_begin(), User->use_end(), PrintIndexChecker);
    };
    const auto &DL = M.getDataLayout();
    auto ToLocalize = selectGlobalsToLocalize(
        M.globals(), LocalizationLimit.getValue(),
        [UsesPrintChecker](const GlobalVariable &GV) {
            // don't localize global constant format string if it's used by
            // print_index intrinsic
            bool UsesPrintIndex = std::any_of(GV.use_begin(), GV.use_end(), UsesPrintChecker);
            return (GV.hasAttribute(genx::FunctionMD::GenXVolatile) || UsesPrintIndex);
        },
        [&DL](const GlobalVariable &GV) { return calcGVWeight(GV, DL); });
    for (auto I = Funcs.begin(), E = Funcs.end(); I != E; ++I) {
        Function *Fn = *I;
        LLVM_DEBUG(dbgs() << "Visiting " << Fn->getName());

        // Collect globals used directly.
        for (GlobalVariable *GV : ToLocalize) {
            for (Value::use_iterator UI = GV->use_begin(), UE = GV->use_end(); UI != UE; ++UI) {
                Instruction *Inst = dyn_cast<Instruction>(UI->getUser());
                // not used in this function.
                if (!Inst || Inst->getParent()->getParent() != Fn)
                    continue;

                // Find the global being used and populate this info.
                for (unsigned i = 0, e = Inst->getNumOperands(); i < e; ++i) {
                    Value *Op = Inst->getOperand(i);
                    if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op))
                        addDirectGlobal(Fn, GV);
                }
            }
        }

        // Collect globals used indirectly.
        for (inst_iterator II = inst_begin(Fn), IE = inst_end(Fn); II != IE; ++II) {
            Instruction *Inst = &*II;
            // Ignore InvokeInst.
            if (CallInst *CI = dyn_cast<CallInst>(Inst)) {
                // Ignore indirect calls
                if (Function *Callee = CI->getCalledFunction()) {
                    // Collect all globals from its callee.
                    if (!Callee->isDeclaration())
                        addIndirectGlobal(Fn, Callee);
                }
            }
        }
    }
}

char GlobalsLocalization::ID = 0;
INITIALIZE_PASS_BEGIN(GlobalsLocalization, "GlobalsLocalization", "Localize globals before SPIR-V", false, false)
INITIALIZE_PASS_DEPENDENCY(CallGraphWrapperPass)
INITIALIZE_PASS_END(GlobalsLocalization, "GlobalsLocalization", "Localize globals before SPIR-V", false, false)

Pass *llvm::createGlobalsLocalizationPass() { return new GlobalsLocalization(); }
#endif