| //===-- GlobalMerge.cpp - Internal globals merging -----------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // This pass merges globals with internal linkage into one. This way all the |
| // globals which were merged into a biggest one can be addressed using offsets |
| // from the same base pointer (no need for separate base pointer for each of the |
| // global). Such a transformation can significantly reduce the register pressure |
| // when many globals are involved. |
| // |
| // For example, consider the code which touches several global variables at |
| // once: |
| // |
| // static int foo[N], bar[N], baz[N]; |
| // |
| // for (i = 0; i < N; ++i) { |
| // foo[i] = bar[i] * baz[i]; |
| // } |
| // |
| // On ARM the addresses of 3 arrays should be kept in the registers, thus |
| // this code has quite large register pressure (loop body): |
| // |
| // ldr r1, [r5], #4 |
| // ldr r2, [r6], #4 |
| // mul r1, r2, r1 |
| // str r1, [r0], #4 |
| // |
| // Pass converts the code to something like: |
| // |
| // static struct { |
| // int foo[N]; |
| // int bar[N]; |
| // int baz[N]; |
| // } merged; |
| // |
| // for (i = 0; i < N; ++i) { |
| // merged.foo[i] = merged.bar[i] * merged.baz[i]; |
| // } |
| // |
| // and in ARM code this becomes: |
| // |
| // ldr r0, [r5, #40] |
| // ldr r1, [r5, #80] |
| // mul r0, r1, r0 |
| // str r0, [r5], #4 |
| // |
| // note that we saved 2 registers here almostly "for free". |
| // |
| // However, merging globals can have tradeoffs: |
| // - it confuses debuggers, tools, and users |
| // - it makes linker optimizations less useful (order files, LOHs, ...) |
| // - it forces usage of indexed addressing (which isn't necessarily "free") |
| // - it can increase register pressure when the uses are disparate enough. |
| // |
| // We use heuristics to discover the best global grouping we can (cf cl::opts). |
| // ===---------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/SmallBitVector.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/CodeGen/Passes.h" |
| #include "llvm/IR/Attributes.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/GlobalVariable.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/Intrinsics.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetLowering.h" |
| #include "llvm/Target/TargetLoweringObjectFile.h" |
| #include "llvm/Target/TargetSubtargetInfo.h" |
| #include <algorithm> |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "global-merge" |
| |
| // FIXME: This is only useful as a last-resort way to disable the pass. |
| static cl::opt<bool> |
| EnableGlobalMerge("enable-global-merge", cl::Hidden, |
| cl::desc("Enable the global merge pass"), |
| cl::init(true)); |
| |
| static cl::opt<bool> GlobalMergeGroupByUse( |
| "global-merge-group-by-use", cl::Hidden, |
| cl::desc("Improve global merge pass to look at uses"), cl::init(true)); |
| |
| static cl::opt<bool> GlobalMergeIgnoreSingleUse( |
| "global-merge-ignore-single-use", cl::Hidden, |
| cl::desc("Improve global merge pass to ignore globals only used alone"), |
| cl::init(true)); |
| |
| static cl::opt<bool> |
| EnableGlobalMergeOnConst("global-merge-on-const", cl::Hidden, |
| cl::desc("Enable global merge pass on constants"), |
| cl::init(false)); |
| |
| // FIXME: this could be a transitional option, and we probably need to remove |
| // it if only we are sure this optimization could always benefit all targets. |
| static cl::opt<bool> |
| EnableGlobalMergeOnExternal("global-merge-on-external", cl::Hidden, |
| cl::desc("Enable global merge pass on external linkage"), |
| cl::init(false)); |
| |
| STATISTIC(NumMerged, "Number of globals merged"); |
| namespace { |
| class GlobalMerge : public FunctionPass { |
| const TargetMachine *TM; |
| // FIXME: Infer the maximum possible offset depending on the actual users |
| // (these max offsets are different for the users inside Thumb or ARM |
| // functions), see the code that passes in the offset in the ARM backend |
| // for more information. |
| unsigned MaxOffset; |
| |
| /// Whether we should try to optimize for size only. |
| /// Currently, this applies a dead simple heuristic: only consider globals |
| /// used in minsize functions for merging. |
| /// FIXME: This could learn about optsize, and be used in the cost model. |
| bool OnlyOptimizeForSize; |
| |
| bool doMerge(SmallVectorImpl<GlobalVariable*> &Globals, |
| Module &M, bool isConst, unsigned AddrSpace) const; |
| /// \brief Merge everything in \p Globals for which the corresponding bit |
| /// in \p GlobalSet is set. |
| bool doMerge(SmallVectorImpl<GlobalVariable *> &Globals, |
| const BitVector &GlobalSet, Module &M, bool isConst, |
| unsigned AddrSpace) const; |
| |
| /// \brief Check if the given variable has been identified as must keep |
| /// \pre setMustKeepGlobalVariables must have been called on the Module that |
| /// contains GV |
| bool isMustKeepGlobalVariable(const GlobalVariable *GV) const { |
| return MustKeepGlobalVariables.count(GV); |
| } |
| |
| /// Collect every variables marked as "used" or used in a landing pad |
| /// instruction for this Module. |
| void setMustKeepGlobalVariables(Module &M); |
| |
| /// Collect every variables marked as "used" |
| void collectUsedGlobalVariables(Module &M); |
| |
| /// Keep track of the GlobalVariable that must not be merged away |
| SmallPtrSet<const GlobalVariable *, 16> MustKeepGlobalVariables; |
| |
| public: |
| static char ID; // Pass identification, replacement for typeid. |
| explicit GlobalMerge(const TargetMachine *TM = nullptr, |
| unsigned MaximalOffset = 0, |
| bool OnlyOptimizeForSize = false) |
| : FunctionPass(ID), TM(TM), MaxOffset(MaximalOffset), |
| OnlyOptimizeForSize(OnlyOptimizeForSize) { |
| initializeGlobalMergePass(*PassRegistry::getPassRegistry()); |
| } |
| |
| bool doInitialization(Module &M) override; |
| bool runOnFunction(Function &F) override; |
| bool doFinalization(Module &M) override; |
| |
| const char *getPassName() const override { |
| return "Merge internal globals"; |
| } |
| |
| void getAnalysisUsage(AnalysisUsage &AU) const override { |
| AU.setPreservesCFG(); |
| FunctionPass::getAnalysisUsage(AU); |
| } |
| }; |
| } // end anonymous namespace |
| |
| char GlobalMerge::ID = 0; |
| INITIALIZE_PASS_BEGIN(GlobalMerge, "global-merge", "Merge global variables", |
| false, false) |
| INITIALIZE_PASS_END(GlobalMerge, "global-merge", "Merge global variables", |
| false, false) |
| |
| bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable*> &Globals, |
| Module &M, bool isConst, unsigned AddrSpace) const { |
| auto &DL = M.getDataLayout(); |
| // FIXME: Find better heuristics |
| std::stable_sort( |
| Globals.begin(), Globals.end(), |
| [&DL](const GlobalVariable *GV1, const GlobalVariable *GV2) { |
| Type *Ty1 = cast<PointerType>(GV1->getType())->getElementType(); |
| Type *Ty2 = cast<PointerType>(GV2->getType())->getElementType(); |
| |
| return (DL.getTypeAllocSize(Ty1) < DL.getTypeAllocSize(Ty2)); |
| }); |
| |
| // If we want to just blindly group all globals together, do so. |
| if (!GlobalMergeGroupByUse) { |
| BitVector AllGlobals(Globals.size()); |
| AllGlobals.set(); |
| return doMerge(Globals, AllGlobals, M, isConst, AddrSpace); |
| } |
| |
| // If we want to be smarter, look at all uses of each global, to try to |
| // discover all sets of globals used together, and how many times each of |
| // these sets occured. |
| // |
| // Keep this reasonably efficient, by having an append-only list of all sets |
| // discovered so far (UsedGlobalSet), and mapping each "together-ness" unit of |
| // code (currently, a Function) to the set of globals seen so far that are |
| // used together in that unit (GlobalUsesByFunction). |
| // |
| // When we look at the Nth global, we now that any new set is either: |
| // - the singleton set {N}, containing this global only, or |
| // - the union of {N} and a previously-discovered set, containing some |
| // combination of the previous N-1 globals. |
| // Using that knowledge, when looking at the Nth global, we can keep: |
| // - a reference to the singleton set {N} (CurGVOnlySetIdx) |
| // - a list mapping each previous set to its union with {N} (EncounteredUGS), |
| // if it actually occurs. |
| |
| // We keep track of the sets of globals used together "close enough". |
| struct UsedGlobalSet { |
| UsedGlobalSet(size_t Size) : Globals(Size), UsageCount(1) {} |
| BitVector Globals; |
| unsigned UsageCount; |
| }; |
| |
| // Each set is unique in UsedGlobalSets. |
| std::vector<UsedGlobalSet> UsedGlobalSets; |
| |
| // Avoid repeating the create-global-set pattern. |
| auto CreateGlobalSet = [&]() -> UsedGlobalSet & { |
| UsedGlobalSets.emplace_back(Globals.size()); |
| return UsedGlobalSets.back(); |
| }; |
| |
| // The first set is the empty set. |
| CreateGlobalSet().UsageCount = 0; |
| |
| // We define "close enough" to be "in the same function". |
| // FIXME: Grouping uses by function is way too aggressive, so we should have |
| // a better metric for distance between uses. |
| // The obvious alternative would be to group by BasicBlock, but that's in |
| // turn too conservative.. |
| // Anything in between wouldn't be trivial to compute, so just stick with |
| // per-function grouping. |
| |
| // The value type is an index into UsedGlobalSets. |
| // The default (0) conveniently points to the empty set. |
| DenseMap<Function *, size_t /*UsedGlobalSetIdx*/> GlobalUsesByFunction; |
| |
| // Now, look at each merge-eligible global in turn. |
| |
| // Keep track of the sets we already encountered to which we added the |
| // current global. |
| // Each element matches the same-index element in UsedGlobalSets. |
| // This lets us efficiently tell whether a set has already been expanded to |
| // include the current global. |
| std::vector<size_t> EncounteredUGS; |
| |
| for (size_t GI = 0, GE = Globals.size(); GI != GE; ++GI) { |
| GlobalVariable *GV = Globals[GI]; |
| |
| // Reset the encountered sets for this global... |
| std::fill(EncounteredUGS.begin(), EncounteredUGS.end(), 0); |
| // ...and grow it in case we created new sets for the previous global. |
| EncounteredUGS.resize(UsedGlobalSets.size()); |
| |
| // We might need to create a set that only consists of the current global. |
| // Keep track of its index into UsedGlobalSets. |
| size_t CurGVOnlySetIdx = 0; |
| |
| // For each global, look at all its Uses. |
| for (auto &U : GV->uses()) { |
| // This Use might be a ConstantExpr. We're interested in Instruction |
| // users, so look through ConstantExpr... |
| Use *UI, *UE; |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U.getUser())) { |
| if (CE->use_empty()) |
| continue; |
| UI = &*CE->use_begin(); |
| UE = nullptr; |
| } else if (isa<Instruction>(U.getUser())) { |
| UI = &U; |
| UE = UI->getNext(); |
| } else { |
| continue; |
| } |
| |
| // ...to iterate on all the instruction users of the global. |
| // Note that we iterate on Uses and not on Users to be able to getNext(). |
| for (; UI != UE; UI = UI->getNext()) { |
| Instruction *I = dyn_cast<Instruction>(UI->getUser()); |
| if (!I) |
| continue; |
| |
| Function *ParentFn = I->getParent()->getParent(); |
| |
| // If we're only optimizing for size, ignore non-minsize functions. |
| if (OnlyOptimizeForSize && |
| !ParentFn->hasFnAttribute(Attribute::MinSize)) |
| continue; |
| |
| size_t UGSIdx = GlobalUsesByFunction[ParentFn]; |
| |
| // If this is the first global the basic block uses, map it to the set |
| // consisting of this global only. |
| if (!UGSIdx) { |
| // If that set doesn't exist yet, create it. |
| if (!CurGVOnlySetIdx) { |
| CurGVOnlySetIdx = UsedGlobalSets.size(); |
| CreateGlobalSet().Globals.set(GI); |
| } else { |
| ++UsedGlobalSets[CurGVOnlySetIdx].UsageCount; |
| } |
| |
| GlobalUsesByFunction[ParentFn] = CurGVOnlySetIdx; |
| continue; |
| } |
| |
| // If we already encountered this BB, just increment the counter. |
| if (UsedGlobalSets[UGSIdx].Globals.test(GI)) { |
| ++UsedGlobalSets[UGSIdx].UsageCount; |
| continue; |
| } |
| |
| // If not, the previous set wasn't actually used in this function. |
| --UsedGlobalSets[UGSIdx].UsageCount; |
| |
| // If we already expanded the previous set to include this global, just |
| // reuse that expanded set. |
| if (size_t ExpandedIdx = EncounteredUGS[UGSIdx]) { |
| ++UsedGlobalSets[ExpandedIdx].UsageCount; |
| GlobalUsesByFunction[ParentFn] = ExpandedIdx; |
| continue; |
| } |
| |
| // If not, create a new set consisting of the union of the previous set |
| // and this global. Mark it as encountered, so we can reuse it later. |
| GlobalUsesByFunction[ParentFn] = EncounteredUGS[UGSIdx] = |
| UsedGlobalSets.size(); |
| |
| UsedGlobalSet &NewUGS = CreateGlobalSet(); |
| NewUGS.Globals.set(GI); |
| NewUGS.Globals |= UsedGlobalSets[UGSIdx].Globals; |
| } |
| } |
| } |
| |
| // Now we found a bunch of sets of globals used together. We accumulated |
| // the number of times we encountered the sets (i.e., the number of blocks |
| // that use that exact set of globals). |
| // |
| // Multiply that by the size of the set to give us a crude profitability |
| // metric. |
| std::sort(UsedGlobalSets.begin(), UsedGlobalSets.end(), |
| [](const UsedGlobalSet &UGS1, const UsedGlobalSet &UGS2) { |
| return UGS1.Globals.count() * UGS1.UsageCount < |
| UGS2.Globals.count() * UGS2.UsageCount; |
| }); |
| |
| // We can choose to merge all globals together, but ignore globals never used |
| // with another global. This catches the obviously non-profitable cases of |
| // having a single global, but is aggressive enough for any other case. |
| if (GlobalMergeIgnoreSingleUse) { |
| BitVector AllGlobals(Globals.size()); |
| for (size_t i = 0, e = UsedGlobalSets.size(); i != e; ++i) { |
| const UsedGlobalSet &UGS = UsedGlobalSets[e - i - 1]; |
| if (UGS.UsageCount == 0) |
| continue; |
| if (UGS.Globals.count() > 1) |
| AllGlobals |= UGS.Globals; |
| } |
| return doMerge(Globals, AllGlobals, M, isConst, AddrSpace); |
| } |
| |
| // Starting from the sets with the best (=biggest) profitability, find a |
| // good combination. |
| // The ideal (and expensive) solution can only be found by trying all |
| // combinations, looking for the one with the best profitability. |
| // Don't be smart about it, and just pick the first compatible combination, |
| // starting with the sets with the best profitability. |
| BitVector PickedGlobals(Globals.size()); |
| bool Changed = false; |
| |
| for (size_t i = 0, e = UsedGlobalSets.size(); i != e; ++i) { |
| const UsedGlobalSet &UGS = UsedGlobalSets[e - i - 1]; |
| if (UGS.UsageCount == 0) |
| continue; |
| if (PickedGlobals.anyCommon(UGS.Globals)) |
| continue; |
| PickedGlobals |= UGS.Globals; |
| // If the set only contains one global, there's no point in merging. |
| // Ignore the global for inclusion in other sets though, so keep it in |
| // PickedGlobals. |
| if (UGS.Globals.count() < 2) |
| continue; |
| Changed |= doMerge(Globals, UGS.Globals, M, isConst, AddrSpace); |
| } |
| |
| return Changed; |
| } |
| |
| bool GlobalMerge::doMerge(SmallVectorImpl<GlobalVariable *> &Globals, |
| const BitVector &GlobalSet, Module &M, bool isConst, |
| unsigned AddrSpace) const { |
| |
| Type *Int32Ty = Type::getInt32Ty(M.getContext()); |
| auto &DL = M.getDataLayout(); |
| |
| assert(Globals.size() > 1); |
| |
| DEBUG(dbgs() << " Trying to merge set, starts with #" |
| << GlobalSet.find_first() << "\n"); |
| |
| ssize_t i = GlobalSet.find_first(); |
| while (i != -1) { |
| ssize_t j = 0; |
| uint64_t MergedSize = 0; |
| std::vector<Type*> Tys; |
| std::vector<Constant*> Inits; |
| |
| bool HasExternal = false; |
| GlobalVariable *TheFirstExternal = 0; |
| for (j = i; j != -1; j = GlobalSet.find_next(j)) { |
| Type *Ty = Globals[j]->getType()->getElementType(); |
| MergedSize += DL.getTypeAllocSize(Ty); |
| if (MergedSize > MaxOffset) { |
| break; |
| } |
| Tys.push_back(Ty); |
| Inits.push_back(Globals[j]->getInitializer()); |
| |
| if (Globals[j]->hasExternalLinkage() && !HasExternal) { |
| HasExternal = true; |
| TheFirstExternal = Globals[j]; |
| } |
| } |
| |
| // If merged variables doesn't have external linkage, we needn't to expose |
| // the symbol after merging. |
| GlobalValue::LinkageTypes Linkage = HasExternal |
| ? GlobalValue::ExternalLinkage |
| : GlobalValue::InternalLinkage; |
| |
| StructType *MergedTy = StructType::get(M.getContext(), Tys); |
| Constant *MergedInit = ConstantStruct::get(MergedTy, Inits); |
| |
| // If merged variables have external linkage, we use symbol name of the |
| // first variable merged as the suffix of global symbol name. This would |
| // be able to avoid the link-time naming conflict for globalm symbols. |
| GlobalVariable *MergedGV = new GlobalVariable( |
| M, MergedTy, isConst, Linkage, MergedInit, |
| HasExternal ? "_MergedGlobals_" + TheFirstExternal->getName() |
| : "_MergedGlobals", |
| nullptr, GlobalVariable::NotThreadLocal, AddrSpace); |
| |
| for (ssize_t k = i, idx = 0; k != j; k = GlobalSet.find_next(k)) { |
| GlobalValue::LinkageTypes Linkage = Globals[k]->getLinkage(); |
| std::string Name = Globals[k]->getName(); |
| |
| Constant *Idx[2] = { |
| ConstantInt::get(Int32Ty, 0), |
| ConstantInt::get(Int32Ty, idx++) |
| }; |
| Constant *GEP = |
| ConstantExpr::getInBoundsGetElementPtr(MergedTy, MergedGV, Idx); |
| Globals[k]->replaceAllUsesWith(GEP); |
| Globals[k]->eraseFromParent(); |
| |
| if (Linkage != GlobalValue::InternalLinkage) { |
| // Generate a new alias... |
| auto *PTy = cast<PointerType>(GEP->getType()); |
| GlobalAlias::create(PTy, Linkage, Name, GEP, &M); |
| } |
| |
| NumMerged++; |
| } |
| i = j; |
| } |
| |
| return true; |
| } |
| |
| void GlobalMerge::collectUsedGlobalVariables(Module &M) { |
| // Extract global variables from llvm.used array |
| const GlobalVariable *GV = M.getGlobalVariable("llvm.used"); |
| if (!GV || !GV->hasInitializer()) return; |
| |
| // Should be an array of 'i8*'. |
| const ConstantArray *InitList = cast<ConstantArray>(GV->getInitializer()); |
| |
| for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) |
| if (const GlobalVariable *G = |
| dyn_cast<GlobalVariable>(InitList->getOperand(i)->stripPointerCasts())) |
| MustKeepGlobalVariables.insert(G); |
| } |
| |
| void GlobalMerge::setMustKeepGlobalVariables(Module &M) { |
| collectUsedGlobalVariables(M); |
| |
| for (Module::iterator IFn = M.begin(), IEndFn = M.end(); IFn != IEndFn; |
| ++IFn) { |
| for (Function::iterator IBB = IFn->begin(), IEndBB = IFn->end(); |
| IBB != IEndBB; ++IBB) { |
| // Follow the invoke link to find the landing pad instruction |
| const InvokeInst *II = dyn_cast<InvokeInst>(IBB->getTerminator()); |
| if (!II) continue; |
| |
| const LandingPadInst *LPInst = II->getUnwindDest()->getLandingPadInst(); |
| // Look for globals in the clauses of the landing pad instruction |
| for (unsigned Idx = 0, NumClauses = LPInst->getNumClauses(); |
| Idx != NumClauses; ++Idx) |
| if (const GlobalVariable *GV = |
| dyn_cast<GlobalVariable>(LPInst->getClause(Idx) |
| ->stripPointerCasts())) |
| MustKeepGlobalVariables.insert(GV); |
| } |
| } |
| } |
| |
| bool GlobalMerge::doInitialization(Module &M) { |
| if (!EnableGlobalMerge) |
| return false; |
| |
| auto &DL = M.getDataLayout(); |
| DenseMap<unsigned, SmallVector<GlobalVariable*, 16> > Globals, ConstGlobals, |
| BSSGlobals; |
| bool Changed = false; |
| setMustKeepGlobalVariables(M); |
| |
| // Grab all non-const globals. |
| for (Module::global_iterator I = M.global_begin(), |
| E = M.global_end(); I != E; ++I) { |
| // Merge is safe for "normal" internal or external globals only |
| if (I->isDeclaration() || I->isThreadLocal() || I->hasSection()) |
| continue; |
| |
| if (!(EnableGlobalMergeOnExternal && I->hasExternalLinkage()) && |
| !I->hasInternalLinkage()) |
| continue; |
| |
| PointerType *PT = dyn_cast<PointerType>(I->getType()); |
| assert(PT && "Global variable is not a pointer!"); |
| |
| unsigned AddressSpace = PT->getAddressSpace(); |
| |
| // Ignore fancy-aligned globals for now. |
| unsigned Alignment = DL.getPreferredAlignment(I); |
| Type *Ty = I->getType()->getElementType(); |
| if (Alignment > DL.getABITypeAlignment(Ty)) |
| continue; |
| |
| // Ignore all 'special' globals. |
| if (I->getName().startswith("llvm.") || |
| I->getName().startswith(".llvm.")) |
| continue; |
| |
| // Ignore all "required" globals: |
| if (isMustKeepGlobalVariable(I)) |
| continue; |
| |
| if (DL.getTypeAllocSize(Ty) < MaxOffset) { |
| if (TargetLoweringObjectFile::getKindForGlobal(I, *TM).isBSSLocal()) |
| BSSGlobals[AddressSpace].push_back(I); |
| else if (I->isConstant()) |
| ConstGlobals[AddressSpace].push_back(I); |
| else |
| Globals[AddressSpace].push_back(I); |
| } |
| } |
| |
| for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator |
| I = Globals.begin(), E = Globals.end(); I != E; ++I) |
| if (I->second.size() > 1) |
| Changed |= doMerge(I->second, M, false, I->first); |
| |
| for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator |
| I = BSSGlobals.begin(), E = BSSGlobals.end(); I != E; ++I) |
| if (I->second.size() > 1) |
| Changed |= doMerge(I->second, M, false, I->first); |
| |
| if (EnableGlobalMergeOnConst) |
| for (DenseMap<unsigned, SmallVector<GlobalVariable*, 16> >::iterator |
| I = ConstGlobals.begin(), E = ConstGlobals.end(); I != E; ++I) |
| if (I->second.size() > 1) |
| Changed |= doMerge(I->second, M, true, I->first); |
| |
| return Changed; |
| } |
| |
| bool GlobalMerge::runOnFunction(Function &F) { |
| return false; |
| } |
| |
| bool GlobalMerge::doFinalization(Module &M) { |
| MustKeepGlobalVariables.clear(); |
| return false; |
| } |
| |
| Pass *llvm::createGlobalMergePass(const TargetMachine *TM, unsigned Offset, |
| bool OnlyOptimizeForSize) { |
| return new GlobalMerge(TM, Offset, OnlyOptimizeForSize); |
| } |