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Diffstat (limited to 'contrib/llvm/lib/CodeGen/GlobalMerge.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/GlobalMerge.cpp | 681 |
1 files changed, 0 insertions, 681 deletions
diff --git a/contrib/llvm/lib/CodeGen/GlobalMerge.cpp b/contrib/llvm/lib/CodeGen/GlobalMerge.cpp deleted file mode 100644 index 09201c2e7bae..000000000000 --- a/contrib/llvm/lib/CodeGen/GlobalMerge.cpp +++ /dev/null @@ -1,681 +0,0 @@ -//===- GlobalMerge.cpp - Internal globals merging -------------------------===// -// -// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. -// See https://llvm.org/LICENSE.txt for license information. -// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception -// -//===----------------------------------------------------------------------===// -// -// 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/ADT/BitVector.h" -#include "llvm/ADT/DenseMap.h" -#include "llvm/ADT/SmallPtrSet.h" -#include "llvm/ADT/SmallVector.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/ADT/StringRef.h" -#include "llvm/ADT/Triple.h" -#include "llvm/ADT/Twine.h" -#include "llvm/CodeGen/Passes.h" -#include "llvm/IR/BasicBlock.h" -#include "llvm/IR/Constants.h" -#include "llvm/IR/DataLayout.h" -#include "llvm/IR/DerivedTypes.h" -#include "llvm/IR/Function.h" -#include "llvm/IR/GlobalAlias.h" -#include "llvm/IR/GlobalValue.h" -#include "llvm/IR/GlobalVariable.h" -#include "llvm/IR/Instruction.h" -#include "llvm/IR/Module.h" -#include "llvm/IR/Type.h" -#include "llvm/IR/Use.h" -#include "llvm/IR/User.h" -#include "llvm/Pass.h" -#include "llvm/Support/Casting.h" -#include "llvm/Support/CommandLine.h" -#include "llvm/Support/Debug.h" -#include "llvm/Support/raw_ostream.h" -#include "llvm/Target/TargetLoweringObjectFile.h" -#include "llvm/Target/TargetMachine.h" -#include <algorithm> -#include <cassert> -#include <cstddef> -#include <cstdint> -#include <string> -#include <vector> - -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<unsigned> -GlobalMergeMaxOffset("global-merge-max-offset", cl::Hidden, - cl::desc("Set maximum offset for global merge pass"), - cl::init(0)); - -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<cl::boolOrDefault> -EnableGlobalMergeOnExternal("global-merge-on-external", cl::Hidden, - cl::desc("Enable global merge pass on external linkage")); - -STATISTIC(NumMerged, "Number of globals merged"); - -namespace { - - class GlobalMerge : public FunctionPass { - const TargetMachine *TM = nullptr; - - // 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 = false; - - /// Whether we should merge global variables that have external linkage. - bool MergeExternalGlobals = false; - - bool IsMachO; - - bool doMerge(SmallVectorImpl<GlobalVariable*> &Globals, - Module &M, bool isConst, unsigned AddrSpace) const; - - /// Merge everything in \p Globals for which the corresponding bit - /// in \p GlobalSet is set. - bool doMerge(const SmallVectorImpl<GlobalVariable *> &Globals, - const BitVector &GlobalSet, Module &M, bool isConst, - unsigned AddrSpace) const; - - /// 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, StringRef Name); - - /// 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() - : FunctionPass(ID), MaxOffset(GlobalMergeMaxOffset) { - initializeGlobalMergePass(*PassRegistry::getPassRegistry()); - } - - explicit GlobalMerge(const TargetMachine *TM, unsigned MaximalOffset, - bool OnlyOptimizeForSize, bool MergeExternalGlobals) - : FunctionPass(ID), TM(TM), MaxOffset(MaximalOffset), - OnlyOptimizeForSize(OnlyOptimizeForSize), - MergeExternalGlobals(MergeExternalGlobals) { - initializeGlobalMergePass(*PassRegistry::getPassRegistry()); - } - - bool doInitialization(Module &M) override; - bool runOnFunction(Function &F) override; - bool doFinalization(Module &M) override; - - StringRef 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(GlobalMerge, DEBUG_TYPE, "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 - llvm::stable_sort( - Globals, [&DL](const GlobalVariable *GV1, const GlobalVariable *GV2) { - return DL.getTypeAllocSize(GV1->getValueType()) < - DL.getTypeAllocSize(GV2->getValueType()); - }); - - // 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 occurred. - // - // 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 know 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 { - BitVector Globals; - unsigned UsageCount = 1; - - UsedGlobalSet(size_t Size) : Globals(Size) {} - }; - - // 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->hasMinSize()) - 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. - llvm::stable_sort(UsedGlobalSets, - [](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(const SmallVectorImpl<GlobalVariable *> &Globals, - const BitVector &GlobalSet, Module &M, bool isConst, - unsigned AddrSpace) const { - assert(Globals.size() > 1); - - Type *Int32Ty = Type::getInt32Ty(M.getContext()); - Type *Int8Ty = Type::getInt8Ty(M.getContext()); - auto &DL = M.getDataLayout(); - - LLVM_DEBUG(dbgs() << " Trying to merge set, starts with #" - << GlobalSet.find_first() << "\n"); - - bool Changed = false; - 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; - std::vector<unsigned> StructIdxs; - - bool HasExternal = false; - StringRef FirstExternalName; - unsigned MaxAlign = 1; - unsigned CurIdx = 0; - for (j = i; j != -1; j = GlobalSet.find_next(j)) { - Type *Ty = Globals[j]->getValueType(); - - // Make sure we use the same alignment AsmPrinter would use. - unsigned Align = DL.getPreferredAlignment(Globals[j]); - unsigned Padding = alignTo(MergedSize, Align) - MergedSize; - MergedSize += Padding; - MergedSize += DL.getTypeAllocSize(Ty); - if (MergedSize > MaxOffset) { - break; - } - if (Padding) { - Tys.push_back(ArrayType::get(Int8Ty, Padding)); - Inits.push_back(ConstantAggregateZero::get(Tys.back())); - ++CurIdx; - } - Tys.push_back(Ty); - Inits.push_back(Globals[j]->getInitializer()); - StructIdxs.push_back(CurIdx++); - - MaxAlign = std::max(MaxAlign, Align); - - if (Globals[j]->hasExternalLinkage() && !HasExternal) { - HasExternal = true; - FirstExternalName = Globals[j]->getName(); - } - } - - // Exit early if there is only one global to merge. - if (Tys.size() < 2) { - i = j; - continue; - } - - // 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; - // Use a packed struct so we can control alignment. - StructType *MergedTy = StructType::get(M.getContext(), Tys, true); - Constant *MergedInit = ConstantStruct::get(MergedTy, Inits); - - // On Darwin external linkage needs to be preserved, otherwise - // dsymutil cannot preserve the debug info for the merged - // variables. If they have external linkage, use the symbol name - // of the first variable merged as the suffix of global symbol - // name. This avoids a link-time naming conflict for the - // _MergedGlobals symbols. - Twine MergedName = - (IsMachO && HasExternal) - ? "_MergedGlobals_" + FirstExternalName - : "_MergedGlobals"; - auto MergedLinkage = IsMachO ? Linkage : GlobalValue::PrivateLinkage; - auto *MergedGV = new GlobalVariable( - M, MergedTy, isConst, MergedLinkage, MergedInit, MergedName, nullptr, - GlobalVariable::NotThreadLocal, AddrSpace); - - MergedGV->setAlignment(MaxAlign); - MergedGV->setSection(Globals[i]->getSection()); - - const StructLayout *MergedLayout = DL.getStructLayout(MergedTy); - for (ssize_t k = i, idx = 0; k != j; k = GlobalSet.find_next(k), ++idx) { - GlobalValue::LinkageTypes Linkage = Globals[k]->getLinkage(); - std::string Name = Globals[k]->getName(); - GlobalValue::DLLStorageClassTypes DLLStorage = - Globals[k]->getDLLStorageClass(); - - // Copy metadata while adjusting any debug info metadata by the original - // global's offset within the merged global. - MergedGV->copyMetadata(Globals[k], - MergedLayout->getElementOffset(StructIdxs[idx])); - - Constant *Idx[2] = { - ConstantInt::get(Int32Ty, 0), - ConstantInt::get(Int32Ty, StructIdxs[idx]), - }; - Constant *GEP = - ConstantExpr::getInBoundsGetElementPtr(MergedTy, MergedGV, Idx); - Globals[k]->replaceAllUsesWith(GEP); - Globals[k]->eraseFromParent(); - - // When the linkage is not internal we must emit an alias for the original - // variable name as it may be accessed from another object. On non-Mach-O - // we can also emit an alias for internal linkage as it's safe to do so. - // It's not safe on Mach-O as the alias (and thus the portion of the - // MergedGlobals variable) may be dead stripped at link time. - if (Linkage != GlobalValue::InternalLinkage || !IsMachO) { - GlobalAlias *GA = GlobalAlias::create(Tys[StructIdxs[idx]], AddrSpace, - Linkage, Name, GEP, &M); - GA->setDLLStorageClass(DLLStorage); - } - - NumMerged++; - } - Changed = true; - i = j; - } - - return Changed; -} - -void GlobalMerge::collectUsedGlobalVariables(Module &M, StringRef Name) { - // Extract global variables from llvm.used array - const GlobalVariable *GV = M.getGlobalVariable(Name); - 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, "llvm.used"); - collectUsedGlobalVariables(M, "llvm.compiler.used"); - - for (Function &F : M) { - for (BasicBlock &BB : F) { - Instruction *Pad = BB.getFirstNonPHI(); - if (!Pad->isEHPad()) - continue; - - // Keep globals used by landingpads and catchpads. - for (const Use &U : Pad->operands()) { - if (const GlobalVariable *GV = - dyn_cast<GlobalVariable>(U->stripPointerCasts())) - MustKeepGlobalVariables.insert(GV); - } - } - } -} - -bool GlobalMerge::doInitialization(Module &M) { - if (!EnableGlobalMerge) - return false; - - IsMachO = Triple(M.getTargetTriple()).isOSBinFormatMachO(); - - auto &DL = M.getDataLayout(); - DenseMap<std::pair<unsigned, StringRef>, SmallVector<GlobalVariable *, 16>> - Globals, ConstGlobals, BSSGlobals; - bool Changed = false; - setMustKeepGlobalVariables(M); - - // Grab all non-const globals. - for (auto &GV : M.globals()) { - // Merge is safe for "normal" internal or external globals only - if (GV.isDeclaration() || GV.isThreadLocal() || GV.hasImplicitSection()) - continue; - - // It's not safe to merge globals that may be preempted - if (TM && !TM->shouldAssumeDSOLocal(M, &GV)) - continue; - - if (!(MergeExternalGlobals && GV.hasExternalLinkage()) && - !GV.hasInternalLinkage()) - continue; - - PointerType *PT = dyn_cast<PointerType>(GV.getType()); - assert(PT && "Global variable is not a pointer!"); - - unsigned AddressSpace = PT->getAddressSpace(); - StringRef Section = GV.getSection(); - - // Ignore all 'special' globals. - if (GV.getName().startswith("llvm.") || - GV.getName().startswith(".llvm.")) - continue; - - // Ignore all "required" globals: - if (isMustKeepGlobalVariable(&GV)) - continue; - - Type *Ty = GV.getValueType(); - if (DL.getTypeAllocSize(Ty) < MaxOffset) { - if (TM && - TargetLoweringObjectFile::getKindForGlobal(&GV, *TM).isBSS()) - BSSGlobals[{AddressSpace, Section}].push_back(&GV); - else if (GV.isConstant()) - ConstGlobals[{AddressSpace, Section}].push_back(&GV); - else - Globals[{AddressSpace, Section}].push_back(&GV); - } - } - - for (auto &P : Globals) - if (P.second.size() > 1) - Changed |= doMerge(P.second, M, false, P.first.first); - - for (auto &P : BSSGlobals) - if (P.second.size() > 1) - Changed |= doMerge(P.second, M, false, P.first.first); - - if (EnableGlobalMergeOnConst) - for (auto &P : ConstGlobals) - if (P.second.size() > 1) - Changed |= doMerge(P.second, M, true, P.first.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, - bool MergeExternalByDefault) { - bool MergeExternal = (EnableGlobalMergeOnExternal == cl::BOU_UNSET) ? - MergeExternalByDefault : (EnableGlobalMergeOnExternal == cl::BOU_TRUE); - return new GlobalMerge(TM, Offset, OnlyOptimizeForSize, MergeExternal); -} |