| //===- GlobalOpt.cpp - Optimize Global Variables --------------------------===// |
| // |
| // 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 transforms simple global variables that never have their address |
| // taken. If obviously true, it marks read/write globals as constant, deletes |
| // variables only stored to, etc. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/Transforms/IPO/GlobalOpt.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/ADT/Twine.h" |
| #include "llvm/ADT/iterator_range.h" |
| #include "llvm/Analysis/BlockFrequencyInfo.h" |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Analysis/MemoryBuiltins.h" |
| #include "llvm/Analysis/TargetLibraryInfo.h" |
| #include "llvm/Analysis/TargetTransformInfo.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include "llvm/BinaryFormat/Dwarf.h" |
| #include "llvm/IR/Attributes.h" |
| #include "llvm/IR/BasicBlock.h" |
| #include "llvm/IR/CallSite.h" |
| #include "llvm/IR/CallingConv.h" |
| #include "llvm/IR/Constant.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/DebugInfoMetadata.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/Dominators.h" |
| #include "llvm/IR/Function.h" |
| #include "llvm/IR/GetElementPtrTypeIterator.h" |
| #include "llvm/IR/GlobalAlias.h" |
| #include "llvm/IR/GlobalValue.h" |
| #include "llvm/IR/GlobalVariable.h" |
| #include "llvm/IR/InstrTypes.h" |
| #include "llvm/IR/Instruction.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/IR/Operator.h" |
| #include "llvm/IR/Type.h" |
| #include "llvm/IR/Use.h" |
| #include "llvm/IR/User.h" |
| #include "llvm/IR/Value.h" |
| #include "llvm/IR/ValueHandle.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/AtomicOrdering.h" |
| #include "llvm/Support/Casting.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Transforms/IPO.h" |
| #include "llvm/Transforms/Utils/CtorUtils.h" |
| #include "llvm/Transforms/Utils/Evaluator.h" |
| #include "llvm/Transforms/Utils/GlobalStatus.h" |
| #include <cassert> |
| #include <cstdint> |
| #include <utility> |
| #include <vector> |
| |
| using namespace llvm; |
| |
| #define DEBUG_TYPE "globalopt" |
| |
| STATISTIC(NumMarked , "Number of globals marked constant"); |
| STATISTIC(NumUnnamed , "Number of globals marked unnamed_addr"); |
| STATISTIC(NumSRA , "Number of aggregate globals broken into scalars"); |
| STATISTIC(NumHeapSRA , "Number of heap objects SRA'd"); |
| STATISTIC(NumSubstitute,"Number of globals with initializers stored into them"); |
| STATISTIC(NumDeleted , "Number of globals deleted"); |
| STATISTIC(NumGlobUses , "Number of global uses devirtualized"); |
| STATISTIC(NumLocalized , "Number of globals localized"); |
| STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans"); |
| STATISTIC(NumFastCallFns , "Number of functions converted to fastcc"); |
| STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated"); |
| STATISTIC(NumNestRemoved , "Number of nest attributes removed"); |
| STATISTIC(NumAliasesResolved, "Number of global aliases resolved"); |
| STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated"); |
| STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed"); |
| STATISTIC(NumInternalFunc, "Number of internal functions"); |
| STATISTIC(NumColdCC, "Number of functions marked coldcc"); |
| |
| static cl::opt<bool> |
| EnableColdCCStressTest("enable-coldcc-stress-test", |
| cl::desc("Enable stress test of coldcc by adding " |
| "calling conv to all internal functions."), |
| cl::init(false), cl::Hidden); |
| |
| static cl::opt<int> ColdCCRelFreq( |
| "coldcc-rel-freq", cl::Hidden, cl::init(2), cl::ZeroOrMore, |
| cl::desc( |
| "Maximum block frequency, expressed as a percentage of caller's " |
| "entry frequency, for a call site to be considered cold for enabling" |
| "coldcc")); |
| |
| /// Is this global variable possibly used by a leak checker as a root? If so, |
| /// we might not really want to eliminate the stores to it. |
| static bool isLeakCheckerRoot(GlobalVariable *GV) { |
| // A global variable is a root if it is a pointer, or could plausibly contain |
| // a pointer. There are two challenges; one is that we could have a struct |
| // the has an inner member which is a pointer. We recurse through the type to |
| // detect these (up to a point). The other is that we may actually be a union |
| // of a pointer and another type, and so our LLVM type is an integer which |
| // gets converted into a pointer, or our type is an [i8 x #] with a pointer |
| // potentially contained here. |
| |
| if (GV->hasPrivateLinkage()) |
| return false; |
| |
| SmallVector<Type *, 4> Types; |
| Types.push_back(GV->getValueType()); |
| |
| unsigned Limit = 20; |
| do { |
| Type *Ty = Types.pop_back_val(); |
| switch (Ty->getTypeID()) { |
| default: break; |
| case Type::PointerTyID: return true; |
| case Type::ArrayTyID: |
| case Type::VectorTyID: { |
| SequentialType *STy = cast<SequentialType>(Ty); |
| Types.push_back(STy->getElementType()); |
| break; |
| } |
| case Type::StructTyID: { |
| StructType *STy = cast<StructType>(Ty); |
| if (STy->isOpaque()) return true; |
| for (StructType::element_iterator I = STy->element_begin(), |
| E = STy->element_end(); I != E; ++I) { |
| Type *InnerTy = *I; |
| if (isa<PointerType>(InnerTy)) return true; |
| if (isa<CompositeType>(InnerTy)) |
| Types.push_back(InnerTy); |
| } |
| break; |
| } |
| } |
| if (--Limit == 0) return true; |
| } while (!Types.empty()); |
| return false; |
| } |
| |
| /// Given a value that is stored to a global but never read, determine whether |
| /// it's safe to remove the store and the chain of computation that feeds the |
| /// store. |
| static bool IsSafeComputationToRemove( |
| Value *V, function_ref<TargetLibraryInfo &(Function &)> GetTLI) { |
| do { |
| if (isa<Constant>(V)) |
| return true; |
| if (!V->hasOneUse()) |
| return false; |
| if (isa<LoadInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V) || |
| isa<GlobalValue>(V)) |
| return false; |
| if (isAllocationFn(V, GetTLI)) |
| return true; |
| |
| Instruction *I = cast<Instruction>(V); |
| if (I->mayHaveSideEffects()) |
| return false; |
| if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) { |
| if (!GEP->hasAllConstantIndices()) |
| return false; |
| } else if (I->getNumOperands() != 1) { |
| return false; |
| } |
| |
| V = I->getOperand(0); |
| } while (true); |
| } |
| |
| /// This GV is a pointer root. Loop over all users of the global and clean up |
| /// any that obviously don't assign the global a value that isn't dynamically |
| /// allocated. |
| static bool |
| CleanupPointerRootUsers(GlobalVariable *GV, |
| function_ref<TargetLibraryInfo &(Function &)> GetTLI) { |
| // A brief explanation of leak checkers. The goal is to find bugs where |
| // pointers are forgotten, causing an accumulating growth in memory |
| // usage over time. The common strategy for leak checkers is to whitelist the |
| // memory pointed to by globals at exit. This is popular because it also |
| // solves another problem where the main thread of a C++ program may shut down |
| // before other threads that are still expecting to use those globals. To |
| // handle that case, we expect the program may create a singleton and never |
| // destroy it. |
| |
| bool Changed = false; |
| |
| // If Dead[n].first is the only use of a malloc result, we can delete its |
| // chain of computation and the store to the global in Dead[n].second. |
| SmallVector<std::pair<Instruction *, Instruction *>, 32> Dead; |
| |
| // Constants can't be pointers to dynamically allocated memory. |
| for (Value::user_iterator UI = GV->user_begin(), E = GV->user_end(); |
| UI != E;) { |
| User *U = *UI++; |
| if (StoreInst *SI = dyn_cast<StoreInst>(U)) { |
| Value *V = SI->getValueOperand(); |
| if (isa<Constant>(V)) { |
| Changed = true; |
| SI->eraseFromParent(); |
| } else if (Instruction *I = dyn_cast<Instruction>(V)) { |
| if (I->hasOneUse()) |
| Dead.push_back(std::make_pair(I, SI)); |
| } |
| } else if (MemSetInst *MSI = dyn_cast<MemSetInst>(U)) { |
| if (isa<Constant>(MSI->getValue())) { |
| Changed = true; |
| MSI->eraseFromParent(); |
| } else if (Instruction *I = dyn_cast<Instruction>(MSI->getValue())) { |
| if (I->hasOneUse()) |
| Dead.push_back(std::make_pair(I, MSI)); |
| } |
| } else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U)) { |
| GlobalVariable *MemSrc = dyn_cast<GlobalVariable>(MTI->getSource()); |
| if (MemSrc && MemSrc->isConstant()) { |
| Changed = true; |
| MTI->eraseFromParent(); |
| } else if (Instruction *I = dyn_cast<Instruction>(MemSrc)) { |
| if (I->hasOneUse()) |
| Dead.push_back(std::make_pair(I, MTI)); |
| } |
| } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { |
| if (CE->use_empty()) { |
| CE->destroyConstant(); |
| Changed = true; |
| } |
| } else if (Constant *C = dyn_cast<Constant>(U)) { |
| if (isSafeToDestroyConstant(C)) { |
| C->destroyConstant(); |
| // This could have invalidated UI, start over from scratch. |
| Dead.clear(); |
| CleanupPointerRootUsers(GV, GetTLI); |
| return true; |
| } |
| } |
| } |
| |
| for (int i = 0, e = Dead.size(); i != e; ++i) { |
| if (IsSafeComputationToRemove(Dead[i].first, GetTLI)) { |
| Dead[i].second->eraseFromParent(); |
| Instruction *I = Dead[i].first; |
| do { |
| if (isAllocationFn(I, GetTLI)) |
| break; |
| Instruction *J = dyn_cast<Instruction>(I->getOperand(0)); |
| if (!J) |
| break; |
| I->eraseFromParent(); |
| I = J; |
| } while (true); |
| I->eraseFromParent(); |
| } |
| } |
| |
| return Changed; |
| } |
| |
| /// We just marked GV constant. Loop over all users of the global, cleaning up |
| /// the obvious ones. This is largely just a quick scan over the use list to |
| /// clean up the easy and obvious cruft. This returns true if it made a change. |
| static bool CleanupConstantGlobalUsers( |
| Value *V, Constant *Init, const DataLayout &DL, |
| function_ref<TargetLibraryInfo &(Function &)> GetTLI) { |
| bool Changed = false; |
| // Note that we need to use a weak value handle for the worklist items. When |
| // we delete a constant array, we may also be holding pointer to one of its |
| // elements (or an element of one of its elements if we're dealing with an |
| // array of arrays) in the worklist. |
| SmallVector<WeakTrackingVH, 8> WorkList(V->user_begin(), V->user_end()); |
| while (!WorkList.empty()) { |
| Value *UV = WorkList.pop_back_val(); |
| if (!UV) |
| continue; |
| |
| User *U = cast<User>(UV); |
| |
| if (LoadInst *LI = dyn_cast<LoadInst>(U)) { |
| if (Init) { |
| // Replace the load with the initializer. |
| LI->replaceAllUsesWith(Init); |
| LI->eraseFromParent(); |
| Changed = true; |
| } |
| } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { |
| // Store must be unreachable or storing Init into the global. |
| SI->eraseFromParent(); |
| Changed = true; |
| } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { |
| if (CE->getOpcode() == Instruction::GetElementPtr) { |
| Constant *SubInit = nullptr; |
| if (Init) |
| SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); |
| Changed |= CleanupConstantGlobalUsers(CE, SubInit, DL, GetTLI); |
| } else if ((CE->getOpcode() == Instruction::BitCast && |
| CE->getType()->isPointerTy()) || |
| CE->getOpcode() == Instruction::AddrSpaceCast) { |
| // Pointer cast, delete any stores and memsets to the global. |
| Changed |= CleanupConstantGlobalUsers(CE, nullptr, DL, GetTLI); |
| } |
| |
| if (CE->use_empty()) { |
| CE->destroyConstant(); |
| Changed = true; |
| } |
| } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { |
| // Do not transform "gepinst (gep constexpr (GV))" here, because forming |
| // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold |
| // and will invalidate our notion of what Init is. |
| Constant *SubInit = nullptr; |
| if (!isa<ConstantExpr>(GEP->getOperand(0))) { |
| ConstantExpr *CE = dyn_cast_or_null<ConstantExpr>( |
| ConstantFoldInstruction(GEP, DL, &GetTLI(*GEP->getFunction()))); |
| if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr) |
| SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); |
| |
| // If the initializer is an all-null value and we have an inbounds GEP, |
| // we already know what the result of any load from that GEP is. |
| // TODO: Handle splats. |
| if (Init && isa<ConstantAggregateZero>(Init) && GEP->isInBounds()) |
| SubInit = Constant::getNullValue(GEP->getResultElementType()); |
| } |
| Changed |= CleanupConstantGlobalUsers(GEP, SubInit, DL, GetTLI); |
| |
| if (GEP->use_empty()) { |
| GEP->eraseFromParent(); |
| Changed = true; |
| } |
| } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv |
| if (MI->getRawDest() == V) { |
| MI->eraseFromParent(); |
| Changed = true; |
| } |
| |
| } else if (Constant *C = dyn_cast<Constant>(U)) { |
| // If we have a chain of dead constantexprs or other things dangling from |
| // us, and if they are all dead, nuke them without remorse. |
| if (isSafeToDestroyConstant(C)) { |
| C->destroyConstant(); |
| CleanupConstantGlobalUsers(V, Init, DL, GetTLI); |
| return true; |
| } |
| } |
| } |
| return Changed; |
| } |
| |
| static bool isSafeSROAElementUse(Value *V); |
| |
| /// Return true if the specified GEP is a safe user of a derived |
| /// expression from a global that we want to SROA. |
| static bool isSafeSROAGEP(User *U) { |
| // Check to see if this ConstantExpr GEP is SRA'able. In particular, we |
| // don't like < 3 operand CE's, and we don't like non-constant integer |
| // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some |
| // value of C. |
| if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) || |
| !cast<Constant>(U->getOperand(1))->isNullValue()) |
| return false; |
| |
| gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U); |
| ++GEPI; // Skip over the pointer index. |
| |
| // For all other level we require that the indices are constant and inrange. |
| // In particular, consider: A[0][i]. We cannot know that the user isn't doing |
| // invalid things like allowing i to index an out-of-range subscript that |
| // accesses A[1]. This can also happen between different members of a struct |
| // in llvm IR. |
| for (; GEPI != E; ++GEPI) { |
| if (GEPI.isStruct()) |
| continue; |
| |
| ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand()); |
| if (!IdxVal || (GEPI.isBoundedSequential() && |
| IdxVal->getZExtValue() >= GEPI.getSequentialNumElements())) |
| return false; |
| } |
| |
| return llvm::all_of(U->users(), |
| [](User *UU) { return isSafeSROAElementUse(UU); }); |
| } |
| |
| /// Return true if the specified instruction is a safe user of a derived |
| /// expression from a global that we want to SROA. |
| static bool isSafeSROAElementUse(Value *V) { |
| // We might have a dead and dangling constant hanging off of here. |
| if (Constant *C = dyn_cast<Constant>(V)) |
| return isSafeToDestroyConstant(C); |
| |
| Instruction *I = dyn_cast<Instruction>(V); |
| if (!I) return false; |
| |
| // Loads are ok. |
| if (isa<LoadInst>(I)) return true; |
| |
| // Stores *to* the pointer are ok. |
| if (StoreInst *SI = dyn_cast<StoreInst>(I)) |
| return SI->getOperand(0) != V; |
| |
| // Otherwise, it must be a GEP. Check it and its users are safe to SRA. |
| return isa<GetElementPtrInst>(I) && isSafeSROAGEP(I); |
| } |
| |
| /// Look at all uses of the global and decide whether it is safe for us to |
| /// perform this transformation. |
| static bool GlobalUsersSafeToSRA(GlobalValue *GV) { |
| for (User *U : GV->users()) { |
| // The user of the global must be a GEP Inst or a ConstantExpr GEP. |
| if (!isa<GetElementPtrInst>(U) && |
| (!isa<ConstantExpr>(U) || |
| cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr)) |
| return false; |
| |
| // Check the gep and it's users are safe to SRA |
| if (!isSafeSROAGEP(U)) |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /// Copy over the debug info for a variable to its SRA replacements. |
| static void transferSRADebugInfo(GlobalVariable *GV, GlobalVariable *NGV, |
| uint64_t FragmentOffsetInBits, |
| uint64_t FragmentSizeInBits, |
| unsigned NumElements) { |
| SmallVector<DIGlobalVariableExpression *, 1> GVs; |
| GV->getDebugInfo(GVs); |
| for (auto *GVE : GVs) { |
| DIVariable *Var = GVE->getVariable(); |
| DIExpression *Expr = GVE->getExpression(); |
| if (NumElements > 1) { |
| if (auto E = DIExpression::createFragmentExpression( |
| Expr, FragmentOffsetInBits, FragmentSizeInBits)) |
| Expr = *E; |
| else |
| return; |
| } |
| auto *NGVE = DIGlobalVariableExpression::get(GVE->getContext(), Var, Expr); |
| NGV->addDebugInfo(NGVE); |
| } |
| } |
| |
| /// Perform scalar replacement of aggregates on the specified global variable. |
| /// This opens the door for other optimizations by exposing the behavior of the |
| /// program in a more fine-grained way. We have determined that this |
| /// transformation is safe already. We return the first global variable we |
| /// insert so that the caller can reprocess it. |
| static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &DL) { |
| // Make sure this global only has simple uses that we can SRA. |
| if (!GlobalUsersSafeToSRA(GV)) |
| return nullptr; |
| |
| assert(GV->hasLocalLinkage()); |
| Constant *Init = GV->getInitializer(); |
| Type *Ty = Init->getType(); |
| |
| std::vector<GlobalVariable *> NewGlobals; |
| Module::GlobalListType &Globals = GV->getParent()->getGlobalList(); |
| |
| // Get the alignment of the global, either explicit or target-specific. |
| unsigned StartAlignment = GV->getAlignment(); |
| if (StartAlignment == 0) |
| StartAlignment = DL.getABITypeAlignment(GV->getType()); |
| |
| if (StructType *STy = dyn_cast<StructType>(Ty)) { |
| unsigned NumElements = STy->getNumElements(); |
| NewGlobals.reserve(NumElements); |
| const StructLayout &Layout = *DL.getStructLayout(STy); |
| for (unsigned i = 0, e = NumElements; i != e; ++i) { |
| Constant *In = Init->getAggregateElement(i); |
| assert(In && "Couldn't get element of initializer?"); |
| GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false, |
| GlobalVariable::InternalLinkage, |
| In, GV->getName()+"."+Twine(i), |
| GV->getThreadLocalMode(), |
| GV->getType()->getAddressSpace()); |
| NGV->setExternallyInitialized(GV->isExternallyInitialized()); |
| NGV->copyAttributesFrom(GV); |
| Globals.push_back(NGV); |
| NewGlobals.push_back(NGV); |
| |
| // Calculate the known alignment of the field. If the original aggregate |
| // had 256 byte alignment for example, something might depend on that: |
| // propagate info to each field. |
| uint64_t FieldOffset = Layout.getElementOffset(i); |
| Align NewAlign(MinAlign(StartAlignment, FieldOffset)); |
| if (NewAlign > Align(DL.getABITypeAlignment(STy->getElementType(i)))) |
| NGV->setAlignment(NewAlign); |
| |
| // Copy over the debug info for the variable. |
| uint64_t Size = DL.getTypeAllocSizeInBits(NGV->getValueType()); |
| uint64_t FragmentOffsetInBits = Layout.getElementOffsetInBits(i); |
| transferSRADebugInfo(GV, NGV, FragmentOffsetInBits, Size, NumElements); |
| } |
| } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) { |
| unsigned NumElements = STy->getNumElements(); |
| if (NumElements > 16 && GV->hasNUsesOrMore(16)) |
| return nullptr; // It's not worth it. |
| NewGlobals.reserve(NumElements); |
| auto ElTy = STy->getElementType(); |
| uint64_t EltSize = DL.getTypeAllocSize(ElTy); |
| Align EltAlign(DL.getABITypeAlignment(ElTy)); |
| uint64_t FragmentSizeInBits = DL.getTypeAllocSizeInBits(ElTy); |
| for (unsigned i = 0, e = NumElements; i != e; ++i) { |
| Constant *In = Init->getAggregateElement(i); |
| assert(In && "Couldn't get element of initializer?"); |
| |
| GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false, |
| GlobalVariable::InternalLinkage, |
| In, GV->getName()+"."+Twine(i), |
| GV->getThreadLocalMode(), |
| GV->getType()->getAddressSpace()); |
| NGV->setExternallyInitialized(GV->isExternallyInitialized()); |
| NGV->copyAttributesFrom(GV); |
| Globals.push_back(NGV); |
| NewGlobals.push_back(NGV); |
| |
| // Calculate the known alignment of the field. If the original aggregate |
| // had 256 byte alignment for example, something might depend on that: |
| // propagate info to each field. |
| Align NewAlign(MinAlign(StartAlignment, EltSize * i)); |
| if (NewAlign > EltAlign) |
| NGV->setAlignment(NewAlign); |
| transferSRADebugInfo(GV, NGV, FragmentSizeInBits * i, FragmentSizeInBits, |
| NumElements); |
| } |
| } |
| |
| if (NewGlobals.empty()) |
| return nullptr; |
| |
| LLVM_DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV << "\n"); |
| |
| Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext())); |
| |
| // Loop over all of the uses of the global, replacing the constantexpr geps, |
| // with smaller constantexpr geps or direct references. |
| while (!GV->use_empty()) { |
| User *GEP = GV->user_back(); |
| assert(((isa<ConstantExpr>(GEP) && |
| cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)|| |
| isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!"); |
| |
| // Ignore the 1th operand, which has to be zero or else the program is quite |
| // broken (undefined). Get the 2nd operand, which is the structure or array |
| // index. |
| unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); |
| if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access. |
| |
| Value *NewPtr = NewGlobals[Val]; |
| Type *NewTy = NewGlobals[Val]->getValueType(); |
| |
| // Form a shorter GEP if needed. |
| if (GEP->getNumOperands() > 3) { |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) { |
| SmallVector<Constant*, 8> Idxs; |
| Idxs.push_back(NullInt); |
| for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i) |
| Idxs.push_back(CE->getOperand(i)); |
| NewPtr = |
| ConstantExpr::getGetElementPtr(NewTy, cast<Constant>(NewPtr), Idxs); |
| } else { |
| GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP); |
| SmallVector<Value*, 8> Idxs; |
| Idxs.push_back(NullInt); |
| for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i) |
| Idxs.push_back(GEPI->getOperand(i)); |
| NewPtr = GetElementPtrInst::Create( |
| NewTy, NewPtr, Idxs, GEPI->getName() + "." + Twine(Val), GEPI); |
| } |
| } |
| GEP->replaceAllUsesWith(NewPtr); |
| |
| if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP)) |
| GEPI->eraseFromParent(); |
| else |
| cast<ConstantExpr>(GEP)->destroyConstant(); |
| } |
| |
| // Delete the old global, now that it is dead. |
| Globals.erase(GV); |
| ++NumSRA; |
| |
| // Loop over the new globals array deleting any globals that are obviously |
| // dead. This can arise due to scalarization of a structure or an array that |
| // has elements that are dead. |
| unsigned FirstGlobal = 0; |
| for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i) |
| if (NewGlobals[i]->use_empty()) { |
| Globals.erase(NewGlobals[i]); |
| if (FirstGlobal == i) ++FirstGlobal; |
| } |
| |
| return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : nullptr; |
| } |
| |
| /// Return true if all users of the specified value will trap if the value is |
| /// dynamically null. PHIs keeps track of any phi nodes we've seen to avoid |
| /// reprocessing them. |
| static bool AllUsesOfValueWillTrapIfNull(const Value *V, |
| SmallPtrSetImpl<const PHINode*> &PHIs) { |
| for (const User *U : V->users()) { |
| if (const Instruction *I = dyn_cast<Instruction>(U)) { |
| // If null pointer is considered valid, then all uses are non-trapping. |
| // Non address-space 0 globals have already been pruned by the caller. |
| if (NullPointerIsDefined(I->getFunction())) |
| return false; |
| } |
| if (isa<LoadInst>(U)) { |
| // Will trap. |
| } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) { |
| if (SI->getOperand(0) == V) { |
| //cerr << "NONTRAPPING USE: " << *U; |
| return false; // Storing the value. |
| } |
| } else if (const CallInst *CI = dyn_cast<CallInst>(U)) { |
| if (CI->getCalledValue() != V) { |
| //cerr << "NONTRAPPING USE: " << *U; |
| return false; // Not calling the ptr |
| } |
| } else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) { |
| if (II->getCalledValue() != V) { |
| //cerr << "NONTRAPPING USE: " << *U; |
| return false; // Not calling the ptr |
| } |
| } else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) { |
| if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false; |
| } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) { |
| if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false; |
| } else if (const PHINode *PN = dyn_cast<PHINode>(U)) { |
| // If we've already seen this phi node, ignore it, it has already been |
| // checked. |
| if (PHIs.insert(PN).second && !AllUsesOfValueWillTrapIfNull(PN, PHIs)) |
| return false; |
| } else if (isa<ICmpInst>(U) && |
| isa<ConstantPointerNull>(U->getOperand(1))) { |
| // Ignore icmp X, null |
| } else { |
| //cerr << "NONTRAPPING USE: " << *U; |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| /// Return true if all uses of any loads from GV will trap if the loaded value |
| /// is null. Note that this also permits comparisons of the loaded value |
| /// against null, as a special case. |
| static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) { |
| for (const User *U : GV->users()) |
| if (const LoadInst *LI = dyn_cast<LoadInst>(U)) { |
| SmallPtrSet<const PHINode*, 8> PHIs; |
| if (!AllUsesOfValueWillTrapIfNull(LI, PHIs)) |
| return false; |
| } else if (isa<StoreInst>(U)) { |
| // Ignore stores to the global. |
| } else { |
| // We don't know or understand this user, bail out. |
| //cerr << "UNKNOWN USER OF GLOBAL!: " << *U; |
| return false; |
| } |
| return true; |
| } |
| |
| static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) { |
| bool Changed = false; |
| for (auto UI = V->user_begin(), E = V->user_end(); UI != E; ) { |
| Instruction *I = cast<Instruction>(*UI++); |
| // Uses are non-trapping if null pointer is considered valid. |
| // Non address-space 0 globals are already pruned by the caller. |
| if (NullPointerIsDefined(I->getFunction())) |
| return false; |
| if (LoadInst *LI = dyn_cast<LoadInst>(I)) { |
| LI->setOperand(0, NewV); |
| Changed = true; |
| } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { |
| if (SI->getOperand(1) == V) { |
| SI->setOperand(1, NewV); |
| Changed = true; |
| } |
| } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) { |
| CallSite CS(I); |
| if (CS.getCalledValue() == V) { |
| // Calling through the pointer! Turn into a direct call, but be careful |
| // that the pointer is not also being passed as an argument. |
| CS.setCalledFunction(NewV); |
| Changed = true; |
| bool PassedAsArg = false; |
| for (unsigned i = 0, e = CS.arg_size(); i != e; ++i) |
| if (CS.getArgument(i) == V) { |
| PassedAsArg = true; |
| CS.setArgument(i, NewV); |
| } |
| |
| if (PassedAsArg) { |
| // Being passed as an argument also. Be careful to not invalidate UI! |
| UI = V->user_begin(); |
| } |
| } |
| } else if (CastInst *CI = dyn_cast<CastInst>(I)) { |
| Changed |= OptimizeAwayTrappingUsesOfValue(CI, |
| ConstantExpr::getCast(CI->getOpcode(), |
| NewV, CI->getType())); |
| if (CI->use_empty()) { |
| Changed = true; |
| CI->eraseFromParent(); |
| } |
| } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { |
| // Should handle GEP here. |
| SmallVector<Constant*, 8> Idxs; |
| Idxs.reserve(GEPI->getNumOperands()-1); |
| for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end(); |
| i != e; ++i) |
| if (Constant *C = dyn_cast<Constant>(*i)) |
| Idxs.push_back(C); |
| else |
| break; |
| if (Idxs.size() == GEPI->getNumOperands()-1) |
| Changed |= OptimizeAwayTrappingUsesOfValue( |
| GEPI, ConstantExpr::getGetElementPtr(GEPI->getSourceElementType(), |
| NewV, Idxs)); |
| if (GEPI->use_empty()) { |
| Changed = true; |
| GEPI->eraseFromParent(); |
| } |
| } |
| } |
| |
| return Changed; |
| } |
| |
| /// The specified global has only one non-null value stored into it. If there |
| /// are uses of the loaded value that would trap if the loaded value is |
| /// dynamically null, then we know that they cannot be reachable with a null |
| /// optimize away the load. |
| static bool OptimizeAwayTrappingUsesOfLoads( |
| GlobalVariable *GV, Constant *LV, const DataLayout &DL, |
| function_ref<TargetLibraryInfo &(Function &)> GetTLI) { |
| bool Changed = false; |
| |
| // Keep track of whether we are able to remove all the uses of the global |
| // other than the store that defines it. |
| bool AllNonStoreUsesGone = true; |
| |
| // Replace all uses of loads with uses of uses of the stored value. |
| for (Value::user_iterator GUI = GV->user_begin(), E = GV->user_end(); GUI != E;){ |
| User *GlobalUser = *GUI++; |
| if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) { |
| Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); |
| // If we were able to delete all uses of the loads |
| if (LI->use_empty()) { |
| LI->eraseFromParent(); |
| Changed = true; |
| } else { |
| AllNonStoreUsesGone = false; |
| } |
| } else if (isa<StoreInst>(GlobalUser)) { |
| // Ignore the store that stores "LV" to the global. |
| assert(GlobalUser->getOperand(1) == GV && |
| "Must be storing *to* the global"); |
| } else { |
| AllNonStoreUsesGone = false; |
| |
| // If we get here we could have other crazy uses that are transitively |
| // loaded. |
| assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) || |
| isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser) || |
| isa<BitCastInst>(GlobalUser) || |
| isa<GetElementPtrInst>(GlobalUser)) && |
| "Only expect load and stores!"); |
| } |
| } |
| |
| if (Changed) { |
| LLVM_DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV |
| << "\n"); |
| ++NumGlobUses; |
| } |
| |
| // If we nuked all of the loads, then none of the stores are needed either, |
| // nor is the global. |
| if (AllNonStoreUsesGone) { |
| if (isLeakCheckerRoot(GV)) { |
| Changed |= CleanupPointerRootUsers(GV, GetTLI); |
| } else { |
| Changed = true; |
| CleanupConstantGlobalUsers(GV, nullptr, DL, GetTLI); |
| } |
| if (GV->use_empty()) { |
| LLVM_DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n"); |
| Changed = true; |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| } |
| } |
| return Changed; |
| } |
| |
| /// Walk the use list of V, constant folding all of the instructions that are |
| /// foldable. |
| static void ConstantPropUsersOf(Value *V, const DataLayout &DL, |
| TargetLibraryInfo *TLI) { |
| for (Value::user_iterator UI = V->user_begin(), E = V->user_end(); UI != E; ) |
| if (Instruction *I = dyn_cast<Instruction>(*UI++)) |
| if (Constant *NewC = ConstantFoldInstruction(I, DL, TLI)) { |
| I->replaceAllUsesWith(NewC); |
| |
| // Advance UI to the next non-I use to avoid invalidating it! |
| // Instructions could multiply use V. |
| while (UI != E && *UI == I) |
| ++UI; |
| if (isInstructionTriviallyDead(I, TLI)) |
| I->eraseFromParent(); |
| } |
| } |
| |
| /// This function takes the specified global variable, and transforms the |
| /// program as if it always contained the result of the specified malloc. |
| /// Because it is always the result of the specified malloc, there is no reason |
| /// to actually DO the malloc. Instead, turn the malloc into a global, and any |
| /// loads of GV as uses of the new global. |
| static GlobalVariable * |
| OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, CallInst *CI, Type *AllocTy, |
| ConstantInt *NElements, const DataLayout &DL, |
| TargetLibraryInfo *TLI) { |
| LLVM_DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI |
| << '\n'); |
| |
| Type *GlobalType; |
| if (NElements->getZExtValue() == 1) |
| GlobalType = AllocTy; |
| else |
| // If we have an array allocation, the global variable is of an array. |
| GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue()); |
| |
| // Create the new global variable. The contents of the malloc'd memory is |
| // undefined, so initialize with an undef value. |
| GlobalVariable *NewGV = new GlobalVariable( |
| *GV->getParent(), GlobalType, false, GlobalValue::InternalLinkage, |
| UndefValue::get(GlobalType), GV->getName() + ".body", nullptr, |
| GV->getThreadLocalMode()); |
| |
| // If there are bitcast users of the malloc (which is typical, usually we have |
| // a malloc + bitcast) then replace them with uses of the new global. Update |
| // other users to use the global as well. |
| BitCastInst *TheBC = nullptr; |
| while (!CI->use_empty()) { |
| Instruction *User = cast<Instruction>(CI->user_back()); |
| if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { |
| if (BCI->getType() == NewGV->getType()) { |
| BCI->replaceAllUsesWith(NewGV); |
| BCI->eraseFromParent(); |
| } else { |
| BCI->setOperand(0, NewGV); |
| } |
| } else { |
| if (!TheBC) |
| TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI); |
| User->replaceUsesOfWith(CI, TheBC); |
| } |
| } |
| |
| Constant *RepValue = NewGV; |
| if (NewGV->getType() != GV->getValueType()) |
| RepValue = ConstantExpr::getBitCast(RepValue, GV->getValueType()); |
| |
| // If there is a comparison against null, we will insert a global bool to |
| // keep track of whether the global was initialized yet or not. |
| GlobalVariable *InitBool = |
| new GlobalVariable(Type::getInt1Ty(GV->getContext()), false, |
| GlobalValue::InternalLinkage, |
| ConstantInt::getFalse(GV->getContext()), |
| GV->getName()+".init", GV->getThreadLocalMode()); |
| bool InitBoolUsed = false; |
| |
| // Loop over all uses of GV, processing them in turn. |
| while (!GV->use_empty()) { |
| if (StoreInst *SI = dyn_cast<StoreInst>(GV->user_back())) { |
| // The global is initialized when the store to it occurs. |
| new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, |
| None, SI->getOrdering(), SI->getSyncScopeID(), SI); |
| SI->eraseFromParent(); |
| continue; |
| } |
| |
| LoadInst *LI = cast<LoadInst>(GV->user_back()); |
| while (!LI->use_empty()) { |
| Use &LoadUse = *LI->use_begin(); |
| ICmpInst *ICI = dyn_cast<ICmpInst>(LoadUse.getUser()); |
| if (!ICI) { |
| LoadUse = RepValue; |
| continue; |
| } |
| |
| // Replace the cmp X, 0 with a use of the bool value. |
| // Sink the load to where the compare was, if atomic rules allow us to. |
| Value *LV = new LoadInst(InitBool->getValueType(), InitBool, |
| InitBool->getName() + ".val", false, None, |
| LI->getOrdering(), LI->getSyncScopeID(), |
| LI->isUnordered() ? (Instruction *)ICI : LI); |
| InitBoolUsed = true; |
| switch (ICI->getPredicate()) { |
| default: llvm_unreachable("Unknown ICmp Predicate!"); |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_SLT: // X < null -> always false |
| LV = ConstantInt::getFalse(GV->getContext()); |
| break; |
| case ICmpInst::ICMP_ULE: |
| case ICmpInst::ICMP_SLE: |
| case ICmpInst::ICMP_EQ: |
| LV = BinaryOperator::CreateNot(LV, "notinit", ICI); |
| break; |
| case ICmpInst::ICMP_NE: |
| case ICmpInst::ICMP_UGE: |
| case ICmpInst::ICMP_SGE: |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGT: |
| break; // no change. |
| } |
| ICI->replaceAllUsesWith(LV); |
| ICI->eraseFromParent(); |
| } |
| LI->eraseFromParent(); |
| } |
| |
| // If the initialization boolean was used, insert it, otherwise delete it. |
| if (!InitBoolUsed) { |
| while (!InitBool->use_empty()) // Delete initializations |
| cast<StoreInst>(InitBool->user_back())->eraseFromParent(); |
| delete InitBool; |
| } else |
| GV->getParent()->getGlobalList().insert(GV->getIterator(), InitBool); |
| |
| // Now the GV is dead, nuke it and the malloc.. |
| GV->eraseFromParent(); |
| CI->eraseFromParent(); |
| |
| // To further other optimizations, loop over all users of NewGV and try to |
| // constant prop them. This will promote GEP instructions with constant |
| // indices into GEP constant-exprs, which will allow global-opt to hack on it. |
| ConstantPropUsersOf(NewGV, DL, TLI); |
| if (RepValue != NewGV) |
| ConstantPropUsersOf(RepValue, DL, TLI); |
| |
| return NewGV; |
| } |
| |
| /// Scan the use-list of V checking to make sure that there are no complex uses |
| /// of V. We permit simple things like dereferencing the pointer, but not |
| /// storing through the address, unless it is to the specified global. |
| static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V, |
| const GlobalVariable *GV, |
| SmallPtrSetImpl<const PHINode*> &PHIs) { |
| for (const User *U : V->users()) { |
| const Instruction *Inst = cast<Instruction>(U); |
| |
| if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) { |
| continue; // Fine, ignore. |
| } |
| |
| if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { |
| if (SI->getOperand(0) == V && SI->getOperand(1) != GV) |
| return false; // Storing the pointer itself... bad. |
| continue; // Otherwise, storing through it, or storing into GV... fine. |
| } |
| |
| // Must index into the array and into the struct. |
| if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) { |
| if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs)) |
| return false; |
| continue; |
| } |
| |
| if (const PHINode *PN = dyn_cast<PHINode>(Inst)) { |
| // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI |
| // cycles. |
| if (PHIs.insert(PN).second) |
| if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs)) |
| return false; |
| continue; |
| } |
| |
| if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) { |
| if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs)) |
| return false; |
| continue; |
| } |
| |
| return false; |
| } |
| return true; |
| } |
| |
| /// The Alloc pointer is stored into GV somewhere. Transform all uses of the |
| /// allocation into loads from the global and uses of the resultant pointer. |
| /// Further, delete the store into GV. This assumes that these value pass the |
| /// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate. |
| static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc, |
| GlobalVariable *GV) { |
| while (!Alloc->use_empty()) { |
| Instruction *U = cast<Instruction>(*Alloc->user_begin()); |
| Instruction *InsertPt = U; |
| if (StoreInst *SI = dyn_cast<StoreInst>(U)) { |
| // If this is the store of the allocation into the global, remove it. |
| if (SI->getOperand(1) == GV) { |
| SI->eraseFromParent(); |
| continue; |
| } |
| } else if (PHINode *PN = dyn_cast<PHINode>(U)) { |
| // Insert the load in the corresponding predecessor, not right before the |
| // PHI. |
| InsertPt = PN->getIncomingBlock(*Alloc->use_begin())->getTerminator(); |
| } else if (isa<BitCastInst>(U)) { |
| // Must be bitcast between the malloc and store to initialize the global. |
| ReplaceUsesOfMallocWithGlobal(U, GV); |
| U->eraseFromParent(); |
| continue; |
| } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) { |
| // If this is a "GEP bitcast" and the user is a store to the global, then |
| // just process it as a bitcast. |
| if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse()) |
| if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->user_back())) |
| if (SI->getOperand(1) == GV) { |
| // Must be bitcast GEP between the malloc and store to initialize |
| // the global. |
| ReplaceUsesOfMallocWithGlobal(GEPI, GV); |
| GEPI->eraseFromParent(); |
| continue; |
| } |
| } |
| |
| // Insert a load from the global, and use it instead of the malloc. |
| Value *NL = |
| new LoadInst(GV->getValueType(), GV, GV->getName() + ".val", InsertPt); |
| U->replaceUsesOfWith(Alloc, NL); |
| } |
| } |
| |
| /// Verify that all uses of V (a load, or a phi of a load) are simple enough to |
| /// perform heap SRA on. This permits GEP's that index through the array and |
| /// struct field, icmps of null, and PHIs. |
| static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V, |
| SmallPtrSetImpl<const PHINode*> &LoadUsingPHIs, |
| SmallPtrSetImpl<const PHINode*> &LoadUsingPHIsPerLoad) { |
| // We permit two users of the load: setcc comparing against the null |
| // pointer, and a getelementptr of a specific form. |
| for (const User *U : V->users()) { |
| const Instruction *UI = cast<Instruction>(U); |
| |
| // Comparison against null is ok. |
| if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UI)) { |
| if (!isa<ConstantPointerNull>(ICI->getOperand(1))) |
| return false; |
| continue; |
| } |
| |
| // getelementptr is also ok, but only a simple form. |
| if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(UI)) { |
| // Must index into the array and into the struct. |
| if (GEPI->getNumOperands() < 3) |
| return false; |
| |
| // Otherwise the GEP is ok. |
| continue; |
| } |
| |
| if (const PHINode *PN = dyn_cast<PHINode>(UI)) { |
| if (!LoadUsingPHIsPerLoad.insert(PN).second) |
| // This means some phi nodes are dependent on each other. |
| // Avoid infinite looping! |
| return false; |
| if (!LoadUsingPHIs.insert(PN).second) |
| // If we have already analyzed this PHI, then it is safe. |
| continue; |
| |
| // Make sure all uses of the PHI are simple enough to transform. |
| if (!LoadUsesSimpleEnoughForHeapSRA(PN, |
| LoadUsingPHIs, LoadUsingPHIsPerLoad)) |
| return false; |
| |
| continue; |
| } |
| |
| // Otherwise we don't know what this is, not ok. |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /// If all users of values loaded from GV are simple enough to perform HeapSRA, |
| /// return true. |
| static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV, |
| Instruction *StoredVal) { |
| SmallPtrSet<const PHINode*, 32> LoadUsingPHIs; |
| SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad; |
| for (const User *U : GV->users()) |
| if (const LoadInst *LI = dyn_cast<LoadInst>(U)) { |
| if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs, |
| LoadUsingPHIsPerLoad)) |
| return false; |
| LoadUsingPHIsPerLoad.clear(); |
| } |
| |
| // If we reach here, we know that all uses of the loads and transitive uses |
| // (through PHI nodes) are simple enough to transform. However, we don't know |
| // that all inputs the to the PHI nodes are in the same equivalence sets. |
| // Check to verify that all operands of the PHIs are either PHIS that can be |
| // transformed, loads from GV, or MI itself. |
| for (const PHINode *PN : LoadUsingPHIs) { |
| for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) { |
| Value *InVal = PN->getIncomingValue(op); |
| |
| // PHI of the stored value itself is ok. |
| if (InVal == StoredVal) continue; |
| |
| if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) { |
| // One of the PHIs in our set is (optimistically) ok. |
| if (LoadUsingPHIs.count(InPN)) |
| continue; |
| return false; |
| } |
| |
| // Load from GV is ok. |
| if (const LoadInst *LI = dyn_cast<LoadInst>(InVal)) |
| if (LI->getOperand(0) == GV) |
| continue; |
| |
| // UNDEF? NULL? |
| |
| // Anything else is rejected. |
| return false; |
| } |
| } |
| |
| return true; |
| } |
| |
| static Value *GetHeapSROAValue(Value *V, unsigned FieldNo, |
| DenseMap<Value *, std::vector<Value *>> &InsertedScalarizedValues, |
| std::vector<std::pair<PHINode *, unsigned>> &PHIsToRewrite) { |
| std::vector<Value *> &FieldVals = InsertedScalarizedValues[V]; |
| |
| if (FieldNo >= FieldVals.size()) |
| FieldVals.resize(FieldNo+1); |
| |
| // If we already have this value, just reuse the previously scalarized |
| // version. |
| if (Value *FieldVal = FieldVals[FieldNo]) |
| return FieldVal; |
| |
| // Depending on what instruction this is, we have several cases. |
| Value *Result; |
| if (LoadInst *LI = dyn_cast<LoadInst>(V)) { |
| // This is a scalarized version of the load from the global. Just create |
| // a new Load of the scalarized global. |
| Value *V = GetHeapSROAValue(LI->getOperand(0), FieldNo, |
| InsertedScalarizedValues, PHIsToRewrite); |
| Result = new LoadInst(V->getType()->getPointerElementType(), V, |
| LI->getName() + ".f" + Twine(FieldNo), LI); |
| } else { |
| PHINode *PN = cast<PHINode>(V); |
| // PN's type is pointer to struct. Make a new PHI of pointer to struct |
| // field. |
| |
| PointerType *PTy = cast<PointerType>(PN->getType()); |
| StructType *ST = cast<StructType>(PTy->getElementType()); |
| |
| unsigned AS = PTy->getAddressSpace(); |
| PHINode *NewPN = |
| PHINode::Create(PointerType::get(ST->getElementType(FieldNo), AS), |
| PN->getNumIncomingValues(), |
| PN->getName()+".f"+Twine(FieldNo), PN); |
| Result = NewPN; |
| PHIsToRewrite.push_back(std::make_pair(PN, FieldNo)); |
| } |
| |
| return FieldVals[FieldNo] = Result; |
| } |
| |
| /// Given a load instruction and a value derived from the load, rewrite the |
| /// derived value to use the HeapSRoA'd load. |
| static void RewriteHeapSROALoadUser(Instruction *LoadUser, |
| DenseMap<Value *, std::vector<Value *>> &InsertedScalarizedValues, |
| std::vector<std::pair<PHINode *, unsigned>> &PHIsToRewrite) { |
| // If this is a comparison against null, handle it. |
| if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) { |
| assert(isa<ConstantPointerNull>(SCI->getOperand(1))); |
| // If we have a setcc of the loaded pointer, we can use a setcc of any |
| // field. |
| Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0, |
| InsertedScalarizedValues, PHIsToRewrite); |
| |
| Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr, |
| Constant::getNullValue(NPtr->getType()), |
| SCI->getName()); |
| SCI->replaceAllUsesWith(New); |
| SCI->eraseFromParent(); |
| return; |
| } |
| |
| // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...' |
| if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) { |
| assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2)) |
| && "Unexpected GEPI!"); |
| |
| // Load the pointer for this field. |
| unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); |
| Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo, |
| InsertedScalarizedValues, PHIsToRewrite); |
| |
| // Create the new GEP idx vector. |
| SmallVector<Value*, 8> GEPIdx; |
| GEPIdx.push_back(GEPI->getOperand(1)); |
| GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end()); |
| |
| Value *NGEPI = GetElementPtrInst::Create(GEPI->getResultElementType(), NewPtr, GEPIdx, |
| GEPI->getName(), GEPI); |
| GEPI->replaceAllUsesWith(NGEPI); |
| GEPI->eraseFromParent(); |
| return; |
| } |
| |
| // Recursively transform the users of PHI nodes. This will lazily create the |
| // PHIs that are needed for individual elements. Keep track of what PHIs we |
| // see in InsertedScalarizedValues so that we don't get infinite loops (very |
| // antisocial). If the PHI is already in InsertedScalarizedValues, it has |
| // already been seen first by another load, so its uses have already been |
| // processed. |
| PHINode *PN = cast<PHINode>(LoadUser); |
| if (!InsertedScalarizedValues.insert(std::make_pair(PN, |
| std::vector<Value *>())).second) |
| return; |
| |
| // If this is the first time we've seen this PHI, recursively process all |
| // users. |
| for (auto UI = PN->user_begin(), E = PN->user_end(); UI != E;) { |
| Instruction *User = cast<Instruction>(*UI++); |
| RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite); |
| } |
| } |
| |
| /// We are performing Heap SRoA on a global. Ptr is a value loaded from the |
| /// global. Eliminate all uses of Ptr, making them use FieldGlobals instead. |
| /// All uses of loaded values satisfy AllGlobalLoadUsesSimpleEnoughForHeapSRA. |
| static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load, |
| DenseMap<Value *, std::vector<Value *>> &InsertedScalarizedValues, |
| std::vector<std::pair<PHINode *, unsigned> > &PHIsToRewrite) { |
| for (auto UI = Load->user_begin(), E = Load->user_end(); UI != E;) { |
| Instruction *User = cast<Instruction>(*UI++); |
| RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite); |
| } |
| |
| if (Load->use_empty()) { |
| Load->eraseFromParent(); |
| InsertedScalarizedValues.erase(Load); |
| } |
| } |
| |
| /// CI is an allocation of an array of structures. Break it up into multiple |
| /// allocations of arrays of the fields. |
| static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI, |
| Value *NElems, const DataLayout &DL, |
| const TargetLibraryInfo *TLI) { |
| LLVM_DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI |
| << '\n'); |
| Type *MAT = getMallocAllocatedType(CI, TLI); |
| StructType *STy = cast<StructType>(MAT); |
| |
| // There is guaranteed to be at least one use of the malloc (storing |
| // it into GV). If there are other uses, change them to be uses of |
| // the global to simplify later code. This also deletes the store |
| // into GV. |
| ReplaceUsesOfMallocWithGlobal(CI, GV); |
| |
| // Okay, at this point, there are no users of the malloc. Insert N |
| // new mallocs at the same place as CI, and N globals. |
| std::vector<Value *> FieldGlobals; |
| std::vector<Value *> FieldMallocs; |
| |
| SmallVector<OperandBundleDef, 1> OpBundles; |
| CI->getOperandBundlesAsDefs(OpBundles); |
| |
| unsigned AS = GV->getType()->getPointerAddressSpace(); |
| for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ |
| Type *FieldTy = STy->getElementType(FieldNo); |
| PointerType *PFieldTy = PointerType::get(FieldTy, AS); |
| |
| GlobalVariable *NGV = new GlobalVariable( |
| *GV->getParent(), PFieldTy, false, GlobalValue::InternalLinkage, |
| Constant::getNullValue(PFieldTy), GV->getName() + ".f" + Twine(FieldNo), |
| nullptr, GV->getThreadLocalMode()); |
| NGV->copyAttributesFrom(GV); |
| FieldGlobals.push_back(NGV); |
| |
| unsigned TypeSize = DL.getTypeAllocSize(FieldTy); |
| if (StructType *ST = dyn_cast<StructType>(FieldTy)) |
| TypeSize = DL.getStructLayout(ST)->getSizeInBytes(); |
| Type *IntPtrTy = DL.getIntPtrType(CI->getType()); |
| Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy, |
| ConstantInt::get(IntPtrTy, TypeSize), |
| NElems, OpBundles, nullptr, |
| CI->getName() + ".f" + Twine(FieldNo)); |
| FieldMallocs.push_back(NMI); |
| new StoreInst(NMI, NGV, CI); |
| } |
| |
| // The tricky aspect of this transformation is handling the case when malloc |
| // fails. In the original code, malloc failing would set the result pointer |
| // of malloc to null. In this case, some mallocs could succeed and others |
| // could fail. As such, we emit code that looks like this: |
| // F0 = malloc(field0) |
| // F1 = malloc(field1) |
| // F2 = malloc(field2) |
| // if (F0 == 0 || F1 == 0 || F2 == 0) { |
| // if (F0) { free(F0); F0 = 0; } |
| // if (F1) { free(F1); F1 = 0; } |
| // if (F2) { free(F2); F2 = 0; } |
| // } |
| // The malloc can also fail if its argument is too large. |
| Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0); |
| Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0), |
| ConstantZero, "isneg"); |
| for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { |
| Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i], |
| Constant::getNullValue(FieldMallocs[i]->getType()), |
| "isnull"); |
| RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI); |
| } |
| |
| // Split the basic block at the old malloc. |
| BasicBlock *OrigBB = CI->getParent(); |
| BasicBlock *ContBB = |
| OrigBB->splitBasicBlock(CI->getIterator(), "malloc_cont"); |
| |
| // Create the block to check the first condition. Put all these blocks at the |
| // end of the function as they are unlikely to be executed. |
| BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(), |
| "malloc_ret_null", |
| OrigBB->getParent()); |
| |
| // Remove the uncond branch from OrigBB to ContBB, turning it into a cond |
| // branch on RunningOr. |
| OrigBB->getTerminator()->eraseFromParent(); |
| BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB); |
| |
| // Within the NullPtrBlock, we need to emit a comparison and branch for each |
| // pointer, because some may be null while others are not. |
| for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { |
| Value *GVVal = |
| new LoadInst(cast<GlobalVariable>(FieldGlobals[i])->getValueType(), |
| FieldGlobals[i], "tmp", NullPtrBlock); |
| Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal, |
| Constant::getNullValue(GVVal->getType())); |
| BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it", |
| OrigBB->getParent()); |
| BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next", |
| OrigBB->getParent()); |
| Instruction *BI = BranchInst::Create(FreeBlock, NextBlock, |
| Cmp, NullPtrBlock); |
| |
| // Fill in FreeBlock. |
| CallInst::CreateFree(GVVal, OpBundles, BI); |
| new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], |
| FreeBlock); |
| BranchInst::Create(NextBlock, FreeBlock); |
| |
| NullPtrBlock = NextBlock; |
| } |
| |
| BranchInst::Create(ContBB, NullPtrBlock); |
| |
| // CI is no longer needed, remove it. |
| CI->eraseFromParent(); |
| |
| /// As we process loads, if we can't immediately update all uses of the load, |
| /// keep track of what scalarized loads are inserted for a given load. |
| DenseMap<Value *, std::vector<Value *>> InsertedScalarizedValues; |
| InsertedScalarizedValues[GV] = FieldGlobals; |
| |
| std::vector<std::pair<PHINode *, unsigned>> PHIsToRewrite; |
| |
| // Okay, the malloc site is completely handled. All of the uses of GV are now |
| // loads, and all uses of those loads are simple. Rewrite them to use loads |
| // of the per-field globals instead. |
| for (auto UI = GV->user_begin(), E = GV->user_end(); UI != E;) { |
| Instruction *User = cast<Instruction>(*UI++); |
| |
| if (LoadInst *LI = dyn_cast<LoadInst>(User)) { |
| RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite); |
| continue; |
| } |
| |
| // Must be a store of null. |
| StoreInst *SI = cast<StoreInst>(User); |
| assert(isa<ConstantPointerNull>(SI->getOperand(0)) && |
| "Unexpected heap-sra user!"); |
| |
| // Insert a store of null into each global. |
| for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { |
| Type *ValTy = cast<GlobalValue>(FieldGlobals[i])->getValueType(); |
| Constant *Null = Constant::getNullValue(ValTy); |
| new StoreInst(Null, FieldGlobals[i], SI); |
| } |
| // Erase the original store. |
| SI->eraseFromParent(); |
| } |
| |
| // While we have PHIs that are interesting to rewrite, do it. |
| while (!PHIsToRewrite.empty()) { |
| PHINode *PN = PHIsToRewrite.back().first; |
| unsigned FieldNo = PHIsToRewrite.back().second; |
| PHIsToRewrite.pop_back(); |
| PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]); |
| assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi"); |
| |
| // Add all the incoming values. This can materialize more phis. |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { |
| Value *InVal = PN->getIncomingValue(i); |
| InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues, |
| PHIsToRewrite); |
| FieldPN->addIncoming(InVal, PN->getIncomingBlock(i)); |
| } |
| } |
| |
| // Drop all inter-phi links and any loads that made it this far. |
| for (DenseMap<Value *, std::vector<Value *>>::iterator |
| I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end(); |
| I != E; ++I) { |
| if (PHINode *PN = dyn_cast<PHINode>(I->first)) |
| PN->dropAllReferences(); |
| else if (LoadInst *LI = dyn_cast<LoadInst>(I->first)) |
| LI->dropAllReferences(); |
| } |
| |
| // Delete all the phis and loads now that inter-references are dead. |
| for (DenseMap<Value *, std::vector<Value *>>::iterator |
| I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end(); |
| I != E; ++I) { |
| if (PHINode *PN = dyn_cast<PHINode>(I->first)) |
| PN->eraseFromParent(); |
| else if (LoadInst *LI = dyn_cast<LoadInst>(I->first)) |
| LI->eraseFromParent(); |
| } |
| |
| // The old global is now dead, remove it. |
| GV->eraseFromParent(); |
| |
| ++NumHeapSRA; |
| return cast<GlobalVariable>(FieldGlobals[0]); |
| } |
| |
| /// This function is called when we see a pointer global variable with a single |
| /// value stored it that is a malloc or cast of malloc. |
| static bool tryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV, CallInst *CI, |
| Type *AllocTy, |
| AtomicOrdering Ordering, |
| const DataLayout &DL, |
| TargetLibraryInfo *TLI) { |
| // If this is a malloc of an abstract type, don't touch it. |
| if (!AllocTy->isSized()) |
| return false; |
| |
| // We can't optimize this global unless all uses of it are *known* to be |
| // of the malloc value, not of the null initializer value (consider a use |
| // that compares the global's value against zero to see if the malloc has |
| // been reached). To do this, we check to see if all uses of the global |
| // would trap if the global were null: this proves that they must all |
| // happen after the malloc. |
| if (!AllUsesOfLoadedValueWillTrapIfNull(GV)) |
| return false; |
| |
| // We can't optimize this if the malloc itself is used in a complex way, |
| // for example, being stored into multiple globals. This allows the |
| // malloc to be stored into the specified global, loaded icmp'd, and |
| // GEP'd. These are all things we could transform to using the global |
| // for. |
| SmallPtrSet<const PHINode*, 8> PHIs; |
| if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs)) |
| return false; |
| |
| // If we have a global that is only initialized with a fixed size malloc, |
| // transform the program to use global memory instead of malloc'd memory. |
| // This eliminates dynamic allocation, avoids an indirection accessing the |
| // data, and exposes the resultant global to further GlobalOpt. |
| // We cannot optimize the malloc if we cannot determine malloc array size. |
| Value *NElems = getMallocArraySize(CI, DL, TLI, true); |
| if (!NElems) |
| return false; |
| |
| if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems)) |
| // Restrict this transformation to only working on small allocations |
| // (2048 bytes currently), as we don't want to introduce a 16M global or |
| // something. |
| if (NElements->getZExtValue() * DL.getTypeAllocSize(AllocTy) < 2048) { |
| OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, DL, TLI); |
| return true; |
| } |
| |
| // If the allocation is an array of structures, consider transforming this |
| // into multiple malloc'd arrays, one for each field. This is basically |
| // SRoA for malloc'd memory. |
| |
| if (Ordering != AtomicOrdering::NotAtomic) |
| return false; |
| |
| // If this is an allocation of a fixed size array of structs, analyze as a |
| // variable size array. malloc [100 x struct],1 -> malloc struct, 100 |
| if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1)) |
| if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy)) |
| AllocTy = AT->getElementType(); |
| |
| StructType *AllocSTy = dyn_cast<StructType>(AllocTy); |
| if (!AllocSTy) |
| return false; |
| |
| // This the structure has an unreasonable number of fields, leave it |
| // alone. |
| if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 && |
| AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) { |
| |
| // If this is a fixed size array, transform the Malloc to be an alloc of |
| // structs. malloc [100 x struct],1 -> malloc struct, 100 |
| if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI, TLI))) { |
| Type *IntPtrTy = DL.getIntPtrType(CI->getType()); |
| unsigned TypeSize = DL.getStructLayout(AllocSTy)->getSizeInBytes(); |
| Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize); |
| Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements()); |
| SmallVector<OperandBundleDef, 1> OpBundles; |
| CI->getOperandBundlesAsDefs(OpBundles); |
| Instruction *Malloc = |
| CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy, AllocSize, NumElements, |
| OpBundles, nullptr, CI->getName()); |
| Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI); |
| CI->replaceAllUsesWith(Cast); |
| CI->eraseFromParent(); |
| if (BitCastInst *BCI = dyn_cast<BitCastInst>(Malloc)) |
| CI = cast<CallInst>(BCI->getOperand(0)); |
| else |
| CI = cast<CallInst>(Malloc); |
| } |
| |
| PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, DL, TLI, true), DL, |
| TLI); |
| return true; |
| } |
| |
| return false; |
| } |
| |
| // Try to optimize globals based on the knowledge that only one value (besides |
| // its initializer) is ever stored to the global. |
| static bool |
| optimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal, |
| AtomicOrdering Ordering, const DataLayout &DL, |
| function_ref<TargetLibraryInfo &(Function &)> GetTLI) { |
| // Ignore no-op GEPs and bitcasts. |
| StoredOnceVal = StoredOnceVal->stripPointerCasts(); |
| |
| // If we are dealing with a pointer global that is initialized to null and |
| // only has one (non-null) value stored into it, then we can optimize any |
| // users of the loaded value (often calls and loads) that would trap if the |
| // value was null. |
| if (GV->getInitializer()->getType()->isPointerTy() && |
| GV->getInitializer()->isNullValue() && |
| !NullPointerIsDefined( |
| nullptr /* F */, |
| GV->getInitializer()->getType()->getPointerAddressSpace())) { |
| if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) { |
| if (GV->getInitializer()->getType() != SOVC->getType()) |
| SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType()); |
| |
| // Optimize away any trapping uses of the loaded value. |
| if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, DL, GetTLI)) |
| return true; |
| } else if (CallInst *CI = extractMallocCall(StoredOnceVal, GetTLI)) { |
| auto *TLI = &GetTLI(*CI->getFunction()); |
| Type *MallocType = getMallocAllocatedType(CI, TLI); |
| if (MallocType && tryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, |
| Ordering, DL, TLI)) |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| /// At this point, we have learned that the only two values ever stored into GV |
| /// are its initializer and OtherVal. See if we can shrink the global into a |
| /// boolean and select between the two values whenever it is used. This exposes |
| /// the values to other scalar optimizations. |
| static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) { |
| Type *GVElType = GV->getValueType(); |
| |
| // If GVElType is already i1, it is already shrunk. If the type of the GV is |
| // an FP value, pointer or vector, don't do this optimization because a select |
| // between them is very expensive and unlikely to lead to later |
| // simplification. In these cases, we typically end up with "cond ? v1 : v2" |
| // where v1 and v2 both require constant pool loads, a big loss. |
| if (GVElType == Type::getInt1Ty(GV->getContext()) || |
| GVElType->isFloatingPointTy() || |
| GVElType->isPointerTy() || GVElType->isVectorTy()) |
| return false; |
| |
| // Walk the use list of the global seeing if all the uses are load or store. |
| // If there is anything else, bail out. |
| for (User *U : GV->users()) |
| if (!isa<LoadInst>(U) && !isa<StoreInst>(U)) |
| return false; |
| |
| LLVM_DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV << "\n"); |
| |
| // Create the new global, initializing it to false. |
| GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()), |
| false, |
| GlobalValue::InternalLinkage, |
| ConstantInt::getFalse(GV->getContext()), |
| GV->getName()+".b", |
| GV->getThreadLocalMode(), |
| GV->getType()->getAddressSpace()); |
| NewGV->copyAttributesFrom(GV); |
| GV->getParent()->getGlobalList().insert(GV->getIterator(), NewGV); |
| |
| Constant *InitVal = GV->getInitializer(); |
| assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) && |
| "No reason to shrink to bool!"); |
| |
| SmallVector<DIGlobalVariableExpression *, 1> GVs; |
| GV->getDebugInfo(GVs); |
| |
| // If initialized to zero and storing one into the global, we can use a cast |
| // instead of a select to synthesize the desired value. |
| bool IsOneZero = false; |
| bool EmitOneOrZero = true; |
| auto *CI = dyn_cast<ConstantInt>(OtherVal); |
| if (CI && CI->getValue().getActiveBits() <= 64) { |
| IsOneZero = InitVal->isNullValue() && CI->isOne(); |
| |
| auto *CIInit = dyn_cast<ConstantInt>(GV->getInitializer()); |
| if (CIInit && CIInit->getValue().getActiveBits() <= 64) { |
| uint64_t ValInit = CIInit->getZExtValue(); |
| uint64_t ValOther = CI->getZExtValue(); |
| uint64_t ValMinus = ValOther - ValInit; |
| |
| for(auto *GVe : GVs){ |
| DIGlobalVariable *DGV = GVe->getVariable(); |
| DIExpression *E = GVe->getExpression(); |
| const DataLayout &DL = GV->getParent()->getDataLayout(); |
| unsigned SizeInOctets = |
| DL.getTypeAllocSizeInBits(NewGV->getType()->getElementType()) / 8; |
| |
| // It is expected that the address of global optimized variable is on |
| // top of the stack. After optimization, value of that variable will |
| // be ether 0 for initial value or 1 for other value. The following |
| // expression should return constant integer value depending on the |
| // value at global object address: |
| // val * (ValOther - ValInit) + ValInit: |
| // DW_OP_deref DW_OP_constu <ValMinus> |
| // DW_OP_mul DW_OP_constu <ValInit> DW_OP_plus DW_OP_stack_value |
| SmallVector<uint64_t, 12> Ops = { |
| dwarf::DW_OP_deref_size, SizeInOctets, |
| dwarf::DW_OP_constu, ValMinus, |
| dwarf::DW_OP_mul, dwarf::DW_OP_constu, ValInit, |
| dwarf::DW_OP_plus}; |
| bool WithStackValue = true; |
| E = DIExpression::prependOpcodes(E, Ops, WithStackValue); |
| DIGlobalVariableExpression *DGVE = |
| DIGlobalVariableExpression::get(NewGV->getContext(), DGV, E); |
| NewGV->addDebugInfo(DGVE); |
| } |
| EmitOneOrZero = false; |
| } |
| } |
| |
| if (EmitOneOrZero) { |
| // FIXME: This will only emit address for debugger on which will |
| // be written only 0 or 1. |
| for(auto *GV : GVs) |
| NewGV->addDebugInfo(GV); |
| } |
| |
| while (!GV->use_empty()) { |
| Instruction *UI = cast<Instruction>(GV->user_back()); |
| if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { |
| // Change the store into a boolean store. |
| bool StoringOther = SI->getOperand(0) == OtherVal; |
| // Only do this if we weren't storing a loaded value. |
| Value *StoreVal; |
| if (StoringOther || SI->getOperand(0) == InitVal) { |
| StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()), |
| StoringOther); |
| } else { |
| // Otherwise, we are storing a previously loaded copy. To do this, |
| // change the copy from copying the original value to just copying the |
| // bool. |
| Instruction *StoredVal = cast<Instruction>(SI->getOperand(0)); |
| |
| // If we've already replaced the input, StoredVal will be a cast or |
| // select instruction. If not, it will be a load of the original |
| // global. |
| if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) { |
| assert(LI->getOperand(0) == GV && "Not a copy!"); |
| // Insert a new load, to preserve the saved value. |
| StoreVal = new LoadInst(NewGV->getValueType(), NewGV, |
| LI->getName() + ".b", false, None, |
| LI->getOrdering(), LI->getSyncScopeID(), LI); |
| } else { |
| assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) && |
| "This is not a form that we understand!"); |
| StoreVal = StoredVal->getOperand(0); |
| assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!"); |
| } |
| } |
| StoreInst *NSI = |
| new StoreInst(StoreVal, NewGV, false, None, SI->getOrdering(), |
| SI->getSyncScopeID(), SI); |
| NSI->setDebugLoc(SI->getDebugLoc()); |
| } else { |
| // Change the load into a load of bool then a select. |
| LoadInst *LI = cast<LoadInst>(UI); |
| LoadInst *NLI = new LoadInst(NewGV->getValueType(), NewGV, |
| LI->getName() + ".b", false, None, |
| LI->getOrdering(), LI->getSyncScopeID(), LI); |
| Instruction *NSI; |
| if (IsOneZero) |
| NSI = new ZExtInst(NLI, LI->getType(), "", LI); |
| else |
| NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI); |
| NSI->takeName(LI); |
| // Since LI is split into two instructions, NLI and NSI both inherit the |
| // same DebugLoc |
| NLI->setDebugLoc(LI->getDebugLoc()); |
| NSI->setDebugLoc(LI->getDebugLoc()); |
| LI->replaceAllUsesWith(NSI); |
| } |
| UI->eraseFromParent(); |
| } |
| |
| // Retain the name of the old global variable. People who are debugging their |
| // programs may expect these variables to be named the same. |
| NewGV->takeName(GV); |
| GV->eraseFromParent(); |
| return true; |
| } |
| |
| static bool deleteIfDead( |
| GlobalValue &GV, SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats) { |
| GV.removeDeadConstantUsers(); |
| |
| if (!GV.isDiscardableIfUnused() && !GV.isDeclaration()) |
| return false; |
| |
| if (const Comdat *C = GV.getComdat()) |
| if (!GV.hasLocalLinkage() && NotDiscardableComdats.count(C)) |
| return false; |
| |
| bool Dead; |
| if (auto *F = dyn_cast<Function>(&GV)) |
| Dead = (F->isDeclaration() && F->use_empty()) || F->isDefTriviallyDead(); |
| else |
| Dead = GV.use_empty(); |
| if (!Dead) |
| return false; |
| |
| LLVM_DEBUG(dbgs() << "GLOBAL DEAD: " << GV << "\n"); |
| GV.eraseFromParent(); |
| ++NumDeleted; |
| return true; |
| } |
| |
| static bool isPointerValueDeadOnEntryToFunction( |
| const Function *F, GlobalValue *GV, |
| function_ref<DominatorTree &(Function &)> LookupDomTree) { |
| // Find all uses of GV. We expect them all to be in F, and if we can't |
| // identify any of the uses we bail out. |
| // |
| // On each of these uses, identify if the memory that GV points to is |
| // used/required/live at the start of the function. If it is not, for example |
| // if the first thing the function does is store to the GV, the GV can |
| // possibly be demoted. |
| // |
| // We don't do an exhaustive search for memory operations - simply look |
| // through bitcasts as they're quite common and benign. |
| const DataLayout &DL = GV->getParent()->getDataLayout(); |
| SmallVector<LoadInst *, 4> Loads; |
| SmallVector<StoreInst *, 4> Stores; |
| for (auto *U : GV->users()) { |
| if (Operator::getOpcode(U) == Instruction::BitCast) { |
| for (auto *UU : U->users()) { |
| if (auto *LI = dyn_cast<LoadInst>(UU)) |
| Loads.push_back(LI); |
| else if (auto *SI = dyn_cast<StoreInst>(UU)) |
| Stores.push_back(SI); |
| else |
| return false; |
| } |
| continue; |
| } |
| |
| Instruction *I = dyn_cast<Instruction>(U); |
| if (!I) |
| return false; |
| assert(I->getParent()->getParent() == F); |
| |
| if (auto *LI = dyn_cast<LoadInst>(I)) |
| Loads.push_back(LI); |
| else if (auto *SI = dyn_cast<StoreInst>(I)) |
| Stores.push_back(SI); |
| else |
| return false; |
| } |
| |
| // We have identified all uses of GV into loads and stores. Now check if all |
| // of them are known not to depend on the value of the global at the function |
| // entry point. We do this by ensuring that every load is dominated by at |
| // least one store. |
| auto &DT = LookupDomTree(*const_cast<Function *>(F)); |
| |
| // The below check is quadratic. Check we're not going to do too many tests. |
| // FIXME: Even though this will always have worst-case quadratic time, we |
| // could put effort into minimizing the average time by putting stores that |
| // have been shown to dominate at least one load at the beginning of the |
| // Stores array, making subsequent dominance checks more likely to succeed |
| // early. |
| // |
| // The threshold here is fairly large because global->local demotion is a |
| // very powerful optimization should it fire. |
| const unsigned Threshold = 100; |
| if (Loads.size() * Stores.size() > Threshold) |
| return false; |
| |
| for (auto *L : Loads) { |
| auto *LTy = L->getType(); |
| if (none_of(Stores, [&](const StoreInst *S) { |
| auto *STy = S->getValueOperand()->getType(); |
| // The load is only dominated by the store if DomTree says so |
| // and the number of bits loaded in L is less than or equal to |
| // the number of bits stored in S. |
| return DT.dominates(S, L) && |
| DL.getTypeStoreSize(LTy) <= DL.getTypeStoreSize(STy); |
| })) |
| return false; |
| } |
| // All loads have known dependences inside F, so the global can be localized. |
| return true; |
| } |
| |
| /// C may have non-instruction users. Can all of those users be turned into |
| /// instructions? |
| static bool allNonInstructionUsersCanBeMadeInstructions(Constant *C) { |
| // We don't do this exhaustively. The most common pattern that we really need |
| // to care about is a constant GEP or constant bitcast - so just looking |
| // through one single ConstantExpr. |
| // |
| // The set of constants that this function returns true for must be able to be |
| // handled by makeAllConstantUsesInstructions. |
| for (auto *U : C->users()) { |
| if (isa<Instruction>(U)) |
| continue; |
| if (!isa<ConstantExpr>(U)) |
| // Non instruction, non-constantexpr user; cannot convert this. |
| return false; |
| for (auto *UU : U->users()) |
| if (!isa<Instruction>(UU)) |
| // A constantexpr used by another constant. We don't try and recurse any |
| // further but just bail out at this point. |
| return false; |
| } |
| |
| return true; |
| } |
| |
| /// C may have non-instruction users, and |
| /// allNonInstructionUsersCanBeMadeInstructions has returned true. Convert the |
| /// non-instruction users to instructions. |
| static void makeAllConstantUsesInstructions(Constant *C) { |
| SmallVector<ConstantExpr*,4> Users; |
| for (auto *U : C->users()) { |
| if (isa<ConstantExpr>(U)) |
| Users.push_back(cast<ConstantExpr>(U)); |
| else |
| // We should never get here; allNonInstructionUsersCanBeMadeInstructions |
| // should not have returned true for C. |
| assert( |
| isa<Instruction>(U) && |
| "Can't transform non-constantexpr non-instruction to instruction!"); |
| } |
| |
| SmallVector<Value*,4> UUsers; |
| for (auto *U : Users) { |
| UUsers.clear(); |
| for (auto *UU : U->users()) |
| UUsers.push_back(UU); |
| for (auto *UU : UUsers) { |
| Instruction *UI = cast<Instruction>(UU); |
| Instruction *NewU = U->getAsInstruction(); |
| NewU->insertBefore(UI); |
| UI->replaceUsesOfWith(U, NewU); |
| } |
| // We've replaced all the uses, so destroy the constant. (destroyConstant |
| // will update value handles and metadata.) |
| U->destroyConstant(); |
| } |
| } |
| |
| /// Analyze the specified global variable and optimize |
| /// it if possible. If we make a change, return true. |
| static bool |
| processInternalGlobal(GlobalVariable *GV, const GlobalStatus &GS, |
| function_ref<TargetLibraryInfo &(Function &)> GetTLI, |
| function_ref<DominatorTree &(Function &)> LookupDomTree) { |
| auto &DL = GV->getParent()->getDataLayout(); |
| // If this is a first class global and has only one accessing function and |
| // this function is non-recursive, we replace the global with a local alloca |
| // in this function. |
| // |
| // NOTE: It doesn't make sense to promote non-single-value types since we |
| // are just replacing static memory to stack memory. |
| // |
| // If the global is in different address space, don't bring it to stack. |
| if (!GS.HasMultipleAccessingFunctions && |
| GS.AccessingFunction && |
| GV->getValueType()->isSingleValueType() && |
| GV->getType()->getAddressSpace() == 0 && |
| !GV->isExternallyInitialized() && |
| allNonInstructionUsersCanBeMadeInstructions(GV) && |
| GS.AccessingFunction->doesNotRecurse() && |
| isPointerValueDeadOnEntryToFunction(GS.AccessingFunction, GV, |
| LookupDomTree)) { |
| const DataLayout &DL = GV->getParent()->getDataLayout(); |
| |
| LLVM_DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV << "\n"); |
| Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction |
| ->getEntryBlock().begin()); |
| Type *ElemTy = GV->getValueType(); |
| // FIXME: Pass Global's alignment when globals have alignment |
| AllocaInst *Alloca = new AllocaInst(ElemTy, DL.getAllocaAddrSpace(), nullptr, |
| GV->getName(), &FirstI); |
| if (!isa<UndefValue>(GV->getInitializer())) |
| new StoreInst(GV->getInitializer(), Alloca, &FirstI); |
| |
| makeAllConstantUsesInstructions(GV); |
| |
| GV->replaceAllUsesWith(Alloca); |
| GV->eraseFromParent(); |
| ++NumLocalized; |
| return true; |
| } |
| |
| // If the global is never loaded (but may be stored to), it is dead. |
| // Delete it now. |
| if (!GS.IsLoaded) { |
| LLVM_DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV << "\n"); |
| |
| bool Changed; |
| if (isLeakCheckerRoot(GV)) { |
| // Delete any constant stores to the global. |
| Changed = CleanupPointerRootUsers(GV, GetTLI); |
| } else { |
| // Delete any stores we can find to the global. We may not be able to |
| // make it completely dead though. |
| Changed = |
| CleanupConstantGlobalUsers(GV, GV->getInitializer(), DL, GetTLI); |
| } |
| |
| // If the global is dead now, delete it. |
| if (GV->use_empty()) { |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| Changed = true; |
| } |
| return Changed; |
| |
| } |
| if (GS.StoredType <= GlobalStatus::InitializerStored) { |
| LLVM_DEBUG(dbgs() << "MARKING CONSTANT: " << *GV << "\n"); |
| |
| // Don't actually mark a global constant if it's atomic because atomic loads |
| // are implemented by a trivial cmpxchg in some edge-cases and that usually |
| // requires write access to the variable even if it's not actually changed. |
| if (GS.Ordering == AtomicOrdering::NotAtomic) |
| GV->setConstant(true); |
| |
| // Clean up any obviously simplifiable users now. |
| CleanupConstantGlobalUsers(GV, GV->getInitializer(), DL, GetTLI); |
| |
| // If the global is dead now, just nuke it. |
| if (GV->use_empty()) { |
| LLVM_DEBUG(dbgs() << " *** Marking constant allowed us to simplify " |
| << "all users and delete global!\n"); |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| return true; |
| } |
| |
| // Fall through to the next check; see if we can optimize further. |
| ++NumMarked; |
| } |
| if (!GV->getInitializer()->getType()->isSingleValueType()) { |
| const DataLayout &DL = GV->getParent()->getDataLayout(); |
| if (SRAGlobal(GV, DL)) |
| return true; |
| } |
| if (GS.StoredType == GlobalStatus::StoredOnce && GS.StoredOnceValue) { |
| // If the initial value for the global was an undef value, and if only |
| // one other value was stored into it, we can just change the |
| // initializer to be the stored value, then delete all stores to the |
| // global. This allows us to mark it constant. |
| if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) |
| if (isa<UndefValue>(GV->getInitializer())) { |
| // Change the initial value here. |
| GV->setInitializer(SOVConstant); |
| |
| // Clean up any obviously simplifiable users now. |
| CleanupConstantGlobalUsers(GV, GV->getInitializer(), DL, GetTLI); |
| |
| if (GV->use_empty()) { |
| LLVM_DEBUG(dbgs() << " *** Substituting initializer allowed us to " |
| << "simplify all users and delete global!\n"); |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| } |
| ++NumSubstitute; |
| return true; |
| } |
| |
| // Try to optimize globals based on the knowledge that only one value |
| // (besides its initializer) is ever stored to the global. |
| if (optimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GS.Ordering, DL, |
| GetTLI)) |
| return true; |
| |
| // Otherwise, if the global was not a boolean, we can shrink it to be a |
| // boolean. |
| if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) { |
| if (GS.Ordering == AtomicOrdering::NotAtomic) { |
| if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) { |
| ++NumShrunkToBool; |
| return true; |
| } |
| } |
| } |
| } |
| |
| return false; |
| } |
| |
| /// Analyze the specified global variable and optimize it if possible. If we |
| /// make a change, return true. |
| static bool |
| processGlobal(GlobalValue &GV, |
| function_ref<TargetLibraryInfo &(Function &)> GetTLI, |
| function_ref<DominatorTree &(Function &)> LookupDomTree) { |
| if (GV.getName().startswith("llvm.")) |
| return false; |
| |
| GlobalStatus GS; |
| |
| if (GlobalStatus::analyzeGlobal(&GV, GS)) |
| return false; |
| |
| bool Changed = false; |
| if (!GS.IsCompared && !GV.hasGlobalUnnamedAddr()) { |
| auto NewUnnamedAddr = GV.hasLocalLinkage() ? GlobalValue::UnnamedAddr::Global |
| : GlobalValue::UnnamedAddr::Local; |
| if (NewUnnamedAddr != GV.getUnnamedAddr()) { |
| GV.setUnnamedAddr(NewUnnamedAddr); |
| NumUnnamed++; |
| Changed = true; |
| } |
| } |
| |
| // Do more involved optimizations if the global is internal. |
| if (!GV.hasLocalLinkage()) |
| return Changed; |
| |
| auto *GVar = dyn_cast<GlobalVariable>(&GV); |
| if (!GVar) |
| return Changed; |
| |
| if (GVar->isConstant() || !GVar->hasInitializer()) |
| return Changed; |
| |
| return processInternalGlobal(GVar, GS, GetTLI, LookupDomTree) || Changed; |
| } |
| |
| /// Walk all of the direct calls of the specified function, changing them to |
| /// FastCC. |
| static void ChangeCalleesToFastCall(Function *F) { |
| for (User *U : F->users()) { |
| if (isa<BlockAddress>(U)) |
| continue; |
| CallSite CS(cast<Instruction>(U)); |
| CS.setCallingConv(CallingConv::Fast); |
| } |
| } |
| |
| static AttributeList StripAttr(LLVMContext &C, AttributeList Attrs, |
| Attribute::AttrKind A) { |
| unsigned AttrIndex; |
| if (Attrs.hasAttrSomewhere(A, &AttrIndex)) |
| return Attrs.removeAttribute(C, AttrIndex, A); |
| return Attrs; |
| } |
| |
| static void RemoveAttribute(Function *F, Attribute::AttrKind A) { |
| F->setAttributes(StripAttr(F->getContext(), F->getAttributes(), A)); |
| for (User *U : F->users()) { |
| if (isa<BlockAddress>(U)) |
| continue; |
| CallSite CS(cast<Instruction>(U)); |
| CS.setAttributes(StripAttr(F->getContext(), CS.getAttributes(), A)); |
| } |
| } |
| |
| /// Return true if this is a calling convention that we'd like to change. The |
| /// idea here is that we don't want to mess with the convention if the user |
| /// explicitly requested something with performance implications like coldcc, |
| /// GHC, or anyregcc. |
| static bool hasChangeableCC(Function *F) { |
| CallingConv::ID CC = F->getCallingConv(); |
| |
| // FIXME: Is it worth transforming x86_stdcallcc and x86_fastcallcc? |
| if (CC != CallingConv::C && CC != CallingConv::X86_ThisCall) |
| return false; |
| |
| // FIXME: Change CC for the whole chain of musttail calls when possible. |
| // |
| // Can't change CC of the function that either has musttail calls, or is a |
| // musttail callee itself |
| for (User *U : F->users()) { |
| if (isa<BlockAddress>(U)) |
| continue; |
| CallInst* CI = dyn_cast<CallInst>(U); |
| if (!CI) |
| continue; |
| |
| if (CI->isMustTailCall()) |
| return false; |
| } |
| |
| for (BasicBlock &BB : *F) |
| if (BB.getTerminatingMustTailCall()) |
| return false; |
| |
| return true; |
| } |
| |
| /// Return true if the block containing the call site has a BlockFrequency of |
| /// less than ColdCCRelFreq% of the entry block. |
| static bool isColdCallSite(CallSite CS, BlockFrequencyInfo &CallerBFI) { |
| const BranchProbability ColdProb(ColdCCRelFreq, 100); |
| auto CallSiteBB = CS.getInstruction()->getParent(); |
| auto CallSiteFreq = CallerBFI.getBlockFreq(CallSiteBB); |
| auto CallerEntryFreq = |
| CallerBFI.getBlockFreq(&(CS.getCaller()->getEntryBlock())); |
| return CallSiteFreq < CallerEntryFreq * ColdProb; |
| } |
| |
| // This function checks if the input function F is cold at all call sites. It |
| // also looks each call site's containing function, returning false if the |
| // caller function contains other non cold calls. The input vector AllCallsCold |
| // contains a list of functions that only have call sites in cold blocks. |
| static bool |
| isValidCandidateForColdCC(Function &F, |
| function_ref<BlockFrequencyInfo &(Function &)> GetBFI, |
| const std::vector<Function *> &AllCallsCold) { |
| |
| if (F.user_empty()) |
| return false; |
| |
| for (User *U : F.users()) { |
| if (isa<BlockAddress>(U)) |
| continue; |
| |
| CallSite CS(cast<Instruction>(U)); |
| Function *CallerFunc = CS.getInstruction()->getParent()->getParent(); |
| BlockFrequencyInfo &CallerBFI = GetBFI(*CallerFunc); |
| if (!isColdCallSite(CS, CallerBFI)) |
| return false; |
| auto It = std::find(AllCallsCold.begin(), AllCallsCold.end(), CallerFunc); |
| if (It == AllCallsCold.end()) |
| return false; |
| } |
| return true; |
| } |
| |
| static void changeCallSitesToColdCC(Function *F) { |
| for (User *U : F->users()) { |
| if (isa<BlockAddress>(U)) |
| continue; |
| CallSite CS(cast<Instruction>(U)); |
| CS.setCallingConv(CallingConv::Cold); |
| } |
| } |
| |
| // This function iterates over all the call instructions in the input Function |
| // and checks that all call sites are in cold blocks and are allowed to use the |
| // coldcc calling convention. |
| static bool |
| hasOnlyColdCalls(Function &F, |
| function_ref<BlockFrequencyInfo &(Function &)> GetBFI) { |
| for (BasicBlock &BB : F) { |
| for (Instruction &I : BB) { |
| if (CallInst *CI = dyn_cast<CallInst>(&I)) { |
| CallSite CS(cast<Instruction>(CI)); |
| // Skip over isline asm instructions since they aren't function calls. |
| if (CI->isInlineAsm()) |
| continue; |
| Function *CalledFn = CI->getCalledFunction(); |
| if (!CalledFn) |
| return false; |
| if (!CalledFn->hasLocalLinkage()) |
| return false; |
| // Skip over instrinsics since they won't remain as function calls. |
| if (CalledFn->getIntrinsicID() != Intrinsic::not_intrinsic) |
| continue; |
| // Check if it's valid to use coldcc calling convention. |
| if (!hasChangeableCC(CalledFn) || CalledFn->isVarArg() || |
| CalledFn->hasAddressTaken()) |
| return false; |
| BlockFrequencyInfo &CallerBFI = GetBFI(F); |
| if (!isColdCallSite(CS, CallerBFI)) |
| return false; |
| } |
| } |
| } |
| return true; |
| } |
| |
| static bool |
| OptimizeFunctions(Module &M, |
| function_ref<TargetLibraryInfo &(Function &)> GetTLI, |
| function_ref<TargetTransformInfo &(Function &)> GetTTI, |
| function_ref<BlockFrequencyInfo &(Function &)> GetBFI, |
| function_ref<DominatorTree &(Function &)> LookupDomTree, |
| SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats) { |
| |
| bool Changed = false; |
| |
| std::vector<Function *> AllCallsCold; |
| for (Module::iterator FI = M.begin(), E = M.end(); FI != E;) { |
| Function *F = &*FI++; |
| if (hasOnlyColdCalls(*F, GetBFI)) |
| AllCallsCold.push_back(F); |
| } |
| |
| // Optimize functions. |
| for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) { |
| Function *F = &*FI++; |
| |
| // Don't perform global opt pass on naked functions; we don't want fast |
| // calling conventions for naked functions. |
| if (F->hasFnAttribute(Attribute::Naked)) |
| continue; |
| |
| // Functions without names cannot be referenced outside this module. |
| if (!F->hasName() && !F->isDeclaration() && !F->hasLocalLinkage()) |
| F->setLinkage(GlobalValue::InternalLinkage); |
| |
| if (deleteIfDead(*F, NotDiscardableComdats)) { |
| Changed = true; |
| continue; |
| } |
| |
| // LLVM's definition of dominance allows instructions that are cyclic |
| // in unreachable blocks, e.g.: |
| // %pat = select i1 %condition, @global, i16* %pat |
| // because any instruction dominates an instruction in a block that's |
| // not reachable from entry. |
| // So, remove unreachable blocks from the function, because a) there's |
| // no point in analyzing them and b) GlobalOpt should otherwise grow |
| // some more complicated logic to break these cycles. |
| if (!F->isDeclaration()) { |
| auto &DT = LookupDomTree(*F); |
| DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Lazy); |
| Changed |= removeUnreachableBlocks(*F, &DTU); |
| } |
| |
| Changed |= processGlobal(*F, GetTLI, LookupDomTree); |
| |
| if (!F->hasLocalLinkage()) |
| continue; |
| |
| // If we have an inalloca parameter that we can safely remove the |
| // inalloca attribute from, do so. This unlocks optimizations that |
| // wouldn't be safe in the presence of inalloca. |
| // FIXME: We should also hoist alloca affected by this to the entry |
| // block if possible. |
| if (F->getAttributes().hasAttrSomewhere(Attribute::InAlloca) && |
| !F->hasAddressTaken()) { |
| RemoveAttribute(F, Attribute::InAlloca); |
| Changed = true; |
| } |
| |
| if (hasChangeableCC(F) && !F->isVarArg() && !F->hasAddressTaken()) { |
| NumInternalFunc++; |
| TargetTransformInfo &TTI = GetTTI(*F); |
| // Change the calling convention to coldcc if either stress testing is |
| // enabled or the target would like to use coldcc on functions which are |
| // cold at all call sites and the callers contain no other non coldcc |
| // calls. |
| if (EnableColdCCStressTest || |
| (TTI.useColdCCForColdCall(*F) && |
| isValidCandidateForColdCC(*F, GetBFI, AllCallsCold))) { |
| F->setCallingConv(CallingConv::Cold); |
| changeCallSitesToColdCC(F); |
| Changed = true; |
| NumColdCC++; |
| } |
| } |
| |
| if (hasChangeableCC(F) && !F->isVarArg() && |
| !F->hasAddressTaken()) { |
| // If this function has a calling convention worth changing, is not a |
| // varargs function, and is only called directly, promote it to use the |
| // Fast calling convention. |
| F->setCallingConv(CallingConv::Fast); |
| ChangeCalleesToFastCall(F); |
| ++NumFastCallFns; |
| Changed = true; |
| } |
| |
| if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) && |
| !F->hasAddressTaken()) { |
| // The function is not used by a trampoline intrinsic, so it is safe |
| // to remove the 'nest' attribute. |
| RemoveAttribute(F, Attribute::Nest); |
| ++NumNestRemoved; |
| Changed = true; |
| } |
| } |
| return Changed; |
| } |
| |
| static bool |
| OptimizeGlobalVars(Module &M, |
| function_ref<TargetLibraryInfo &(Function &)> GetTLI, |
| function_ref<DominatorTree &(Function &)> LookupDomTree, |
| SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats) { |
| bool Changed = false; |
| |
| for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); |
| GVI != E; ) { |
| GlobalVariable *GV = &*GVI++; |
| // Global variables without names cannot be referenced outside this module. |
| if (!GV->hasName() && !GV->isDeclaration() && !GV->hasLocalLinkage()) |
| GV->setLinkage(GlobalValue::InternalLinkage); |
| // Simplify the initializer. |
| if (GV->hasInitializer()) |
| if (auto *C = dyn_cast<Constant>(GV->getInitializer())) { |
| auto &DL = M.getDataLayout(); |
| // TLI is not used in the case of a Constant, so use default nullptr |
| // for that optional parameter, since we don't have a Function to |
| // provide GetTLI anyway. |
| Constant *New = ConstantFoldConstant(C, DL, /*TLI*/ nullptr); |
| if (New && New != C) |
| GV->setInitializer(New); |
| } |
| |
| if (deleteIfDead(*GV, NotDiscardableComdats)) { |
| Changed = true; |
| continue; |
| } |
| |
| Changed |= processGlobal(*GV, GetTLI, LookupDomTree); |
| } |
| return Changed; |
| } |
| |
| /// Evaluate a piece of a constantexpr store into a global initializer. This |
| /// returns 'Init' modified to reflect 'Val' stored into it. At this point, the |
| /// GEP operands of Addr [0, OpNo) have been stepped into. |
| static Constant *EvaluateStoreInto(Constant *Init, Constant *Val, |
| ConstantExpr *Addr, unsigned OpNo) { |
| // Base case of the recursion. |
| if (OpNo == Addr->getNumOperands()) { |
| assert(Val->getType() == Init->getType() && "Type mismatch!"); |
| return Val; |
| } |
| |
| SmallVector<Constant*, 32> Elts; |
| if (StructType *STy = dyn_cast<StructType>(Init->getType())) { |
| // Break up the constant into its elements. |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) |
| Elts.push_back(Init->getAggregateElement(i)); |
| |
| // Replace the element that we are supposed to. |
| ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo)); |
| unsigned Idx = CU->getZExtValue(); |
| assert(Idx < STy->getNumElements() && "Struct index out of range!"); |
| Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1); |
| |
| // Return the modified struct. |
| return ConstantStruct::get(STy, Elts); |
| } |
| |
| ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); |
| SequentialType *InitTy = cast<SequentialType>(Init->getType()); |
| uint64_t NumElts = InitTy->getNumElements(); |
| |
| // Break up the array into elements. |
| for (uint64_t i = 0, e = NumElts; i != e; ++i) |
| Elts.push_back(Init->getAggregateElement(i)); |
| |
| assert(CI->getZExtValue() < NumElts); |
| Elts[CI->getZExtValue()] = |
| EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); |
| |
| if (Init->getType()->isArrayTy()) |
| return ConstantArray::get(cast<ArrayType>(InitTy), Elts); |
| return ConstantVector::get(Elts); |
| } |
| |
| /// We have decided that Addr (which satisfies the predicate |
| /// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen. |
| static void CommitValueTo(Constant *Val, Constant *Addr) { |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) { |
| assert(GV->hasInitializer()); |
| GV->setInitializer(Val); |
| return; |
| } |
| |
| ConstantExpr *CE = cast<ConstantExpr>(Addr); |
| GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); |
| GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2)); |
| } |
| |
| /// Given a map of address -> value, where addresses are expected to be some form |
| /// of either a global or a constant GEP, set the initializer for the address to |
| /// be the value. This performs mostly the same function as CommitValueTo() |
| /// and EvaluateStoreInto() but is optimized to be more efficient for the common |
| /// case where the set of addresses are GEPs sharing the same underlying global, |
| /// processing the GEPs in batches rather than individually. |
| /// |
| /// To give an example, consider the following C++ code adapted from the clang |
| /// regression tests: |
| /// struct S { |
| /// int n = 10; |
| /// int m = 2 * n; |
| /// S(int a) : n(a) {} |
| /// }; |
| /// |
| /// template<typename T> |
| /// struct U { |
| /// T *r = &q; |
| /// T q = 42; |
| /// U *p = this; |
| /// }; |
| /// |
| /// U<S> e; |
| /// |
| /// The global static constructor for 'e' will need to initialize 'r' and 'p' of |
| /// the outer struct, while also initializing the inner 'q' structs 'n' and 'm' |
| /// members. This batch algorithm will simply use general CommitValueTo() method |
| /// to handle the complex nested S struct initialization of 'q', before |
| /// processing the outermost members in a single batch. Using CommitValueTo() to |
| /// handle member in the outer struct is inefficient when the struct/array is |
| /// very large as we end up creating and destroy constant arrays for each |
| /// initialization. |
| /// For the above case, we expect the following IR to be generated: |
| /// |
| /// %struct.U = type { %struct.S*, %struct.S, %struct.U* } |
| /// %struct.S = type { i32, i32 } |
| /// @e = global %struct.U { %struct.S* gep inbounds (%struct.U, %struct.U* @e, |
| /// i64 0, i32 1), |
| /// %struct.S { i32 42, i32 84 }, %struct.U* @e } |
| /// The %struct.S { i32 42, i32 84 } inner initializer is treated as a complex |
| /// constant expression, while the other two elements of @e are "simple". |
| static void BatchCommitValueTo(const DenseMap<Constant*, Constant*> &Mem) { |
| SmallVector<std::pair<GlobalVariable*, Constant*>, 32> GVs; |
| SmallVector<std::pair<ConstantExpr*, Constant*>, 32> ComplexCEs; |
| SmallVector<std::pair<ConstantExpr*, Constant*>, 32> SimpleCEs; |
| SimpleCEs.reserve(Mem.size()); |
| |
| for (const auto &I : Mem) { |
| if (auto *GV = dyn_cast<GlobalVariable>(I.first)) { |
| GVs.push_back(std::make_pair(GV, I.second)); |
| } else { |
| ConstantExpr *GEP = cast<ConstantExpr>(I.first); |
| // We don't handle the deeply recursive case using the batch method. |
| if (GEP->getNumOperands() > 3) |
| ComplexCEs.push_back(std::make_pair(GEP, I.second)); |
| else |
| SimpleCEs.push_back(std::make_pair(GEP, I.second)); |
| } |
| } |
| |
| // The algorithm below doesn't handle cases like nested structs, so use the |
| // slower fully general method if we have to. |
| for (auto ComplexCE : ComplexCEs) |
| CommitValueTo(ComplexCE.second, ComplexCE.first); |
| |
| for (auto GVPair : GVs) { |
| assert(GVPair.first->hasInitializer()); |
| GVPair.first->setInitializer(GVPair.second); |
| } |
| |
| if (SimpleCEs.empty()) |
| return; |
| |
| // We cache a single global's initializer elements in the case where the |
| // subsequent address/val pair uses the same one. This avoids throwing away and |
| // rebuilding the constant struct/vector/array just because one element is |
| // modified at a time. |
| SmallVector<Constant *, 32> Elts; |
| Elts.reserve(SimpleCEs.size()); |
| GlobalVariable *CurrentGV = nullptr; |
| |
| auto commitAndSetupCache = [&](GlobalVariable *GV, bool Update) { |
| Constant *Init = GV->getInitializer(); |
| Type *Ty = Init->getType(); |
| if (Update) { |
| if (CurrentGV) { |
| assert(CurrentGV && "Expected a GV to commit to!"); |
| Type *CurrentInitTy = CurrentGV->getInitializer()->getType(); |
| // We have a valid cache that needs to be committed. |
| if (StructType *STy = dyn_cast<StructType>(CurrentInitTy)) |
| CurrentGV->setInitializer(ConstantStruct::get(STy, Elts)); |
| else if (ArrayType *ArrTy = dyn_cast<ArrayType>(CurrentInitTy)) |
| CurrentGV->setInitializer(ConstantArray::get(ArrTy, Elts)); |
| else |
| CurrentGV->setInitializer(ConstantVector::get(Elts)); |
| } |
| if (CurrentGV == GV) |
| return; |
| // Need to clear and set up cache for new initializer. |
| CurrentGV = GV; |
| Elts.clear(); |
| unsigned NumElts; |
| if (auto *STy = dyn_cast<StructType>(Ty)) |
| NumElts = STy->getNumElements(); |
| else |
| NumElts = cast<SequentialType>(Ty)->getNumElements(); |
| for (unsigned i = 0, e = NumElts; i != e; ++i) |
| Elts.push_back(Init->getAggregateElement(i)); |
| } |
| }; |
| |
| for (auto CEPair : SimpleCEs) { |
| ConstantExpr *GEP = CEPair.first; |
| Constant *Val = CEPair.second; |
| |
| GlobalVariable *GV = cast<GlobalVariable>(GEP->getOperand(0)); |
| commitAndSetupCache(GV, GV != CurrentGV); |
| ConstantInt *CI = cast<ConstantInt>(GEP->getOperand(2)); |
| Elts[CI->getZExtValue()] = Val; |
| } |
| // The last initializer in the list needs to be committed, others |
| // will be committed on a new initializer being processed. |
| commitAndSetupCache(CurrentGV, true); |
| } |
| |
| /// Evaluate static constructors in the function, if we can. Return true if we |
| /// can, false otherwise. |
| static bool EvaluateStaticConstructor(Function *F, const DataLayout &DL, |
| TargetLibraryInfo *TLI) { |
| // Call the function. |
| Evaluator Eval(DL, TLI); |
| Constant *RetValDummy; |
| bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy, |
| SmallVector<Constant*, 0>()); |
| |
| if (EvalSuccess) { |
| ++NumCtorsEvaluated; |
| |
| // We succeeded at evaluation: commit the result. |
| LLVM_DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" |
| << F->getName() << "' to " |
| << Eval.getMutatedMemory().size() << " stores.\n"); |
| BatchCommitValueTo(Eval.getMutatedMemory()); |
| for (GlobalVariable *GV : Eval.getInvariants()) |
| GV->setConstant(true); |
| } |
| |
| return EvalSuccess; |
| } |
| |
| static int compareNames(Constant *const *A, Constant *const *B) { |
| Value *AStripped = (*A)->stripPointerCasts(); |
| Value *BStripped = (*B)->stripPointerCasts(); |
| return AStripped->getName().compare(BStripped->getName()); |
| } |
| |
| static void setUsedInitializer(GlobalVariable &V, |
| const SmallPtrSetImpl<GlobalValue *> &Init) { |
| if (Init.empty()) { |
| V.eraseFromParent(); |
| return; |
| } |
| |
| // Type of pointer to the array of pointers. |
| PointerType *Int8PtrTy = Type::getInt8PtrTy(V.getContext(), 0); |
| |
| SmallVector<Constant *, 8> UsedArray; |
| for (GlobalValue *GV : Init) { |
| Constant *Cast |
| = ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, Int8PtrTy); |
| UsedArray.push_back(Cast); |
| } |
| // Sort to get deterministic order. |
| array_pod_sort(UsedArray.begin(), UsedArray.end(), compareNames); |
| ArrayType *ATy = ArrayType::get(Int8PtrTy, UsedArray.size()); |
| |
| Module *M = V.getParent(); |
| V.removeFromParent(); |
| GlobalVariable *NV = |
| new GlobalVariable(*M, ATy, false, GlobalValue::AppendingLinkage, |
| ConstantArray::get(ATy, UsedArray), ""); |
| NV->takeName(&V); |
| NV->setSection("llvm.metadata"); |
| delete &V; |
| } |
| |
| namespace { |
| |
| /// An easy to access representation of llvm.used and llvm.compiler.used. |
| class LLVMUsed { |
| SmallPtrSet<GlobalValue *, 8> Used; |
| SmallPtrSet<GlobalValue *, 8> CompilerUsed; |
| GlobalVariable *UsedV; |
| GlobalVariable *CompilerUsedV; |
|