| //===- GlobalOpt.cpp - Optimize Global Variables --------------------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // 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. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "globalopt" |
| #include "llvm/Transforms/IPO.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/Analysis/ConstantFolding.h" |
| #include "llvm/Analysis/MemoryBuiltins.h" |
| #include "llvm/IR/CallingConv.h" |
| #include "llvm/IR/Constants.h" |
| #include "llvm/IR/DataLayout.h" |
| #include "llvm/IR/DerivedTypes.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/IR/Module.h" |
| #include "llvm/IR/Operator.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Support/CallSite.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetLibraryInfo.h" |
| #include <algorithm> |
| using namespace llvm; |
| |
| 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(NumFnDeleted , "Number of functions 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"); |
| |
| namespace { |
| struct GlobalStatus; |
| struct GlobalOpt : public ModulePass { |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<TargetLibraryInfo>(); |
| } |
| static char ID; // Pass identification, replacement for typeid |
| GlobalOpt() : ModulePass(ID) { |
| initializeGlobalOptPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| bool runOnModule(Module &M); |
| |
| private: |
| GlobalVariable *FindGlobalCtors(Module &M); |
| bool OptimizeFunctions(Module &M); |
| bool OptimizeGlobalVars(Module &M); |
| bool OptimizeGlobalAliases(Module &M); |
| bool OptimizeGlobalCtorsList(GlobalVariable *&GCL); |
| bool ProcessGlobal(GlobalVariable *GV,Module::global_iterator &GVI); |
| bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI, |
| const SmallPtrSet<const PHINode*, 16> &PHIUsers, |
| const GlobalStatus &GS); |
| bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn); |
| |
| DataLayout *TD; |
| TargetLibraryInfo *TLI; |
| }; |
| } |
| |
| char GlobalOpt::ID = 0; |
| INITIALIZE_PASS_BEGIN(GlobalOpt, "globalopt", |
| "Global Variable Optimizer", false, false) |
| INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo) |
| INITIALIZE_PASS_END(GlobalOpt, "globalopt", |
| "Global Variable Optimizer", false, false) |
| |
| ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); } |
| |
| namespace { |
| |
| /// GlobalStatus - As we analyze each global, keep track of some information |
| /// about it. If we find out that the address of the global is taken, none of |
| /// this info will be accurate. |
| struct GlobalStatus { |
| /// isCompared - True if the global's address is used in a comparison. |
| bool isCompared; |
| |
| /// isLoaded - True if the global is ever loaded. If the global isn't ever |
| /// loaded it can be deleted. |
| bool isLoaded; |
| |
| /// StoredType - Keep track of what stores to the global look like. |
| /// |
| enum StoredType { |
| /// NotStored - There is no store to this global. It can thus be marked |
| /// constant. |
| NotStored, |
| |
| /// isInitializerStored - This global is stored to, but the only thing |
| /// stored is the constant it was initialized with. This is only tracked |
| /// for scalar globals. |
| isInitializerStored, |
| |
| /// isStoredOnce - This global is stored to, but only its initializer and |
| /// one other value is ever stored to it. If this global isStoredOnce, we |
| /// track the value stored to it in StoredOnceValue below. This is only |
| /// tracked for scalar globals. |
| isStoredOnce, |
| |
| /// isStored - This global is stored to by multiple values or something else |
| /// that we cannot track. |
| isStored |
| } StoredType; |
| |
| /// StoredOnceValue - If only one value (besides the initializer constant) is |
| /// ever stored to this global, keep track of what value it is. |
| Value *StoredOnceValue; |
| |
| /// AccessingFunction/HasMultipleAccessingFunctions - These start out |
| /// null/false. When the first accessing function is noticed, it is recorded. |
| /// When a second different accessing function is noticed, |
| /// HasMultipleAccessingFunctions is set to true. |
| const Function *AccessingFunction; |
| bool HasMultipleAccessingFunctions; |
| |
| /// HasNonInstructionUser - Set to true if this global has a user that is not |
| /// an instruction (e.g. a constant expr or GV initializer). |
| bool HasNonInstructionUser; |
| |
| /// AtomicOrdering - Set to the strongest atomic ordering requirement. |
| AtomicOrdering Ordering; |
| |
| GlobalStatus() : isCompared(false), isLoaded(false), StoredType(NotStored), |
| StoredOnceValue(0), AccessingFunction(0), |
| HasMultipleAccessingFunctions(false), |
| HasNonInstructionUser(false), Ordering(NotAtomic) {} |
| }; |
| |
| } |
| |
| /// StrongerOrdering - Return the stronger of the two ordering. If the two |
| /// orderings are acquire and release, then return AcquireRelease. |
| /// |
| static AtomicOrdering StrongerOrdering(AtomicOrdering X, AtomicOrdering Y) { |
| if (X == Acquire && Y == Release) return AcquireRelease; |
| if (Y == Acquire && X == Release) return AcquireRelease; |
| return (AtomicOrdering)std::max(X, Y); |
| } |
| |
| /// SafeToDestroyConstant - It is safe to destroy a constant iff it is only used |
| /// by constants itself. Note that constants cannot be cyclic, so this test is |
| /// pretty easy to implement recursively. |
| /// |
| static bool SafeToDestroyConstant(const Constant *C) { |
| if (isa<GlobalValue>(C)) return false; |
| |
| for (Value::const_use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; |
| ++UI) |
| if (const Constant *CU = dyn_cast<Constant>(*UI)) { |
| if (!SafeToDestroyConstant(CU)) return false; |
| } else |
| return false; |
| return true; |
| } |
| |
| |
| /// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus |
| /// structure. If the global has its address taken, return true to indicate we |
| /// can't do anything with it. |
| /// |
| static bool AnalyzeGlobal(const Value *V, GlobalStatus &GS, |
| SmallPtrSet<const PHINode*, 16> &PHIUsers) { |
| for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; |
| ++UI) { |
| const User *U = *UI; |
| if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { |
| GS.HasNonInstructionUser = true; |
| |
| // If the result of the constantexpr isn't pointer type, then we won't |
| // know to expect it in various places. Just reject early. |
| if (!isa<PointerType>(CE->getType())) return true; |
| |
| if (AnalyzeGlobal(CE, GS, PHIUsers)) return true; |
| } else if (const Instruction *I = dyn_cast<Instruction>(U)) { |
| if (!GS.HasMultipleAccessingFunctions) { |
| const Function *F = I->getParent()->getParent(); |
| if (GS.AccessingFunction == 0) |
| GS.AccessingFunction = F; |
| else if (GS.AccessingFunction != F) |
| GS.HasMultipleAccessingFunctions = true; |
| } |
| if (const LoadInst *LI = dyn_cast<LoadInst>(I)) { |
| GS.isLoaded = true; |
| // Don't hack on volatile loads. |
| if (LI->isVolatile()) return true; |
| GS.Ordering = StrongerOrdering(GS.Ordering, LI->getOrdering()); |
| } else if (const StoreInst *SI = dyn_cast<StoreInst>(I)) { |
| // Don't allow a store OF the address, only stores TO the address. |
| if (SI->getOperand(0) == V) return true; |
| |
| // Don't hack on volatile stores. |
| if (SI->isVolatile()) return true; |
| |
| GS.Ordering = StrongerOrdering(GS.Ordering, SI->getOrdering()); |
| |
| // If this is a direct store to the global (i.e., the global is a scalar |
| // value, not an aggregate), keep more specific information about |
| // stores. |
| if (GS.StoredType != GlobalStatus::isStored) { |
| if (const GlobalVariable *GV = dyn_cast<GlobalVariable>( |
| SI->getOperand(1))) { |
| Value *StoredVal = SI->getOperand(0); |
| |
| if (Constant *C = dyn_cast<Constant>(StoredVal)) { |
| if (C->isThreadDependent()) { |
| // The stored value changes between threads; don't track it. |
| return true; |
| } |
| } |
| |
| if (StoredVal == GV->getInitializer()) { |
| if (GS.StoredType < GlobalStatus::isInitializerStored) |
| GS.StoredType = GlobalStatus::isInitializerStored; |
| } else if (isa<LoadInst>(StoredVal) && |
| cast<LoadInst>(StoredVal)->getOperand(0) == GV) { |
| if (GS.StoredType < GlobalStatus::isInitializerStored) |
| GS.StoredType = GlobalStatus::isInitializerStored; |
| } else if (GS.StoredType < GlobalStatus::isStoredOnce) { |
| GS.StoredType = GlobalStatus::isStoredOnce; |
| GS.StoredOnceValue = StoredVal; |
| } else if (GS.StoredType == GlobalStatus::isStoredOnce && |
| GS.StoredOnceValue == StoredVal) { |
| // noop. |
| } else { |
| GS.StoredType = GlobalStatus::isStored; |
| } |
| } else { |
| GS.StoredType = GlobalStatus::isStored; |
| } |
| } |
| } else if (isa<BitCastInst>(I)) { |
| if (AnalyzeGlobal(I, GS, PHIUsers)) return true; |
| } else if (isa<GetElementPtrInst>(I)) { |
| if (AnalyzeGlobal(I, GS, PHIUsers)) return true; |
| } else if (isa<SelectInst>(I)) { |
| if (AnalyzeGlobal(I, GS, PHIUsers)) return true; |
| } else if (const PHINode *PN = dyn_cast<PHINode>(I)) { |
| // PHI nodes we can check just like select or GEP instructions, but we |
| // have to be careful about infinite recursion. |
| if (PHIUsers.insert(PN)) // Not already visited. |
| if (AnalyzeGlobal(I, GS, PHIUsers)) return true; |
| } else if (isa<CmpInst>(I)) { |
| GS.isCompared = true; |
| } else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) { |
| if (MTI->isVolatile()) return true; |
| if (MTI->getArgOperand(0) == V) |
| GS.StoredType = GlobalStatus::isStored; |
| if (MTI->getArgOperand(1) == V) |
| GS.isLoaded = true; |
| } else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) { |
| assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!"); |
| if (MSI->isVolatile()) return true; |
| GS.StoredType = GlobalStatus::isStored; |
| } else { |
| return true; // Any other non-load instruction might take address! |
| } |
| } else if (const Constant *C = dyn_cast<Constant>(U)) { |
| GS.HasNonInstructionUser = true; |
| // We might have a dead and dangling constant hanging off of here. |
| if (!SafeToDestroyConstant(C)) |
| return true; |
| } else { |
| GS.HasNonInstructionUser = true; |
| // Otherwise must be some other user. |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| /// isLeakCheckerRoot - 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(cast<PointerType>(GV->getType())->getElementType()); |
| |
| 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, const TargetLibraryInfo *TLI) { |
| 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, TLI)) |
| 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 (1); |
| } |
| |
| /// CleanupPointerRootUsers - 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, |
| const TargetLibraryInfo *TLI) { |
| // 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::use_iterator UI = GV->use_begin(), E = GV->use_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 (SafeToDestroyConstant(C)) { |
| C->destroyConstant(); |
| // This could have invalidated UI, start over from scratch. |
| Dead.clear(); |
| CleanupPointerRootUsers(GV, TLI); |
| return true; |
| } |
| } |
| } |
| |
| for (int i = 0, e = Dead.size(); i != e; ++i) { |
| if (IsSafeComputationToRemove(Dead[i].first, TLI)) { |
| Dead[i].second->eraseFromParent(); |
| Instruction *I = Dead[i].first; |
| do { |
| if (isAllocationFn(I, TLI)) |
| break; |
| Instruction *J = dyn_cast<Instruction>(I->getOperand(0)); |
| if (!J) |
| break; |
| I->eraseFromParent(); |
| I = J; |
| } while (1); |
| I->eraseFromParent(); |
| } |
| } |
| |
| return Changed; |
| } |
| |
| /// CleanupConstantGlobalUsers - 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, |
| DataLayout *TD, TargetLibraryInfo *TLI) { |
| bool Changed = false; |
| for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) { |
| User *U = *UI++; |
| |
| 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 = 0; |
| if (Init) |
| SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); |
| Changed |= CleanupConstantGlobalUsers(CE, SubInit, TD, TLI); |
| } else if (CE->getOpcode() == Instruction::BitCast && |
| CE->getType()->isPointerTy()) { |
| // Pointer cast, delete any stores and memsets to the global. |
| Changed |= CleanupConstantGlobalUsers(CE, 0, TD, TLI); |
| } |
| |
| 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 = 0; |
| if (!isa<ConstantExpr>(GEP->getOperand(0))) { |
| ConstantExpr *CE = |
| dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP, TD, TLI)); |
| 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->getType()->getElementType()); |
| } |
| Changed |= CleanupConstantGlobalUsers(GEP, SubInit, TD, TLI); |
| |
| 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 (SafeToDestroyConstant(C)) { |
| C->destroyConstant(); |
| // This could have invalidated UI, start over from scratch. |
| CleanupConstantGlobalUsers(V, Init, TD, TLI); |
| return true; |
| } |
| } |
| } |
| return Changed; |
| } |
| |
| /// isSafeSROAElementUse - 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 SafeToDestroyConstant(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. |
| GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I); |
| if (GEPI == 0) return false; |
| |
| if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) || |
| !cast<Constant>(GEPI->getOperand(1))->isNullValue()) |
| return false; |
| |
| for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end(); |
| I != E; ++I) |
| if (!isSafeSROAElementUse(*I)) |
| return false; |
| return true; |
| } |
| |
| |
| /// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value. |
| /// Look at it and its uses and decide whether it is safe to SROA this global. |
| /// |
| static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) { |
| // 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 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() || |
| !isa<ConstantInt>(U->getOperand(2))) |
| return false; |
| |
| gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U); |
| ++GEPI; // Skip over the pointer index. |
| |
| // If this is a use of an array allocation, do a bit more checking for sanity. |
| if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) { |
| uint64_t NumElements = AT->getNumElements(); |
| ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2)); |
| |
| // Check to make sure that index falls within the array. If not, |
| // something funny is going on, so we won't do the optimization. |
| // |
| if (Idx->getZExtValue() >= NumElements) |
| return false; |
| |
| // We cannot scalar repl this level of the array unless any array |
| // sub-indices are in-range constants. 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]. |
| // |
| // Scalar replacing *just* the outer index of the array is probably not |
| // going to be a win anyway, so just give up. |
| for (++GEPI; // Skip array index. |
| GEPI != E; |
| ++GEPI) { |
| uint64_t NumElements; |
| if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI)) |
| NumElements = SubArrayTy->getNumElements(); |
| else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI)) |
| NumElements = SubVectorTy->getNumElements(); |
| else { |
| assert((*GEPI)->isStructTy() && |
| "Indexed GEP type is not array, vector, or struct!"); |
| continue; |
| } |
| |
| ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand()); |
| if (!IdxVal || IdxVal->getZExtValue() >= NumElements) |
| return false; |
| } |
| } |
| |
| for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I) |
| if (!isSafeSROAElementUse(*I)) |
| return false; |
| return true; |
| } |
| |
| /// GlobalUsersSafeToSRA - 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 (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); |
| UI != E; ++UI) { |
| if (!IsUserOfGlobalSafeForSRA(*UI, GV)) |
| return false; |
| } |
| return true; |
| } |
| |
| |
| /// SRAGlobal - 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 &TD) { |
| // Make sure this global only has simple uses that we can SRA. |
| if (!GlobalUsersSafeToSRA(GV)) |
| return 0; |
| |
| assert(GV->hasLocalLinkage() && !GV->isConstant()); |
| 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 = TD.getABITypeAlignment(GV->getType()); |
| |
| if (StructType *STy = dyn_cast<StructType>(Ty)) { |
| NewGlobals.reserve(STy->getNumElements()); |
| const StructLayout &Layout = *TD.getStructLayout(STy); |
| for (unsigned i = 0, e = STy->getNumElements(); 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()); |
| Globals.insert(GV, 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); |
| unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset); |
| if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i))) |
| NGV->setAlignment(NewAlign); |
| } |
| } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) { |
| unsigned NumElements = 0; |
| if (ArrayType *ATy = dyn_cast<ArrayType>(STy)) |
| NumElements = ATy->getNumElements(); |
| else |
| NumElements = cast<VectorType>(STy)->getNumElements(); |
| |
| if (NumElements > 16 && GV->hasNUsesOrMore(16)) |
| return 0; // It's not worth it. |
| NewGlobals.reserve(NumElements); |
| |
| uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType()); |
| unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType()); |
| 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()); |
| Globals.insert(GV, 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. |
| unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i); |
| if (NewAlign > EltAlign) |
| NGV->setAlignment(NewAlign); |
| } |
| } |
| |
| if (NewGlobals.empty()) |
| return 0; |
| |
| DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV); |
| |
| 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->use_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]; |
| |
| // 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(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(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] : 0; |
| } |
| |
| /// AllUsesOfValueWillTrapIfNull - 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, |
| SmallPtrSet<const PHINode*, 8> &PHIs) { |
| for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; |
| ++UI) { |
| const User *U = *UI; |
| |
| 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) && !AllUsesOfValueWillTrapIfNull(PN, PHIs)) |
| return false; |
| } else if (isa<ICmpInst>(U) && |
| isa<ConstantPointerNull>(UI->getOperand(1))) { |
| // Ignore icmp X, null |
| } else { |
| //cerr << "NONTRAPPING USE: " << *U; |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| /// AllUsesOfLoadedValueWillTrapIfNull - 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 (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end(); |
| UI != E; ++UI) { |
| const User *U = *UI; |
| |
| 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 (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) { |
| Instruction *I = cast<Instruction>(*UI++); |
| 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->use_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(NewV, Idxs)); |
| if (GEPI->use_empty()) { |
| Changed = true; |
| GEPI->eraseFromParent(); |
| } |
| } |
| } |
| |
| return Changed; |
| } |
| |
| |
| /// OptimizeAwayTrappingUsesOfLoads - 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, |
| DataLayout *TD, |
| TargetLibraryInfo *TLI) { |
| 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::use_iterator GUI = GV->use_begin(), E = GV->use_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) { |
| DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV); |
| ++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, TLI); |
| } else { |
| Changed = true; |
| CleanupConstantGlobalUsers(GV, 0, TD, TLI); |
| } |
| if (GV->use_empty()) { |
| DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n"); |
| Changed = true; |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| } |
| } |
| return Changed; |
| } |
| |
| /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the |
| /// instructions that are foldable. |
| static void ConstantPropUsersOf(Value *V, |
| DataLayout *TD, TargetLibraryInfo *TLI) { |
| for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) |
| if (Instruction *I = dyn_cast<Instruction>(*UI++)) |
| if (Constant *NewC = ConstantFoldInstruction(I, TD, 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; |
| I->eraseFromParent(); |
| } |
| } |
| |
| /// OptimizeGlobalAddressOfMalloc - 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, |
| DataLayout *TD, |
| TargetLibraryInfo *TLI) { |
| 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", |
| GV, |
| 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 = 0; |
| while (!CI->use_empty()) { |
| Instruction *User = cast<Instruction>(CI->use_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 == 0) |
| TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI); |
| User->replaceUsesOfWith(CI, TheBC); |
| } |
| } |
| |
| Constant *RepValue = NewGV; |
| if (NewGV->getType() != GV->getType()->getElementType()) |
| RepValue = ConstantExpr::getBitCast(RepValue, |
| GV->getType()->getElementType()); |
| |
| // 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->use_back())) { |
| // The global is initialized when the store to it occurs. |
| new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, 0, |
| SI->getOrdering(), SI->getSynchScope(), SI); |
| SI->eraseFromParent(); |
| continue; |
| } |
| |
| LoadInst *LI = cast<LoadInst>(GV->use_back()); |
| while (!LI->use_empty()) { |
| Use &LoadUse = LI->use_begin().getUse(); |
| if (!isa<ICmpInst>(LoadUse.getUser())) { |
| LoadUse = RepValue; |
| continue; |
| } |
| |
| ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser()); |
| // 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, InitBool->getName()+".val", false, 0, |
| LI->getOrdering(), LI->getSynchScope(), |
| 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->use_back())->eraseFromParent(); |
| delete InitBool; |
| } else |
| GV->getParent()->getGlobalList().insert(GV, 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, TD, TLI); |
| if (RepValue != NewGV) |
| ConstantPropUsersOf(RepValue, TD, TLI); |
| |
| return NewGV; |
| } |
| |
| /// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - 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, |
| SmallPtrSet<const PHINode*, 8> &PHIs) { |
| for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); |
| UI != E; ++UI) { |
| const Instruction *Inst = cast<Instruction>(*UI); |
| |
| 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)) |
| 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; |
| } |
| |
| /// ReplaceUsesOfMallocWithGlobal - 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->use_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->use_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, GV->getName()+".val", InsertPt); |
| U->replaceUsesOfWith(Alloc, NL); |
| } |
| } |
| |
| /// LoadUsesSimpleEnoughForHeapSRA - 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, |
| SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs, |
| SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) { |
| // We permit two users of the load: setcc comparing against the null |
| // pointer, and a getelementptr of a specific form. |
| for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; |
| ++UI) { |
| const Instruction *User = cast<Instruction>(*UI); |
| |
| // Comparison against null is ok. |
| if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) { |
| 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>(User)) { |
| // 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>(User)) { |
| if (!LoadUsingPHIsPerLoad.insert(PN)) |
| // This means some phi nodes are dependent on each other. |
| // Avoid infinite looping! |
| return false; |
| if (!LoadUsingPHIs.insert(PN)) |
| // 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; |
| } |
| |
| |
| /// AllGlobalLoadUsesSimpleEnoughForHeapSRA - 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 (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end(); |
| UI != E; ++UI) |
| if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) { |
| 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 (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin() |
| , E = LoadUsingPHIs.end(); I != E; ++I) { |
| const PHINode *PN = *I; |
| 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. |
| Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo, |
| InsertedScalarizedValues, |
| PHIsToRewrite), |
| LI->getName()+".f"+Twine(FieldNo), LI); |
| } else if (PHINode *PN = dyn_cast<PHINode>(V)) { |
| // PN's type is pointer to struct. Make a new PHI of pointer to struct |
| // field. |
| StructType *ST = |
| cast<StructType>(cast<PointerType>(PN->getType())->getElementType()); |
| |
| PHINode *NewPN = |
| PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)), |
| PN->getNumIncomingValues(), |
| PN->getName()+".f"+Twine(FieldNo), PN); |
| Result = NewPN; |
| PHIsToRewrite.push_back(std::make_pair(PN, FieldNo)); |
| } else { |
| llvm_unreachable("Unknown usable value"); |
| } |
| |
| return FieldVals[FieldNo] = Result; |
| } |
| |
| /// RewriteHeapSROALoadUser - 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(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 (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) { |
| Instruction *User = cast<Instruction>(*UI++); |
| RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite); |
| } |
| } |
| |
| /// RewriteUsesOfLoadForHeapSRoA - 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 (Value::use_iterator UI = Load->use_begin(), E = Load->use_end(); |
| UI != E; ) { |
| Instruction *User = cast<Instruction>(*UI++); |
| RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite); |
| } |
| |
| if (Load->use_empty()) { |
| Load->eraseFromParent(); |
| InsertedScalarizedValues.erase(Load); |
| } |
| } |
| |
| /// PerformHeapAllocSRoA - 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, DataLayout *TD, |
| const TargetLibraryInfo *TLI) { |
| 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; |
| |
| for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ |
| Type *FieldTy = STy->getElementType(FieldNo); |
| PointerType *PFieldTy = PointerType::getUnqual(FieldTy); |
| |
| GlobalVariable *NGV = |
| new GlobalVariable(*GV->getParent(), |
| PFieldTy, false, GlobalValue::InternalLinkage, |
| Constant::getNullValue(PFieldTy), |
| GV->getName() + ".f" + Twine(FieldNo), GV, |
| GV->getThreadLocalMode()); |
| FieldGlobals.push_back(NGV); |
| |
| unsigned TypeSize = TD->getTypeAllocSize(FieldTy); |
| if (StructType *ST = dyn_cast<StructType>(FieldTy)) |
| TypeSize = TD->getStructLayout(ST)->getSizeInBytes(); |
| Type *IntPtrTy = TD->getIntPtrType(CI->getContext()); |
| Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy, |
| ConstantInt::get(IntPtrTy, TypeSize), |
| NElems, 0, |
| 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, "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(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, 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(); |
| |
| /// InsertedScalarizedLoads - 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 (Value::use_iterator UI = GV->use_begin(), E = GV->use_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) { |
| PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType()); |
| Constant *Null = Constant::getNullValue(PT->getElementType()); |
| 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]); |
| } |
| |
| /// TryToOptimizeStoreOfMallocToGlobal - 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, |
| Module::global_iterator &GVI, |
| DataLayout *TD, |
| TargetLibraryInfo *TLI) { |
| if (!TD) |
| return false; |
| |
| // 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, TD, 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() * TD->getTypeAllocSize(AllocTy) < 2048) { |
| GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD, 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 != 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 = TD->getIntPtrType(CI->getContext()); |
| unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes(); |
| Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize); |
| Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements()); |
| Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy, |
| AllocSize, NumElements, |
| 0, 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); |
| } |
| |
| GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, TLI, true), |
| TD, TLI); |
| return true; |
| } |
| |
| return false; |
| } |
| |
| // OptimizeOnceStoredGlobal - 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, |
| Module::global_iterator &GVI, |
| DataLayout *TD, TargetLibraryInfo *TLI) { |
| // 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()) { |
| 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, TD, TLI)) |
| return true; |
| } else if (CallInst *CI = extractMallocCall(StoredOnceVal, TLI)) { |
| Type *MallocType = getMallocAllocatedType(CI, TLI); |
| if (MallocType && |
| TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, Ordering, GVI, |
| TD, TLI)) |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| /// TryToShrinkGlobalToBoolean - 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->getType()->getElementType(); |
| |
| // 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 (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){ |
| User *U = *I; |
| if (!isa<LoadInst>(U) && !isa<StoreInst>(U)) |
| return false; |
| } |
| |
| DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV); |
| |
| // 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()); |
| GV->getParent()->getGlobalList().insert(GV, NewGV); |
| |
| Constant *InitVal = GV->getInitializer(); |
| assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) && |
| "No reason to shrink to bool!"); |
| |
| // 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; |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) |
| IsOneZero = InitVal->isNullValue() && CI->isOne(); |
| |
| while (!GV->use_empty()) { |
| Instruction *UI = cast<Instruction>(GV->use_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, LI->getName()+".b", false, 0, |
| LI->getOrdering(), LI->getSynchScope(), 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!"); |
| } |
| } |
| new StoreInst(StoreVal, NewGV, false, 0, |
| SI->getOrdering(), SI->getSynchScope(), SI); |
| } else { |
| // Change the load into a load of bool then a select. |
| LoadInst *LI = cast<LoadInst>(UI); |
| LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", false, 0, |
| LI->getOrdering(), LI->getSynchScope(), LI); |
| Value *NSI; |
| if (IsOneZero) |
| NSI = new ZExtInst(NLI, LI->getType(), "", LI); |
| else |
| NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI); |
| NSI->takeName(LI); |
| LI->replaceAllUsesWith(NSI); |
| } |
| UI->eraseFromParent(); |
| } |
| |
| GV->eraseFromParent(); |
| return true; |
| } |
| |
| |
| /// ProcessGlobal - Analyze the specified global variable and optimize it if |
| /// possible. If we make a change, return true. |
| bool GlobalOpt::ProcessGlobal(GlobalVariable *GV, |
| Module::global_iterator &GVI) { |
| if (!GV->isDiscardableIfUnused()) |
| return false; |
| |
| // Do more involved optimizations if the global is internal. |
| GV->removeDeadConstantUsers(); |
| |
| if (GV->use_empty()) { |
| DEBUG(dbgs() << "GLOBAL DEAD: " << *GV); |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| return true; |
| } |
| |
| if (!GV->hasLocalLinkage()) |
| return false; |
| |
| SmallPtrSet<const PHINode*, 16> PHIUsers; |
| GlobalStatus GS; |
| |
| if (AnalyzeGlobal(GV, GS, PHIUsers)) |
| return false; |
| |
| if (!GS.isCompared && !GV->hasUnnamedAddr()) { |
| GV->setUnnamedAddr(true); |
| NumUnnamed++; |
| } |
| |
| if (GV->isConstant() || !GV->hasInitializer()) |
| return false; |
| |
| return ProcessInternalGlobal(GV, GVI, PHIUsers, GS); |
| } |
| |
| /// ProcessInternalGlobal - Analyze the specified global variable and optimize |
| /// it if possible. If we make a change, return true. |
| bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV, |
| Module::global_iterator &GVI, |
| const SmallPtrSet<const PHINode*, 16> &PHIUsers, |
| const GlobalStatus &GS) { |
| // If this is a first class global and has only one accessing function |
| // and this function is main (which we know is not recursive we can make |
| // this global a local variable) 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 && !GS.HasNonInstructionUser && |
| GV->getType()->getElementType()->isSingleValueType() && |
| GS.AccessingFunction->getName() == "main" && |
| GS.AccessingFunction->hasExternalLinkage() && |
| GV->getType()->getAddressSpace() == 0) { |
| DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV); |
| Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction |
| ->getEntryBlock().begin()); |
| Type *ElemTy = GV->getType()->getElementType(); |
| // FIXME: Pass Global's alignment when globals have alignment |
| AllocaInst *Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), &FirstI); |
| if (!isa<UndefValue>(GV->getInitializer())) |
| new StoreInst(GV->getInitializer(), Alloca, &FirstI); |
| |
| 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) { |
| DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV); |
| |
| bool Changed; |
| if (isLeakCheckerRoot(GV)) { |
| // Delete any constant stores to the global. |
| Changed = CleanupPointerRootUsers(GV, TLI); |
| } 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(), TD, TLI); |
| } |
| |
| // If the global is dead now, delete it. |
| if (GV->use_empty()) { |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| Changed = true; |
| } |
| return Changed; |
| |
| } else if (GS.StoredType <= GlobalStatus::isInitializerStored) { |
| DEBUG(dbgs() << "MARKING CONSTANT: " << *GV << "\n"); |
| GV->setConstant(true); |
| |
| // Clean up any obviously simplifiable users now. |
| CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI); |
| |
| // If the global is dead now, just nuke it. |
| if (GV->use_empty()) { |
| DEBUG(dbgs() << " *** Marking constant allowed us to simplify " |
| << "all users and delete global!\n"); |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| } |
| |
| ++NumMarked; |
| return true; |
| } else if (!GV->getInitializer()->getType()->isSingleValueType()) { |
| if (DataLayout *TD = getAnalysisIfAvailable<DataLayout>()) |
| if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) { |
| GVI = FirstNewGV; // Don't skip the newly produced globals! |
| return true; |
| } |
| } else if (GS.StoredType == GlobalStatus::isStoredOnce) { |
| // 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(), TD, TLI); |
| |
| if (GV->use_empty()) { |
| DEBUG(dbgs() << " *** Substituting initializer allowed us to " |
| << "simplify all users and delete global!\n"); |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| } else { |
| GVI = GV; |
| } |
| ++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, GVI, |
| TD, TLI)) |
| 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 (TryToShrinkGlobalToBoolean(GV, SOVConstant)) { |
| ++NumShrunkToBool; |
| return true; |
| } |
| } |
| |
| return false; |
| } |
| |
| /// ChangeCalleesToFastCall - Walk all of the direct calls of the specified |
| /// function, changing them to FastCC. |
| static void ChangeCalleesToFastCall(Function *F) { |
| for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ |
| if (isa<BlockAddress>(*UI)) |
| continue; |
| CallSite User(cast<Instruction>(*UI)); |
| User.setCallingConv(CallingConv::Fast); |
| } |
| } |
| |
| static AttributeSet StripNest(LLVMContext &C, const AttributeSet &Attrs) { |
| for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) { |
| unsigned Index = Attrs.getSlotIndex(i); |
| if (!Attrs.getSlotAttributes(i).hasAttribute(Index, Attribute::Nest)) |
| continue; |
| |
| // There can be only one. |
| return Attrs.removeAttribute(C, Index, Attribute::Nest); |
| } |
| |
| return Attrs; |
| } |
| |
| static void RemoveNestAttribute(Function *F) { |
| F->setAttributes(StripNest(F->getContext(), F->getAttributes())); |
| for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ |
| if (isa<BlockAddress>(*UI)) |
| continue; |
| CallSite User(cast<Instruction>(*UI)); |
| User.setAttributes(StripNest(F->getContext(), User.getAttributes())); |
| } |
| } |
| |
| bool GlobalOpt::OptimizeFunctions(Module &M) { |
| bool Changed = false; |
| // Optimize functions. |
| for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) { |
| Function *F = FI++; |
| // Functions without names cannot be referenced outside this module. |
| if (!F->hasName() && !F->isDeclaration()) |
| F->setLinkage(GlobalValue::InternalLinkage); |
| F->removeDeadConstantUsers(); |
| if (F->isDefTriviallyDead()) { |
| F->eraseFromParent(); |
| Changed = true; |
| ++NumFnDeleted; |
| } else if (F->hasLocalLinkage()) { |
| if (F->getCallingConv() == CallingConv::C && !F->isVarArg() && |
| !F->hasAddressTaken()) { |
| // If this function has C calling conventions, 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. |
| RemoveNestAttribute(F); |
| ++NumNestRemoved; |
| Changed = true; |
| } |
| } |
| } |
| return Changed; |
| } |
| |
| bool GlobalOpt::OptimizeGlobalVars(Module &M) { |
| 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->setLinkage(GlobalValue::InternalLinkage); |
| // Simplify the initializer. |
| if (GV->hasInitializer()) |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) { |
| Constant *New = ConstantFoldConstantExpression(CE, TD, TLI); |
| if (New && New != CE) |
| GV->setInitializer(New); |
| } |
| |
| Changed |= ProcessGlobal(GV, GVI); |
| } |
| return Changed; |
| } |
| |
| /// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all |
| /// initializers have an init priority of 65535. |
| GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) { |
| GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors"); |
| if (GV == 0) return 0; |
| |
| // Verify that the initializer is simple enough for us to handle. We are |
| // only allowed to optimize the initializer if it is unique. |
| if (!GV->hasUniqueInitializer()) return 0; |
| |
| if (isa<ConstantAggregateZero>(GV->getInitializer())) |
| return GV; |
| ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); |
| |
| for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) { |
| if (isa<ConstantAggregateZero>(*i)) |
| continue; |
| ConstantStruct *CS = cast<ConstantStruct>(*i); |
| if (isa<ConstantPointerNull>(CS->getOperand(1))) |
| continue; |
| |
| // Must have a function or null ptr. |
| if (!isa<Function>(CS->getOperand(1))) |
| return 0; |
| |
| // Init priority must be standard. |
| ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0)); |
| if (CI->getZExtValue() != 65535) |
| return 0; |
| } |
| |
| return GV; |
| } |
| |
| /// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand, |
| /// return a list of the functions and null terminator as a vector. |
| static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) { |
| if (GV->getInitializer()->isNullValue()) |
| return std::vector<Function*>(); |
| ConstantArray *CA = cast<ConstantArray>(GV->getInitializer()); |
| std::vector<Function*> Result; |
| Result.reserve(CA->getNumOperands()); |
| for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) { |
| ConstantStruct *CS = cast<ConstantStruct>(*i); |
| Result.push_back(dyn_cast<Function>(CS->getOperand(1))); |
| } |
| return Result; |
| } |
| |
| /// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the |
| /// specified array, returning the new global to use. |
| static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL, |
| const std::vector<Function*> &Ctors) { |
| // If we made a change, reassemble the initializer list. |
| Constant *CSVals[2]; |
| CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535); |
| CSVals[1] = 0; |
| |
| StructType *StructTy = |
| cast <StructType>( |
| cast<ArrayType>(GCL->getType()->getElementType())->getElementType()); |
| |
| // Create the new init list. |
| std::vector<Constant*> CAList; |
| for (unsigned i = 0, e = Ctors.size(); i != e; ++i) { |
| if (Ctors[i]) { |
| CSVals[1] = Ctors[i]; |
| } else { |
| Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()), |
| false); |
| PointerType *PFTy = PointerType::getUnqual(FTy); |
| CSVals[1] = Constant::getNullValue(PFTy); |
| CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), |
| 0x7fffffff); |
| } |
| CAList.push_back(ConstantStruct::get(StructTy, CSVals)); |
| } |
| |
| // Create the array initializer. |
| Constant *CA = ConstantArray::get(ArrayType::get(StructTy, |
| CAList.size()), CAList); |
| |
| // If we didn't change the number of elements, don't create a new GV. |
| if (CA->getType() == GCL->getInitializer()->getType()) { |
| GCL->setInitializer(CA); |
| return GCL; |
| } |
| |
| // Create the new global and insert it next to the existing list. |
| GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(), |
| GCL->getLinkage(), CA, "", |
| GCL->getThreadLocalMode()); |
| GCL->getParent()->getGlobalList().insert(GCL, NGV); |
| NGV->takeName(GCL); |
| |
| // Nuke the old list, replacing any uses with the new one. |
| if (!GCL->use_empty()) { |
| Constant *V = NGV; |
| if (V->getType() != GCL->getType()) |
| V = ConstantExpr::getBitCast(V, GCL->getType()); |
| GCL->replaceAllUsesWith(V); |
| } |
| GCL->eraseFromParent(); |
| |
| if (Ctors.size()) |
| return NGV; |
| else |
| return 0; |
| } |
| |
| |
| static inline bool |
| isSimpleEnoughValueToCommit(Constant *C, |
| SmallPtrSet<Constant*, 8> &SimpleConstants, |
| const DataLayout *TD); |
| |
| |
| /// isSimpleEnoughValueToCommit - Return true if the specified constant can be |
| /// handled by the code generator. We don't want to generate something like: |
| /// void *X = &X/42; |
| /// because the code generator doesn't have a relocation that can handle that. |
| /// |
| /// This function should be called if C was not found (but just got inserted) |
| /// in SimpleConstants to avoid having to rescan the same constants all the |
| /// time. |
| static bool isSimpleEnoughValueToCommitHelper(Constant *C, |
| SmallPtrSet<Constant*, 8> &SimpleConstants, |
| const DataLayout *TD) { |
| // Simple integer, undef, constant aggregate zero, global addresses, etc are |
| // all supported. |
| if (C->getNumOperands() == 0 || isa<BlockAddress>(C) || |
| isa<GlobalValue>(C)) |
| return true; |
| |
| // Aggregate values are safe if all their elements are. |
| if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) || |
| isa<ConstantVector>(C)) { |
| for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) { |
| Constant *Op = cast<Constant>(C->getOperand(i)); |
| if (!isSimpleEnoughValueToCommit(Op, SimpleConstants, TD)) |
| return false; |
| } |
| return true; |
| } |
| |
| // We don't know exactly what relocations are allowed in constant expressions, |
| // so we allow &global+constantoffset, which is safe and uniformly supported |
| // across targets. |
| ConstantExpr *CE = cast<ConstantExpr>(C); |
| switch (CE->getOpcode()) { |
| case Instruction::BitCast: |
| // Bitcast is fine if the casted value is fine. |
| return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); |
| |
| case Instruction::IntToPtr: |
| case Instruction::PtrToInt: |
| // int <=> ptr is fine if the int type is the same size as the |
| // pointer type. |
| if (!TD || TD->getTypeSizeInBits(CE->getType()) != |
| TD->getTypeSizeInBits(CE->getOperand(0)->getType())) |
| return false; |
| return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); |
| |
| // GEP is fine if it is simple + constant offset. |
| case Instruction::GetElementPtr: |
| for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i) |
| if (!isa<ConstantInt>(CE->getOperand(i))) |
| return false; |
| return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); |
| |
| case Instruction::Add: |
| // We allow simple+cst. |
| if (!isa<ConstantInt>(CE->getOperand(1))) |
| return false; |
| return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD); |
| } |
| return false; |
| } |
| |
| static inline bool |
| isSimpleEnoughValueToCommit(Constant *C, |
| SmallPtrSet<Constant*, 8> &SimpleConstants, |
| const DataLayout *TD) { |
| // If we already checked this constant, we win. |
| if (!SimpleConstants.insert(C)) return true; |
| // Check the constant. |
| return isSimpleEnoughValueToCommitHelper(C, SimpleConstants, TD); |
| } |
| |
| |
| /// isSimpleEnoughPointerToCommit - Return true if this constant is simple |
| /// enough for us to understand. In particular, if it is a cast to anything |
| /// other than from one pointer type to another pointer type, we punt. |
| /// We basically just support direct accesses to globals and GEP's of |
| /// globals. This should be kept up to date with CommitValueTo. |
| static bool isSimpleEnoughPointerToCommit(Constant *C) { |
| // Conservatively, avoid aggregate types. This is because we don't |
| // want to worry about them partially overlapping other stores. |
| if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType()) |
| return false; |
| |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) |
| // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or |
| // external globals. |
| return GV->hasUniqueInitializer(); |
| |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) { |
| // Handle a constantexpr gep. |
| if (CE->getOpcode() == Instruction::GetElementPtr && |
| isa<GlobalVariable>(CE->getOperand(0)) && |
| cast<GEPOperator>(CE)->isInBounds()) { |
| GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); |
| // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or |
| // external globals. |
| if (!GV->hasUniqueInitializer()) |
| return false; |
| |
| // The first index must be zero. |
| ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin())); |
| if (!CI || !CI->isZero()) return false; |
| |
| // The remaining indices must be compile-time known integers within the |
| // notional bounds of the corresponding static array types. |
| if (!CE->isGEPWithNoNotionalOverIndexing()) |
| return false; |
| |
| return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); |
| |
| // A constantexpr bitcast from a pointer to another pointer is a no-op, |
| // and we know how to evaluate it by moving the bitcast from the pointer |
| // operand to the value operand. |
| } else if (CE->getOpcode() == Instruction::BitCast && |
| isa<GlobalVariable>(CE->getOperand(0))) { |
| // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or |
| // external globals. |
| return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer(); |
| } |
| } |
| |
| return false; |
| } |
| |
| /// EvaluateStoreInto - 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; |
| if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy)) |
| NumElts = ATy->getNumElements(); |
| else |
| NumElts = InitTy->getVectorNumElements(); |
| |
| // 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); |
| } |
| |
| /// CommitValueTo - 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)); |
| } |
| |
| namespace { |
| |
| /// Evaluator - This class evaluates LLVM IR, producing the Constant |
| /// representing each SSA instruction. Changes to global variables are stored |
| /// in a mapping that can be iterated over after the evaluation is complete. |
| /// Once an evaluation call fails, the evaluation object should not be reused. |
| class Evaluator { |
| public: |
| Evaluator(const DataLayout *TD, const TargetLibraryInfo *TLI) |
| : TD(TD), TLI(TLI) { |
| ValueStack.push_back(new DenseMap<Value*, Constant*>); |
| } |
| |
| ~Evaluator() { |
| DeleteContainerPointers(ValueStack); |
| while (!AllocaTmps.empty()) { |
| GlobalVariable *Tmp = AllocaTmps.back(); |
| AllocaTmps.pop_back(); |
| |
| // If there are still users of the alloca, the program is doing something |
| // silly, e.g. storing the address of the alloca somewhere and using it |
| // later. Since this is undefined, we'll just make it be null. |
| if (!Tmp->use_empty()) |
| Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType())); |
| delete Tmp; |
| } |
| } |
| |
| /// EvaluateFunction - Evaluate a call to function F, returning true if |
| /// successful, false if we can't evaluate it. ActualArgs contains the formal |
| /// arguments for the function. |
| bool EvaluateFunction(Function *F, Constant *&RetVal, |
| const SmallVectorImpl<Constant*> &ActualArgs); |
| |
| /// EvaluateBlock - Evaluate all instructions in block BB, returning true if |
| /// successful, false if we can't evaluate it. NewBB returns the next BB that |
| /// control flows into, or null upon return. |
| bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB); |
| |
| Constant *getVal(Value *V) { |
| if (Constant *CV = dyn_cast<Constant>(V)) return CV; |
| Constant *R = ValueStack.back()->lookup(V); |
| assert(R && "Reference to an uncomputed value!"); |
| return R; |
| } |
| |
| void setVal(Value *V, Constant *C) { |
| ValueStack.back()->operator[](V) = C; |
| } |
| |
| const DenseMap<Constant*, Constant*> &getMutatedMemory() const { |
| return MutatedMemory; |
| } |
| |
| const SmallPtrSet<GlobalVariable*, 8> &getInvariants() const { |
| return Invariants; |
| } |
| |
| private: |
| Constant *ComputeLoadResult(Constant *P); |
| |
| /// ValueStack - As we compute SSA register values, we store their contents |
| /// here. The back of the vector contains the current function and the stack |
| /// contains the values in the calling frames. |
| SmallVector<DenseMap<Value*, Constant*>*, 4> ValueStack; |
| |
| /// CallStack - This is used to detect recursion. In pathological situations |
| /// we could hit exponential behavior, but at least there is nothing |
| /// unbounded. |
| SmallVector<Function*, 4> CallStack; |
| |
| /// MutatedMemory - For each store we execute, we update this map. Loads |
| /// check this to get the most up-to-date value. If evaluation is successful, |
| /// this state is committed to the process. |
| DenseMap<Constant*, Constant*> MutatedMemory; |
| |
| /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable |
| /// to represent its body. This vector is needed so we can delete the |
| /// temporary globals when we are done. |
| SmallVector<GlobalVariable*, 32> AllocaTmps; |
| |
| /// Invariants - These global variables have been marked invariant by the |
| /// static constructor. |
| SmallPtrSet<GlobalVariable*, 8> Invariants; |
| |
| /// SimpleConstants - These are constants we have checked and know to be |
| /// simple enough to live in a static initializer of a global. |
| SmallPtrSet<Constant*, 8> SimpleConstants; |
| |
| const DataLayout *TD; |
| const TargetLibraryInfo *TLI; |
| }; |
| |
| } // anonymous namespace |
| |
| /// ComputeLoadResult - Return the value that would be computed by a load from |
| /// P after the stores reflected by 'memory' have been performed. If we can't |
| /// decide, return null. |
| Constant *Evaluator::ComputeLoadResult(Constant *P) { |
| // If this memory location has been recently stored, use the stored value: it |
| // is the most up-to-date. |
| DenseMap<Constant*, Constant*>::const_iterator I = MutatedMemory.find(P); |
| if (I != MutatedMemory.end()) return I->second; |
| |
| // Access it. |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) { |
| if (GV->hasDefinitiveInitializer()) |
| return GV->getInitializer(); |
| return 0; |
| } |
| |
| // Handle a constantexpr getelementptr. |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P)) |
| if (CE->getOpcode() == Instruction::GetElementPtr && |
| isa<GlobalVariable>(CE->getOperand(0))) { |
| GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); |
| if (GV->hasDefinitiveInitializer()) |
| return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); |
| } |
| |
| return 0; // don't know how to evaluate. |
| } |
| |
| /// EvaluateBlock - Evaluate all instructions in block BB, returning true if |
| /// successful, false if we can't evaluate it. NewBB returns the next BB that |
| /// control flows into, or null upon return. |
| bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst, |
| BasicBlock *&NextBB) { |
| // This is the main evaluation loop. |
| while (1) { |
| Constant *InstResult = 0; |
| |
| DEBUG(dbgs() << "Evaluating Instruction: " << *CurInst << "\n"); |
| |
| if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) { |
| if (!SI->isSimple()) { |
| DEBUG(dbgs() << "Store is not simple! Can not evaluate.\n"); |
| return false; // no volatile/atomic accesses. |
| } |
| Constant *Ptr = getVal(SI->getOperand(1)); |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) { |
| DEBUG(dbgs() << "Folding constant ptr expression: " << *Ptr); |
| Ptr = ConstantFoldConstantExpression(CE, TD, TLI); |
| DEBUG(dbgs() << "; To: " << *Ptr << "\n"); |
| } |
| if (!isSimpleEnoughPointerToCommit(Ptr)) { |
| // If this is too complex for us to commit, reject it. |
| DEBUG(dbgs() << "Pointer is too complex for us to evaluate store."); |
| return false; |
| } |
| |
| Constant *Val = getVal(SI->getOperand(0)); |
| |
| // If this might be too difficult for the backend to handle (e.g. the addr |
| // of one global variable divided by another) then we can't commit it. |
| if (!isSimpleEnoughValueToCommit(Val, SimpleConstants, TD)) { |
| DEBUG(dbgs() << "Store value is too complex to evaluate store. " << *Val |
| << "\n"); |
| return false; |
| } |
| |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) { |
| if (CE->getOpcode() == Instruction::BitCast) { |
| DEBUG(dbgs() << "Attempting to resolve bitcast on constant ptr.\n"); |
| // If we're evaluating a store through a bitcast, then we need |
| // to pull the bitcast off the pointer type and push it onto the |
| // stored value. |
| Ptr = CE->getOperand(0); |
| |
| Type *NewTy = cast<PointerType>(Ptr->getType())->getElementType(); |
| |
| // In order to push the bitcast onto the stored value, a bitcast |
| // from NewTy to Val's type must be legal. If it's not, we can try |
| // introspecting NewTy to find a legal conversion. |
| while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) { |
| // If NewTy is a struct, we can convert the pointer to the struct |
| // into a pointer to its first member. |
| // FIXME: This could be extended to support arrays as well. |
| if (StructType *STy = dyn_cast<StructType>(NewTy)) { |
| NewTy = STy->getTypeAtIndex(0U); |
| |
| IntegerType *IdxTy = IntegerType::get(NewTy->getContext(), 32); |
| Constant *IdxZero = ConstantInt::get(IdxTy, 0, false); |
| Constant * const IdxList[] = {IdxZero, IdxZero}; |
| |
| Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList); |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) |
| Ptr = ConstantFoldConstantExpression(CE, TD, TLI); |
| |
| // If we can't improve the situation by introspecting NewTy, |
| // we have to give up. |
| } else { |
| DEBUG(dbgs() << "Failed to bitcast constant ptr, can not " |
| "evaluate.\n"); |
| return false; |
| } |
| } |
| |
| // If we found compatible types, go ahead and push the bitcast |
| // onto the stored value. |
| Val = ConstantExpr::getBitCast(Val, NewTy); |
| |
| DEBUG(dbgs() << "Evaluated bitcast: " << *Val << "\n"); |
| } |
| } |
| |
| MutatedMemory[Ptr] = Val; |
| } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) { |
| InstResult = ConstantExpr::get(BO->getOpcode(), |
| getVal(BO->getOperand(0)), |
| getVal(BO->getOperand(1))); |
| DEBUG(dbgs() << "Found a BinaryOperator! Simplifying: " << *InstResult |
| << "\n"); |
| } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) { |
| InstResult = ConstantExpr::getCompare(CI->getPredicate(), |
| getVal(CI->getOperand(0)), |
| getVal(CI->getOperand(1))); |
| DEBUG(dbgs() << "Found a CmpInst! Simplifying: " << *InstResult |
| << "\n"); |
| } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) { |
| InstResult = ConstantExpr::getCast(CI->getOpcode(), |
| getVal(CI->getOperand(0)), |
| CI->getType()); |
| DEBUG(dbgs() << "Found a Cast! Simplifying: " << *InstResult |
| << "\n"); |
| } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) { |
| InstResult = ConstantExpr::getSelect(getVal(SI->getOperand(0)), |
| getVal(SI->getOperand(1)), |
| getVal(SI->getOperand(2))); |
| DEBUG(dbgs() << "Found a Select! Simplifying: " << *InstResult |
| << "\n"); |
| } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) { |
| Constant *P = getVal(GEP->getOperand(0)); |
| SmallVector<Constant*, 8> GEPOps; |
| for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end(); |
| i != e; ++i) |
| GEPOps.push_back(getVal(*i)); |
| InstResult = |
| ConstantExpr::getGetElementPtr(P, GEPOps, |
| cast<GEPOperator>(GEP)->isInBounds()); |
| DEBUG(dbgs() << "Found a GEP! Simplifying: " << *InstResult |
| << "\n"); |
| } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) { |
| |
| if (!LI->isSimple()) { |
| DEBUG(dbgs() << "Found a Load! Not a simple load, can not evaluate.\n"); |
| return false; // no volatile/atomic accesses. |
| } |
| |
| Constant *Ptr = getVal(LI->getOperand(0)); |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) { |
| Ptr = ConstantFoldConstantExpression(CE, TD, TLI); |
| DEBUG(dbgs() << "Found a constant pointer expression, constant " |
| "folding: " << *Ptr << "\n"); |
| } |
| InstResult = ComputeLoadResult(Ptr); |
| if (InstResult == 0) { |
| DEBUG(dbgs() << "Failed to compute load result. Can not evaluate load." |
| "\n"); |
| return false; // Could not evaluate load. |
| } |
| |
| DEBUG(dbgs() << "Evaluated load: " << *InstResult << "\n"); |
| } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) { |
| if (AI->isArrayAllocation()) { |
| DEBUG(dbgs() << "Found an array alloca. Can not evaluate.\n"); |
| return false; // Cannot handle array allocs. |
| } |
| Type *Ty = AI->getType()->getElementType(); |
| AllocaTmps.push_back(new GlobalVariable(Ty, false, |
| GlobalValue::InternalLinkage, |
| UndefValue::get(Ty), |
| AI->getName())); |
| InstResult = AllocaTmps.back(); |
| DEBUG(dbgs() << "Found an alloca. Result: " << *InstResult << "\n"); |
| } else if (isa<CallInst>(CurInst) || isa<InvokeInst>(CurInst)) { |
| CallSite CS(CurInst); |
| |
| // Debug info can safely be ignored here. |
| if (isa<DbgInfoIntrinsic>(CS.getInstruction())) { |
| DEBUG(dbgs() << "Ignoring debug info.\n"); |
| ++CurInst; |
| continue; |
| } |
| |
| // Cannot handle inline asm. |
| if (isa<InlineAsm>(CS.getCalledValue())) { |
| DEBUG(dbgs() << "Found inline asm, can not evaluate.\n"); |
| return false; |
| } |
| |
| if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) { |
| if (MemSetInst *MSI = dyn_cast<MemSetInst>(II)) { |
| if (MSI->isVolatile()) { |
| DEBUG(dbgs() << "Can not optimize a volatile memset " << |
| "intrinsic.\n"); |
| return false; |
| } |
| Constant *Ptr = getVal(MSI->getDest()); |
| Constant *Val = getVal(MSI->getValue()); |
| Constant *DestVal = ComputeLoadResult(getVal(Ptr)); |
| if (Val->isNullValue() && DestVal && DestVal->isNullValue()) { |
| // This memset is a no-op. |
| DEBUG(dbgs() << "Ignoring no-op memset.\n"); |
| ++CurInst; |
| continue; |
| } |
| } |
| |
| if (II->getIntrinsicID() == Intrinsic::lifetime_start || |
| II->getIntrinsicID() == Intrinsic::lifetime_end) { |
| DEBUG(dbgs() << "Ignoring lifetime intrinsic.\n"); |
| ++CurInst; |
| continue; |
| } |
| |
| if (II->getIntrinsicID() == Intrinsic::invariant_start) { |
| // We don't insert an entry into Values, as it doesn't have a |
| // meaningful return value. |
| if (!II->use_empty()) { |
| DEBUG(dbgs() << "Found unused invariant_start. Cant evaluate.\n"); |
| return false; |
| } |
| ConstantInt *Size = cast<ConstantInt>(II->getArgOperand(0)); |
| Value *PtrArg = getVal(II->getArgOperand(1)); |
| Value *Ptr = PtrArg->stripPointerCasts(); |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) { |
| Type *ElemTy = cast<PointerType>(GV->getType())->getElementType(); |
| if (!Size->isAllOnesValue() && |
| Size->getValue().getLimitedValue() >= |
| TD->getTypeStoreSize(ElemTy)) { |
| Invariants.insert(GV); |
| DEBUG(dbgs() << "Found a global var that is an invariant: " << *GV |
| << "\n"); |
| } else { |
| DEBUG(dbgs() << "Found a global var, but can not treat it as an " |
| "invariant.\n"); |
| } |
| } |
| // Continue even if we do nothing. |
| ++CurInst; |
| continue; |
| } |
| |
| DEBUG(dbgs() << "Unknown intrinsic. Can not evaluate.\n"); |
| return false; |
| } |
| |
| // Resolve function pointers. |
| Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue())); |
| if (!Callee || Callee->mayBeOverridden()) { |
| DEBUG(dbgs() << "Can not resolve function pointer.\n"); |
| return false; // Cannot resolve. |
| } |
| |
| SmallVector<Constant*, 8> Formals; |
| for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end(); i != e; ++i) |
| Formals.push_back(getVal(*i)); |
| |
| if (Callee->isDeclaration()) { |
| // If this is a function we can constant fold, do it. |
| if (Constant *C = ConstantFoldCall(Callee, Formals, TLI)) { |
| InstResult = C; |
| DEBUG(dbgs() << "Constant folded function call. Result: " << |
| *InstResult << "\n"); |
| } else { |
| DEBUG(dbgs() << "Can not constant fold function call.\n"); |
| return false; |
| } |
| } else { |
| if (Callee->getFunctionType()->isVarArg()) { |
| DEBUG(dbgs() << "Can not constant fold vararg function call.\n"); |
| return false; |
| } |
| |
| Constant *RetVal = 0; |
| // Execute the call, if successful, use the return value. |
| ValueStack.push_back(new DenseMap<Value*, Constant*>); |
| if (!EvaluateFunction(Callee, RetVal, Formals)) { |
| DEBUG(dbgs() << "Failed to evaluate function.\n"); |
| return false; |
| } |
| delete ValueStack.pop_back_val(); |
| InstResult = RetVal; |
| |
| if (InstResult != NULL) { |
| DEBUG(dbgs() << "Successfully evaluated function. Result: " << |
| InstResult << "\n\n"); |
| } else { |
| DEBUG(dbgs() << "Successfully evaluated function. Result: 0\n\n"); |
| } |
| } |
| } else if (isa<TerminatorInst>(CurInst)) { |
| DEBUG(dbgs() << "Found a terminator instruction.\n"); |
| |
| if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) { |
| if (BI->isUnconditional()) { |
| NextBB = BI->getSuccessor(0); |
| } else { |
| ConstantInt *Cond = |
| dyn_cast<ConstantInt>(getVal(BI->getCondition())); |
| if (!Cond) return false; // Cannot determine. |
| |
| NextBB = BI->getSuccessor(!Cond->getZExtValue()); |
| } |
| } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) { |
| ConstantInt *Val = |
| dyn_cast<ConstantInt>(getVal(SI->getCondition())); |
| if (!Val) return false; // Cannot determine. |
| NextBB = SI->findCaseValue(Val).getCaseSuccessor(); |
| } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) { |
| Value *Val = getVal(IBI->getAddress())->stripPointerCasts(); |
| if (BlockAddress *BA = dyn_cast<BlockAddress>(Val)) |
| NextBB = BA->getBasicBlock(); |
| else |
| return false; // Cannot determine. |
| } else if (isa<ReturnInst>(CurInst)) { |
| NextBB = 0; |
| } else { |
| // invoke, unwind, resume, unreachable. |
| DEBUG(dbgs() << "Can not handle terminator."); |
| return false; // Cannot handle this terminator. |
| } |
| |
| // We succeeded at evaluating this block! |
| DEBUG(dbgs() << "Successfully evaluated block.\n"); |
| return true; |
| } else { |
| // Did not know how to evaluate this! |
| DEBUG(dbgs() << "Failed to evaluate block due to unhandled instruction." |
| "\n"); |
| return false; |
| } |
| |
| if (!CurInst->use_empty()) { |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult)) |
| InstResult = ConstantFoldConstantExpression(CE, TD, TLI); |
| |
| setVal(CurInst, InstResult); |
| } |
| |
| // If we just processed an invoke, we finished evaluating the block. |
| if (InvokeInst *II = dyn_cast<InvokeInst>(CurInst)) { |
| NextBB = II->getNormalDest(); |
| DEBUG(dbgs() << "Found an invoke instruction. Finished Block.\n\n"); |
| return true; |
| } |
| |
| // Advance program counter. |
| ++CurInst; |
| } |
| } |
| |
| /// EvaluateFunction - Evaluate a call to function F, returning true if |
| /// successful, false if we can't evaluate it. ActualArgs contains the formal |
| /// arguments for the function. |
| bool Evaluator::EvaluateFunction(Function *F, Constant *&RetVal, |
| const SmallVectorImpl<Constant*> &ActualArgs) { |
| // Check to see if this function is already executing (recursion). If so, |
| // bail out. TODO: we might want to accept limited recursion. |
| if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end()) |
| return false; |
| |
| CallStack.push_back(F); |
| |
| // Initialize arguments to the incoming values specified. |
| unsigned ArgNo = 0; |
| for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E; |
| ++AI, ++ArgNo) |
| setVal(AI, ActualArgs[ArgNo]); |
| |
| // ExecutedBlocks - We only handle non-looping, non-recursive code. As such, |
| // we can only evaluate any one basic block at most once. This set keeps |
| // track of what we have executed so we can detect recursive cases etc. |
| SmallPtrSet<BasicBlock*, 32> ExecutedBlocks; |
| |
| // CurBB - The current basic block we're evaluating. |
| BasicBlock *CurBB = F->begin(); |
| |
| BasicBlock::iterator CurInst = CurBB->begin(); |
| |
| while (1) { |
| BasicBlock *NextBB = 0; // Initialized to avoid compiler warnings. |
| DEBUG(dbgs() << "Trying to evaluate BB: " << *CurBB << "\n"); |
| |
| if (!EvaluateBlock(CurInst, NextBB)) |
| return false; |
| |
| if (NextBB == 0) { |
| // Successfully running until there's no next block means that we found |
| // the return. Fill it the return value and pop the call stack. |
| ReturnInst *RI = cast<ReturnInst>(CurBB->getTerminator()); |
| if (RI->getNumOperands()) |
| RetVal = getVal(RI->getOperand(0)); |
| CallStack.pop_back(); |
| return true; |
| } |
| |
| // Okay, we succeeded in evaluating this control flow. See if we have |
| // executed the new block before. If so, we have a looping function, |
| // which we cannot evaluate in reasonable time. |
| if (!ExecutedBlocks.insert(NextBB)) |
| return false; // looped! |
| |
| // Okay, we have never been in this block before. Check to see if there |
| // are any PHI nodes. If so, evaluate them with information about where |
| // we came from. |
| PHINode *PN = 0; |
| for (CurInst = NextBB->begin(); |
| (PN = dyn_cast<PHINode>(CurInst)); ++CurInst) |
| setVal(PN, getVal(PN->getIncomingValueForBlock(CurBB))); |
| |
| // Advance to the next block. |
| CurBB = NextBB; |
| } |
| } |
| |
| /// EvaluateStaticConstructor - Evaluate static constructors in the function, if |
| /// we can. Return true if we can, false otherwise. |
| static bool EvaluateStaticConstructor(Function *F, const DataLayout *TD, |
| const TargetLibraryInfo *TLI) { |
| // Call the function. |
| Evaluator Eval(TD, TLI); |
| Constant *RetValDummy; |
| bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy, |
| SmallVector<Constant*, 0>()); |
| |
| if (EvalSuccess) { |
| // We succeeded at evaluation: commit the result. |
| DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" |
| << F->getName() << "' to " << Eval.getMutatedMemory().size() |
| << " stores.\n"); |
| for (DenseMap<Constant*, Constant*>::const_iterator I = |
| Eval.getMutatedMemory().begin(), E = Eval.getMutatedMemory().end(); |
| I != E; ++I) |
| CommitValueTo(I->second, I->first); |
| for (SmallPtrSet<GlobalVariable*, 8>::const_iterator I = |
| Eval.getInvariants().begin(), E = Eval.getInvariants().end(); |
| I != E; ++I) |
| (*I)->setConstant(true); |
| } |
| |
| return EvalSuccess; |
| } |
| |
| /// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible. |
| /// Return true if anything changed. |
| bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) { |
| std::vector<Function*> Ctors = ParseGlobalCtors(GCL); |
| bool MadeChange = false; |
| if (Ctors.empty()) return false; |
| |
| // Loop over global ctors, optimizing them when we can. |
| for (unsigned i = 0; i != Ctors.size(); ++i) { |
| Function *F = Ctors[i]; |
| // Found a null terminator in the middle of the list, prune off the rest of |
| // the list. |
| if (F == 0) { |
| if (i != Ctors.size()-1) { |
| Ctors.resize(i+1); |
| MadeChange = true; |
| } |
| break; |
| } |
| DEBUG(dbgs() << "Optimizing Global Constructor: " << *F << "\n"); |
| |
| // We cannot simplify external ctor functions. |
| if (F->empty()) continue; |
| |
| // If we can evaluate the ctor at compile time, do. |
| if (EvaluateStaticConstructor(F, TD, TLI)) { |
| Ctors.erase(Ctors.begin()+i); |
| MadeChange = true; |
| --i; |
| ++NumCtorsEvaluated; |
| continue; |
| } |
| } |
| |
| if (!MadeChange) return false; |
| |
| GCL = InstallGlobalCtors(GCL, Ctors); |
| return true; |
| } |
| |
| bool GlobalOpt::OptimizeGlobalAliases(Module &M) { |
| bool Changed = false; |
| |
| for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); |
| I != E;) { |
| Module::alias_iterator J = I++; |
| // Aliases without names cannot be referenced outside this module. |
| if (!J->hasName() && !J->isDeclaration()) |
| J->setLinkage(GlobalValue::InternalLinkage); |
| // If the aliasee may change at link time, nothing can be done - bail out. |
| if (J->mayBeOverridden()) |
| continue; |
| |
| Constant *Aliasee = J->getAliasee(); |
| GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts()); |
| Target->removeDeadConstantUsers(); |
| bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse(); |
| |
| // Make all users of the alias use the aliasee instead. |
| if (!J->use_empty()) { |
| J->replaceAllUsesWith(Aliasee); |
| ++NumAliasesResolved; |
| Changed = true; |
| } |
| |
| // If the alias is externally visible, we may still be able to simplify it. |
| if (!J->hasLocalLinkage()) { |
| // If the aliasee has internal linkage, give it the name and linkage |
| // of the alias, and delete the alias. This turns: |
| // define internal ... @f(...) |
| // @a = alias ... @f |
| // into: |
| // define ... @a(...) |
| if (!Target->hasLocalLinkage()) |
| continue; |
| |
| // Do not perform the transform if multiple aliases potentially target the |
| // aliasee. This check also ensures that it is safe to replace the section |
| // and other attributes of the aliasee with those of the alias. |
| if (!hasOneUse) |
| continue; |
| |
| // Give the aliasee the name, linkage and other attributes of the alias. |
| Target->takeName(J); |
| Target->setLinkage(J->getLinkage()); |
| Target->GlobalValue::copyAttributesFrom(J); |
| } |
| |
| // Delete the alias. |
| M.getAliasList().erase(J); |
| ++NumAliasesRemoved; |
| Changed = true; |
| } |
| |
| return Changed; |
| } |
| |
| static Function *FindCXAAtExit(Module &M, TargetLibraryInfo *TLI) { |
| if (!TLI->has(LibFunc::cxa_atexit)) |
| return 0; |
| |
| Function *Fn = M.getFunction(TLI->getName(LibFunc::cxa_atexit)); |
| |
| if (!Fn) |
| return 0; |
| |
| FunctionType *FTy = Fn->getFunctionType(); |
| |
| // Checking that the function has the right return type, the right number of |
| // parameters and that they all have pointer types should be enough. |
| if (!FTy->getReturnType()->isIntegerTy() || |
| FTy->getNumParams() != 3 || |
| !FTy->getParamType(0)->isPointerTy() || |
| !FTy->getParamType(1)->isPointerTy() || |
| !FTy->getParamType(2)->isPointerTy()) |
| return 0; |
| |
| return Fn; |
| } |
| |
| /// cxxDtorIsEmpty - Returns whether the given function is an empty C++ |
| /// destructor and can therefore be eliminated. |
| /// Note that we assume that other optimization passes have already simplified |
| /// the code so we only look for a function with a single basic block, where |
| /// the only allowed instructions are 'ret', 'call' to an empty C++ dtor and |
| /// other side-effect free instructions. |
| static bool cxxDtorIsEmpty(const Function &Fn, |
| SmallPtrSet<const Function *, 8> &CalledFunctions) { |
| // FIXME: We could eliminate C++ destructors if they're readonly/readnone and |
| // nounwind, but that doesn't seem worth doing. |
| if (Fn.isDeclaration()) |
| return false; |
| |
| if (++Fn.begin() != Fn.end()) |
| return false; |
| |
| const BasicBlock &EntryBlock = Fn.getEntryBlock(); |
| for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end(); |
| I != E; ++I) { |
| if (const CallInst *CI = dyn_cast<CallInst>(I)) { |
| // Ignore debug intrinsics. |
| if (isa<DbgInfoIntrinsic>(CI)) |
| continue; |
| |
| const Function *CalledFn = CI->getCalledFunction(); |
| |
| if (!CalledFn) |
| return false; |
| |
| SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions); |
| |
| // Don't treat recursive functions as empty. |
| if (!NewCalledFunctions.insert(CalledFn)) |
| return false; |
| |
| if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions)) |
| return false; |
| } else if (isa<ReturnInst>(*I)) |
| return true; // We're done. |
| else if (I->mayHaveSideEffects()) |
| return false; // Destructor with side effects, bail. |
| } |
| |
| return false; |
| } |
| |
| bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) { |
| /// Itanium C++ ABI p3.3.5: |
| /// |
| /// After constructing a global (or local static) object, that will require |
| /// destruction on exit, a termination function is registered as follows: |
| /// |
| /// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d ); |
| /// |
| /// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the |
| /// call f(p) when DSO d is unloaded, before all such termination calls |
| /// registered before this one. It returns zero if registration is |
| /// successful, nonzero on failure. |
| |
| // This pass will look for calls to __cxa_atexit where the function is trivial |
| // and remove them. |
| bool Changed = false; |
| |
| for (Function::use_iterator I = CXAAtExitFn->use_begin(), |
| E = CXAAtExitFn->use_end(); I != E;) { |
| // We're only interested in calls. Theoretically, we could handle invoke |
| // instructions as well, but neither llvm-gcc nor clang generate invokes |
| // to __cxa_atexit. |
| CallInst *CI = dyn_cast<CallInst>(*I++); |
| if (!CI) |
| continue; |
| |
| Function *DtorFn = |
| dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts()); |
| if (!DtorFn) |
| continue; |
| |
| SmallPtrSet<const Function *, 8> CalledFunctions; |
| if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions)) |
| continue; |
| |
| // Just remove the call. |
| CI->replaceAllUsesWith(Constant::getNullValue(CI->getType())); |
| CI->eraseFromParent(); |
| |
| ++NumCXXDtorsRemoved; |
| |
| Changed |= true; |
| } |
| |
| return Changed; |
| } |
| |
| bool GlobalOpt::runOnModule(Module &M) { |
| bool Changed = false; |
| |
| TD = getAnalysisIfAvailable<DataLayout>(); |
| TLI = &getAnalysis<TargetLibraryInfo>(); |
| |
| // Try to find the llvm.globalctors list. |
| GlobalVariable *GlobalCtors = FindGlobalCtors(M); |
| |
| Function *CXAAtExitFn = FindCXAAtExit(M, TLI); |
| |
| bool LocalChange = true; |
| while (LocalChange) { |
| LocalChange = false; |
| |
| // Delete functions that are trivially dead, ccc -> fastcc |
| LocalChange |= OptimizeFunctions(M); |
| |
| // Optimize global_ctors list. |
| if (GlobalCtors) |
| LocalChange |= OptimizeGlobalCtorsList(GlobalCtors); |
| |
| // Optimize non-address-taken globals. |
| LocalChange |= OptimizeGlobalVars(M); |
| |
| // Resolve aliases, when possible. |
| LocalChange |= OptimizeGlobalAliases(M); |
| |
| // Try to remove trivial global destructors. |
| if (CXAAtExitFn) |
| LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn); |
| |
| Changed |= LocalChange; |
| } |
| |
| // TODO: Move all global ctors functions to the end of the module for code |
| // layout. |
| |
| return Changed; |
| } |