| //===- 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/CallingConv.h" |
| #include "llvm/Constants.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/IntrinsicInst.h" |
| #include "llvm/Module.h" |
| #include "llvm/Pass.h" |
| #include "llvm/Analysis/ConstantFolding.h" |
| #include "llvm/Target/TargetData.h" |
| #include "llvm/Support/CallSite.h" |
| #include "llvm/Support/Compiler.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/GetElementPtrTypeIterator.h" |
| #include "llvm/Support/MathExtras.h" |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallVector.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/ADT/StringExtras.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include <algorithm> |
| using namespace llvm; |
| |
| STATISTIC(NumMarked , "Number of globals marked constant"); |
| 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"); |
| |
| namespace { |
| struct VISIBILITY_HIDDEN GlobalOpt : public ModulePass { |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<TargetData>(); |
| } |
| static char ID; // Pass identification, replacement for typeid |
| GlobalOpt() : ModulePass(&ID) {} |
| |
| bool runOnModule(Module &M); |
| |
| private: |
| GlobalVariable *FindGlobalCtors(Module &M); |
| bool OptimizeFunctions(Module &M); |
| bool OptimizeGlobalVars(Module &M); |
| bool ResolveAliases(Module &M); |
| bool OptimizeGlobalCtorsList(GlobalVariable *&GCL); |
| bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI); |
| }; |
| } |
| |
| char GlobalOpt::ID = 0; |
| static RegisterPass<GlobalOpt> X("globalopt", "Global Variable Optimizer"); |
| |
| 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 VISIBILITY_HIDDEN GlobalStatus { |
| /// 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. |
| 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; |
| |
| /// HasPHIUser - Set to true if this global has a user that is a PHI node. |
| bool HasPHIUser; |
| |
| GlobalStatus() : isLoaded(false), StoredType(NotStored), StoredOnceValue(0), |
| AccessingFunction(0), HasMultipleAccessingFunctions(false), |
| HasNonInstructionUser(false), HasPHIUser(false) {} |
| }; |
| |
| } |
| |
| /// ConstantIsDead - Return true if the specified constant is (transitively) |
| /// dead. The constant may be used by other constants (e.g. constant arrays and |
| /// constant exprs) as long as they are dead, but it cannot be used by anything |
| /// else. |
| static bool ConstantIsDead(Constant *C) { |
| if (isa<GlobalValue>(C)) return false; |
| |
| for (Value::use_iterator UI = C->use_begin(), E = C->use_end(); UI != E; ++UI) |
| if (Constant *CU = dyn_cast<Constant>(*UI)) { |
| if (!ConstantIsDead(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(Value *V, GlobalStatus &GS, |
| SmallPtrSet<PHINode*, 16> &PHIUsers) { |
| for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(*UI)) { |
| GS.HasNonInstructionUser = true; |
| |
| if (AnalyzeGlobal(CE, GS, PHIUsers)) return true; |
| |
| } else if (Instruction *I = dyn_cast<Instruction>(*UI)) { |
| if (!GS.HasMultipleAccessingFunctions) { |
| Function *F = I->getParent()->getParent(); |
| if (GS.AccessingFunction == 0) |
| GS.AccessingFunction = F; |
| else if (GS.AccessingFunction != F) |
| GS.HasMultipleAccessingFunctions = true; |
| } |
| if (LoadInst *LI = dyn_cast<LoadInst>(I)) { |
| GS.isLoaded = true; |
| if (LI->isVolatile()) return true; // Don't hack on volatile loads. |
| } else if (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; |
| |
| if (SI->isVolatile()) return true; // Don't hack on volatile stores. |
| |
| // 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 (GlobalVariable *GV = dyn_cast<GlobalVariable>(SI->getOperand(1))){ |
| Value *StoredVal = SI->getOperand(0); |
| if (StoredVal == GV->getInitializer()) { |
| if (GS.StoredType < GlobalStatus::isInitializerStored) |
| GS.StoredType = GlobalStatus::isInitializerStored; |
| } else if (isa<LoadInst>(StoredVal) && |
| cast<LoadInst>(StoredVal)->getOperand(0) == GV) { |
| // G = G |
| 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<GetElementPtrInst>(I)) { |
| if (AnalyzeGlobal(I, GS, PHIUsers)) return true; |
| } else if (isa<SelectInst>(I)) { |
| if (AnalyzeGlobal(I, GS, PHIUsers)) return true; |
| } else if (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; |
| GS.HasPHIUser = true; |
| } else if (isa<CmpInst>(I)) { |
| } else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) { |
| if (I->getOperand(1) == V) |
| GS.StoredType = GlobalStatus::isStored; |
| if (I->getOperand(2) == V) |
| GS.isLoaded = true; |
| } else if (isa<MemSetInst>(I)) { |
| assert(I->getOperand(1) == V && "Memset only takes one pointer!"); |
| GS.StoredType = GlobalStatus::isStored; |
| } else { |
| return true; // Any other non-load instruction might take address! |
| } |
| } else if (Constant *C = dyn_cast<Constant>(*UI)) { |
| GS.HasNonInstructionUser = true; |
| // We might have a dead and dangling constant hanging off of here. |
| if (!ConstantIsDead(C)) |
| return true; |
| } else { |
| GS.HasNonInstructionUser = true; |
| // Otherwise must be some other user. |
| return true; |
| } |
| |
| return false; |
| } |
| |
| static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) { |
| ConstantInt *CI = dyn_cast<ConstantInt>(Idx); |
| if (!CI) return 0; |
| unsigned IdxV = CI->getZExtValue(); |
| |
| if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Agg)) { |
| if (IdxV < CS->getNumOperands()) return CS->getOperand(IdxV); |
| } else if (ConstantArray *CA = dyn_cast<ConstantArray>(Agg)) { |
| if (IdxV < CA->getNumOperands()) return CA->getOperand(IdxV); |
| } else if (ConstantVector *CP = dyn_cast<ConstantVector>(Agg)) { |
| if (IdxV < CP->getNumOperands()) return CP->getOperand(IdxV); |
| } else if (isa<ConstantAggregateZero>(Agg)) { |
| if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { |
| if (IdxV < STy->getNumElements()) |
| return Constant::getNullValue(STy->getElementType(IdxV)); |
| } else if (const SequentialType *STy = |
| dyn_cast<SequentialType>(Agg->getType())) { |
| return Constant::getNullValue(STy->getElementType()); |
| } |
| } else if (isa<UndefValue>(Agg)) { |
| if (const StructType *STy = dyn_cast<StructType>(Agg->getType())) { |
| if (IdxV < STy->getNumElements()) |
| return UndefValue::get(STy->getElementType(IdxV)); |
| } else if (const SequentialType *STy = |
| dyn_cast<SequentialType>(Agg->getType())) { |
| return UndefValue::get(STy->getElementType()); |
| } |
| } |
| return 0; |
| } |
| |
| |
| /// 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) { |
| 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); |
| } else if (CE->getOpcode() == Instruction::BitCast && |
| isa<PointerType>(CE->getType())) { |
| // Pointer cast, delete any stores and memsets to the global. |
| Changed |= CleanupConstantGlobalUsers(CE, 0); |
| } |
| |
| 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)); |
| if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr) |
| SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); |
| } |
| Changed |= CleanupConstantGlobalUsers(GEP, SubInit); |
| |
| 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 (ConstantIsDead(C)) { |
| C->destroyConstant(); |
| // This could have invalidated UI, start over from scratch. |
| CleanupConstantGlobalUsers(V, Init); |
| 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 ConstantIsDead(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 (const 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 && (isa<ArrayType>(*GEPI) || isa<VectorType>(*GEPI)); |
| ++GEPI) { |
| uint64_t NumElements; |
| if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI)) |
| NumElements = SubArrayTy->getNumElements(); |
| else |
| NumElements = cast<VectorType>(*GEPI)->getNumElements(); |
| |
| 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 TargetData &TD) { |
| // Make sure this global only has simple uses that we can SRA. |
| if (!GlobalUsersSafeToSRA(GV)) |
| return 0; |
| |
| assert(GV->hasInternalLinkage() && !GV->isConstant()); |
| Constant *Init = GV->getInitializer(); |
| const 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 (const 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 = getAggregateConstantElement(Init, |
| ConstantInt::get(Type::Int32Ty, i)); |
| assert(In && "Couldn't get element of initializer?"); |
| GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false, |
| GlobalVariable::InternalLinkage, |
| In, GV->getName()+"."+utostr(i), |
| (Module *)NULL, |
| GV->isThreadLocal(), |
| 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 (const SequentialType *STy = dyn_cast<SequentialType>(Ty)) { |
| unsigned NumElements = 0; |
| if (const 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.getTypePaddedSize(STy->getElementType()); |
| unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType()); |
| for (unsigned i = 0, e = NumElements; i != e; ++i) { |
| Constant *In = getAggregateConstantElement(Init, |
| ConstantInt::get(Type::Int32Ty, i)); |
| assert(In && "Couldn't get element of initializer?"); |
| |
| GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false, |
| GlobalVariable::InternalLinkage, |
| In, GV->getName()+"."+utostr(i), |
| (Module *)NULL, |
| GV->isThreadLocal(), |
| 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; |
| |
| DOUT << "PERFORMING GLOBAL SRA ON: " << *GV; |
| |
| Constant *NullInt = Constant::getNullValue(Type::Int32Ty); |
| |
| // 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[0], Idxs.size()); |
| } 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.begin(), Idxs.end(), |
| GEPI->getName()+"."+utostr(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(Value *V, |
| SmallPtrSet<PHINode*, 8> &PHIs) { |
| for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ++UI) |
| if (isa<LoadInst>(*UI)) { |
| // Will trap. |
| } else if (StoreInst *SI = dyn_cast<StoreInst>(*UI)) { |
| if (SI->getOperand(0) == V) { |
| //cerr << "NONTRAPPING USE: " << **UI; |
| return false; // Storing the value. |
| } |
| } else if (CallInst *CI = dyn_cast<CallInst>(*UI)) { |
| if (CI->getOperand(0) != V) { |
| //cerr << "NONTRAPPING USE: " << **UI; |
| return false; // Not calling the ptr |
| } |
| } else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI)) { |
| if (II->getOperand(0) != V) { |
| //cerr << "NONTRAPPING USE: " << **UI; |
| return false; // Not calling the ptr |
| } |
| } else if (BitCastInst *CI = dyn_cast<BitCastInst>(*UI)) { |
| if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false; |
| } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(*UI)) { |
| if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false; |
| } else if (PHINode *PN = dyn_cast<PHINode>(*UI)) { |
| // If we've already seen this phi node, ignore it, it has already been |
| // checked. |
| if (PHIs.insert(PN)) |
| return AllUsesOfValueWillTrapIfNull(PN, PHIs); |
| } else if (isa<ICmpInst>(*UI) && |
| isa<ConstantPointerNull>(UI->getOperand(1))) { |
| // Ignore setcc X, null |
| } else { |
| //cerr << "NONTRAPPING USE: " << **UI; |
| 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(GlobalVariable *GV) { |
| for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI!=E; ++UI) |
| if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { |
| SmallPtrSet<PHINode*, 8> PHIs; |
| if (!AllUsesOfValueWillTrapIfNull(LI, PHIs)) |
| return false; |
| } else if (isa<StoreInst>(*UI)) { |
| // Ignore stores to the global. |
| } else { |
| // We don't know or understand this user, bail out. |
| //cerr << "UNKNOWN USER OF GLOBAL!: " << **UI; |
| 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)) { |
| if (I->getOperand(0) == V) { |
| // Calling through the pointer! Turn into a direct call, but be careful |
| // that the pointer is not also being passed as an argument. |
| I->setOperand(0, NewV); |
| Changed = true; |
| bool PassedAsArg = false; |
| for (unsigned i = 1, e = I->getNumOperands(); i != e; ++i) |
| if (I->getOperand(i) == V) { |
| PassedAsArg = true; |
| I->setOperand(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[0], |
| Idxs.size())); |
| 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) { |
| std::vector<LoadInst*> Loads; |
| bool Changed = false; |
| |
| // 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; ++GUI) |
| if (LoadInst *LI = dyn_cast<LoadInst>(*GUI)) { |
| Loads.push_back(LI); |
| Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); |
| } else { |
| // If we get here we could have stores, selects, or phi nodes whose values |
| // are loaded. |
| assert((isa<StoreInst>(*GUI) || isa<PHINode>(*GUI) || |
| isa<SelectInst>(*GUI) || isa<ConstantExpr>(*GUI)) && |
| "Only expect load and stores!"); |
| } |
| |
| if (Changed) { |
| DOUT << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV; |
| ++NumGlobUses; |
| } |
| |
| // Delete all of the loads we can, keeping track of whether we nuked them all! |
| bool AllLoadsGone = true; |
| while (!Loads.empty()) { |
| LoadInst *L = Loads.back(); |
| if (L->use_empty()) { |
| L->eraseFromParent(); |
| Changed = true; |
| } else { |
| AllLoadsGone = false; |
| } |
| Loads.pop_back(); |
| } |
| |
| // If we nuked all of the loads, then none of the stores are needed either, |
| // nor is the global. |
| if (AllLoadsGone) { |
| DOUT << " *** GLOBAL NOW DEAD!\n"; |
| CleanupConstantGlobalUsers(GV, 0); |
| if (GV->use_empty()) { |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| } |
| Changed = true; |
| } |
| return Changed; |
| } |
| |
| /// ConstantPropUsersOf - Walk the use list of V, constant folding all of the |
| /// instructions that are foldable. |
| static void ConstantPropUsersOf(Value *V) { |
| 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)) { |
| 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, |
| MallocInst *MI) { |
| DOUT << "PROMOTING MALLOC GLOBAL: " << *GV << " MALLOC = " << *MI; |
| ConstantInt *NElements = cast<ConstantInt>(MI->getArraySize()); |
| |
| if (NElements->getZExtValue() != 1) { |
| // If we have an array allocation, transform it to a single element |
| // allocation to make the code below simpler. |
| Type *NewTy = ArrayType::get(MI->getAllocatedType(), |
| NElements->getZExtValue()); |
| MallocInst *NewMI = |
| new MallocInst(NewTy, Constant::getNullValue(Type::Int32Ty), |
| MI->getAlignment(), MI->getName(), MI); |
| Value* Indices[2]; |
| Indices[0] = Indices[1] = Constant::getNullValue(Type::Int32Ty); |
| Value *NewGEP = GetElementPtrInst::Create(NewMI, Indices, Indices + 2, |
| NewMI->getName()+".el0", MI); |
| MI->replaceAllUsesWith(NewGEP); |
| MI->eraseFromParent(); |
| MI = NewMI; |
| } |
| |
| // Create the new global variable. The contents of the malloc'd memory is |
| // undefined, so initialize with an undef value. |
| Constant *Init = UndefValue::get(MI->getAllocatedType()); |
| GlobalVariable *NewGV = new GlobalVariable(MI->getAllocatedType(), false, |
| GlobalValue::InternalLinkage, Init, |
| GV->getName()+".body", |
| (Module *)NULL, |
| GV->isThreadLocal()); |
| // FIXME: This new global should have the alignment returned by malloc. Code |
| // could depend on malloc returning large alignment (on the mac, 16 bytes) but |
| // this would only guarantee some lower alignment. |
| GV->getParent()->getGlobalList().insert(GV, NewGV); |
| |
| // Anything that used the malloc now uses the global directly. |
| MI->replaceAllUsesWith(NewGV); |
| |
| 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::Int1Ty, false, GlobalValue::InternalLinkage, |
| ConstantInt::getFalse(), GV->getName()+".init", |
| (Module *)NULL, GV->isThreadLocal()); |
| bool InitBoolUsed = false; |
| |
| // Loop over all uses of GV, processing them in turn. |
| std::vector<StoreInst*> Stores; |
| while (!GV->use_empty()) |
| if (LoadInst *LI = dyn_cast<LoadInst>(GV->use_back())) { |
| while (!LI->use_empty()) { |
| Use &LoadUse = LI->use_begin().getUse(); |
| if (!isa<ICmpInst>(LoadUse.getUser())) |
| LoadUse = RepValue; |
| else { |
| ICmpInst *CI = cast<ICmpInst>(LoadUse.getUser()); |
| // Replace the cmp X, 0 with a use of the bool value. |
| Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", CI); |
| InitBoolUsed = true; |
| switch (CI->getPredicate()) { |
| default: assert(0 && "Unknown ICmp Predicate!"); |
| case ICmpInst::ICMP_ULT: |
| case ICmpInst::ICMP_SLT: |
| LV = ConstantInt::getFalse(); // X < null -> always false |
| break; |
| case ICmpInst::ICMP_ULE: |
| case ICmpInst::ICMP_SLE: |
| case ICmpInst::ICMP_EQ: |
| LV = BinaryOperator::CreateNot(LV, "notinit", CI); |
| break; |
| case ICmpInst::ICMP_NE: |
| case ICmpInst::ICMP_UGE: |
| case ICmpInst::ICMP_SGE: |
| case ICmpInst::ICMP_UGT: |
| case ICmpInst::ICMP_SGT: |
| break; // no change. |
| } |
| CI->replaceAllUsesWith(LV); |
| CI->eraseFromParent(); |
| } |
| } |
| LI->eraseFromParent(); |
| } else { |
| StoreInst *SI = cast<StoreInst>(GV->use_back()); |
| // The global is initialized when the store to it occurs. |
| new StoreInst(ConstantInt::getTrue(), InitBool, SI); |
| SI->eraseFromParent(); |
| } |
| |
| // If the initialization boolean was used, insert it, otherwise delete it. |
| if (!InitBoolUsed) { |
| while (!InitBool->use_empty()) // Delete initializations |
| cast<Instruction>(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(); |
| MI->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); |
| if (RepValue != NewGV) |
| ConstantPropUsersOf(RepValue); |
| |
| 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(Instruction *V, |
| GlobalVariable *GV, |
| SmallPtrSet<PHINode*, 8> &PHIs) { |
| for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){ |
| Instruction *Inst = dyn_cast<Instruction>(*UI); |
| if (Inst == 0) return false; |
| |
| if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) { |
| continue; // Fine, ignore. |
| } |
| |
| if (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. |
| } |
| |
| if (isa<GetElementPtrInst>(Inst)) { |
| if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs)) |
| return false; |
| continue; |
| } |
| |
| if (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 (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. |
| unsigned PredNo = Alloc->use_begin().getOperandNo()/2; |
| InsertPt = PN->getIncomingBlock(PredNo)->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(Value *V, |
| SmallPtrSet<PHINode*, 32> &LoadUsingPHIs) { |
| // We permit two users of the load: setcc comparing against the null |
| // pointer, and a getelementptr of a specific form. |
| for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;++UI){ |
| Instruction *User = cast<Instruction>(*UI); |
| |
| // Comparison against null is ok. |
| if (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 (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 (PHINode *PN = dyn_cast<PHINode>(User)) { |
| // If we have already recursively analyzed this PHI, then it is safe. |
| if (LoadUsingPHIs.insert(PN)) |
| continue; |
| |
| // Make sure all uses of the PHI are simple enough to transform. |
| if (!LoadUsesSimpleEnoughForHeapSRA(PN, LoadUsingPHIs)) |
| 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(GlobalVariable *GV, |
| MallocInst *MI) { |
| SmallPtrSet<PHINode*, 32> LoadUsingPHIs; |
| for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E; |
| ++UI) |
| if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) |
| if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs)) |
| return false; |
| |
| // 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<PHINode*, 32>::iterator I = LoadUsingPHIs.begin(), |
| E = LoadUsingPHIs.end(); I != E; ++I) { |
| 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 == MI) continue; |
| |
| if (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 (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" + utostr(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. |
| const StructType *ST = |
| cast<StructType>(cast<PointerType>(PN->getType())->getElementType()); |
| |
| Result =PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)), |
| PN->getName()+".f"+utostr(FieldNo), PN); |
| PHIsToRewrite.push_back(std::make_pair(PN, FieldNo)); |
| } else { |
| assert(0 && "Unknown usable value"); |
| Result = 0; |
| } |
| |
| 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->getPredicate(), NPtr, |
| Constant::getNullValue(NPtr->getType()), |
| SCI->getName(), SCI); |
| 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.begin(), GEPIdx.end(), |
| 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); |
| bool Inserted; |
| DenseMap<Value*, std::vector<Value*> >::iterator InsertPos; |
| tie(InsertPos, Inserted) = |
| InsertedScalarizedValues.insert(std::make_pair(PN, std::vector<Value*>())); |
| if (!Inserted) 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 - MI is an allocation of an array of structures. Break |
| /// it up into multiple allocations of arrays of the fields. |
| static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, MallocInst *MI){ |
| DOUT << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *MI; |
| const StructType *STy = cast<StructType>(MI->getAllocatedType()); |
| |
| // 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(MI, GV); |
| |
| // Okay, at this point, there are no users of the malloc. Insert N |
| // new mallocs at the same place as MI, and N globals. |
| std::vector<Value*> FieldGlobals; |
| std::vector<MallocInst*> FieldMallocs; |
| |
| for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ |
| const Type *FieldTy = STy->getElementType(FieldNo); |
| const Type *PFieldTy = PointerType::getUnqual(FieldTy); |
| |
| GlobalVariable *NGV = |
| new GlobalVariable(PFieldTy, false, GlobalValue::InternalLinkage, |
| Constant::getNullValue(PFieldTy), |
| GV->getName() + ".f" + utostr(FieldNo), GV, |
| GV->isThreadLocal()); |
| FieldGlobals.push_back(NGV); |
| |
| MallocInst *NMI = new MallocInst(FieldTy, MI->getArraySize(), |
| MI->getName() + ".f" + utostr(FieldNo),MI); |
| FieldMallocs.push_back(NMI); |
| new StoreInst(NMI, NGV, MI); |
| } |
| |
| // 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; } |
| // } |
| Value *RunningOr = 0; |
| for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { |
| Value *Cond = new ICmpInst(ICmpInst::ICMP_EQ, FieldMallocs[i], |
| Constant::getNullValue(FieldMallocs[i]->getType()), |
| "isnull", MI); |
| if (!RunningOr) |
| RunningOr = Cond; // First seteq |
| else |
| RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", MI); |
| } |
| |
| // Split the basic block at the old malloc. |
| BasicBlock *OrigBB = MI->getParent(); |
| BasicBlock *ContBB = OrigBB->splitBasicBlock(MI, "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("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(ICmpInst::ICMP_NE, GVVal, |
| Constant::getNullValue(GVVal->getType()), |
| "tmp", NullPtrBlock); |
| BasicBlock *FreeBlock = BasicBlock::Create("free_it", OrigBB->getParent()); |
| BasicBlock *NextBlock = BasicBlock::Create("next", OrigBB->getParent()); |
| BranchInst::Create(FreeBlock, NextBlock, Cmp, NullPtrBlock); |
| |
| // Fill in FreeBlock. |
| new FreeInst(GVVal, FreeBlock); |
| new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], |
| FreeBlock); |
| BranchInst::Create(NextBlock, FreeBlock); |
| |
| NullPtrBlock = NextBlock; |
| } |
| |
| BranchInst::Create(ContBB, NullPtrBlock); |
| |
| // MI is no longer needed, remove it. |
| MI->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) { |
| const 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, |
| MallocInst *MI, |
| Module::global_iterator &GVI, |
| TargetData &TD) { |
| // If this is a malloc of an abstract type, don't touch it. |
| if (!MI->getAllocatedType()->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 setcc'd, and |
| // GEP'd. These are all things we could transform to using the global |
| // for. |
| { |
| SmallPtrSet<PHINode*, 8> PHIs; |
| if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(MI, 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. |
| if (ConstantInt *NElements = dyn_cast<ConstantInt>(MI->getArraySize())) { |
| // 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.getTypePaddedSize(MI->getAllocatedType()) < 2048) { |
| GVI = OptimizeGlobalAddressOfMalloc(GV, MI); |
| 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. |
| const Type *AllocTy = MI->getAllocatedType(); |
| |
| // 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 (!MI->isArrayAllocation()) |
| if (const ArrayType *AT = dyn_cast<ArrayType>(AllocTy)) |
| AllocTy = AT->getElementType(); |
| |
| if (const StructType *AllocSTy = dyn_cast<StructType>(AllocTy)) { |
| // This the structure has an unreasonable number of fields, leave it |
| // alone. |
| if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 && |
| AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, MI)) { |
| |
| // 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 (const ArrayType *AT = dyn_cast<ArrayType>(MI->getAllocatedType())) { |
| MallocInst *NewMI = |
| new MallocInst(AllocSTy, |
| ConstantInt::get(Type::Int32Ty, AT->getNumElements()), |
| "", MI); |
| NewMI->takeName(MI); |
| Value *Cast = new BitCastInst(NewMI, MI->getType(), "tmp", MI); |
| MI->replaceAllUsesWith(Cast); |
| MI->eraseFromParent(); |
| MI = NewMI; |
| } |
| |
| GVI = PerformHeapAllocSRoA(GV, MI); |
| 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, |
| Module::global_iterator &GVI, |
| TargetData &TD) { |
| // 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 (isa<PointerType>(GV->getInitializer()->getType()) && |
| 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)) |
| return true; |
| } else if (MallocInst *MI = dyn_cast<MallocInst>(StoredOnceVal)) { |
| if (TryToOptimizeStoreOfMallocToGlobal(GV, MI, GVI, TD)) |
| 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) { |
| const Type *GVElType = GV->getType()->getElementType(); |
| |
| // If GVElType is already i1, it is already shrunk. If the type of the GV is |
| // an FP value or vector, don't do this optimization because a select between |
| // them is very expensive and unlikely to lead to later simplification. |
| if (GVElType == Type::Int1Ty || GVElType->isFloatingPoint() || |
| isa<VectorType>(GVElType)) |
| 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) |
| if (!isa<LoadInst>(I) && !isa<StoreInst>(I)) |
| return false; |
| |
| DOUT << " *** SHRINKING TO BOOL: " << *GV; |
| |
| // Create the new global, initializing it to false. |
| GlobalVariable *NewGV = new GlobalVariable(Type::Int1Ty, false, |
| GlobalValue::InternalLinkage, ConstantInt::getFalse(), |
| GV->getName()+".b", |
| (Module *)NULL, |
| GV->isThreadLocal()); |
| GV->getParent()->getGlobalList().insert(GV, NewGV); |
| |
| Constant *InitVal = GV->getInitializer(); |
| assert(InitVal->getType() != Type::Int1Ty && "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::Int1Ty, 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're 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", 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, 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", 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; |
| } |
| |
| |
| /// 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) { |
| SmallPtrSet<PHINode*, 16> PHIUsers; |
| GlobalStatus GS; |
| GV->removeDeadConstantUsers(); |
| |
| if (GV->use_empty()) { |
| DOUT << "GLOBAL DEAD: " << *GV; |
| GV->eraseFromParent(); |
| ++NumDeleted; |
| return true; |
| } |
| |
| if (!AnalyzeGlobal(GV, GS, PHIUsers)) { |
| #if 0 |
| cerr << "Global: " << *GV; |
| cerr << " isLoaded = " << GS.isLoaded << "\n"; |
| cerr << " StoredType = "; |
| switch (GS.StoredType) { |
| case GlobalStatus::NotStored: cerr << "NEVER STORED\n"; break; |
| case GlobalStatus::isInitializerStored: cerr << "INIT STORED\n"; break; |
| case GlobalStatus::isStoredOnce: cerr << "STORED ONCE\n"; break; |
| case GlobalStatus::isStored: cerr << "stored\n"; break; |
| } |
| if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue) |
| cerr << " StoredOnceValue = " << *GS.StoredOnceValue << "\n"; |
| if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions) |
| cerr << " AccessingFunction = " << GS.AccessingFunction->getName() |
| << "\n"; |
| cerr << " HasMultipleAccessingFunctions = " |
| << GS.HasMultipleAccessingFunctions << "\n"; |
| cerr << " HasNonInstructionUser = " << GS.HasNonInstructionUser<<"\n"; |
| cerr << "\n"; |
| #endif |
| |
| // 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 (!GS.HasMultipleAccessingFunctions && |
| GS.AccessingFunction && !GS.HasNonInstructionUser && |
| GV->getType()->getElementType()->isSingleValueType() && |
| GS.AccessingFunction->getName() == "main" && |
| GS.AccessingFunction->hasExternalLinkage()) { |
| DOUT << "LOCALIZING GLOBAL: " << *GV; |
| Instruction* FirstI = GS.AccessingFunction->getEntryBlock().begin(); |
| const 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) { |
| DOUT << "GLOBAL NEVER LOADED: " << *GV; |
| |
| // Delete any stores we can find to the global. We may not be able to |
| // make it completely dead though. |
| bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer()); |
| |
| // 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) { |
| DOUT << "MARKING CONSTANT: " << *GV; |
| GV->setConstant(true); |
| |
| // Clean up any obviously simplifiable users now. |
| CleanupConstantGlobalUsers(GV, GV->getInitializer()); |
| |
| // If the global is dead now, just nuke it. |
| if (GV->use_empty()) { |
| DOUT << " *** 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 (GlobalVariable *FirstNewGV = SRAGlobal(GV, |
| getAnalysis<TargetData>())) { |
| 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 an undef 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()); |
| |
| if (GV->use_empty()) { |
| DOUT << " *** 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, GVI, |
| getAnalysis<TargetData>())) |
| 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; |
| } |
| |
| /// OnlyCalledDirectly - Return true if the specified function is only called |
| /// directly. In other words, its address is never taken. |
| static bool OnlyCalledDirectly(Function *F) { |
| for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ |
| Instruction *User = dyn_cast<Instruction>(*UI); |
| if (!User) return false; |
| if (!isa<CallInst>(User) && !isa<InvokeInst>(User)) return false; |
| |
| // See if the function address is passed as an argument. |
| for (User::op_iterator i = User->op_begin() + 1, e = User->op_end(); |
| i != e; ++i) |
| if (*i == F) return false; |
| } |
| return true; |
| } |
| |
| /// 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){ |
| CallSite User(cast<Instruction>(*UI)); |
| User.setCallingConv(CallingConv::Fast); |
| } |
| } |
| |
| static AttrListPtr StripNest(const AttrListPtr &Attrs) { |
| for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) { |
| if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0) |
| continue; |
| |
| // There can be only one. |
| return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest); |
| } |
| |
| return Attrs; |
| } |
| |
| static void RemoveNestAttribute(Function *F) { |
| F->setAttributes(StripNest(F->getAttributes())); |
| for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){ |
| CallSite User(cast<Instruction>(*UI)); |
| User.setAttributes(StripNest(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++; |
| F->removeDeadConstantUsers(); |
| if (F->use_empty() && (F->hasInternalLinkage() || |
| F->hasLinkOnceLinkage())) { |
| M.getFunctionList().erase(F); |
| Changed = true; |
| ++NumFnDeleted; |
| } else if (F->hasInternalLinkage()) { |
| if (F->getCallingConv() == CallingConv::C && !F->isVarArg() && |
| OnlyCalledDirectly(F)) { |
| // 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) && |
| OnlyCalledDirectly(F)) { |
| // 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++; |
| if (!GV->isConstant() && GV->hasInternalLinkage() && |
| GV->hasInitializer()) |
| Changed |= ProcessInternalGlobal(GV, GVI); |
| } |
| return Changed; |
| } |
| |
| /// FindGlobalCtors - Find the llvm.globalctors list, verifying that all |
| /// initializers have an init priority of 65535. |
| GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) { |
| for (Module::global_iterator I = M.global_begin(), E = M.global_end(); |
| I != E; ++I) |
| if (I->getName() == "llvm.global_ctors") { |
| // Found it, verify it's an array of { int, void()* }. |
| const ArrayType *ATy =dyn_cast<ArrayType>(I->getType()->getElementType()); |
| if (!ATy) return 0; |
| const StructType *STy = dyn_cast<StructType>(ATy->getElementType()); |
| if (!STy || STy->getNumElements() != 2 || |
| STy->getElementType(0) != Type::Int32Ty) return 0; |
| const PointerType *PFTy = dyn_cast<PointerType>(STy->getElementType(1)); |
| if (!PFTy) return 0; |
| const FunctionType *FTy = dyn_cast<FunctionType>(PFTy->getElementType()); |
| if (!FTy || FTy->getReturnType() != Type::VoidTy || FTy->isVarArg() || |
| FTy->getNumParams() != 0) |
| return 0; |
| |
| // Verify that the initializer is simple enough for us to handle. |
| if (!I->hasInitializer()) return 0; |
| ConstantArray *CA = dyn_cast<ConstantArray>(I->getInitializer()); |
| if (!CA) return 0; |
| for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) |
| if (ConstantStruct *CS = dyn_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 = dyn_cast<ConstantInt>(CS->getOperand(0)); |
| if (!CI || CI->getZExtValue() != 65535) |
| return 0; |
| } else { |
| return 0; |
| } |
| |
| return I; |
| } |
| return 0; |
| } |
| |
| /// 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) { |
| 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. |
| std::vector<Constant*> CSVals; |
| CSVals.push_back(ConstantInt::get(Type::Int32Ty, 65535)); |
| CSVals.push_back(0); |
| |
| // 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 { |
| const Type *FTy = FunctionType::get(Type::VoidTy, |
| std::vector<const Type*>(), false); |
| const PointerType *PFTy = PointerType::getUnqual(FTy); |
| CSVals[1] = Constant::getNullValue(PFTy); |
| CSVals[0] = ConstantInt::get(Type::Int32Ty, 2147483647); |
| } |
| CAList.push_back(ConstantStruct::get(CSVals)); |
| } |
| |
| // Create the array initializer. |
| const Type *StructTy = |
| cast<ArrayType>(GCL->getType()->getElementType())->getElementType(); |
| 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, "", |
| (Module *)NULL, |
| GCL->isThreadLocal()); |
| 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 Constant *getVal(DenseMap<Value*, Constant*> &ComputedValues, |
| Value *V) { |
| if (Constant *CV = dyn_cast<Constant>(V)) return CV; |
| Constant *R = ComputedValues[V]; |
| assert(R && "Reference to an uncomputed value!"); |
| return R; |
| } |
| |
| /// isSimpleEnoughPointerToCommit - Return true if this constant is simple |
| /// enough for us to understand. In particular, if it is a cast of something, |
| /// 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) { |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) { |
| if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) |
| return false; // do not allow weak/linkonce/dllimport/dllexport linkage. |
| return !GV->isDeclaration(); // reject external globals. |
| } |
| if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) |
| // Handle a constantexpr gep. |
| if (CE->getOpcode() == Instruction::GetElementPtr && |
| isa<GlobalVariable>(CE->getOperand(0))) { |
| GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); |
| if (!GV->hasExternalLinkage() && !GV->hasInternalLinkage()) |
| return false; // do not allow weak/linkonce/dllimport/dllexport linkage. |
| return GV->hasInitializer() && |
| ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); |
| } |
| 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; |
| } |
| |
| if (const StructType *STy = dyn_cast<StructType>(Init->getType())) { |
| std::vector<Constant*> Elts; |
| |
| // Break up the constant into its elements. |
| if (ConstantStruct *CS = dyn_cast<ConstantStruct>(Init)) { |
| for (User::op_iterator i = CS->op_begin(), e = CS->op_end(); i != e; ++i) |
| Elts.push_back(cast<Constant>(*i)); |
| } else if (isa<ConstantAggregateZero>(Init)) { |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) |
| Elts.push_back(Constant::getNullValue(STy->getElementType(i))); |
| } else if (isa<UndefValue>(Init)) { |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) |
| Elts.push_back(UndefValue::get(STy->getElementType(i))); |
| } else { |
| assert(0 && "This code is out of sync with " |
| " ConstantFoldLoadThroughGEPConstantExpr"); |
| } |
| |
| // 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(&Elts[0], Elts.size(), STy->isPacked()); |
| } else { |
| ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); |
| const ArrayType *ATy = cast<ArrayType>(Init->getType()); |
| |
| // Break up the array into elements. |
| std::vector<Constant*> Elts; |
| if (ConstantArray *CA = dyn_cast<ConstantArray>(Init)) { |
| for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) |
| Elts.push_back(cast<Constant>(*i)); |
| } else if (isa<ConstantAggregateZero>(Init)) { |
| Constant *Elt = Constant::getNullValue(ATy->getElementType()); |
| Elts.assign(ATy->getNumElements(), Elt); |
| } else if (isa<UndefValue>(Init)) { |
| Constant *Elt = UndefValue::get(ATy->getElementType()); |
| Elts.assign(ATy->getNumElements(), Elt); |
| } else { |
| assert(0 && "This code is out of sync with " |
| " ConstantFoldLoadThroughGEPConstantExpr"); |
| } |
| |
| assert(CI->getZExtValue() < ATy->getNumElements()); |
| Elts[CI->getZExtValue()] = |
| EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); |
| return ConstantArray::get(ATy, 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)); |
| |
| Constant *Init = GV->getInitializer(); |
| Init = EvaluateStoreInto(Init, Val, CE, 2); |
| GV->setInitializer(Init); |
| } |
| |
| /// 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. |
| static Constant *ComputeLoadResult(Constant *P, |
| const DenseMap<Constant*, Constant*> &Memory) { |
| // 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 = Memory.find(P); |
| if (I != Memory.end()) return I->second; |
| |
| // Access it. |
| if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) { |
| if (GV->hasInitializer()) |
| 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->hasInitializer()) |
| return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); |
| } |
| |
| return 0; // don't know how to evaluate. |
| } |
| |
| /// 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. |
| static bool EvaluateFunction(Function *F, Constant *&RetVal, |
| const std::vector<Constant*> &ActualArgs, |
| std::vector<Function*> &CallStack, |
| DenseMap<Constant*, Constant*> &MutatedMemory, |
| std::vector<GlobalVariable*> &AllocaTmps) { |
| // 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); |
| |
| /// Values - As we compute SSA register values, we store their contents here. |
| DenseMap<Value*, Constant*> Values; |
| |
| // 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) |
| Values[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; |
| |
| // CurInst - The current instruction we're evaluating. |
| BasicBlock::iterator CurInst = F->begin()->begin(); |
| |
| // This is the main evaluation loop. |
| while (1) { |
| Constant *InstResult = 0; |
| |
| if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) { |
| if (SI->isVolatile()) return false; // no volatile accesses. |
| Constant *Ptr = getVal(Values, SI->getOperand(1)); |
| if (!isSimpleEnoughPointerToCommit(Ptr)) |
| // If this is too complex for us to commit, reject it. |
| return false; |
| Constant *Val = getVal(Values, SI->getOperand(0)); |
| MutatedMemory[Ptr] = Val; |
| } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) { |
| InstResult = ConstantExpr::get(BO->getOpcode(), |
| getVal(Values, BO->getOperand(0)), |
| getVal(Values, BO->getOperand(1))); |
| } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) { |
| InstResult = ConstantExpr::getCompare(CI->getPredicate(), |
| getVal(Values, CI->getOperand(0)), |
| getVal(Values, CI->getOperand(1))); |
| } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) { |
| InstResult = ConstantExpr::getCast(CI->getOpcode(), |
| getVal(Values, CI->getOperand(0)), |
| CI->getType()); |
| } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) { |
| InstResult = ConstantExpr::getSelect(getVal(Values, SI->getOperand(0)), |
| getVal(Values, SI->getOperand(1)), |
| getVal(Values, SI->getOperand(2))); |
| } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) { |
| Constant *P = getVal(Values, 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(Values, *i)); |
| InstResult = ConstantExpr::getGetElementPtr(P, &GEPOps[0], GEPOps.size()); |
| } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) { |
| if (LI->isVolatile()) return false; // no volatile accesses. |
| InstResult = ComputeLoadResult(getVal(Values, LI->getOperand(0)), |
| MutatedMemory); |
| if (InstResult == 0) return false; // Could not evaluate load. |
| } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) { |
| if (AI->isArrayAllocation()) return false; // Cannot handle array allocs. |
| const Type *Ty = AI->getType()->getElementType(); |
| AllocaTmps.push_back(new GlobalVariable(Ty, false, |
| GlobalValue::InternalLinkage, |
| UndefValue::get(Ty), |
| AI->getName())); |
| InstResult = AllocaTmps.back(); |
| } else if (CallInst *CI = dyn_cast<CallInst>(CurInst)) { |
| // Cannot handle inline asm. |
| if (isa<InlineAsm>(CI->getOperand(0))) return false; |
| |
| // Resolve function pointers. |
| Function *Callee = dyn_cast<Function>(getVal(Values, CI->getOperand(0))); |
| if (!Callee) return false; // Cannot resolve. |
| |
| std::vector<Constant*> Formals; |
| for (User::op_iterator i = CI->op_begin() + 1, e = CI->op_end(); |
| i != e; ++i) |
| Formals.push_back(getVal(Values, *i)); |
| |
| if (Callee->isDeclaration()) { |
| // If this is a function we can constant fold, do it. |
| if (Constant *C = ConstantFoldCall(Callee, &Formals[0], |
| Formals.size())) { |
| InstResult = C; |
| } else { |
| return false; |
| } |
| } else { |
| if (Callee->getFunctionType()->isVarArg()) |
| return false; |
| |
| Constant *RetVal; |
| |
| // Execute the call, if successful, use the return value. |
| if (!EvaluateFunction(Callee, RetVal, Formals, CallStack, |
| MutatedMemory, AllocaTmps)) |
| return false; |
| InstResult = RetVal; |
| } |
| } else if (isa<TerminatorInst>(CurInst)) { |
| BasicBlock *NewBB = 0; |
| if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) { |
| if (BI->isUnconditional()) { |
| NewBB = BI->getSuccessor(0); |
| } else { |
| ConstantInt *Cond = |
| dyn_cast<ConstantInt>(getVal(Values, BI->getCondition())); |
| if (!Cond) return false; // Cannot determine. |
| |
| NewBB = BI->getSuccessor(!Cond->getZExtValue()); |
| } |
| } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) { |
| ConstantInt *Val = |
| dyn_cast<ConstantInt>(getVal(Values, SI->getCondition())); |
| if (!Val) return false; // Cannot determine. |
| NewBB = SI->getSuccessor(SI->findCaseValue(Val)); |
| } else if (ReturnInst *RI = dyn_cast<ReturnInst>(CurInst)) { |
| if (RI->getNumOperands()) |
| RetVal = getVal(Values, RI->getOperand(0)); |
| |
| CallStack.pop_back(); // return from fn. |
| return true; // We succeeded at evaluating this ctor! |
| } else { |
| // invoke, unwind, unreachable. |
| return false; // Cannot handle this terminator. |
| } |
| |
| // 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(NewBB)) |
| 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. |
| BasicBlock *OldBB = CurInst->getParent(); |
| CurInst = NewBB->begin(); |
| PHINode *PN; |
| for (; (PN = dyn_cast<PHINode>(CurInst)); ++CurInst) |
| Values[PN] = getVal(Values, PN->getIncomingValueForBlock(OldBB)); |
| |
| // Do NOT increment CurInst. We know that the terminator had no value. |
| continue; |
| } else { |
| // Did not know how to evaluate this! |
| return false; |
| } |
| |
| if (!CurInst->use_empty()) |
| Values[CurInst] = InstResult; |
| |
| // Advance program counter. |
| ++CurInst; |
| } |
| } |
| |
| /// EvaluateStaticConstructor - Evaluate static constructors in the function, if |
| /// we can. Return true if we can, false otherwise. |
| static bool EvaluateStaticConstructor(Function *F) { |
| /// 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. |
| std::vector<GlobalVariable*> AllocaTmps; |
| |
| /// CallStack - This is used to detect recursion. In pathological situations |
| /// we could hit exponential behavior, but at least there is nothing |
| /// unbounded. |
| std::vector<Function*> CallStack; |
| |
| // Call the function. |
| Constant *RetValDummy; |
| bool EvalSuccess = EvaluateFunction(F, RetValDummy, std::vector<Constant*>(), |
| CallStack, MutatedMemory, AllocaTmps); |
| if (EvalSuccess) { |
| // We succeeded at evaluation: commit the result. |
| DOUT << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" |
| << F->getName() << "' to " << MutatedMemory.size() |
| << " stores.\n"; |
| for (DenseMap<Constant*, Constant*>::iterator I = MutatedMemory.begin(), |
| E = MutatedMemory.end(); I != E; ++I) |
| CommitValueTo(I->second, I->first); |
| } |
| |
| // At this point, we are done interpreting. If we created any 'alloca' |
| // temporaries, release them now. |
| 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; |
| } |
| |
| 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; |
| } |
| |
| // We cannot simplify external ctor functions. |
| if (F->empty()) continue; |
| |
| // If we can evaluate the ctor at compile time, do. |
| if (EvaluateStaticConstructor(F)) { |
| Ctors.erase(Ctors.begin()+i); |
| MadeChange = true; |
| --i; |
| ++NumCtorsEvaluated; |
| continue; |
| } |
| } |
| |
| if (!MadeChange) return false; |
| |
| GCL = InstallGlobalCtors(GCL, Ctors); |
| return true; |
| } |
| |
| bool GlobalOpt::ResolveAliases(Module &M) { |
| bool Changed = false; |
| |
| for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); |
| I != E; ++I) { |
| if (I->use_empty()) |
| continue; |
| |
| if (const GlobalValue *GV = I->resolveAliasedGlobal()) |
| if (GV != I) { |
| I->replaceAllUsesWith(const_cast<GlobalValue*>(GV)); |
| Changed = true; |
| } |
| } |
| |
| return Changed; |
| } |
| |
| bool GlobalOpt::runOnModule(Module &M) { |
| bool Changed = false; |
| |
| // Try to find the llvm.globalctors list. |
| GlobalVariable *GlobalCtors = FindGlobalCtors(M); |
| |
| 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 |= ResolveAliases(M); |
| Changed |= LocalChange; |
| } |
| |
| // TODO: Move all global ctors functions to the end of the module for code |
| // layout. |
| |
| return Changed; |
| } |