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Diffstat (limited to 'lib/Transforms/IPO/GlobalOpt.cpp')
| -rw-r--r-- | lib/Transforms/IPO/GlobalOpt.cpp | 2564 |
1 files changed, 2564 insertions, 0 deletions
diff --git a/lib/Transforms/IPO/GlobalOpt.cpp b/lib/Transforms/IPO/GlobalOpt.cpp new file mode 100644 index 0000000..ac91631 --- /dev/null +++ b/lib/Transforms/IPO/GlobalOpt.cpp @@ -0,0 +1,2564 @@ +//===- 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/Analysis/MemoryBuiltins.h" +#include "llvm/Target/TargetData.h" +#include "llvm/Support/CallSite.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/GetElementPtrTypeIterator.h" +#include "llvm/Support/MathExtras.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/ADT/DenseMap.h" +#include "llvm/ADT/SmallPtrSet.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/ADT/Statistic.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"); +STATISTIC(NumAliasesResolved, "Number of global aliases resolved"); +STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated"); + +namespace { + struct GlobalOpt : public ModulePass { + virtual void getAnalysisUsage(AnalysisUsage &AU) const { + } + 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 OptimizeGlobalAliases(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 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) {} +}; + +} + +// SafeToDestroyConstant - It is safe to destroy a constant iff it is only used +// by constants itself. Note that constants cannot be cyclic, so this test is +// pretty easy to implement recursively. +// +static bool SafeToDestroyConstant(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 (!SafeToDestroyConstant(CU)) return false; + } else + return false; + return true; +} + + +/// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus +/// structure. If the global has its address taken, return true to indicate we +/// can't do anything with it. +/// +static bool AnalyzeGlobal(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<MemTransferInst>(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 (!SafeToDestroyConstant(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 (SafeToDestroyConstant(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 SafeToDestroyConstant(C); + + Instruction *I = dyn_cast<Instruction>(V); + if (!I) return false; + + // Loads are ok. + if (isa<LoadInst>(I)) return true; + + // Stores *to* the pointer are ok. + if (StoreInst *SI = dyn_cast<StoreInst>(I)) + return SI->getOperand(0) != V; + + // Otherwise, it must be a GEP. + GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I); + if (GEPI == 0) return false; + + if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) || + !cast<Constant>(GEPI->getOperand(1))->isNullValue()) + return false; + + for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end(); + I != E; ++I) + if (!isSafeSROAElementUse(*I)) + return false; + return true; +} + + +/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value. +/// Look at it and its uses and decide whether it is safe to SROA this global. +/// +static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) { + // The user of the global must be a GEP Inst or a ConstantExpr GEP. + if (!isa<GetElementPtrInst>(U) && + (!isa<ConstantExpr>(U) || + cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr)) + return false; + + // Check to see if this ConstantExpr GEP is SRA'able. In particular, we + // don't like < 3 operand CE's, and we don't like non-constant integer + // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some + // value of C. + if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) || + !cast<Constant>(U->getOperand(1))->isNullValue() || + !isa<ConstantInt>(U->getOperand(2))) + return false; + + gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U); + ++GEPI; // Skip over the pointer index. + + // If this is a use of an array allocation, do a bit more checking for sanity. + if (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; + ++GEPI) { + uint64_t NumElements; + if (const ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI)) + NumElements = SubArrayTy->getNumElements(); + else if (const VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI)) + NumElements = SubVectorTy->getNumElements(); + else { + assert(isa<StructType>(*GEPI) && + "Indexed GEP type is not array, vector, or struct!"); + continue; + } + + ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand()); + if (!IdxVal || IdxVal->getZExtValue() >= NumElements) + return false; + } + } + + for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I) + if (!isSafeSROAElementUse(*I)) + return false; + return true; +} + +/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it +/// is safe for us to perform this transformation. +/// +static bool GlobalUsersSafeToSRA(GlobalValue *GV) { + for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); + UI != E; ++UI) { + if (!IsUserOfGlobalSafeForSRA(*UI, GV)) + return false; + } + return true; +} + + +/// SRAGlobal - Perform scalar replacement of aggregates on the specified global +/// variable. This opens the door for other optimizations by exposing the +/// behavior of the program in a more fine-grained way. We have determined that +/// this transformation is safe already. We return the first global variable we +/// insert so that the caller can reprocess it. +static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) { + // Make sure this global only has simple uses that we can SRA. + if (!GlobalUsersSafeToSRA(GV)) + return 0; + + assert(GV->hasLocalLinkage() && !GV->isConstant()); + Constant *Init = GV->getInitializer(); + 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::getInt32Ty(STy->getContext()), i)); + assert(In && "Couldn't get element of initializer?"); + GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false, + GlobalVariable::InternalLinkage, + In, GV->getName()+"."+Twine(i), + GV->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.getTypeAllocSize(STy->getElementType()); + unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType()); + for (unsigned i = 0, e = NumElements; i != e; ++i) { + Constant *In = getAggregateConstantElement(Init, + ConstantInt::get(Type::getInt32Ty(Init->getContext()), i)); + assert(In && "Couldn't get element of initializer?"); + + GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false, + GlobalVariable::InternalLinkage, + In, GV->getName()+"."+Twine(i), + 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; + + DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV); + + Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext())); + + // Loop over all of the uses of the global, replacing the constantexpr geps, + // with smaller constantexpr geps or direct references. + while (!GV->use_empty()) { + User *GEP = GV->use_back(); + assert(((isa<ConstantExpr>(GEP) && + cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)|| + isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!"); + + // Ignore the 1th operand, which has to be zero or else the program is quite + // broken (undefined). Get the 2nd operand, which is the structure or array + // index. + unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); + if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access. + + Value *NewPtr = NewGlobals[Val]; + + // Form a shorter GEP if needed. + if (GEP->getNumOperands() > 3) { + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) { + SmallVector<Constant*, 8> Idxs; + Idxs.push_back(NullInt); + for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i) + Idxs.push_back(CE->getOperand(i)); + NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), + &Idxs[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()+"."+Twine(Val),GEPI); + } + } + GEP->replaceAllUsesWith(NewPtr); + + if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP)) + GEPI->eraseFromParent(); + else + cast<ConstantExpr>(GEP)->destroyConstant(); + } + + // Delete the old global, now that it is dead. + Globals.erase(GV); + ++NumSRA; + + // Loop over the new globals array deleting any globals that are obviously + // dead. This can arise due to scalarization of a structure or an array that + // has elements that are dead. + unsigned FirstGlobal = 0; + for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i) + if (NewGlobals[i]->use_empty()) { + Globals.erase(NewGlobals[i]); + if (FirstGlobal == i) ++FirstGlobal; + } + + return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0; +} + +/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified +/// value will trap if the value is dynamically null. PHIs keeps track of any +/// phi nodes we've seen to avoid reprocessing them. +static bool AllUsesOfValueWillTrapIfNull(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) && !AllUsesOfValueWillTrapIfNull(PN, PHIs)) + return false; + } 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) { + bool Changed = false; + + // Keep track of whether we are able to remove all the uses of the global + // other than the store that defines it. + bool AllNonStoreUsesGone = true; + + // Replace all uses of loads with uses of uses of the stored value. + for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){ + User *GlobalUser = *GUI++; + if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) { + Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); + // If we were able to delete all uses of the loads + if (LI->use_empty()) { + LI->eraseFromParent(); + Changed = true; + } else { + AllNonStoreUsesGone = false; + } + } else if (isa<StoreInst>(GlobalUser)) { + // Ignore the store that stores "LV" to the global. + assert(GlobalUser->getOperand(1) == GV && + "Must be storing *to* the global"); + } else { + AllNonStoreUsesGone = false; + + // If we get here we could have other crazy uses that are transitively + // loaded. + assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) || + isa<ConstantExpr>(GlobalUser)) && "Only expect load and stores!"); + } + } + + if (Changed) { + DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV); + ++NumGlobUses; + } + + // If we nuked all of the loads, then none of the stores are needed either, + // nor is the global. + if (AllNonStoreUsesGone) { + DEBUG(dbgs() << " *** 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, + CallInst *CI, + const Type *AllocTy, + Value* NElems, + TargetData* TD) { + DEBUG(dbgs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI << '\n'); + + const Type *IntPtrTy = TD->getIntPtrType(GV->getContext()); + + // CI has either 0 or 1 bitcast uses (getMallocType() would otherwise have + // returned NULL and we would not be here). + BitCastInst *BCI = NULL; + for (Value::use_iterator UI = CI->use_begin(), E = CI->use_end(); UI != E; ) + if ((BCI = dyn_cast<BitCastInst>(cast<Instruction>(*UI++)))) + break; + + ConstantInt *NElements = cast<ConstantInt>(NElems); + 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(AllocTy, NElements->getZExtValue()); + unsigned TypeSize = TD->getTypeAllocSize(NewTy); + if (const StructType *ST = dyn_cast<StructType>(NewTy)) + TypeSize = TD->getStructLayout(ST)->getSizeInBytes(); + Instruction *NewCI = CallInst::CreateMalloc(CI, IntPtrTy, NewTy, + ConstantInt::get(IntPtrTy, TypeSize)); + Value* Indices[2]; + Indices[0] = Indices[1] = Constant::getNullValue(IntPtrTy); + Value *NewGEP = GetElementPtrInst::Create(NewCI, Indices, Indices + 2, + NewCI->getName()+".el0", CI); + Value *Cast = new BitCastInst(NewGEP, CI->getType(), "el0", CI); + if (BCI) BCI->replaceAllUsesWith(NewGEP); + CI->replaceAllUsesWith(Cast); + if (BCI) BCI->eraseFromParent(); + CI->eraseFromParent(); + BCI = dyn_cast<BitCastInst>(NewCI); + CI = BCI ? extractMallocCallFromBitCast(BCI) : cast<CallInst>(NewCI); + } + + // Create the new global variable. The contents of the malloc'd memory is + // undefined, so initialize with an undef value. + const Type *MAT = getMallocAllocatedType(CI); + Constant *Init = UndefValue::get(MAT); + GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(), + MAT, false, + GlobalValue::InternalLinkage, Init, + GV->getName()+".body", + GV, + GV->isThreadLocal()); + + // Anything that used the malloc or its bitcast now uses the global directly. + if (BCI) BCI->replaceAllUsesWith(NewGV); + CI->replaceAllUsesWith(new BitCastInst(NewGV, CI->getType(), "newgv", CI)); + + Constant *RepValue = NewGV; + if (NewGV->getType() != GV->getType()->getElementType()) + RepValue = ConstantExpr::getBitCast(RepValue, + GV->getType()->getElementType()); + + // If there is a comparison against null, we will insert a global bool to + // keep track of whether the global was initialized yet or not. + GlobalVariable *InitBool = + new GlobalVariable(Type::getInt1Ty(GV->getContext()), false, + GlobalValue::InternalLinkage, + ConstantInt::getFalse(GV->getContext()), + GV->getName()+".init", GV->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 *ICI = cast<ICmpInst>(LoadUse.getUser()); + // Replace the cmp X, 0 with a use of the bool value. + Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", ICI); + InitBoolUsed = true; + switch (ICI->getPredicate()) { + default: llvm_unreachable("Unknown ICmp Predicate!"); + case ICmpInst::ICMP_ULT: + case ICmpInst::ICMP_SLT: // X < null -> always false + LV = ConstantInt::getFalse(GV->getContext()); + break; + case ICmpInst::ICMP_ULE: + case ICmpInst::ICMP_SLE: + case ICmpInst::ICMP_EQ: + LV = BinaryOperator::CreateNot(LV, "notinit", ICI); + break; + case ICmpInst::ICMP_NE: + case ICmpInst::ICMP_UGE: + case ICmpInst::ICMP_SGE: + case ICmpInst::ICMP_UGT: + case ICmpInst::ICMP_SGT: + break; // no change. + } + ICI->replaceAllUsesWith(LV); + ICI->eraseFromParent(); + } + } + LI->eraseFromParent(); + } else { + StoreInst *SI = cast<StoreInst>(GV->use_back()); + // The global is initialized when the store to it occurs. + new StoreInst(ConstantInt::getTrue(GV->getContext()), 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 (both CI and BCI). + GV->eraseFromParent(); + if (BCI) BCI->eraseFromParent(); + CI->eraseFromParent(); + + // To further other optimizations, loop over all users of NewGV and try to + // constant prop them. This will promote GEP instructions with constant + // indices into GEP constant-exprs, which will allow global-opt to hack on it. + ConstantPropUsersOf(NewGV); + 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 = cast<Instruction>(*UI); + + 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. + InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator(); + } else if (isa<BitCastInst>(U)) { + // Must be bitcast between the malloc and store to initialize the global. + ReplaceUsesOfMallocWithGlobal(U, GV); + U->eraseFromParent(); + continue; + } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) { + // If this is a "GEP bitcast" and the user is a store to the global, then + // just process it as a bitcast. + if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse()) + if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back())) + if (SI->getOperand(1) == GV) { + // Must be bitcast GEP between the malloc and store to initialize + // the global. + ReplaceUsesOfMallocWithGlobal(GEPI, GV); + GEPI->eraseFromParent(); + continue; + } + } + + // Insert a load from the global, and use it instead of the malloc. + Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt); + U->replaceUsesOfWith(Alloc, NL); + } +} + +/// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi +/// of a load) are simple enough to perform heap SRA on. This permits GEP's +/// that index through the array and struct field, icmps of null, and PHIs. +static bool LoadUsesSimpleEnoughForHeapSRA(Value *V, + SmallPtrSet<PHINode*, 32> &LoadUsingPHIs, + SmallPtrSet<PHINode*, 32> &LoadUsingPHIsPerLoad) { + // We permit two users of the load: setcc comparing against the null + // pointer, and a getelementptr of a specific form. + for (Value::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 (!LoadUsingPHIsPerLoad.insert(PN)) + // This means some phi nodes are dependent on each other. + // Avoid infinite looping! + return false; + if (!LoadUsingPHIs.insert(PN)) + // If we have already analyzed this PHI, then it is safe. + continue; + + // Make sure all uses of the PHI are simple enough to transform. + if (!LoadUsesSimpleEnoughForHeapSRA(PN, + LoadUsingPHIs, LoadUsingPHIsPerLoad)) + return false; + + continue; + } + + // Otherwise we don't know what this is, not ok. + return false; + } + + return true; +} + + +/// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from +/// GV are simple enough to perform HeapSRA, return true. +static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(GlobalVariable *GV, + Instruction *StoredVal) { + SmallPtrSet<PHINode*, 32> LoadUsingPHIs; + SmallPtrSet<PHINode*, 32> LoadUsingPHIsPerLoad; + 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, + LoadUsingPHIsPerLoad)) + return false; + LoadUsingPHIsPerLoad.clear(); + } + + // If we reach here, we know that all uses of the loads and transitive uses + // (through PHI nodes) are simple enough to transform. However, we don't know + // that all inputs the to the PHI nodes are in the same equivalence sets. + // Check to verify that all operands of the PHIs are either PHIS that can be + // transformed, loads from GV, or MI itself. + for (SmallPtrSet<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 == StoredVal) 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"+Twine(FieldNo), LI); + } else if (PHINode *PN = dyn_cast<PHINode>(V)) { + // PN's type is pointer to struct. Make a new PHI of pointer to struct + // field. + const StructType *ST = + cast<StructType>(cast<PointerType>(PN->getType())->getElementType()); + + Result = + PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)), + PN->getName()+".f"+Twine(FieldNo), PN); + PHIsToRewrite.push_back(std::make_pair(PN, FieldNo)); + } else { + llvm_unreachable("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, SCI->getPredicate(), NPtr, + Constant::getNullValue(NPtr->getType()), + SCI->getName()); + SCI->replaceAllUsesWith(New); + SCI->eraseFromParent(); + return; + } + + // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...' + if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) { + assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2)) + && "Unexpected GEPI!"); + + // Load the pointer for this field. + unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); + Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo, + InsertedScalarizedValues, PHIsToRewrite); + + // Create the new GEP idx vector. + SmallVector<Value*, 8> GEPIdx; + GEPIdx.push_back(GEPI->getOperand(1)); + GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end()); + + Value *NGEPI = GetElementPtrInst::Create(NewPtr, + GEPIdx.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 - CI is an allocation of an array of structures. Break +/// it up into multiple allocations of arrays of the fields. +static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI, + Value* NElems, TargetData *TD) { + DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI << '\n'); + const Type* MAT = getMallocAllocatedType(CI); + const StructType *STy = cast<StructType>(MAT); + + // There is guaranteed to be at least one use of the malloc (storing + // it into GV). If there are other uses, change them to be uses of + // the global to simplify later code. This also deletes the store + // into GV. + ReplaceUsesOfMallocWithGlobal(CI, GV); + + // Okay, at this point, there are no users of the malloc. Insert N + // new mallocs at the same place as CI, and N globals. + std::vector<Value*> FieldGlobals; + std::vector<Value*> FieldMallocs; + + for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ + const Type *FieldTy = STy->getElementType(FieldNo); + const PointerType *PFieldTy = PointerType::getUnqual(FieldTy); + + GlobalVariable *NGV = + new GlobalVariable(*GV->getParent(), + PFieldTy, false, GlobalValue::InternalLinkage, + Constant::getNullValue(PFieldTy), + GV->getName() + ".f" + Twine(FieldNo), GV, + GV->isThreadLocal()); + FieldGlobals.push_back(NGV); + + unsigned TypeSize = TD->getTypeAllocSize(FieldTy); + if (const StructType *ST = dyn_cast<StructType>(FieldTy)) + TypeSize = TD->getStructLayout(ST)->getSizeInBytes(); + const Type *IntPtrTy = TD->getIntPtrType(CI->getContext()); + Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy, + ConstantInt::get(IntPtrTy, TypeSize), + NElems, + CI->getName() + ".f" + Twine(FieldNo)); + CallInst *NCI = dyn_cast<BitCastInst>(NMI) ? + extractMallocCallFromBitCast(NMI) : cast<CallInst>(NMI); + FieldMallocs.push_back(NCI); + new StoreInst(NMI, NGV, CI); + } + + // The tricky aspect of this transformation is handling the case when malloc + // fails. In the original code, malloc failing would set the result pointer + // of malloc to null. In this case, some mallocs could succeed and others + // could fail. As such, we emit code that looks like this: + // F0 = malloc(field0) + // F1 = malloc(field1) + // F2 = malloc(field2) + // if (F0 == 0 || F1 == 0 || F2 == 0) { + // if (F0) { free(F0); F0 = 0; } + // if (F1) { free(F1); F1 = 0; } + // if (F2) { free(F2); F2 = 0; } + // } + // The malloc can also fail if its argument is too large. + Constant *ConstantZero = ConstantInt::get(CI->getOperand(1)->getType(), 0); + Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getOperand(1), + ConstantZero, "isneg"); + for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { + Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i], + Constant::getNullValue(FieldMallocs[i]->getType()), + "isnull"); + RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI); + } + + // Split the basic block at the old malloc. + BasicBlock *OrigBB = CI->getParent(); + BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont"); + + // Create the block to check the first condition. Put all these blocks at the + // end of the function as they are unlikely to be executed. + BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(), + "malloc_ret_null", + OrigBB->getParent()); + + // Remove the uncond branch from OrigBB to ContBB, turning it into a cond + // branch on RunningOr. + OrigBB->getTerminator()->eraseFromParent(); + BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB); + + // Within the NullPtrBlock, we need to emit a comparison and branch for each + // pointer, because some may be null while others are not. + for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { + Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock); + Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal, + Constant::getNullValue(GVVal->getType()), + "tmp"); + BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it", + OrigBB->getParent()); + BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next", + OrigBB->getParent()); + Instruction *BI = BranchInst::Create(FreeBlock, NextBlock, + Cmp, NullPtrBlock); + + // Fill in FreeBlock. + CallInst::CreateFree(GVVal, BI); + new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], + FreeBlock); + BranchInst::Create(NextBlock, FreeBlock); + + NullPtrBlock = NextBlock; + } + + BranchInst::Create(ContBB, NullPtrBlock); + + // CI is no longer needed, remove it. + CI->eraseFromParent(); + + /// InsertedScalarizedLoads - As we process loads, if we can't immediately + /// update all uses of the load, keep track of what scalarized loads are + /// inserted for a given load. + DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues; + InsertedScalarizedValues[GV] = FieldGlobals; + + std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite; + + // Okay, the malloc site is completely handled. All of the uses of GV are now + // loads, and all uses of those loads are simple. Rewrite them to use loads + // of the per-field globals instead. + for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) { + Instruction *User = cast<Instruction>(*UI++); + + if (LoadInst *LI = dyn_cast<LoadInst>(User)) { + RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite); + continue; + } + + // Must be a store of null. + StoreInst *SI = cast<StoreInst>(User); + assert(isa<ConstantPointerNull>(SI->getOperand(0)) && + "Unexpected heap-sra user!"); + + // Insert a store of null into each global. + for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { + 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, + CallInst *CI, + const Type *AllocTy, + Module::global_iterator &GVI, + TargetData *TD) { + // If this is a malloc of an abstract type, don't touch it. + if (!AllocTy->isSized()) + return false; + + // We can't optimize this global unless all uses of it are *known* to be + // of the malloc value, not of the null initializer value (consider a use + // that compares the global's value against zero to see if the malloc has + // been reached). To do this, we check to see if all uses of the global + // would trap if the global were null: this proves that they must all + // happen after the malloc. + if (!AllUsesOfLoadedValueWillTrapIfNull(GV)) + return false; + + // We can't optimize this if the malloc itself is used in a complex way, + // for example, being stored into multiple globals. This allows the + // malloc to be stored into the specified global, loaded setcc'd, and + // GEP'd. These are all things we could transform to using the global + // for. + { + SmallPtrSet<PHINode*, 8> PHIs; + if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs)) + return false; + } + + // If we have a global that is only initialized with a fixed size malloc, + // transform the program to use global memory instead of malloc'd memory. + // This eliminates dynamic allocation, avoids an indirection accessing the + // data, and exposes the resultant global to further GlobalOpt. + // We cannot optimize the malloc if we cannot determine malloc array size. + if (Value *NElems = getMallocArraySize(CI, TD, true)) { + if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems)) + // Restrict this transformation to only working on small allocations + // (2048 bytes currently), as we don't want to introduce a 16M global or + // something. + if (TD && + NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) { + GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElems, TD); + return true; + } + + // If the allocation is an array of structures, consider transforming this + // into multiple malloc'd arrays, one for each field. This is basically + // SRoA for malloc'd memory. + + // If this is an allocation of a fixed size array of structs, analyze as a + // variable size array. malloc [100 x struct],1 -> malloc struct, 100 + if (NElems == ConstantInt::get(CI->getOperand(1)->getType(), 1)) + 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, CI)) { + + // If this is a fixed size array, transform the Malloc to be an alloc of + // structs. malloc [100 x struct],1 -> malloc struct, 100 + if (const ArrayType *AT = + dyn_cast<ArrayType>(getMallocAllocatedType(CI))) { + const Type *IntPtrTy = TD->getIntPtrType(CI->getContext()); + unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes(); + Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize); + Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements()); + Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy, + AllocSize, NumElements, + CI->getName()); + Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI); + CI->replaceAllUsesWith(Cast); + CI->eraseFromParent(); + CI = dyn_cast<BitCastInst>(Malloc) ? + extractMallocCallFromBitCast(Malloc) : cast<CallInst>(Malloc); + } + + GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, true),TD); + 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 (CallInst *CI = extractMallocCall(StoredOnceVal)) { + const Type* MallocType = getMallocAllocatedType(CI); + if (MallocType && TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, + 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, pointer or vector, don't do this optimization because a select + // between them is very expensive and unlikely to lead to later + // simplification. In these cases, we typically end up with "cond ? v1 : v2" + // where v1 and v2 both require constant pool loads, a big loss. + if (GVElType == Type::getInt1Ty(GV->getContext()) || + GVElType->isFloatingPoint() || + isa<PointerType>(GVElType) || 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; + + DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV); + + // Create the new global, initializing it to false. + GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()), + false, + GlobalValue::InternalLinkage, + ConstantInt::getFalse(GV->getContext()), + GV->getName()+".b", + GV->isThreadLocal()); + GV->getParent()->getGlobalList().insert(GV, NewGV); + + Constant *InitVal = GV->getInitializer(); + assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) && + "No reason to shrink to bool!"); + + // If initialized to zero and storing one into the global, we can use a cast + // instead of a select to synthesize the desired value. + bool IsOneZero = false; + if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)) + IsOneZero = InitVal->isNullValue() && CI->isOne(); + + while (!GV->use_empty()) { + Instruction *UI = cast<Instruction>(GV->use_back()); + if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { + // Change the store into a boolean store. + bool StoringOther = SI->getOperand(0) == OtherVal; + // Only do this if we weren't storing a loaded value. + Value *StoreVal; + if (StoringOther || SI->getOperand(0) == InitVal) + StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()), + StoringOther); + else { + // Otherwise, we are storing a previously loaded copy. To do this, + // change the copy from copying the original value to just copying the + // bool. + Instruction *StoredVal = cast<Instruction>(SI->getOperand(0)); + + // If we'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()) { + DEBUG(dbgs() << "GLOBAL DEAD: " << *GV); + GV->eraseFromParent(); + ++NumDeleted; + return true; + } + + if (!AnalyzeGlobal(GV, GS, PHIUsers)) { +#if 0 + DEBUG(dbgs() << "Global: " << *GV); + DEBUG(dbgs() << " isLoaded = " << GS.isLoaded << "\n"); + DEBUG(dbgs() << " StoredType = "); + switch (GS.StoredType) { + case GlobalStatus::NotStored: DEBUG(dbgs() << "NEVER STORED\n"); break; + case GlobalStatus::isInitializerStored: DEBUG(dbgs() << "INIT STORED\n"); + break; + case GlobalStatus::isStoredOnce: DEBUG(dbgs() << "STORED ONCE\n"); break; + case GlobalStatus::isStored: DEBUG(dbgs() << "stored\n"); break; + } + if (GS.StoredType == GlobalStatus::isStoredOnce && GS.StoredOnceValue) + DEBUG(dbgs() << " StoredOnceValue = " << *GS.StoredOnceValue << "\n"); + if (GS.AccessingFunction && !GS.HasMultipleAccessingFunctions) + DEBUG(dbgs() << " AccessingFunction = " << GS.AccessingFunction->getName() + << "\n"); + DEBUG(dbgs() << " HasMultipleAccessingFunctions = " + << GS.HasMultipleAccessingFunctions << "\n"); + DEBUG(dbgs() << " HasNonInstructionUser = " + << GS.HasNonInstructionUser<<"\n"); + DEBUG(dbgs() << "\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 the global is in different address space, don't bring it to stack. + if (!GS.HasMultipleAccessingFunctions && + GS.AccessingFunction && !GS.HasNonInstructionUser && + GV->getType()->getElementType()->isSingleValueType() && + GS.AccessingFunction->getName() == "main" && + GS.AccessingFunction->hasExternalLinkage() && + GV->getType()->getAddressSpace() == 0) { + DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV); + Instruction* FirstI = 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) { + DEBUG(dbgs() << "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) { + DEBUG(dbgs() << "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()) { + DEBUG(dbgs() << " *** Marking constant allowed us to simplify " + << "all users and delete global!\n"); + GV->eraseFromParent(); + ++NumDeleted; + } + + ++NumMarked; + return true; + } else if (!GV->getInitializer()->getType()->isSingleValueType()) { + if (TargetData *TD = getAnalysisIfAvailable<TargetData>()) + if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) { + GVI = FirstNewGV; // Don't skip the newly produced globals! + return true; + } + } else if (GS.StoredType == GlobalStatus::isStoredOnce) { + // If the initial value for the global was an undef value, and if only + // one other value was stored into it, we can just change the + // initializer to be the stored value, then delete all stores to the + // global. This allows us to mark it constant. + if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) + if (isa<UndefValue>(GV->getInitializer())) { + // Change the initial value here. + GV->setInitializer(SOVConstant); + + // Clean up any obviously simplifiable users now. + CleanupConstantGlobalUsers(GV, GV->getInitializer()); + + if (GV->use_empty()) { + DEBUG(dbgs() << " *** Substituting initializer allowed us to " + << "simplify all users and delete global!\n"); + GV->eraseFromParent(); + ++NumDeleted; + } else { + GVI = GV; + } + ++NumSubstitute; + return true; + } + + // Try to optimize globals based on the knowledge that only one value + // (besides its initializer) is ever stored to the global. + if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GVI, + getAnalysisIfAvailable<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; +} + +/// 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++; + // Functions without names cannot be referenced outside this module. + if (!F->hasName() && !F->isDeclaration()) + F->setLinkage(GlobalValue::InternalLinkage); + F->removeDeadConstantUsers(); + if (F->use_empty() && (F->hasLocalLinkage() || F->hasLinkOnceLinkage())) { + F->eraseFromParent(); + Changed = true; + ++NumFnDeleted; + } else if (F->hasLocalLinkage()) { + if (F->getCallingConv() == CallingConv::C && !F->isVarArg() && + !F->hasAddressTaken()) { + // If this function has C calling conventions, is not a varargs + // function, and is only called directly, promote it to use the Fast + // calling convention. + F->setCallingConv(CallingConv::Fast); + ChangeCalleesToFastCall(F); + ++NumFastCallFns; + Changed = true; + } + + if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) && + !F->hasAddressTaken()) { + // The function is not used by a trampoline intrinsic, so it is safe + // to remove the 'nest' attribute. + RemoveNestAttribute(F); + ++NumNestRemoved; + Changed = true; + } + } + } + return Changed; +} + +bool GlobalOpt::OptimizeGlobalVars(Module &M) { + bool Changed = false; + for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); + GVI != E; ) { + GlobalVariable *GV = GVI++; + // Global variables without names cannot be referenced outside this module. + if (!GV->hasName() && !GV->isDeclaration()) + GV->setLinkage(GlobalValue::InternalLinkage); + // Simplify the initializer. + if (GV->hasInitializer()) + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) { + TargetData *TD = getAnalysisIfAvailable<TargetData>(); + Constant *New = ConstantFoldConstantExpression(CE, TD); + if (New && New != CE) + GV->setInitializer(New); + } + // Do more involved optimizations if the global is internal. + if (!GV->isConstant() && GV->hasLocalLinkage() && + 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)->isInteger(32)) 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()->isVoidTy() || + FTy->isVarArg() || FTy->getNumParams() != 0) + return 0; + + // Verify that the initializer is simple enough for us to handle. + if (!I->hasDefinitiveInitializer()) 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::getInt32Ty(GCL->getContext()),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::getVoidTy(GCL->getContext()), + false); + const PointerType *PFTy = PointerType::getUnqual(FTy); + CSVals[1] = Constant::getNullValue(PFTy); + CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), + 2147483647); + } + CAList.push_back(ConstantStruct::get(GCL->getContext(), CSVals, false)); + } + + // 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, "", + 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) { + // Conservatively, avoid aggregate types. This is because we don't + // want to worry about them partially overlapping other stores. + if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType()) + return false; + + if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C)) + // Do not allow weak/linkonce/dllimport/dllexport linkage or + // external globals. + return GV->hasDefinitiveInitializer(); + + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) + // Handle a constantexpr gep. + if (CE->getOpcode() == Instruction::GetElementPtr && + isa<GlobalVariable>(CE->getOperand(0)) && + cast<GEPOperator>(CE)->isInBounds()) { + GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); + // Do not allow weak/linkonce/dllimport/dllexport linkage or + // external globals. + if (!GV->hasDefinitiveInitializer()) + return false; + + // The first index must be zero. + ConstantInt *CI = dyn_cast<ConstantInt>(*next(CE->op_begin())); + if (!CI || !CI->isZero()) return false; + + // The remaining indices must be compile-time known integers within the + // notional bounds of the corresponding static array types. + if (!CE->isGEPWithNoNotionalOverIndexing()) + return false; + + return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); + } + 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; + } + + std::vector<Constant*> Elts; + if (const StructType *STy = dyn_cast<StructType>(Init->getType())) { + + // 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 { + llvm_unreachable("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(Init->getContext(), &Elts[0], Elts.size(), + STy->isPacked()); + } else { + ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); + const SequentialType *InitTy = cast<SequentialType>(Init->getType()); + + uint64_t NumElts; + if (const ArrayType *ATy = dyn_cast<ArrayType>(InitTy)) + NumElts = ATy->getNumElements(); + else + NumElts = cast<VectorType>(InitTy)->getNumElements(); + + + // Break up the array into elements. + 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 (ConstantVector *CV = dyn_cast<ConstantVector>(Init)) { + for (User::op_iterator i = CV->op_begin(), e = CV->op_end(); i != e; ++i) + Elts.push_back(cast<Constant>(*i)); + } else if (isa<ConstantAggregateZero>(Init)) { + Elts.assign(NumElts, Constant::getNullValue(InitTy->getElementType())); + } else { + assert(isa<UndefValue>(Init) && "This code is out of sync with " + " ConstantFoldLoadThroughGEPConstantExpr"); + Elts.assign(NumElts, UndefValue::get(InitTy->getElementType())); + } + + assert(CI->getZExtValue() < NumElts); + Elts[CI->getZExtValue()] = + EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); + + if (isa<ArrayType>(Init->getType())) + return ConstantArray::get(cast<ArrayType>(InitTy), Elts); + else + return ConstantVector::get(&Elts[0], Elts.size()); + } +} + +/// CommitValueTo - We have decided that Addr (which satisfies the predicate +/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen. +static void CommitValueTo(Constant *Val, Constant *Addr) { + if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) { + assert(GV->hasInitializer()); + GV->setInitializer(Val); + return; + } + + ConstantExpr *CE = cast<ConstantExpr>(Addr); + GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); + GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2)); +} + +/// 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->hasDefinitiveInitializer()) + return GV->getInitializer(); + return 0; + } + + // Handle a constantexpr getelementptr. + if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P)) + if (CE->getOpcode() == Instruction::GetElementPtr && + isa<GlobalVariable>(CE->getOperand(0))) { + GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); + if (GV->hasDefinitiveInitializer()) + return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE); + } + + return 0; // don't know how to evaluate. +} + +/// 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 SmallVectorImpl<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 = cast<GEPOperator>(GEP)->isInBounds() ? + ConstantExpr::getInBoundsGetElementPtr(P, &GEPOps[0], GEPOps.size()) : + 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)) { + + // Debug info can safely be ignored here. + if (isa<DbgInfoIntrinsic>(CI)) { + ++CurInst; + continue; + } + + // 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. + + SmallVector<Constant*, 8> 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.data(), + 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 (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) { + Value *Val = getVal(Values, IBI->getAddress())->stripPointerCasts(); + if (BlockAddress *BA = dyn_cast<BlockAddress>(Val)) + NewBB = BA->getBasicBlock(); + else + return false; // Cannot determine. + } 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, + SmallVector<Constant*, 0>(), CallStack, + MutatedMemory, AllocaTmps); + if (EvalSuccess) { + // We succeeded at evaluation: commit the result. + DEBUG(dbgs() << "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::OptimizeGlobalAliases(Module &M) { + bool Changed = false; + + for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); + I != E;) { + Module::alias_iterator J = I++; + // Aliases without names cannot be referenced outside this module. + if (!J->hasName() && !J->isDeclaration()) + J->setLinkage(GlobalValue::InternalLinkage); + // If the aliasee may change at link time, nothing can be done - bail out. + if (J->mayBeOverridden()) + continue; + + Constant *Aliasee = J->getAliasee(); + GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts()); + Target->removeDeadConstantUsers(); + bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse(); + + // Make all users of the alias use the aliasee instead. + if (!J->use_empty()) { + J->replaceAllUsesWith(Aliasee); + ++NumAliasesResolved; + Changed = true; + } + + // If the alias is externally visible, we may still be able to simplify it. + if (!J->hasLocalLinkage()) { + // If the aliasee has internal linkage, give it the name and linkage + // of the alias, and delete the alias. This turns: + // define internal ... @f(...) + // @a = alias ... @f + // into: + // define ... @a(...) + if (!Target->hasLocalLinkage()) + continue; + + // Do not perform the transform if multiple aliases potentially target the + // aliasee. This check also ensures that it is safe to replace the section + // and other attributes of the aliasee with those of the alias. + if (!hasOneUse) + continue; + + // Give the aliasee the name, linkage and other attributes of the alias. + Target->takeName(J); + Target->setLinkage(J->getLinkage()); + Target->GlobalValue::copyAttributesFrom(J); + } + + // Delete the alias. + M.getAliasList().erase(J); + ++NumAliasesRemoved; + Changed = true; + } + + return Changed; +} + +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 |= OptimizeGlobalAliases(M); + Changed |= LocalChange; + } + + // TODO: Move all global ctors functions to the end of the module for code + // layout. + + return Changed; +} |