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Diffstat (limited to 'gnu/llvm/lib/Transforms/IPO/GlobalOpt.cpp')
| -rw-r--r-- | gnu/llvm/lib/Transforms/IPO/GlobalOpt.cpp | 3030 |
1 files changed, 0 insertions, 3030 deletions
diff --git a/gnu/llvm/lib/Transforms/IPO/GlobalOpt.cpp b/gnu/llvm/lib/Transforms/IPO/GlobalOpt.cpp deleted file mode 100644 index 3005aafd06b..00000000000 --- a/gnu/llvm/lib/Transforms/IPO/GlobalOpt.cpp +++ /dev/null @@ -1,3030 +0,0 @@ -//===- 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. -// -//===----------------------------------------------------------------------===// - -#include "llvm/Transforms/IPO/GlobalOpt.h" -#include "llvm/ADT/DenseMap.h" -#include "llvm/ADT/STLExtras.h" -#include "llvm/ADT/SmallPtrSet.h" -#include "llvm/ADT/SmallVector.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/ADT/Twine.h" -#include "llvm/ADT/iterator_range.h" -#include "llvm/Analysis/BlockFrequencyInfo.h" -#include "llvm/Analysis/ConstantFolding.h" -#include "llvm/Analysis/MemoryBuiltins.h" -#include "llvm/Analysis/TargetLibraryInfo.h" -#include "llvm/Analysis/TargetTransformInfo.h" -#include "llvm/Transforms/Utils/Local.h" -#include "llvm/BinaryFormat/Dwarf.h" -#include "llvm/IR/Attributes.h" -#include "llvm/IR/BasicBlock.h" -#include "llvm/IR/CallSite.h" -#include "llvm/IR/CallingConv.h" -#include "llvm/IR/Constant.h" -#include "llvm/IR/Constants.h" -#include "llvm/IR/DataLayout.h" -#include "llvm/IR/DebugInfoMetadata.h" -#include "llvm/IR/DerivedTypes.h" -#include "llvm/IR/Dominators.h" -#include "llvm/IR/Function.h" -#include "llvm/IR/GetElementPtrTypeIterator.h" -#include "llvm/IR/GlobalAlias.h" -#include "llvm/IR/GlobalValue.h" -#include "llvm/IR/GlobalVariable.h" -#include "llvm/IR/InstrTypes.h" -#include "llvm/IR/Instruction.h" -#include "llvm/IR/Instructions.h" -#include "llvm/IR/IntrinsicInst.h" -#include "llvm/IR/Module.h" -#include "llvm/IR/Operator.h" -#include "llvm/IR/Type.h" -#include "llvm/IR/Use.h" -#include "llvm/IR/User.h" -#include "llvm/IR/Value.h" -#include "llvm/IR/ValueHandle.h" -#include "llvm/Pass.h" -#include "llvm/Support/AtomicOrdering.h" -#include "llvm/Support/Casting.h" -#include "llvm/Support/CommandLine.h" -#include "llvm/Support/Debug.h" -#include "llvm/Support/ErrorHandling.h" -#include "llvm/Support/MathExtras.h" -#include "llvm/Support/raw_ostream.h" -#include "llvm/Transforms/IPO.h" -#include "llvm/Transforms/Utils/CtorUtils.h" -#include "llvm/Transforms/Utils/Evaluator.h" -#include "llvm/Transforms/Utils/GlobalStatus.h" -#include <cassert> -#include <cstdint> -#include <utility> -#include <vector> - -using namespace llvm; - -#define DEBUG_TYPE "globalopt" - -STATISTIC(NumMarked , "Number of globals marked constant"); -STATISTIC(NumUnnamed , "Number of globals marked unnamed_addr"); -STATISTIC(NumSRA , "Number of aggregate globals broken into scalars"); -STATISTIC(NumHeapSRA , "Number of heap objects SRA'd"); -STATISTIC(NumSubstitute,"Number of globals with initializers stored into them"); -STATISTIC(NumDeleted , "Number of globals deleted"); -STATISTIC(NumGlobUses , "Number of global uses devirtualized"); -STATISTIC(NumLocalized , "Number of globals localized"); -STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans"); -STATISTIC(NumFastCallFns , "Number of functions converted to fastcc"); -STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated"); -STATISTIC(NumNestRemoved , "Number of nest attributes removed"); -STATISTIC(NumAliasesResolved, "Number of global aliases resolved"); -STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated"); -STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed"); -STATISTIC(NumInternalFunc, "Number of internal functions"); -STATISTIC(NumColdCC, "Number of functions marked coldcc"); - -static cl::opt<bool> - EnableColdCCStressTest("enable-coldcc-stress-test", - cl::desc("Enable stress test of coldcc by adding " - "calling conv to all internal functions."), - cl::init(false), cl::Hidden); - -static cl::opt<int> ColdCCRelFreq( - "coldcc-rel-freq", cl::Hidden, cl::init(2), cl::ZeroOrMore, - cl::desc( - "Maximum block frequency, expressed as a percentage of caller's " - "entry frequency, for a call site to be considered cold for enabling" - "coldcc")); - -/// Is this global variable possibly used by a leak checker as a root? If so, -/// we might not really want to eliminate the stores to it. -static bool isLeakCheckerRoot(GlobalVariable *GV) { - // A global variable is a root if it is a pointer, or could plausibly contain - // a pointer. There are two challenges; one is that we could have a struct - // the has an inner member which is a pointer. We recurse through the type to - // detect these (up to a point). The other is that we may actually be a union - // of a pointer and another type, and so our LLVM type is an integer which - // gets converted into a pointer, or our type is an [i8 x #] with a pointer - // potentially contained here. - - if (GV->hasPrivateLinkage()) - return false; - - SmallVector<Type *, 4> Types; - Types.push_back(GV->getValueType()); - - unsigned Limit = 20; - do { - Type *Ty = Types.pop_back_val(); - switch (Ty->getTypeID()) { - default: break; - case Type::PointerTyID: return true; - case Type::ArrayTyID: - case Type::VectorTyID: { - SequentialType *STy = cast<SequentialType>(Ty); - Types.push_back(STy->getElementType()); - break; - } - case Type::StructTyID: { - StructType *STy = cast<StructType>(Ty); - if (STy->isOpaque()) return true; - for (StructType::element_iterator I = STy->element_begin(), - E = STy->element_end(); I != E; ++I) { - Type *InnerTy = *I; - if (isa<PointerType>(InnerTy)) return true; - if (isa<CompositeType>(InnerTy)) - Types.push_back(InnerTy); - } - break; - } - } - if (--Limit == 0) return true; - } while (!Types.empty()); - return false; -} - -/// Given a value that is stored to a global but never read, determine whether -/// it's safe to remove the store and the chain of computation that feeds the -/// store. -static bool IsSafeComputationToRemove(Value *V, const TargetLibraryInfo *TLI) { - do { - if (isa<Constant>(V)) - return true; - if (!V->hasOneUse()) - return false; - if (isa<LoadInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V) || - isa<GlobalValue>(V)) - return false; - if (isAllocationFn(V, TLI)) - return true; - - Instruction *I = cast<Instruction>(V); - if (I->mayHaveSideEffects()) - return false; - if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) { - if (!GEP->hasAllConstantIndices()) - return false; - } else if (I->getNumOperands() != 1) { - return false; - } - - V = I->getOperand(0); - } while (true); -} - -/// This GV is a pointer root. Loop over all users of the global and clean up -/// any that obviously don't assign the global a value that isn't dynamically -/// allocated. -static bool CleanupPointerRootUsers(GlobalVariable *GV, - const TargetLibraryInfo *TLI) { - // A brief explanation of leak checkers. The goal is to find bugs where - // pointers are forgotten, causing an accumulating growth in memory - // usage over time. The common strategy for leak checkers is to whitelist the - // memory pointed to by globals at exit. This is popular because it also - // solves another problem where the main thread of a C++ program may shut down - // before other threads that are still expecting to use those globals. To - // handle that case, we expect the program may create a singleton and never - // destroy it. - - bool Changed = false; - - // If Dead[n].first is the only use of a malloc result, we can delete its - // chain of computation and the store to the global in Dead[n].second. - SmallVector<std::pair<Instruction *, Instruction *>, 32> Dead; - - // Constants can't be pointers to dynamically allocated memory. - for (Value::user_iterator UI = GV->user_begin(), E = GV->user_end(); - UI != E;) { - User *U = *UI++; - if (StoreInst *SI = dyn_cast<StoreInst>(U)) { - Value *V = SI->getValueOperand(); - if (isa<Constant>(V)) { - Changed = true; - SI->eraseFromParent(); - } else if (Instruction *I = dyn_cast<Instruction>(V)) { - if (I->hasOneUse()) - Dead.push_back(std::make_pair(I, SI)); - } - } else if (MemSetInst *MSI = dyn_cast<MemSetInst>(U)) { - if (isa<Constant>(MSI->getValue())) { - Changed = true; - MSI->eraseFromParent(); - } else if (Instruction *I = dyn_cast<Instruction>(MSI->getValue())) { - if (I->hasOneUse()) - Dead.push_back(std::make_pair(I, MSI)); - } - } else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U)) { - GlobalVariable *MemSrc = dyn_cast<GlobalVariable>(MTI->getSource()); - if (MemSrc && MemSrc->isConstant()) { - Changed = true; - MTI->eraseFromParent(); - } else if (Instruction *I = dyn_cast<Instruction>(MemSrc)) { - if (I->hasOneUse()) - Dead.push_back(std::make_pair(I, MTI)); - } - } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { - if (CE->use_empty()) { - CE->destroyConstant(); - Changed = true; - } - } else if (Constant *C = dyn_cast<Constant>(U)) { - if (isSafeToDestroyConstant(C)) { - C->destroyConstant(); - // This could have invalidated UI, start over from scratch. - Dead.clear(); - CleanupPointerRootUsers(GV, TLI); - return true; - } - } - } - - for (int i = 0, e = Dead.size(); i != e; ++i) { - if (IsSafeComputationToRemove(Dead[i].first, TLI)) { - Dead[i].second->eraseFromParent(); - Instruction *I = Dead[i].first; - do { - if (isAllocationFn(I, TLI)) - break; - Instruction *J = dyn_cast<Instruction>(I->getOperand(0)); - if (!J) - break; - I->eraseFromParent(); - I = J; - } while (true); - I->eraseFromParent(); - } - } - - return Changed; -} - -/// We just marked GV constant. Loop over all users of the global, cleaning up -/// the obvious ones. This is largely just a quick scan over the use list to -/// clean up the easy and obvious cruft. This returns true if it made a change. -static bool CleanupConstantGlobalUsers(Value *V, Constant *Init, - const DataLayout &DL, - TargetLibraryInfo *TLI) { - bool Changed = false; - // Note that we need to use a weak value handle for the worklist items. When - // we delete a constant array, we may also be holding pointer to one of its - // elements (or an element of one of its elements if we're dealing with an - // array of arrays) in the worklist. - SmallVector<WeakTrackingVH, 8> WorkList(V->user_begin(), V->user_end()); - while (!WorkList.empty()) { - Value *UV = WorkList.pop_back_val(); - if (!UV) - continue; - - User *U = cast<User>(UV); - - if (LoadInst *LI = dyn_cast<LoadInst>(U)) { - if (Init) { - // Replace the load with the initializer. - LI->replaceAllUsesWith(Init); - LI->eraseFromParent(); - Changed = true; - } - } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) { - // Store must be unreachable or storing Init into the global. - SI->eraseFromParent(); - Changed = true; - } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) { - if (CE->getOpcode() == Instruction::GetElementPtr) { - Constant *SubInit = nullptr; - if (Init) - SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); - Changed |= CleanupConstantGlobalUsers(CE, SubInit, DL, TLI); - } else if ((CE->getOpcode() == Instruction::BitCast && - CE->getType()->isPointerTy()) || - CE->getOpcode() == Instruction::AddrSpaceCast) { - // Pointer cast, delete any stores and memsets to the global. - Changed |= CleanupConstantGlobalUsers(CE, nullptr, DL, TLI); - } - - if (CE->use_empty()) { - CE->destroyConstant(); - Changed = true; - } - } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { - // Do not transform "gepinst (gep constexpr (GV))" here, because forming - // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold - // and will invalidate our notion of what Init is. - Constant *SubInit = nullptr; - if (!isa<ConstantExpr>(GEP->getOperand(0))) { - ConstantExpr *CE = dyn_cast_or_null<ConstantExpr>( - ConstantFoldInstruction(GEP, DL, TLI)); - if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr) - SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE); - - // If the initializer is an all-null value and we have an inbounds GEP, - // we already know what the result of any load from that GEP is. - // TODO: Handle splats. - if (Init && isa<ConstantAggregateZero>(Init) && GEP->isInBounds()) - SubInit = Constant::getNullValue(GEP->getResultElementType()); - } - Changed |= CleanupConstantGlobalUsers(GEP, SubInit, DL, TLI); - - if (GEP->use_empty()) { - GEP->eraseFromParent(); - Changed = true; - } - } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv - if (MI->getRawDest() == V) { - MI->eraseFromParent(); - Changed = true; - } - - } else if (Constant *C = dyn_cast<Constant>(U)) { - // If we have a chain of dead constantexprs or other things dangling from - // us, and if they are all dead, nuke them without remorse. - if (isSafeToDestroyConstant(C)) { - C->destroyConstant(); - CleanupConstantGlobalUsers(V, Init, DL, TLI); - return true; - } - } - } - return Changed; -} - -static bool isSafeSROAElementUse(Value *V); - -/// Return true if the specified GEP is a safe user of a derived -/// expression from a global that we want to SROA. -static bool isSafeSROAGEP(User *U) { - // Check to see if this ConstantExpr GEP is SRA'able. In particular, we - // don't like < 3 operand CE's, and we don't like non-constant integer - // indices. This enforces that all uses are 'gep GV, 0, C, ...' for some - // value of C. - if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) || - !cast<Constant>(U->getOperand(1))->isNullValue()) - return false; - - gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U); - ++GEPI; // Skip over the pointer index. - - // For all other level we require that the indices are constant and inrange. - // In particular, consider: A[0][i]. We cannot know that the user isn't doing - // invalid things like allowing i to index an out-of-range subscript that - // accesses A[1]. This can also happen between different members of a struct - // in llvm IR. - for (; GEPI != E; ++GEPI) { - if (GEPI.isStruct()) - continue; - - ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand()); - if (!IdxVal || (GEPI.isBoundedSequential() && - IdxVal->getZExtValue() >= GEPI.getSequentialNumElements())) - return false; - } - - return llvm::all_of(U->users(), - [](User *UU) { return isSafeSROAElementUse(UU); }); -} - -/// Return true if the specified instruction is a safe user of a derived -/// expression from a global that we want to SROA. -static bool isSafeSROAElementUse(Value *V) { - // We might have a dead and dangling constant hanging off of here. - if (Constant *C = dyn_cast<Constant>(V)) - return isSafeToDestroyConstant(C); - - Instruction *I = dyn_cast<Instruction>(V); - if (!I) return false; - - // Loads are ok. - if (isa<LoadInst>(I)) return true; - - // Stores *to* the pointer are ok. - if (StoreInst *SI = dyn_cast<StoreInst>(I)) - return SI->getOperand(0) != V; - - // Otherwise, it must be a GEP. Check it and its users are safe to SRA. - return isa<GetElementPtrInst>(I) && isSafeSROAGEP(I); -} - -/// Look at all uses of the global and decide whether it is safe for us to -/// perform this transformation. -static bool GlobalUsersSafeToSRA(GlobalValue *GV) { - for (User *U : GV->users()) { - // The user of the global must be a GEP Inst or a ConstantExpr GEP. - if (!isa<GetElementPtrInst>(U) && - (!isa<ConstantExpr>(U) || - cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr)) - return false; - - // Check the gep and it's users are safe to SRA - if (!isSafeSROAGEP(U)) - return false; - } - - return true; -} - -/// Copy over the debug info for a variable to its SRA replacements. -static void transferSRADebugInfo(GlobalVariable *GV, GlobalVariable *NGV, - uint64_t FragmentOffsetInBits, - uint64_t FragmentSizeInBits, - unsigned NumElements) { - SmallVector<DIGlobalVariableExpression *, 1> GVs; - GV->getDebugInfo(GVs); - for (auto *GVE : GVs) { - DIVariable *Var = GVE->getVariable(); - DIExpression *Expr = GVE->getExpression(); - if (NumElements > 1) { - if (auto E = DIExpression::createFragmentExpression( - Expr, FragmentOffsetInBits, FragmentSizeInBits)) - Expr = *E; - else - return; - } - auto *NGVE = DIGlobalVariableExpression::get(GVE->getContext(), Var, Expr); - NGV->addDebugInfo(NGVE); - } -} - -/// Perform scalar replacement of aggregates on the specified global variable. -/// This opens the door for other optimizations by exposing the behavior of the -/// program in a more fine-grained way. We have determined that this -/// transformation is safe already. We return the first global variable we -/// insert so that the caller can reprocess it. -static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &DL) { - // Make sure this global only has simple uses that we can SRA. - if (!GlobalUsersSafeToSRA(GV)) - return nullptr; - - assert(GV->hasLocalLinkage()); - Constant *Init = GV->getInitializer(); - Type *Ty = Init->getType(); - - std::vector<GlobalVariable *> NewGlobals; - Module::GlobalListType &Globals = GV->getParent()->getGlobalList(); - - // Get the alignment of the global, either explicit or target-specific. - unsigned StartAlignment = GV->getAlignment(); - if (StartAlignment == 0) - StartAlignment = DL.getABITypeAlignment(GV->getType()); - - if (StructType *STy = dyn_cast<StructType>(Ty)) { - unsigned NumElements = STy->getNumElements(); - NewGlobals.reserve(NumElements); - const StructLayout &Layout = *DL.getStructLayout(STy); - for (unsigned i = 0, e = NumElements; i != e; ++i) { - Constant *In = Init->getAggregateElement(i); - assert(In && "Couldn't get element of initializer?"); - GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false, - GlobalVariable::InternalLinkage, - In, GV->getName()+"."+Twine(i), - GV->getThreadLocalMode(), - GV->getType()->getAddressSpace()); - NGV->setExternallyInitialized(GV->isExternallyInitialized()); - NGV->copyAttributesFrom(GV); - Globals.push_back(NGV); - NewGlobals.push_back(NGV); - - // Calculate the known alignment of the field. If the original aggregate - // had 256 byte alignment for example, something might depend on that: - // propagate info to each field. - uint64_t FieldOffset = Layout.getElementOffset(i); - unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset); - if (NewAlign > DL.getABITypeAlignment(STy->getElementType(i))) - NGV->setAlignment(NewAlign); - - // Copy over the debug info for the variable. - uint64_t Size = DL.getTypeAllocSizeInBits(NGV->getValueType()); - uint64_t FragmentOffsetInBits = Layout.getElementOffsetInBits(i); - transferSRADebugInfo(GV, NGV, FragmentOffsetInBits, Size, NumElements); - } - } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) { - unsigned NumElements = STy->getNumElements(); - if (NumElements > 16 && GV->hasNUsesOrMore(16)) - return nullptr; // It's not worth it. - NewGlobals.reserve(NumElements); - auto ElTy = STy->getElementType(); - uint64_t EltSize = DL.getTypeAllocSize(ElTy); - unsigned EltAlign = DL.getABITypeAlignment(ElTy); - uint64_t FragmentSizeInBits = DL.getTypeAllocSizeInBits(ElTy); - for (unsigned i = 0, e = NumElements; i != e; ++i) { - Constant *In = Init->getAggregateElement(i); - assert(In && "Couldn't get element of initializer?"); - - GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false, - GlobalVariable::InternalLinkage, - In, GV->getName()+"."+Twine(i), - GV->getThreadLocalMode(), - GV->getType()->getAddressSpace()); - NGV->setExternallyInitialized(GV->isExternallyInitialized()); - NGV->copyAttributesFrom(GV); - Globals.push_back(NGV); - NewGlobals.push_back(NGV); - - // Calculate the known alignment of the field. If the original aggregate - // had 256 byte alignment for example, something might depend on that: - // propagate info to each field. - unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i); - if (NewAlign > EltAlign) - NGV->setAlignment(NewAlign); - transferSRADebugInfo(GV, NGV, FragmentSizeInBits * i, FragmentSizeInBits, - NumElements); - } - } - - if (NewGlobals.empty()) - return nullptr; - - LLVM_DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV << "\n"); - - Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext())); - - // Loop over all of the uses of the global, replacing the constantexpr geps, - // with smaller constantexpr geps or direct references. - while (!GV->use_empty()) { - User *GEP = GV->user_back(); - assert(((isa<ConstantExpr>(GEP) && - cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)|| - isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!"); - - // Ignore the 1th operand, which has to be zero or else the program is quite - // broken (undefined). Get the 2nd operand, which is the structure or array - // index. - unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue(); - if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access. - - Value *NewPtr = NewGlobals[Val]; - Type *NewTy = NewGlobals[Val]->getValueType(); - - // Form a shorter GEP if needed. - if (GEP->getNumOperands() > 3) { - if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) { - SmallVector<Constant*, 8> Idxs; - Idxs.push_back(NullInt); - for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i) - Idxs.push_back(CE->getOperand(i)); - NewPtr = - ConstantExpr::getGetElementPtr(NewTy, cast<Constant>(NewPtr), Idxs); - } else { - GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP); - SmallVector<Value*, 8> Idxs; - Idxs.push_back(NullInt); - for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i) - Idxs.push_back(GEPI->getOperand(i)); - NewPtr = GetElementPtrInst::Create( - NewTy, NewPtr, Idxs, GEPI->getName() + "." + Twine(Val), GEPI); - } - } - GEP->replaceAllUsesWith(NewPtr); - - if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP)) - GEPI->eraseFromParent(); - else - cast<ConstantExpr>(GEP)->destroyConstant(); - } - - // Delete the old global, now that it is dead. - Globals.erase(GV); - ++NumSRA; - - // Loop over the new globals array deleting any globals that are obviously - // dead. This can arise due to scalarization of a structure or an array that - // has elements that are dead. - unsigned FirstGlobal = 0; - for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i) - if (NewGlobals[i]->use_empty()) { - Globals.erase(NewGlobals[i]); - if (FirstGlobal == i) ++FirstGlobal; - } - - return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : nullptr; -} - -/// Return true if all users of the specified value will trap if the value is -/// dynamically null. PHIs keeps track of any phi nodes we've seen to avoid -/// reprocessing them. -static bool AllUsesOfValueWillTrapIfNull(const Value *V, - SmallPtrSetImpl<const PHINode*> &PHIs) { - for (const User *U : V->users()) { - if (const Instruction *I = dyn_cast<Instruction>(U)) { - // If null pointer is considered valid, then all uses are non-trapping. - // Non address-space 0 globals have already been pruned by the caller. - if (NullPointerIsDefined(I->getFunction())) - return false; - } - if (isa<LoadInst>(U)) { - // Will trap. - } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) { - if (SI->getOperand(0) == V) { - //cerr << "NONTRAPPING USE: " << *U; - return false; // Storing the value. - } - } else if (const CallInst *CI = dyn_cast<CallInst>(U)) { - if (CI->getCalledValue() != V) { - //cerr << "NONTRAPPING USE: " << *U; - return false; // Not calling the ptr - } - } else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) { - if (II->getCalledValue() != V) { - //cerr << "NONTRAPPING USE: " << *U; - return false; // Not calling the ptr - } - } else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) { - if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false; - } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) { - if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false; - } else if (const PHINode *PN = dyn_cast<PHINode>(U)) { - // If we've already seen this phi node, ignore it, it has already been - // checked. - if (PHIs.insert(PN).second && !AllUsesOfValueWillTrapIfNull(PN, PHIs)) - return false; - } else if (isa<ICmpInst>(U) && - isa<ConstantPointerNull>(U->getOperand(1))) { - // Ignore icmp X, null - } else { - //cerr << "NONTRAPPING USE: " << *U; - return false; - } - } - return true; -} - -/// Return true if all uses of any loads from GV will trap if the loaded value -/// is null. Note that this also permits comparisons of the loaded value -/// against null, as a special case. -static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) { - for (const User *U : GV->users()) - if (const LoadInst *LI = dyn_cast<LoadInst>(U)) { - SmallPtrSet<const PHINode*, 8> PHIs; - if (!AllUsesOfValueWillTrapIfNull(LI, PHIs)) - return false; - } else if (isa<StoreInst>(U)) { - // Ignore stores to the global. - } else { - // We don't know or understand this user, bail out. - //cerr << "UNKNOWN USER OF GLOBAL!: " << *U; - return false; - } - return true; -} - -static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) { - bool Changed = false; - for (auto UI = V->user_begin(), E = V->user_end(); UI != E; ) { - Instruction *I = cast<Instruction>(*UI++); - // Uses are non-trapping if null pointer is considered valid. - // Non address-space 0 globals are already pruned by the caller. - if (NullPointerIsDefined(I->getFunction())) - return false; - if (LoadInst *LI = dyn_cast<LoadInst>(I)) { - LI->setOperand(0, NewV); - Changed = true; - } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) { - if (SI->getOperand(1) == V) { - SI->setOperand(1, NewV); - Changed = true; - } - } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) { - CallSite CS(I); - if (CS.getCalledValue() == V) { - // Calling through the pointer! Turn into a direct call, but be careful - // that the pointer is not also being passed as an argument. - CS.setCalledFunction(NewV); - Changed = true; - bool PassedAsArg = false; - for (unsigned i = 0, e = CS.arg_size(); i != e; ++i) - if (CS.getArgument(i) == V) { - PassedAsArg = true; - CS.setArgument(i, NewV); - } - - if (PassedAsArg) { - // Being passed as an argument also. Be careful to not invalidate UI! - UI = V->user_begin(); - } - } - } else if (CastInst *CI = dyn_cast<CastInst>(I)) { - Changed |= OptimizeAwayTrappingUsesOfValue(CI, - ConstantExpr::getCast(CI->getOpcode(), - NewV, CI->getType())); - if (CI->use_empty()) { - Changed = true; - CI->eraseFromParent(); - } - } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) { - // Should handle GEP here. - SmallVector<Constant*, 8> Idxs; - Idxs.reserve(GEPI->getNumOperands()-1); - for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end(); - i != e; ++i) - if (Constant *C = dyn_cast<Constant>(*i)) - Idxs.push_back(C); - else - break; - if (Idxs.size() == GEPI->getNumOperands()-1) - Changed |= OptimizeAwayTrappingUsesOfValue( - GEPI, ConstantExpr::getGetElementPtr(nullptr, NewV, Idxs)); - if (GEPI->use_empty()) { - Changed = true; - GEPI->eraseFromParent(); - } - } - } - - return Changed; -} - -/// The specified global has only one non-null value stored into it. If there -/// are uses of the loaded value that would trap if the loaded value is -/// dynamically null, then we know that they cannot be reachable with a null -/// optimize away the load. -static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV, - const DataLayout &DL, - TargetLibraryInfo *TLI) { - bool Changed = false; - - // Keep track of whether we are able to remove all the uses of the global - // other than the store that defines it. - bool AllNonStoreUsesGone = true; - - // Replace all uses of loads with uses of uses of the stored value. - for (Value::user_iterator GUI = GV->user_begin(), E = GV->user_end(); GUI != E;){ - User *GlobalUser = *GUI++; - if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) { - Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV); - // If we were able to delete all uses of the loads - if (LI->use_empty()) { - LI->eraseFromParent(); - Changed = true; - } else { - AllNonStoreUsesGone = false; - } - } else if (isa<StoreInst>(GlobalUser)) { - // Ignore the store that stores "LV" to the global. - assert(GlobalUser->getOperand(1) == GV && - "Must be storing *to* the global"); - } else { - AllNonStoreUsesGone = false; - - // If we get here we could have other crazy uses that are transitively - // loaded. - assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) || - isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser) || - isa<BitCastInst>(GlobalUser) || - isa<GetElementPtrInst>(GlobalUser)) && - "Only expect load and stores!"); - } - } - - if (Changed) { - LLVM_DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV - << "\n"); - ++NumGlobUses; - } - - // If we nuked all of the loads, then none of the stores are needed either, - // nor is the global. - if (AllNonStoreUsesGone) { - if (isLeakCheckerRoot(GV)) { - Changed |= CleanupPointerRootUsers(GV, TLI); - } else { - Changed = true; - CleanupConstantGlobalUsers(GV, nullptr, DL, TLI); - } - if (GV->use_empty()) { - LLVM_DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n"); - Changed = true; - GV->eraseFromParent(); - ++NumDeleted; - } - } - return Changed; -} - -/// Walk the use list of V, constant folding all of the instructions that are -/// foldable. -static void ConstantPropUsersOf(Value *V, const DataLayout &DL, - TargetLibraryInfo *TLI) { - for (Value::user_iterator UI = V->user_begin(), E = V->user_end(); UI != E; ) - if (Instruction *I = dyn_cast<Instruction>(*UI++)) - if (Constant *NewC = ConstantFoldInstruction(I, DL, TLI)) { - I->replaceAllUsesWith(NewC); - - // Advance UI to the next non-I use to avoid invalidating it! - // Instructions could multiply use V. - while (UI != E && *UI == I) - ++UI; - if (isInstructionTriviallyDead(I, TLI)) - I->eraseFromParent(); - } -} - -/// This function takes the specified global variable, and transforms the -/// program as if it always contained the result of the specified malloc. -/// Because it is always the result of the specified malloc, there is no reason -/// to actually DO the malloc. Instead, turn the malloc into a global, and any -/// loads of GV as uses of the new global. -static GlobalVariable * -OptimizeGlobalAddressOfMalloc(GlobalVariable *GV, CallInst *CI, Type *AllocTy, - ConstantInt *NElements, const DataLayout &DL, - TargetLibraryInfo *TLI) { - LLVM_DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI - << '\n'); - - Type *GlobalType; - if (NElements->getZExtValue() == 1) - GlobalType = AllocTy; - else - // If we have an array allocation, the global variable is of an array. - GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue()); - - // Create the new global variable. The contents of the malloc'd memory is - // undefined, so initialize with an undef value. - GlobalVariable *NewGV = new GlobalVariable( - *GV->getParent(), GlobalType, false, GlobalValue::InternalLinkage, - UndefValue::get(GlobalType), GV->getName() + ".body", nullptr, - GV->getThreadLocalMode()); - - // If there are bitcast users of the malloc (which is typical, usually we have - // a malloc + bitcast) then replace them with uses of the new global. Update - // other users to use the global as well. - BitCastInst *TheBC = nullptr; - while (!CI->use_empty()) { - Instruction *User = cast<Instruction>(CI->user_back()); - if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) { - if (BCI->getType() == NewGV->getType()) { - BCI->replaceAllUsesWith(NewGV); - BCI->eraseFromParent(); - } else { - BCI->setOperand(0, NewGV); - } - } else { - if (!TheBC) - TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI); - User->replaceUsesOfWith(CI, TheBC); - } - } - - Constant *RepValue = NewGV; - if (NewGV->getType() != GV->getValueType()) - RepValue = ConstantExpr::getBitCast(RepValue, GV->getValueType()); - - // If there is a comparison against null, we will insert a global bool to - // keep track of whether the global was initialized yet or not. - GlobalVariable *InitBool = - new GlobalVariable(Type::getInt1Ty(GV->getContext()), false, - GlobalValue::InternalLinkage, - ConstantInt::getFalse(GV->getContext()), - GV->getName()+".init", GV->getThreadLocalMode()); - bool InitBoolUsed = false; - - // Loop over all uses of GV, processing them in turn. - while (!GV->use_empty()) { - if (StoreInst *SI = dyn_cast<StoreInst>(GV->user_back())) { - // The global is initialized when the store to it occurs. - new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, 0, - SI->getOrdering(), SI->getSyncScopeID(), SI); - SI->eraseFromParent(); - continue; - } - - LoadInst *LI = cast<LoadInst>(GV->user_back()); - while (!LI->use_empty()) { - Use &LoadUse = *LI->use_begin(); - ICmpInst *ICI = dyn_cast<ICmpInst>(LoadUse.getUser()); - if (!ICI) { - LoadUse = RepValue; - continue; - } - - // Replace the cmp X, 0 with a use of the bool value. - // Sink the load to where the compare was, if atomic rules allow us to. - Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", false, 0, - LI->getOrdering(), LI->getSyncScopeID(), - LI->isUnordered() ? (Instruction*)ICI : LI); - InitBoolUsed = true; - switch (ICI->getPredicate()) { - default: llvm_unreachable("Unknown ICmp Predicate!"); - case ICmpInst::ICMP_ULT: - case ICmpInst::ICMP_SLT: // X < null -> always false - LV = ConstantInt::getFalse(GV->getContext()); - break; - case ICmpInst::ICMP_ULE: - case ICmpInst::ICMP_SLE: - case ICmpInst::ICMP_EQ: - LV = BinaryOperator::CreateNot(LV, "notinit", ICI); - break; - case ICmpInst::ICMP_NE: - case ICmpInst::ICMP_UGE: - case ICmpInst::ICMP_SGE: - case ICmpInst::ICMP_UGT: - case ICmpInst::ICMP_SGT: - break; // no change. - } - ICI->replaceAllUsesWith(LV); - ICI->eraseFromParent(); - } - LI->eraseFromParent(); - } - - // If the initialization boolean was used, insert it, otherwise delete it. - if (!InitBoolUsed) { - while (!InitBool->use_empty()) // Delete initializations - cast<StoreInst>(InitBool->user_back())->eraseFromParent(); - delete InitBool; - } else - GV->getParent()->getGlobalList().insert(GV->getIterator(), InitBool); - - // Now the GV is dead, nuke it and the malloc.. - GV->eraseFromParent(); - CI->eraseFromParent(); - - // To further other optimizations, loop over all users of NewGV and try to - // constant prop them. This will promote GEP instructions with constant - // indices into GEP constant-exprs, which will allow global-opt to hack on it. - ConstantPropUsersOf(NewGV, DL, TLI); - if (RepValue != NewGV) - ConstantPropUsersOf(RepValue, DL, TLI); - - return NewGV; -} - -/// Scan the use-list of V checking to make sure that there are no complex uses -/// of V. We permit simple things like dereferencing the pointer, but not -/// storing through the address, unless it is to the specified global. -static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V, - const GlobalVariable *GV, - SmallPtrSetImpl<const PHINode*> &PHIs) { - for (const User *U : V->users()) { - const Instruction *Inst = cast<Instruction>(U); - - if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) { - continue; // Fine, ignore. - } - - if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { - if (SI->getOperand(0) == V && SI->getOperand(1) != GV) - return false; // Storing the pointer itself... bad. - continue; // Otherwise, storing through it, or storing into GV... fine. - } - - // Must index into the array and into the struct. - if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) { - if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs)) - return false; - continue; - } - - if (const PHINode *PN = dyn_cast<PHINode>(Inst)) { - // PHIs are ok if all uses are ok. Don't infinitely recurse through PHI - // cycles. - if (PHIs.insert(PN).second) - if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs)) - return false; - continue; - } - - if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) { - if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs)) - return false; - continue; - } - - return false; - } - return true; -} - -/// The Alloc pointer is stored into GV somewhere. Transform all uses of the -/// allocation into loads from the global and uses of the resultant pointer. -/// Further, delete the store into GV. This assumes that these value pass the -/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate. -static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc, - GlobalVariable *GV) { - while (!Alloc->use_empty()) { - Instruction *U = cast<Instruction>(*Alloc->user_begin()); - Instruction *InsertPt = U; - if (StoreInst *SI = dyn_cast<StoreInst>(U)) { - // If this is the store of the allocation into the global, remove it. - if (SI->getOperand(1) == GV) { - SI->eraseFromParent(); - continue; - } - } else if (PHINode *PN = dyn_cast<PHINode>(U)) { - // Insert the load in the corresponding predecessor, not right before the - // PHI. - InsertPt = PN->getIncomingBlock(*Alloc->use_begin())->getTerminator(); - } else if (isa<BitCastInst>(U)) { - // Must be bitcast between the malloc and store to initialize the global. - ReplaceUsesOfMallocWithGlobal(U, GV); - U->eraseFromParent(); - continue; - } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) { - // If this is a "GEP bitcast" and the user is a store to the global, then - // just process it as a bitcast. - if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse()) - if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->user_back())) - if (SI->getOperand(1) == GV) { - // Must be bitcast GEP between the malloc and store to initialize - // the global. - ReplaceUsesOfMallocWithGlobal(GEPI, GV); - GEPI->eraseFromParent(); - continue; - } - } - - // Insert a load from the global, and use it instead of the malloc. - Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt); - U->replaceUsesOfWith(Alloc, NL); - } -} - -/// Verify that all uses of V (a load, or a phi of a load) are simple enough to -/// perform heap SRA on. This permits GEP's that index through the array and -/// struct field, icmps of null, and PHIs. -static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V, - SmallPtrSetImpl<const PHINode*> &LoadUsingPHIs, - SmallPtrSetImpl<const PHINode*> &LoadUsingPHIsPerLoad) { - // We permit two users of the load: setcc comparing against the null - // pointer, and a getelementptr of a specific form. - for (const User *U : V->users()) { - const Instruction *UI = cast<Instruction>(U); - - // Comparison against null is ok. - if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UI)) { - if (!isa<ConstantPointerNull>(ICI->getOperand(1))) - return false; - continue; - } - - // getelementptr is also ok, but only a simple form. - if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(UI)) { - // Must index into the array and into the struct. - if (GEPI->getNumOperands() < 3) - return false; - - // Otherwise the GEP is ok. - continue; - } - - if (const PHINode *PN = dyn_cast<PHINode>(UI)) { - if (!LoadUsingPHIsPerLoad.insert(PN).second) - // This means some phi nodes are dependent on each other. - // Avoid infinite looping! - return false; - if (!LoadUsingPHIs.insert(PN).second) - // If we have already analyzed this PHI, then it is safe. - continue; - - // Make sure all uses of the PHI are simple enough to transform. - if (!LoadUsesSimpleEnoughForHeapSRA(PN, - LoadUsingPHIs, LoadUsingPHIsPerLoad)) - return false; - - continue; - } - - // Otherwise we don't know what this is, not ok. - return false; - } - - return true; -} - -/// If all users of values loaded from GV are simple enough to perform HeapSRA, -/// return true. -static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV, - Instruction *StoredVal) { - SmallPtrSet<const PHINode*, 32> LoadUsingPHIs; - SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad; - for (const User *U : GV->users()) - if (const LoadInst *LI = dyn_cast<LoadInst>(U)) { - if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs, - LoadUsingPHIsPerLoad)) - return false; - LoadUsingPHIsPerLoad.clear(); - } - - // If we reach here, we know that all uses of the loads and transitive uses - // (through PHI nodes) are simple enough to transform. However, we don't know - // that all inputs the to the PHI nodes are in the same equivalence sets. - // Check to verify that all operands of the PHIs are either PHIS that can be - // transformed, loads from GV, or MI itself. - for (const PHINode *PN : LoadUsingPHIs) { - for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) { - Value *InVal = PN->getIncomingValue(op); - - // PHI of the stored value itself is ok. - if (InVal == StoredVal) continue; - - if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) { - // One of the PHIs in our set is (optimistically) ok. - if (LoadUsingPHIs.count(InPN)) - continue; - return false; - } - - // Load from GV is ok. - if (const LoadInst *LI = dyn_cast<LoadInst>(InVal)) - if (LI->getOperand(0) == GV) - continue; - - // UNDEF? NULL? - - // Anything else is rejected. - return false; - } - } - - return true; -} - -static Value *GetHeapSROAValue(Value *V, unsigned FieldNo, - DenseMap<Value *, std::vector<Value *>> &InsertedScalarizedValues, - std::vector<std::pair<PHINode *, unsigned>> &PHIsToRewrite) { - std::vector<Value *> &FieldVals = InsertedScalarizedValues[V]; - - if (FieldNo >= FieldVals.size()) - FieldVals.resize(FieldNo+1); - - // If we already have this value, just reuse the previously scalarized - // version. - if (Value *FieldVal = FieldVals[FieldNo]) - return FieldVal; - - // Depending on what instruction this is, we have several cases. - Value *Result; - if (LoadInst *LI = dyn_cast<LoadInst>(V)) { - // This is a scalarized version of the load from the global. Just create - // a new Load of the scalarized global. - Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo, - InsertedScalarizedValues, - PHIsToRewrite), - LI->getName()+".f"+Twine(FieldNo), LI); - } else { - PHINode *PN = cast<PHINode>(V); - // PN's type is pointer to struct. Make a new PHI of pointer to struct - // field. - - PointerType *PTy = cast<PointerType>(PN->getType()); - StructType *ST = cast<StructType>(PTy->getElementType()); - - unsigned AS = PTy->getAddressSpace(); - PHINode *NewPN = - PHINode::Create(PointerType::get(ST->getElementType(FieldNo), AS), - PN->getNumIncomingValues(), - PN->getName()+".f"+Twine(FieldNo), PN); - Result = NewPN; - PHIsToRewrite.push_back(std::make_pair(PN, FieldNo)); - } - - return FieldVals[FieldNo] = Result; -} - -/// Given a load instruction and a value derived from the load, rewrite the -/// derived value to use the HeapSRoA'd load. -static void RewriteHeapSROALoadUser(Instruction *LoadUser, - DenseMap<Value *, std::vector<Value *>> &InsertedScalarizedValues, - std::vector<std::pair<PHINode *, unsigned>> &PHIsToRewrite) { - // If this is a comparison against null, handle it. - if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) { - assert(isa<ConstantPointerNull>(SCI->getOperand(1))); - // If we have a setcc of the loaded pointer, we can use a setcc of any - // field. - Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0, - InsertedScalarizedValues, PHIsToRewrite); - - Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr, - Constant::getNullValue(NPtr->getType()), - SCI->getName()); - SCI->replaceAllUsesWith(New); - SCI->eraseFromParent(); - return; - } - - // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...' - if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) { - assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2)) - && "Unexpected GEPI!"); - - // Load the pointer for this field. - unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue(); - Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo, - InsertedScalarizedValues, PHIsToRewrite); - - // Create the new GEP idx vector. - SmallVector<Value*, 8> GEPIdx; - GEPIdx.push_back(GEPI->getOperand(1)); - GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end()); - - Value *NGEPI = GetElementPtrInst::Create(GEPI->getResultElementType(), NewPtr, GEPIdx, - GEPI->getName(), GEPI); - GEPI->replaceAllUsesWith(NGEPI); - GEPI->eraseFromParent(); - return; - } - - // Recursively transform the users of PHI nodes. This will lazily create the - // PHIs that are needed for individual elements. Keep track of what PHIs we - // see in InsertedScalarizedValues so that we don't get infinite loops (very - // antisocial). If the PHI is already in InsertedScalarizedValues, it has - // already been seen first by another load, so its uses have already been - // processed. - PHINode *PN = cast<PHINode>(LoadUser); - if (!InsertedScalarizedValues.insert(std::make_pair(PN, - std::vector<Value *>())).second) - return; - - // If this is the first time we've seen this PHI, recursively process all - // users. - for (auto UI = PN->user_begin(), E = PN->user_end(); UI != E;) { - Instruction *User = cast<Instruction>(*UI++); - RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite); - } -} - -/// We are performing Heap SRoA on a global. Ptr is a value loaded from the -/// global. Eliminate all uses of Ptr, making them use FieldGlobals instead. -/// All uses of loaded values satisfy AllGlobalLoadUsesSimpleEnoughForHeapSRA. -static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load, - DenseMap<Value *, std::vector<Value *>> &InsertedScalarizedValues, - std::vector<std::pair<PHINode *, unsigned> > &PHIsToRewrite) { - for (auto UI = Load->user_begin(), E = Load->user_end(); UI != E;) { - Instruction *User = cast<Instruction>(*UI++); - RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite); - } - - if (Load->use_empty()) { - Load->eraseFromParent(); - InsertedScalarizedValues.erase(Load); - } -} - -/// CI is an allocation of an array of structures. Break it up into multiple -/// allocations of arrays of the fields. -static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI, - Value *NElems, const DataLayout &DL, - const TargetLibraryInfo *TLI) { - LLVM_DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI - << '\n'); - Type *MAT = getMallocAllocatedType(CI, TLI); - StructType *STy = cast<StructType>(MAT); - - // There is guaranteed to be at least one use of the malloc (storing - // it into GV). If there are other uses, change them to be uses of - // the global to simplify later code. This also deletes the store - // into GV. - ReplaceUsesOfMallocWithGlobal(CI, GV); - - // Okay, at this point, there are no users of the malloc. Insert N - // new mallocs at the same place as CI, and N globals. - std::vector<Value *> FieldGlobals; - std::vector<Value *> FieldMallocs; - - SmallVector<OperandBundleDef, 1> OpBundles; - CI->getOperandBundlesAsDefs(OpBundles); - - unsigned AS = GV->getType()->getPointerAddressSpace(); - for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){ - Type *FieldTy = STy->getElementType(FieldNo); - PointerType *PFieldTy = PointerType::get(FieldTy, AS); - - GlobalVariable *NGV = new GlobalVariable( - *GV->getParent(), PFieldTy, false, GlobalValue::InternalLinkage, - Constant::getNullValue(PFieldTy), GV->getName() + ".f" + Twine(FieldNo), - nullptr, GV->getThreadLocalMode()); - NGV->copyAttributesFrom(GV); - FieldGlobals.push_back(NGV); - - unsigned TypeSize = DL.getTypeAllocSize(FieldTy); - if (StructType *ST = dyn_cast<StructType>(FieldTy)) - TypeSize = DL.getStructLayout(ST)->getSizeInBytes(); - Type *IntPtrTy = DL.getIntPtrType(CI->getType()); - Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy, - ConstantInt::get(IntPtrTy, TypeSize), - NElems, OpBundles, nullptr, - CI->getName() + ".f" + Twine(FieldNo)); - FieldMallocs.push_back(NMI); - new StoreInst(NMI, NGV, CI); - } - - // The tricky aspect of this transformation is handling the case when malloc - // fails. In the original code, malloc failing would set the result pointer - // of malloc to null. In this case, some mallocs could succeed and others - // could fail. As such, we emit code that looks like this: - // F0 = malloc(field0) - // F1 = malloc(field1) - // F2 = malloc(field2) - // if (F0 == 0 || F1 == 0 || F2 == 0) { - // if (F0) { free(F0); F0 = 0; } - // if (F1) { free(F1); F1 = 0; } - // if (F2) { free(F2); F2 = 0; } - // } - // The malloc can also fail if its argument is too large. - Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0); - Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0), - ConstantZero, "isneg"); - for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) { - Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i], - Constant::getNullValue(FieldMallocs[i]->getType()), - "isnull"); - RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI); - } - - // Split the basic block at the old malloc. - BasicBlock *OrigBB = CI->getParent(); - BasicBlock *ContBB = - OrigBB->splitBasicBlock(CI->getIterator(), "malloc_cont"); - - // Create the block to check the first condition. Put all these blocks at the - // end of the function as they are unlikely to be executed. - BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(), - "malloc_ret_null", - OrigBB->getParent()); - - // Remove the uncond branch from OrigBB to ContBB, turning it into a cond - // branch on RunningOr. - OrigBB->getTerminator()->eraseFromParent(); - BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB); - - // Within the NullPtrBlock, we need to emit a comparison and branch for each - // pointer, because some may be null while others are not. - for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { - Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock); - Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal, - Constant::getNullValue(GVVal->getType())); - BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it", - OrigBB->getParent()); - BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next", - OrigBB->getParent()); - Instruction *BI = BranchInst::Create(FreeBlock, NextBlock, - Cmp, NullPtrBlock); - - // Fill in FreeBlock. - CallInst::CreateFree(GVVal, OpBundles, BI); - new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i], - FreeBlock); - BranchInst::Create(NextBlock, FreeBlock); - - NullPtrBlock = NextBlock; - } - - BranchInst::Create(ContBB, NullPtrBlock); - - // CI is no longer needed, remove it. - CI->eraseFromParent(); - - /// As we process loads, if we can't immediately update all uses of the load, - /// keep track of what scalarized loads are inserted for a given load. - DenseMap<Value *, std::vector<Value *>> InsertedScalarizedValues; - InsertedScalarizedValues[GV] = FieldGlobals; - - std::vector<std::pair<PHINode *, unsigned>> PHIsToRewrite; - - // Okay, the malloc site is completely handled. All of the uses of GV are now - // loads, and all uses of those loads are simple. Rewrite them to use loads - // of the per-field globals instead. - for (auto UI = GV->user_begin(), E = GV->user_end(); UI != E;) { - Instruction *User = cast<Instruction>(*UI++); - - if (LoadInst *LI = dyn_cast<LoadInst>(User)) { - RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite); - continue; - } - - // Must be a store of null. - StoreInst *SI = cast<StoreInst>(User); - assert(isa<ConstantPointerNull>(SI->getOperand(0)) && - "Unexpected heap-sra user!"); - - // Insert a store of null into each global. - for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) { - Type *ValTy = cast<GlobalValue>(FieldGlobals[i])->getValueType(); - Constant *Null = Constant::getNullValue(ValTy); - new StoreInst(Null, FieldGlobals[i], SI); - } - // Erase the original store. - SI->eraseFromParent(); - } - - // While we have PHIs that are interesting to rewrite, do it. - while (!PHIsToRewrite.empty()) { - PHINode *PN = PHIsToRewrite.back().first; - unsigned FieldNo = PHIsToRewrite.back().second; - PHIsToRewrite.pop_back(); - PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]); - assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi"); - - // Add all the incoming values. This can materialize more phis. - for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) { - Value *InVal = PN->getIncomingValue(i); - InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues, - PHIsToRewrite); - FieldPN->addIncoming(InVal, PN->getIncomingBlock(i)); - } - } - - // Drop all inter-phi links and any loads that made it this far. - for (DenseMap<Value *, std::vector<Value *>>::iterator - I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end(); - I != E; ++I) { - if (PHINode *PN = dyn_cast<PHINode>(I->first)) - PN->dropAllReferences(); - else if (LoadInst *LI = dyn_cast<LoadInst>(I->first)) - LI->dropAllReferences(); - } - - // Delete all the phis and loads now that inter-references are dead. - for (DenseMap<Value *, std::vector<Value *>>::iterator - I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end(); - I != E; ++I) { - if (PHINode *PN = dyn_cast<PHINode>(I->first)) - PN->eraseFromParent(); - else if (LoadInst *LI = dyn_cast<LoadInst>(I->first)) - LI->eraseFromParent(); - } - - // The old global is now dead, remove it. - GV->eraseFromParent(); - - ++NumHeapSRA; - return cast<GlobalVariable>(FieldGlobals[0]); -} - -/// This function is called when we see a pointer global variable with a single -/// value stored it that is a malloc or cast of malloc. -static bool tryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV, CallInst *CI, - Type *AllocTy, - AtomicOrdering Ordering, - const DataLayout &DL, - TargetLibraryInfo *TLI) { - // If this is a malloc of an abstract type, don't touch it. - if (!AllocTy->isSized()) - return false; - - // We can't optimize this global unless all uses of it are *known* to be - // of the malloc value, not of the null initializer value (consider a use - // that compares the global's value against zero to see if the malloc has - // been reached). To do this, we check to see if all uses of the global - // would trap if the global were null: this proves that they must all - // happen after the malloc. - if (!AllUsesOfLoadedValueWillTrapIfNull(GV)) - return false; - - // We can't optimize this if the malloc itself is used in a complex way, - // for example, being stored into multiple globals. This allows the - // malloc to be stored into the specified global, loaded icmp'd, and - // GEP'd. These are all things we could transform to using the global - // for. - SmallPtrSet<const PHINode*, 8> PHIs; - if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs)) - return false; - - // If we have a global that is only initialized with a fixed size malloc, - // transform the program to use global memory instead of malloc'd memory. - // This eliminates dynamic allocation, avoids an indirection accessing the - // data, and exposes the resultant global to further GlobalOpt. - // We cannot optimize the malloc if we cannot determine malloc array size. - Value *NElems = getMallocArraySize(CI, DL, TLI, true); - if (!NElems) - return false; - - if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems)) - // Restrict this transformation to only working on small allocations - // (2048 bytes currently), as we don't want to introduce a 16M global or - // something. - if (NElements->getZExtValue() * DL.getTypeAllocSize(AllocTy) < 2048) { - OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, DL, TLI); - return true; - } - - // If the allocation is an array of structures, consider transforming this - // into multiple malloc'd arrays, one for each field. This is basically - // SRoA for malloc'd memory. - - if (Ordering != AtomicOrdering::NotAtomic) - return false; - - // If this is an allocation of a fixed size array of structs, analyze as a - // variable size array. malloc [100 x struct],1 -> malloc struct, 100 - if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1)) - if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy)) - AllocTy = AT->getElementType(); - - StructType *AllocSTy = dyn_cast<StructType>(AllocTy); - if (!AllocSTy) - return false; - - // This the structure has an unreasonable number of fields, leave it - // alone. - if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 && - AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) { - - // If this is a fixed size array, transform the Malloc to be an alloc of - // structs. malloc [100 x struct],1 -> malloc struct, 100 - if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI, TLI))) { - Type *IntPtrTy = DL.getIntPtrType(CI->getType()); - unsigned TypeSize = DL.getStructLayout(AllocSTy)->getSizeInBytes(); - Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize); - Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements()); - SmallVector<OperandBundleDef, 1> OpBundles; - CI->getOperandBundlesAsDefs(OpBundles); - Instruction *Malloc = - CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy, AllocSize, NumElements, - OpBundles, nullptr, CI->getName()); - Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI); - CI->replaceAllUsesWith(Cast); - CI->eraseFromParent(); - if (BitCastInst *BCI = dyn_cast<BitCastInst>(Malloc)) - CI = cast<CallInst>(BCI->getOperand(0)); - else - CI = cast<CallInst>(Malloc); - } - - PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, DL, TLI, true), DL, - TLI); - return true; - } - - return false; -} - -// Try to optimize globals based on the knowledge that only one value (besides -// its initializer) is ever stored to the global. -static bool optimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal, - AtomicOrdering Ordering, - const DataLayout &DL, - TargetLibraryInfo *TLI) { - // Ignore no-op GEPs and bitcasts. - StoredOnceVal = StoredOnceVal->stripPointerCasts(); - - // If we are dealing with a pointer global that is initialized to null and - // only has one (non-null) value stored into it, then we can optimize any - // users of the loaded value (often calls and loads) that would trap if the - // value was null. - if (GV->getInitializer()->getType()->isPointerTy() && - GV->getInitializer()->isNullValue() && - !NullPointerIsDefined( - nullptr /* F */, - GV->getInitializer()->getType()->getPointerAddressSpace())) { - if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) { - if (GV->getInitializer()->getType() != SOVC->getType()) - SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType()); - - // Optimize away any trapping uses of the loaded value. - if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, DL, TLI)) - return true; - } else if (CallInst *CI = extractMallocCall(StoredOnceVal, TLI)) { - Type *MallocType = getMallocAllocatedType(CI, TLI); - if (MallocType && tryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, - Ordering, DL, TLI)) - return true; - } - } - - return false; -} - -/// At this point, we have learned that the only two values ever stored into GV -/// are its initializer and OtherVal. See if we can shrink the global into a -/// boolean and select between the two values whenever it is used. This exposes -/// the values to other scalar optimizations. -static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) { - Type *GVElType = GV->getValueType(); - - // If GVElType is already i1, it is already shrunk. If the type of the GV is - // an FP value, pointer or vector, don't do this optimization because a select - // between them is very expensive and unlikely to lead to later - // simplification. In these cases, we typically end up with "cond ? v1 : v2" - // where v1 and v2 both require constant pool loads, a big loss. - if (GVElType == Type::getInt1Ty(GV->getContext()) || - GVElType->isFloatingPointTy() || - GVElType->isPointerTy() || GVElType->isVectorTy()) - return false; - - // Walk the use list of the global seeing if all the uses are load or store. - // If there is anything else, bail out. - for (User *U : GV->users()) - if (!isa<LoadInst>(U) && !isa<StoreInst>(U)) - return false; - - LLVM_DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV << "\n"); - - // Create the new global, initializing it to false. - GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()), - false, - GlobalValue::InternalLinkage, - ConstantInt::getFalse(GV->getContext()), - GV->getName()+".b", - GV->getThreadLocalMode(), - GV->getType()->getAddressSpace()); - NewGV->copyAttributesFrom(GV); - GV->getParent()->getGlobalList().insert(GV->getIterator(), NewGV); - - Constant *InitVal = GV->getInitializer(); - assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) && - "No reason to shrink to bool!"); - - SmallVector<DIGlobalVariableExpression *, 1> GVs; - GV->getDebugInfo(GVs); - - // If initialized to zero and storing one into the global, we can use a cast - // instead of a select to synthesize the desired value. - bool IsOneZero = false; - bool EmitOneOrZero = true; - if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal)){ - IsOneZero = InitVal->isNullValue() && CI->isOne(); - - if (ConstantInt *CIInit = dyn_cast<ConstantInt>(GV->getInitializer())){ - uint64_t ValInit = CIInit->getZExtValue(); - uint64_t ValOther = CI->getZExtValue(); - uint64_t ValMinus = ValOther - ValInit; - - for(auto *GVe : GVs){ - DIGlobalVariable *DGV = GVe->getVariable(); - DIExpression *E = GVe->getExpression(); - - // It is expected that the address of global optimized variable is on - // top of the stack. After optimization, value of that variable will - // be ether 0 for initial value or 1 for other value. The following - // expression should return constant integer value depending on the - // value at global object address: - // val * (ValOther - ValInit) + ValInit: - // DW_OP_deref DW_OP_constu <ValMinus> - // DW_OP_mul DW_OP_constu <ValInit> DW_OP_plus DW_OP_stack_value - SmallVector<uint64_t, 12> Ops = { - dwarf::DW_OP_deref, dwarf::DW_OP_constu, ValMinus, - dwarf::DW_OP_mul, dwarf::DW_OP_constu, ValInit, - dwarf::DW_OP_plus}; - E = DIExpression::prependOpcodes(E, Ops, DIExpression::WithStackValue); - DIGlobalVariableExpression *DGVE = - DIGlobalVariableExpression::get(NewGV->getContext(), DGV, E); - NewGV->addDebugInfo(DGVE); - } - EmitOneOrZero = false; - } - } - - if (EmitOneOrZero) { - // FIXME: This will only emit address for debugger on which will - // be written only 0 or 1. - for(auto *GV : GVs) - NewGV->addDebugInfo(GV); - } - - while (!GV->use_empty()) { - Instruction *UI = cast<Instruction>(GV->user_back()); - if (StoreInst *SI = dyn_cast<StoreInst>(UI)) { - // Change the store into a boolean store. - bool StoringOther = SI->getOperand(0) == OtherVal; - // Only do this if we weren't storing a loaded value. - Value *StoreVal; - if (StoringOther || SI->getOperand(0) == InitVal) { - StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()), - StoringOther); - } else { - // Otherwise, we are storing a previously loaded copy. To do this, - // change the copy from copying the original value to just copying the - // bool. - Instruction *StoredVal = cast<Instruction>(SI->getOperand(0)); - - // If we've already replaced the input, StoredVal will be a cast or - // select instruction. If not, it will be a load of the original - // global. - if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) { - assert(LI->getOperand(0) == GV && "Not a copy!"); - // Insert a new load, to preserve the saved value. - StoreVal = new LoadInst(NewGV, LI->getName()+".b", false, 0, - LI->getOrdering(), LI->getSyncScopeID(), LI); - } else { - assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) && - "This is not a form that we understand!"); - StoreVal = StoredVal->getOperand(0); - assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!"); - } - } - StoreInst *NSI = - new StoreInst(StoreVal, NewGV, false, 0, SI->getOrdering(), - SI->getSyncScopeID(), SI); - NSI->setDebugLoc(SI->getDebugLoc()); - } else { - // Change the load into a load of bool then a select. - LoadInst *LI = cast<LoadInst>(UI); - LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", false, 0, - LI->getOrdering(), LI->getSyncScopeID(), LI); - Instruction *NSI; - if (IsOneZero) - NSI = new ZExtInst(NLI, LI->getType(), "", LI); - else - NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI); - NSI->takeName(LI); - // Since LI is split into two instructions, NLI and NSI both inherit the - // same DebugLoc - NLI->setDebugLoc(LI->getDebugLoc()); - NSI->setDebugLoc(LI->getDebugLoc()); - LI->replaceAllUsesWith(NSI); - } - UI->eraseFromParent(); - } - - // Retain the name of the old global variable. People who are debugging their - // programs may expect these variables to be named the same. - NewGV->takeName(GV); - GV->eraseFromParent(); - return true; -} - -static bool deleteIfDead( - GlobalValue &GV, SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats) { - GV.removeDeadConstantUsers(); - - if (!GV.isDiscardableIfUnused() && !GV.isDeclaration()) - return false; - - if (const Comdat *C = GV.getComdat()) - if (!GV.hasLocalLinkage() && NotDiscardableComdats.count(C)) - return false; - - bool Dead; - if (auto *F = dyn_cast<Function>(&GV)) - Dead = (F->isDeclaration() && F->use_empty()) || F->isDefTriviallyDead(); - else - Dead = GV.use_empty(); - if (!Dead) - return false; - - LLVM_DEBUG(dbgs() << "GLOBAL DEAD: " << GV << "\n"); - GV.eraseFromParent(); - ++NumDeleted; - return true; -} - -static bool isPointerValueDeadOnEntryToFunction( - const Function *F, GlobalValue *GV, - function_ref<DominatorTree &(Function &)> LookupDomTree) { - // Find all uses of GV. We expect them all to be in F, and if we can't - // identify any of the uses we bail out. - // - // On each of these uses, identify if the memory that GV points to is - // used/required/live at the start of the function. If it is not, for example - // if the first thing the function does is store to the GV, the GV can - // possibly be demoted. - // - // We don't do an exhaustive search for memory operations - simply look - // through bitcasts as they're quite common and benign. - const DataLayout &DL = GV->getParent()->getDataLayout(); - SmallVector<LoadInst *, 4> Loads; - SmallVector<StoreInst *, 4> Stores; - for (auto *U : GV->users()) { - if (Operator::getOpcode(U) == Instruction::BitCast) { - for (auto *UU : U->users()) { - if (auto *LI = dyn_cast<LoadInst>(UU)) - Loads.push_back(LI); - else if (auto *SI = dyn_cast<StoreInst>(UU)) - Stores.push_back(SI); - else - return false; - } - continue; - } - - Instruction *I = dyn_cast<Instruction>(U); - if (!I) - return false; - assert(I->getParent()->getParent() == F); - - if (auto *LI = dyn_cast<LoadInst>(I)) - Loads.push_back(LI); - else if (auto *SI = dyn_cast<StoreInst>(I)) - Stores.push_back(SI); - else - return false; - } - - // We have identified all uses of GV into loads and stores. Now check if all - // of them are known not to depend on the value of the global at the function - // entry point. We do this by ensuring that every load is dominated by at - // least one store. - auto &DT = LookupDomTree(*const_cast<Function *>(F)); - - // The below check is quadratic. Check we're not going to do too many tests. - // FIXME: Even though this will always have worst-case quadratic time, we - // could put effort into minimizing the average time by putting stores that - // have been shown to dominate at least one load at the beginning of the - // Stores array, making subsequent dominance checks more likely to succeed - // early. - // - // The threshold here is fairly large because global->local demotion is a - // very powerful optimization should it fire. - const unsigned Threshold = 100; - if (Loads.size() * Stores.size() > Threshold) - return false; - - for (auto *L : Loads) { - auto *LTy = L->getType(); - if (none_of(Stores, [&](const StoreInst *S) { - auto *STy = S->getValueOperand()->getType(); - // The load is only dominated by the store if DomTree says so - // and the number of bits loaded in L is less than or equal to - // the number of bits stored in S. - return DT.dominates(S, L) && - DL.getTypeStoreSize(LTy) <= DL.getTypeStoreSize(STy); - })) - return false; - } - // All loads have known dependences inside F, so the global can be localized. - return true; -} - -/// C may have non-instruction users. Can all of those users be turned into -/// instructions? -static bool allNonInstructionUsersCanBeMadeInstructions(Constant *C) { - // We don't do this exhaustively. The most common pattern that we really need - // to care about is a constant GEP or constant bitcast - so just looking - // through one single ConstantExpr. - // - // The set of constants that this function returns true for must be able to be - // handled by makeAllConstantUsesInstructions. - for (auto *U : C->users()) { - if (isa<Instruction>(U)) - continue; - if (!isa<ConstantExpr>(U)) - // Non instruction, non-constantexpr user; cannot convert this. - return false; - for (auto *UU : U->users()) - if (!isa<Instruction>(UU)) - // A constantexpr used by another constant. We don't try and recurse any - // further but just bail out at this point. - return false; - } - - return true; -} - -/// C may have non-instruction users, and -/// allNonInstructionUsersCanBeMadeInstructions has returned true. Convert the -/// non-instruction users to instructions. -static void makeAllConstantUsesInstructions(Constant *C) { - SmallVector<ConstantExpr*,4> Users; - for (auto *U : C->users()) { - if (isa<ConstantExpr>(U)) - Users.push_back(cast<ConstantExpr>(U)); - else - // We should never get here; allNonInstructionUsersCanBeMadeInstructions - // should not have returned true for C. - assert( - isa<Instruction>(U) && - "Can't transform non-constantexpr non-instruction to instruction!"); - } - - SmallVector<Value*,4> UUsers; - for (auto *U : Users) { - UUsers.clear(); - for (auto *UU : U->users()) - UUsers.push_back(UU); - for (auto *UU : UUsers) { - Instruction *UI = cast<Instruction>(UU); - Instruction *NewU = U->getAsInstruction(); - NewU->insertBefore(UI); - UI->replaceUsesOfWith(U, NewU); - } - // We've replaced all the uses, so destroy the constant. (destroyConstant - // will update value handles and metadata.) - U->destroyConstant(); - } -} - -/// Analyze the specified global variable and optimize -/// it if possible. If we make a change, return true. -static bool processInternalGlobal( - GlobalVariable *GV, const GlobalStatus &GS, TargetLibraryInfo *TLI, - function_ref<DominatorTree &(Function &)> LookupDomTree) { - auto &DL = GV->getParent()->getDataLayout(); - // If this is a first class global and has only one accessing function and - // this function is non-recursive, we replace the global with a local alloca - // in this function. - // - // NOTE: It doesn't make sense to promote non-single-value types since we - // are just replacing static memory to stack memory. - // - // If the global is in different address space, don't bring it to stack. - if (!GS.HasMultipleAccessingFunctions && - GS.AccessingFunction && - GV->getValueType()->isSingleValueType() && - GV->getType()->getAddressSpace() == 0 && - !GV->isExternallyInitialized() && - allNonInstructionUsersCanBeMadeInstructions(GV) && - GS.AccessingFunction->doesNotRecurse() && - isPointerValueDeadOnEntryToFunction(GS.AccessingFunction, GV, - LookupDomTree)) { - const DataLayout &DL = GV->getParent()->getDataLayout(); - - LLVM_DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV << "\n"); - Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction - ->getEntryBlock().begin()); - Type *ElemTy = GV->getValueType(); - // FIXME: Pass Global's alignment when globals have alignment - AllocaInst *Alloca = new AllocaInst(ElemTy, DL.getAllocaAddrSpace(), nullptr, - GV->getName(), &FirstI); - if (!isa<UndefValue>(GV->getInitializer())) - new StoreInst(GV->getInitializer(), Alloca, &FirstI); - - makeAllConstantUsesInstructions(GV); - - GV->replaceAllUsesWith(Alloca); - GV->eraseFromParent(); - ++NumLocalized; - return true; - } - - // If the global is never loaded (but may be stored to), it is dead. - // Delete it now. - if (!GS.IsLoaded) { - LLVM_DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV << "\n"); - - bool Changed; - if (isLeakCheckerRoot(GV)) { - // Delete any constant stores to the global. - Changed = CleanupPointerRootUsers(GV, TLI); - } else { - // Delete any stores we can find to the global. We may not be able to - // make it completely dead though. - Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer(), DL, TLI); - } - - // If the global is dead now, delete it. - if (GV->use_empty()) { - GV->eraseFromParent(); - ++NumDeleted; - Changed = true; - } - return Changed; - - } - if (GS.StoredType <= GlobalStatus::InitializerStored) { - LLVM_DEBUG(dbgs() << "MARKING CONSTANT: " << *GV << "\n"); - GV->setConstant(true); - - // Clean up any obviously simplifiable users now. - CleanupConstantGlobalUsers(GV, GV->getInitializer(), DL, TLI); - - // If the global is dead now, just nuke it. - if (GV->use_empty()) { - LLVM_DEBUG(dbgs() << " *** Marking constant allowed us to simplify " - << "all users and delete global!\n"); - GV->eraseFromParent(); - ++NumDeleted; - return true; - } - - // Fall through to the next check; see if we can optimize further. - ++NumMarked; - } - if (!GV->getInitializer()->getType()->isSingleValueType()) { - const DataLayout &DL = GV->getParent()->getDataLayout(); - if (SRAGlobal(GV, DL)) - return true; - } - if (GS.StoredType == GlobalStatus::StoredOnce && GS.StoredOnceValue) { - // If the initial value for the global was an undef value, and if only - // one other value was stored into it, we can just change the - // initializer to be the stored value, then delete all stores to the - // global. This allows us to mark it constant. - if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) - if (isa<UndefValue>(GV->getInitializer())) { - // Change the initial value here. - GV->setInitializer(SOVConstant); - - // Clean up any obviously simplifiable users now. - CleanupConstantGlobalUsers(GV, GV->getInitializer(), DL, TLI); - - if (GV->use_empty()) { - LLVM_DEBUG(dbgs() << " *** Substituting initializer allowed us to " - << "simplify all users and delete global!\n"); - GV->eraseFromParent(); - ++NumDeleted; - } - ++NumSubstitute; - return true; - } - - // Try to optimize globals based on the knowledge that only one value - // (besides its initializer) is ever stored to the global. - if (optimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GS.Ordering, DL, TLI)) - return true; - - // Otherwise, if the global was not a boolean, we can shrink it to be a - // boolean. - if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) { - if (GS.Ordering == AtomicOrdering::NotAtomic) { - if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) { - ++NumShrunkToBool; - return true; - } - } - } - } - - return false; -} - -/// Analyze the specified global variable and optimize it if possible. If we -/// make a change, return true. -static bool -processGlobal(GlobalValue &GV, TargetLibraryInfo *TLI, - function_ref<DominatorTree &(Function &)> LookupDomTree) { - if (GV.getName().startswith("llvm.")) - return false; - - GlobalStatus GS; - - if (GlobalStatus::analyzeGlobal(&GV, GS)) - return false; - - bool Changed = false; - if (!GS.IsCompared && !GV.hasGlobalUnnamedAddr()) { - auto NewUnnamedAddr = GV.hasLocalLinkage() ? GlobalValue::UnnamedAddr::Global - : GlobalValue::UnnamedAddr::Local; - if (NewUnnamedAddr != GV.getUnnamedAddr()) { - GV.setUnnamedAddr(NewUnnamedAddr); - NumUnnamed++; - Changed = true; - } - } - - // Do more involved optimizations if the global is internal. - if (!GV.hasLocalLinkage()) - return Changed; - - auto *GVar = dyn_cast<GlobalVariable>(&GV); - if (!GVar) - return Changed; - - if (GVar->isConstant() || !GVar->hasInitializer()) - return Changed; - - return processInternalGlobal(GVar, GS, TLI, LookupDomTree) || Changed; -} - -/// Walk all of the direct calls of the specified function, changing them to -/// FastCC. -static void ChangeCalleesToFastCall(Function *F) { - for (User *U : F->users()) { - if (isa<BlockAddress>(U)) - continue; - CallSite CS(cast<Instruction>(U)); - CS.setCallingConv(CallingConv::Fast); - } -} - -static AttributeList StripNest(LLVMContext &C, AttributeList Attrs) { - // There can be at most one attribute set with a nest attribute. - unsigned NestIndex; - if (Attrs.hasAttrSomewhere(Attribute::Nest, &NestIndex)) - return Attrs.removeAttribute(C, NestIndex, Attribute::Nest); - return Attrs; -} - -static void RemoveNestAttribute(Function *F) { - F->setAttributes(StripNest(F->getContext(), F->getAttributes())); - for (User *U : F->users()) { - if (isa<BlockAddress>(U)) - continue; - CallSite CS(cast<Instruction>(U)); - CS.setAttributes(StripNest(F->getContext(), CS.getAttributes())); - } -} - -/// Return true if this is a calling convention that we'd like to change. The -/// idea here is that we don't want to mess with the convention if the user -/// explicitly requested something with performance implications like coldcc, -/// GHC, or anyregcc. -static bool hasChangeableCC(Function *F) { - CallingConv::ID CC = F->getCallingConv(); - - // FIXME: Is it worth transforming x86_stdcallcc and x86_fastcallcc? - if (CC != CallingConv::C && CC != CallingConv::X86_ThisCall) - return false; - - // Don't break the invariant that the inalloca parameter is the only parameter - // passed in memory. - // FIXME: GlobalOpt should remove inalloca when possible and hoist the dynamic - // alloca it uses to the entry block if possible. - if (F->getAttributes().hasAttrSomewhere(Attribute::InAlloca)) - return false; - - // FIXME: Change CC for the whole chain of musttail calls when possible. - // - // Can't change CC of the function that either has musttail calls, or is a - // musttail callee itself - for (User *U : F->users()) { - if (isa<BlockAddress>(U)) - continue; - CallInst* CI = dyn_cast<CallInst>(U); - if (!CI) - continue; - - if (CI->isMustTailCall()) - return false; - } - - for (BasicBlock &BB : *F) - if (BB.getTerminatingMustTailCall()) - return false; - - return true; -} - -/// Return true if the block containing the call site has a BlockFrequency of -/// less than ColdCCRelFreq% of the entry block. -static bool isColdCallSite(CallSite CS, BlockFrequencyInfo &CallerBFI) { - const BranchProbability ColdProb(ColdCCRelFreq, 100); - auto CallSiteBB = CS.getInstruction()->getParent(); - auto CallSiteFreq = CallerBFI.getBlockFreq(CallSiteBB); - auto CallerEntryFreq = - CallerBFI.getBlockFreq(&(CS.getCaller()->getEntryBlock())); - return CallSiteFreq < CallerEntryFreq * ColdProb; -} - -// This function checks if the input function F is cold at all call sites. It -// also looks each call site's containing function, returning false if the -// caller function contains other non cold calls. The input vector AllCallsCold -// contains a list of functions that only have call sites in cold blocks. -static bool -isValidCandidateForColdCC(Function &F, - function_ref<BlockFrequencyInfo &(Function &)> GetBFI, - const std::vector<Function *> &AllCallsCold) { - - if (F.user_empty()) - return false; - - for (User *U : F.users()) { - if (isa<BlockAddress>(U)) - continue; - - CallSite CS(cast<Instruction>(U)); - Function *CallerFunc = CS.getInstruction()->getParent()->getParent(); - BlockFrequencyInfo &CallerBFI = GetBFI(*CallerFunc); - if (!isColdCallSite(CS, CallerBFI)) - return false; - auto It = std::find(AllCallsCold.begin(), AllCallsCold.end(), CallerFunc); - if (It == AllCallsCold.end()) - return false; - } - return true; -} - -static void changeCallSitesToColdCC(Function *F) { - for (User *U : F->users()) { - if (isa<BlockAddress>(U)) - continue; - CallSite CS(cast<Instruction>(U)); - CS.setCallingConv(CallingConv::Cold); - } -} - -// This function iterates over all the call instructions in the input Function -// and checks that all call sites are in cold blocks and are allowed to use the -// coldcc calling convention. -static bool -hasOnlyColdCalls(Function &F, - function_ref<BlockFrequencyInfo &(Function &)> GetBFI) { - for (BasicBlock &BB : F) { - for (Instruction &I : BB) { - if (CallInst *CI = dyn_cast<CallInst>(&I)) { - CallSite CS(cast<Instruction>(CI)); - // Skip over isline asm instructions since they aren't function calls. - if (CI->isInlineAsm()) - continue; - Function *CalledFn = CI->getCalledFunction(); - if (!CalledFn) - return false; - if (!CalledFn->hasLocalLinkage()) - return false; - // Skip over instrinsics since they won't remain as function calls. - if (CalledFn->getIntrinsicID() != Intrinsic::not_intrinsic) - continue; - // Check if it's valid to use coldcc calling convention. - if (!hasChangeableCC(CalledFn) || CalledFn->isVarArg() || - CalledFn->hasAddressTaken()) - return false; - BlockFrequencyInfo &CallerBFI = GetBFI(F); - if (!isColdCallSite(CS, CallerBFI)) - return false; - } - } - } - return true; -} - -static bool -OptimizeFunctions(Module &M, TargetLibraryInfo *TLI, - function_ref<TargetTransformInfo &(Function &)> GetTTI, - function_ref<BlockFrequencyInfo &(Function &)> GetBFI, - function_ref<DominatorTree &(Function &)> LookupDomTree, - SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats) { - - bool Changed = false; - - std::vector<Function *> AllCallsCold; - for (Module::iterator FI = M.begin(), E = M.end(); FI != E;) { - Function *F = &*FI++; - if (hasOnlyColdCalls(*F, GetBFI)) - AllCallsCold.push_back(F); - } - - // Optimize functions. - for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) { - Function *F = &*FI++; - - // Don't perform global opt pass on naked functions; we don't want fast - // calling conventions for naked functions. - if (F->hasFnAttribute(Attribute::Naked)) - continue; - - // Functions without names cannot be referenced outside this module. - if (!F->hasName() && !F->isDeclaration() && !F->hasLocalLinkage()) - F->setLinkage(GlobalValue::InternalLinkage); - - if (deleteIfDead(*F, NotDiscardableComdats)) { - Changed = true; - continue; - } - - // LLVM's definition of dominance allows instructions that are cyclic - // in unreachable blocks, e.g.: - // %pat = select i1 %condition, @global, i16* %pat - // because any instruction dominates an instruction in a block that's - // not reachable from entry. - // So, remove unreachable blocks from the function, because a) there's - // no point in analyzing them and b) GlobalOpt should otherwise grow - // some more complicated logic to break these cycles. - // Removing unreachable blocks might invalidate the dominator so we - // recalculate it. - if (!F->isDeclaration()) { - if (removeUnreachableBlocks(*F)) { - auto &DT = LookupDomTree(*F); - DT.recalculate(*F); - Changed = true; - } - } - - Changed |= processGlobal(*F, TLI, LookupDomTree); - - if (!F->hasLocalLinkage()) - continue; - - if (hasChangeableCC(F) && !F->isVarArg() && !F->hasAddressTaken()) { - NumInternalFunc++; - TargetTransformInfo &TTI = GetTTI(*F); - // Change the calling convention to coldcc if either stress testing is - // enabled or the target would like to use coldcc on functions which are - // cold at all call sites and the callers contain no other non coldcc - // calls. - if (EnableColdCCStressTest || - (isValidCandidateForColdCC(*F, GetBFI, AllCallsCold) && - TTI.useColdCCForColdCall(*F))) { - F->setCallingConv(CallingConv::Cold); - changeCallSitesToColdCC(F); - Changed = true; - NumColdCC++; - } - } - - if (hasChangeableCC(F) && !F->isVarArg() && - !F->hasAddressTaken()) { - // If this function has a calling convention worth changing, is not a - // varargs function, and is only called directly, promote it to use the - // Fast calling convention. - F->setCallingConv(CallingConv::Fast); - ChangeCalleesToFastCall(F); - ++NumFastCallFns; - Changed = true; - } - - if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) && - !F->hasAddressTaken()) { - // The function is not used by a trampoline intrinsic, so it is safe - // to remove the 'nest' attribute. - RemoveNestAttribute(F); - ++NumNestRemoved; - Changed = true; - } - } - return Changed; -} - -static bool -OptimizeGlobalVars(Module &M, TargetLibraryInfo *TLI, - function_ref<DominatorTree &(Function &)> LookupDomTree, - SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats) { - bool Changed = false; - - for (Module::global_iterator GVI = M.global_begin(), E = M.global_end(); - GVI != E; ) { - GlobalVariable *GV = &*GVI++; - // Global variables without names cannot be referenced outside this module. - if (!GV->hasName() && !GV->isDeclaration() && !GV->hasLocalLinkage()) - GV->setLinkage(GlobalValue::InternalLinkage); - // Simplify the initializer. - if (GV->hasInitializer()) - if (auto *C = dyn_cast<Constant>(GV->getInitializer())) { - auto &DL = M.getDataLayout(); - Constant *New = ConstantFoldConstant(C, DL, TLI); - if (New && New != C) - GV->setInitializer(New); - } - - if (deleteIfDead(*GV, NotDiscardableComdats)) { - Changed = true; - continue; - } - - Changed |= processGlobal(*GV, TLI, LookupDomTree); - } - return Changed; -} - -/// Evaluate a piece of a constantexpr store into a global initializer. This -/// returns 'Init' modified to reflect 'Val' stored into it. At this point, the -/// GEP operands of Addr [0, OpNo) have been stepped into. -static Constant *EvaluateStoreInto(Constant *Init, Constant *Val, - ConstantExpr *Addr, unsigned OpNo) { - // Base case of the recursion. - if (OpNo == Addr->getNumOperands()) { - assert(Val->getType() == Init->getType() && "Type mismatch!"); - return Val; - } - - SmallVector<Constant*, 32> Elts; - if (StructType *STy = dyn_cast<StructType>(Init->getType())) { - // Break up the constant into its elements. - for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) - Elts.push_back(Init->getAggregateElement(i)); - - // Replace the element that we are supposed to. - ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo)); - unsigned Idx = CU->getZExtValue(); - assert(Idx < STy->getNumElements() && "Struct index out of range!"); - Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1); - - // Return the modified struct. - return ConstantStruct::get(STy, Elts); - } - - ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo)); - SequentialType *InitTy = cast<SequentialType>(Init->getType()); - uint64_t NumElts = InitTy->getNumElements(); - - // Break up the array into elements. - for (uint64_t i = 0, e = NumElts; i != e; ++i) - Elts.push_back(Init->getAggregateElement(i)); - - assert(CI->getZExtValue() < NumElts); - Elts[CI->getZExtValue()] = - EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1); - - if (Init->getType()->isArrayTy()) - return ConstantArray::get(cast<ArrayType>(InitTy), Elts); - return ConstantVector::get(Elts); -} - -/// We have decided that Addr (which satisfies the predicate -/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen. -static void CommitValueTo(Constant *Val, Constant *Addr) { - if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) { - assert(GV->hasInitializer()); - GV->setInitializer(Val); - return; - } - - ConstantExpr *CE = cast<ConstantExpr>(Addr); - GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0)); - GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2)); -} - -/// Given a map of address -> value, where addresses are expected to be some form -/// of either a global or a constant GEP, set the initializer for the address to -/// be the value. This performs mostly the same function as CommitValueTo() -/// and EvaluateStoreInto() but is optimized to be more efficient for the common -/// case where the set of addresses are GEPs sharing the same underlying global, -/// processing the GEPs in batches rather than individually. -/// -/// To give an example, consider the following C++ code adapted from the clang -/// regression tests: -/// struct S { -/// int n = 10; -/// int m = 2 * n; -/// S(int a) : n(a) {} -/// }; -/// -/// template<typename T> -/// struct U { -/// T *r = &q; -/// T q = 42; -/// U *p = this; -/// }; -/// -/// U<S> e; -/// -/// The global static constructor for 'e' will need to initialize 'r' and 'p' of -/// the outer struct, while also initializing the inner 'q' structs 'n' and 'm' -/// members. This batch algorithm will simply use general CommitValueTo() method -/// to handle the complex nested S struct initialization of 'q', before -/// processing the outermost members in a single batch. Using CommitValueTo() to -/// handle member in the outer struct is inefficient when the struct/array is -/// very large as we end up creating and destroy constant arrays for each -/// initialization. -/// For the above case, we expect the following IR to be generated: -/// -/// %struct.U = type { %struct.S*, %struct.S, %struct.U* } -/// %struct.S = type { i32, i32 } -/// @e = global %struct.U { %struct.S* gep inbounds (%struct.U, %struct.U* @e, -/// i64 0, i32 1), -/// %struct.S { i32 42, i32 84 }, %struct.U* @e } -/// The %struct.S { i32 42, i32 84 } inner initializer is treated as a complex -/// constant expression, while the other two elements of @e are "simple". -static void BatchCommitValueTo(const DenseMap<Constant*, Constant*> &Mem) { - SmallVector<std::pair<GlobalVariable*, Constant*>, 32> GVs; - SmallVector<std::pair<ConstantExpr*, Constant*>, 32> ComplexCEs; - SmallVector<std::pair<ConstantExpr*, Constant*>, 32> SimpleCEs; - SimpleCEs.reserve(Mem.size()); - - for (const auto &I : Mem) { - if (auto *GV = dyn_cast<GlobalVariable>(I.first)) { - GVs.push_back(std::make_pair(GV, I.second)); - } else { - ConstantExpr *GEP = cast<ConstantExpr>(I.first); - // We don't handle the deeply recursive case using the batch method. - if (GEP->getNumOperands() > 3) - ComplexCEs.push_back(std::make_pair(GEP, I.second)); - else - SimpleCEs.push_back(std::make_pair(GEP, I.second)); - } - } - - // The algorithm below doesn't handle cases like nested structs, so use the - // slower fully general method if we have to. - for (auto ComplexCE : ComplexCEs) - CommitValueTo(ComplexCE.second, ComplexCE.first); - - for (auto GVPair : GVs) { - assert(GVPair.first->hasInitializer()); - GVPair.first->setInitializer(GVPair.second); - } - - if (SimpleCEs.empty()) - return; - - // We cache a single global's initializer elements in the case where the - // subsequent address/val pair uses the same one. This avoids throwing away and - // rebuilding the constant struct/vector/array just because one element is - // modified at a time. - SmallVector<Constant *, 32> Elts; - Elts.reserve(SimpleCEs.size()); - GlobalVariable *CurrentGV = nullptr; - - auto commitAndSetupCache = [&](GlobalVariable *GV, bool Update) { - Constant *Init = GV->getInitializer(); - Type *Ty = Init->getType(); - if (Update) { - if (CurrentGV) { - assert(CurrentGV && "Expected a GV to commit to!"); - Type *CurrentInitTy = CurrentGV->getInitializer()->getType(); - // We have a valid cache that needs to be committed. - if (StructType *STy = dyn_cast<StructType>(CurrentInitTy)) - CurrentGV->setInitializer(ConstantStruct::get(STy, Elts)); - else if (ArrayType *ArrTy = dyn_cast<ArrayType>(CurrentInitTy)) - CurrentGV->setInitializer(ConstantArray::get(ArrTy, Elts)); - else - CurrentGV->setInitializer(ConstantVector::get(Elts)); - } - if (CurrentGV == GV) - return; - // Need to clear and set up cache for new initializer. - CurrentGV = GV; - Elts.clear(); - unsigned NumElts; - if (auto *STy = dyn_cast<StructType>(Ty)) - NumElts = STy->getNumElements(); - else - NumElts = cast<SequentialType>(Ty)->getNumElements(); - for (unsigned i = 0, e = NumElts; i != e; ++i) - Elts.push_back(Init->getAggregateElement(i)); - } - }; - - for (auto CEPair : SimpleCEs) { - ConstantExpr *GEP = CEPair.first; - Constant *Val = CEPair.second; - - GlobalVariable *GV = cast<GlobalVariable>(GEP->getOperand(0)); - commitAndSetupCache(GV, GV != CurrentGV); - ConstantInt *CI = cast<ConstantInt>(GEP->getOperand(2)); - Elts[CI->getZExtValue()] = Val; - } - // The last initializer in the list needs to be committed, others - // will be committed on a new initializer being processed. - commitAndSetupCache(CurrentGV, true); -} - -/// Evaluate static constructors in the function, if we can. Return true if we -/// can, false otherwise. -static bool EvaluateStaticConstructor(Function *F, const DataLayout &DL, - TargetLibraryInfo *TLI) { - // Call the function. - Evaluator Eval(DL, TLI); - Constant *RetValDummy; - bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy, - SmallVector<Constant*, 0>()); - - if (EvalSuccess) { - ++NumCtorsEvaluated; - - // We succeeded at evaluation: commit the result. - LLVM_DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '" - << F->getName() << "' to " - << Eval.getMutatedMemory().size() << " stores.\n"); - BatchCommitValueTo(Eval.getMutatedMemory()); - for (GlobalVariable *GV : Eval.getInvariants()) - GV->setConstant(true); - } - - return EvalSuccess; -} - -static int compareNames(Constant *const *A, Constant *const *B) { - Value *AStripped = (*A)->stripPointerCastsNoFollowAliases(); - Value *BStripped = (*B)->stripPointerCastsNoFollowAliases(); - return AStripped->getName().compare(BStripped->getName()); -} - -static void setUsedInitializer(GlobalVariable &V, - const SmallPtrSetImpl<GlobalValue *> &Init) { - if (Init.empty()) { - V.eraseFromParent(); - return; - } - - // Type of pointer to the array of pointers. - PointerType *Int8PtrTy = Type::getInt8PtrTy(V.getContext(), 0); - - SmallVector<Constant *, 8> UsedArray; - for (GlobalValue *GV : Init) { - Constant *Cast - = ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, Int8PtrTy); - UsedArray.push_back(Cast); - } - // Sort to get deterministic order. - array_pod_sort(UsedArray.begin(), UsedArray.end(), compareNames); - ArrayType *ATy = ArrayType::get(Int8PtrTy, UsedArray.size()); - - Module *M = V.getParent(); - V.removeFromParent(); - GlobalVariable *NV = - new GlobalVariable(*M, ATy, false, GlobalValue::AppendingLinkage, - ConstantArray::get(ATy, UsedArray), ""); - NV->takeName(&V); - NV->setSection("llvm.metadata"); - delete &V; -} - -namespace { - -/// An easy to access representation of llvm.used and llvm.compiler.used. -class LLVMUsed { - SmallPtrSet<GlobalValue *, 8> Used; - SmallPtrSet<GlobalValue *, 8> CompilerUsed; - GlobalVariable *UsedV; - GlobalVariable *CompilerUsedV; - -public: - LLVMUsed(Module &M) { - UsedV = collectUsedGlobalVariables(M, Used, false); - CompilerUsedV = collectUsedGlobalVariables(M, CompilerUsed, true); - } - - using iterator = SmallPtrSet<GlobalValue *, 8>::iterator; - using used_iterator_range = iterator_range<iterator>; - - iterator usedBegin() { return Used.begin(); } - iterator usedEnd() { return Used.end(); } - - used_iterator_range used() { - return used_iterator_range(usedBegin(), usedEnd()); - } - - iterator compilerUsedBegin() { return CompilerUsed.begin(); } - iterator compilerUsedEnd() { return CompilerUsed.end(); } - - used_iterator_range compilerUsed() { - return used_iterator_range(compilerUsedBegin(), compilerUsedEnd()); - } - - bool usedCount(GlobalValue *GV) const { return Used.count(GV); } - - bool compilerUsedCount(GlobalValue *GV) const { - return CompilerUsed.count(GV); - } - - bool usedErase(GlobalValue *GV) { return Used.erase(GV); } - bool compilerUsedErase(GlobalValue *GV) { return CompilerUsed.erase(GV); } - bool usedInsert(GlobalValue *GV) { return Used.insert(GV).second; } - - bool compilerUsedInsert(GlobalValue *GV) { - return CompilerUsed.insert(GV).second; - } - - void syncVariablesAndSets() { - if (UsedV) - setUsedInitializer(*UsedV, Used); - if (CompilerUsedV) - setUsedInitializer(*CompilerUsedV, CompilerUsed); - } -}; - -} // end anonymous namespace - -static bool hasUseOtherThanLLVMUsed(GlobalAlias &GA, const LLVMUsed &U) { - if (GA.use_empty()) // No use at all. - return false; - - assert((!U.usedCount(&GA) || !U.compilerUsedCount(&GA)) && - "We should have removed the duplicated " - "element from llvm.compiler.used"); - if (!GA.hasOneUse()) - // Strictly more than one use. So at least one is not in llvm.used and - // llvm.compiler.used. - return true; - - // Exactly one use. Check if it is in llvm.used or llvm.compiler.used. - return !U.usedCount(&GA) && !U.compilerUsedCount(&GA); -} - -static bool hasMoreThanOneUseOtherThanLLVMUsed(GlobalValue &V, - const LLVMUsed &U) { - unsigned N = 2; - assert((!U.usedCount(&V) || !U.compilerUsedCount(&V)) && - "We should have removed the duplicated " - "element from llvm.compiler.used"); - if (U.usedCount(&V) || U.compilerUsedCount(&V)) - ++N; - return V.hasNUsesOrMore(N); -} - -static bool mayHaveOtherReferences(GlobalAlias &GA, const LLVMUsed &U) { - if (!GA.hasLocalLinkage()) - return true; - - return U.usedCount(&GA) || U.compilerUsedCount(&GA); -} - -static bool hasUsesToReplace(GlobalAlias &GA, const LLVMUsed &U, - bool &RenameTarget) { - RenameTarget = false; - bool Ret = false; - if (hasUseOtherThanLLVMUsed(GA, U)) - Ret = true; - - // If the alias is externally visible, we may still be able to simplify it. - if (!mayHaveOtherReferences(GA, U)) - return Ret; - - // 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(...) - Constant *Aliasee = GA.getAliasee(); - GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts()); - if (!Target->hasLocalLinkage()) - return Ret; - - // 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 (hasMoreThanOneUseOtherThanLLVMUsed(*Target, U)) - return Ret; - - RenameTarget = true; - return true; -} - -static bool -OptimizeGlobalAliases(Module &M, - SmallPtrSetImpl<const Comdat *> &NotDiscardableComdats) { - bool Changed = false; - LLVMUsed Used(M); - - for (GlobalValue *GV : Used.used()) - Used.compilerUsedErase(GV); - - for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end(); - I != E;) { - GlobalAlias *J = &*I++; - - // Aliases without names cannot be referenced outside this module. - if (!J->hasName() && !J->isDeclaration() && !J->hasLocalLinkage()) - J->setLinkage(GlobalValue::InternalLinkage); - - if (deleteIfDead(*J, NotDiscardableComdats)) { - Changed = true; - continue; - } - - // If the alias can change at link time, nothing can be done - bail out. - if (J->isInterposable()) - continue; - - Constant *Aliasee = J->getAliasee(); - GlobalValue *Target = dyn_cast<GlobalValue>(Aliasee->stripPointerCasts()); - // We can't trivially replace the alias with the aliasee if the aliasee is - // non-trivial in some way. - // TODO: Try to handle non-zero GEPs of local aliasees. - if (!Target) - continue; - Target->removeDeadConstantUsers(); - - // Make all users of the alias use the aliasee instead. - bool RenameTarget; - if (!hasUsesToReplace(*J, Used, RenameTarget)) - continue; - - J->replaceAllUsesWith(ConstantExpr::getBitCast(Aliasee, J->getType())); - ++NumAliasesResolved; - Changed = true; - - if (RenameTarget) { - // Give the aliasee the name, linkage and other attributes of the alias. - Target->takeName(&*J); - Target->setLinkage(J->getLinkage()); - Target->setDSOLocal(J->isDSOLocal()); - Target->setVisibility(J->getVisibility()); - Target->setDLLStorageClass(J->getDLLStorageClass()); - - if (Used.usedErase(&*J)) - Used.usedInsert(Target); - - if (Used.compilerUsedErase(&*J)) - Used.compilerUsedInsert(Target); - } else if (mayHaveOtherReferences(*J, Used)) - continue; - - // Delete the alias. - M.getAliasList().erase(J); - ++NumAliasesRemoved; - Changed = true; - } - - Used.syncVariablesAndSets(); - - return Changed; -} - -static Function *FindCXAAtExit(Module &M, TargetLibraryInfo *TLI) { - LibFunc F = LibFunc_cxa_atexit; - if (!TLI->has(F)) - return nullptr; - - Function *Fn = M.getFunction(TLI->getName(F)); - if (!Fn) - return nullptr; - - // Make sure that the function has the correct prototype. - if (!TLI->getLibFunc(*Fn, F) || F != LibFunc_cxa_atexit) - return nullptr; - - return Fn; -} - -/// Returns whether the given function is an empty C++ destructor and can -/// therefore be eliminated. -/// Note that we assume that other optimization passes have already simplified -/// the code so we only look for a function with a single basic block, where -/// the only allowed instructions are 'ret', 'call' to an empty C++ dtor and -/// other side-effect free instructions. -static bool cxxDtorIsEmpty(const Function &Fn, - SmallPtrSet<const Function *, 8> &CalledFunctions) { - // FIXME: We could eliminate C++ destructors if they're readonly/readnone and - // nounwind, but that doesn't seem worth doing. - if (Fn.isDeclaration()) - return false; - - if (++Fn.begin() != Fn.end()) - return false; - - const BasicBlock &EntryBlock = Fn.getEntryBlock(); - for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end(); - I != E; ++I) { - if (const CallInst *CI = dyn_cast<CallInst>(I)) { - // Ignore debug intrinsics. - if (isa<DbgInfoIntrinsic>(CI)) - continue; - - const Function *CalledFn = CI->getCalledFunction(); - - if (!CalledFn) - return false; - - SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions); - - // Don't treat recursive functions as empty. - if (!NewCalledFunctions.insert(CalledFn).second) - return false; - - if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions)) - return false; - } else if (isa<ReturnInst>(*I)) - return true; // We're done. - else if (I->mayHaveSideEffects()) - return false; // Destructor with side effects, bail. - } - - return false; -} - -static bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) { - /// Itanium C++ ABI p3.3.5: - /// - /// After constructing a global (or local static) object, that will require - /// destruction on exit, a termination function is registered as follows: - /// - /// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d ); - /// - /// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the - /// call f(p) when DSO d is unloaded, before all such termination calls - /// registered before this one. It returns zero if registration is - /// successful, nonzero on failure. - - // This pass will look for calls to __cxa_atexit where the function is trivial - // and remove them. - bool Changed = false; - - for (auto I = CXAAtExitFn->user_begin(), E = CXAAtExitFn->user_end(); - I != E;) { - // We're only interested in calls. Theoretically, we could handle invoke - // instructions as well, but neither llvm-gcc nor clang generate invokes - // to __cxa_atexit. - CallInst *CI = dyn_cast<CallInst>(*I++); - if (!CI) - continue; - - Function *DtorFn = - dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts()); - if (!DtorFn) - continue; - - SmallPtrSet<const Function *, 8> CalledFunctions; - if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions)) - continue; - - // Just remove the call. - CI->replaceAllUsesWith(Constant::getNullValue(CI->getType())); - CI->eraseFromParent(); - - ++NumCXXDtorsRemoved; - - Changed |= true; - } - - return Changed; -} - -static bool optimizeGlobalsInModule( - Module &M, const DataLayout &DL, TargetLibraryInfo *TLI, - function_ref<TargetTransformInfo &(Function &)> GetTTI, - function_ref<BlockFrequencyInfo &(Function &)> GetBFI, - function_ref<DominatorTree &(Function &)> LookupDomTree) { - SmallPtrSet<const Comdat *, 8> NotDiscardableComdats; - bool Changed = false; - bool LocalChange = true; - while (LocalChange) { - LocalChange = false; - - NotDiscardableComdats.clear(); - for (const GlobalVariable &GV : M.globals()) - if (const Comdat *C = GV.getComdat()) - if (!GV.isDiscardableIfUnused() || !GV.use_empty()) - NotDiscardableComdats.insert(C); - for (Function &F : M) - if (const Comdat *C = F.getComdat()) - if (!F.isDefTriviallyDead()) - NotDiscardableComdats.insert(C); - for (GlobalAlias &GA : M.aliases()) - if (const Comdat *C = GA.getComdat()) - if (!GA.isDiscardableIfUnused() || !GA.use_empty()) - NotDiscardableComdats.insert(C); - - // Delete functions that are trivially dead, ccc -> fastcc - LocalChange |= OptimizeFunctions(M, TLI, GetTTI, GetBFI, LookupDomTree, - NotDiscardableComdats); - - // Optimize global_ctors list. - LocalChange |= optimizeGlobalCtorsList(M, [&](Function *F) { - return EvaluateStaticConstructor(F, DL, TLI); - }); - - // Optimize non-address-taken globals. - LocalChange |= OptimizeGlobalVars(M, TLI, LookupDomTree, - NotDiscardableComdats); - - // Resolve aliases, when possible. - LocalChange |= OptimizeGlobalAliases(M, NotDiscardableComdats); - - // Try to remove trivial global destructors if they are not removed - // already. - Function *CXAAtExitFn = FindCXAAtExit(M, TLI); - if (CXAAtExitFn) - LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn); - - Changed |= LocalChange; - } - - // TODO: Move all global ctors functions to the end of the module for code - // layout. - - return Changed; -} - -PreservedAnalyses GlobalOptPass::run(Module &M, ModuleAnalysisManager &AM) { - auto &DL = M.getDataLayout(); - auto &TLI = AM.getResult<TargetLibraryAnalysis>(M); - auto &FAM = - AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager(); - auto LookupDomTree = [&FAM](Function &F) -> DominatorTree &{ - return FAM.getResult<DominatorTreeAnalysis>(F); - }; - auto GetTTI = [&FAM](Function &F) -> TargetTransformInfo & { - return FAM.getResult<TargetIRAnalysis>(F); - }; - - auto GetBFI = [&FAM](Function &F) -> BlockFrequencyInfo & { - return FAM.getResult<BlockFrequencyAnalysis>(F); - }; - - if (!optimizeGlobalsInModule(M, DL, &TLI, GetTTI, GetBFI, LookupDomTree)) - return PreservedAnalyses::all(); - return PreservedAnalyses::none(); -} - -namespace { - -struct GlobalOptLegacyPass : public ModulePass { - static char ID; // Pass identification, replacement for typeid - - GlobalOptLegacyPass() : ModulePass(ID) { - initializeGlobalOptLegacyPassPass(*PassRegistry::getPassRegistry()); - } - - bool runOnModule(Module &M) override { - if (skipModule(M)) - return false; - - auto &DL = M.getDataLayout(); - auto *TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); - auto LookupDomTree = [this](Function &F) -> DominatorTree & { - return this->getAnalysis<DominatorTreeWrapperPass>(F).getDomTree(); - }; - auto GetTTI = [this](Function &F) -> TargetTransformInfo & { - return this->getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F); - }; - - auto GetBFI = [this](Function &F) -> BlockFrequencyInfo & { - return this->getAnalysis<BlockFrequencyInfoWrapperPass>(F).getBFI(); - }; - - return optimizeGlobalsInModule(M, DL, TLI, GetTTI, GetBFI, LookupDomTree); - } - - void getAnalysisUsage(AnalysisUsage &AU) const override { - AU.addRequired<TargetLibraryInfoWrapperPass>(); - AU.addRequired<TargetTransformInfoWrapperPass>(); - AU.addRequired<DominatorTreeWrapperPass>(); - AU.addRequired<BlockFrequencyInfoWrapperPass>(); - } -}; - -} // end anonymous namespace - -char GlobalOptLegacyPass::ID = 0; - -INITIALIZE_PASS_BEGIN(GlobalOptLegacyPass, "globalopt", - "Global Variable Optimizer", false, false) -INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) -INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) -INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass) -INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) -INITIALIZE_PASS_END(GlobalOptLegacyPass, "globalopt", - "Global Variable Optimizer", false, false) - -ModulePass *llvm::createGlobalOptimizerPass() { - return new GlobalOptLegacyPass(); -} |