CbC/CbC_llvm: lib/Transforms/IPO/GlobalOpt.cpp comparison

comparison lib/Transforms/IPO/GlobalOpt.cpp @ 0:95c75e76d11b LLVM3.4

LLVM 3.4

author	Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date	Thu, 12 Dec 2013 13:56:28 +0900
parents
children	e4204d083e25

comparison

equal deleted inserted replaced

--1:000000000000
+:95c75e76d11b
+//===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass transforms simple global variables that never have their address
+// taken.  If obviously true, it marks read/write globals as constant, deletes
+// variables only stored to, etc.
+//
+//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "globalopt"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
+#include "llvm/IR/CallingConv.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CallSite.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/GetElementPtrTypeIterator.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetLibraryInfo.h"
+#include "llvm/Transforms/Utils/GlobalStatus.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+#include <algorithm>
+using namespace llvm;
+STATISTIC(NumMarked    , "Number of globals marked constant");
+STATISTIC(NumUnnamed   , "Number of globals marked unnamed_addr");
+STATISTIC(NumSRA       , "Number of aggregate globals broken into scalars");
+STATISTIC(NumHeapSRA   , "Number of heap objects SRA'd");
+STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
+STATISTIC(NumDeleted   , "Number of globals deleted");
+STATISTIC(NumFnDeleted , "Number of functions deleted");
+STATISTIC(NumGlobUses  , "Number of global uses devirtualized");
+STATISTIC(NumLocalized , "Number of globals localized");
+STATISTIC(NumShrunkToBool  , "Number of global vars shrunk to booleans");
+STATISTIC(NumFastCallFns   , "Number of functions converted to fastcc");
+STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
+STATISTIC(NumNestRemoved   , "Number of nest attributes removed");
+STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
+STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
+STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed");
+namespace {
+struct GlobalOpt : public ModulePass {
+virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+AU.addRequired<TargetLibraryInfo>();
+}
+static char ID; // Pass identification, replacement for typeid
+GlobalOpt() : ModulePass(ID) {
+initializeGlobalOptPass(*PassRegistry::getPassRegistry());
+}
+bool runOnModule(Module &M);
+private:
+GlobalVariable *FindGlobalCtors(Module &M);
+bool OptimizeFunctions(Module &M);
+bool OptimizeGlobalVars(Module &M);
+bool OptimizeGlobalAliases(Module &M);
+bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
+bool ProcessGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
+bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI,
+const GlobalStatus &GS);
+bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn);
+DataLayout *TD;
+TargetLibraryInfo *TLI;
+};
+}
+char GlobalOpt::ID = 0;
+INITIALIZE_PASS_BEGIN(GlobalOpt, "globalopt",
+"Global Variable Optimizer", false, false)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
+INITIALIZE_PASS_END(GlobalOpt, "globalopt",
+"Global Variable Optimizer", false, false)
+ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
+/// isLeakCheckerRoot - Is this global variable possibly used by a leak checker
+/// as a root?  If so, we might not really want to eliminate the stores to it.
+static bool isLeakCheckerRoot(GlobalVariable *GV) {
+// A global variable is a root if it is a pointer, or could plausibly contain
+// a pointer.  There are two challenges; one is that we could have a struct
+// the has an inner member which is a pointer.  We recurse through the type to
+// detect these (up to a point).  The other is that we may actually be a union
+// of a pointer and another type, and so our LLVM type is an integer which
+// gets converted into a pointer, or our type is an [i8 x #] with a pointer
+// potentially contained here.
+if (GV->hasPrivateLinkage())
+return false;
+SmallVector<Type *, 4> Types;
+Types.push_back(cast<PointerType>(GV->getType())->getElementType());
+unsigned Limit = 20;
+do {
+Type *Ty = Types.pop_back_val();
+switch (Ty->getTypeID()) {
+default: break;
+case Type::PointerTyID: return true;
+case Type::ArrayTyID:
+case Type::VectorTyID: {
+SequentialType *STy = cast<SequentialType>(Ty);
+Types.push_back(STy->getElementType());
+break;
+}
+case Type::StructTyID: {
+StructType *STy = cast<StructType>(Ty);
+if (STy->isOpaque()) return true;
+for (StructType::element_iterator I = STy->element_begin(),
+E = STy->element_end(); I != E; ++I) {
+Type *InnerTy = *I;
+if (isa<PointerType>(InnerTy)) return true;
+if (isa<CompositeType>(InnerTy))
+Types.push_back(InnerTy);
+}
+break;
+}
+}
+if (--Limit == 0) return true;
+} while (!Types.empty());
+return false;
+}
+/// Given a value that is stored to a global but never read, determine whether
+/// it's safe to remove the store and the chain of computation that feeds the
+/// store.
+static bool IsSafeComputationToRemove(Value *V, const TargetLibraryInfo *TLI) {
+do {
+if (isa<Constant>(V))
+return true;
+if (!V->hasOneUse())
+return false;
+if (isa<LoadInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V) ||
+isa<GlobalValue>(V))
+return false;
+if (isAllocationFn(V, TLI))
+return true;
+Instruction *I = cast<Instruction>(V);
+if (I->mayHaveSideEffects())
+return false;
+if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
+if (!GEP->hasAllConstantIndices())
+return false;
+} else if (I->getNumOperands() != 1) {
+return false;
+}
+V = I->getOperand(0);
+} while (1);
+}
+/// CleanupPointerRootUsers - This GV is a pointer root.  Loop over all users
+/// of the global and clean up any that obviously don't assign the global a
+/// value that isn't dynamically allocated.
+///
+static bool CleanupPointerRootUsers(GlobalVariable *GV,
+const TargetLibraryInfo *TLI) {
+// A brief explanation of leak checkers.  The goal is to find bugs where
+// pointers are forgotten, causing an accumulating growth in memory
+// usage over time.  The common strategy for leak checkers is to whitelist the
+// memory pointed to by globals at exit.  This is popular because it also
+// solves another problem where the main thread of a C++ program may shut down
+// before other threads that are still expecting to use those globals.  To
+// handle that case, we expect the program may create a singleton and never
+// destroy it.
+bool Changed = false;
+// If Dead[n].first is the only use of a malloc result, we can delete its
+// chain of computation and the store to the global in Dead[n].second.
+SmallVector<std::pair<Instruction *, Instruction *>, 32> Dead;
+// Constants can't be pointers to dynamically allocated memory.
+for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
+UI != E;) {
+User *U = *UI++;
+if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
+Value *V = SI->getValueOperand();
+if (isa<Constant>(V)) {
+Changed = true;
+SI->eraseFromParent();
+} else if (Instruction *I = dyn_cast<Instruction>(V)) {
+if (I->hasOneUse())
+Dead.push_back(std::make_pair(I, SI));
+}
+} else if (MemSetInst *MSI = dyn_cast<MemSetInst>(U)) {
+if (isa<Constant>(MSI->getValue())) {
+Changed = true;
+MSI->eraseFromParent();
+} else if (Instruction *I = dyn_cast<Instruction>(MSI->getValue())) {
+if (I->hasOneUse())
+Dead.push_back(std::make_pair(I, MSI));
+}
+} else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U)) {
+GlobalVariable *MemSrc = dyn_cast<GlobalVariable>(MTI->getSource());
+if (MemSrc && MemSrc->isConstant()) {
+Changed = true;
+MTI->eraseFromParent();
+} else if (Instruction *I = dyn_cast<Instruction>(MemSrc)) {
+if (I->hasOneUse())
+Dead.push_back(std::make_pair(I, MTI));
+}
+} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
+if (CE->use_empty()) {
+CE->destroyConstant();
+Changed = true;
+}
+} else if (Constant *C = dyn_cast<Constant>(U)) {
+if (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 (1);
+I->eraseFromParent();
+}
+}
+return Changed;
+}
+/// CleanupConstantGlobalUsers - We just marked GV constant.  Loop over all
+/// users of the global, cleaning up the obvious ones.  This is largely just a
+/// quick scan over the use list to clean up the easy and obvious cruft.  This
+/// returns true if it made a change.
+static bool CleanupConstantGlobalUsers(Value *V, Constant *Init,
+DataLayout *TD, TargetLibraryInfo *TLI) {
+bool Changed = false;
+SmallVector<User*, 8> WorkList(V->use_begin(), V->use_end());
+while (!WorkList.empty()) {
+User *U = WorkList.pop_back_val();
+if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
+if (Init) {
+// Replace the load with the initializer.
+LI->replaceAllUsesWith(Init);
+LI->eraseFromParent();
+Changed = true;
+}
+} else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
+// Store must be unreachable or storing Init into the global.
+SI->eraseFromParent();
+Changed = true;
+} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
+if (CE->getOpcode() == Instruction::GetElementPtr) {
+Constant *SubInit = 0;
+if (Init)
+SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
+Changed |= CleanupConstantGlobalUsers(CE, SubInit, TD, TLI);
+} else if (CE->getOpcode() == Instruction::BitCast &&
+CE->getType()->isPointerTy()) {
+// Pointer cast, delete any stores and memsets to the global.
+Changed |= CleanupConstantGlobalUsers(CE, 0, TD, TLI);
+}
+if (CE->use_empty()) {
+CE->destroyConstant();
+Changed = true;
+}
+} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
+// Do not transform "gepinst (gep constexpr (GV))" here, because forming
+// "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
+// and will invalidate our notion of what Init is.
+Constant *SubInit = 0;
+if (!isa<ConstantExpr>(GEP->getOperand(0))) {
+ConstantExpr *CE =
+dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP, TD, TLI));
+if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
+SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
+// If the initializer is an all-null value and we have an inbounds GEP,
+// we already know what the result of any load from that GEP is.
+// TODO: Handle splats.
+if (Init && isa<ConstantAggregateZero>(Init) && GEP->isInBounds())
+SubInit = Constant::getNullValue(GEP->getType()->getElementType());
+}
+Changed |= CleanupConstantGlobalUsers(GEP, SubInit, TD, TLI);
+if (GEP->use_empty()) {
+GEP->eraseFromParent();
+Changed = true;
+}
+} else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
+if (MI->getRawDest() == V) {
+MI->eraseFromParent();
+Changed = true;
+}
+} else if (Constant *C = dyn_cast<Constant>(U)) {
+// If we have a chain of dead constantexprs or other things dangling from
+// us, and if they are all dead, nuke them without remorse.
+if (isSafeToDestroyConstant(C)) {
+C->destroyConstant();
+CleanupConstantGlobalUsers(V, Init, TD, TLI);
+return true;
+}
+}
+}
+return Changed;
+}
+/// isSafeSROAElementUse - Return true if the specified instruction is a safe
+/// user of a derived expression from a global that we want to SROA.
+static bool isSafeSROAElementUse(Value *V) {
+// We might have a dead and dangling constant hanging off of here.
+if (Constant *C = dyn_cast<Constant>(V))
+return 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.
+GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
+if (GEPI == 0) return false;
+if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
+!cast<Constant>(GEPI->getOperand(1))->isNullValue())
+return false;
+for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
+I != E; ++I)
+if (!isSafeSROAElementUse(*I))
+return false;
+return true;
+}
+/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
+/// Look at it and its uses and decide whether it is safe to SROA this global.
+///
+static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
+// The user of the global must be a GEP Inst or a ConstantExpr GEP.
+if (!isa<GetElementPtrInst>(U) &&
+(!isa<ConstantExpr>(U) ||
+cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
+return false;
+// Check to see if this ConstantExpr GEP is SRA'able.  In particular, we
+// don't like < 3 operand CE's, and we don't like non-constant integer
+// indices.  This enforces that all uses are 'gep GV, 0, C, ...' for some
+// value of C.
+if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
+!cast<Constant>(U->getOperand(1))->isNullValue() ||
+!isa<ConstantInt>(U->getOperand(2)))
+return false;
+gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
+++GEPI;  // Skip over the pointer index.
+// If this is a use of an array allocation, do a bit more checking for sanity.
+if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
+uint64_t NumElements = AT->getNumElements();
+ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
+// Check to make sure that index falls within the array.  If not,
+// something funny is going on, so we won't do the optimization.
+//
+if (Idx->getZExtValue() >= NumElements)
+return false;
+// We cannot scalar repl this level of the array unless any array
+// sub-indices are in-range constants.  In particular, consider:
+// A[0][i].  We cannot know that the user isn't doing invalid things like
+// allowing i to index an out-of-range subscript that accesses A[1].
+//
+// Scalar replacing *just* the outer index of the array is probably not
+// going to be a win anyway, so just give up.
+for (++GEPI; // Skip array index.
+GEPI != E;
+++GEPI) {
+uint64_t NumElements;
+if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
+NumElements = SubArrayTy->getNumElements();
+else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI))
+NumElements = SubVectorTy->getNumElements();
+else {
+assert((*GEPI)->isStructTy() &&
+"Indexed GEP type is not array, vector, or struct!");
+continue;
+}
+ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
+if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
+return false;
+}
+}
+for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
+if (!isSafeSROAElementUse(*I))
+return false;
+return true;
+}
+/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
+/// is safe for us to perform this transformation.
+///
+static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
+for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
+UI != E; ++UI) {
+if (!IsUserOfGlobalSafeForSRA(*UI, GV))
+return false;
+}
+return true;
+}
+/// SRAGlobal - Perform scalar replacement of aggregates on the specified global
+/// variable.  This opens the door for other optimizations by exposing the
+/// behavior of the program in a more fine-grained way.  We have determined that
+/// this transformation is safe already.  We return the first global variable we
+/// insert so that the caller can reprocess it.
+static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &TD) {
+// Make sure this global only has simple uses that we can SRA.
+if (!GlobalUsersSafeToSRA(GV))
+return 0;
+assert(GV->hasLocalLinkage() && !GV->isConstant());
+Constant *Init = GV->getInitializer();
+Type *Ty = Init->getType();
+std::vector<GlobalVariable*> NewGlobals;
+Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
+// Get the alignment of the global, either explicit or target-specific.
+unsigned StartAlignment = GV->getAlignment();
+if (StartAlignment == 0)
+StartAlignment = TD.getABITypeAlignment(GV->getType());
+if (StructType *STy = dyn_cast<StructType>(Ty)) {
+NewGlobals.reserve(STy->getNumElements());
+const StructLayout &Layout = *TD.getStructLayout(STy);
+for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+Constant *In = Init->getAggregateElement(i);
+assert(In && "Couldn't get element of initializer?");
+GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
+GlobalVariable::InternalLinkage,
+In, GV->getName()+"."+Twine(i),
+GV->getThreadLocalMode(),
+GV->getType()->getAddressSpace());
+Globals.insert(GV, NGV);
+NewGlobals.push_back(NGV);
+// Calculate the known alignment of the field.  If the original aggregate
+// had 256 byte alignment for example, something might depend on that:
+// propagate info to each field.
+uint64_t FieldOffset = Layout.getElementOffset(i);
+unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
+if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
+NGV->setAlignment(NewAlign);
+}
+} else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
+unsigned NumElements = 0;
+if (ArrayType *ATy = dyn_cast<ArrayType>(STy))
+NumElements = ATy->getNumElements();
+else
+NumElements = cast<VectorType>(STy)->getNumElements();
+if (NumElements > 16 && GV->hasNUsesOrMore(16))
+return 0; // It's not worth it.
+NewGlobals.reserve(NumElements);
+uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
+unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
+for (unsigned i = 0, e = NumElements; i != e; ++i) {
+Constant *In = Init->getAggregateElement(i);
+assert(In && "Couldn't get element of initializer?");
+GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
+GlobalVariable::InternalLinkage,
+In, GV->getName()+"."+Twine(i),
+GV->getThreadLocalMode(),
+GV->getType()->getAddressSpace());
+Globals.insert(GV, NGV);
+NewGlobals.push_back(NGV);
+// Calculate the known alignment of the field.  If the original aggregate
+// had 256 byte alignment for example, something might depend on that:
+// propagate info to each field.
+unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
+if (NewAlign > EltAlign)
+NGV->setAlignment(NewAlign);
+}
+}
+if (NewGlobals.empty())
+return 0;
+DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV);
+Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext()));
+// Loop over all of the uses of the global, replacing the constantexpr geps,
+// with smaller constantexpr geps or direct references.
+while (!GV->use_empty()) {
+User *GEP = GV->use_back();
+assert(((isa<ConstantExpr>(GEP) &&
+cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
+isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
+// Ignore the 1th operand, which has to be zero or else the program is quite
+// broken (undefined).  Get the 2nd operand, which is the structure or array
+// index.
+unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
+if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
+Value *NewPtr = NewGlobals[Val];
+// Form a shorter GEP if needed.
+if (GEP->getNumOperands() > 3) {
+if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
+SmallVector<Constant*, 8> Idxs;
+Idxs.push_back(NullInt);
+for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
+Idxs.push_back(CE->getOperand(i));
+NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs);
+} else {
+GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
+SmallVector<Value*, 8> Idxs;
+Idxs.push_back(NullInt);
+for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
+Idxs.push_back(GEPI->getOperand(i));
+NewPtr = GetElementPtrInst::Create(NewPtr, Idxs,
+GEPI->getName()+"."+Twine(Val),GEPI);
+}
+}
+GEP->replaceAllUsesWith(NewPtr);
+if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
+GEPI->eraseFromParent();
+else
+cast<ConstantExpr>(GEP)->destroyConstant();
+}
+// Delete the old global, now that it is dead.
+Globals.erase(GV);
+++NumSRA;
+// Loop over the new globals array deleting any globals that are obviously
+// dead.  This can arise due to scalarization of a structure or an array that
+// has elements that are dead.
+unsigned FirstGlobal = 0;
+for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
+if (NewGlobals[i]->use_empty()) {
+Globals.erase(NewGlobals[i]);
+if (FirstGlobal == i) ++FirstGlobal;
+}
+return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
+}
+/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
+/// value will trap if the value is dynamically null.  PHIs keeps track of any
+/// phi nodes we've seen to avoid reprocessing them.
+static bool AllUsesOfValueWillTrapIfNull(const Value *V,
+SmallPtrSet<const PHINode*, 8> &PHIs) {
+for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
+++UI) {
+const User *U = *UI;
+if (isa<LoadInst>(U)) {
+// Will trap.
+} else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
+if (SI->getOperand(0) == V) {
+//cerr << "NONTRAPPING USE: " << *U;
+return false;  // Storing the value.
+}
+} else if (const CallInst *CI = dyn_cast<CallInst>(U)) {
+if (CI->getCalledValue() != V) {
+//cerr << "NONTRAPPING USE: " << *U;
+return false;  // Not calling the ptr
+}
+} else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) {
+if (II->getCalledValue() != V) {
+//cerr << "NONTRAPPING USE: " << *U;
+return false;  // Not calling the ptr
+}
+} else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) {
+if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
+} else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
+if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
+} else if (const PHINode *PN = dyn_cast<PHINode>(U)) {
+// If we've already seen this phi node, ignore it, it has already been
+// checked.
+if (PHIs.insert(PN) && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
+return false;
+} else if (isa<ICmpInst>(U) &&
+isa<ConstantPointerNull>(UI->getOperand(1))) {
+// Ignore icmp X, null
+} else {
+//cerr << "NONTRAPPING USE: " << *U;
+return false;
+}
+}
+return true;
+}
+/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
+/// from GV will trap if the loaded value is null.  Note that this also permits
+/// comparisons of the loaded value against null, as a special case.
+static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) {
+for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
+UI != E; ++UI) {
+const User *U = *UI;
+if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
+SmallPtrSet<const PHINode*, 8> PHIs;
+if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
+return false;
+} else if (isa<StoreInst>(U)) {
+// Ignore stores to the global.
+} else {
+// We don't know or understand this user, bail out.
+//cerr << "UNKNOWN USER OF GLOBAL!: " << *U;
+return false;
+}
+}
+return true;
+}
+static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
+bool Changed = false;
+for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
+Instruction *I = cast<Instruction>(*UI++);
+if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
+LI->setOperand(0, NewV);
+Changed = true;
+} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
+if (SI->getOperand(1) == V) {
+SI->setOperand(1, NewV);
+Changed = true;
+}
+} else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
+CallSite CS(I);
+if (CS.getCalledValue() == V) {
+// Calling through the pointer!  Turn into a direct call, but be careful
+// that the pointer is not also being passed as an argument.
+CS.setCalledFunction(NewV);
+Changed = true;
+bool PassedAsArg = false;
+for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
+if (CS.getArgument(i) == V) {
+PassedAsArg = true;
+CS.setArgument(i, NewV);
+}
+if (PassedAsArg) {
+// Being passed as an argument also.  Be careful to not invalidate UI!
+UI = V->use_begin();
+}
+}
+} else if (CastInst *CI = dyn_cast<CastInst>(I)) {
+Changed |= OptimizeAwayTrappingUsesOfValue(CI,
+ConstantExpr::getCast(CI->getOpcode(),
+NewV, CI->getType()));
+if (CI->use_empty()) {
+Changed = true;
+CI->eraseFromParent();
+}
+} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
+// Should handle GEP here.
+SmallVector<Constant*, 8> Idxs;
+Idxs.reserve(GEPI->getNumOperands()-1);
+for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
+i != e; ++i)
+if (Constant *C = dyn_cast<Constant>(*i))
+Idxs.push_back(C);
+else
+break;
+if (Idxs.size() == GEPI->getNumOperands()-1)
+Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
+ConstantExpr::getGetElementPtr(NewV, Idxs));
+if (GEPI->use_empty()) {
+Changed = true;
+GEPI->eraseFromParent();
+}
+}
+}
+return Changed;
+}
+/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
+/// value stored into it.  If there are uses of the loaded value that would trap
+/// if the loaded value is dynamically null, then we know that they cannot be
+/// reachable with a null optimize away the load.
+static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV,
+DataLayout *TD,
+TargetLibraryInfo *TLI) {
+bool Changed = false;
+// Keep track of whether we are able to remove all the uses of the global
+// other than the store that defines it.
+bool AllNonStoreUsesGone = true;
+// Replace all uses of loads with uses of uses of the stored value.
+for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
+User *GlobalUser = *GUI++;
+if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
+Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
+// If we were able to delete all uses of the loads
+if (LI->use_empty()) {
+LI->eraseFromParent();
+Changed = true;
+} else {
+AllNonStoreUsesGone = false;
+}
+} else if (isa<StoreInst>(GlobalUser)) {
+// Ignore the store that stores "LV" to the global.
+assert(GlobalUser->getOperand(1) == GV &&
+"Must be storing *to* the global");
+} else {
+AllNonStoreUsesGone = false;
+// If we get here we could have other crazy uses that are transitively
+// loaded.
+assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
+isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser) ||
+isa<BitCastInst>(GlobalUser) ||
+isa<GetElementPtrInst>(GlobalUser)) &&
+"Only expect load and stores!");
+}
+}
+if (Changed) {
+DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
+++NumGlobUses;
+}
+// If we nuked all of the loads, then none of the stores are needed either,
+// nor is the global.
+if (AllNonStoreUsesGone) {
+if (isLeakCheckerRoot(GV)) {
+Changed |= CleanupPointerRootUsers(GV, TLI);
+} else {
+Changed = true;
+CleanupConstantGlobalUsers(GV, 0, TD, TLI);
+}
+if (GV->use_empty()) {
+DEBUG(dbgs() << "  *** GLOBAL NOW DEAD!\n");
+Changed = true;
+GV->eraseFromParent();
+++NumDeleted;
+}
+}
+return Changed;
+}
+/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
+/// instructions that are foldable.
+static void ConstantPropUsersOf(Value *V,
+DataLayout *TD, TargetLibraryInfo *TLI) {
+for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
+if (Instruction *I = dyn_cast<Instruction>(*UI++))
+if (Constant *NewC = ConstantFoldInstruction(I, TD, TLI)) {
+I->replaceAllUsesWith(NewC);
+// Advance UI to the next non-I use to avoid invalidating it!
+// Instructions could multiply use V.
+while (UI != E && *UI == I)
+++UI;
+I->eraseFromParent();
+}
+}
+/// OptimizeGlobalAddressOfMalloc - This function takes the specified global
+/// variable, and transforms the program as if it always contained the result of
+/// the specified malloc.  Because it is always the result of the specified
+/// malloc, there is no reason to actually DO the malloc.  Instead, turn the
+/// malloc into a global, and any loads of GV as uses of the new global.
+static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
+CallInst *CI,
+Type *AllocTy,
+ConstantInt *NElements,
+DataLayout *TD,
+TargetLibraryInfo *TLI) {
+DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << "  CALL = " << *CI << '\n');
+Type *GlobalType;
+if (NElements->getZExtValue() == 1)
+GlobalType = AllocTy;
+else
+// If we have an array allocation, the global variable is of an array.
+GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue());
+// Create the new global variable.  The contents of the malloc'd memory is
+// undefined, so initialize with an undef value.
+GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(),
+GlobalType, false,
+GlobalValue::InternalLinkage,
+UndefValue::get(GlobalType),
+GV->getName()+".body",
+GV,
+GV->getThreadLocalMode());
+// If there are bitcast users of the malloc (which is typical, usually we have
+// a malloc + bitcast) then replace them with uses of the new global.  Update
+// other users to use the global as well.
+BitCastInst *TheBC = 0;
+while (!CI->use_empty()) {
+Instruction *User = cast<Instruction>(CI->use_back());
+if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
+if (BCI->getType() == NewGV->getType()) {
+BCI->replaceAllUsesWith(NewGV);
+BCI->eraseFromParent();
+} else {
+BCI->setOperand(0, NewGV);
+}
+} else {
+if (TheBC == 0)
+TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI);
+User->replaceUsesOfWith(CI, TheBC);
+}
+}
+Constant *RepValue = NewGV;
+if (NewGV->getType() != GV->getType()->getElementType())
+RepValue = ConstantExpr::getBitCast(RepValue,
+GV->getType()->getElementType());
+// If there is a comparison against null, we will insert a global bool to
+// keep track of whether the global was initialized yet or not.
+GlobalVariable *InitBool =
+new GlobalVariable(Type::getInt1Ty(GV->getContext()), false,
+GlobalValue::InternalLinkage,
+ConstantInt::getFalse(GV->getContext()),
+GV->getName()+".init", GV->getThreadLocalMode());
+bool InitBoolUsed = false;
+// Loop over all uses of GV, processing them in turn.
+while (!GV->use_empty()) {
+if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) {
+// The global is initialized when the store to it occurs.
+new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, 0,
+SI->getOrdering(), SI->getSynchScope(), SI);
+SI->eraseFromParent();
+continue;
+}
+LoadInst *LI = cast<LoadInst>(GV->use_back());
+while (!LI->use_empty()) {
+Use &LoadUse = LI->use_begin().getUse();
+if (!isa<ICmpInst>(LoadUse.getUser())) {
+LoadUse = RepValue;
+continue;
+}
+ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser());
+// Replace the cmp X, 0 with a use of the bool value.
+// Sink the load to where the compare was, if atomic rules allow us to.
+Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", false, 0,
+LI->getOrdering(), LI->getSynchScope(),
+LI->isUnordered() ? (Instruction*)ICI : LI);
+InitBoolUsed = true;
+switch (ICI->getPredicate()) {
+default: llvm_unreachable("Unknown ICmp Predicate!");
+case ICmpInst::ICMP_ULT:
+case ICmpInst::ICMP_SLT:   // X < null -> always false
+LV = ConstantInt::getFalse(GV->getContext());
+break;
+case ICmpInst::ICMP_ULE:
+case ICmpInst::ICMP_SLE:
+case ICmpInst::ICMP_EQ:
+LV = BinaryOperator::CreateNot(LV, "notinit", ICI);
+break;
+case ICmpInst::ICMP_NE:
+case ICmpInst::ICMP_UGE:
+case ICmpInst::ICMP_SGE:
+case ICmpInst::ICMP_UGT:
+case ICmpInst::ICMP_SGT:
+break;  // no change.
+}
+ICI->replaceAllUsesWith(LV);
+ICI->eraseFromParent();
+}
+LI->eraseFromParent();
+}
+// If the initialization boolean was used, insert it, otherwise delete it.
+if (!InitBoolUsed) {
+while (!InitBool->use_empty())  // Delete initializations
+cast<StoreInst>(InitBool->use_back())->eraseFromParent();
+delete InitBool;
+} else
+GV->getParent()->getGlobalList().insert(GV, InitBool);
+// Now the GV is dead, nuke it and the malloc..
+GV->eraseFromParent();
+CI->eraseFromParent();
+// To further other optimizations, loop over all users of NewGV and try to
+// constant prop them.  This will promote GEP instructions with constant
+// indices into GEP constant-exprs, which will allow global-opt to hack on it.
+ConstantPropUsersOf(NewGV, TD, TLI);
+if (RepValue != NewGV)
+ConstantPropUsersOf(RepValue, TD, TLI);
+return NewGV;
+}
+/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
+/// to make sure that there are no complex uses of V.  We permit simple things
+/// like dereferencing the pointer, but not storing through the address, unless
+/// it is to the specified global.
+static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V,
+const GlobalVariable *GV,
+SmallPtrSet<const PHINode*, 8> &PHIs) {
+for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end();
+UI != E; ++UI) {
+const Instruction *Inst = cast<Instruction>(*UI);
+if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
+continue; // Fine, ignore.
+}
+if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
+return false;  // Storing the pointer itself... bad.
+continue; // Otherwise, storing through it, or storing into GV... fine.
+}
+// Must index into the array and into the struct.
+if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) {
+if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
+return false;
+continue;
+}
+if (const PHINode *PN = dyn_cast<PHINode>(Inst)) {
+// PHIs are ok if all uses are ok.  Don't infinitely recurse through PHI
+// cycles.
+if (PHIs.insert(PN))
+if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
+return false;
+continue;
+}
+if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
+if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
+return false;
+continue;
+}
+return false;
+}
+return true;
+}
+/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
+/// somewhere.  Transform all uses of the allocation into loads from the
+/// global and uses of the resultant pointer.  Further, delete the store into
+/// GV.  This assumes that these value pass the
+/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
+static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
+GlobalVariable *GV) {
+while (!Alloc->use_empty()) {
+Instruction *U = cast<Instruction>(*Alloc->use_begin());
+Instruction *InsertPt = U;
+if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
+// If this is the store of the allocation into the global, remove it.
+if (SI->getOperand(1) == GV) {
+SI->eraseFromParent();
+continue;
+}
+} else if (PHINode *PN = dyn_cast<PHINode>(U)) {
+// Insert the load in the corresponding predecessor, not right before the
+// PHI.
+InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
+} else if (isa<BitCastInst>(U)) {
+// Must be bitcast between the malloc and store to initialize the global.
+ReplaceUsesOfMallocWithGlobal(U, GV);
+U->eraseFromParent();
+continue;
+} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
+// If this is a "GEP bitcast" and the user is a store to the global, then
+// just process it as a bitcast.
+if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
+if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
+if (SI->getOperand(1) == GV) {
+// Must be bitcast GEP between the malloc and store to initialize
+// the global.
+ReplaceUsesOfMallocWithGlobal(GEPI, GV);
+GEPI->eraseFromParent();
+continue;
+}
+}
+// Insert a load from the global, and use it instead of the malloc.
+Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
+U->replaceUsesOfWith(Alloc, NL);
+}
+}
+/// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
+/// of a load) are simple enough to perform heap SRA on.  This permits GEP's
+/// that index through the array and struct field, icmps of null, and PHIs.
+static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V,
+SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs,
+SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) {
+// We permit two users of the load: setcc comparing against the null
+// pointer, and a getelementptr of a specific form.
+for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
+++UI) {
+const Instruction *User = cast<Instruction>(*UI);
+// Comparison against null is ok.
+if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
+if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
+return false;
+continue;
+}
+// getelementptr is also ok, but only a simple form.
+if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
+// Must index into the array and into the struct.
+if (GEPI->getNumOperands() < 3)
+return false;
+// Otherwise the GEP is ok.
+continue;
+}
+if (const PHINode *PN = dyn_cast<PHINode>(User)) {
+if (!LoadUsingPHIsPerLoad.insert(PN))
+// This means some phi nodes are dependent on each other.
+// Avoid infinite looping!
+return false;
+if (!LoadUsingPHIs.insert(PN))
+// If we have already analyzed this PHI, then it is safe.
+continue;
+// Make sure all uses of the PHI are simple enough to transform.
+if (!LoadUsesSimpleEnoughForHeapSRA(PN,
+LoadUsingPHIs, LoadUsingPHIsPerLoad))
+return false;
+continue;
+}
+// Otherwise we don't know what this is, not ok.
+return false;
+}
+return true;
+}
+/// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
+/// GV are simple enough to perform HeapSRA, return true.
+static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV,
+Instruction *StoredVal) {
+SmallPtrSet<const PHINode*, 32> LoadUsingPHIs;
+SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad;
+for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
+UI != E; ++UI)
+if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
+if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
+LoadUsingPHIsPerLoad))
+return false;
+LoadUsingPHIsPerLoad.clear();
+}
+// If we reach here, we know that all uses of the loads and transitive uses
+// (through PHI nodes) are simple enough to transform.  However, we don't know
+// that all inputs the to the PHI nodes are in the same equivalence sets.
+// Check to verify that all operands of the PHIs are either PHIS that can be
+// transformed, loads from GV, or MI itself.
+for (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin()
+, E = LoadUsingPHIs.end(); I != E; ++I) {
+const PHINode *PN = *I;
+for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
+Value *InVal = PN->getIncomingValue(op);
+// PHI of the stored value itself is ok.
+if (InVal == StoredVal) continue;
+if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) {
+// One of the PHIs in our set is (optimistically) ok.
+if (LoadUsingPHIs.count(InPN))
+continue;
+return false;
+}
+// Load from GV is ok.
+if (const LoadInst *LI = dyn_cast<LoadInst>(InVal))
+if (LI->getOperand(0) == GV)
+continue;
+// UNDEF? NULL?
+// Anything else is rejected.
+return false;
+}
+}
+return true;
+}
+static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
+DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
+std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
+std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
+if (FieldNo >= FieldVals.size())
+FieldVals.resize(FieldNo+1);
+// If we already have this value, just reuse the previously scalarized
+// version.
+if (Value *FieldVal = FieldVals[FieldNo])
+return FieldVal;
+// Depending on what instruction this is, we have several cases.
+Value *Result;
+if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
+// This is a scalarized version of the load from the global.  Just create
+// a new Load of the scalarized global.
+Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
+InsertedScalarizedValues,
+PHIsToRewrite),
+LI->getName()+".f"+Twine(FieldNo), LI);
+} else if (PHINode *PN = dyn_cast<PHINode>(V)) {
+// PN's type is pointer to struct.  Make a new PHI of pointer to struct
+// field.
+StructType *ST = cast<StructType>(PN->getType()->getPointerElementType());
+PHINode *NewPN =
+PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
+PN->getNumIncomingValues(),
+PN->getName()+".f"+Twine(FieldNo), PN);
+Result = NewPN;
+PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
+} else {
+llvm_unreachable("Unknown usable value");
+}
+return FieldVals[FieldNo] = Result;
+}
+/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
+/// the load, rewrite the derived value to use the HeapSRoA'd load.
+static void RewriteHeapSROALoadUser(Instruction *LoadUser,
+DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
+std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
+// If this is a comparison against null, handle it.
+if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
+assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
+// If we have a setcc of the loaded pointer, we can use a setcc of any
+// field.
+Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
+InsertedScalarizedValues, PHIsToRewrite);
+Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr,
+Constant::getNullValue(NPtr->getType()),
+SCI->getName());
+SCI->replaceAllUsesWith(New);
+SCI->eraseFromParent();
+return;
+}
+// Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
+if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
+assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
+&& "Unexpected GEPI!");
+// Load the pointer for this field.
+unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
+Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
+InsertedScalarizedValues, PHIsToRewrite);
+// Create the new GEP idx vector.
+SmallVector<Value*, 8> GEPIdx;
+GEPIdx.push_back(GEPI->getOperand(1));
+GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
+Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx,
+GEPI->getName(), GEPI);
+GEPI->replaceAllUsesWith(NGEPI);
+GEPI->eraseFromParent();
+return;
+}
+// Recursively transform the users of PHI nodes.  This will lazily create the
+// PHIs that are needed for individual elements.  Keep track of what PHIs we
+// see in InsertedScalarizedValues so that we don't get infinite loops (very
+// antisocial).  If the PHI is already in InsertedScalarizedValues, it has
+// already been seen first by another load, so its uses have already been
+// processed.
+PHINode *PN = cast<PHINode>(LoadUser);
+if (!InsertedScalarizedValues.insert(std::make_pair(PN,
+std::vector<Value*>())).second)
+return;
+// If this is the first time we've seen this PHI, recursively process all
+// users.
+for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
+Instruction *User = cast<Instruction>(*UI++);
+RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
+}
+}
+/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global.  Ptr
+/// is a value loaded from the global.  Eliminate all uses of Ptr, making them
+/// use FieldGlobals instead.  All uses of loaded values satisfy
+/// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
+static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
+DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
+std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
+for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
+UI != E; ) {
+Instruction *User = cast<Instruction>(*UI++);
+RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
+}
+if (Load->use_empty()) {
+Load->eraseFromParent();
+InsertedScalarizedValues.erase(Load);
+}
+}
+/// PerformHeapAllocSRoA - CI is an allocation of an array of structures.  Break
+/// it up into multiple allocations of arrays of the fields.
+static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI,
+Value *NElems, DataLayout *TD,
+const TargetLibraryInfo *TLI) {
+DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << "  MALLOC = " << *CI << '\n');
+Type *MAT = getMallocAllocatedType(CI, TLI);
+StructType *STy = cast<StructType>(MAT);
+// There is guaranteed to be at least one use of the malloc (storing
+// it into GV).  If there are other uses, change them to be uses of
+// the global to simplify later code.  This also deletes the store
+// into GV.
+ReplaceUsesOfMallocWithGlobal(CI, GV);
+// Okay, at this point, there are no users of the malloc.  Insert N
+// new mallocs at the same place as CI, and N globals.
+std::vector<Value*> FieldGlobals;
+std::vector<Value*> FieldMallocs;
+for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
+Type *FieldTy = STy->getElementType(FieldNo);
+PointerType *PFieldTy = PointerType::getUnqual(FieldTy);
+GlobalVariable *NGV =
+new GlobalVariable(*GV->getParent(),
+PFieldTy, false, GlobalValue::InternalLinkage,
+Constant::getNullValue(PFieldTy),
+GV->getName() + ".f" + Twine(FieldNo), GV,
+GV->getThreadLocalMode());
+FieldGlobals.push_back(NGV);
+unsigned TypeSize = TD->getTypeAllocSize(FieldTy);
+if (StructType *ST = dyn_cast<StructType>(FieldTy))
+TypeSize = TD->getStructLayout(ST)->getSizeInBytes();
+Type *IntPtrTy = TD->getIntPtrType(CI->getType());
+Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy,
+ConstantInt::get(IntPtrTy, TypeSize),
+NElems, 0,
+CI->getName() + ".f" + Twine(FieldNo));
+FieldMallocs.push_back(NMI);
+new StoreInst(NMI, NGV, CI);
+}
+// The tricky aspect of this transformation is handling the case when malloc
+// fails.  In the original code, malloc failing would set the result pointer
+// of malloc to null.  In this case, some mallocs could succeed and others
+// could fail.  As such, we emit code that looks like this:
+//    F0 = malloc(field0)
+//    F1 = malloc(field1)
+//    F2 = malloc(field2)
+//    if (F0 == 0 || F1 == 0 || F2 == 0) {
+//      if (F0) { free(F0); F0 = 0; }
+//      if (F1) { free(F1); F1 = 0; }
+//      if (F2) { free(F2); F2 = 0; }
+//    }
+// The malloc can also fail if its argument is too large.
+Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0);
+Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0),
+ConstantZero, "isneg");
+for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
+Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i],
+Constant::getNullValue(FieldMallocs[i]->getType()),
+"isnull");
+RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI);
+}
+// Split the basic block at the old malloc.
+BasicBlock *OrigBB = CI->getParent();
+BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont");
+// Create the block to check the first condition.  Put all these blocks at the
+// end of the function as they are unlikely to be executed.
+BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(),
+"malloc_ret_null",
+OrigBB->getParent());
+// Remove the uncond branch from OrigBB to ContBB, turning it into a cond
+// branch on RunningOr.
+OrigBB->getTerminator()->eraseFromParent();
+BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
+// Within the NullPtrBlock, we need to emit a comparison and branch for each
+// pointer, because some may be null while others are not.
+for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
+Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
+Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal,
+Constant::getNullValue(GVVal->getType()));
+BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it",
+OrigBB->getParent());
+BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next",
+OrigBB->getParent());
+Instruction *BI = BranchInst::Create(FreeBlock, NextBlock,
+Cmp, NullPtrBlock);
+// Fill in FreeBlock.
+CallInst::CreateFree(GVVal, BI);
+new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
+FreeBlock);
+BranchInst::Create(NextBlock, FreeBlock);
+NullPtrBlock = NextBlock;
+}
+BranchInst::Create(ContBB, NullPtrBlock);
+// CI is no longer needed, remove it.
+CI->eraseFromParent();
+/// InsertedScalarizedLoads - As we process loads, if we can't immediately
+/// update all uses of the load, keep track of what scalarized loads are
+/// inserted for a given load.
+DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
+InsertedScalarizedValues[GV] = FieldGlobals;
+std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
+// Okay, the malloc site is completely handled.  All of the uses of GV are now
+// loads, and all uses of those loads are simple.  Rewrite them to use loads
+// of the per-field globals instead.
+for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
+Instruction *User = cast<Instruction>(*UI++);
+if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
+RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
+continue;
+}
+// Must be a store of null.
+StoreInst *SI = cast<StoreInst>(User);
+assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
+"Unexpected heap-sra user!");
+// Insert a store of null into each global.
+for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
+PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
+Constant *Null = Constant::getNullValue(PT->getElementType());
+new StoreInst(Null, FieldGlobals[i], SI);
+}
+// Erase the original store.
+SI->eraseFromParent();
+}
+// While we have PHIs that are interesting to rewrite, do it.
+while (!PHIsToRewrite.empty()) {
+PHINode *PN = PHIsToRewrite.back().first;
+unsigned FieldNo = PHIsToRewrite.back().second;
+PHIsToRewrite.pop_back();
+PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
+assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
+// Add all the incoming values.  This can materialize more phis.
+for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+Value *InVal = PN->getIncomingValue(i);
+InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
+PHIsToRewrite);
+FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
+}
+}
+// Drop all inter-phi links and any loads that made it this far.
+for (DenseMap<Value*, std::vector<Value*> >::iterator
+I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
+I != E; ++I) {
+if (PHINode *PN = dyn_cast<PHINode>(I->first))
+PN->dropAllReferences();
+else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
+LI->dropAllReferences();
+}
+// Delete all the phis and loads now that inter-references are dead.
+for (DenseMap<Value*, std::vector<Value*> >::iterator
+I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
+I != E; ++I) {
+if (PHINode *PN = dyn_cast<PHINode>(I->first))
+PN->eraseFromParent();
+else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
+LI->eraseFromParent();
+}
+// The old global is now dead, remove it.
+GV->eraseFromParent();
+++NumHeapSRA;
+return cast<GlobalVariable>(FieldGlobals[0]);
+}
+/// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
+/// pointer global variable with a single value stored it that is a malloc or
+/// cast of malloc.
+static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
+CallInst *CI,
+Type *AllocTy,
+AtomicOrdering Ordering,
+Module::global_iterator &GVI,
+DataLayout *TD,
+TargetLibraryInfo *TLI) {
+if (!TD)
+return false;
+// If this is a malloc of an abstract type, don't touch it.
+if (!AllocTy->isSized())
+return false;
+// We can't optimize this global unless all uses of it are *known* to be
+// of the malloc value, not of the null initializer value (consider a use
+// that compares the global's value against zero to see if the malloc has
+// been reached).  To do this, we check to see if all uses of the global
+// would trap if the global were null: this proves that they must all
+// happen after the malloc.
+if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
+return false;
+// We can't optimize this if the malloc itself is used in a complex way,
+// for example, being stored into multiple globals.  This allows the
+// malloc to be stored into the specified global, loaded icmp'd, and
+// GEP'd.  These are all things we could transform to using the global
+// for.
+SmallPtrSet<const PHINode*, 8> PHIs;
+if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs))
+return false;
+// If we have a global that is only initialized with a fixed size malloc,
+// transform the program to use global memory instead of malloc'd memory.
+// This eliminates dynamic allocation, avoids an indirection accessing the
+// data, and exposes the resultant global to further GlobalOpt.
+// We cannot optimize the malloc if we cannot determine malloc array size.
+Value *NElems = getMallocArraySize(CI, TD, TLI, true);
+if (!NElems)
+return false;
+if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
+// Restrict this transformation to only working on small allocations
+// (2048 bytes currently), as we don't want to introduce a 16M global or
+// something.
+if (NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) {
+GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD, TLI);
+return true;
+}
+// If the allocation is an array of structures, consider transforming this
+// into multiple malloc'd arrays, one for each field.  This is basically
+// SRoA for malloc'd memory.
+if (Ordering != NotAtomic)
+return false;
+// If this is an allocation of a fixed size array of structs, analyze as a
+// variable size array.  malloc [100 x struct],1 -> malloc struct, 100
+if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1))
+if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
+AllocTy = AT->getElementType();
+StructType *AllocSTy = dyn_cast<StructType>(AllocTy);
+if (!AllocSTy)
+return false;
+// This the structure has an unreasonable number of fields, leave it
+// alone.
+if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
+AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) {
+// If this is a fixed size array, transform the Malloc to be an alloc of
+// structs.  malloc [100 x struct],1 -> malloc struct, 100
+if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI, TLI))) {
+Type *IntPtrTy = TD->getIntPtrType(CI->getType());
+unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes();
+Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize);
+Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements());
+Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy,
+AllocSize, NumElements,
+0, CI->getName());
+Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI);
+CI->replaceAllUsesWith(Cast);
+CI->eraseFromParent();
+if (BitCastInst *BCI = dyn_cast<BitCastInst>(Malloc))
+CI = cast<CallInst>(BCI->getOperand(0));
+else
+CI = cast<CallInst>(Malloc);
+}
+GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, TLI, true),
+TD, TLI);
+return true;
+}
+return false;
+}
+// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
+// that only one value (besides its initializer) is ever stored to the global.
+static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
+AtomicOrdering Ordering,
+Module::global_iterator &GVI,
+DataLayout *TD, TargetLibraryInfo *TLI) {
+// Ignore no-op GEPs and bitcasts.
+StoredOnceVal = StoredOnceVal->stripPointerCasts();
+// If we are dealing with a pointer global that is initialized to null and
+// only has one (non-null) value stored into it, then we can optimize any
+// users of the loaded value (often calls and loads) that would trap if the
+// value was null.
+if (GV->getInitializer()->getType()->isPointerTy() &&
+GV->getInitializer()->isNullValue()) {
+if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
+if (GV->getInitializer()->getType() != SOVC->getType())
+SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
+// Optimize away any trapping uses of the loaded value.
+if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, TD, TLI))
+return true;
+} else if (CallInst *CI = extractMallocCall(StoredOnceVal, TLI)) {
+Type *MallocType = getMallocAllocatedType(CI, TLI);
+if (MallocType &&
+TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, Ordering, GVI,
+TD, TLI))
+return true;
+}
+}
+return false;
+}
+/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
+/// two values ever stored into GV are its initializer and OtherVal.  See if we
+/// can shrink the global into a boolean and select between the two values
+/// whenever it is used.  This exposes the values to other scalar optimizations.
+static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
+Type *GVElType = GV->getType()->getElementType();
+// If GVElType is already i1, it is already shrunk.  If the type of the GV is
+// an FP value, pointer or vector, don't do this optimization because a select
+// between them is very expensive and unlikely to lead to later
+// simplification.  In these cases, we typically end up with "cond ? v1 : v2"
+// where v1 and v2 both require constant pool loads, a big loss.
+if (GVElType == Type::getInt1Ty(GV->getContext()) ||
+GVElType->isFloatingPointTy() ||
+GVElType->isPointerTy() || GVElType->isVectorTy())
+return false;
+// Walk the use list of the global seeing if all the uses are load or store.
+// If there is anything else, bail out.
+for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
+User *U = *I;
+if (!isa<LoadInst>(U) && !isa<StoreInst>(U))
+return false;
+}
+DEBUG(dbgs() << "   *** SHRINKING TO BOOL: " << *GV);
+// Create the new global, initializing it to false.
+GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()),
+false,
+GlobalValue::InternalLinkage,
+ConstantInt::getFalse(GV->getContext()),
+GV->getName()+".b",
+GV->getThreadLocalMode(),
+GV->getType()->getAddressSpace());
+GV->getParent()->getGlobalList().insert(GV, NewGV);
+Constant *InitVal = GV->getInitializer();
+assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
+"No reason to shrink to bool!");
+// If initialized to zero and storing one into the global, we can use a cast
+// instead of a select to synthesize the desired value.
+bool IsOneZero = false;
+if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
+IsOneZero = InitVal->isNullValue() && CI->isOne();
+while (!GV->use_empty()) {
+Instruction *UI = cast<Instruction>(GV->use_back());
+if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
+// Change the store into a boolean store.
+bool StoringOther = SI->getOperand(0) == OtherVal;
+// Only do this if we weren't storing a loaded value.
+Value *StoreVal;
+if (StoringOther || SI->getOperand(0) == InitVal) {
+StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()),
+StoringOther);
+} else {
+// Otherwise, we are storing a previously loaded copy.  To do this,
+// change the copy from copying the original value to just copying the
+// bool.
+Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
+// If we've already replaced the input, StoredVal will be a cast or
+// select instruction.  If not, it will be a load of the original
+// global.
+if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
+assert(LI->getOperand(0) == GV && "Not a copy!");
+// Insert a new load, to preserve the saved value.
+StoreVal = new LoadInst(NewGV, LI->getName()+".b", false, 0,
+LI->getOrdering(), LI->getSynchScope(), LI);
+} else {
+assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
+"This is not a form that we understand!");
+StoreVal = StoredVal->getOperand(0);
+assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
+}
+}
+new StoreInst(StoreVal, NewGV, false, 0,
+SI->getOrdering(), SI->getSynchScope(), SI);
+} else {
+// Change the load into a load of bool then a select.
+LoadInst *LI = cast<LoadInst>(UI);
+LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", false, 0,
+LI->getOrdering(), LI->getSynchScope(), LI);
+Value *NSI;
+if (IsOneZero)
+NSI = new ZExtInst(NLI, LI->getType(), "", LI);
+else
+NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
+NSI->takeName(LI);
+LI->replaceAllUsesWith(NSI);
+}
+UI->eraseFromParent();
+}
+// 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;
+}
+/// ProcessGlobal - Analyze the specified global variable and optimize it if
+/// possible.  If we make a change, return true.
+bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
+Module::global_iterator &GVI) {
+if (!GV->isDiscardableIfUnused())
+return false;
+// Do more involved optimizations if the global is internal.
+GV->removeDeadConstantUsers();
+if (GV->use_empty()) {
+DEBUG(dbgs() << "GLOBAL DEAD: " << *GV);
+GV->eraseFromParent();
+++NumDeleted;
+return true;
+}
+if (!GV->hasLocalLinkage())
+return false;
+GlobalStatus GS;
+if (GlobalStatus::analyzeGlobal(GV, GS))
+return false;
+if (!GS.IsCompared && !GV->hasUnnamedAddr()) {
+GV->setUnnamedAddr(true);
+NumUnnamed++;
+}
+if (GV->isConstant() || !GV->hasInitializer())
+return false;
+return ProcessInternalGlobal(GV, GVI, GS);
+}
+/// ProcessInternalGlobal - Analyze the specified global variable and optimize
+/// it if possible.  If we make a change, return true.
+bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
+Module::global_iterator &GVI,
+const GlobalStatus &GS) {
+// If this is a first class global and has only one accessing function
+// and this function is main (which we know is not recursive), we replace
+// the global with a local alloca in this function.
+//
+// NOTE: It doesn't make sense to promote non single-value types since we
+// are just replacing static memory to stack memory.
+//
+// If the global is in different address space, don't bring it to stack.
+if (!GS.HasMultipleAccessingFunctions &&
+GS.AccessingFunction && !GS.HasNonInstructionUser &&
+GV->getType()->getElementType()->isSingleValueType() &&
+GS.AccessingFunction->getName() == "main" &&
+GS.AccessingFunction->hasExternalLinkage() &&
+GV->getType()->getAddressSpace() == 0) {
+DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV);
+Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction
+->getEntryBlock().begin());
+Type *ElemTy = GV->getType()->getElementType();
+// FIXME: Pass Global's alignment when globals have alignment
+AllocaInst *Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), &FirstI);
+if (!isa<UndefValue>(GV->getInitializer()))
+new StoreInst(GV->getInitializer(), Alloca, &FirstI);
+GV->replaceAllUsesWith(Alloca);
+GV->eraseFromParent();
+++NumLocalized;
+return true;
+}
+// If the global is never loaded (but may be stored to), it is dead.
+// Delete it now.
+if (!GS.IsLoaded) {
+DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV);
+bool Changed;
+if (isLeakCheckerRoot(GV)) {
+// Delete any constant stores to the global.
+Changed = CleanupPointerRootUsers(GV, TLI);
+} else {
+// Delete any stores we can find to the global.  We may not be able to
+// make it completely dead though.
+Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
+}
+// If the global is dead now, delete it.
+if (GV->use_empty()) {
+GV->eraseFromParent();
+++NumDeleted;
+Changed = true;
+}
+return Changed;
+} else if (GS.StoredType <= GlobalStatus::InitializerStored) {
+DEBUG(dbgs() << "MARKING CONSTANT: " << *GV << "\n");
+GV->setConstant(true);
+// Clean up any obviously simplifiable users now.
+CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
+// If the global is dead now, just nuke it.
+if (GV->use_empty()) {
+DEBUG(dbgs() << "   *** Marking constant allowed us to simplify "
+<< "all users and delete global!\n");
+GV->eraseFromParent();
+++NumDeleted;
+}
+++NumMarked;
+return true;
+} else if (!GV->getInitializer()->getType()->isSingleValueType()) {
+if (DataLayout *TD = getAnalysisIfAvailable<DataLayout>())
+if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) {
+GVI = FirstNewGV;  // Don't skip the newly produced globals!
+return true;
+}
+} else if (GS.StoredType == GlobalStatus::StoredOnce) {
+// If the initial value for the global was an undef value, and if only
+// one other value was stored into it, we can just change the
+// initializer to be the stored value, then delete all stores to the
+// global.  This allows us to mark it constant.
+if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
+if (isa<UndefValue>(GV->getInitializer())) {
+// Change the initial value here.
+GV->setInitializer(SOVConstant);
+// Clean up any obviously simplifiable users now.
+CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
+if (GV->use_empty()) {
+DEBUG(dbgs() << "   *** Substituting initializer allowed us to "
+<< "simplify all users and delete global!\n");
+GV->eraseFromParent();
+++NumDeleted;
+} else {
+GVI = GV;
+}
+++NumSubstitute;
+return true;
+}
+// Try to optimize globals based on the knowledge that only one value
+// (besides its initializer) is ever stored to the global.
+if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GS.Ordering, GVI,
+TD, TLI))
+return true;
+// Otherwise, if the global was not a boolean, we can shrink it to be a
+// boolean.
+if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) {
+if (GS.Ordering == NotAtomic) {
+if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
+++NumShrunkToBool;
+return true;
+}
+}
+}
+}
+return false;
+}
+/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
+/// function, changing them to FastCC.
+static void ChangeCalleesToFastCall(Function *F) {
+for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
+if (isa<BlockAddress>(*UI))
+continue;
+CallSite User(cast<Instruction>(*UI));
+User.setCallingConv(CallingConv::Fast);
+}
+}
+static AttributeSet StripNest(LLVMContext &C, const AttributeSet &Attrs) {
+for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
+unsigned Index = Attrs.getSlotIndex(i);
+if (!Attrs.getSlotAttributes(i).hasAttribute(Index, Attribute::Nest))
+continue;
+// There can be only one.
+return Attrs.removeAttribute(C, Index, Attribute::Nest);
+}
+return Attrs;
+}
+static void RemoveNestAttribute(Function *F) {
+F->setAttributes(StripNest(F->getContext(), F->getAttributes()));
+for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
+if (isa<BlockAddress>(*UI))
+continue;
+CallSite User(cast<Instruction>(*UI));
+User.setAttributes(StripNest(F->getContext(), User.getAttributes()));
+}
+}
+bool GlobalOpt::OptimizeFunctions(Module &M) {
+bool Changed = false;
+// Optimize functions.
+for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
+Function *F = FI++;
+// Functions without names cannot be referenced outside this module.
+if (!F->hasName() && !F->isDeclaration())
+F->setLinkage(GlobalValue::InternalLinkage);
+F->removeDeadConstantUsers();
+if (F->isDefTriviallyDead()) {
+F->eraseFromParent();
+Changed = true;
+++NumFnDeleted;
+} else if (F->hasLocalLinkage()) {
+if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
+!F->hasAddressTaken()) {
+// If this function has C calling conventions, is not a varargs
+// function, and is only called directly, promote it to use the Fast
+// calling convention.
+F->setCallingConv(CallingConv::Fast);
+ChangeCalleesToFastCall(F);
+++NumFastCallFns;
+Changed = true;
+}
+if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
+!F->hasAddressTaken()) {
+// The function is not used by a trampoline intrinsic, so it is safe
+// to remove the 'nest' attribute.
+RemoveNestAttribute(F);
+++NumNestRemoved;
+Changed = true;
+}
+}
+}
+return Changed;
+}
+bool GlobalOpt::OptimizeGlobalVars(Module &M) {
+bool Changed = false;
+for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
+GVI != E; ) {
+GlobalVariable *GV = GVI++;
+// Global variables without names cannot be referenced outside this module.
+if (!GV->hasName() && !GV->isDeclaration())
+GV->setLinkage(GlobalValue::InternalLinkage);
+// Simplify the initializer.
+if (GV->hasInitializer())
+if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) {
+Constant *New = ConstantFoldConstantExpression(CE, TD, TLI);
+if (New && New != CE)
+GV->setInitializer(New);
+}
+Changed |= ProcessGlobal(GV, GVI);
+}
+return Changed;
+}
+/// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all
+/// initializers have an init priority of 65535.
+GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
+GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
+if (GV == 0) return 0;
+// Verify that the initializer is simple enough for us to handle. We are
+// only allowed to optimize the initializer if it is unique.
+if (!GV->hasUniqueInitializer()) return 0;
+if (isa<ConstantAggregateZero>(GV->getInitializer()))
+return GV;
+ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
+for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
+if (isa<ConstantAggregateZero>(*i))
+continue;
+ConstantStruct *CS = cast<ConstantStruct>(*i);
+if (isa<ConstantPointerNull>(CS->getOperand(1)))
+continue;
+// Must have a function or null ptr.
+if (!isa<Function>(CS->getOperand(1)))
+return 0;
+// Init priority must be standard.
+ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0));
+if (CI->getZExtValue() != 65535)
+return 0;
+}
+return GV;
+}
+/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
+/// return a list of the functions and null terminator as a vector.
+static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
+if (GV->getInitializer()->isNullValue())
+return std::vector<Function*>();
+ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
+std::vector<Function*> Result;
+Result.reserve(CA->getNumOperands());
+for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
+ConstantStruct *CS = cast<ConstantStruct>(*i);
+Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
+}
+return Result;
+}
+/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
+/// specified array, returning the new global to use.
+static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
+const std::vector<Function*> &Ctors) {
+// If we made a change, reassemble the initializer list.
+Constant *CSVals[2];
+CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535);
+CSVals[1] = 0;
+StructType *StructTy =
+cast<StructType>(GCL->getType()->getElementType()->getArrayElementType());
+// Create the new init list.
+std::vector<Constant*> CAList;
+for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
+if (Ctors[i]) {
+CSVals[1] = Ctors[i];
+} else {
+Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()),
+false);
+PointerType *PFTy = PointerType::getUnqual(FTy);
+CSVals[1] = Constant::getNullValue(PFTy);
+CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()),
+0x7fffffff);
+}
+CAList.push_back(ConstantStruct::get(StructTy, CSVals));
+}
+// Create the array initializer.
+Constant *CA = ConstantArray::get(ArrayType::get(StructTy,
+CAList.size()), CAList);
+// If we didn't change the number of elements, don't create a new GV.
+if (CA->getType() == GCL->getInitializer()->getType()) {
+GCL->setInitializer(CA);
+return GCL;
+}
+// Create the new global and insert it next to the existing list.
+GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
+GCL->getLinkage(), CA, "",
+GCL->getThreadLocalMode());
+GCL->getParent()->getGlobalList().insert(GCL, NGV);
+NGV->takeName(GCL);
+// Nuke the old list, replacing any uses with the new one.
+if (!GCL->use_empty()) {
+Constant *V = NGV;
+if (V->getType() != GCL->getType())
+V = ConstantExpr::getBitCast(V, GCL->getType());
+GCL->replaceAllUsesWith(V);
+}
+GCL->eraseFromParent();
+if (Ctors.size())
+return NGV;
+else
+return 0;
+}
+static inline bool
+isSimpleEnoughValueToCommit(Constant *C,
+SmallPtrSet<Constant*, 8> &SimpleConstants,
+const DataLayout *TD);
+/// isSimpleEnoughValueToCommit - Return true if the specified constant can be
+/// handled by the code generator.  We don't want to generate something like:
+///   void *X = &X/42;
+/// because the code generator doesn't have a relocation that can handle that.
+///
+/// This function should be called if C was not found (but just got inserted)
+/// in SimpleConstants to avoid having to rescan the same constants all the
+/// time.
+static bool isSimpleEnoughValueToCommitHelper(Constant *C,
+SmallPtrSet<Constant*, 8> &SimpleConstants,
+const DataLayout *TD) {
+// Simple integer, undef, constant aggregate zero, global addresses, etc are
+// all supported.
+if (C->getNumOperands() == 0 || isa<BlockAddress>(C) ||
+isa<GlobalValue>(C))
+return true;
+// Aggregate values are safe if all their elements are.
+if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
+isa<ConstantVector>(C)) {
+for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
+Constant *Op = cast<Constant>(C->getOperand(i));
+if (!isSimpleEnoughValueToCommit(Op, SimpleConstants, TD))
+return false;
+}
+return true;
+}
+// We don't know exactly what relocations are allowed in constant expressions,
+// so we allow &global+constantoffset, which is safe and uniformly supported
+// across targets.
+ConstantExpr *CE = cast<ConstantExpr>(C);
+switch (CE->getOpcode()) {
+case Instruction::BitCast:
+// Bitcast is fine if the casted value is fine.
+return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
+case Instruction::IntToPtr:
+case Instruction::PtrToInt:
+// int <=> ptr is fine if the int type is the same size as the
+// pointer type.
+if (!TD || TD->getTypeSizeInBits(CE->getType()) !=
+TD->getTypeSizeInBits(CE->getOperand(0)->getType()))
+return false;
+return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
+// GEP is fine if it is simple + constant offset.
+case Instruction::GetElementPtr:
+for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
+if (!isa<ConstantInt>(CE->getOperand(i)))
+return false;
+return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
+case Instruction::Add:
+// We allow simple+cst.
+if (!isa<ConstantInt>(CE->getOperand(1)))
+return false;
+return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
+}
+return false;
+}
+static inline bool
+isSimpleEnoughValueToCommit(Constant *C,
+SmallPtrSet<Constant*, 8> &SimpleConstants,
+const DataLayout *TD) {
+// If we already checked this constant, we win.
+if (!SimpleConstants.insert(C)) return true;
+// Check the constant.
+return isSimpleEnoughValueToCommitHelper(C, SimpleConstants, TD);
+}
+/// isSimpleEnoughPointerToCommit - Return true if this constant is simple
+/// enough for us to understand.  In particular, if it is a cast to anything
+/// other than from one pointer type to another pointer type, we punt.
+/// We basically just support direct accesses to globals and GEP's of
+/// globals.  This should be kept up to date with CommitValueTo.
+static bool isSimpleEnoughPointerToCommit(Constant *C) {
+// Conservatively, avoid aggregate types. This is because we don't
+// want to worry about them partially overlapping other stores.
+if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType())
+return false;
+if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
+// Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
+// external globals.
+return GV->hasUniqueInitializer();
+if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
+// Handle a constantexpr gep.
+if (CE->getOpcode() == Instruction::GetElementPtr &&
+isa<GlobalVariable>(CE->getOperand(0)) &&
+cast<GEPOperator>(CE)->isInBounds()) {
+GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
+// Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
+// external globals.
+if (!GV->hasUniqueInitializer())
+return false;
+// The first index must be zero.
+ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin()));
+if (!CI || !CI->isZero()) return false;
+// The remaining indices must be compile-time known integers within the
+// notional bounds of the corresponding static array types.
+if (!CE->isGEPWithNoNotionalOverIndexing())
+return false;
+return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
+// A constantexpr bitcast from a pointer to another pointer is a no-op,
+// and we know how to evaluate it by moving the bitcast from the pointer
+// operand to the value operand.
+} else if (CE->getOpcode() == Instruction::BitCast &&
+isa<GlobalVariable>(CE->getOperand(0))) {
+// Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
+// external globals.
+return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer();
+}
+}
+return false;
+}
+/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
+/// initializer.  This returns 'Init' modified to reflect 'Val' stored into it.
+/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
+static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
+ConstantExpr *Addr, unsigned OpNo) {
+// Base case of the recursion.
+if (OpNo == Addr->getNumOperands()) {
+assert(Val->getType() == Init->getType() && "Type mismatch!");
+return Val;
+}
+SmallVector<Constant*, 32> Elts;
+if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
+// Break up the constant into its elements.
+for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
+Elts.push_back(Init->getAggregateElement(i));
+// Replace the element that we are supposed to.
+ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
+unsigned Idx = CU->getZExtValue();
+assert(Idx < STy->getNumElements() && "Struct index out of range!");
+Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
+// Return the modified struct.
+return ConstantStruct::get(STy, Elts);
+}
+ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
+SequentialType *InitTy = cast<SequentialType>(Init->getType());
+uint64_t NumElts;
+if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy))
+NumElts = ATy->getNumElements();
+else
+NumElts = InitTy->getVectorNumElements();
+// Break up the array into elements.
+for (uint64_t i = 0, e = NumElts; i != e; ++i)
+Elts.push_back(Init->getAggregateElement(i));
+assert(CI->getZExtValue() < NumElts);
+Elts[CI->getZExtValue()] =
+EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
+if (Init->getType()->isArrayTy())
+return ConstantArray::get(cast<ArrayType>(InitTy), Elts);
+return ConstantVector::get(Elts);
+}
+/// CommitValueTo - We have decided that Addr (which satisfies the predicate
+/// isSimpleEnoughPointerToCommit) should get Val as its value.  Make it happen.
+static void CommitValueTo(Constant *Val, Constant *Addr) {
+if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
+assert(GV->hasInitializer());
+GV->setInitializer(Val);
+return;
+}
+ConstantExpr *CE = cast<ConstantExpr>(Addr);
+GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
+GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2));
+}
+namespace {
+/// Evaluator - This class evaluates LLVM IR, producing the Constant
+/// representing each SSA instruction.  Changes to global variables are stored
+/// in a mapping that can be iterated over after the evaluation is complete.
+/// Once an evaluation call fails, the evaluation object should not be reused.
+class Evaluator {
+public:
+Evaluator(const DataLayout *TD, const TargetLibraryInfo *TLI)
+: TD(TD), TLI(TLI) {
+ValueStack.push_back(new DenseMap<Value*, Constant*>);
+}
+~Evaluator() {
+DeleteContainerPointers(ValueStack);
+while (!AllocaTmps.empty()) {
+GlobalVariable *Tmp = AllocaTmps.back();
+AllocaTmps.pop_back();
+// If there are still users of the alloca, the program is doing something
+// silly, e.g. storing the address of the alloca somewhere and using it
+// later.  Since this is undefined, we'll just make it be null.
+if (!Tmp->use_empty())
+Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
+delete Tmp;
+}
+}
+/// EvaluateFunction - Evaluate a call to function F, returning true if
+/// successful, false if we can't evaluate it.  ActualArgs contains the formal
+/// arguments for the function.
+bool EvaluateFunction(Function *F, Constant *&RetVal,
+const SmallVectorImpl<Constant*> &ActualArgs);
+/// EvaluateBlock - Evaluate all instructions in block BB, returning true if
+/// successful, false if we can't evaluate it.  NewBB returns the next BB that
+/// control flows into, or null upon return.
+bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB);
+Constant *getVal(Value *V) {
+if (Constant *CV = dyn_cast<Constant>(V)) return CV;
+Constant *R = ValueStack.back()->lookup(V);
+assert(R && "Reference to an uncomputed value!");
+return R;
+}
+void setVal(Value *V, Constant *C) {
+ValueStack.back()->operator[](V) = C;
+}
+const DenseMap<Constant*, Constant*> &getMutatedMemory() const {
+return MutatedMemory;
+}
+const SmallPtrSet<GlobalVariable*, 8> &getInvariants() const {
+return Invariants;
+}
+private:
+Constant *ComputeLoadResult(Constant *P);
+/// ValueStack - As we compute SSA register values, we store their contents
+/// here. The back of the vector contains the current function and the stack
+/// contains the values in the calling frames.
+SmallVector<DenseMap<Value*, Constant*>*, 4> ValueStack;
+/// CallStack - This is used to detect recursion.  In pathological situations
+/// we could hit exponential behavior, but at least there is nothing
+/// unbounded.
+SmallVector<Function*, 4> CallStack;
+/// MutatedMemory - For each store we execute, we update this map.  Loads
+/// check this to get the most up-to-date value.  If evaluation is successful,
+/// this state is committed to the process.
+DenseMap<Constant*, Constant*> MutatedMemory;
+/// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
+/// to represent its body.  This vector is needed so we can delete the
+/// temporary globals when we are done.
+SmallVector<GlobalVariable*, 32> AllocaTmps;
+/// Invariants - These global variables have been marked invariant by the
+/// static constructor.
+SmallPtrSet<GlobalVariable*, 8> Invariants;
+/// SimpleConstants - These are constants we have checked and know to be
+/// simple enough to live in a static initializer of a global.
+SmallPtrSet<Constant*, 8> SimpleConstants;
+const DataLayout *TD;
+const TargetLibraryInfo *TLI;
+};
+}  // anonymous namespace
+/// ComputeLoadResult - Return the value that would be computed by a load from
+/// P after the stores reflected by 'memory' have been performed.  If we can't
+/// decide, return null.
+Constant *Evaluator::ComputeLoadResult(Constant *P) {
+// If this memory location has been recently stored, use the stored value: it
+// is the most up-to-date.
+DenseMap<Constant*, Constant*>::const_iterator I = MutatedMemory.find(P);
+if (I != MutatedMemory.end()) return I->second;
+// Access it.
+if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
+if (GV->hasDefinitiveInitializer())
+return GV->getInitializer();
+return 0;
+}
+// Handle a constantexpr getelementptr.
+if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
+if (CE->getOpcode() == Instruction::GetElementPtr &&
+isa<GlobalVariable>(CE->getOperand(0))) {
+GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
+if (GV->hasDefinitiveInitializer())
+return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
+}
+return 0;  // don't know how to evaluate.
+}
+/// EvaluateBlock - Evaluate all instructions in block BB, returning true if
+/// successful, false if we can't evaluate it.  NewBB returns the next BB that
+/// control flows into, or null upon return.
+bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
+BasicBlock *&NextBB) {
+// This is the main evaluation loop.
+while (1) {
+Constant *InstResult = 0;
+DEBUG(dbgs() << "Evaluating Instruction: " << *CurInst << "\n");
+if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
+if (!SI->isSimple()) {
+DEBUG(dbgs() << "Store is not simple! Can not evaluate.\n");
+return false;  // no volatile/atomic accesses.
+}
+Constant *Ptr = getVal(SI->getOperand(1));
+if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
+DEBUG(dbgs() << "Folding constant ptr expression: " << *Ptr);
+Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
+DEBUG(dbgs() << "; To: " << *Ptr << "\n");
+}
+if (!isSimpleEnoughPointerToCommit(Ptr)) {
+// If this is too complex for us to commit, reject it.
+DEBUG(dbgs() << "Pointer is too complex for us to evaluate store.");
+return false;
+}
+Constant *Val = getVal(SI->getOperand(0));
+// If this might be too difficult for the backend to handle (e.g. the addr
+// of one global variable divided by another) then we can't commit it.
+if (!isSimpleEnoughValueToCommit(Val, SimpleConstants, TD)) {
+DEBUG(dbgs() << "Store value is too complex to evaluate store. " << *Val
+<< "\n");
+return false;
+}
+if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
+if (CE->getOpcode() == Instruction::BitCast) {
+DEBUG(dbgs() << "Attempting to resolve bitcast on constant ptr.\n");
+// If we're evaluating a store through a bitcast, then we need
+// to pull the bitcast off the pointer type and push it onto the
+// stored value.
+Ptr = CE->getOperand(0);
+Type *NewTy = cast<PointerType>(Ptr->getType())->getElementType();
+// In order to push the bitcast onto the stored value, a bitcast
+// from NewTy to Val's type must be legal.  If it's not, we can try
+// introspecting NewTy to find a legal conversion.
+while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) {
+// If NewTy is a struct, we can convert the pointer to the struct
+// into a pointer to its first member.
+// FIXME: This could be extended to support arrays as well.
+if (StructType *STy = dyn_cast<StructType>(NewTy)) {
+NewTy = STy->getTypeAtIndex(0U);
+IntegerType *IdxTy = IntegerType::get(NewTy->getContext(), 32);
+Constant *IdxZero = ConstantInt::get(IdxTy, 0, false);
+Constant * const IdxList[] = {IdxZero, IdxZero};
+Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList);
+if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
+Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
+// If we can't improve the situation by introspecting NewTy,
+// we have to give up.
+} else {
+DEBUG(dbgs() << "Failed to bitcast constant ptr, can not "
+"evaluate.\n");
+return false;
+}
+}
+// If we found compatible types, go ahead and push the bitcast
+// onto the stored value.
+Val = ConstantExpr::getBitCast(Val, NewTy);
+DEBUG(dbgs() << "Evaluated bitcast: " << *Val << "\n");
+}
+}
+MutatedMemory[Ptr] = Val;
+} else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
+InstResult = ConstantExpr::get(BO->getOpcode(),
+getVal(BO->getOperand(0)),
+getVal(BO->getOperand(1)));
+DEBUG(dbgs() << "Found a BinaryOperator! Simplifying: " << *InstResult
+<< "\n");
+} else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
+InstResult = ConstantExpr::getCompare(CI->getPredicate(),
+getVal(CI->getOperand(0)),
+getVal(CI->getOperand(1)));
+DEBUG(dbgs() << "Found a CmpInst! Simplifying: " << *InstResult
+<< "\n");
+} else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
+InstResult = ConstantExpr::getCast(CI->getOpcode(),
+getVal(CI->getOperand(0)),
+CI->getType());
+DEBUG(dbgs() << "Found a Cast! Simplifying: " << *InstResult
+<< "\n");
+} else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
+InstResult = ConstantExpr::getSelect(getVal(SI->getOperand(0)),
+getVal(SI->getOperand(1)),
+getVal(SI->getOperand(2)));
+DEBUG(dbgs() << "Found a Select! Simplifying: " << *InstResult
+<< "\n");
+} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
+Constant *P = getVal(GEP->getOperand(0));
+SmallVector<Constant*, 8> GEPOps;
+for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
+i != e; ++i)
+GEPOps.push_back(getVal(*i));
+InstResult =
+ConstantExpr::getGetElementPtr(P, GEPOps,
+cast<GEPOperator>(GEP)->isInBounds());
+DEBUG(dbgs() << "Found a GEP! Simplifying: " << *InstResult
+<< "\n");
+} else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
+if (!LI->isSimple()) {
+DEBUG(dbgs() << "Found a Load! Not a simple load, can not evaluate.\n");
+return false;  // no volatile/atomic accesses.
+}
+Constant *Ptr = getVal(LI->getOperand(0));
+if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
+Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
+DEBUG(dbgs() << "Found a constant pointer expression, constant "
+"folding: " << *Ptr << "\n");
+}
+InstResult = ComputeLoadResult(Ptr);
+if (InstResult == 0) {
+DEBUG(dbgs() << "Failed to compute load result. Can not evaluate load."
+"\n");
+return false; // Could not evaluate load.
+}
+DEBUG(dbgs() << "Evaluated load: " << *InstResult << "\n");
+} else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
+if (AI->isArrayAllocation()) {
+DEBUG(dbgs() << "Found an array alloca. Can not evaluate.\n");
+return false;  // Cannot handle array allocs.
+}
+Type *Ty = AI->getType()->getElementType();
+AllocaTmps.push_back(new GlobalVariable(Ty, false,
+GlobalValue::InternalLinkage,
+UndefValue::get(Ty),
+AI->getName()));
+InstResult = AllocaTmps.back();
+DEBUG(dbgs() << "Found an alloca. Result: " << *InstResult << "\n");
+} else if (isa<CallInst>(CurInst) || isa<InvokeInst>(CurInst)) {
+CallSite CS(CurInst);
+// Debug info can safely be ignored here.
+if (isa<DbgInfoIntrinsic>(CS.getInstruction())) {
+DEBUG(dbgs() << "Ignoring debug info.\n");
+++CurInst;
+continue;
+}
+// Cannot handle inline asm.
+if (isa<InlineAsm>(CS.getCalledValue())) {
+DEBUG(dbgs() << "Found inline asm, can not evaluate.\n");
+return false;
+}
+if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
+if (MemSetInst *MSI = dyn_cast<MemSetInst>(II)) {
+if (MSI->isVolatile()) {
+DEBUG(dbgs() << "Can not optimize a volatile memset " <<
+"intrinsic.\n");
+return false;
+}
+Constant *Ptr = getVal(MSI->getDest());
+Constant *Val = getVal(MSI->getValue());
+Constant *DestVal = ComputeLoadResult(getVal(Ptr));
+if (Val->isNullValue() && DestVal && DestVal->isNullValue()) {
+// This memset is a no-op.
+DEBUG(dbgs() << "Ignoring no-op memset.\n");
+++CurInst;
+continue;
+}
+}
+if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
+II->getIntrinsicID() == Intrinsic::lifetime_end) {
+DEBUG(dbgs() << "Ignoring lifetime intrinsic.\n");
+++CurInst;
+continue;
+}
+if (II->getIntrinsicID() == Intrinsic::invariant_start) {
+// We don't insert an entry into Values, as it doesn't have a
+// meaningful return value.
+if (!II->use_empty()) {
+DEBUG(dbgs() << "Found unused invariant_start. Cant evaluate.\n");
+return false;
+}
+ConstantInt *Size = cast<ConstantInt>(II->getArgOperand(0));
+Value *PtrArg = getVal(II->getArgOperand(1));
+Value *Ptr = PtrArg->stripPointerCasts();
+if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
+Type *ElemTy = cast<PointerType>(GV->getType())->getElementType();
+if (TD && !Size->isAllOnesValue() &&
+Size->getValue().getLimitedValue() >=
+TD->getTypeStoreSize(ElemTy)) {
+Invariants.insert(GV);
+DEBUG(dbgs() << "Found a global var that is an invariant: " << *GV
+<< "\n");
+} else {
+DEBUG(dbgs() << "Found a global var, but can not treat it as an "
+"invariant.\n");
+}
+}
+// Continue even if we do nothing.
+++CurInst;
+continue;
+}
+DEBUG(dbgs() << "Unknown intrinsic. Can not evaluate.\n");
+return false;
+}
+// Resolve function pointers.
+Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue()));
+if (!Callee || Callee->mayBeOverridden()) {
+DEBUG(dbgs() << "Can not resolve function pointer.\n");
+return false;  // Cannot resolve.
+}
+SmallVector<Constant*, 8> Formals;
+for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end(); i != e; ++i)
+Formals.push_back(getVal(*i));
+if (Callee->isDeclaration()) {
+// If this is a function we can constant fold, do it.
+if (Constant *C = ConstantFoldCall(Callee, Formals, TLI)) {
+InstResult = C;
+DEBUG(dbgs() << "Constant folded function call. Result: " <<
+*InstResult << "\n");
+} else {
+DEBUG(dbgs() << "Can not constant fold function call.\n");
+return false;
+}
+} else {
+if (Callee->getFunctionType()->isVarArg()) {
+DEBUG(dbgs() << "Can not constant fold vararg function call.\n");
+return false;
+}
+Constant *RetVal = 0;
+// Execute the call, if successful, use the return value.
+ValueStack.push_back(new DenseMap<Value*, Constant*>);
+if (!EvaluateFunction(Callee, RetVal, Formals)) {
+DEBUG(dbgs() << "Failed to evaluate function.\n");
+return false;
+}
+delete ValueStack.pop_back_val();
+InstResult = RetVal;
+if (InstResult != NULL) {
+DEBUG(dbgs() << "Successfully evaluated function. Result: " <<
+InstResult << "\n\n");
+} else {
+DEBUG(dbgs() << "Successfully evaluated function. Result: 0\n\n");
+}
+}
+} else if (isa<TerminatorInst>(CurInst)) {
+DEBUG(dbgs() << "Found a terminator instruction.\n");
+if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
+if (BI->isUnconditional()) {
+NextBB = BI->getSuccessor(0);
+} else {
+ConstantInt *Cond =
+dyn_cast<ConstantInt>(getVal(BI->getCondition()));
+if (!Cond) return false;  // Cannot determine.
+NextBB = BI->getSuccessor(!Cond->getZExtValue());
+}
+} else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
+ConstantInt *Val =
+dyn_cast<ConstantInt>(getVal(SI->getCondition()));
+if (!Val) return false;  // Cannot determine.
+NextBB = SI->findCaseValue(Val).getCaseSuccessor();
+} else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) {
+Value *Val = getVal(IBI->getAddress())->stripPointerCasts();
+if (BlockAddress *BA = dyn_cast<BlockAddress>(Val))
+NextBB = BA->getBasicBlock();
+else
+return false;  // Cannot determine.
+} else if (isa<ReturnInst>(CurInst)) {
+NextBB = 0;
+} else {
+// invoke, unwind, resume, unreachable.
+DEBUG(dbgs() << "Can not handle terminator.");
+return false;  // Cannot handle this terminator.
+}
+// We succeeded at evaluating this block!
+DEBUG(dbgs() << "Successfully evaluated block.\n");
+return true;
+} else {
+// Did not know how to evaluate this!
+DEBUG(dbgs() << "Failed to evaluate block due to unhandled instruction."
+"\n");
+return false;
+}
+if (!CurInst->use_empty()) {
+if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult))
+InstResult = ConstantFoldConstantExpression(CE, TD, TLI);
+setVal(CurInst, InstResult);
+}
+// If we just processed an invoke, we finished evaluating the block.
+if (InvokeInst *II = dyn_cast<InvokeInst>(CurInst)) {
+NextBB = II->getNormalDest();
+DEBUG(dbgs() << "Found an invoke instruction. Finished Block.\n\n");
+return true;
+}
+// Advance program counter.
+++CurInst;
+}
+}
+/// EvaluateFunction - Evaluate a call to function F, returning true if
+/// successful, false if we can't evaluate it.  ActualArgs contains the formal
+/// arguments for the function.
+bool Evaluator::EvaluateFunction(Function *F, Constant *&RetVal,
+const SmallVectorImpl<Constant*> &ActualArgs) {
+// Check to see if this function is already executing (recursion).  If so,
+// bail out.  TODO: we might want to accept limited recursion.
+if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
+return false;
+CallStack.push_back(F);
+// Initialize arguments to the incoming values specified.
+unsigned ArgNo = 0;
+for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
+++AI, ++ArgNo)
+setVal(AI, ActualArgs[ArgNo]);
+// ExecutedBlocks - We only handle non-looping, non-recursive code.  As such,
+// we can only evaluate any one basic block at most once.  This set keeps
+// track of what we have executed so we can detect recursive cases etc.
+SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
+// CurBB - The current basic block we're evaluating.
+BasicBlock *CurBB = F->begin();
+BasicBlock::iterator CurInst = CurBB->begin();
+while (1) {
+BasicBlock *NextBB = 0; // Initialized to avoid compiler warnings.
+DEBUG(dbgs() << "Trying to evaluate BB: " << *CurBB << "\n");
+if (!EvaluateBlock(CurInst, NextBB))
+return false;
+if (NextBB == 0) {
+// Successfully running until there's no next block means that we found
+// the return.  Fill it the return value and pop the call stack.
+ReturnInst *RI = cast<ReturnInst>(CurBB->getTerminator());
+if (RI->getNumOperands())
+RetVal = getVal(RI->getOperand(0));
+CallStack.pop_back();
+return true;
+}
+// Okay, we succeeded in evaluating this control flow.  See if we have
+// executed the new block before.  If so, we have a looping function,
+// which we cannot evaluate in reasonable time.
+if (!ExecutedBlocks.insert(NextBB))
+return false;  // looped!
+// Okay, we have never been in this block before.  Check to see if there
+// are any PHI nodes.  If so, evaluate them with information about where
+// we came from.
+PHINode *PN = 0;
+for (CurInst = NextBB->begin();
+(PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
+setVal(PN, getVal(PN->getIncomingValueForBlock(CurBB)));
+// Advance to the next block.
+CurBB = NextBB;
+}
+}
+/// EvaluateStaticConstructor - Evaluate static constructors in the function, if
+/// we can.  Return true if we can, false otherwise.
+static bool EvaluateStaticConstructor(Function *F, const DataLayout *TD,
+const TargetLibraryInfo *TLI) {
+// Call the function.
+Evaluator Eval(TD, TLI);
+Constant *RetValDummy;
+bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy,
+SmallVector<Constant*, 0>());
+if (EvalSuccess) {
+// We succeeded at evaluation: commit the result.
+DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
+<< F->getName() << "' to " << Eval.getMutatedMemory().size()
+<< " stores.\n");
+for (DenseMap<Constant*, Constant*>::const_iterator I =
+Eval.getMutatedMemory().begin(), E = Eval.getMutatedMemory().end();
+I != E; ++I)
+CommitValueTo(I->second, I->first);
+for (SmallPtrSet<GlobalVariable*, 8>::const_iterator I =
+Eval.getInvariants().begin(), E = Eval.getInvariants().end();
+I != E; ++I)
+(*I)->setConstant(true);
+}
+return EvalSuccess;
+}
+/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
+/// Return true if anything changed.
+bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
+std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
+bool MadeChange = false;
+if (Ctors.empty()) return false;
+// Loop over global ctors, optimizing them when we can.
+for (unsigned i = 0; i != Ctors.size(); ++i) {
+Function *F = Ctors[i];
+// Found a null terminator in the middle of the list, prune off the rest of
+// the list.
+if (F == 0) {
+if (i != Ctors.size()-1) {
+Ctors.resize(i+1);
+MadeChange = true;
+}
+break;
+}
+DEBUG(dbgs() << "Optimizing Global Constructor: " << *F << "\n");
+// We cannot simplify external ctor functions.
+if (F->empty()) continue;
+// If we can evaluate the ctor at compile time, do.
+if (EvaluateStaticConstructor(F, TD, TLI)) {
+Ctors.erase(Ctors.begin()+i);
+MadeChange = true;
+--i;
+++NumCtorsEvaluated;
+continue;
+}
+}
+if (!MadeChange) return false;
+GCL = InstallGlobalCtors(GCL, Ctors);
+return true;
+}
+static int compareNames(Constant *const *A, Constant *const *B) {
+return (*A)->getName().compare((*B)->getName());
+}
+static void setUsedInitializer(GlobalVariable &V,
+SmallPtrSet<GlobalValue *, 8> Init) {
+if (Init.empty()) {
+V.eraseFromParent();
+return;
+}
+SmallVector<llvm::Constant *, 8> UsedArray;
+PointerType *Int8PtrTy = Type::getInt8PtrTy(V.getContext());
+for (SmallPtrSet<GlobalValue *, 8>::iterator I = Init.begin(), E = Init.end();
+I != E; ++I) {
+Constant *Cast = llvm::ConstantExpr::getBitCast(*I, 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, llvm::GlobalValue::AppendingLinkage,
+llvm::ConstantArray::get(ATy, UsedArray), "");
+NV->takeName(&V);
+NV->setSection("llvm.metadata");
+delete &V;
+}
+namespace {
+/// \brief 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);
+}
+typedef SmallPtrSet<GlobalValue *, 8>::iterator iterator;
+iterator usedBegin() { return Used.begin(); }
+iterator usedEnd() { return Used.end(); }
+iterator compilerUsedBegin() { return CompilerUsed.begin(); }
+iterator compilerUsedEnd() { return CompilerUsed.end(); }
+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); }
+bool compilerUsedInsert(GlobalValue *GV) { return CompilerUsed.insert(GV); }
+void syncVariablesAndSets() {
+if (UsedV)
+setUsedInitializer(*UsedV, Used);
+if (CompilerUsedV)
+setUsedInitializer(*CompilerUsedV, CompilerUsed);
+}
+};
+}
+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, 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;
+}
+bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
+bool Changed = false;
+LLVMUsed Used(M);
+for (SmallPtrSet<GlobalValue *, 8>::iterator I = Used.usedBegin(),
+E = Used.usedEnd();
+I != E; ++I)
+Used.compilerUsedErase(*I);
+for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
+I != E;) {
+Module::alias_iterator J = I++;
+// Aliases without names cannot be referenced outside this module.
+if (!J->hasName() && !J->isDeclaration())
+J->setLinkage(GlobalValue::InternalLinkage);
+// If the aliasee may change at link time, nothing can be done - bail out.
+if (J->mayBeOverridden())
+continue;
+Constant *Aliasee = J->getAliasee();
+GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
+Target->removeDeadConstantUsers();
+// Make all users of the alias use the aliasee instead.
+bool RenameTarget;
+if (!hasUsesToReplace(*J, Used, RenameTarget))
+continue;
+J->replaceAllUsesWith(Aliasee);
+++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->GlobalValue::copyAttributesFrom(J);
+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) {
+if (!TLI->has(LibFunc::cxa_atexit))
+return 0;
+Function *Fn = M.getFunction(TLI->getName(LibFunc::cxa_atexit));
+if (!Fn)
+return 0;
+FunctionType *FTy = Fn->getFunctionType();
+// Checking that the function has the right return type, the right number of
+// parameters and that they all have pointer types should be enough.
+if (!FTy->getReturnType()->isIntegerTy() ||
+FTy->getNumParams() != 3 ||
+!FTy->getParamType(0)->isPointerTy() ||
+!FTy->getParamType(1)->isPointerTy() ||
+!FTy->getParamType(2)->isPointerTy())
+return 0;
+return Fn;
+}
+/// cxxDtorIsEmpty - Returns whether the given function is an empty C++
+/// destructor and can therefore be eliminated.
+/// Note that we assume that other optimization passes have already simplified
+/// the code so we only look for a function with a single basic block, where
+/// the only allowed instructions are 'ret', 'call' to an empty C++ dtor and
+/// other side-effect free instructions.
+static bool cxxDtorIsEmpty(const Function &Fn,
+SmallPtrSet<const Function *, 8> &CalledFunctions) {
+// FIXME: We could eliminate C++ destructors if they're readonly/readnone and
+// nounwind, but that doesn't seem worth doing.
+if (Fn.isDeclaration())
+return false;
+if (++Fn.begin() != Fn.end())
+return false;
+const BasicBlock &EntryBlock = Fn.getEntryBlock();
+for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end();
+I != E; ++I) {
+if (const CallInst *CI = dyn_cast<CallInst>(I)) {
+// Ignore debug intrinsics.
+if (isa<DbgInfoIntrinsic>(CI))
+continue;
+const Function *CalledFn = CI->getCalledFunction();
+if (!CalledFn)
+return false;
+SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions);
+// Don't treat recursive functions as empty.
+if (!NewCalledFunctions.insert(CalledFn))
+return false;
+if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions))
+return false;
+} else if (isa<ReturnInst>(*I))
+return true; // We're done.
+else if (I->mayHaveSideEffects())
+return false; // Destructor with side effects, bail.
+}
+return false;
+}
+bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) {
+/// Itanium C++ ABI p3.3.5:
+///
+///   After constructing a global (or local static) object, that will require
+///   destruction on exit, a termination function is registered as follows:
+///
+///   extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
+///
+///   This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the
+///   call f(p) when DSO d is unloaded, before all such termination calls
+///   registered before this one. It returns zero if registration is
+///   successful, nonzero on failure.
+// This pass will look for calls to __cxa_atexit where the function is trivial
+// and remove them.
+bool Changed = false;
+for (Function::use_iterator I = CXAAtExitFn->use_begin(),
+E = CXAAtExitFn->use_end(); I != E;) {
+// We're only interested in calls. Theoretically, we could handle invoke
+// instructions as well, but neither llvm-gcc nor clang generate invokes
+// to __cxa_atexit.
+CallInst *CI = dyn_cast<CallInst>(*I++);
+if (!CI)
+continue;
+Function *DtorFn =
+dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts());
+if (!DtorFn)
+continue;
+SmallPtrSet<const Function *, 8> CalledFunctions;
+if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions))
+continue;
+// Just remove the call.
+CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
+CI->eraseFromParent();
+++NumCXXDtorsRemoved;
+Changed |= true;
+}
+return Changed;
+}
+bool GlobalOpt::runOnModule(Module &M) {
+bool Changed = false;
+TD = getAnalysisIfAvailable<DataLayout>();
+TLI = &getAnalysis<TargetLibraryInfo>();
+// Try to find the llvm.globalctors list.
+GlobalVariable *GlobalCtors = FindGlobalCtors(M);
+bool LocalChange = true;
+while (LocalChange) {
+LocalChange = false;
+// Delete functions that are trivially dead, ccc -> fastcc
+LocalChange |= OptimizeFunctions(M);
+// Optimize global_ctors list.
+if (GlobalCtors)
+LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
+// Optimize non-address-taken globals.
+LocalChange |= OptimizeGlobalVars(M);
+// Resolve aliases, when possible.
+LocalChange |= OptimizeGlobalAliases(M);
+// Try to remove trivial global destructors if 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;
+}

Mercurial > hg > CbC > CbC_llvm

comparison lib/Transforms/IPO/GlobalOpt.cpp @ 0:95c75e76d11b LLVM3.4