| //===-- ArgumentPromotion.cpp - Promote by-reference arguments ------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This pass promotes "by reference" arguments to be "by value" arguments. In |
| // practice, this means looking for internal functions that have pointer |
| // arguments. If it can prove, through the use of alias analysis, that an |
| // argument is *only* loaded, then it can pass the value into the function |
| // instead of the address of the value. This can cause recursive simplification |
| // of code and lead to the elimination of allocas (especially in C++ template |
| // code like the STL). |
| // |
| // This pass also handles aggregate arguments that are passed into a function, |
| // scalarizing them if the elements of the aggregate are only loaded. Note that |
| // by default it refuses to scalarize aggregates which would require passing in |
| // more than three operands to the function, because passing thousands of |
| // operands for a large array or structure is unprofitable! This limit can be |
| // configured or disabled, however. |
| // |
| // Note that this transformation could also be done for arguments that are only |
| // stored to (returning the value instead), but does not currently. This case |
| // would be best handled when and if LLVM begins supporting multiple return |
| // values from functions. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "argpromotion" |
| #include "llvm/Transforms/IPO.h" |
| #include "llvm/Constants.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Module.h" |
| #include "llvm/CallGraphSCCPass.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/LLVMContext.h" |
| #include "llvm/Analysis/AliasAnalysis.h" |
| #include "llvm/Analysis/CallGraph.h" |
| #include "llvm/Support/CallSite.h" |
| #include "llvm/Support/CFG.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/ADT/DepthFirstIterator.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/ADT/StringExtras.h" |
| #include <set> |
| using namespace llvm; |
| |
| STATISTIC(NumArgumentsPromoted , "Number of pointer arguments promoted"); |
| STATISTIC(NumAggregatesPromoted, "Number of aggregate arguments promoted"); |
| STATISTIC(NumByValArgsPromoted , "Number of byval arguments promoted"); |
| STATISTIC(NumArgumentsDead , "Number of dead pointer args eliminated"); |
| |
| namespace { |
| /// ArgPromotion - The 'by reference' to 'by value' argument promotion pass. |
| /// |
| struct ArgPromotion : public CallGraphSCCPass { |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequired<AliasAnalysis>(); |
| CallGraphSCCPass::getAnalysisUsage(AU); |
| } |
| |
| virtual bool runOnSCC(CallGraphSCC &SCC); |
| static char ID; // Pass identification, replacement for typeid |
| explicit ArgPromotion(unsigned maxElements = 3) |
| : CallGraphSCCPass(ID), maxElements(maxElements) { |
| initializeArgPromotionPass(*PassRegistry::getPassRegistry()); |
| } |
| |
| /// A vector used to hold the indices of a single GEP instruction |
| typedef std::vector<uint64_t> IndicesVector; |
| |
| private: |
| CallGraphNode *PromoteArguments(CallGraphNode *CGN); |
| bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const; |
| CallGraphNode *DoPromotion(Function *F, |
| SmallPtrSet<Argument*, 8> &ArgsToPromote, |
| SmallPtrSet<Argument*, 8> &ByValArgsToTransform); |
| /// The maximum number of elements to expand, or 0 for unlimited. |
| unsigned maxElements; |
| }; |
| } |
| |
| char ArgPromotion::ID = 0; |
| INITIALIZE_PASS_BEGIN(ArgPromotion, "argpromotion", |
| "Promote 'by reference' arguments to scalars", false, false) |
| INITIALIZE_AG_DEPENDENCY(AliasAnalysis) |
| INITIALIZE_AG_DEPENDENCY(CallGraph) |
| INITIALIZE_PASS_END(ArgPromotion, "argpromotion", |
| "Promote 'by reference' arguments to scalars", false, false) |
| |
| Pass *llvm::createArgumentPromotionPass(unsigned maxElements) { |
| return new ArgPromotion(maxElements); |
| } |
| |
| bool ArgPromotion::runOnSCC(CallGraphSCC &SCC) { |
| bool Changed = false, LocalChange; |
| |
| do { // Iterate until we stop promoting from this SCC. |
| LocalChange = false; |
| // Attempt to promote arguments from all functions in this SCC. |
| for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) { |
| if (CallGraphNode *CGN = PromoteArguments(*I)) { |
| LocalChange = true; |
| SCC.ReplaceNode(*I, CGN); |
| } |
| } |
| Changed |= LocalChange; // Remember that we changed something. |
| } while (LocalChange); |
| |
| return Changed; |
| } |
| |
| /// PromoteArguments - This method checks the specified function to see if there |
| /// are any promotable arguments and if it is safe to promote the function (for |
| /// example, all callers are direct). If safe to promote some arguments, it |
| /// calls the DoPromotion method. |
| /// |
| CallGraphNode *ArgPromotion::PromoteArguments(CallGraphNode *CGN) { |
| Function *F = CGN->getFunction(); |
| |
| // Make sure that it is local to this module. |
| if (!F || !F->hasLocalLinkage()) return 0; |
| |
| // First check: see if there are any pointer arguments! If not, quick exit. |
| SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs; |
| unsigned ArgNo = 0; |
| for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); |
| I != E; ++I, ++ArgNo) |
| if (I->getType()->isPointerTy()) |
| PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo)); |
| if (PointerArgs.empty()) return 0; |
| |
| // Second check: make sure that all callers are direct callers. We can't |
| // transform functions that have indirect callers. Also see if the function |
| // is self-recursive. |
| bool isSelfRecursive = false; |
| for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); |
| UI != E; ++UI) { |
| CallSite CS(*UI); |
| // Must be a direct call. |
| if (CS.getInstruction() == 0 || !CS.isCallee(UI)) return 0; |
| |
| if (CS.getInstruction()->getParent()->getParent() == F) |
| isSelfRecursive = true; |
| } |
| |
| // Check to see which arguments are promotable. If an argument is promotable, |
| // add it to ArgsToPromote. |
| SmallPtrSet<Argument*, 8> ArgsToPromote; |
| SmallPtrSet<Argument*, 8> ByValArgsToTransform; |
| for (unsigned i = 0; i != PointerArgs.size(); ++i) { |
| bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, Attribute::ByVal); |
| Argument *PtrArg = PointerArgs[i].first; |
| Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType(); |
| |
| // If this is a byval argument, and if the aggregate type is small, just |
| // pass the elements, which is always safe. |
| if (isByVal) { |
| if (StructType *STy = dyn_cast<StructType>(AgTy)) { |
| if (maxElements > 0 && STy->getNumElements() > maxElements) { |
| DEBUG(dbgs() << "argpromotion disable promoting argument '" |
| << PtrArg->getName() << "' because it would require adding more" |
| << " than " << maxElements << " arguments to the function.\n"); |
| continue; |
| } |
| |
| // If all the elements are single-value types, we can promote it. |
| bool AllSimple = true; |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { |
| if (!STy->getElementType(i)->isSingleValueType()) { |
| AllSimple = false; |
| break; |
| } |
| } |
| |
| // Safe to transform, don't even bother trying to "promote" it. |
| // Passing the elements as a scalar will allow scalarrepl to hack on |
| // the new alloca we introduce. |
| if (AllSimple) { |
| ByValArgsToTransform.insert(PtrArg); |
| continue; |
| } |
| } |
| } |
| |
| // If the argument is a recursive type and we're in a recursive |
| // function, we could end up infinitely peeling the function argument. |
| if (isSelfRecursive) { |
| if (StructType *STy = dyn_cast<StructType>(AgTy)) { |
| bool RecursiveType = false; |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { |
| if (STy->getElementType(i) == PtrArg->getType()) { |
| RecursiveType = true; |
| break; |
| } |
| } |
| if (RecursiveType) |
| continue; |
| } |
| } |
| |
| // Otherwise, see if we can promote the pointer to its value. |
| if (isSafeToPromoteArgument(PtrArg, isByVal)) |
| ArgsToPromote.insert(PtrArg); |
| } |
| |
| // No promotable pointer arguments. |
| if (ArgsToPromote.empty() && ByValArgsToTransform.empty()) |
| return 0; |
| |
| return DoPromotion(F, ArgsToPromote, ByValArgsToTransform); |
| } |
| |
| /// AllCallersPassInValidPointerForArgument - Return true if we can prove that |
| /// all callees pass in a valid pointer for the specified function argument. |
| static bool AllCallersPassInValidPointerForArgument(Argument *Arg) { |
| Function *Callee = Arg->getParent(); |
| |
| unsigned ArgNo = std::distance(Callee->arg_begin(), |
| Function::arg_iterator(Arg)); |
| |
| // Look at all call sites of the function. At this pointer we know we only |
| // have direct callees. |
| for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end(); |
| UI != E; ++UI) { |
| CallSite CS(*UI); |
| assert(CS && "Should only have direct calls!"); |
| |
| if (!CS.getArgument(ArgNo)->isDereferenceablePointer()) |
| return false; |
| } |
| return true; |
| } |
| |
| /// Returns true if Prefix is a prefix of longer. That means, Longer has a size |
| /// that is greater than or equal to the size of prefix, and each of the |
| /// elements in Prefix is the same as the corresponding elements in Longer. |
| /// |
| /// This means it also returns true when Prefix and Longer are equal! |
| static bool IsPrefix(const ArgPromotion::IndicesVector &Prefix, |
| const ArgPromotion::IndicesVector &Longer) { |
| if (Prefix.size() > Longer.size()) |
| return false; |
| for (unsigned i = 0, e = Prefix.size(); i != e; ++i) |
| if (Prefix[i] != Longer[i]) |
| return false; |
| return true; |
| } |
| |
| |
| /// Checks if Indices, or a prefix of Indices, is in Set. |
| static bool PrefixIn(const ArgPromotion::IndicesVector &Indices, |
| std::set<ArgPromotion::IndicesVector> &Set) { |
| std::set<ArgPromotion::IndicesVector>::iterator Low; |
| Low = Set.upper_bound(Indices); |
| if (Low != Set.begin()) |
| Low--; |
| // Low is now the last element smaller than or equal to Indices. This means |
| // it points to a prefix of Indices (possibly Indices itself), if such |
| // prefix exists. |
| // |
| // This load is safe if any prefix of its operands is safe to load. |
| return Low != Set.end() && IsPrefix(*Low, Indices); |
| } |
| |
| /// Mark the given indices (ToMark) as safe in the given set of indices |
| /// (Safe). Marking safe usually means adding ToMark to Safe. However, if there |
| /// is already a prefix of Indices in Safe, Indices are implicitely marked safe |
| /// already. Furthermore, any indices that Indices is itself a prefix of, are |
| /// removed from Safe (since they are implicitely safe because of Indices now). |
| static void MarkIndicesSafe(const ArgPromotion::IndicesVector &ToMark, |
| std::set<ArgPromotion::IndicesVector> &Safe) { |
| std::set<ArgPromotion::IndicesVector>::iterator Low; |
| Low = Safe.upper_bound(ToMark); |
| // Guard against the case where Safe is empty |
| if (Low != Safe.begin()) |
| Low--; |
| // Low is now the last element smaller than or equal to Indices. This |
| // means it points to a prefix of Indices (possibly Indices itself), if |
| // such prefix exists. |
| if (Low != Safe.end()) { |
| if (IsPrefix(*Low, ToMark)) |
| // If there is already a prefix of these indices (or exactly these |
| // indices) marked a safe, don't bother adding these indices |
| return; |
| |
| // Increment Low, so we can use it as a "insert before" hint |
| ++Low; |
| } |
| // Insert |
| Low = Safe.insert(Low, ToMark); |
| ++Low; |
| // If there we're a prefix of longer index list(s), remove those |
| std::set<ArgPromotion::IndicesVector>::iterator End = Safe.end(); |
| while (Low != End && IsPrefix(ToMark, *Low)) { |
| std::set<ArgPromotion::IndicesVector>::iterator Remove = Low; |
| ++Low; |
| Safe.erase(Remove); |
| } |
| } |
| |
| /// isSafeToPromoteArgument - As you might guess from the name of this method, |
| /// it checks to see if it is both safe and useful to promote the argument. |
| /// This method limits promotion of aggregates to only promote up to three |
| /// elements of the aggregate in order to avoid exploding the number of |
| /// arguments passed in. |
| bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const { |
| typedef std::set<IndicesVector> GEPIndicesSet; |
| |
| // Quick exit for unused arguments |
| if (Arg->use_empty()) |
| return true; |
| |
| // We can only promote this argument if all of the uses are loads, or are GEP |
| // instructions (with constant indices) that are subsequently loaded. |
| // |
| // Promoting the argument causes it to be loaded in the caller |
| // unconditionally. This is only safe if we can prove that either the load |
| // would have happened in the callee anyway (ie, there is a load in the entry |
| // block) or the pointer passed in at every call site is guaranteed to be |
| // valid. |
| // In the former case, invalid loads can happen, but would have happened |
| // anyway, in the latter case, invalid loads won't happen. This prevents us |
| // from introducing an invalid load that wouldn't have happened in the |
| // original code. |
| // |
| // This set will contain all sets of indices that are loaded in the entry |
| // block, and thus are safe to unconditionally load in the caller. |
| GEPIndicesSet SafeToUnconditionallyLoad; |
| |
| // This set contains all the sets of indices that we are planning to promote. |
| // This makes it possible to limit the number of arguments added. |
| GEPIndicesSet ToPromote; |
| |
| // If the pointer is always valid, any load with first index 0 is valid. |
| if (isByVal || AllCallersPassInValidPointerForArgument(Arg)) |
| SafeToUnconditionallyLoad.insert(IndicesVector(1, 0)); |
| |
| // First, iterate the entry block and mark loads of (geps of) arguments as |
| // safe. |
| BasicBlock *EntryBlock = Arg->getParent()->begin(); |
| // Declare this here so we can reuse it |
| IndicesVector Indices; |
| for (BasicBlock::iterator I = EntryBlock->begin(), E = EntryBlock->end(); |
| I != E; ++I) |
| if (LoadInst *LI = dyn_cast<LoadInst>(I)) { |
| Value *V = LI->getPointerOperand(); |
| if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) { |
| V = GEP->getPointerOperand(); |
| if (V == Arg) { |
| // This load actually loads (part of) Arg? Check the indices then. |
| Indices.reserve(GEP->getNumIndices()); |
| for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end(); |
| II != IE; ++II) |
| if (ConstantInt *CI = dyn_cast<ConstantInt>(*II)) |
| Indices.push_back(CI->getSExtValue()); |
| else |
| // We found a non-constant GEP index for this argument? Bail out |
| // right away, can't promote this argument at all. |
| return false; |
| |
| // Indices checked out, mark them as safe |
| MarkIndicesSafe(Indices, SafeToUnconditionallyLoad); |
| Indices.clear(); |
| } |
| } else if (V == Arg) { |
| // Direct loads are equivalent to a GEP with a single 0 index. |
| MarkIndicesSafe(IndicesVector(1, 0), SafeToUnconditionallyLoad); |
| } |
| } |
| |
| // Now, iterate all uses of the argument to see if there are any uses that are |
| // not (GEP+)loads, or any (GEP+)loads that are not safe to promote. |
| SmallVector<LoadInst*, 16> Loads; |
| IndicesVector Operands; |
| for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end(); |
| UI != E; ++UI) { |
| User *U = *UI; |
| Operands.clear(); |
| if (LoadInst *LI = dyn_cast<LoadInst>(U)) { |
| // Don't hack volatile/atomic loads |
| if (!LI->isSimple()) return false; |
| Loads.push_back(LI); |
| // Direct loads are equivalent to a GEP with a zero index and then a load. |
| Operands.push_back(0); |
| } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { |
| if (GEP->use_empty()) { |
| // Dead GEP's cause trouble later. Just remove them if we run into |
| // them. |
| getAnalysis<AliasAnalysis>().deleteValue(GEP); |
| GEP->eraseFromParent(); |
| // TODO: This runs the above loop over and over again for dead GEPs |
| // Couldn't we just do increment the UI iterator earlier and erase the |
| // use? |
| return isSafeToPromoteArgument(Arg, isByVal); |
| } |
| |
| // Ensure that all of the indices are constants. |
| for (User::op_iterator i = GEP->idx_begin(), e = GEP->idx_end(); |
| i != e; ++i) |
| if (ConstantInt *C = dyn_cast<ConstantInt>(*i)) |
| Operands.push_back(C->getSExtValue()); |
| else |
| return false; // Not a constant operand GEP! |
| |
| // Ensure that the only users of the GEP are load instructions. |
| for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end(); |
| UI != E; ++UI) |
| if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) { |
| // Don't hack volatile/atomic loads |
| if (!LI->isSimple()) return false; |
| Loads.push_back(LI); |
| } else { |
| // Other uses than load? |
| return false; |
| } |
| } else { |
| return false; // Not a load or a GEP. |
| } |
| |
| // Now, see if it is safe to promote this load / loads of this GEP. Loading |
| // is safe if Operands, or a prefix of Operands, is marked as safe. |
| if (!PrefixIn(Operands, SafeToUnconditionallyLoad)) |
| return false; |
| |
| // See if we are already promoting a load with these indices. If not, check |
| // to make sure that we aren't promoting too many elements. If so, nothing |
| // to do. |
| if (ToPromote.find(Operands) == ToPromote.end()) { |
| if (maxElements > 0 && ToPromote.size() == maxElements) { |
| DEBUG(dbgs() << "argpromotion not promoting argument '" |
| << Arg->getName() << "' because it would require adding more " |
| << "than " << maxElements << " arguments to the function.\n"); |
| // We limit aggregate promotion to only promoting up to a fixed number |
| // of elements of the aggregate. |
| return false; |
| } |
| ToPromote.insert(Operands); |
| } |
| } |
| |
| if (Loads.empty()) return true; // No users, this is a dead argument. |
| |
| // Okay, now we know that the argument is only used by load instructions and |
| // it is safe to unconditionally perform all of them. Use alias analysis to |
| // check to see if the pointer is guaranteed to not be modified from entry of |
| // the function to each of the load instructions. |
| |
| // Because there could be several/many load instructions, remember which |
| // blocks we know to be transparent to the load. |
| SmallPtrSet<BasicBlock*, 16> TranspBlocks; |
| |
| AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); |
| |
| for (unsigned i = 0, e = Loads.size(); i != e; ++i) { |
| // Check to see if the load is invalidated from the start of the block to |
| // the load itself. |
| LoadInst *Load = Loads[i]; |
| BasicBlock *BB = Load->getParent(); |
| |
| AliasAnalysis::Location Loc = AA.getLocation(Load); |
| if (AA.canInstructionRangeModify(BB->front(), *Load, Loc)) |
| return false; // Pointer is invalidated! |
| |
| // Now check every path from the entry block to the load for transparency. |
| // To do this, we perform a depth first search on the inverse CFG from the |
| // loading block. |
| for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) { |
| BasicBlock *P = *PI; |
| for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> > |
| I = idf_ext_begin(P, TranspBlocks), |
| E = idf_ext_end(P, TranspBlocks); I != E; ++I) |
| if (AA.canBasicBlockModify(**I, Loc)) |
| return false; |
| } |
| } |
| |
| // If the path from the entry of the function to each load is free of |
| // instructions that potentially invalidate the load, we can make the |
| // transformation! |
| return true; |
| } |
| |
| /// DoPromotion - This method actually performs the promotion of the specified |
| /// arguments, and returns the new function. At this point, we know that it's |
| /// safe to do so. |
| CallGraphNode *ArgPromotion::DoPromotion(Function *F, |
| SmallPtrSet<Argument*, 8> &ArgsToPromote, |
| SmallPtrSet<Argument*, 8> &ByValArgsToTransform) { |
| |
| // Start by computing a new prototype for the function, which is the same as |
| // the old function, but has modified arguments. |
| FunctionType *FTy = F->getFunctionType(); |
| std::vector<Type*> Params; |
| |
| typedef std::set<IndicesVector> ScalarizeTable; |
| |
| // ScalarizedElements - If we are promoting a pointer that has elements |
| // accessed out of it, keep track of which elements are accessed so that we |
| // can add one argument for each. |
| // |
| // Arguments that are directly loaded will have a zero element value here, to |
| // handle cases where there are both a direct load and GEP accesses. |
| // |
| std::map<Argument*, ScalarizeTable> ScalarizedElements; |
| |
| // OriginalLoads - Keep track of a representative load instruction from the |
| // original function so that we can tell the alias analysis implementation |
| // what the new GEP/Load instructions we are inserting look like. |
| std::map<IndicesVector, LoadInst*> OriginalLoads; |
| |
| // Attributes - Keep track of the parameter attributes for the arguments |
| // that we are *not* promoting. For the ones that we do promote, the parameter |
| // attributes are lost |
| SmallVector<AttributeWithIndex, 8> AttributesVec; |
| const AttrListPtr &PAL = F->getAttributes(); |
| |
| // Add any return attributes. |
| if (Attributes attrs = PAL.getRetAttributes()) |
| AttributesVec.push_back(AttributeWithIndex::get(0, attrs)); |
| |
| // First, determine the new argument list |
| unsigned ArgIndex = 1; |
| for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; |
| ++I, ++ArgIndex) { |
| if (ByValArgsToTransform.count(I)) { |
| // Simple byval argument? Just add all the struct element types. |
| Type *AgTy = cast<PointerType>(I->getType())->getElementType(); |
| StructType *STy = cast<StructType>(AgTy); |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) |
| Params.push_back(STy->getElementType(i)); |
| ++NumByValArgsPromoted; |
| } else if (!ArgsToPromote.count(I)) { |
| // Unchanged argument |
| Params.push_back(I->getType()); |
| if (Attributes attrs = PAL.getParamAttributes(ArgIndex)) |
| AttributesVec.push_back(AttributeWithIndex::get(Params.size(), attrs)); |
| } else if (I->use_empty()) { |
| // Dead argument (which are always marked as promotable) |
| ++NumArgumentsDead; |
| } else { |
| // Okay, this is being promoted. This means that the only uses are loads |
| // or GEPs which are only used by loads |
| |
| // In this table, we will track which indices are loaded from the argument |
| // (where direct loads are tracked as no indices). |
| ScalarizeTable &ArgIndices = ScalarizedElements[I]; |
| for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E; |
| ++UI) { |
| Instruction *User = cast<Instruction>(*UI); |
| assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User)); |
| IndicesVector Indices; |
| Indices.reserve(User->getNumOperands() - 1); |
| // Since loads will only have a single operand, and GEPs only a single |
| // non-index operand, this will record direct loads without any indices, |
| // and gep+loads with the GEP indices. |
| for (User::op_iterator II = User->op_begin() + 1, IE = User->op_end(); |
| II != IE; ++II) |
| Indices.push_back(cast<ConstantInt>(*II)->getSExtValue()); |
| // GEPs with a single 0 index can be merged with direct loads |
| if (Indices.size() == 1 && Indices.front() == 0) |
| Indices.clear(); |
| ArgIndices.insert(Indices); |
| LoadInst *OrigLoad; |
| if (LoadInst *L = dyn_cast<LoadInst>(User)) |
| OrigLoad = L; |
| else |
| // Take any load, we will use it only to update Alias Analysis |
| OrigLoad = cast<LoadInst>(User->use_back()); |
| OriginalLoads[Indices] = OrigLoad; |
| } |
| |
| // Add a parameter to the function for each element passed in. |
| for (ScalarizeTable::iterator SI = ArgIndices.begin(), |
| E = ArgIndices.end(); SI != E; ++SI) { |
| // not allowed to dereference ->begin() if size() is 0 |
| Params.push_back(GetElementPtrInst::getIndexedType(I->getType(), *SI)); |
| assert(Params.back()); |
| } |
| |
| if (ArgIndices.size() == 1 && ArgIndices.begin()->empty()) |
| ++NumArgumentsPromoted; |
| else |
| ++NumAggregatesPromoted; |
| } |
| } |
| |
| // Add any function attributes. |
| if (Attributes attrs = PAL.getFnAttributes()) |
| AttributesVec.push_back(AttributeWithIndex::get(~0, attrs)); |
| |
| Type *RetTy = FTy->getReturnType(); |
| |
| // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which |
| // have zero fixed arguments. |
| bool ExtraArgHack = false; |
| if (Params.empty() && FTy->isVarArg()) { |
| ExtraArgHack = true; |
| Params.push_back(Type::getInt32Ty(F->getContext())); |
| } |
| |
| // Construct the new function type using the new arguments. |
| FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg()); |
| |
| // Create the new function body and insert it into the module. |
| Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName()); |
| NF->copyAttributesFrom(F); |
| |
| |
| DEBUG(dbgs() << "ARG PROMOTION: Promoting to:" << *NF << "\n" |
| << "From: " << *F); |
| |
| // Recompute the parameter attributes list based on the new arguments for |
| // the function. |
| NF->setAttributes(AttrListPtr::get(AttributesVec.begin(), |
| AttributesVec.end())); |
| AttributesVec.clear(); |
| |
| F->getParent()->getFunctionList().insert(F, NF); |
| NF->takeName(F); |
| |
| // Get the alias analysis information that we need to update to reflect our |
| // changes. |
| AliasAnalysis &AA = getAnalysis<AliasAnalysis>(); |
| |
| // Get the callgraph information that we need to update to reflect our |
| // changes. |
| CallGraph &CG = getAnalysis<CallGraph>(); |
| |
| // Get a new callgraph node for NF. |
| CallGraphNode *NF_CGN = CG.getOrInsertFunction(NF); |
| |
| // Loop over all of the callers of the function, transforming the call sites |
| // to pass in the loaded pointers. |
| // |
| SmallVector<Value*, 16> Args; |
| while (!F->use_empty()) { |
| CallSite CS(F->use_back()); |
| assert(CS.getCalledFunction() == F); |
| Instruction *Call = CS.getInstruction(); |
| const AttrListPtr &CallPAL = CS.getAttributes(); |
| |
| // Add any return attributes. |
| if (Attributes attrs = CallPAL.getRetAttributes()) |
| AttributesVec.push_back(AttributeWithIndex::get(0, attrs)); |
| |
| // Loop over the operands, inserting GEP and loads in the caller as |
| // appropriate. |
| CallSite::arg_iterator AI = CS.arg_begin(); |
| ArgIndex = 1; |
| for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); |
| I != E; ++I, ++AI, ++ArgIndex) |
| if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) { |
| Args.push_back(*AI); // Unmodified argument |
| |
| if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex)) |
| AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs)); |
| |
| } else if (ByValArgsToTransform.count(I)) { |
| // Emit a GEP and load for each element of the struct. |
| Type *AgTy = cast<PointerType>(I->getType())->getElementType(); |
| StructType *STy = cast<StructType>(AgTy); |
| Value *Idxs[2] = { |
| ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 }; |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { |
| Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i); |
| Value *Idx = GetElementPtrInst::Create(*AI, Idxs, |
| (*AI)->getName()+"."+utostr(i), |
| Call); |
| // TODO: Tell AA about the new values? |
| Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call)); |
| } |
| } else if (!I->use_empty()) { |
| // Non-dead argument: insert GEPs and loads as appropriate. |
| ScalarizeTable &ArgIndices = ScalarizedElements[I]; |
| // Store the Value* version of the indices in here, but declare it now |
| // for reuse. |
| std::vector<Value*> Ops; |
| for (ScalarizeTable::iterator SI = ArgIndices.begin(), |
| E = ArgIndices.end(); SI != E; ++SI) { |
| Value *V = *AI; |
| LoadInst *OrigLoad = OriginalLoads[*SI]; |
| if (!SI->empty()) { |
| Ops.reserve(SI->size()); |
| Type *ElTy = V->getType(); |
| for (IndicesVector::const_iterator II = SI->begin(), |
| IE = SI->end(); II != IE; ++II) { |
| // Use i32 to index structs, and i64 for others (pointers/arrays). |
| // This satisfies GEP constraints. |
| Type *IdxTy = (ElTy->isStructTy() ? |
| Type::getInt32Ty(F->getContext()) : |
| Type::getInt64Ty(F->getContext())); |
| Ops.push_back(ConstantInt::get(IdxTy, *II)); |
| // Keep track of the type we're currently indexing. |
| ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(*II); |
| } |
| // And create a GEP to extract those indices. |
| V = GetElementPtrInst::Create(V, Ops, V->getName()+".idx", Call); |
| Ops.clear(); |
| AA.copyValue(OrigLoad->getOperand(0), V); |
| } |
| // Since we're replacing a load make sure we take the alignment |
| // of the previous load. |
| LoadInst *newLoad = new LoadInst(V, V->getName()+".val", Call); |
| newLoad->setAlignment(OrigLoad->getAlignment()); |
| // Transfer the TBAA info too. |
| newLoad->setMetadata(LLVMContext::MD_tbaa, |
| OrigLoad->getMetadata(LLVMContext::MD_tbaa)); |
| Args.push_back(newLoad); |
| AA.copyValue(OrigLoad, Args.back()); |
| } |
| } |
| |
| if (ExtraArgHack) |
| Args.push_back(Constant::getNullValue(Type::getInt32Ty(F->getContext()))); |
| |
| // Push any varargs arguments on the list. |
| for (; AI != CS.arg_end(); ++AI, ++ArgIndex) { |
| Args.push_back(*AI); |
| if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex)) |
| AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs)); |
| } |
| |
| // Add any function attributes. |
| if (Attributes attrs = CallPAL.getFnAttributes()) |
| AttributesVec.push_back(AttributeWithIndex::get(~0, attrs)); |
| |
| Instruction *New; |
| if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) { |
| New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(), |
| Args, "", Call); |
| cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv()); |
| cast<InvokeInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(), |
| AttributesVec.end())); |
| } else { |
| New = CallInst::Create(NF, Args, "", Call); |
| cast<CallInst>(New)->setCallingConv(CS.getCallingConv()); |
| cast<CallInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(), |
| AttributesVec.end())); |
| if (cast<CallInst>(Call)->isTailCall()) |
| cast<CallInst>(New)->setTailCall(); |
| } |
| Args.clear(); |
| AttributesVec.clear(); |
| |
| // Update the alias analysis implementation to know that we are replacing |
| // the old call with a new one. |
| AA.replaceWithNewValue(Call, New); |
| |
| // Update the callgraph to know that the callsite has been transformed. |
| CallGraphNode *CalleeNode = CG[Call->getParent()->getParent()]; |
| CalleeNode->replaceCallEdge(Call, New, NF_CGN); |
| |
| if (!Call->use_empty()) { |
| Call->replaceAllUsesWith(New); |
| New->takeName(Call); |
| } |
| |
| // Finally, remove the old call from the program, reducing the use-count of |
| // F. |
| Call->eraseFromParent(); |
| } |
| |
| // Since we have now created the new function, splice the body of the old |
| // function right into the new function, leaving the old rotting hulk of the |
| // function empty. |
| NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList()); |
| |
| // Loop over the argument list, transferring uses of the old arguments over to |
| // the new arguments, also transferring over the names as well. |
| // |
| for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(), |
| I2 = NF->arg_begin(); I != E; ++I) { |
| if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) { |
| // If this is an unmodified argument, move the name and users over to the |
| // new version. |
| I->replaceAllUsesWith(I2); |
| I2->takeName(I); |
| AA.replaceWithNewValue(I, I2); |
| ++I2; |
| continue; |
| } |
| |
| if (ByValArgsToTransform.count(I)) { |
| // In the callee, we create an alloca, and store each of the new incoming |
| // arguments into the alloca. |
| Instruction *InsertPt = NF->begin()->begin(); |
| |
| // Just add all the struct element types. |
| Type *AgTy = cast<PointerType>(I->getType())->getElementType(); |
| Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt); |
| StructType *STy = cast<StructType>(AgTy); |
| Value *Idxs[2] = { |
| ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 }; |
| |
| for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) { |
| Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i); |
| Value *Idx = |
| GetElementPtrInst::Create(TheAlloca, Idxs, |
| TheAlloca->getName()+"."+Twine(i), |
| InsertPt); |
| I2->setName(I->getName()+"."+Twine(i)); |
| new StoreInst(I2++, Idx, InsertPt); |
| } |
| |
| // Anything that used the arg should now use the alloca. |
| I->replaceAllUsesWith(TheAlloca); |
| TheAlloca->takeName(I); |
| AA.replaceWithNewValue(I, TheAlloca); |
| continue; |
| } |
| |
| if (I->use_empty()) { |
| AA.deleteValue(I); |
| continue; |
| } |
| |
| // Otherwise, if we promoted this argument, then all users are load |
| // instructions (or GEPs with only load users), and all loads should be |
| // using the new argument that we added. |
| ScalarizeTable &ArgIndices = ScalarizedElements[I]; |
| |
| while (!I->use_empty()) { |
| if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) { |
| assert(ArgIndices.begin()->empty() && |
| "Load element should sort to front!"); |
| I2->setName(I->getName()+".val"); |
| LI->replaceAllUsesWith(I2); |
| AA.replaceWithNewValue(LI, I2); |
| LI->eraseFromParent(); |
| DEBUG(dbgs() << "*** Promoted load of argument '" << I->getName() |
| << "' in function '" << F->getName() << "'\n"); |
| } else { |
| GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back()); |
| IndicesVector Operands; |
| Operands.reserve(GEP->getNumIndices()); |
| for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end(); |
| II != IE; ++II) |
| Operands.push_back(cast<ConstantInt>(*II)->getSExtValue()); |
| |
| // GEPs with a single 0 index can be merged with direct loads |
| if (Operands.size() == 1 && Operands.front() == 0) |
| Operands.clear(); |
| |
| Function::arg_iterator TheArg = I2; |
| for (ScalarizeTable::iterator It = ArgIndices.begin(); |
| *It != Operands; ++It, ++TheArg) { |
| assert(It != ArgIndices.end() && "GEP not handled??"); |
| } |
| |
| std::string NewName = I->getName(); |
| for (unsigned i = 0, e = Operands.size(); i != e; ++i) { |
| NewName += "." + utostr(Operands[i]); |
| } |
| NewName += ".val"; |
| TheArg->setName(NewName); |
| |
| DEBUG(dbgs() << "*** Promoted agg argument '" << TheArg->getName() |
| << "' of function '" << NF->getName() << "'\n"); |
| |
| // All of the uses must be load instructions. Replace them all with |
| // the argument specified by ArgNo. |
| while (!GEP->use_empty()) { |
| LoadInst *L = cast<LoadInst>(GEP->use_back()); |
| L->replaceAllUsesWith(TheArg); |
| AA.replaceWithNewValue(L, TheArg); |
| L->eraseFromParent(); |
| } |
| AA.deleteValue(GEP); |
| GEP->eraseFromParent(); |
| } |
| } |
| |
| // Increment I2 past all of the arguments added for this promoted pointer. |
| for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i) |
| ++I2; |
| } |
| |
| // Notify the alias analysis implementation that we inserted a new argument. |
| if (ExtraArgHack) |
| AA.copyValue(Constant::getNullValue(Type::getInt32Ty(F->getContext())), |
| NF->arg_begin()); |
| |
| |
| // Tell the alias analysis that the old function is about to disappear. |
| AA.replaceWithNewValue(F, NF); |
| |
| |
| NF_CGN->stealCalledFunctionsFrom(CG[F]); |
| |
| // Now that the old function is dead, delete it. If there is a dangling |
| // reference to the CallgraphNode, just leave the dead function around for |
| // someone else to nuke. |
| CallGraphNode *CGN = CG[F]; |
| if (CGN->getNumReferences() == 0) |
| delete CG.removeFunctionFromModule(CGN); |
| else |
| F->setLinkage(Function::ExternalLinkage); |
| |
| return NF_CGN; |
| } |
