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//===-- ArgumentPromotion.cpp - Promote by-reference arguments ------------===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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// This pass promotes "by reference" arguments to be "by value" arguments. In
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// practice, this means looking for internal functions that have pointer
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// arguments. If it can prove, through the use of alias analysis, that an
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// argument is *only* loaded, then it can pass the value into the function
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// instead of the address of the value. This can cause recursive simplification
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// of code and lead to the elimination of allocas (especially in C++ template
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// code like the STL).
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// This pass also handles aggregate arguments that are passed into a function,
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// scalarizing them if the elements of the aggregate are only loaded. Note that
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// by default it refuses to scalarize aggregates which would require passing in
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// more than three operands to the function, because passing thousands of
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// operands for a large array or structure is unprofitable! This limit can be
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// configured or disabled, however.
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// Note that this transformation could also be done for arguments that are only
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// stored to (returning the value instead), but does not currently. This case
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// would be best handled when and if LLVM begins supporting multiple return
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// values from functions.
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "argpromotion"
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#include "llvm/Transforms/IPO.h"
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#include "llvm/Constants.h"
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#include "llvm/DerivedTypes.h"
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#include "llvm/Module.h"
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#include "llvm/CallGraphSCCPass.h"
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#include "llvm/Instructions.h"
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#include "llvm/LLVMContext.h"
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#include "llvm/Analysis/AliasAnalysis.h"
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#include "llvm/Analysis/CallGraph.h"
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#include "llvm/Target/TargetData.h"
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#include "llvm/Support/CallSite.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/StringExtras.h"
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STATISTIC(NumArgumentsPromoted , "Number of pointer arguments promoted");
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STATISTIC(NumAggregatesPromoted, "Number of aggregate arguments promoted");
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STATISTIC(NumByValArgsPromoted , "Number of byval arguments promoted");
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STATISTIC(NumArgumentsDead , "Number of dead pointer args eliminated");
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/// ArgPromotion - The 'by reference' to 'by value' argument promotion pass.
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struct ArgPromotion : public CallGraphSCCPass {
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virtual void getAnalysisUsage(AnalysisUsage &AU) const {
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AU.addRequired<AliasAnalysis>();
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CallGraphSCCPass::getAnalysisUsage(AU);
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virtual bool runOnSCC(std::vector<CallGraphNode *> &SCC);
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static char ID; // Pass identification, replacement for typeid
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explicit ArgPromotion(unsigned maxElements = 3)
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: CallGraphSCCPass(&ID), maxElements(maxElements) {}
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/// A vector used to hold the indices of a single GEP instruction
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typedef std::vector<uint64_t> IndicesVector;
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CallGraphNode *PromoteArguments(CallGraphNode *CGN);
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bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const;
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CallGraphNode *DoPromotion(Function *F,
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SmallPtrSet<Argument*, 8> &ArgsToPromote,
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SmallPtrSet<Argument*, 8> &ByValArgsToTransform);
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/// The maximum number of elements to expand, or 0 for unlimited.
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char ArgPromotion::ID = 0;
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static RegisterPass<ArgPromotion>
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X("argpromotion", "Promote 'by reference' arguments to scalars");
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Pass *llvm::createArgumentPromotionPass(unsigned maxElements) {
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return new ArgPromotion(maxElements);
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bool ArgPromotion::runOnSCC(std::vector<CallGraphNode *> &SCC) {
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bool Changed = false, LocalChange;
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do { // Iterate until we stop promoting from this SCC.
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// Attempt to promote arguments from all functions in this SCC.
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for (unsigned i = 0, e = SCC.size(); i != e; ++i)
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if (CallGraphNode *CGN = PromoteArguments(SCC[i])) {
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Changed |= LocalChange; // Remember that we changed something.
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} while (LocalChange);
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/// PromoteArguments - This method checks the specified function to see if there
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/// are any promotable arguments and if it is safe to promote the function (for
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/// example, all callers are direct). If safe to promote some arguments, it
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/// calls the DoPromotion method.
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CallGraphNode *ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
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Function *F = CGN->getFunction();
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// Make sure that it is local to this module.
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if (!F || !F->hasLocalLinkage()) return 0;
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// First check: see if there are any pointer arguments! If not, quick exit.
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SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs;
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for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
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I != E; ++I, ++ArgNo)
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if (I->getType()->isPointerTy())
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PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo));
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if (PointerArgs.empty()) return 0;
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// Second check: make sure that all callers are direct callers. We can't
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// transform functions that have indirect callers.
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if (F->hasAddressTaken())
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// Check to see which arguments are promotable. If an argument is promotable,
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// add it to ArgsToPromote.
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SmallPtrSet<Argument*, 8> ArgsToPromote;
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SmallPtrSet<Argument*, 8> ByValArgsToTransform;
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for (unsigned i = 0; i != PointerArgs.size(); ++i) {
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bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, Attribute::ByVal);
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// If this is a byval argument, and if the aggregate type is small, just
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// pass the elements, which is always safe.
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Argument *PtrArg = PointerArgs[i].first;
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const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
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if (const StructType *STy = dyn_cast<StructType>(AgTy)) {
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if (maxElements > 0 && STy->getNumElements() > maxElements) {
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DEBUG(dbgs() << "argpromotion disable promoting argument '"
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<< PtrArg->getName() << "' because it would require adding more"
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<< " than " << maxElements << " arguments to the function.\n");
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// If all the elements are single-value types, we can promote it.
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bool AllSimple = true;
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for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
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if (!STy->getElementType(i)->isSingleValueType()) {
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// Safe to transform, don't even bother trying to "promote" it.
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// Passing the elements as a scalar will allow scalarrepl to hack on
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// the new alloca we introduce.
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ByValArgsToTransform.insert(PtrArg);
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// Otherwise, see if we can promote the pointer to its value.
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if (isSafeToPromoteArgument(PtrArg, isByVal))
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ArgsToPromote.insert(PtrArg);
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// No promotable pointer arguments.
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if (ArgsToPromote.empty() && ByValArgsToTransform.empty())
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return DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
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/// IsAlwaysValidPointer - Return true if the specified pointer is always legal
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static bool IsAlwaysValidPointer(Value *V) {
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if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
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if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V))
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return IsAlwaysValidPointer(GEP->getOperand(0));
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if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
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if (CE->getOpcode() == Instruction::GetElementPtr)
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return IsAlwaysValidPointer(CE->getOperand(0));
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/// AllCalleesPassInValidPointerForArgument - Return true if we can prove that
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/// all callees pass in a valid pointer for the specified function argument.
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static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
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Function *Callee = Arg->getParent();
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unsigned ArgNo = std::distance(Callee->arg_begin(),
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Function::arg_iterator(Arg));
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// Look at all call sites of the function. At this pointer we know we only
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// have direct callees.
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for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
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CallSite CS = CallSite::get(*UI);
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assert(CS.getInstruction() && "Should only have direct calls!");
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if (!IsAlwaysValidPointer(CS.getArgument(ArgNo)))
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/// Returns true if Prefix is a prefix of longer. That means, Longer has a size
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/// that is greater than or equal to the size of prefix, and each of the
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/// elements in Prefix is the same as the corresponding elements in Longer.
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/// This means it also returns true when Prefix and Longer are equal!
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static bool IsPrefix(const ArgPromotion::IndicesVector &Prefix,
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const ArgPromotion::IndicesVector &Longer) {
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if (Prefix.size() > Longer.size())
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for (unsigned i = 0, e = Prefix.size(); i != e; ++i)
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if (Prefix[i] != Longer[i])
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/// Checks if Indices, or a prefix of Indices, is in Set.
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static bool PrefixIn(const ArgPromotion::IndicesVector &Indices,
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std::set<ArgPromotion::IndicesVector> &Set) {
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std::set<ArgPromotion::IndicesVector>::iterator Low;
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Low = Set.upper_bound(Indices);
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if (Low != Set.begin())
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// Low is now the last element smaller than or equal to Indices. This means
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// it points to a prefix of Indices (possibly Indices itself), if such
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// This load is safe if any prefix of its operands is safe to load.
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return Low != Set.end() && IsPrefix(*Low, Indices);
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/// Mark the given indices (ToMark) as safe in the given set of indices
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/// (Safe). Marking safe usually means adding ToMark to Safe. However, if there
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/// is already a prefix of Indices in Safe, Indices are implicitely marked safe
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/// already. Furthermore, any indices that Indices is itself a prefix of, are
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/// removed from Safe (since they are implicitely safe because of Indices now).
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static void MarkIndicesSafe(const ArgPromotion::IndicesVector &ToMark,
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std::set<ArgPromotion::IndicesVector> &Safe) {
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std::set<ArgPromotion::IndicesVector>::iterator Low;
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Low = Safe.upper_bound(ToMark);
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// Guard against the case where Safe is empty
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if (Low != Safe.begin())
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// Low is now the last element smaller than or equal to Indices. This
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// means it points to a prefix of Indices (possibly Indices itself), if
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// such prefix exists.
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if (Low != Safe.end()) {
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if (IsPrefix(*Low, ToMark))
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// If there is already a prefix of these indices (or exactly these
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// indices) marked a safe, don't bother adding these indices
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// Increment Low, so we can use it as a "insert before" hint
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Low = Safe.insert(Low, ToMark);
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// If there we're a prefix of longer index list(s), remove those
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std::set<ArgPromotion::IndicesVector>::iterator End = Safe.end();
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while (Low != End && IsPrefix(ToMark, *Low)) {
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std::set<ArgPromotion::IndicesVector>::iterator Remove = Low;
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/// isSafeToPromoteArgument - As you might guess from the name of this method,
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/// it checks to see if it is both safe and useful to promote the argument.
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/// This method limits promotion of aggregates to only promote up to three
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/// elements of the aggregate in order to avoid exploding the number of
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/// arguments passed in.
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bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
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typedef std::set<IndicesVector> GEPIndicesSet;
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// Quick exit for unused arguments
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if (Arg->use_empty())
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// We can only promote this argument if all of the uses are loads, or are GEP
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// instructions (with constant indices) that are subsequently loaded.
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// Promoting the argument causes it to be loaded in the caller
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// unconditionally. This is only safe if we can prove that either the load
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// would have happened in the callee anyway (ie, there is a load in the entry
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// block) or the pointer passed in at every call site is guaranteed to be
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// In the former case, invalid loads can happen, but would have happened
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// anyway, in the latter case, invalid loads won't happen. This prevents us
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// from introducing an invalid load that wouldn't have happened in the
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// This set will contain all sets of indices that are loaded in the entry
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// block, and thus are safe to unconditionally load in the caller.
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GEPIndicesSet SafeToUnconditionallyLoad;
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// This set contains all the sets of indices that we are planning to promote.
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// This makes it possible to limit the number of arguments added.
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GEPIndicesSet ToPromote;
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// If the pointer is always valid, any load with first index 0 is valid.
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if (isByVal || AllCalleesPassInValidPointerForArgument(Arg))
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SafeToUnconditionallyLoad.insert(IndicesVector(1, 0));
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// First, iterate the entry block and mark loads of (geps of) arguments as
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BasicBlock *EntryBlock = Arg->getParent()->begin();
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// Declare this here so we can reuse it
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IndicesVector Indices;
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for (BasicBlock::iterator I = EntryBlock->begin(), E = EntryBlock->end();
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if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
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Value *V = LI->getPointerOperand();
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if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
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V = GEP->getPointerOperand();
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// This load actually loads (part of) Arg? Check the indices then.
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Indices.reserve(GEP->getNumIndices());
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for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
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if (ConstantInt *CI = dyn_cast<ConstantInt>(*II))
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Indices.push_back(CI->getSExtValue());
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// We found a non-constant GEP index for this argument? Bail out
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// right away, can't promote this argument at all.
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// Indices checked out, mark them as safe
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MarkIndicesSafe(Indices, SafeToUnconditionallyLoad);
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} else if (V == Arg) {
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// Direct loads are equivalent to a GEP with a single 0 index.
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MarkIndicesSafe(IndicesVector(1, 0), SafeToUnconditionallyLoad);
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// Now, iterate all uses of the argument to see if there are any uses that are
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// not (GEP+)loads, or any (GEP+)loads that are not safe to promote.
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SmallVector<LoadInst*, 16> Loads;
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IndicesVector Operands;
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for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
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if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
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if (LI->isVolatile()) return false; // Don't hack volatile loads
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// Direct loads are equivalent to a GEP with a zero index and then a load.
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Operands.push_back(0);
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} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
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if (GEP->use_empty()) {
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// Dead GEP's cause trouble later. Just remove them if we run into
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getAnalysis<AliasAnalysis>().deleteValue(GEP);
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GEP->eraseFromParent();
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// TODO: This runs the above loop over and over again for dead GEPS
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// Couldn't we just do increment the UI iterator earlier and erase the
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return isSafeToPromoteArgument(Arg, isByVal);
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// Ensure that all of the indices are constants.
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for (User::op_iterator i = GEP->idx_begin(), e = GEP->idx_end();
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if (ConstantInt *C = dyn_cast<ConstantInt>(*i))
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Operands.push_back(C->getSExtValue());
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return false; // Not a constant operand GEP!
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// Ensure that the only users of the GEP are load instructions.
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for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
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if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
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if (LI->isVolatile()) return false; // Don't hack volatile loads
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// Other uses than load?
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return false; // Not a load or a GEP.
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// Now, see if it is safe to promote this load / loads of this GEP. Loading
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// is safe if Operands, or a prefix of Operands, is marked as safe.
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if (!PrefixIn(Operands, SafeToUnconditionallyLoad))
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// See if we are already promoting a load with these indices. If not, check
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// to make sure that we aren't promoting too many elements. If so, nothing
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if (ToPromote.find(Operands) == ToPromote.end()) {
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if (maxElements > 0 && ToPromote.size() == maxElements) {
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DEBUG(dbgs() << "argpromotion not promoting argument '"
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<< Arg->getName() << "' because it would require adding more "
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<< "than " << maxElements << " arguments to the function.\n");
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// We limit aggregate promotion to only promoting up to a fixed number
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// of elements of the aggregate.
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ToPromote.insert(Operands);
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if (Loads.empty()) return true; // No users, this is a dead argument.
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// Okay, now we know that the argument is only used by load instructions and
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// it is safe to unconditionally perform all of them. Use alias analysis to
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// check to see if the pointer is guaranteed to not be modified from entry of
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// the function to each of the load instructions.
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// Because there could be several/many load instructions, remember which
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// blocks we know to be transparent to the load.
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SmallPtrSet<BasicBlock*, 16> TranspBlocks;
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AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
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TargetData *TD = getAnalysisIfAvailable<TargetData>();
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if (!TD) return false; // Without TargetData, assume the worst.
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for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
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// Check to see if the load is invalidated from the start of the block to
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LoadInst *Load = Loads[i];
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BasicBlock *BB = Load->getParent();
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const PointerType *LoadTy =
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cast<PointerType>(Load->getPointerOperand()->getType());
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unsigned LoadSize =(unsigned)TD->getTypeStoreSize(LoadTy->getElementType());
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if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize))
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return false; // Pointer is invalidated!
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// Now check every path from the entry block to the load for transparency.
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// To do this, we perform a depth first search on the inverse CFG from the
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for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
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for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
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I = idf_ext_begin(*PI, TranspBlocks),
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E = idf_ext_end(*PI, TranspBlocks); I != E; ++I)
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if (AA.canBasicBlockModify(**I, Arg, LoadSize))
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// If the path from the entry of the function to each load is free of
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// instructions that potentially invalidate the load, we can make the
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/// DoPromotion - This method actually performs the promotion of the specified
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/// arguments, and returns the new function. At this point, we know that it's
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CallGraphNode *ArgPromotion::DoPromotion(Function *F,
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SmallPtrSet<Argument*, 8> &ArgsToPromote,
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SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
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// Start by computing a new prototype for the function, which is the same as
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// the old function, but has modified arguments.
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const FunctionType *FTy = F->getFunctionType();
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std::vector<const Type*> Params;
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typedef std::set<IndicesVector> ScalarizeTable;
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// ScalarizedElements - If we are promoting a pointer that has elements
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// accessed out of it, keep track of which elements are accessed so that we
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// can add one argument for each.
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// Arguments that are directly loaded will have a zero element value here, to
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// handle cases where there are both a direct load and GEP accesses.
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std::map<Argument*, ScalarizeTable> ScalarizedElements;
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// OriginalLoads - Keep track of a representative load instruction from the
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// original function so that we can tell the alias analysis implementation
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// what the new GEP/Load instructions we are inserting look like.
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std::map<IndicesVector, LoadInst*> OriginalLoads;
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// Attributes - Keep track of the parameter attributes for the arguments
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// that we are *not* promoting. For the ones that we do promote, the parameter
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// attributes are lost
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SmallVector<AttributeWithIndex, 8> AttributesVec;
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const AttrListPtr &PAL = F->getAttributes();
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// Add any return attributes.
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if (Attributes attrs = PAL.getRetAttributes())
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AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
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// First, determine the new argument list
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unsigned ArgIndex = 1;
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for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
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if (ByValArgsToTransform.count(I)) {
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// Simple byval argument? Just add all the struct element types.
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const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
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const StructType *STy = cast<StructType>(AgTy);
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for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
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Params.push_back(STy->getElementType(i));
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++NumByValArgsPromoted;
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} else if (!ArgsToPromote.count(I)) {
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// Unchanged argument
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Params.push_back(I->getType());
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if (Attributes attrs = PAL.getParamAttributes(ArgIndex))
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AttributesVec.push_back(AttributeWithIndex::get(Params.size(), attrs));
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} else if (I->use_empty()) {
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// Dead argument (which are always marked as promotable)
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// Okay, this is being promoted. This means that the only uses are loads
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// or GEPs which are only used by loads
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// In this table, we will track which indices are loaded from the argument
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// (where direct loads are tracked as no indices).
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ScalarizeTable &ArgIndices = ScalarizedElements[I];
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for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
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Instruction *User = cast<Instruction>(*UI);
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assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
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IndicesVector Indices;
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Indices.reserve(User->getNumOperands() - 1);
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// Since loads will only have a single operand, and GEPs only a single
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// non-index operand, this will record direct loads without any indices,
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// and gep+loads with the GEP indices.
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for (User::op_iterator II = User->op_begin() + 1, IE = User->op_end();
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Indices.push_back(cast<ConstantInt>(*II)->getSExtValue());
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// GEPs with a single 0 index can be merged with direct loads
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if (Indices.size() == 1 && Indices.front() == 0)
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ArgIndices.insert(Indices);
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if (LoadInst *L = dyn_cast<LoadInst>(User))
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// Take any load, we will use it only to update Alias Analysis
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OrigLoad = cast<LoadInst>(User->use_back());
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OriginalLoads[Indices] = OrigLoad;
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// Add a parameter to the function for each element passed in.
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for (ScalarizeTable::iterator SI = ArgIndices.begin(),
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E = ArgIndices.end(); SI != E; ++SI) {
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// not allowed to dereference ->begin() if size() is 0
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Params.push_back(GetElementPtrInst::getIndexedType(I->getType(),
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assert(Params.back());
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if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
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++NumArgumentsPromoted;
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++NumAggregatesPromoted;
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// Add any function attributes.
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if (Attributes attrs = PAL.getFnAttributes())
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AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
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const Type *RetTy = FTy->getReturnType();
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// Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
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// have zero fixed arguments.
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bool ExtraArgHack = false;
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if (Params.empty() && FTy->isVarArg()) {
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Params.push_back(Type::getInt32Ty(F->getContext()));
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// Construct the new function type using the new arguments.
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FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
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// Create the new function body and insert it into the module.
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Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
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NF->copyAttributesFrom(F);
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DEBUG(dbgs() << "ARG PROMOTION: Promoting to:" << *NF << "\n"
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// Recompute the parameter attributes list based on the new arguments for
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NF->setAttributes(AttrListPtr::get(AttributesVec.begin(),
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AttributesVec.end()));
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AttributesVec.clear();
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F->getParent()->getFunctionList().insert(F, NF);
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// Get the alias analysis information that we need to update to reflect our
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AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
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// Get the callgraph information that we need to update to reflect our
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CallGraph &CG = getAnalysis<CallGraph>();
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// Get a new callgraph node for NF.
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CallGraphNode *NF_CGN = CG.getOrInsertFunction(NF);
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// Loop over all of the callers of the function, transforming the call sites
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// to pass in the loaded pointers.
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SmallVector<Value*, 16> Args;
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while (!F->use_empty()) {
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CallSite CS = CallSite::get(F->use_back());
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Instruction *Call = CS.getInstruction();
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const AttrListPtr &CallPAL = CS.getAttributes();
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// Add any return attributes.
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if (Attributes attrs = CallPAL.getRetAttributes())
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AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
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// Loop over the operands, inserting GEP and loads in the caller as
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CallSite::arg_iterator AI = CS.arg_begin();
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for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
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I != E; ++I, ++AI, ++ArgIndex)
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if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
640
Args.push_back(*AI); // Unmodified argument
642
if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
643
AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
645
} else if (ByValArgsToTransform.count(I)) {
646
// Emit a GEP and load for each element of the struct.
647
const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
648
const StructType *STy = cast<StructType>(AgTy);
650
ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
651
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
652
Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
653
Value *Idx = GetElementPtrInst::Create(*AI, Idxs, Idxs+2,
654
(*AI)->getName()+"."+utostr(i),
656
// TODO: Tell AA about the new values?
657
Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
659
} else if (!I->use_empty()) {
660
// Non-dead argument: insert GEPs and loads as appropriate.
661
ScalarizeTable &ArgIndices = ScalarizedElements[I];
662
// Store the Value* version of the indices in here, but declare it now
664
std::vector<Value*> Ops;
665
for (ScalarizeTable::iterator SI = ArgIndices.begin(),
666
E = ArgIndices.end(); SI != E; ++SI) {
668
LoadInst *OrigLoad = OriginalLoads[*SI];
670
Ops.reserve(SI->size());
671
const Type *ElTy = V->getType();
672
for (IndicesVector::const_iterator II = SI->begin(),
673
IE = SI->end(); II != IE; ++II) {
674
// Use i32 to index structs, and i64 for others (pointers/arrays).
675
// This satisfies GEP constraints.
676
const Type *IdxTy = (ElTy->isStructTy() ?
677
Type::getInt32Ty(F->getContext()) :
678
Type::getInt64Ty(F->getContext()));
679
Ops.push_back(ConstantInt::get(IdxTy, *II));
680
// Keep track of the type we're currently indexing
681
ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(*II);
683
// And create a GEP to extract those indices
684
V = GetElementPtrInst::Create(V, Ops.begin(), Ops.end(),
685
V->getName()+".idx", Call);
687
AA.copyValue(OrigLoad->getOperand(0), V);
689
Args.push_back(new LoadInst(V, V->getName()+".val", Call));
690
AA.copyValue(OrigLoad, Args.back());
695
Args.push_back(Constant::getNullValue(Type::getInt32Ty(F->getContext())));
697
// Push any varargs arguments on the list
698
for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
700
if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
701
AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
704
// Add any function attributes.
705
if (Attributes attrs = CallPAL.getFnAttributes())
706
AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
709
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
710
New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
711
Args.begin(), Args.end(), "", Call);
712
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
713
cast<InvokeInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
714
AttributesVec.end()));
716
New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
717
cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
718
cast<CallInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
719
AttributesVec.end()));
720
if (cast<CallInst>(Call)->isTailCall())
721
cast<CallInst>(New)->setTailCall();
724
AttributesVec.clear();
726
// Update the alias analysis implementation to know that we are replacing
727
// the old call with a new one.
728
AA.replaceWithNewValue(Call, New);
730
// Update the callgraph to know that the callsite has been transformed.
731
CallGraphNode *CalleeNode = CG[Call->getParent()->getParent()];
732
CalleeNode->replaceCallEdge(Call, New, NF_CGN);
734
if (!Call->use_empty()) {
735
Call->replaceAllUsesWith(New);
739
// Finally, remove the old call from the program, reducing the use-count of
741
Call->eraseFromParent();
744
// Since we have now created the new function, splice the body of the old
745
// function right into the new function, leaving the old rotting hulk of the
747
NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
749
// Loop over the argument list, transfering uses of the old arguments over to
750
// the new arguments, also transfering over the names as well.
752
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
753
I2 = NF->arg_begin(); I != E; ++I) {
754
if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
755
// If this is an unmodified argument, move the name and users over to the
757
I->replaceAllUsesWith(I2);
759
AA.replaceWithNewValue(I, I2);
764
if (ByValArgsToTransform.count(I)) {
765
// In the callee, we create an alloca, and store each of the new incoming
766
// arguments into the alloca.
767
Instruction *InsertPt = NF->begin()->begin();
769
// Just add all the struct element types.
770
const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
771
Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
772
const StructType *STy = cast<StructType>(AgTy);
774
ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
776
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
777
Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
779
GetElementPtrInst::Create(TheAlloca, Idxs, Idxs+2,
780
TheAlloca->getName()+"."+Twine(i),
782
I2->setName(I->getName()+"."+Twine(i));
783
new StoreInst(I2++, Idx, InsertPt);
786
// Anything that used the arg should now use the alloca.
787
I->replaceAllUsesWith(TheAlloca);
788
TheAlloca->takeName(I);
789
AA.replaceWithNewValue(I, TheAlloca);
793
if (I->use_empty()) {
798
// Otherwise, if we promoted this argument, then all users are load
799
// instructions (or GEPs with only load users), and all loads should be
800
// using the new argument that we added.
801
ScalarizeTable &ArgIndices = ScalarizedElements[I];
803
while (!I->use_empty()) {
804
if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
805
assert(ArgIndices.begin()->empty() &&
806
"Load element should sort to front!");
807
I2->setName(I->getName()+".val");
808
LI->replaceAllUsesWith(I2);
809
AA.replaceWithNewValue(LI, I2);
810
LI->eraseFromParent();
811
DEBUG(dbgs() << "*** Promoted load of argument '" << I->getName()
812
<< "' in function '" << F->getName() << "'\n");
814
GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
815
IndicesVector Operands;
816
Operands.reserve(GEP->getNumIndices());
817
for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
819
Operands.push_back(cast<ConstantInt>(*II)->getSExtValue());
821
// GEPs with a single 0 index can be merged with direct loads
822
if (Operands.size() == 1 && Operands.front() == 0)
825
Function::arg_iterator TheArg = I2;
826
for (ScalarizeTable::iterator It = ArgIndices.begin();
827
*It != Operands; ++It, ++TheArg) {
828
assert(It != ArgIndices.end() && "GEP not handled??");
831
std::string NewName = I->getName();
832
for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
833
NewName += "." + utostr(Operands[i]);
836
TheArg->setName(NewName);
838
DEBUG(dbgs() << "*** Promoted agg argument '" << TheArg->getName()
839
<< "' of function '" << NF->getName() << "'\n");
841
// All of the uses must be load instructions. Replace them all with
842
// the argument specified by ArgNo.
843
while (!GEP->use_empty()) {
844
LoadInst *L = cast<LoadInst>(GEP->use_back());
845
L->replaceAllUsesWith(TheArg);
846
AA.replaceWithNewValue(L, TheArg);
847
L->eraseFromParent();
850
GEP->eraseFromParent();
854
// Increment I2 past all of the arguments added for this promoted pointer.
855
for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
859
// Notify the alias analysis implementation that we inserted a new argument.
861
AA.copyValue(Constant::getNullValue(Type::getInt32Ty(F->getContext())),
865
// Tell the alias analysis that the old function is about to disappear.
866
AA.replaceWithNewValue(F, NF);
869
NF_CGN->stealCalledFunctionsFrom(CG[F]);
871
// Now that the old function is dead, delete it.
872
delete CG.removeFunctionFromModule(F);
added
removed
libclamav/c++/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
