1 //===-- ArgumentPromotion.cpp - Promote by-reference arguments ------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This pass promotes "by reference" arguments to be "by value" arguments. In
11 // practice, this means looking for internal functions that have pointer
12 // arguments. If it can prove, through the use of alias analysis, that an
13 // argument is *only* loaded, then it can pass the value into the function
14 // instead of the address of the value. This can cause recursive simplification
15 // of code and lead to the elimination of allocas (especially in C++ template
16 // code like the STL).
18 // This pass also handles aggregate arguments that are passed into a function,
19 // scalarizing them if the elements of the aggregate are only loaded. Note that
20 // by default it refuses to scalarize aggregates which would require passing in
21 // more than three operands to the function, because passing thousands of
22 // operands for a large array or structure is unprofitable! This limit can be
23 // configured or disabled, however.
25 // Note that this transformation could also be done for arguments that are only
26 // stored to (returning the value instead), but does not currently. This case
27 // would be best handled when and if LLVM begins supporting multiple return
28 // values from functions.
30 //===----------------------------------------------------------------------===//
32 #define DEBUG_TYPE "argpromotion"
33 #include "llvm/Transforms/IPO.h"
34 #include "llvm/ADT/DepthFirstIterator.h"
35 #include "llvm/ADT/Statistic.h"
36 #include "llvm/ADT/StringExtras.h"
37 #include "llvm/Analysis/AliasAnalysis.h"
38 #include "llvm/Analysis/CallGraph.h"
39 #include "llvm/Analysis/CallGraphSCCPass.h"
40 #include "llvm/IR/Constants.h"
41 #include "llvm/IR/DerivedTypes.h"
42 #include "llvm/IR/Instructions.h"
43 #include "llvm/IR/LLVMContext.h"
44 #include "llvm/IR/Module.h"
45 #include "llvm/Support/CFG.h"
46 #include "llvm/Support/CallSite.h"
47 #include "llvm/Support/Debug.h"
48 #include "llvm/Support/raw_ostream.h"
52 STATISTIC(NumArgumentsPromoted , "Number of pointer arguments promoted");
53 STATISTIC(NumAggregatesPromoted, "Number of aggregate arguments promoted");
54 STATISTIC(NumByValArgsPromoted , "Number of byval arguments promoted");
55 STATISTIC(NumArgumentsDead , "Number of dead pointer args eliminated");
58 /// ArgPromotion - The 'by reference' to 'by value' argument promotion pass.
60 struct ArgPromotion : public CallGraphSCCPass {
61 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
62 AU.addRequired<AliasAnalysis>();
63 CallGraphSCCPass::getAnalysisUsage(AU);
66 virtual bool runOnSCC(CallGraphSCC &SCC);
67 static char ID; // Pass identification, replacement for typeid
68 explicit ArgPromotion(unsigned maxElements = 3)
69 : CallGraphSCCPass(ID), maxElements(maxElements) {
70 initializeArgPromotionPass(*PassRegistry::getPassRegistry());
73 /// A vector used to hold the indices of a single GEP instruction
74 typedef std::vector<uint64_t> IndicesVector;
77 CallGraphNode *PromoteArguments(CallGraphNode *CGN);
78 bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const;
79 CallGraphNode *DoPromotion(Function *F,
80 SmallPtrSet<Argument*, 8> &ArgsToPromote,
81 SmallPtrSet<Argument*, 8> &ByValArgsToTransform);
82 /// The maximum number of elements to expand, or 0 for unlimited.
87 char ArgPromotion::ID = 0;
88 INITIALIZE_PASS_BEGIN(ArgPromotion, "argpromotion",
89 "Promote 'by reference' arguments to scalars", false, false)
90 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
91 INITIALIZE_PASS_DEPENDENCY(CallGraph)
92 INITIALIZE_PASS_END(ArgPromotion, "argpromotion",
93 "Promote 'by reference' arguments to scalars", false, false)
95 Pass *llvm::createArgumentPromotionPass(unsigned maxElements) {
96 return new ArgPromotion(maxElements);
99 bool ArgPromotion::runOnSCC(CallGraphSCC &SCC) {
100 bool Changed = false, LocalChange;
102 do { // Iterate until we stop promoting from this SCC.
104 // Attempt to promote arguments from all functions in this SCC.
105 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
106 if (CallGraphNode *CGN = PromoteArguments(*I)) {
108 SCC.ReplaceNode(*I, CGN);
111 Changed |= LocalChange; // Remember that we changed something.
112 } while (LocalChange);
117 /// PromoteArguments - This method checks the specified function to see if there
118 /// are any promotable arguments and if it is safe to promote the function (for
119 /// example, all callers are direct). If safe to promote some arguments, it
120 /// calls the DoPromotion method.
122 CallGraphNode *ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
123 Function *F = CGN->getFunction();
125 // Make sure that it is local to this module.
126 if (!F || !F->hasLocalLinkage()) return 0;
128 // First check: see if there are any pointer arguments! If not, quick exit.
129 SmallVector<Argument*, 16> PointerArgs;
130 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I)
131 if (I->getType()->isPointerTy())
132 PointerArgs.push_back(I);
133 if (PointerArgs.empty()) return 0;
135 // Second check: make sure that all callers are direct callers. We can't
136 // transform functions that have indirect callers. Also see if the function
137 // is self-recursive.
138 bool isSelfRecursive = false;
139 for (Value::use_iterator UI = F->use_begin(), E = F->use_end();
142 // Must be a direct call.
143 if (CS.getInstruction() == 0 || !CS.isCallee(UI)) return 0;
145 if (CS.getInstruction()->getParent()->getParent() == F)
146 isSelfRecursive = true;
149 // Check to see which arguments are promotable. If an argument is promotable,
150 // add it to ArgsToPromote.
151 SmallPtrSet<Argument*, 8> ArgsToPromote;
152 SmallPtrSet<Argument*, 8> ByValArgsToTransform;
153 for (unsigned i = 0, e = PointerArgs.size(); i != e; ++i) {
154 Argument *PtrArg = PointerArgs[i];
155 Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
157 // If this is a byval argument, and if the aggregate type is small, just
158 // pass the elements, which is always safe.
159 if (PtrArg->hasByValAttr()) {
160 if (StructType *STy = dyn_cast<StructType>(AgTy)) {
161 if (maxElements > 0 && STy->getNumElements() > maxElements) {
162 DEBUG(dbgs() << "argpromotion disable promoting argument '"
163 << PtrArg->getName() << "' because it would require adding more"
164 << " than " << maxElements << " arguments to the function.\n");
168 // If all the elements are single-value types, we can promote it.
169 bool AllSimple = true;
170 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
171 if (!STy->getElementType(i)->isSingleValueType()) {
177 // Safe to transform, don't even bother trying to "promote" it.
178 // Passing the elements as a scalar will allow scalarrepl to hack on
179 // the new alloca we introduce.
181 ByValArgsToTransform.insert(PtrArg);
187 // If the argument is a recursive type and we're in a recursive
188 // function, we could end up infinitely peeling the function argument.
189 if (isSelfRecursive) {
190 if (StructType *STy = dyn_cast<StructType>(AgTy)) {
191 bool RecursiveType = false;
192 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
193 if (STy->getElementType(i) == PtrArg->getType()) {
194 RecursiveType = true;
203 // Otherwise, see if we can promote the pointer to its value.
204 if (isSafeToPromoteArgument(PtrArg, PtrArg->hasByValAttr()))
205 ArgsToPromote.insert(PtrArg);
208 // No promotable pointer arguments.
209 if (ArgsToPromote.empty() && ByValArgsToTransform.empty())
212 return DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
215 /// AllCallersPassInValidPointerForArgument - Return true if we can prove that
216 /// all callees pass in a valid pointer for the specified function argument.
217 static bool AllCallersPassInValidPointerForArgument(Argument *Arg) {
218 Function *Callee = Arg->getParent();
220 unsigned ArgNo = Arg->getArgNo();
222 // Look at all call sites of the function. At this pointer we know we only
223 // have direct callees.
224 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
227 assert(CS && "Should only have direct calls!");
229 if (!CS.getArgument(ArgNo)->isDereferenceablePointer())
235 /// Returns true if Prefix is a prefix of longer. That means, Longer has a size
236 /// that is greater than or equal to the size of prefix, and each of the
237 /// elements in Prefix is the same as the corresponding elements in Longer.
239 /// This means it also returns true when Prefix and Longer are equal!
240 static bool IsPrefix(const ArgPromotion::IndicesVector &Prefix,
241 const ArgPromotion::IndicesVector &Longer) {
242 if (Prefix.size() > Longer.size())
244 return std::equal(Prefix.begin(), Prefix.end(), Longer.begin());
248 /// Checks if Indices, or a prefix of Indices, is in Set.
249 static bool PrefixIn(const ArgPromotion::IndicesVector &Indices,
250 std::set<ArgPromotion::IndicesVector> &Set) {
251 std::set<ArgPromotion::IndicesVector>::iterator Low;
252 Low = Set.upper_bound(Indices);
253 if (Low != Set.begin())
255 // Low is now the last element smaller than or equal to Indices. This means
256 // it points to a prefix of Indices (possibly Indices itself), if such
259 // This load is safe if any prefix of its operands is safe to load.
260 return Low != Set.end() && IsPrefix(*Low, Indices);
263 /// Mark the given indices (ToMark) as safe in the given set of indices
264 /// (Safe). Marking safe usually means adding ToMark to Safe. However, if there
265 /// is already a prefix of Indices in Safe, Indices are implicitely marked safe
266 /// already. Furthermore, any indices that Indices is itself a prefix of, are
267 /// removed from Safe (since they are implicitely safe because of Indices now).
268 static void MarkIndicesSafe(const ArgPromotion::IndicesVector &ToMark,
269 std::set<ArgPromotion::IndicesVector> &Safe) {
270 std::set<ArgPromotion::IndicesVector>::iterator Low;
271 Low = Safe.upper_bound(ToMark);
272 // Guard against the case where Safe is empty
273 if (Low != Safe.begin())
275 // Low is now the last element smaller than or equal to Indices. This
276 // means it points to a prefix of Indices (possibly Indices itself), if
277 // such prefix exists.
278 if (Low != Safe.end()) {
279 if (IsPrefix(*Low, ToMark))
280 // If there is already a prefix of these indices (or exactly these
281 // indices) marked a safe, don't bother adding these indices
284 // Increment Low, so we can use it as a "insert before" hint
288 Low = Safe.insert(Low, ToMark);
290 // If there we're a prefix of longer index list(s), remove those
291 std::set<ArgPromotion::IndicesVector>::iterator End = Safe.end();
292 while (Low != End && IsPrefix(ToMark, *Low)) {
293 std::set<ArgPromotion::IndicesVector>::iterator Remove = Low;
299 /// isSafeToPromoteArgument - As you might guess from the name of this method,
300 /// it checks to see if it is both safe and useful to promote the argument.
301 /// This method limits promotion of aggregates to only promote up to three
302 /// elements of the aggregate in order to avoid exploding the number of
303 /// arguments passed in.
304 bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
305 typedef std::set<IndicesVector> GEPIndicesSet;
307 // Quick exit for unused arguments
308 if (Arg->use_empty())
311 // We can only promote this argument if all of the uses are loads, or are GEP
312 // instructions (with constant indices) that are subsequently loaded.
314 // Promoting the argument causes it to be loaded in the caller
315 // unconditionally. This is only safe if we can prove that either the load
316 // would have happened in the callee anyway (ie, there is a load in the entry
317 // block) or the pointer passed in at every call site is guaranteed to be
319 // In the former case, invalid loads can happen, but would have happened
320 // anyway, in the latter case, invalid loads won't happen. This prevents us
321 // from introducing an invalid load that wouldn't have happened in the
324 // This set will contain all sets of indices that are loaded in the entry
325 // block, and thus are safe to unconditionally load in the caller.
326 GEPIndicesSet SafeToUnconditionallyLoad;
328 // This set contains all the sets of indices that we are planning to promote.
329 // This makes it possible to limit the number of arguments added.
330 GEPIndicesSet ToPromote;
332 // If the pointer is always valid, any load with first index 0 is valid.
333 if (isByVal || AllCallersPassInValidPointerForArgument(Arg))
334 SafeToUnconditionallyLoad.insert(IndicesVector(1, 0));
336 // First, iterate the entry block and mark loads of (geps of) arguments as
338 BasicBlock *EntryBlock = Arg->getParent()->begin();
339 // Declare this here so we can reuse it
340 IndicesVector Indices;
341 for (BasicBlock::iterator I = EntryBlock->begin(), E = EntryBlock->end();
343 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
344 Value *V = LI->getPointerOperand();
345 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
346 V = GEP->getPointerOperand();
348 // This load actually loads (part of) Arg? Check the indices then.
349 Indices.reserve(GEP->getNumIndices());
350 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
352 if (ConstantInt *CI = dyn_cast<ConstantInt>(*II))
353 Indices.push_back(CI->getSExtValue());
355 // We found a non-constant GEP index for this argument? Bail out
356 // right away, can't promote this argument at all.
359 // Indices checked out, mark them as safe
360 MarkIndicesSafe(Indices, SafeToUnconditionallyLoad);
363 } else if (V == Arg) {
364 // Direct loads are equivalent to a GEP with a single 0 index.
365 MarkIndicesSafe(IndicesVector(1, 0), SafeToUnconditionallyLoad);
369 // Now, iterate all uses of the argument to see if there are any uses that are
370 // not (GEP+)loads, or any (GEP+)loads that are not safe to promote.
371 SmallVector<LoadInst*, 16> Loads;
372 IndicesVector Operands;
373 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
377 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
378 // Don't hack volatile/atomic loads
379 if (!LI->isSimple()) return false;
381 // Direct loads are equivalent to a GEP with a zero index and then a load.
382 Operands.push_back(0);
383 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
384 if (GEP->use_empty()) {
385 // Dead GEP's cause trouble later. Just remove them if we run into
387 getAnalysis<AliasAnalysis>().deleteValue(GEP);
388 GEP->eraseFromParent();
389 // TODO: This runs the above loop over and over again for dead GEPs
390 // Couldn't we just do increment the UI iterator earlier and erase the
392 return isSafeToPromoteArgument(Arg, isByVal);
395 // Ensure that all of the indices are constants.
396 for (User::op_iterator i = GEP->idx_begin(), e = GEP->idx_end();
398 if (ConstantInt *C = dyn_cast<ConstantInt>(*i))
399 Operands.push_back(C->getSExtValue());
401 return false; // Not a constant operand GEP!
403 // Ensure that the only users of the GEP are load instructions.
404 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
406 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
407 // Don't hack volatile/atomic loads
408 if (!LI->isSimple()) return false;
411 // Other uses than load?
415 return false; // Not a load or a GEP.
418 // Now, see if it is safe to promote this load / loads of this GEP. Loading
419 // is safe if Operands, or a prefix of Operands, is marked as safe.
420 if (!PrefixIn(Operands, SafeToUnconditionallyLoad))
423 // See if we are already promoting a load with these indices. If not, check
424 // to make sure that we aren't promoting too many elements. If so, nothing
426 if (ToPromote.find(Operands) == ToPromote.end()) {
427 if (maxElements > 0 && ToPromote.size() == maxElements) {
428 DEBUG(dbgs() << "argpromotion not promoting argument '"
429 << Arg->getName() << "' because it would require adding more "
430 << "than " << maxElements << " arguments to the function.\n");
431 // We limit aggregate promotion to only promoting up to a fixed number
432 // of elements of the aggregate.
435 ToPromote.insert(Operands);
439 if (Loads.empty()) return true; // No users, this is a dead argument.
441 // Okay, now we know that the argument is only used by load instructions and
442 // it is safe to unconditionally perform all of them. Use alias analysis to
443 // check to see if the pointer is guaranteed to not be modified from entry of
444 // the function to each of the load instructions.
446 // Because there could be several/many load instructions, remember which
447 // blocks we know to be transparent to the load.
448 SmallPtrSet<BasicBlock*, 16> TranspBlocks;
450 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
452 for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
453 // Check to see if the load is invalidated from the start of the block to
455 LoadInst *Load = Loads[i];
456 BasicBlock *BB = Load->getParent();
458 AliasAnalysis::Location Loc = AA.getLocation(Load);
459 if (AA.canInstructionRangeModify(BB->front(), *Load, Loc))
460 return false; // Pointer is invalidated!
462 // Now check every path from the entry block to the load for transparency.
463 // To do this, we perform a depth first search on the inverse CFG from the
465 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
467 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
468 I = idf_ext_begin(P, TranspBlocks),
469 E = idf_ext_end(P, TranspBlocks); I != E; ++I)
470 if (AA.canBasicBlockModify(**I, Loc))
475 // If the path from the entry of the function to each load is free of
476 // instructions that potentially invalidate the load, we can make the
481 /// DoPromotion - This method actually performs the promotion of the specified
482 /// arguments, and returns the new function. At this point, we know that it's
484 CallGraphNode *ArgPromotion::DoPromotion(Function *F,
485 SmallPtrSet<Argument*, 8> &ArgsToPromote,
486 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
488 // Start by computing a new prototype for the function, which is the same as
489 // the old function, but has modified arguments.
490 FunctionType *FTy = F->getFunctionType();
491 std::vector<Type*> Params;
493 typedef std::set<IndicesVector> ScalarizeTable;
495 // ScalarizedElements - If we are promoting a pointer that has elements
496 // accessed out of it, keep track of which elements are accessed so that we
497 // can add one argument for each.
499 // Arguments that are directly loaded will have a zero element value here, to
500 // handle cases where there are both a direct load and GEP accesses.
502 std::map<Argument*, ScalarizeTable> ScalarizedElements;
504 // OriginalLoads - Keep track of a representative load instruction from the
505 // original function so that we can tell the alias analysis implementation
506 // what the new GEP/Load instructions we are inserting look like.
507 std::map<IndicesVector, LoadInst*> OriginalLoads;
509 // Attribute - Keep track of the parameter attributes for the arguments
510 // that we are *not* promoting. For the ones that we do promote, the parameter
511 // attributes are lost
512 SmallVector<AttributeSet, 8> AttributesVec;
513 const AttributeSet &PAL = F->getAttributes();
515 // Add any return attributes.
516 if (PAL.hasAttributes(AttributeSet::ReturnIndex))
517 AttributesVec.push_back(AttributeSet::get(F->getContext(),
518 PAL.getRetAttributes()));
520 // First, determine the new argument list
521 unsigned ArgIndex = 1;
522 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
524 if (ByValArgsToTransform.count(I)) {
525 // Simple byval argument? Just add all the struct element types.
526 Type *AgTy = cast<PointerType>(I->getType())->getElementType();
527 StructType *STy = cast<StructType>(AgTy);
528 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
529 Params.push_back(STy->getElementType(i));
530 ++NumByValArgsPromoted;
531 } else if (!ArgsToPromote.count(I)) {
532 // Unchanged argument
533 Params.push_back(I->getType());
534 AttributeSet attrs = PAL.getParamAttributes(ArgIndex);
535 if (attrs.hasAttributes(ArgIndex)) {
536 AttrBuilder B(attrs, ArgIndex);
538 push_back(AttributeSet::get(F->getContext(), Params.size(), B));
540 } else if (I->use_empty()) {
541 // Dead argument (which are always marked as promotable)
544 // Okay, this is being promoted. This means that the only uses are loads
545 // or GEPs which are only used by loads
547 // In this table, we will track which indices are loaded from the argument
548 // (where direct loads are tracked as no indices).
549 ScalarizeTable &ArgIndices = ScalarizedElements[I];
550 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
552 Instruction *User = cast<Instruction>(*UI);
553 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
554 IndicesVector Indices;
555 Indices.reserve(User->getNumOperands() - 1);
556 // Since loads will only have a single operand, and GEPs only a single
557 // non-index operand, this will record direct loads without any indices,
558 // and gep+loads with the GEP indices.
559 for (User::op_iterator II = User->op_begin() + 1, IE = User->op_end();
561 Indices.push_back(cast<ConstantInt>(*II)->getSExtValue());
562 // GEPs with a single 0 index can be merged with direct loads
563 if (Indices.size() == 1 && Indices.front() == 0)
565 ArgIndices.insert(Indices);
567 if (LoadInst *L = dyn_cast<LoadInst>(User))
570 // Take any load, we will use it only to update Alias Analysis
571 OrigLoad = cast<LoadInst>(User->use_back());
572 OriginalLoads[Indices] = OrigLoad;
575 // Add a parameter to the function for each element passed in.
576 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
577 E = ArgIndices.end(); SI != E; ++SI) {
578 // not allowed to dereference ->begin() if size() is 0
579 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(), *SI));
580 assert(Params.back());
583 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
584 ++NumArgumentsPromoted;
586 ++NumAggregatesPromoted;
590 // Add any function attributes.
591 if (PAL.hasAttributes(AttributeSet::FunctionIndex))
592 AttributesVec.push_back(AttributeSet::get(FTy->getContext(),
593 PAL.getFnAttributes()));
595 Type *RetTy = FTy->getReturnType();
597 // Construct the new function type using the new arguments.
598 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
600 // Create the new function body and insert it into the module.
601 Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
602 NF->copyAttributesFrom(F);
605 DEBUG(dbgs() << "ARG PROMOTION: Promoting to:" << *NF << "\n"
608 // Recompute the parameter attributes list based on the new arguments for
610 NF->setAttributes(AttributeSet::get(F->getContext(), AttributesVec));
611 AttributesVec.clear();
613 F->getParent()->getFunctionList().insert(F, NF);
616 // Get the alias analysis information that we need to update to reflect our
618 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
620 // Get the callgraph information that we need to update to reflect our
622 CallGraph &CG = getAnalysis<CallGraph>();
624 // Get a new callgraph node for NF.
625 CallGraphNode *NF_CGN = CG.getOrInsertFunction(NF);
627 // Loop over all of the callers of the function, transforming the call sites
628 // to pass in the loaded pointers.
630 SmallVector<Value*, 16> Args;
631 while (!F->use_empty()) {
632 CallSite CS(F->use_back());
633 assert(CS.getCalledFunction() == F);
634 Instruction *Call = CS.getInstruction();
635 const AttributeSet &CallPAL = CS.getAttributes();
637 // Add any return attributes.
638 if (CallPAL.hasAttributes(AttributeSet::ReturnIndex))
639 AttributesVec.push_back(AttributeSet::get(F->getContext(),
640 CallPAL.getRetAttributes()));
642 // Loop over the operands, inserting GEP and loads in the caller as
644 CallSite::arg_iterator AI = CS.arg_begin();
646 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
647 I != E; ++I, ++AI, ++ArgIndex)
648 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
649 Args.push_back(*AI); // Unmodified argument
651 if (CallPAL.hasAttributes(ArgIndex)) {
652 AttrBuilder B(CallPAL, ArgIndex);
654 push_back(AttributeSet::get(F->getContext(), Args.size(), B));
656 } else if (ByValArgsToTransform.count(I)) {
657 // Emit a GEP and load for each element of the struct.
658 Type *AgTy = cast<PointerType>(I->getType())->getElementType();
659 StructType *STy = cast<StructType>(AgTy);
661 ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
662 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
663 Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
664 Value *Idx = GetElementPtrInst::Create(*AI, Idxs,
665 (*AI)->getName()+"."+utostr(i),
667 // TODO: Tell AA about the new values?
668 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
670 } else if (!I->use_empty()) {
671 // Non-dead argument: insert GEPs and loads as appropriate.
672 ScalarizeTable &ArgIndices = ScalarizedElements[I];
673 // Store the Value* version of the indices in here, but declare it now
675 std::vector<Value*> Ops;
676 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
677 E = ArgIndices.end(); SI != E; ++SI) {
679 LoadInst *OrigLoad = OriginalLoads[*SI];
681 Ops.reserve(SI->size());
682 Type *ElTy = V->getType();
683 for (IndicesVector::const_iterator II = SI->begin(),
684 IE = SI->end(); II != IE; ++II) {
685 // Use i32 to index structs, and i64 for others (pointers/arrays).
686 // This satisfies GEP constraints.
687 Type *IdxTy = (ElTy->isStructTy() ?
688 Type::getInt32Ty(F->getContext()) :
689 Type::getInt64Ty(F->getContext()));
690 Ops.push_back(ConstantInt::get(IdxTy, *II));
691 // Keep track of the type we're currently indexing.
692 ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(*II);
694 // And create a GEP to extract those indices.
695 V = GetElementPtrInst::Create(V, Ops, V->getName()+".idx", Call);
697 AA.copyValue(OrigLoad->getOperand(0), V);
699 // Since we're replacing a load make sure we take the alignment
700 // of the previous load.
701 LoadInst *newLoad = new LoadInst(V, V->getName()+".val", Call);
702 newLoad->setAlignment(OrigLoad->getAlignment());
703 // Transfer the TBAA info too.
704 newLoad->setMetadata(LLVMContext::MD_tbaa,
705 OrigLoad->getMetadata(LLVMContext::MD_tbaa));
706 Args.push_back(newLoad);
707 AA.copyValue(OrigLoad, Args.back());
711 // Push any varargs arguments on the list.
712 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
714 if (CallPAL.hasAttributes(ArgIndex)) {
715 AttrBuilder B(CallPAL, ArgIndex);
717 push_back(AttributeSet::get(F->getContext(), Args.size(), B));
721 // Add any function attributes.
722 if (CallPAL.hasAttributes(AttributeSet::FunctionIndex))
723 AttributesVec.push_back(AttributeSet::get(Call->getContext(),
724 CallPAL.getFnAttributes()));
727 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
728 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
730 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
731 cast<InvokeInst>(New)->setAttributes(AttributeSet::get(II->getContext(),
734 New = CallInst::Create(NF, Args, "", Call);
735 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
736 cast<CallInst>(New)->setAttributes(AttributeSet::get(New->getContext(),
738 if (cast<CallInst>(Call)->isTailCall())
739 cast<CallInst>(New)->setTailCall();
742 AttributesVec.clear();
744 // Update the alias analysis implementation to know that we are replacing
745 // the old call with a new one.
746 AA.replaceWithNewValue(Call, New);
748 // Update the callgraph to know that the callsite has been transformed.
749 CallGraphNode *CalleeNode = CG[Call->getParent()->getParent()];
750 CalleeNode->replaceCallEdge(Call, New, NF_CGN);
752 if (!Call->use_empty()) {
753 Call->replaceAllUsesWith(New);
757 // Finally, remove the old call from the program, reducing the use-count of
759 Call->eraseFromParent();
762 // Since we have now created the new function, splice the body of the old
763 // function right into the new function, leaving the old rotting hulk of the
765 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
767 // Loop over the argument list, transferring uses of the old arguments over to
768 // the new arguments, also transferring over the names as well.
770 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
771 I2 = NF->arg_begin(); I != E; ++I) {
772 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
773 // If this is an unmodified argument, move the name and users over to the
775 I->replaceAllUsesWith(I2);
777 AA.replaceWithNewValue(I, I2);
782 if (ByValArgsToTransform.count(I)) {
783 // In the callee, we create an alloca, and store each of the new incoming
784 // arguments into the alloca.
785 Instruction *InsertPt = NF->begin()->begin();
787 // Just add all the struct element types.
788 Type *AgTy = cast<PointerType>(I->getType())->getElementType();
789 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
790 StructType *STy = cast<StructType>(AgTy);
792 ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
794 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
795 Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
797 GetElementPtrInst::Create(TheAlloca, Idxs,
798 TheAlloca->getName()+"."+Twine(i),
800 I2->setName(I->getName()+"."+Twine(i));
801 new StoreInst(I2++, Idx, InsertPt);
804 // Anything that used the arg should now use the alloca.
805 I->replaceAllUsesWith(TheAlloca);
806 TheAlloca->takeName(I);
807 AA.replaceWithNewValue(I, TheAlloca);
811 if (I->use_empty()) {
816 // Otherwise, if we promoted this argument, then all users are load
817 // instructions (or GEPs with only load users), and all loads should be
818 // using the new argument that we added.
819 ScalarizeTable &ArgIndices = ScalarizedElements[I];
821 while (!I->use_empty()) {
822 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
823 assert(ArgIndices.begin()->empty() &&
824 "Load element should sort to front!");
825 I2->setName(I->getName()+".val");
826 LI->replaceAllUsesWith(I2);
827 AA.replaceWithNewValue(LI, I2);
828 LI->eraseFromParent();
829 DEBUG(dbgs() << "*** Promoted load of argument '" << I->getName()
830 << "' in function '" << F->getName() << "'\n");
832 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
833 IndicesVector Operands;
834 Operands.reserve(GEP->getNumIndices());
835 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
837 Operands.push_back(cast<ConstantInt>(*II)->getSExtValue());
839 // GEPs with a single 0 index can be merged with direct loads
840 if (Operands.size() == 1 && Operands.front() == 0)
843 Function::arg_iterator TheArg = I2;
844 for (ScalarizeTable::iterator It = ArgIndices.begin();
845 *It != Operands; ++It, ++TheArg) {
846 assert(It != ArgIndices.end() && "GEP not handled??");
849 std::string NewName = I->getName();
850 for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
851 NewName += "." + utostr(Operands[i]);
854 TheArg->setName(NewName);
856 DEBUG(dbgs() << "*** Promoted agg argument '" << TheArg->getName()
857 << "' of function '" << NF->getName() << "'\n");
859 // All of the uses must be load instructions. Replace them all with
860 // the argument specified by ArgNo.
861 while (!GEP->use_empty()) {
862 LoadInst *L = cast<LoadInst>(GEP->use_back());
863 L->replaceAllUsesWith(TheArg);
864 AA.replaceWithNewValue(L, TheArg);
865 L->eraseFromParent();
868 GEP->eraseFromParent();
872 // Increment I2 past all of the arguments added for this promoted pointer.
873 std::advance(I2, ArgIndices.size());
876 // Tell the alias analysis that the old function is about to disappear.
877 AA.replaceWithNewValue(F, NF);
880 NF_CGN->stealCalledFunctionsFrom(CG[F]);
882 // Now that the old function is dead, delete it. If there is a dangling
883 // reference to the CallgraphNode, just leave the dead function around for
884 // someone else to nuke.
885 CallGraphNode *CGN = CG[F];
886 if (CGN->getNumReferences() == 0)
887 delete CG.removeFunctionFromModule(CGN);
889 F->setLinkage(Function::ExternalLinkage);