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/Constants.h"
35 #include "llvm/DerivedTypes.h"
36 #include "llvm/Module.h"
37 #include "llvm/CallGraphSCCPass.h"
38 #include "llvm/Instructions.h"
39 #include "llvm/LLVMContext.h"
40 #include "llvm/Analysis/AliasAnalysis.h"
41 #include "llvm/Analysis/CallGraph.h"
42 #include "llvm/Support/CallSite.h"
43 #include "llvm/Support/CFG.h"
44 #include "llvm/Support/Debug.h"
45 #include "llvm/Support/raw_ostream.h"
46 #include "llvm/ADT/DepthFirstIterator.h"
47 #include "llvm/ADT/Statistic.h"
48 #include "llvm/ADT/StringExtras.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_AG_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<std::pair<Argument*, unsigned>, 16> PointerArgs;
131 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
132 I != E; ++I, ++ArgNo)
133 if (I->getType()->isPointerTy())
134 PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo));
135 if (PointerArgs.empty()) return 0;
137 // Second check: make sure that all callers are direct callers. We can't
138 // transform functions that have indirect callers.
139 if (F->hasAddressTaken())
142 // Check to see which arguments are promotable. If an argument is promotable,
143 // add it to ArgsToPromote.
144 SmallPtrSet<Argument*, 8> ArgsToPromote;
145 SmallPtrSet<Argument*, 8> ByValArgsToTransform;
146 for (unsigned i = 0; i != PointerArgs.size(); ++i) {
147 bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, Attribute::ByVal);
149 // If this is a byval argument, and if the aggregate type is small, just
150 // pass the elements, which is always safe.
151 Argument *PtrArg = PointerArgs[i].first;
153 const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
154 if (const StructType *STy = dyn_cast<StructType>(AgTy)) {
155 if (maxElements > 0 && STy->getNumElements() > maxElements) {
156 DEBUG(dbgs() << "argpromotion disable promoting argument '"
157 << PtrArg->getName() << "' because it would require adding more"
158 << " than " << maxElements << " arguments to the function.\n");
160 // If all the elements are single-value types, we can promote it.
161 bool AllSimple = true;
162 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
163 if (!STy->getElementType(i)->isSingleValueType()) {
168 // Safe to transform, don't even bother trying to "promote" it.
169 // Passing the elements as a scalar will allow scalarrepl to hack on
170 // the new alloca we introduce.
172 ByValArgsToTransform.insert(PtrArg);
179 // Otherwise, see if we can promote the pointer to its value.
180 if (isSafeToPromoteArgument(PtrArg, isByVal))
181 ArgsToPromote.insert(PtrArg);
184 // No promotable pointer arguments.
185 if (ArgsToPromote.empty() && ByValArgsToTransform.empty())
188 return DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
191 /// AllCalleesPassInValidPointerForArgument - Return true if we can prove that
192 /// all callees pass in a valid pointer for the specified function argument.
193 static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
194 Function *Callee = Arg->getParent();
196 unsigned ArgNo = std::distance(Callee->arg_begin(),
197 Function::arg_iterator(Arg));
199 // Look at all call sites of the function. At this pointer we know we only
200 // have direct callees.
201 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
204 assert(CS && "Should only have direct calls!");
206 if (!CS.getArgument(ArgNo)->isDereferenceablePointer())
212 /// Returns true if Prefix is a prefix of longer. That means, Longer has a size
213 /// that is greater than or equal to the size of prefix, and each of the
214 /// elements in Prefix is the same as the corresponding elements in Longer.
216 /// This means it also returns true when Prefix and Longer are equal!
217 static bool IsPrefix(const ArgPromotion::IndicesVector &Prefix,
218 const ArgPromotion::IndicesVector &Longer) {
219 if (Prefix.size() > Longer.size())
221 for (unsigned i = 0, e = Prefix.size(); i != e; ++i)
222 if (Prefix[i] != Longer[i])
228 /// Checks if Indices, or a prefix of Indices, is in Set.
229 static bool PrefixIn(const ArgPromotion::IndicesVector &Indices,
230 std::set<ArgPromotion::IndicesVector> &Set) {
231 std::set<ArgPromotion::IndicesVector>::iterator Low;
232 Low = Set.upper_bound(Indices);
233 if (Low != Set.begin())
235 // Low is now the last element smaller than or equal to Indices. This means
236 // it points to a prefix of Indices (possibly Indices itself), if such
239 // This load is safe if any prefix of its operands is safe to load.
240 return Low != Set.end() && IsPrefix(*Low, Indices);
243 /// Mark the given indices (ToMark) as safe in the given set of indices
244 /// (Safe). Marking safe usually means adding ToMark to Safe. However, if there
245 /// is already a prefix of Indices in Safe, Indices are implicitely marked safe
246 /// already. Furthermore, any indices that Indices is itself a prefix of, are
247 /// removed from Safe (since they are implicitely safe because of Indices now).
248 static void MarkIndicesSafe(const ArgPromotion::IndicesVector &ToMark,
249 std::set<ArgPromotion::IndicesVector> &Safe) {
250 std::set<ArgPromotion::IndicesVector>::iterator Low;
251 Low = Safe.upper_bound(ToMark);
252 // Guard against the case where Safe is empty
253 if (Low != Safe.begin())
255 // Low is now the last element smaller than or equal to Indices. This
256 // means it points to a prefix of Indices (possibly Indices itself), if
257 // such prefix exists.
258 if (Low != Safe.end()) {
259 if (IsPrefix(*Low, ToMark))
260 // If there is already a prefix of these indices (or exactly these
261 // indices) marked a safe, don't bother adding these indices
264 // Increment Low, so we can use it as a "insert before" hint
268 Low = Safe.insert(Low, ToMark);
270 // If there we're a prefix of longer index list(s), remove those
271 std::set<ArgPromotion::IndicesVector>::iterator End = Safe.end();
272 while (Low != End && IsPrefix(ToMark, *Low)) {
273 std::set<ArgPromotion::IndicesVector>::iterator Remove = Low;
279 /// isSafeToPromoteArgument - As you might guess from the name of this method,
280 /// it checks to see if it is both safe and useful to promote the argument.
281 /// This method limits promotion of aggregates to only promote up to three
282 /// elements of the aggregate in order to avoid exploding the number of
283 /// arguments passed in.
284 bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
285 typedef std::set<IndicesVector> GEPIndicesSet;
287 // Quick exit for unused arguments
288 if (Arg->use_empty())
291 // We can only promote this argument if all of the uses are loads, or are GEP
292 // instructions (with constant indices) that are subsequently loaded.
294 // Promoting the argument causes it to be loaded in the caller
295 // unconditionally. This is only safe if we can prove that either the load
296 // would have happened in the callee anyway (ie, there is a load in the entry
297 // block) or the pointer passed in at every call site is guaranteed to be
299 // In the former case, invalid loads can happen, but would have happened
300 // anyway, in the latter case, invalid loads won't happen. This prevents us
301 // from introducing an invalid load that wouldn't have happened in the
304 // This set will contain all sets of indices that are loaded in the entry
305 // block, and thus are safe to unconditionally load in the caller.
306 GEPIndicesSet SafeToUnconditionallyLoad;
308 // This set contains all the sets of indices that we are planning to promote.
309 // This makes it possible to limit the number of arguments added.
310 GEPIndicesSet ToPromote;
312 // If the pointer is always valid, any load with first index 0 is valid.
313 if (isByVal || AllCalleesPassInValidPointerForArgument(Arg))
314 SafeToUnconditionallyLoad.insert(IndicesVector(1, 0));
316 // First, iterate the entry block and mark loads of (geps of) arguments as
318 BasicBlock *EntryBlock = Arg->getParent()->begin();
319 // Declare this here so we can reuse it
320 IndicesVector Indices;
321 for (BasicBlock::iterator I = EntryBlock->begin(), E = EntryBlock->end();
323 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
324 Value *V = LI->getPointerOperand();
325 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
326 V = GEP->getPointerOperand();
328 // This load actually loads (part of) Arg? Check the indices then.
329 Indices.reserve(GEP->getNumIndices());
330 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
332 if (ConstantInt *CI = dyn_cast<ConstantInt>(*II))
333 Indices.push_back(CI->getSExtValue());
335 // We found a non-constant GEP index for this argument? Bail out
336 // right away, can't promote this argument at all.
339 // Indices checked out, mark them as safe
340 MarkIndicesSafe(Indices, SafeToUnconditionallyLoad);
343 } else if (V == Arg) {
344 // Direct loads are equivalent to a GEP with a single 0 index.
345 MarkIndicesSafe(IndicesVector(1, 0), SafeToUnconditionallyLoad);
349 // Now, iterate all uses of the argument to see if there are any uses that are
350 // not (GEP+)loads, or any (GEP+)loads that are not safe to promote.
351 SmallVector<LoadInst*, 16> Loads;
352 IndicesVector Operands;
353 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
357 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
358 if (LI->isVolatile()) return false; // Don't hack volatile loads
360 // Direct loads are equivalent to a GEP with a zero index and then a load.
361 Operands.push_back(0);
362 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
363 if (GEP->use_empty()) {
364 // Dead GEP's cause trouble later. Just remove them if we run into
366 getAnalysis<AliasAnalysis>().deleteValue(GEP);
367 GEP->eraseFromParent();
368 // TODO: This runs the above loop over and over again for dead GEPs
369 // Couldn't we just do increment the UI iterator earlier and erase the
371 return isSafeToPromoteArgument(Arg, isByVal);
374 // Ensure that all of the indices are constants.
375 for (User::op_iterator i = GEP->idx_begin(), e = GEP->idx_end();
377 if (ConstantInt *C = dyn_cast<ConstantInt>(*i))
378 Operands.push_back(C->getSExtValue());
380 return false; // Not a constant operand GEP!
382 // Ensure that the only users of the GEP are load instructions.
383 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
385 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
386 if (LI->isVolatile()) return false; // Don't hack volatile loads
389 // Other uses than load?
393 return false; // Not a load or a GEP.
396 // Now, see if it is safe to promote this load / loads of this GEP. Loading
397 // is safe if Operands, or a prefix of Operands, is marked as safe.
398 if (!PrefixIn(Operands, SafeToUnconditionallyLoad))
401 // See if we are already promoting a load with these indices. If not, check
402 // to make sure that we aren't promoting too many elements. If so, nothing
404 if (ToPromote.find(Operands) == ToPromote.end()) {
405 if (maxElements > 0 && ToPromote.size() == maxElements) {
406 DEBUG(dbgs() << "argpromotion not promoting argument '"
407 << Arg->getName() << "' because it would require adding more "
408 << "than " << maxElements << " arguments to the function.\n");
409 // We limit aggregate promotion to only promoting up to a fixed number
410 // of elements of the aggregate.
413 ToPromote.insert(Operands);
417 if (Loads.empty()) return true; // No users, this is a dead argument.
419 // Okay, now we know that the argument is only used by load instructions and
420 // it is safe to unconditionally perform all of them. Use alias analysis to
421 // check to see if the pointer is guaranteed to not be modified from entry of
422 // the function to each of the load instructions.
424 // Because there could be several/many load instructions, remember which
425 // blocks we know to be transparent to the load.
426 SmallPtrSet<BasicBlock*, 16> TranspBlocks;
428 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
430 for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
431 // Check to see if the load is invalidated from the start of the block to
433 LoadInst *Load = Loads[i];
434 BasicBlock *BB = Load->getParent();
436 AliasAnalysis::Location Loc = AA.getLocation(Load);
437 if (AA.canInstructionRangeModify(BB->front(), *Load, Loc))
438 return false; // Pointer is invalidated!
440 // Now check every path from the entry block to the load for transparency.
441 // To do this, we perform a depth first search on the inverse CFG from the
443 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
445 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
446 I = idf_ext_begin(P, TranspBlocks),
447 E = idf_ext_end(P, TranspBlocks); I != E; ++I)
448 if (AA.canBasicBlockModify(**I, Loc))
453 // If the path from the entry of the function to each load is free of
454 // instructions that potentially invalidate the load, we can make the
459 /// DoPromotion - This method actually performs the promotion of the specified
460 /// arguments, and returns the new function. At this point, we know that it's
462 CallGraphNode *ArgPromotion::DoPromotion(Function *F,
463 SmallPtrSet<Argument*, 8> &ArgsToPromote,
464 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
466 // Start by computing a new prototype for the function, which is the same as
467 // the old function, but has modified arguments.
468 const FunctionType *FTy = F->getFunctionType();
469 std::vector<const Type*> Params;
471 typedef std::set<IndicesVector> ScalarizeTable;
473 // ScalarizedElements - If we are promoting a pointer that has elements
474 // accessed out of it, keep track of which elements are accessed so that we
475 // can add one argument for each.
477 // Arguments that are directly loaded will have a zero element value here, to
478 // handle cases where there are both a direct load and GEP accesses.
480 std::map<Argument*, ScalarizeTable> ScalarizedElements;
482 // OriginalLoads - Keep track of a representative load instruction from the
483 // original function so that we can tell the alias analysis implementation
484 // what the new GEP/Load instructions we are inserting look like.
485 std::map<IndicesVector, LoadInst*> OriginalLoads;
487 // Attributes - Keep track of the parameter attributes for the arguments
488 // that we are *not* promoting. For the ones that we do promote, the parameter
489 // attributes are lost
490 SmallVector<AttributeWithIndex, 8> AttributesVec;
491 const AttrListPtr &PAL = F->getAttributes();
493 // Add any return attributes.
494 if (Attributes attrs = PAL.getRetAttributes())
495 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
497 // First, determine the new argument list
498 unsigned ArgIndex = 1;
499 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
501 if (ByValArgsToTransform.count(I)) {
502 // Simple byval argument? Just add all the struct element types.
503 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
504 const StructType *STy = cast<StructType>(AgTy);
505 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
506 Params.push_back(STy->getElementType(i));
507 ++NumByValArgsPromoted;
508 } else if (!ArgsToPromote.count(I)) {
509 // Unchanged argument
510 Params.push_back(I->getType());
511 if (Attributes attrs = PAL.getParamAttributes(ArgIndex))
512 AttributesVec.push_back(AttributeWithIndex::get(Params.size(), attrs));
513 } else if (I->use_empty()) {
514 // Dead argument (which are always marked as promotable)
517 // Okay, this is being promoted. This means that the only uses are loads
518 // or GEPs which are only used by loads
520 // In this table, we will track which indices are loaded from the argument
521 // (where direct loads are tracked as no indices).
522 ScalarizeTable &ArgIndices = ScalarizedElements[I];
523 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
525 Instruction *User = cast<Instruction>(*UI);
526 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
527 IndicesVector Indices;
528 Indices.reserve(User->getNumOperands() - 1);
529 // Since loads will only have a single operand, and GEPs only a single
530 // non-index operand, this will record direct loads without any indices,
531 // and gep+loads with the GEP indices.
532 for (User::op_iterator II = User->op_begin() + 1, IE = User->op_end();
534 Indices.push_back(cast<ConstantInt>(*II)->getSExtValue());
535 // GEPs with a single 0 index can be merged with direct loads
536 if (Indices.size() == 1 && Indices.front() == 0)
538 ArgIndices.insert(Indices);
540 if (LoadInst *L = dyn_cast<LoadInst>(User))
543 // Take any load, we will use it only to update Alias Analysis
544 OrigLoad = cast<LoadInst>(User->use_back());
545 OriginalLoads[Indices] = OrigLoad;
548 // Add a parameter to the function for each element passed in.
549 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
550 E = ArgIndices.end(); SI != E; ++SI) {
551 // not allowed to dereference ->begin() if size() is 0
552 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(),
555 assert(Params.back());
558 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
559 ++NumArgumentsPromoted;
561 ++NumAggregatesPromoted;
565 // Add any function attributes.
566 if (Attributes attrs = PAL.getFnAttributes())
567 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
569 const Type *RetTy = FTy->getReturnType();
571 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
572 // have zero fixed arguments.
573 bool ExtraArgHack = false;
574 if (Params.empty() && FTy->isVarArg()) {
576 Params.push_back(Type::getInt32Ty(F->getContext()));
579 // Construct the new function type using the new arguments.
580 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
582 // Create the new function body and insert it into the module.
583 Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
584 NF->copyAttributesFrom(F);
587 DEBUG(dbgs() << "ARG PROMOTION: Promoting to:" << *NF << "\n"
590 // Recompute the parameter attributes list based on the new arguments for
592 NF->setAttributes(AttrListPtr::get(AttributesVec.begin(),
593 AttributesVec.end()));
594 AttributesVec.clear();
596 F->getParent()->getFunctionList().insert(F, NF);
599 // Get the alias analysis information that we need to update to reflect our
601 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
603 // Get the callgraph information that we need to update to reflect our
605 CallGraph &CG = getAnalysis<CallGraph>();
607 // Get a new callgraph node for NF.
608 CallGraphNode *NF_CGN = CG.getOrInsertFunction(NF);
610 // Loop over all of the callers of the function, transforming the call sites
611 // to pass in the loaded pointers.
613 SmallVector<Value*, 16> Args;
614 while (!F->use_empty()) {
615 CallSite CS(F->use_back());
616 assert(CS.getCalledFunction() == F);
617 Instruction *Call = CS.getInstruction();
618 const AttrListPtr &CallPAL = CS.getAttributes();
620 // Add any return attributes.
621 if (Attributes attrs = CallPAL.getRetAttributes())
622 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
624 // Loop over the operands, inserting GEP and loads in the caller as
626 CallSite::arg_iterator AI = CS.arg_begin();
628 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
629 I != E; ++I, ++AI, ++ArgIndex)
630 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
631 Args.push_back(*AI); // Unmodified argument
633 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
634 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
636 } else if (ByValArgsToTransform.count(I)) {
637 // Emit a GEP and load for each element of the struct.
638 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
639 const StructType *STy = cast<StructType>(AgTy);
641 ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
642 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
643 Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
644 Value *Idx = GetElementPtrInst::Create(*AI, Idxs, Idxs+2,
645 (*AI)->getName()+"."+utostr(i),
647 // TODO: Tell AA about the new values?
648 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
650 } else if (!I->use_empty()) {
651 // Non-dead argument: insert GEPs and loads as appropriate.
652 ScalarizeTable &ArgIndices = ScalarizedElements[I];
653 // Store the Value* version of the indices in here, but declare it now
655 std::vector<Value*> Ops;
656 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
657 E = ArgIndices.end(); SI != E; ++SI) {
659 LoadInst *OrigLoad = OriginalLoads[*SI];
661 Ops.reserve(SI->size());
662 const Type *ElTy = V->getType();
663 for (IndicesVector::const_iterator II = SI->begin(),
664 IE = SI->end(); II != IE; ++II) {
665 // Use i32 to index structs, and i64 for others (pointers/arrays).
666 // This satisfies GEP constraints.
667 const Type *IdxTy = (ElTy->isStructTy() ?
668 Type::getInt32Ty(F->getContext()) :
669 Type::getInt64Ty(F->getContext()));
670 Ops.push_back(ConstantInt::get(IdxTy, *II));
671 // Keep track of the type we're currently indexing.
672 ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(*II);
674 // And create a GEP to extract those indices.
675 V = GetElementPtrInst::Create(V, Ops.begin(), Ops.end(),
676 V->getName()+".idx", Call);
678 AA.copyValue(OrigLoad->getOperand(0), V);
680 // Since we're replacing a load make sure we take the alignment
681 // of the previous load.
682 LoadInst *newLoad = new LoadInst(V, V->getName()+".val", Call);
683 newLoad->setAlignment(OrigLoad->getAlignment());
684 // Transfer the TBAA info too.
685 newLoad->setMetadata(LLVMContext::MD_tbaa,
686 OrigLoad->getMetadata(LLVMContext::MD_tbaa));
687 Args.push_back(newLoad);
688 AA.copyValue(OrigLoad, Args.back());
693 Args.push_back(Constant::getNullValue(Type::getInt32Ty(F->getContext())));
695 // Push any varargs arguments on the list.
696 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
698 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
699 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
702 // Add any function attributes.
703 if (Attributes attrs = CallPAL.getFnAttributes())
704 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
707 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
708 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
709 Args.begin(), Args.end(), "", Call);
710 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
711 cast<InvokeInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
712 AttributesVec.end()));
714 New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
715 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
716 cast<CallInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
717 AttributesVec.end()));
718 if (cast<CallInst>(Call)->isTailCall())
719 cast<CallInst>(New)->setTailCall();
722 AttributesVec.clear();
724 // Update the alias analysis implementation to know that we are replacing
725 // the old call with a new one.
726 AA.replaceWithNewValue(Call, New);
728 // Update the callgraph to know that the callsite has been transformed.
729 CallGraphNode *CalleeNode = CG[Call->getParent()->getParent()];
730 CalleeNode->replaceCallEdge(Call, New, NF_CGN);
732 if (!Call->use_empty()) {
733 Call->replaceAllUsesWith(New);
737 // Finally, remove the old call from the program, reducing the use-count of
739 Call->eraseFromParent();
742 // Since we have now created the new function, splice the body of the old
743 // function right into the new function, leaving the old rotting hulk of the
745 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
747 // Loop over the argument list, transfering uses of the old arguments over to
748 // the new arguments, also transfering over the names as well.
750 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
751 I2 = NF->arg_begin(); I != E; ++I) {
752 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
753 // If this is an unmodified argument, move the name and users over to the
755 I->replaceAllUsesWith(I2);
757 AA.replaceWithNewValue(I, I2);
762 if (ByValArgsToTransform.count(I)) {
763 // In the callee, we create an alloca, and store each of the new incoming
764 // arguments into the alloca.
765 Instruction *InsertPt = NF->begin()->begin();
767 // Just add all the struct element types.
768 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
769 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
770 const StructType *STy = cast<StructType>(AgTy);
772 ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
774 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
775 Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
777 GetElementPtrInst::Create(TheAlloca, Idxs, Idxs+2,
778 TheAlloca->getName()+"."+Twine(i),
780 I2->setName(I->getName()+"."+Twine(i));
781 new StoreInst(I2++, Idx, InsertPt);
784 // Anything that used the arg should now use the alloca.
785 I->replaceAllUsesWith(TheAlloca);
786 TheAlloca->takeName(I);
787 AA.replaceWithNewValue(I, TheAlloca);
791 if (I->use_empty()) {
796 // Otherwise, if we promoted this argument, then all users are load
797 // instructions (or GEPs with only load users), and all loads should be
798 // using the new argument that we added.
799 ScalarizeTable &ArgIndices = ScalarizedElements[I];
801 while (!I->use_empty()) {
802 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
803 assert(ArgIndices.begin()->empty() &&
804 "Load element should sort to front!");
805 I2->setName(I->getName()+".val");
806 LI->replaceAllUsesWith(I2);
807 AA.replaceWithNewValue(LI, I2);
808 LI->eraseFromParent();
809 DEBUG(dbgs() << "*** Promoted load of argument '" << I->getName()
810 << "' in function '" << F->getName() << "'\n");
812 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
813 IndicesVector Operands;
814 Operands.reserve(GEP->getNumIndices());
815 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
817 Operands.push_back(cast<ConstantInt>(*II)->getSExtValue());
819 // GEPs with a single 0 index can be merged with direct loads
820 if (Operands.size() == 1 && Operands.front() == 0)
823 Function::arg_iterator TheArg = I2;
824 for (ScalarizeTable::iterator It = ArgIndices.begin();
825 *It != Operands; ++It, ++TheArg) {
826 assert(It != ArgIndices.end() && "GEP not handled??");
829 std::string NewName = I->getName();
830 for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
831 NewName += "." + utostr(Operands[i]);
834 TheArg->setName(NewName);
836 DEBUG(dbgs() << "*** Promoted agg argument '" << TheArg->getName()
837 << "' of function '" << NF->getName() << "'\n");
839 // All of the uses must be load instructions. Replace them all with
840 // the argument specified by ArgNo.
841 while (!GEP->use_empty()) {
842 LoadInst *L = cast<LoadInst>(GEP->use_back());
843 L->replaceAllUsesWith(TheArg);
844 AA.replaceWithNewValue(L, TheArg);
845 L->eraseFromParent();
848 GEP->eraseFromParent();
852 // Increment I2 past all of the arguments added for this promoted pointer.
853 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
857 // Notify the alias analysis implementation that we inserted a new argument.
859 AA.copyValue(Constant::getNullValue(Type::getInt32Ty(F->getContext())),
863 // Tell the alias analysis that the old function is about to disappear.
864 AA.replaceWithNewValue(F, NF);
867 NF_CGN->stealCalledFunctionsFrom(CG[F]);
869 // Now that the old function is dead, delete it. If there is a dangling
870 // reference to the CallgraphNode, just leave the dead function around for
871 // someone else to nuke.
872 CallGraphNode *CGN = CG[F];
873 if (CGN->getNumReferences() == 0)
874 delete CG.removeFunctionFromModule(CGN);
876 F->setLinkage(Function::ExternalLinkage);