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/Analysis/AliasAnalysis.h"
40 #include "llvm/Analysis/CallGraph.h"
41 #include "llvm/Target/TargetData.h"
42 #include "llvm/Support/CallSite.h"
43 #include "llvm/Support/CFG.h"
44 #include "llvm/Support/Debug.h"
45 #include "llvm/ADT/DepthFirstIterator.h"
46 #include "llvm/ADT/Statistic.h"
47 #include "llvm/ADT/StringExtras.h"
48 #include "llvm/Support/Compiler.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 VISIBILITY_HIDDEN ArgPromotion : public CallGraphSCCPass {
61 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
62 AU.addRequired<AliasAnalysis>();
63 AU.addRequired<TargetData>();
64 CallGraphSCCPass::getAnalysisUsage(AU);
67 virtual bool runOnSCC(const std::vector<CallGraphNode *> &SCC);
68 static char ID; // Pass identification, replacement for typeid
69 explicit ArgPromotion(unsigned maxElements = 3)
70 : CallGraphSCCPass(&ID), maxElements(maxElements) {}
72 /// A vector used to hold the indices of a single GEP instruction
73 typedef std::vector<uint64_t> IndicesVector;
76 bool PromoteArguments(CallGraphNode *CGN);
77 bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const;
78 Function *DoPromotion(Function *F,
79 SmallPtrSet<Argument*, 8> &ArgsToPromote,
80 SmallPtrSet<Argument*, 8> &ByValArgsToTransform);
81 /// The maximum number of elements to expand, or 0 for unlimited.
86 char ArgPromotion::ID = 0;
87 static RegisterPass<ArgPromotion>
88 X("argpromotion", "Promote 'by reference' arguments to scalars");
90 Pass *llvm::createArgumentPromotionPass(unsigned maxElements) {
91 return new ArgPromotion(maxElements);
94 bool ArgPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
95 bool Changed = false, LocalChange;
97 do { // Iterate until we stop promoting from this SCC.
99 // Attempt to promote arguments from all functions in this SCC.
100 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
101 LocalChange |= PromoteArguments(SCC[i]);
102 Changed |= LocalChange; // Remember that we changed something.
103 } while (LocalChange);
108 /// PromoteArguments - This method checks the specified function to see if there
109 /// are any promotable arguments and if it is safe to promote the function (for
110 /// example, all callers are direct). If safe to promote some arguments, it
111 /// calls the DoPromotion method.
113 bool ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
114 Function *F = CGN->getFunction();
116 // Make sure that it is local to this module.
117 if (!F || !F->hasLocalLinkage()) return false;
119 // First check: see if there are any pointer arguments! If not, quick exit.
120 SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs;
122 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
123 I != E; ++I, ++ArgNo)
124 if (isa<PointerType>(I->getType()))
125 PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo));
126 if (PointerArgs.empty()) return false;
128 // Second check: make sure that all callers are direct callers. We can't
129 // transform functions that have indirect callers.
130 if (F->hasAddressTaken())
133 // Check to see which arguments are promotable. If an argument is promotable,
134 // add it to ArgsToPromote.
135 SmallPtrSet<Argument*, 8> ArgsToPromote;
136 SmallPtrSet<Argument*, 8> ByValArgsToTransform;
137 for (unsigned i = 0; i != PointerArgs.size(); ++i) {
138 bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, Attribute::ByVal);
140 // If this is a byval argument, and if the aggregate type is small, just
141 // pass the elements, which is always safe.
142 Argument *PtrArg = PointerArgs[i].first;
144 const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
145 if (const StructType *STy = dyn_cast<StructType>(AgTy)) {
146 if (maxElements > 0 && STy->getNumElements() > maxElements) {
147 DOUT << "argpromotion disable promoting argument '"
148 << PtrArg->getName() << "' because it would require adding more "
149 << "than " << maxElements << " arguments to the function.\n";
151 // If all the elements are single-value types, we can promote it.
152 bool AllSimple = true;
153 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
154 if (!STy->getElementType(i)->isSingleValueType()) {
159 // Safe to transform, don't even bother trying to "promote" it.
160 // Passing the elements as a scalar will allow scalarrepl to hack on
161 // the new alloca we introduce.
163 ByValArgsToTransform.insert(PtrArg);
170 // Otherwise, see if we can promote the pointer to its value.
171 if (isSafeToPromoteArgument(PtrArg, isByVal))
172 ArgsToPromote.insert(PtrArg);
175 // No promotable pointer arguments.
176 if (ArgsToPromote.empty() && ByValArgsToTransform.empty()) return false;
178 Function *NewF = DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
180 // Update the call graph to know that the function has been transformed.
181 getAnalysis<CallGraph>().changeFunction(F, NewF);
185 /// IsAlwaysValidPointer - Return true if the specified pointer is always legal
187 static bool IsAlwaysValidPointer(Value *V) {
188 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
189 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V))
190 return IsAlwaysValidPointer(GEP->getOperand(0));
191 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
192 if (CE->getOpcode() == Instruction::GetElementPtr)
193 return IsAlwaysValidPointer(CE->getOperand(0));
198 /// AllCalleesPassInValidPointerForArgument - Return true if we can prove that
199 /// all callees pass in a valid pointer for the specified function argument.
200 static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
201 Function *Callee = Arg->getParent();
203 unsigned ArgNo = std::distance(Callee->arg_begin(),
204 Function::arg_iterator(Arg));
206 // Look at all call sites of the function. At this pointer we know we only
207 // have direct callees.
208 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
210 CallSite CS = CallSite::get(*UI);
211 assert(CS.getInstruction() && "Should only have direct calls!");
213 if (!IsAlwaysValidPointer(CS.getArgument(ArgNo)))
219 /// Returns true if Prefix is a prefix of longer. That means, Longer has a size
220 /// that is greater than or equal to the size of prefix, and each of the
221 /// elements in Prefix is the same as the corresponding elements in Longer.
223 /// This means it also returns true when Prefix and Longer are equal!
224 static bool IsPrefix(const ArgPromotion::IndicesVector &Prefix,
225 const ArgPromotion::IndicesVector &Longer) {
226 if (Prefix.size() > Longer.size())
228 for (unsigned i = 0, e = Prefix.size(); i != e; ++i)
229 if (Prefix[i] != Longer[i])
235 /// Checks if Indices, or a prefix of Indices, is in Set.
236 static bool PrefixIn(const ArgPromotion::IndicesVector &Indices,
237 std::set<ArgPromotion::IndicesVector> &Set) {
238 std::set<ArgPromotion::IndicesVector>::iterator Low;
239 Low = Set.upper_bound(Indices);
240 if (Low != Set.begin())
242 // Low is now the last element smaller than or equal to Indices. This means
243 // it points to a prefix of Indices (possibly Indices itself), if such
246 // This load is safe if any prefix of its operands is safe to load.
247 return Low != Set.end() && IsPrefix(*Low, Indices);
250 /// Mark the given indices (ToMark) as safe in the the given set of indices
251 /// (Safe). Marking safe usually means adding ToMark to Safe. However, if there
252 /// is already a prefix of Indices in Safe, Indices are implicitely marked safe
253 /// already. Furthermore, any indices that Indices is itself a prefix of, are
254 /// removed from Safe (since they are implicitely safe because of Indices now).
255 static void MarkIndicesSafe(const ArgPromotion::IndicesVector &ToMark,
256 std::set<ArgPromotion::IndicesVector> &Safe) {
257 std::set<ArgPromotion::IndicesVector>::iterator Low;
258 Low = Safe.upper_bound(ToMark);
259 // Guard against the case where Safe is empty
260 if (Low != Safe.begin())
262 // Low is now the last element smaller than or equal to Indices. This
263 // means it points to a prefix of Indices (possibly Indices itself), if
264 // such prefix exists.
265 if (Low != Safe.end()) {
266 if (IsPrefix(*Low, ToMark))
267 // If there is already a prefix of these indices (or exactly these
268 // indices) marked a safe, don't bother adding these indices
271 // Increment Low, so we can use it as a "insert before" hint
275 Low = Safe.insert(Low, ToMark);
277 // If there we're a prefix of longer index list(s), remove those
278 std::set<ArgPromotion::IndicesVector>::iterator End = Safe.end();
279 while (Low != End && IsPrefix(ToMark, *Low)) {
280 std::set<ArgPromotion::IndicesVector>::iterator Remove = Low;
286 /// isSafeToPromoteArgument - As you might guess from the name of this method,
287 /// it checks to see if it is both safe and useful to promote the argument.
288 /// This method limits promotion of aggregates to only promote up to three
289 /// elements of the aggregate in order to avoid exploding the number of
290 /// arguments passed in.
291 bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
292 typedef std::set<IndicesVector> GEPIndicesSet;
294 // Quick exit for unused arguments
295 if (Arg->use_empty())
298 // We can only promote this argument if all of the uses are loads, or are GEP
299 // instructions (with constant indices) that are subsequently loaded.
301 // Promoting the argument causes it to be loaded in the caller
302 // unconditionally. This is only safe if we can prove that either the load
303 // would have happened in the callee anyway (ie, there is a load in the entry
304 // block) or the pointer passed in at every call site is guaranteed to be
306 // In the former case, invalid loads can happen, but would have happened
307 // anyway, in the latter case, invalid loads won't happen. This prevents us
308 // from introducing an invalid load that wouldn't have happened in the
311 // This set will contain all sets of indices that are loaded in the entry
312 // block, and thus are safe to unconditionally load in the caller.
313 GEPIndicesSet SafeToUnconditionallyLoad;
315 // This set contains all the sets of indices that we are planning to promote.
316 // This makes it possible to limit the number of arguments added.
317 GEPIndicesSet ToPromote;
319 // If the pointer is always valid, any load with first index 0 is valid.
320 if(isByVal || AllCalleesPassInValidPointerForArgument(Arg))
321 SafeToUnconditionallyLoad.insert(IndicesVector(1, 0));
323 // First, iterate the entry block and mark loads of (geps of) arguments as
325 BasicBlock *EntryBlock = Arg->getParent()->begin();
326 // Declare this here so we can reuse it
327 IndicesVector Indices;
328 for (BasicBlock::iterator I = EntryBlock->begin(), E = EntryBlock->end();
330 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
331 Value *V = LI->getPointerOperand();
332 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
333 V = GEP->getPointerOperand();
335 // This load actually loads (part of) Arg? Check the indices then.
336 Indices.reserve(GEP->getNumIndices());
337 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
339 if (ConstantInt *CI = dyn_cast<ConstantInt>(*II))
340 Indices.push_back(CI->getSExtValue());
342 // We found a non-constant GEP index for this argument? Bail out
343 // right away, can't promote this argument at all.
346 // Indices checked out, mark them as safe
347 MarkIndicesSafe(Indices, SafeToUnconditionallyLoad);
350 } else if (V == Arg) {
351 // Direct loads are equivalent to a GEP with a single 0 index.
352 MarkIndicesSafe(IndicesVector(1, 0), SafeToUnconditionallyLoad);
356 // Now, iterate all uses of the argument to see if there are any uses that are
357 // not (GEP+)loads, or any (GEP+)loads that are not safe to promote.
358 SmallVector<LoadInst*, 16> Loads;
359 IndicesVector Operands;
360 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
363 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
364 if (LI->isVolatile()) return false; // Don't hack volatile loads
366 // Direct loads are equivalent to a GEP with a zero index and then a load.
367 Operands.push_back(0);
368 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
369 if (GEP->use_empty()) {
370 // Dead GEP's cause trouble later. Just remove them if we run into
372 getAnalysis<AliasAnalysis>().deleteValue(GEP);
373 GEP->eraseFromParent();
374 // TODO: This runs the above loop over and over again for dead GEPS
375 // Couldn't we just do increment the UI iterator earlier and erase the
377 return isSafeToPromoteArgument(Arg, isByVal);
380 // Ensure that all of the indices are constants.
381 for (User::op_iterator i = GEP->idx_begin(), e = GEP->idx_end();
383 if (ConstantInt *C = dyn_cast<ConstantInt>(*i))
384 Operands.push_back(C->getSExtValue());
386 return false; // Not a constant operand GEP!
388 // Ensure that the only users of the GEP are load instructions.
389 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
391 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
392 if (LI->isVolatile()) return false; // Don't hack volatile loads
395 // Other uses than load?
399 return false; // Not a load or a GEP.
402 // Now, see if it is safe to promote this load / loads of this GEP. Loading
403 // is safe if Operands, or a prefix of Operands, is marked as safe.
404 if (!PrefixIn(Operands, SafeToUnconditionallyLoad))
407 // See if we are already promoting a load with these indices. If not, check
408 // to make sure that we aren't promoting too many elements. If so, nothing
410 if (ToPromote.find(Operands) == ToPromote.end()) {
411 if (maxElements > 0 && ToPromote.size() == maxElements) {
412 DOUT << "argpromotion not promoting argument '"
413 << Arg->getName() << "' because it would require adding more "
414 << "than " << maxElements << " arguments to the function.\n";
415 // We limit aggregate promotion to only promoting up to a fixed number
416 // of elements of the aggregate.
419 ToPromote.insert(Operands);
423 if (Loads.empty()) return true; // No users, this is a dead argument.
425 // Okay, now we know that the argument is only used by load instructions and
426 // it is safe to unconditionally perform all of them. Use alias analysis to
427 // check to see if the pointer is guaranteed to not be modified from entry of
428 // the function to each of the load instructions.
430 // Because there could be several/many load instructions, remember which
431 // blocks we know to be transparent to the load.
432 SmallPtrSet<BasicBlock*, 16> TranspBlocks;
434 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
435 TargetData &TD = getAnalysis<TargetData>();
437 for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
438 // Check to see if the load is invalidated from the start of the block to
440 LoadInst *Load = Loads[i];
441 BasicBlock *BB = Load->getParent();
443 const PointerType *LoadTy =
444 cast<PointerType>(Load->getPointerOperand()->getType());
445 unsigned LoadSize = (unsigned)TD.getTypeStoreSize(LoadTy->getElementType());
447 if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize))
448 return false; // Pointer is invalidated!
450 // Now check every path from the entry block to the load for transparency.
451 // To do this, we perform a depth first search on the inverse CFG from the
453 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
454 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
455 I = idf_ext_begin(*PI, TranspBlocks),
456 E = idf_ext_end(*PI, TranspBlocks); I != E; ++I)
457 if (AA.canBasicBlockModify(**I, Arg, LoadSize))
461 // If the path from the entry of the function to each load is free of
462 // instructions that potentially invalidate the load, we can make the
467 /// DoPromotion - This method actually performs the promotion of the specified
468 /// arguments, and returns the new function. At this point, we know that it's
470 Function *ArgPromotion::DoPromotion(Function *F,
471 SmallPtrSet<Argument*, 8> &ArgsToPromote,
472 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
474 // Start by computing a new prototype for the function, which is the same as
475 // the old function, but has modified arguments.
476 const FunctionType *FTy = F->getFunctionType();
477 std::vector<const Type*> Params;
479 typedef std::set<IndicesVector> ScalarizeTable;
481 // ScalarizedElements - If we are promoting a pointer that has elements
482 // accessed out of it, keep track of which elements are accessed so that we
483 // can add one argument for each.
485 // Arguments that are directly loaded will have a zero element value here, to
486 // handle cases where there are both a direct load and GEP accesses.
488 std::map<Argument*, ScalarizeTable> ScalarizedElements;
490 // OriginalLoads - Keep track of a representative load instruction from the
491 // original function so that we can tell the alias analysis implementation
492 // what the new GEP/Load instructions we are inserting look like.
493 std::map<IndicesVector, LoadInst*> OriginalLoads;
495 // Attributes - Keep track of the parameter attributes for the arguments
496 // that we are *not* promoting. For the ones that we do promote, the parameter
497 // attributes are lost
498 SmallVector<AttributeWithIndex, 8> AttributesVec;
499 const AttrListPtr &PAL = F->getAttributes();
501 // Add any return attributes.
502 if (Attributes attrs = PAL.getRetAttributes())
503 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
505 // First, determine the new argument list
506 unsigned ArgIndex = 1;
507 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
509 if (ByValArgsToTransform.count(I)) {
510 // Simple byval argument? Just add all the struct element types.
511 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
512 const StructType *STy = cast<StructType>(AgTy);
513 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
514 Params.push_back(STy->getElementType(i));
515 ++NumByValArgsPromoted;
516 } else if (!ArgsToPromote.count(I)) {
517 // Unchanged argument
518 Params.push_back(I->getType());
519 if (Attributes attrs = PAL.getParamAttributes(ArgIndex))
520 AttributesVec.push_back(AttributeWithIndex::get(Params.size(), attrs));
521 } else if (I->use_empty()) {
522 // Dead argument (which are always marked as promotable)
525 // Okay, this is being promoted. This means that the only uses are loads
526 // or GEPs which are only used by loads
528 // In this table, we will track which indices are loaded from the argument
529 // (where direct loads are tracked as no indices).
530 ScalarizeTable &ArgIndices = ScalarizedElements[I];
531 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
533 Instruction *User = cast<Instruction>(*UI);
534 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
535 IndicesVector Indices;
536 Indices.reserve(User->getNumOperands() - 1);
537 // Since loads will only have a single operand, and GEPs only a single
538 // non-index operand, this will record direct loads without any indices,
539 // and gep+loads with the GEP indices.
540 for (User::op_iterator II = User->op_begin() + 1, IE = User->op_end();
542 Indices.push_back(cast<ConstantInt>(*II)->getSExtValue());
543 // GEPs with a single 0 index can be merged with direct loads
544 if (Indices.size() == 1 && Indices.front() == 0)
546 ArgIndices.insert(Indices);
548 if (LoadInst *L = dyn_cast<LoadInst>(User))
551 // Take any load, we will use it only to update Alias Analysis
552 OrigLoad = cast<LoadInst>(User->use_back());
553 OriginalLoads[Indices] = OrigLoad;
556 // Add a parameter to the function for each element passed in.
557 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
558 E = ArgIndices.end(); SI != E; ++SI) {
559 // not allowed to dereference ->begin() if size() is 0
560 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(),
563 assert(Params.back());
566 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
567 ++NumArgumentsPromoted;
569 ++NumAggregatesPromoted;
573 // Add any function attributes.
574 if (Attributes attrs = PAL.getFnAttributes())
575 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
577 const Type *RetTy = FTy->getReturnType();
579 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
580 // have zero fixed arguments.
581 bool ExtraArgHack = false;
582 if (Params.empty() && FTy->isVarArg()) {
584 Params.push_back(Type::Int32Ty);
587 // Construct the new function type using the new arguments.
588 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
590 // Create the new function body and insert it into the module...
591 Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
592 NF->copyAttributesFrom(F);
594 // Recompute the parameter attributes list based on the new arguments for
596 NF->setAttributes(AttrListPtr::get(AttributesVec.begin(), AttributesVec.end()));
597 AttributesVec.clear();
599 F->getParent()->getFunctionList().insert(F, NF);
602 // Get the alias analysis information that we need to update to reflect our
604 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
606 // Get the callgraph information that we need to update to reflect our
608 CallGraph &CG = getAnalysis<CallGraph>();
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 = CallSite::get(F->use_back());
616 Instruction *Call = CS.getInstruction();
617 const AttrListPtr &CallPAL = CS.getAttributes();
619 // Add any return attributes.
620 if (Attributes attrs = CallPAL.getRetAttributes())
621 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
623 // Loop over the operands, inserting GEP and loads in the caller as
625 CallSite::arg_iterator AI = CS.arg_begin();
627 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
628 I != E; ++I, ++AI, ++ArgIndex)
629 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
630 Args.push_back(*AI); // Unmodified argument
632 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
633 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
635 } else if (ByValArgsToTransform.count(I)) {
636 // Emit a GEP and load for each element of the struct.
637 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
638 const StructType *STy = cast<StructType>(AgTy);
639 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
640 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
641 Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
642 Value *Idx = GetElementPtrInst::Create(*AI, Idxs, Idxs+2,
643 (*AI)->getName()+"."+utostr(i),
645 // TODO: Tell AA about the new values?
646 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
648 } else if (!I->use_empty()) {
649 // Non-dead argument: insert GEPs and loads as appropriate.
650 ScalarizeTable &ArgIndices = ScalarizedElements[I];
651 // Store the Value* version of the indices in here, but declare it now
653 std::vector<Value*> Ops;
654 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
655 E = ArgIndices.end(); SI != E; ++SI) {
657 LoadInst *OrigLoad = OriginalLoads[*SI];
659 Ops.reserve(SI->size());
660 const Type *ElTy = V->getType();
661 for (IndicesVector::const_iterator II = SI->begin(),
662 IE = SI->end(); II != IE; ++II) {
663 // Use i32 to index structs, and i64 for others (pointers/arrays).
664 // This satisfies GEP constraints.
665 const Type *IdxTy = (isa<StructType>(ElTy) ? Type::Int32Ty : Type::Int64Ty);
666 Ops.push_back(ConstantInt::get(IdxTy, *II));
667 // Keep track of the type we're currently indexing
668 ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(*II);
670 // And create a GEP to extract those indices
671 V = GetElementPtrInst::Create(V, Ops.begin(), Ops.end(),
672 V->getName()+".idx", Call);
674 AA.copyValue(OrigLoad->getOperand(0), V);
676 Args.push_back(new LoadInst(V, V->getName()+".val", Call));
677 AA.copyValue(OrigLoad, Args.back());
682 Args.push_back(Constant::getNullValue(Type::Int32Ty));
684 // Push any varargs arguments on the list
685 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
687 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
688 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
691 // Add any function attributes.
692 if (Attributes attrs = CallPAL.getFnAttributes())
693 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
696 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
697 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
698 Args.begin(), Args.end(), "", Call);
699 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
700 cast<InvokeInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
701 AttributesVec.end()));
703 New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
704 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
705 cast<CallInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
706 AttributesVec.end()));
707 if (cast<CallInst>(Call)->isTailCall())
708 cast<CallInst>(New)->setTailCall();
711 AttributesVec.clear();
713 // Update the alias analysis implementation to know that we are replacing
714 // the old call with a new one.
715 AA.replaceWithNewValue(Call, New);
717 // Update the callgraph to know that the callsite has been transformed.
718 CG[Call->getParent()->getParent()]->replaceCallSite(Call, New);
720 if (!Call->use_empty()) {
721 Call->replaceAllUsesWith(New);
725 // Finally, remove the old call from the program, reducing the use-count of
727 Call->eraseFromParent();
730 // Since we have now created the new function, splice the body of the old
731 // function right into the new function, leaving the old rotting hulk of the
733 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
735 // Loop over the argument list, transfering uses of the old arguments over to
736 // the new arguments, also transfering over the names as well.
738 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
739 I2 = NF->arg_begin(); I != E; ++I) {
740 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
741 // If this is an unmodified argument, move the name and users over to the
743 I->replaceAllUsesWith(I2);
745 AA.replaceWithNewValue(I, I2);
750 if (ByValArgsToTransform.count(I)) {
751 // In the callee, we create an alloca, and store each of the new incoming
752 // arguments into the alloca.
753 Instruction *InsertPt = NF->begin()->begin();
755 // Just add all the struct element types.
756 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
757 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
758 const StructType *STy = cast<StructType>(AgTy);
759 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
761 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
762 Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
763 std::string Name = TheAlloca->getName()+"."+utostr(i);
764 Value *Idx = GetElementPtrInst::Create(TheAlloca, Idxs, Idxs+2,
766 I2->setName(I->getName()+"."+utostr(i));
767 new StoreInst(I2++, Idx, InsertPt);
770 // Anything that used the arg should now use the alloca.
771 I->replaceAllUsesWith(TheAlloca);
772 TheAlloca->takeName(I);
773 AA.replaceWithNewValue(I, TheAlloca);
777 if (I->use_empty()) {
782 // Otherwise, if we promoted this argument, then all users are load
783 // instructions (or GEPs with only load users), and all loads should be
784 // using the new argument that we added.
785 ScalarizeTable &ArgIndices = ScalarizedElements[I];
787 while (!I->use_empty()) {
788 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
789 assert(ArgIndices.begin()->empty() &&
790 "Load element should sort to front!");
791 I2->setName(I->getName()+".val");
792 LI->replaceAllUsesWith(I2);
793 AA.replaceWithNewValue(LI, I2);
794 LI->eraseFromParent();
795 DOUT << "*** Promoted load of argument '" << I->getName()
796 << "' in function '" << F->getName() << "'\n";
798 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
799 IndicesVector Operands;
800 Operands.reserve(GEP->getNumIndices());
801 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
803 Operands.push_back(cast<ConstantInt>(*II)->getSExtValue());
805 // GEPs with a single 0 index can be merged with direct loads
806 if (Operands.size() == 1 && Operands.front() == 0)
809 Function::arg_iterator TheArg = I2;
810 for (ScalarizeTable::iterator It = ArgIndices.begin();
811 *It != Operands; ++It, ++TheArg) {
812 assert(It != ArgIndices.end() && "GEP not handled??");
815 std::string NewName = I->getName();
816 for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
817 NewName += "." + utostr(Operands[i]);
820 TheArg->setName(NewName);
822 DOUT << "*** Promoted agg argument '" << TheArg->getName()
823 << "' of function '" << NF->getName() << "'\n";
825 // All of the uses must be load instructions. Replace them all with
826 // the argument specified by ArgNo.
827 while (!GEP->use_empty()) {
828 LoadInst *L = cast<LoadInst>(GEP->use_back());
829 L->replaceAllUsesWith(TheArg);
830 AA.replaceWithNewValue(L, TheArg);
831 L->eraseFromParent();
834 GEP->eraseFromParent();
838 // Increment I2 past all of the arguments added for this promoted pointer.
839 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
843 // Notify the alias analysis implementation that we inserted a new argument.
845 AA.copyValue(Constant::getNullValue(Type::Int32Ty), NF->arg_begin());
848 // Tell the alias analysis that the old function is about to disappear.
849 AA.replaceWithNewValue(F, NF);
851 // Now that the old function is dead, delete it.
852 F->eraseFromParent();