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/Target/TargetData.h"
43 #include "llvm/Support/CallSite.h"
44 #include "llvm/Support/CFG.h"
45 #include "llvm/Support/Debug.h"
46 #include "llvm/ADT/DepthFirstIterator.h"
47 #include "llvm/ADT/Statistic.h"
48 #include "llvm/ADT/StringExtras.h"
49 #include "llvm/Support/Compiler.h"
53 STATISTIC(NumArgumentsPromoted , "Number of pointer arguments promoted");
54 STATISTIC(NumAggregatesPromoted, "Number of aggregate arguments promoted");
55 STATISTIC(NumByValArgsPromoted , "Number of byval arguments promoted");
56 STATISTIC(NumArgumentsDead , "Number of dead pointer args eliminated");
59 /// ArgPromotion - The 'by reference' to 'by value' argument promotion pass.
61 struct VISIBILITY_HIDDEN ArgPromotion : public CallGraphSCCPass {
62 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
63 AU.addRequired<AliasAnalysis>();
64 AU.addRequired<TargetData>();
65 CallGraphSCCPass::getAnalysisUsage(AU);
68 virtual bool runOnSCC(const std::vector<CallGraphNode *> &SCC);
69 static char ID; // Pass identification, replacement for typeid
70 explicit ArgPromotion(unsigned maxElements = 3)
71 : CallGraphSCCPass(&ID), maxElements(maxElements) {}
73 /// A vector used to hold the indices of a single GEP instruction
74 typedef std::vector<uint64_t> IndicesVector;
77 bool PromoteArguments(CallGraphNode *CGN);
78 bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const;
79 Function *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 static RegisterPass<ArgPromotion>
89 X("argpromotion", "Promote 'by reference' arguments to scalars");
91 Pass *llvm::createArgumentPromotionPass(unsigned maxElements) {
92 return new ArgPromotion(maxElements);
95 bool ArgPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
96 bool Changed = false, LocalChange;
98 do { // Iterate until we stop promoting from this SCC.
100 // Attempt to promote arguments from all functions in this SCC.
101 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
102 LocalChange |= PromoteArguments(SCC[i]);
103 Changed |= LocalChange; // Remember that we changed something.
104 } while (LocalChange);
109 /// PromoteArguments - This method checks the specified function to see if there
110 /// are any promotable arguments and if it is safe to promote the function (for
111 /// example, all callers are direct). If safe to promote some arguments, it
112 /// calls the DoPromotion method.
114 bool ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
115 Function *F = CGN->getFunction();
117 // Make sure that it is local to this module.
118 if (!F || !F->hasLocalLinkage()) return false;
120 // First check: see if there are any pointer arguments! If not, quick exit.
121 SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs;
123 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
124 I != E; ++I, ++ArgNo)
125 if (isa<PointerType>(I->getType()))
126 PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo));
127 if (PointerArgs.empty()) return false;
129 // Second check: make sure that all callers are direct callers. We can't
130 // transform functions that have indirect callers.
131 if (F->hasAddressTaken())
134 // Check to see which arguments are promotable. If an argument is promotable,
135 // add it to ArgsToPromote.
136 SmallPtrSet<Argument*, 8> ArgsToPromote;
137 SmallPtrSet<Argument*, 8> ByValArgsToTransform;
138 for (unsigned i = 0; i != PointerArgs.size(); ++i) {
139 bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, Attribute::ByVal);
141 // If this is a byval argument, and if the aggregate type is small, just
142 // pass the elements, which is always safe.
143 Argument *PtrArg = PointerArgs[i].first;
145 const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
146 if (const StructType *STy = dyn_cast<StructType>(AgTy)) {
147 if (maxElements > 0 && STy->getNumElements() > maxElements) {
148 DOUT << "argpromotion disable promoting argument '"
149 << PtrArg->getName() << "' because it would require adding more "
150 << "than " << maxElements << " arguments to the function.\n";
152 // If all the elements are single-value types, we can promote it.
153 bool AllSimple = true;
154 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
155 if (!STy->getElementType(i)->isSingleValueType()) {
160 // Safe to transform, don't even bother trying to "promote" it.
161 // Passing the elements as a scalar will allow scalarrepl to hack on
162 // the new alloca we introduce.
164 ByValArgsToTransform.insert(PtrArg);
171 // Otherwise, see if we can promote the pointer to its value.
172 if (isSafeToPromoteArgument(PtrArg, isByVal))
173 ArgsToPromote.insert(PtrArg);
176 // No promotable pointer arguments.
177 if (ArgsToPromote.empty() && ByValArgsToTransform.empty()) return false;
179 Function *NewF = DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
181 // Update the call graph to know that the function has been transformed.
182 getAnalysis<CallGraph>().changeFunction(F, NewF);
186 /// IsAlwaysValidPointer - Return true if the specified pointer is always legal
188 static bool IsAlwaysValidPointer(Value *V) {
189 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
190 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V))
191 return IsAlwaysValidPointer(GEP->getOperand(0));
192 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
193 if (CE->getOpcode() == Instruction::GetElementPtr)
194 return IsAlwaysValidPointer(CE->getOperand(0));
199 /// AllCalleesPassInValidPointerForArgument - Return true if we can prove that
200 /// all callees pass in a valid pointer for the specified function argument.
201 static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
202 Function *Callee = Arg->getParent();
204 unsigned ArgNo = std::distance(Callee->arg_begin(),
205 Function::arg_iterator(Arg));
207 // Look at all call sites of the function. At this pointer we know we only
208 // have direct callees.
209 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
211 CallSite CS = CallSite::get(*UI);
212 assert(CS.getInstruction() && "Should only have direct calls!");
214 if (!IsAlwaysValidPointer(CS.getArgument(ArgNo)))
220 /// Returns true if Prefix is a prefix of longer. That means, Longer has a size
221 /// that is greater than or equal to the size of prefix, and each of the
222 /// elements in Prefix is the same as the corresponding elements in Longer.
224 /// This means it also returns true when Prefix and Longer are equal!
225 static bool IsPrefix(const ArgPromotion::IndicesVector &Prefix,
226 const ArgPromotion::IndicesVector &Longer) {
227 if (Prefix.size() > Longer.size())
229 for (unsigned i = 0, e = Prefix.size(); i != e; ++i)
230 if (Prefix[i] != Longer[i])
236 /// Checks if Indices, or a prefix of Indices, is in Set.
237 static bool PrefixIn(const ArgPromotion::IndicesVector &Indices,
238 std::set<ArgPromotion::IndicesVector> &Set) {
239 std::set<ArgPromotion::IndicesVector>::iterator Low;
240 Low = Set.upper_bound(Indices);
241 if (Low != Set.begin())
243 // Low is now the last element smaller than or equal to Indices. This means
244 // it points to a prefix of Indices (possibly Indices itself), if such
247 // This load is safe if any prefix of its operands is safe to load.
248 return Low != Set.end() && IsPrefix(*Low, Indices);
251 /// Mark the given indices (ToMark) as safe in the the given set of indices
252 /// (Safe). Marking safe usually means adding ToMark to Safe. However, if there
253 /// is already a prefix of Indices in Safe, Indices are implicitely marked safe
254 /// already. Furthermore, any indices that Indices is itself a prefix of, are
255 /// removed from Safe (since they are implicitely safe because of Indices now).
256 static void MarkIndicesSafe(const ArgPromotion::IndicesVector &ToMark,
257 std::set<ArgPromotion::IndicesVector> &Safe) {
258 std::set<ArgPromotion::IndicesVector>::iterator Low;
259 Low = Safe.upper_bound(ToMark);
260 // Guard against the case where Safe is empty
261 if (Low != Safe.begin())
263 // Low is now the last element smaller than or equal to Indices. This
264 // means it points to a prefix of Indices (possibly Indices itself), if
265 // such prefix exists.
266 if (Low != Safe.end()) {
267 if (IsPrefix(*Low, ToMark))
268 // If there is already a prefix of these indices (or exactly these
269 // indices) marked a safe, don't bother adding these indices
272 // Increment Low, so we can use it as a "insert before" hint
276 Low = Safe.insert(Low, ToMark);
278 // If there we're a prefix of longer index list(s), remove those
279 std::set<ArgPromotion::IndicesVector>::iterator End = Safe.end();
280 while (Low != End && IsPrefix(ToMark, *Low)) {
281 std::set<ArgPromotion::IndicesVector>::iterator Remove = Low;
287 /// isSafeToPromoteArgument - As you might guess from the name of this method,
288 /// it checks to see if it is both safe and useful to promote the argument.
289 /// This method limits promotion of aggregates to only promote up to three
290 /// elements of the aggregate in order to avoid exploding the number of
291 /// arguments passed in.
292 bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
293 typedef std::set<IndicesVector> GEPIndicesSet;
295 // Quick exit for unused arguments
296 if (Arg->use_empty())
299 // We can only promote this argument if all of the uses are loads, or are GEP
300 // instructions (with constant indices) that are subsequently loaded.
302 // Promoting the argument causes it to be loaded in the caller
303 // unconditionally. This is only safe if we can prove that either the load
304 // would have happened in the callee anyway (ie, there is a load in the entry
305 // block) or the pointer passed in at every call site is guaranteed to be
307 // In the former case, invalid loads can happen, but would have happened
308 // anyway, in the latter case, invalid loads won't happen. This prevents us
309 // from introducing an invalid load that wouldn't have happened in the
312 // This set will contain all sets of indices that are loaded in the entry
313 // block, and thus are safe to unconditionally load in the caller.
314 GEPIndicesSet SafeToUnconditionallyLoad;
316 // This set contains all the sets of indices that we are planning to promote.
317 // This makes it possible to limit the number of arguments added.
318 GEPIndicesSet ToPromote;
320 // If the pointer is always valid, any load with first index 0 is valid.
321 if(isByVal || AllCalleesPassInValidPointerForArgument(Arg))
322 SafeToUnconditionallyLoad.insert(IndicesVector(1, 0));
324 // First, iterate the entry block and mark loads of (geps of) arguments as
326 BasicBlock *EntryBlock = Arg->getParent()->begin();
327 // Declare this here so we can reuse it
328 IndicesVector Indices;
329 for (BasicBlock::iterator I = EntryBlock->begin(), E = EntryBlock->end();
331 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
332 Value *V = LI->getPointerOperand();
333 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
334 V = GEP->getPointerOperand();
336 // This load actually loads (part of) Arg? Check the indices then.
337 Indices.reserve(GEP->getNumIndices());
338 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
340 if (ConstantInt *CI = dyn_cast<ConstantInt>(*II))
341 Indices.push_back(CI->getSExtValue());
343 // We found a non-constant GEP index for this argument? Bail out
344 // right away, can't promote this argument at all.
347 // Indices checked out, mark them as safe
348 MarkIndicesSafe(Indices, SafeToUnconditionallyLoad);
351 } else if (V == Arg) {
352 // Direct loads are equivalent to a GEP with a single 0 index.
353 MarkIndicesSafe(IndicesVector(1, 0), SafeToUnconditionallyLoad);
357 // Now, iterate all uses of the argument to see if there are any uses that are
358 // not (GEP+)loads, or any (GEP+)loads that are not safe to promote.
359 SmallVector<LoadInst*, 16> Loads;
360 IndicesVector Operands;
361 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
364 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
365 if (LI->isVolatile()) return false; // Don't hack volatile loads
367 // Direct loads are equivalent to a GEP with a zero index and then a load.
368 Operands.push_back(0);
369 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
370 if (GEP->use_empty()) {
371 // Dead GEP's cause trouble later. Just remove them if we run into
373 getAnalysis<AliasAnalysis>().deleteValue(GEP);
374 GEP->eraseFromParent();
375 // TODO: This runs the above loop over and over again for dead GEPS
376 // Couldn't we just do increment the UI iterator earlier and erase the
378 return isSafeToPromoteArgument(Arg, isByVal);
381 // Ensure that all of the indices are constants.
382 for (User::op_iterator i = GEP->idx_begin(), e = GEP->idx_end();
384 if (ConstantInt *C = dyn_cast<ConstantInt>(*i))
385 Operands.push_back(C->getSExtValue());
387 return false; // Not a constant operand GEP!
389 // Ensure that the only users of the GEP are load instructions.
390 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
392 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
393 if (LI->isVolatile()) return false; // Don't hack volatile loads
396 // Other uses than load?
400 return false; // Not a load or a GEP.
403 // Now, see if it is safe to promote this load / loads of this GEP. Loading
404 // is safe if Operands, or a prefix of Operands, is marked as safe.
405 if (!PrefixIn(Operands, SafeToUnconditionallyLoad))
408 // See if we are already promoting a load with these indices. If not, check
409 // to make sure that we aren't promoting too many elements. If so, nothing
411 if (ToPromote.find(Operands) == ToPromote.end()) {
412 if (maxElements > 0 && ToPromote.size() == maxElements) {
413 DOUT << "argpromotion not promoting argument '"
414 << Arg->getName() << "' because it would require adding more "
415 << "than " << maxElements << " arguments to the function.\n";
416 // We limit aggregate promotion to only promoting up to a fixed number
417 // of elements of the aggregate.
420 ToPromote.insert(Operands);
424 if (Loads.empty()) return true; // No users, this is a dead argument.
426 // Okay, now we know that the argument is only used by load instructions and
427 // it is safe to unconditionally perform all of them. Use alias analysis to
428 // check to see if the pointer is guaranteed to not be modified from entry of
429 // the function to each of the load instructions.
431 // Because there could be several/many load instructions, remember which
432 // blocks we know to be transparent to the load.
433 SmallPtrSet<BasicBlock*, 16> TranspBlocks;
435 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
436 TargetData &TD = getAnalysis<TargetData>();
438 for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
439 // Check to see if the load is invalidated from the start of the block to
441 LoadInst *Load = Loads[i];
442 BasicBlock *BB = Load->getParent();
444 const PointerType *LoadTy =
445 cast<PointerType>(Load->getPointerOperand()->getType());
446 unsigned LoadSize = (unsigned)TD.getTypeStoreSize(LoadTy->getElementType());
448 if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize))
449 return false; // Pointer is invalidated!
451 // Now check every path from the entry block to the load for transparency.
452 // To do this, we perform a depth first search on the inverse CFG from the
454 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
455 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
456 I = idf_ext_begin(*PI, TranspBlocks),
457 E = idf_ext_end(*PI, TranspBlocks); I != E; ++I)
458 if (AA.canBasicBlockModify(**I, Arg, LoadSize))
462 // If the path from the entry of the function to each load is free of
463 // instructions that potentially invalidate the load, we can make the
468 /// DoPromotion - This method actually performs the promotion of the specified
469 /// arguments, and returns the new function. At this point, we know that it's
471 Function *ArgPromotion::DoPromotion(Function *F,
472 SmallPtrSet<Argument*, 8> &ArgsToPromote,
473 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
475 // Start by computing a new prototype for the function, which is the same as
476 // the old function, but has modified arguments.
477 const FunctionType *FTy = F->getFunctionType();
478 std::vector<const Type*> Params;
480 typedef std::set<IndicesVector> ScalarizeTable;
482 // ScalarizedElements - If we are promoting a pointer that has elements
483 // accessed out of it, keep track of which elements are accessed so that we
484 // can add one argument for each.
486 // Arguments that are directly loaded will have a zero element value here, to
487 // handle cases where there are both a direct load and GEP accesses.
489 std::map<Argument*, ScalarizeTable> ScalarizedElements;
491 // OriginalLoads - Keep track of a representative load instruction from the
492 // original function so that we can tell the alias analysis implementation
493 // what the new GEP/Load instructions we are inserting look like.
494 std::map<IndicesVector, LoadInst*> OriginalLoads;
496 // Attributes - Keep track of the parameter attributes for the arguments
497 // that we are *not* promoting. For the ones that we do promote, the parameter
498 // attributes are lost
499 SmallVector<AttributeWithIndex, 8> AttributesVec;
500 const AttrListPtr &PAL = F->getAttributes();
502 // Add any return attributes.
503 if (Attributes attrs = PAL.getRetAttributes())
504 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
506 // First, determine the new argument list
507 unsigned ArgIndex = 1;
508 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
510 if (ByValArgsToTransform.count(I)) {
511 // Simple byval argument? Just add all the struct element types.
512 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
513 const StructType *STy = cast<StructType>(AgTy);
514 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
515 Params.push_back(STy->getElementType(i));
516 ++NumByValArgsPromoted;
517 } else if (!ArgsToPromote.count(I)) {
518 // Unchanged argument
519 Params.push_back(I->getType());
520 if (Attributes attrs = PAL.getParamAttributes(ArgIndex))
521 AttributesVec.push_back(AttributeWithIndex::get(Params.size(), attrs));
522 } else if (I->use_empty()) {
523 // Dead argument (which are always marked as promotable)
526 // Okay, this is being promoted. This means that the only uses are loads
527 // or GEPs which are only used by loads
529 // In this table, we will track which indices are loaded from the argument
530 // (where direct loads are tracked as no indices).
531 ScalarizeTable &ArgIndices = ScalarizedElements[I];
532 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
534 Instruction *User = cast<Instruction>(*UI);
535 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
536 IndicesVector Indices;
537 Indices.reserve(User->getNumOperands() - 1);
538 // Since loads will only have a single operand, and GEPs only a single
539 // non-index operand, this will record direct loads without any indices,
540 // and gep+loads with the GEP indices.
541 for (User::op_iterator II = User->op_begin() + 1, IE = User->op_end();
543 Indices.push_back(cast<ConstantInt>(*II)->getSExtValue());
544 // GEPs with a single 0 index can be merged with direct loads
545 if (Indices.size() == 1 && Indices.front() == 0)
547 ArgIndices.insert(Indices);
549 if (LoadInst *L = dyn_cast<LoadInst>(User))
552 // Take any load, we will use it only to update Alias Analysis
553 OrigLoad = cast<LoadInst>(User->use_back());
554 OriginalLoads[Indices] = OrigLoad;
557 // Add a parameter to the function for each element passed in.
558 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
559 E = ArgIndices.end(); SI != E; ++SI) {
560 // not allowed to dereference ->begin() if size() is 0
561 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(),
564 assert(Params.back());
567 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
568 ++NumArgumentsPromoted;
570 ++NumAggregatesPromoted;
574 // Add any function attributes.
575 if (Attributes attrs = PAL.getFnAttributes())
576 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
578 const Type *RetTy = FTy->getReturnType();
579 LLVMContext &Context = RetTy->getContext();
581 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
582 // have zero fixed arguments.
583 bool ExtraArgHack = false;
584 if (Params.empty() && FTy->isVarArg()) {
586 Params.push_back(Type::Int32Ty);
589 // Construct the new function type using the new arguments.
590 FunctionType *NFTy = Context.getFunctionType(RetTy, Params, FTy->isVarArg());
592 // Create the new function body and insert it into the module...
593 Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
594 NF->copyAttributesFrom(F);
596 // Recompute the parameter attributes list based on the new arguments for
598 NF->setAttributes(AttrListPtr::get(AttributesVec.begin(), AttributesVec.end()));
599 AttributesVec.clear();
601 F->getParent()->getFunctionList().insert(F, NF);
604 // Get the alias analysis information that we need to update to reflect our
606 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
608 // Get the callgraph information that we need to update to reflect our
610 CallGraph &CG = getAnalysis<CallGraph>();
612 // Loop over all of the callers of the function, transforming the call sites
613 // to pass in the loaded pointers.
615 SmallVector<Value*, 16> Args;
616 while (!F->use_empty()) {
617 CallSite CS = CallSite::get(F->use_back());
618 Instruction *Call = CS.getInstruction();
619 const AttrListPtr &CallPAL = CS.getAttributes();
621 // Add any return attributes.
622 if (Attributes attrs = CallPAL.getRetAttributes())
623 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
625 // Loop over the operands, inserting GEP and loads in the caller as
627 CallSite::arg_iterator AI = CS.arg_begin();
629 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
630 I != E; ++I, ++AI, ++ArgIndex)
631 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
632 Args.push_back(*AI); // Unmodified argument
634 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
635 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
637 } else if (ByValArgsToTransform.count(I)) {
638 // Emit a GEP and load for each element of the struct.
639 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
640 const StructType *STy = cast<StructType>(AgTy);
641 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
642 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
643 Idxs[1] = ConstantInt::get(Type::Int32Ty, 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 = (isa<StructType>(ElTy) ? Type::Int32Ty : Type::Int64Ty);
668 Ops.push_back(ConstantInt::get(IdxTy, *II));
669 // Keep track of the type we're currently indexing
670 ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(*II);
672 // And create a GEP to extract those indices
673 V = GetElementPtrInst::Create(V, Ops.begin(), Ops.end(),
674 V->getName()+".idx", Call);
676 AA.copyValue(OrigLoad->getOperand(0), V);
678 Args.push_back(new LoadInst(V, V->getName()+".val", Call));
679 AA.copyValue(OrigLoad, Args.back());
684 Args.push_back(Context.getNullValue(Type::Int32Ty));
686 // Push any varargs arguments on the list
687 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
689 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
690 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
693 // Add any function attributes.
694 if (Attributes attrs = CallPAL.getFnAttributes())
695 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
698 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
699 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
700 Args.begin(), Args.end(), "", Call);
701 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
702 cast<InvokeInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
703 AttributesVec.end()));
705 New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
706 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
707 cast<CallInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
708 AttributesVec.end()));
709 if (cast<CallInst>(Call)->isTailCall())
710 cast<CallInst>(New)->setTailCall();
713 AttributesVec.clear();
715 // Update the alias analysis implementation to know that we are replacing
716 // the old call with a new one.
717 AA.replaceWithNewValue(Call, New);
719 // Update the callgraph to know that the callsite has been transformed.
720 CG[Call->getParent()->getParent()]->replaceCallSite(Call, New);
722 if (!Call->use_empty()) {
723 Call->replaceAllUsesWith(New);
727 // Finally, remove the old call from the program, reducing the use-count of
729 Call->eraseFromParent();
732 // Since we have now created the new function, splice the body of the old
733 // function right into the new function, leaving the old rotting hulk of the
735 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
737 // Loop over the argument list, transfering uses of the old arguments over to
738 // the new arguments, also transfering over the names as well.
740 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
741 I2 = NF->arg_begin(); I != E; ++I) {
742 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
743 // If this is an unmodified argument, move the name and users over to the
745 I->replaceAllUsesWith(I2);
747 AA.replaceWithNewValue(I, I2);
752 if (ByValArgsToTransform.count(I)) {
753 // In the callee, we create an alloca, and store each of the new incoming
754 // arguments into the alloca.
755 Instruction *InsertPt = NF->begin()->begin();
757 // Just add all the struct element types.
758 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
759 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
760 const StructType *STy = cast<StructType>(AgTy);
761 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
763 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
764 Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
766 GetElementPtrInst::Create(TheAlloca, Idxs, Idxs+2,
767 TheAlloca->getName()+"."+utostr(i),
769 I2->setName(I->getName()+"."+utostr(i));
770 new StoreInst(I2++, Idx, InsertPt);
773 // Anything that used the arg should now use the alloca.
774 I->replaceAllUsesWith(TheAlloca);
775 TheAlloca->takeName(I);
776 AA.replaceWithNewValue(I, TheAlloca);
780 if (I->use_empty()) {
785 // Otherwise, if we promoted this argument, then all users are load
786 // instructions (or GEPs with only load users), and all loads should be
787 // using the new argument that we added.
788 ScalarizeTable &ArgIndices = ScalarizedElements[I];
790 while (!I->use_empty()) {
791 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
792 assert(ArgIndices.begin()->empty() &&
793 "Load element should sort to front!");
794 I2->setName(I->getName()+".val");
795 LI->replaceAllUsesWith(I2);
796 AA.replaceWithNewValue(LI, I2);
797 LI->eraseFromParent();
798 DOUT << "*** Promoted load of argument '" << I->getName()
799 << "' in function '" << F->getName() << "'\n";
801 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
802 IndicesVector Operands;
803 Operands.reserve(GEP->getNumIndices());
804 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
806 Operands.push_back(cast<ConstantInt>(*II)->getSExtValue());
808 // GEPs with a single 0 index can be merged with direct loads
809 if (Operands.size() == 1 && Operands.front() == 0)
812 Function::arg_iterator TheArg = I2;
813 for (ScalarizeTable::iterator It = ArgIndices.begin();
814 *It != Operands; ++It, ++TheArg) {
815 assert(It != ArgIndices.end() && "GEP not handled??");
818 std::string NewName = I->getName();
819 for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
820 NewName += "." + utostr(Operands[i]);
823 TheArg->setName(NewName);
825 DOUT << "*** Promoted agg argument '" << TheArg->getName()
826 << "' of function '" << NF->getName() << "'\n";
828 // All of the uses must be load instructions. Replace them all with
829 // the argument specified by ArgNo.
830 while (!GEP->use_empty()) {
831 LoadInst *L = cast<LoadInst>(GEP->use_back());
832 L->replaceAllUsesWith(TheArg);
833 AA.replaceWithNewValue(L, TheArg);
834 L->eraseFromParent();
837 GEP->eraseFromParent();
841 // Increment I2 past all of the arguments added for this promoted pointer.
842 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
846 // Notify the alias analysis implementation that we inserted a new argument.
848 AA.copyValue(Context.getNullValue(Type::Int32Ty), NF->arg_begin());
851 // Tell the alias analysis that the old function is about to disappear.
852 AA.replaceWithNewValue(F, NF);
854 // Now that the old function is dead, delete it.
855 F->eraseFromParent();