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 for (Value::use_iterator UI = F->use_begin(), E = F->use_end();
132 CallSite CS = CallSite::get(*UI);
133 if (!CS.getInstruction()) // "Taking the address" of the function
136 // Ensure that this call site is CALLING the function, not passing it as
138 if (!CS.isCallee(UI))
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 DOUT << "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()) return false;
187 Function *NewF = DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
189 // Update the call graph to know that the function has been transformed.
190 getAnalysis<CallGraph>().changeFunction(F, NewF);
194 /// IsAlwaysValidPointer - Return true if the specified pointer is always legal
196 static bool IsAlwaysValidPointer(Value *V) {
197 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
198 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V))
199 return IsAlwaysValidPointer(GEP->getOperand(0));
200 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
201 if (CE->getOpcode() == Instruction::GetElementPtr)
202 return IsAlwaysValidPointer(CE->getOperand(0));
207 /// AllCalleesPassInValidPointerForArgument - Return true if we can prove that
208 /// all callees pass in a valid pointer for the specified function argument.
209 static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
210 Function *Callee = Arg->getParent();
212 unsigned ArgNo = std::distance(Callee->arg_begin(),
213 Function::arg_iterator(Arg));
215 // Look at all call sites of the function. At this pointer we know we only
216 // have direct callees.
217 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
219 CallSite CS = CallSite::get(*UI);
220 assert(CS.getInstruction() && "Should only have direct calls!");
222 if (!IsAlwaysValidPointer(CS.getArgument(ArgNo)))
228 /// Returns true if Prefix is a prefix of longer. That means, Longer has a size
229 /// that is greater than or equal to the size of prefix, and each of the
230 /// elements in Prefix is the same as the corresponding elements in Longer.
232 /// This means it also returns true when Prefix and Longer are equal!
233 static bool IsPrefix(const ArgPromotion::IndicesVector &Prefix,
234 const ArgPromotion::IndicesVector &Longer) {
235 if (Prefix.size() > Longer.size())
237 for (unsigned i = 0, e = Prefix.size(); i != e; ++i)
238 if (Prefix[i] != Longer[i])
244 /// Checks if Indices, or a prefix of Indices, is in Set.
245 static bool PrefixIn(const ArgPromotion::IndicesVector &Indices,
246 std::set<ArgPromotion::IndicesVector> &Set) {
247 std::set<ArgPromotion::IndicesVector>::iterator Low;
248 Low = Set.upper_bound(Indices);
249 if (Low != Set.begin())
251 // Low is now the last element smaller than or equal to Indices. This means
252 // it points to a prefix of Indices (possibly Indices itself), if such
255 // This load is safe if any prefix of its operands is safe to load.
256 return Low != Set.end() && IsPrefix(*Low, Indices);
259 /// Mark the given indices (ToMark) as safe in the the given set of indices
260 /// (Safe). Marking safe usually means adding ToMark to Safe. However, if there
261 /// is already a prefix of Indices in Safe, Indices are implicitely marked safe
262 /// already. Furthermore, any indices that Indices is itself a prefix of, are
263 /// removed from Safe (since they are implicitely safe because of Indices now).
264 static void MarkIndicesSafe(const ArgPromotion::IndicesVector &ToMark,
265 std::set<ArgPromotion::IndicesVector> &Safe) {
266 std::set<ArgPromotion::IndicesVector>::iterator Low;
267 Low = Safe.upper_bound(ToMark);
268 // Guard against the case where Safe is empty
269 if (Low != Safe.begin())
271 // Low is now the last element smaller than or equal to Indices. This
272 // means it points to a prefix of Indices (possibly Indices itself), if
273 // such prefix exists.
274 if (Low != Safe.end()) {
275 if (IsPrefix(*Low, ToMark))
276 // If there is already a prefix of these indices (or exactly these
277 // indices) marked a safe, don't bother adding these indices
280 // Increment Low, so we can use it as a "insert before" hint
284 Low = Safe.insert(Low, ToMark);
286 // If there we're a prefix of longer index list(s), remove those
287 std::set<ArgPromotion::IndicesVector>::iterator End = Safe.end();
288 while (Low != End && IsPrefix(ToMark, *Low)) {
289 std::set<ArgPromotion::IndicesVector>::iterator Remove = Low;
295 /// isSafeToPromoteArgument - As you might guess from the name of this method,
296 /// it checks to see if it is both safe and useful to promote the argument.
297 /// This method limits promotion of aggregates to only promote up to three
298 /// elements of the aggregate in order to avoid exploding the number of
299 /// arguments passed in.
300 bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
301 typedef std::set<IndicesVector> GEPIndicesSet;
303 // Quick exit for unused arguments
304 if (Arg->use_empty())
307 // We can only promote this argument if all of the uses are loads, or are GEP
308 // instructions (with constant indices) that are subsequently loaded.
310 // Promoting the argument causes it to be loaded in the caller
311 // unconditionally. This is only safe if we can prove that either the load
312 // would have happened in the callee anyway (ie, there is a load in the entry
313 // block) or the pointer passed in at every call site is guaranteed to be
315 // In the former case, invalid loads can happen, but would have happened
316 // anyway, in the latter case, invalid loads won't happen. This prevents us
317 // from introducing an invalid load that wouldn't have happened in the
320 // This set will contain all sets of indices that are loaded in the entry
321 // block, and thus are safe to unconditionally load in the caller.
322 GEPIndicesSet SafeToUnconditionallyLoad;
324 // This set contains all the sets of indices that we are planning to promote.
325 // This makes it possible to limit the number of arguments added.
326 GEPIndicesSet ToPromote;
328 // If the pointer is always valid, any load with first index 0 is valid.
329 if(isByVal || AllCalleesPassInValidPointerForArgument(Arg))
330 SafeToUnconditionallyLoad.insert(IndicesVector(1, 0));
332 // First, iterate the entry block and mark loads of (geps of) arguments as
334 BasicBlock *EntryBlock = Arg->getParent()->begin();
335 // Declare this here so we can reuse it
336 IndicesVector Indices;
337 for (BasicBlock::iterator I = EntryBlock->begin(), E = EntryBlock->end();
339 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
340 Value *V = LI->getPointerOperand();
341 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
342 V = GEP->getPointerOperand();
344 // This load actually loads (part of) Arg? Check the indices then.
345 Indices.reserve(GEP->getNumIndices());
346 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
348 if (ConstantInt *CI = dyn_cast<ConstantInt>(*II))
349 Indices.push_back(CI->getSExtValue());
351 // We found a non-constant GEP index for this argument? Bail out
352 // right away, can't promote this argument at all.
355 // Indices checked out, mark them as safe
356 MarkIndicesSafe(Indices, SafeToUnconditionallyLoad);
359 } else if (V == Arg) {
360 // Direct loads are equivalent to a GEP with a single 0 index.
361 MarkIndicesSafe(IndicesVector(1, 0), SafeToUnconditionallyLoad);
365 // Now, iterate all uses of the argument to see if there are any uses that are
366 // not (GEP+)loads, or any (GEP+)loads that are not safe to promote.
367 SmallVector<LoadInst*, 16> Loads;
368 IndicesVector Operands;
369 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
372 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
373 if (LI->isVolatile()) return false; // Don't hack volatile loads
375 // Direct loads are equivalent to a GEP with a zero index and then a load.
376 Operands.push_back(0);
377 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
378 if (GEP->use_empty()) {
379 // Dead GEP's cause trouble later. Just remove them if we run into
381 getAnalysis<AliasAnalysis>().deleteValue(GEP);
382 GEP->eraseFromParent();
383 // TODO: This runs the above loop over and over again for dead GEPS
384 // Couldn't we just do increment the UI iterator earlier and erase the
386 return isSafeToPromoteArgument(Arg, isByVal);
389 // Ensure that all of the indices are constants.
390 for (User::op_iterator i = GEP->idx_begin(), e = GEP->idx_end();
392 if (ConstantInt *C = dyn_cast<ConstantInt>(*i))
393 Operands.push_back(C->getSExtValue());
395 return false; // Not a constant operand GEP!
397 // Ensure that the only users of the GEP are load instructions.
398 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
400 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
401 if (LI->isVolatile()) return false; // Don't hack volatile loads
404 // Other uses than load?
408 return false; // Not a load or a GEP.
411 // Now, see if it is safe to promote this load / loads of this GEP. Loading
412 // is safe if Operands, or a prefix of Operands, is marked as safe.
413 if (!PrefixIn(Operands, SafeToUnconditionallyLoad))
416 // See if we are already promoting a load with these indices. If not, check
417 // to make sure that we aren't promoting too many elements. If so, nothing
419 if (ToPromote.find(Operands) == ToPromote.end()) {
420 if (maxElements > 0 && ToPromote.size() == maxElements) {
421 DOUT << "argpromotion not promoting argument '"
422 << Arg->getName() << "' because it would require adding more "
423 << "than " << maxElements << " arguments to the function.\n";
424 // We limit aggregate promotion to only promoting up to a fixed number
425 // of elements of the aggregate.
428 ToPromote.insert(Operands);
432 if (Loads.empty()) return true; // No users, this is a dead argument.
434 // Okay, now we know that the argument is only used by load instructions and
435 // it is safe to unconditionally perform all of them. Use alias analysis to
436 // check to see if the pointer is guaranteed to not be modified from entry of
437 // the function to each of the load instructions.
439 // Because there could be several/many load instructions, remember which
440 // blocks we know to be transparent to the load.
441 SmallPtrSet<BasicBlock*, 16> TranspBlocks;
443 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
444 TargetData &TD = getAnalysis<TargetData>();
446 for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
447 // Check to see if the load is invalidated from the start of the block to
449 LoadInst *Load = Loads[i];
450 BasicBlock *BB = Load->getParent();
452 const PointerType *LoadTy =
453 cast<PointerType>(Load->getPointerOperand()->getType());
454 unsigned LoadSize = (unsigned)TD.getTypeStoreSize(LoadTy->getElementType());
456 if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize))
457 return false; // Pointer is invalidated!
459 // Now check every path from the entry block to the load for transparency.
460 // To do this, we perform a depth first search on the inverse CFG from the
462 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
463 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
464 I = idf_ext_begin(*PI, TranspBlocks),
465 E = idf_ext_end(*PI, TranspBlocks); I != E; ++I)
466 if (AA.canBasicBlockModify(**I, Arg, LoadSize))
470 // If the path from the entry of the function to each load is free of
471 // instructions that potentially invalidate the load, we can make the
476 /// DoPromotion - This method actually performs the promotion of the specified
477 /// arguments, and returns the new function. At this point, we know that it's
479 Function *ArgPromotion::DoPromotion(Function *F,
480 SmallPtrSet<Argument*, 8> &ArgsToPromote,
481 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
483 // Start by computing a new prototype for the function, which is the same as
484 // the old function, but has modified arguments.
485 const FunctionType *FTy = F->getFunctionType();
486 std::vector<const Type*> Params;
488 typedef std::set<IndicesVector> ScalarizeTable;
490 // ScalarizedElements - If we are promoting a pointer that has elements
491 // accessed out of it, keep track of which elements are accessed so that we
492 // can add one argument for each.
494 // Arguments that are directly loaded will have a zero element value here, to
495 // handle cases where there are both a direct load and GEP accesses.
497 std::map<Argument*, ScalarizeTable> ScalarizedElements;
499 // OriginalLoads - Keep track of a representative load instruction from the
500 // original function so that we can tell the alias analysis implementation
501 // what the new GEP/Load instructions we are inserting look like.
502 std::map<IndicesVector, LoadInst*> OriginalLoads;
504 // Attributes - Keep track of the parameter attributes for the arguments
505 // that we are *not* promoting. For the ones that we do promote, the parameter
506 // attributes are lost
507 SmallVector<AttributeWithIndex, 8> AttributesVec;
508 const AttrListPtr &PAL = F->getAttributes();
510 // Add any return attributes.
511 if (Attributes attrs = PAL.getRetAttributes())
512 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
514 // First, determine the new argument list
515 unsigned ArgIndex = 1;
516 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
518 if (ByValArgsToTransform.count(I)) {
519 // Simple byval argument? Just add all the struct element types.
520 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
521 const StructType *STy = cast<StructType>(AgTy);
522 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
523 Params.push_back(STy->getElementType(i));
524 ++NumByValArgsPromoted;
525 } else if (!ArgsToPromote.count(I)) {
526 // Unchanged argument
527 Params.push_back(I->getType());
528 if (Attributes attrs = PAL.getParamAttributes(ArgIndex))
529 AttributesVec.push_back(AttributeWithIndex::get(Params.size(), attrs));
530 } else if (I->use_empty()) {
531 // Dead argument (which are always marked as promotable)
534 // Okay, this is being promoted. This means that the only uses are loads
535 // or GEPs which are only used by loads
537 // In this table, we will track which indices are loaded from the argument
538 // (where direct loads are tracked as no indices).
539 ScalarizeTable &ArgIndices = ScalarizedElements[I];
540 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
542 Instruction *User = cast<Instruction>(*UI);
543 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
544 IndicesVector Indices;
545 Indices.reserve(User->getNumOperands() - 1);
546 // Since loads will only have a single operand, and GEPs only a single
547 // non-index operand, this will record direct loads without any indices,
548 // and gep+loads with the GEP indices.
549 for (User::op_iterator II = User->op_begin() + 1, IE = User->op_end();
551 Indices.push_back(cast<ConstantInt>(*II)->getSExtValue());
552 // GEPs with a single 0 index can be merged with direct loads
553 if (Indices.size() == 1 && Indices.front() == 0)
555 ArgIndices.insert(Indices);
557 if (LoadInst *L = dyn_cast<LoadInst>(User))
560 // Take any load, we will use it only to update Alias Analysis
561 OrigLoad = cast<LoadInst>(User->use_back());
562 OriginalLoads[Indices] = OrigLoad;
565 // Add a parameter to the function for each element passed in.
566 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
567 E = ArgIndices.end(); SI != E; ++SI) {
568 unsigned num = SI->size();
569 // not allowed to dereference ->begin() if size() is 0
570 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(),
571 num ? &*SI->begin(): 0,
573 assert(Params.back());
576 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
577 ++NumArgumentsPromoted;
579 ++NumAggregatesPromoted;
583 // Add any function attributes.
584 if (Attributes attrs = PAL.getFnAttributes())
585 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
587 const Type *RetTy = FTy->getReturnType();
589 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
590 // have zero fixed arguments.
591 bool ExtraArgHack = false;
592 if (Params.empty() && FTy->isVarArg()) {
594 Params.push_back(Type::Int32Ty);
597 // Construct the new function type using the new arguments.
598 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
600 // Create the new function body and insert it into the module...
601 Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
602 NF->copyAttributesFrom(F);
604 // Recompute the parameter attributes list based on the new arguments for
606 NF->setAttributes(AttrListPtr::get(AttributesVec.begin(), AttributesVec.end()));
607 AttributesVec.clear();
609 F->getParent()->getFunctionList().insert(F, NF);
612 // Get the alias analysis information that we need to update to reflect our
614 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
616 // Get the callgraph information that we need to update to reflect our
618 CallGraph &CG = getAnalysis<CallGraph>();
620 // Loop over all of the callers of the function, transforming the call sites
621 // to pass in the loaded pointers.
623 SmallVector<Value*, 16> Args;
624 while (!F->use_empty()) {
625 CallSite CS = CallSite::get(F->use_back());
626 Instruction *Call = CS.getInstruction();
627 const AttrListPtr &CallPAL = CS.getAttributes();
629 // Add any return attributes.
630 if (Attributes attrs = CallPAL.getRetAttributes())
631 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
633 // Loop over the operands, inserting GEP and loads in the caller as
635 CallSite::arg_iterator AI = CS.arg_begin();
637 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
638 I != E; ++I, ++AI, ++ArgIndex)
639 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
640 Args.push_back(*AI); // Unmodified argument
642 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
643 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
645 } else if (ByValArgsToTransform.count(I)) {
646 // Emit a GEP and load for each element of the struct.
647 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
648 const StructType *STy = cast<StructType>(AgTy);
649 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
650 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
651 Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
652 Value *Idx = GetElementPtrInst::Create(*AI, Idxs, Idxs+2,
653 (*AI)->getName()+"."+utostr(i),
655 // TODO: Tell AA about the new values?
656 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
658 } else if (!I->use_empty()) {
659 // Non-dead argument: insert GEPs and loads as appropriate.
660 ScalarizeTable &ArgIndices = ScalarizedElements[I];
661 // Store the Value* version of the indices in here, but declare it now
663 std::vector<Value*> Ops;
664 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
665 E = ArgIndices.end(); SI != E; ++SI) {
667 LoadInst *OrigLoad = OriginalLoads[*SI];
669 Ops.reserve(SI->size());
670 const Type *ElTy = V->getType();
671 for (IndicesVector::const_iterator II = SI->begin(),
672 IE = SI->end(); II != IE; ++II) {
673 // Use i32 to index structs, and i64 for others (pointers/arrays).
674 // This satisfies GEP constraints.
675 const Type *IdxTy = (isa<StructType>(ElTy) ? Type::Int32Ty : Type::Int64Ty);
676 Ops.push_back(ConstantInt::get(IdxTy, *II));
677 // Keep track of the type we're currently indexing
678 ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(*II);
680 // And create a GEP to extract those indices
681 V = GetElementPtrInst::Create(V, Ops.begin(), Ops.end(),
682 V->getName()+".idx", Call);
684 AA.copyValue(OrigLoad->getOperand(0), V);
686 Args.push_back(new LoadInst(V, V->getName()+".val", Call));
687 AA.copyValue(OrigLoad, Args.back());
692 Args.push_back(Constant::getNullValue(Type::Int32Ty));
694 // Push any varargs arguments on the list
695 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
697 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
698 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
701 // Add any function attributes.
702 if (Attributes attrs = CallPAL.getFnAttributes())
703 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
706 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
707 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
708 Args.begin(), Args.end(), "", Call);
709 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
710 cast<InvokeInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
711 AttributesVec.end()));
713 New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
714 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
715 cast<CallInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
716 AttributesVec.end()));
717 if (cast<CallInst>(Call)->isTailCall())
718 cast<CallInst>(New)->setTailCall();
721 AttributesVec.clear();
723 // Update the alias analysis implementation to know that we are replacing
724 // the old call with a new one.
725 AA.replaceWithNewValue(Call, New);
727 // Update the callgraph to know that the callsite has been transformed.
728 CG[Call->getParent()->getParent()]->replaceCallSite(Call, New);
730 if (!Call->use_empty()) {
731 Call->replaceAllUsesWith(New);
735 // Finally, remove the old call from the program, reducing the use-count of
737 Call->eraseFromParent();
740 // Since we have now created the new function, splice the body of the old
741 // function right into the new function, leaving the old rotting hulk of the
743 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
745 // Loop over the argument list, transfering uses of the old arguments over to
746 // the new arguments, also transfering over the names as well.
748 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
749 I2 = NF->arg_begin(); I != E; ++I) {
750 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
751 // If this is an unmodified argument, move the name and users over to the
753 I->replaceAllUsesWith(I2);
755 AA.replaceWithNewValue(I, I2);
760 if (ByValArgsToTransform.count(I)) {
761 // In the callee, we create an alloca, and store each of the new incoming
762 // arguments into the alloca.
763 Instruction *InsertPt = NF->begin()->begin();
765 // Just add all the struct element types.
766 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
767 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
768 const StructType *STy = cast<StructType>(AgTy);
769 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
771 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
772 Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
773 std::string Name = TheAlloca->getName()+"."+utostr(i);
774 Value *Idx = GetElementPtrInst::Create(TheAlloca, Idxs, Idxs+2,
776 I2->setName(I->getName()+"."+utostr(i));
777 new StoreInst(I2++, Idx, InsertPt);
780 // Anything that used the arg should now use the alloca.
781 I->replaceAllUsesWith(TheAlloca);
782 TheAlloca->takeName(I);
783 AA.replaceWithNewValue(I, TheAlloca);
787 if (I->use_empty()) {
792 // Otherwise, if we promoted this argument, then all users are load
793 // instructions (or GEPs with only load users), and all loads should be
794 // using the new argument that we added.
795 ScalarizeTable &ArgIndices = ScalarizedElements[I];
797 while (!I->use_empty()) {
798 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
799 assert(ArgIndices.begin()->empty() &&
800 "Load element should sort to front!");
801 I2->setName(I->getName()+".val");
802 LI->replaceAllUsesWith(I2);
803 AA.replaceWithNewValue(LI, I2);
804 LI->eraseFromParent();
805 DOUT << "*** Promoted load of argument '" << I->getName()
806 << "' in function '" << F->getName() << "'\n";
808 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
809 IndicesVector Operands;
810 Operands.reserve(GEP->getNumIndices());
811 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
813 Operands.push_back(cast<ConstantInt>(*II)->getSExtValue());
815 // GEPs with a single 0 index can be merged with direct loads
816 if (Operands.size() == 1 && Operands.front() == 0)
819 Function::arg_iterator TheArg = I2;
820 for (ScalarizeTable::iterator It = ArgIndices.begin();
821 *It != Operands; ++It, ++TheArg) {
822 assert(It != ArgIndices.end() && "GEP not handled??");
825 std::string NewName = I->getName();
826 for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
827 NewName += "." + utostr(Operands[i]);
830 TheArg->setName(NewName);
832 DOUT << "*** Promoted agg argument '" << TheArg->getName()
833 << "' of function '" << NF->getName() << "'\n";
835 // All of the uses must be load instructions. Replace them all with
836 // the argument specified by ArgNo.
837 while (!GEP->use_empty()) {
838 LoadInst *L = cast<LoadInst>(GEP->use_back());
839 L->replaceAllUsesWith(TheArg);
840 AA.replaceWithNewValue(L, TheArg);
841 L->eraseFromParent();
844 GEP->eraseFromParent();
848 // Increment I2 past all of the arguments added for this promoted pointer.
849 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
853 // Notify the alias analysis implementation that we inserted a new argument.
855 AA.copyValue(Constant::getNullValue(Type::Int32Ty), NF->arg_begin());
858 // Tell the alias analysis that the old function is about to disappear.
859 AA.replaceWithNewValue(F, NF);
861 // Now that the old function is dead, delete it.
862 F->eraseFromParent();