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/Support/raw_ostream.h"
47 #include "llvm/ADT/DepthFirstIterator.h"
48 #include "llvm/ADT/Statistic.h"
49 #include "llvm/ADT/StringExtras.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 ArgPromotion : public CallGraphSCCPass {
62 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
63 AU.addRequired<AliasAnalysis>();
64 CallGraphSCCPass::getAnalysisUsage(AU);
67 virtual bool runOnSCC(CallGraphSCC &SCC);
68 static char ID; // Pass identification, replacement for typeid
69 explicit ArgPromotion(unsigned maxElements = 3)
70 : CallGraphSCCPass(ID), maxElements(maxElements) {
71 initializeArgPromotionPass(*PassRegistry::getPassRegistry());
74 /// A vector used to hold the indices of a single GEP instruction
75 typedef std::vector<uint64_t> IndicesVector;
78 CallGraphNode *PromoteArguments(CallGraphNode *CGN);
79 bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const;
80 CallGraphNode *DoPromotion(Function *F,
81 SmallPtrSet<Argument*, 8> &ArgsToPromote,
82 SmallPtrSet<Argument*, 8> &ByValArgsToTransform);
83 /// The maximum number of elements to expand, or 0 for unlimited.
88 char ArgPromotion::ID = 0;
89 INITIALIZE_PASS_BEGIN(ArgPromotion, "argpromotion",
90 "Promote 'by reference' arguments to scalars", false, false)
91 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
92 INITIALIZE_AG_DEPENDENCY(CallGraph)
93 INITIALIZE_PASS_END(ArgPromotion, "argpromotion",
94 "Promote 'by reference' arguments to scalars", false, false)
96 Pass *llvm::createArgumentPromotionPass(unsigned maxElements) {
97 return new ArgPromotion(maxElements);
100 bool ArgPromotion::runOnSCC(CallGraphSCC &SCC) {
101 bool Changed = false, LocalChange;
103 do { // Iterate until we stop promoting from this SCC.
105 // Attempt to promote arguments from all functions in this SCC.
106 for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I) {
107 if (CallGraphNode *CGN = PromoteArguments(*I)) {
109 SCC.ReplaceNode(*I, CGN);
112 Changed |= LocalChange; // Remember that we changed something.
113 } while (LocalChange);
118 /// PromoteArguments - This method checks the specified function to see if there
119 /// are any promotable arguments and if it is safe to promote the function (for
120 /// example, all callers are direct). If safe to promote some arguments, it
121 /// calls the DoPromotion method.
123 CallGraphNode *ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
124 Function *F = CGN->getFunction();
126 // Make sure that it is local to this module.
127 if (!F || !F->hasLocalLinkage()) return 0;
129 // First check: see if there are any pointer arguments! If not, quick exit.
130 SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs;
132 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
133 I != E; ++I, ++ArgNo)
134 if (I->getType()->isPointerTy())
135 PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo));
136 if (PointerArgs.empty()) return 0;
138 // Second check: make sure that all callers are direct callers. We can't
139 // transform functions that have indirect callers.
140 if (F->hasAddressTaken())
143 // Check to see which arguments are promotable. If an argument is promotable,
144 // add it to ArgsToPromote.
145 SmallPtrSet<Argument*, 8> ArgsToPromote;
146 SmallPtrSet<Argument*, 8> ByValArgsToTransform;
147 for (unsigned i = 0; i != PointerArgs.size(); ++i) {
148 bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, Attribute::ByVal);
150 // If this is a byval argument, and if the aggregate type is small, just
151 // pass the elements, which is always safe.
152 Argument *PtrArg = PointerArgs[i].first;
154 const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
155 if (const StructType *STy = dyn_cast<StructType>(AgTy)) {
156 if (maxElements > 0 && STy->getNumElements() > maxElements) {
157 DEBUG(dbgs() << "argpromotion disable promoting argument '"
158 << PtrArg->getName() << "' because it would require adding more"
159 << " than " << maxElements << " arguments to the function.\n");
161 // If all the elements are single-value types, we can promote it.
162 bool AllSimple = true;
163 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
164 if (!STy->getElementType(i)->isSingleValueType()) {
169 // Safe to transform, don't even bother trying to "promote" it.
170 // Passing the elements as a scalar will allow scalarrepl to hack on
171 // the new alloca we introduce.
173 ByValArgsToTransform.insert(PtrArg);
180 // Otherwise, see if we can promote the pointer to its value.
181 if (isSafeToPromoteArgument(PtrArg, isByVal))
182 ArgsToPromote.insert(PtrArg);
185 // No promotable pointer arguments.
186 if (ArgsToPromote.empty() && ByValArgsToTransform.empty())
189 return DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
192 /// IsAlwaysValidPointer - Return true if the specified pointer is always legal
194 static bool IsAlwaysValidPointer(Value *V) {
195 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
196 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V))
197 return IsAlwaysValidPointer(GEP->getOperand(0));
198 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
199 if (CE->getOpcode() == Instruction::GetElementPtr)
200 return IsAlwaysValidPointer(CE->getOperand(0));
205 /// AllCalleesPassInValidPointerForArgument - Return true if we can prove that
206 /// all callees pass in a valid pointer for the specified function argument.
207 static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
208 Function *Callee = Arg->getParent();
210 unsigned ArgNo = std::distance(Callee->arg_begin(),
211 Function::arg_iterator(Arg));
213 // Look at all call sites of the function. At this pointer we know we only
214 // have direct callees.
215 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
218 assert(CS && "Should only have direct calls!");
220 if (!IsAlwaysValidPointer(CS.getArgument(ArgNo)))
226 /// Returns true if Prefix is a prefix of longer. That means, Longer has a size
227 /// that is greater than or equal to the size of prefix, and each of the
228 /// elements in Prefix is the same as the corresponding elements in Longer.
230 /// This means it also returns true when Prefix and Longer are equal!
231 static bool IsPrefix(const ArgPromotion::IndicesVector &Prefix,
232 const ArgPromotion::IndicesVector &Longer) {
233 if (Prefix.size() > Longer.size())
235 for (unsigned i = 0, e = Prefix.size(); i != e; ++i)
236 if (Prefix[i] != Longer[i])
242 /// Checks if Indices, or a prefix of Indices, is in Set.
243 static bool PrefixIn(const ArgPromotion::IndicesVector &Indices,
244 std::set<ArgPromotion::IndicesVector> &Set) {
245 std::set<ArgPromotion::IndicesVector>::iterator Low;
246 Low = Set.upper_bound(Indices);
247 if (Low != Set.begin())
249 // Low is now the last element smaller than or equal to Indices. This means
250 // it points to a prefix of Indices (possibly Indices itself), if such
253 // This load is safe if any prefix of its operands is safe to load.
254 return Low != Set.end() && IsPrefix(*Low, Indices);
257 /// Mark the given indices (ToMark) as safe in the given set of indices
258 /// (Safe). Marking safe usually means adding ToMark to Safe. However, if there
259 /// is already a prefix of Indices in Safe, Indices are implicitely marked safe
260 /// already. Furthermore, any indices that Indices is itself a prefix of, are
261 /// removed from Safe (since they are implicitely safe because of Indices now).
262 static void MarkIndicesSafe(const ArgPromotion::IndicesVector &ToMark,
263 std::set<ArgPromotion::IndicesVector> &Safe) {
264 std::set<ArgPromotion::IndicesVector>::iterator Low;
265 Low = Safe.upper_bound(ToMark);
266 // Guard against the case where Safe is empty
267 if (Low != Safe.begin())
269 // Low is now the last element smaller than or equal to Indices. This
270 // means it points to a prefix of Indices (possibly Indices itself), if
271 // such prefix exists.
272 if (Low != Safe.end()) {
273 if (IsPrefix(*Low, ToMark))
274 // If there is already a prefix of these indices (or exactly these
275 // indices) marked a safe, don't bother adding these indices
278 // Increment Low, so we can use it as a "insert before" hint
282 Low = Safe.insert(Low, ToMark);
284 // If there we're a prefix of longer index list(s), remove those
285 std::set<ArgPromotion::IndicesVector>::iterator End = Safe.end();
286 while (Low != End && IsPrefix(ToMark, *Low)) {
287 std::set<ArgPromotion::IndicesVector>::iterator Remove = Low;
293 /// isSafeToPromoteArgument - As you might guess from the name of this method,
294 /// it checks to see if it is both safe and useful to promote the argument.
295 /// This method limits promotion of aggregates to only promote up to three
296 /// elements of the aggregate in order to avoid exploding the number of
297 /// arguments passed in.
298 bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
299 typedef std::set<IndicesVector> GEPIndicesSet;
301 // Quick exit for unused arguments
302 if (Arg->use_empty())
305 // We can only promote this argument if all of the uses are loads, or are GEP
306 // instructions (with constant indices) that are subsequently loaded.
308 // Promoting the argument causes it to be loaded in the caller
309 // unconditionally. This is only safe if we can prove that either the load
310 // would have happened in the callee anyway (ie, there is a load in the entry
311 // block) or the pointer passed in at every call site is guaranteed to be
313 // In the former case, invalid loads can happen, but would have happened
314 // anyway, in the latter case, invalid loads won't happen. This prevents us
315 // from introducing an invalid load that wouldn't have happened in the
318 // This set will contain all sets of indices that are loaded in the entry
319 // block, and thus are safe to unconditionally load in the caller.
320 GEPIndicesSet SafeToUnconditionallyLoad;
322 // This set contains all the sets of indices that we are planning to promote.
323 // This makes it possible to limit the number of arguments added.
324 GEPIndicesSet ToPromote;
326 // If the pointer is always valid, any load with first index 0 is valid.
327 if (isByVal || AllCalleesPassInValidPointerForArgument(Arg))
328 SafeToUnconditionallyLoad.insert(IndicesVector(1, 0));
330 // First, iterate the entry block and mark loads of (geps of) arguments as
332 BasicBlock *EntryBlock = Arg->getParent()->begin();
333 // Declare this here so we can reuse it
334 IndicesVector Indices;
335 for (BasicBlock::iterator I = EntryBlock->begin(), E = EntryBlock->end();
337 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
338 Value *V = LI->getPointerOperand();
339 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V)) {
340 V = GEP->getPointerOperand();
342 // This load actually loads (part of) Arg? Check the indices then.
343 Indices.reserve(GEP->getNumIndices());
344 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
346 if (ConstantInt *CI = dyn_cast<ConstantInt>(*II))
347 Indices.push_back(CI->getSExtValue());
349 // We found a non-constant GEP index for this argument? Bail out
350 // right away, can't promote this argument at all.
353 // Indices checked out, mark them as safe
354 MarkIndicesSafe(Indices, SafeToUnconditionallyLoad);
357 } else if (V == Arg) {
358 // Direct loads are equivalent to a GEP with a single 0 index.
359 MarkIndicesSafe(IndicesVector(1, 0), SafeToUnconditionallyLoad);
363 // Now, iterate all uses of the argument to see if there are any uses that are
364 // not (GEP+)loads, or any (GEP+)loads that are not safe to promote.
365 SmallVector<LoadInst*, 16> Loads;
366 IndicesVector Operands;
367 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
371 if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
372 if (LI->isVolatile()) return false; // Don't hack volatile loads
374 // Direct loads are equivalent to a GEP with a zero index and then a load.
375 Operands.push_back(0);
376 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
377 if (GEP->use_empty()) {
378 // Dead GEP's cause trouble later. Just remove them if we run into
380 getAnalysis<AliasAnalysis>().deleteValue(GEP);
381 GEP->eraseFromParent();
382 // TODO: This runs the above loop over and over again for dead GEPs
383 // Couldn't we just do increment the UI iterator earlier and erase the
385 return isSafeToPromoteArgument(Arg, isByVal);
388 // Ensure that all of the indices are constants.
389 for (User::op_iterator i = GEP->idx_begin(), e = GEP->idx_end();
391 if (ConstantInt *C = dyn_cast<ConstantInt>(*i))
392 Operands.push_back(C->getSExtValue());
394 return false; // Not a constant operand GEP!
396 // Ensure that the only users of the GEP are load instructions.
397 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
399 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
400 if (LI->isVolatile()) return false; // Don't hack volatile loads
403 // Other uses than load?
407 return false; // Not a load or a GEP.
410 // Now, see if it is safe to promote this load / loads of this GEP. Loading
411 // is safe if Operands, or a prefix of Operands, is marked as safe.
412 if (!PrefixIn(Operands, SafeToUnconditionallyLoad))
415 // See if we are already promoting a load with these indices. If not, check
416 // to make sure that we aren't promoting too many elements. If so, nothing
418 if (ToPromote.find(Operands) == ToPromote.end()) {
419 if (maxElements > 0 && ToPromote.size() == maxElements) {
420 DEBUG(dbgs() << "argpromotion not promoting argument '"
421 << Arg->getName() << "' because it would require adding more "
422 << "than " << maxElements << " arguments to the function.\n");
423 // We limit aggregate promotion to only promoting up to a fixed number
424 // of elements of the aggregate.
427 ToPromote.insert(Operands);
431 if (Loads.empty()) return true; // No users, this is a dead argument.
433 // Okay, now we know that the argument is only used by load instructions and
434 // it is safe to unconditionally perform all of them. Use alias analysis to
435 // check to see if the pointer is guaranteed to not be modified from entry of
436 // the function to each of the load instructions.
438 // Because there could be several/many load instructions, remember which
439 // blocks we know to be transparent to the load.
440 SmallPtrSet<BasicBlock*, 16> TranspBlocks;
442 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
443 TargetData *TD = getAnalysisIfAvailable<TargetData>();
444 if (!TD) return false; // Without TargetData, assume the worst.
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) {
464 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
465 I = idf_ext_begin(P, TranspBlocks),
466 E = idf_ext_end(P, TranspBlocks); I != E; ++I)
467 if (AA.canBasicBlockModify(**I, Arg, LoadSize))
472 // If the path from the entry of the function to each load is free of
473 // instructions that potentially invalidate the load, we can make the
478 /// DoPromotion - This method actually performs the promotion of the specified
479 /// arguments, and returns the new function. At this point, we know that it's
481 CallGraphNode *ArgPromotion::DoPromotion(Function *F,
482 SmallPtrSet<Argument*, 8> &ArgsToPromote,
483 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
485 // Start by computing a new prototype for the function, which is the same as
486 // the old function, but has modified arguments.
487 const FunctionType *FTy = F->getFunctionType();
488 std::vector<const Type*> Params;
490 typedef std::set<IndicesVector> ScalarizeTable;
492 // ScalarizedElements - If we are promoting a pointer that has elements
493 // accessed out of it, keep track of which elements are accessed so that we
494 // can add one argument for each.
496 // Arguments that are directly loaded will have a zero element value here, to
497 // handle cases where there are both a direct load and GEP accesses.
499 std::map<Argument*, ScalarizeTable> ScalarizedElements;
501 // OriginalLoads - Keep track of a representative load instruction from the
502 // original function so that we can tell the alias analysis implementation
503 // what the new GEP/Load instructions we are inserting look like.
504 std::map<IndicesVector, LoadInst*> OriginalLoads;
506 // Attributes - Keep track of the parameter attributes for the arguments
507 // that we are *not* promoting. For the ones that we do promote, the parameter
508 // attributes are lost
509 SmallVector<AttributeWithIndex, 8> AttributesVec;
510 const AttrListPtr &PAL = F->getAttributes();
512 // Add any return attributes.
513 if (Attributes attrs = PAL.getRetAttributes())
514 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
516 // First, determine the new argument list
517 unsigned ArgIndex = 1;
518 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
520 if (ByValArgsToTransform.count(I)) {
521 // Simple byval argument? Just add all the struct element types.
522 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
523 const StructType *STy = cast<StructType>(AgTy);
524 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
525 Params.push_back(STy->getElementType(i));
526 ++NumByValArgsPromoted;
527 } else if (!ArgsToPromote.count(I)) {
528 // Unchanged argument
529 Params.push_back(I->getType());
530 if (Attributes attrs = PAL.getParamAttributes(ArgIndex))
531 AttributesVec.push_back(AttributeWithIndex::get(Params.size(), attrs));
532 } else if (I->use_empty()) {
533 // Dead argument (which are always marked as promotable)
536 // Okay, this is being promoted. This means that the only uses are loads
537 // or GEPs which are only used by loads
539 // In this table, we will track which indices are loaded from the argument
540 // (where direct loads are tracked as no indices).
541 ScalarizeTable &ArgIndices = ScalarizedElements[I];
542 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
544 Instruction *User = cast<Instruction>(*UI);
545 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
546 IndicesVector Indices;
547 Indices.reserve(User->getNumOperands() - 1);
548 // Since loads will only have a single operand, and GEPs only a single
549 // non-index operand, this will record direct loads without any indices,
550 // and gep+loads with the GEP indices.
551 for (User::op_iterator II = User->op_begin() + 1, IE = User->op_end();
553 Indices.push_back(cast<ConstantInt>(*II)->getSExtValue());
554 // GEPs with a single 0 index can be merged with direct loads
555 if (Indices.size() == 1 && Indices.front() == 0)
557 ArgIndices.insert(Indices);
559 if (LoadInst *L = dyn_cast<LoadInst>(User))
562 // Take any load, we will use it only to update Alias Analysis
563 OrigLoad = cast<LoadInst>(User->use_back());
564 OriginalLoads[Indices] = OrigLoad;
567 // Add a parameter to the function for each element passed in.
568 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
569 E = ArgIndices.end(); SI != E; ++SI) {
570 // not allowed to dereference ->begin() if size() is 0
571 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(),
574 assert(Params.back());
577 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
578 ++NumArgumentsPromoted;
580 ++NumAggregatesPromoted;
584 // Add any function attributes.
585 if (Attributes attrs = PAL.getFnAttributes())
586 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
588 const Type *RetTy = FTy->getReturnType();
590 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
591 // have zero fixed arguments.
592 bool ExtraArgHack = false;
593 if (Params.empty() && FTy->isVarArg()) {
595 Params.push_back(Type::getInt32Ty(F->getContext()));
598 // Construct the new function type using the new arguments.
599 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
601 // Create the new function body and insert it into the module.
602 Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
603 NF->copyAttributesFrom(F);
606 DEBUG(dbgs() << "ARG PROMOTION: Promoting to:" << *NF << "\n"
609 // Recompute the parameter attributes list based on the new arguments for
611 NF->setAttributes(AttrListPtr::get(AttributesVec.begin(),
612 AttributesVec.end()));
613 AttributesVec.clear();
615 F->getParent()->getFunctionList().insert(F, NF);
618 // Get the alias analysis information that we need to update to reflect our
620 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
622 // Get the callgraph information that we need to update to reflect our
624 CallGraph &CG = getAnalysis<CallGraph>();
626 // Get a new callgraph node for NF.
627 CallGraphNode *NF_CGN = CG.getOrInsertFunction(NF);
629 // Loop over all of the callers of the function, transforming the call sites
630 // to pass in the loaded pointers.
632 SmallVector<Value*, 16> Args;
633 while (!F->use_empty()) {
634 CallSite CS(F->use_back());
635 assert(CS.getCalledFunction() == F);
636 Instruction *Call = CS.getInstruction();
637 const AttrListPtr &CallPAL = CS.getAttributes();
639 // Add any return attributes.
640 if (Attributes attrs = CallPAL.getRetAttributes())
641 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
643 // Loop over the operands, inserting GEP and loads in the caller as
645 CallSite::arg_iterator AI = CS.arg_begin();
647 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
648 I != E; ++I, ++AI, ++ArgIndex)
649 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
650 Args.push_back(*AI); // Unmodified argument
652 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
653 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
655 } else if (ByValArgsToTransform.count(I)) {
656 // Emit a GEP and load for each element of the struct.
657 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
658 const StructType *STy = cast<StructType>(AgTy);
660 ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
661 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
662 Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
663 Value *Idx = GetElementPtrInst::Create(*AI, Idxs, Idxs+2,
664 (*AI)->getName()+"."+utostr(i),
666 // TODO: Tell AA about the new values?
667 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
669 } else if (!I->use_empty()) {
670 // Non-dead argument: insert GEPs and loads as appropriate.
671 ScalarizeTable &ArgIndices = ScalarizedElements[I];
672 // Store the Value* version of the indices in here, but declare it now
674 std::vector<Value*> Ops;
675 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
676 E = ArgIndices.end(); SI != E; ++SI) {
678 LoadInst *OrigLoad = OriginalLoads[*SI];
680 Ops.reserve(SI->size());
681 const Type *ElTy = V->getType();
682 for (IndicesVector::const_iterator II = SI->begin(),
683 IE = SI->end(); II != IE; ++II) {
684 // Use i32 to index structs, and i64 for others (pointers/arrays).
685 // This satisfies GEP constraints.
686 const Type *IdxTy = (ElTy->isStructTy() ?
687 Type::getInt32Ty(F->getContext()) :
688 Type::getInt64Ty(F->getContext()));
689 Ops.push_back(ConstantInt::get(IdxTy, *II));
690 // Keep track of the type we're currently indexing.
691 ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(*II);
693 // And create a GEP to extract those indices.
694 V = GetElementPtrInst::Create(V, Ops.begin(), Ops.end(),
695 V->getName()+".idx", Call);
697 AA.copyValue(OrigLoad->getOperand(0), V);
699 // Since we're replacing a load make sure we take the alignment
700 // of the previous load.
701 LoadInst *newLoad = new LoadInst(V, V->getName()+".val", Call);
702 newLoad->setAlignment(OrigLoad->getAlignment());
703 Args.push_back(newLoad);
704 AA.copyValue(OrigLoad, Args.back());
709 Args.push_back(Constant::getNullValue(Type::getInt32Ty(F->getContext())));
711 // Push any varargs arguments on the list.
712 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
714 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
715 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
718 // Add any function attributes.
719 if (Attributes attrs = CallPAL.getFnAttributes())
720 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
723 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
724 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
725 Args.begin(), Args.end(), "", Call);
726 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
727 cast<InvokeInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
728 AttributesVec.end()));
730 New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
731 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
732 cast<CallInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
733 AttributesVec.end()));
734 if (cast<CallInst>(Call)->isTailCall())
735 cast<CallInst>(New)->setTailCall();
738 AttributesVec.clear();
740 // Update the alias analysis implementation to know that we are replacing
741 // the old call with a new one.
742 AA.replaceWithNewValue(Call, New);
744 // Update the callgraph to know that the callsite has been transformed.
745 CallGraphNode *CalleeNode = CG[Call->getParent()->getParent()];
746 CalleeNode->replaceCallEdge(Call, New, NF_CGN);
748 if (!Call->use_empty()) {
749 Call->replaceAllUsesWith(New);
753 // Finally, remove the old call from the program, reducing the use-count of
755 Call->eraseFromParent();
758 // Since we have now created the new function, splice the body of the old
759 // function right into the new function, leaving the old rotting hulk of the
761 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
763 // Loop over the argument list, transfering uses of the old arguments over to
764 // the new arguments, also transfering over the names as well.
766 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
767 I2 = NF->arg_begin(); I != E; ++I) {
768 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
769 // If this is an unmodified argument, move the name and users over to the
771 I->replaceAllUsesWith(I2);
773 AA.replaceWithNewValue(I, I2);
778 if (ByValArgsToTransform.count(I)) {
779 // In the callee, we create an alloca, and store each of the new incoming
780 // arguments into the alloca.
781 Instruction *InsertPt = NF->begin()->begin();
783 // Just add all the struct element types.
784 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
785 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
786 const StructType *STy = cast<StructType>(AgTy);
788 ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
790 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
791 Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
793 GetElementPtrInst::Create(TheAlloca, Idxs, Idxs+2,
794 TheAlloca->getName()+"."+Twine(i),
796 I2->setName(I->getName()+"."+Twine(i));
797 new StoreInst(I2++, Idx, InsertPt);
800 // Anything that used the arg should now use the alloca.
801 I->replaceAllUsesWith(TheAlloca);
802 TheAlloca->takeName(I);
803 AA.replaceWithNewValue(I, TheAlloca);
807 if (I->use_empty()) {
812 // Otherwise, if we promoted this argument, then all users are load
813 // instructions (or GEPs with only load users), and all loads should be
814 // using the new argument that we added.
815 ScalarizeTable &ArgIndices = ScalarizedElements[I];
817 while (!I->use_empty()) {
818 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
819 assert(ArgIndices.begin()->empty() &&
820 "Load element should sort to front!");
821 I2->setName(I->getName()+".val");
822 LI->replaceAllUsesWith(I2);
823 AA.replaceWithNewValue(LI, I2);
824 LI->eraseFromParent();
825 DEBUG(dbgs() << "*** Promoted load of argument '" << I->getName()
826 << "' in function '" << F->getName() << "'\n");
828 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
829 IndicesVector Operands;
830 Operands.reserve(GEP->getNumIndices());
831 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
833 Operands.push_back(cast<ConstantInt>(*II)->getSExtValue());
835 // GEPs with a single 0 index can be merged with direct loads
836 if (Operands.size() == 1 && Operands.front() == 0)
839 Function::arg_iterator TheArg = I2;
840 for (ScalarizeTable::iterator It = ArgIndices.begin();
841 *It != Operands; ++It, ++TheArg) {
842 assert(It != ArgIndices.end() && "GEP not handled??");
845 std::string NewName = I->getName();
846 for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
847 NewName += "." + utostr(Operands[i]);
850 TheArg->setName(NewName);
852 DEBUG(dbgs() << "*** Promoted agg argument '" << TheArg->getName()
853 << "' of function '" << NF->getName() << "'\n");
855 // All of the uses must be load instructions. Replace them all with
856 // the argument specified by ArgNo.
857 while (!GEP->use_empty()) {
858 LoadInst *L = cast<LoadInst>(GEP->use_back());
859 L->replaceAllUsesWith(TheArg);
860 AA.replaceWithNewValue(L, TheArg);
861 L->eraseFromParent();
864 GEP->eraseFromParent();
868 // Increment I2 past all of the arguments added for this promoted pointer.
869 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
873 // Notify the alias analysis implementation that we inserted a new argument.
875 AA.copyValue(Constant::getNullValue(Type::getInt32Ty(F->getContext())),
879 // Tell the alias analysis that the old function is about to disappear.
880 AA.replaceWithNewValue(F, NF);
883 NF_CGN->stealCalledFunctionsFrom(CG[F]);
885 // Now that the old function is dead, delete it. If there is a dangling
886 // reference to the CallgraphNode, just leave the dead function around for
887 // someone else to nuke.
888 CallGraphNode *CGN = CG[F];
889 if (CGN->getNumReferences() == 0)
890 delete CG.removeFunctionFromModule(CGN);
892 F->setLinkage(Function::ExternalLinkage);