Fix comment for consistency sake.
[llvm/avr.git] / lib / Transforms / IPO / ArgumentPromotion.cpp
blob3c584c894af5022e69814ac13738ac1583d56e3a
1 //===-- ArgumentPromotion.cpp - Promote by-reference arguments ------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
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/Compiler.h"
45 #include "llvm/Support/CFG.h"
46 #include "llvm/Support/Debug.h"
47 #include "llvm/Support/raw_ostream.h"
48 #include "llvm/ADT/DepthFirstIterator.h"
49 #include "llvm/ADT/Statistic.h"
50 #include "llvm/ADT/StringExtras.h"
51 #include <set>
52 using namespace llvm;
54 STATISTIC(NumArgumentsPromoted , "Number of pointer arguments promoted");
55 STATISTIC(NumAggregatesPromoted, "Number of aggregate arguments promoted");
56 STATISTIC(NumByValArgsPromoted , "Number of byval arguments promoted");
57 STATISTIC(NumArgumentsDead , "Number of dead pointer args eliminated");
59 namespace {
60 /// ArgPromotion - The 'by reference' to 'by value' argument promotion pass.
61 ///
62 struct VISIBILITY_HIDDEN ArgPromotion : public CallGraphSCCPass {
63 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
64 AU.addRequired<AliasAnalysis>();
65 CallGraphSCCPass::getAnalysisUsage(AU);
68 virtual bool runOnSCC(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;
76 private:
77 CallGraphNode *PromoteArguments(CallGraphNode *CGN);
78 bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const;
79 CallGraphNode *DoPromotion(Function *F,
80 SmallPtrSet<Argument*, 8> &ArgsToPromote,
81 SmallPtrSet<Argument*, 8> &ByValArgsToTransform);
82 /// The maximum number of elements to expand, or 0 for unlimited.
83 unsigned maxElements;
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(std::vector<CallGraphNode *> &SCC) {
96 bool Changed = false, LocalChange;
98 do { // Iterate until we stop promoting from this SCC.
99 LocalChange = false;
100 // Attempt to promote arguments from all functions in this SCC.
101 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
102 if (CallGraphNode *CGN = PromoteArguments(SCC[i])) {
103 LocalChange = true;
104 SCC[i] = CGN;
106 Changed |= LocalChange; // Remember that we changed something.
107 } while (LocalChange);
109 return Changed;
112 /// PromoteArguments - This method checks the specified function to see if there
113 /// are any promotable arguments and if it is safe to promote the function (for
114 /// example, all callers are direct). If safe to promote some arguments, it
115 /// calls the DoPromotion method.
117 CallGraphNode *ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
118 Function *F = CGN->getFunction();
120 // Make sure that it is local to this module.
121 if (!F || !F->hasLocalLinkage()) return 0;
123 // First check: see if there are any pointer arguments! If not, quick exit.
124 SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs;
125 unsigned ArgNo = 0;
126 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
127 I != E; ++I, ++ArgNo)
128 if (isa<PointerType>(I->getType()))
129 PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo));
130 if (PointerArgs.empty()) return 0;
132 // Second check: make sure that all callers are direct callers. We can't
133 // transform functions that have indirect callers.
134 if (F->hasAddressTaken())
135 return 0;
137 // Check to see which arguments are promotable. If an argument is promotable,
138 // add it to ArgsToPromote.
139 SmallPtrSet<Argument*, 8> ArgsToPromote;
140 SmallPtrSet<Argument*, 8> ByValArgsToTransform;
141 for (unsigned i = 0; i != PointerArgs.size(); ++i) {
142 bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, Attribute::ByVal);
144 // If this is a byval argument, and if the aggregate type is small, just
145 // pass the elements, which is always safe.
146 Argument *PtrArg = PointerArgs[i].first;
147 if (isByVal) {
148 const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
149 if (const StructType *STy = dyn_cast<StructType>(AgTy)) {
150 if (maxElements > 0 && STy->getNumElements() > maxElements) {
151 DEBUG(errs() << "argpromotion disable promoting argument '"
152 << PtrArg->getName() << "' because it would require adding more"
153 << " than " << maxElements << " arguments to the function.\n");
154 } else {
155 // If all the elements are single-value types, we can promote it.
156 bool AllSimple = true;
157 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
158 if (!STy->getElementType(i)->isSingleValueType()) {
159 AllSimple = false;
160 break;
163 // Safe to transform, don't even bother trying to "promote" it.
164 // Passing the elements as a scalar will allow scalarrepl to hack on
165 // the new alloca we introduce.
166 if (AllSimple) {
167 ByValArgsToTransform.insert(PtrArg);
168 continue;
174 // Otherwise, see if we can promote the pointer to its value.
175 if (isSafeToPromoteArgument(PtrArg, isByVal))
176 ArgsToPromote.insert(PtrArg);
179 // No promotable pointer arguments.
180 if (ArgsToPromote.empty() && ByValArgsToTransform.empty())
181 return 0;
183 return DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
186 /// IsAlwaysValidPointer - Return true if the specified pointer is always legal
187 /// to load.
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));
196 return false;
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();
210 UI != E; ++UI) {
211 CallSite CS = CallSite::get(*UI);
212 assert(CS.getInstruction() && "Should only have direct calls!");
214 if (!IsAlwaysValidPointer(CS.getArgument(ArgNo)))
215 return false;
217 return true;
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())
228 return false;
229 for (unsigned i = 0, e = Prefix.size(); i != e; ++i)
230 if (Prefix[i] != Longer[i])
231 return false;
232 return true;
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())
242 Low--;
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
245 // prefix exists.
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())
262 Low--;
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
270 return;
272 // Increment Low, so we can use it as a "insert before" hint
273 ++Low;
275 // Insert
276 Low = Safe.insert(Low, ToMark);
277 ++Low;
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;
282 ++Low;
283 Safe.erase(Remove);
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())
297 return true;
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
306 // valid.
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
310 // original code.
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
325 // safe.
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();
330 I != E; ++I)
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();
335 if (V == Arg) {
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();
339 II != IE; ++II)
340 if (ConstantInt *CI = dyn_cast<ConstantInt>(*II))
341 Indices.push_back(CI->getSExtValue());
342 else
343 // We found a non-constant GEP index for this argument? Bail out
344 // right away, can't promote this argument at all.
345 return false;
347 // Indices checked out, mark them as safe
348 MarkIndicesSafe(Indices, SafeToUnconditionallyLoad);
349 Indices.clear();
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();
362 UI != E; ++UI) {
363 Operands.clear();
364 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
365 if (LI->isVolatile()) return false; // Don't hack volatile loads
366 Loads.push_back(LI);
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
372 // them.
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
377 // use?
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();
383 i != e; ++i)
384 if (ConstantInt *C = dyn_cast<ConstantInt>(*i))
385 Operands.push_back(C->getSExtValue());
386 else
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();
391 UI != E; ++UI)
392 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
393 if (LI->isVolatile()) return false; // Don't hack volatile loads
394 Loads.push_back(LI);
395 } else {
396 // Other uses than load?
397 return false;
399 } else {
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))
406 return false;
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
410 // to do.
411 if (ToPromote.find(Operands) == ToPromote.end()) {
412 if (maxElements > 0 && ToPromote.size() == maxElements) {
413 DEBUG(errs() << "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.
418 return false;
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 = getAnalysisIfAvailable<TargetData>();
437 if (!TD) return false; // Without TargetData, assume the worst.
439 for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
440 // Check to see if the load is invalidated from the start of the block to
441 // the load itself.
442 LoadInst *Load = Loads[i];
443 BasicBlock *BB = Load->getParent();
445 const PointerType *LoadTy =
446 cast<PointerType>(Load->getPointerOperand()->getType());
447 unsigned LoadSize =(unsigned)TD->getTypeStoreSize(LoadTy->getElementType());
449 if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize))
450 return false; // Pointer is invalidated!
452 // Now check every path from the entry block to the load for transparency.
453 // To do this, we perform a depth first search on the inverse CFG from the
454 // loading block.
455 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
456 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
457 I = idf_ext_begin(*PI, TranspBlocks),
458 E = idf_ext_end(*PI, TranspBlocks); I != E; ++I)
459 if (AA.canBasicBlockModify(**I, Arg, LoadSize))
460 return false;
463 // If the path from the entry of the function to each load is free of
464 // instructions that potentially invalidate the load, we can make the
465 // transformation!
466 return true;
469 /// DoPromotion - This method actually performs the promotion of the specified
470 /// arguments, and returns the new function. At this point, we know that it's
471 /// safe to do so.
472 CallGraphNode *ArgPromotion::DoPromotion(Function *F,
473 SmallPtrSet<Argument*, 8> &ArgsToPromote,
474 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
476 // Start by computing a new prototype for the function, which is the same as
477 // the old function, but has modified arguments.
478 const FunctionType *FTy = F->getFunctionType();
479 std::vector<const Type*> Params;
481 typedef std::set<IndicesVector> ScalarizeTable;
483 // ScalarizedElements - If we are promoting a pointer that has elements
484 // accessed out of it, keep track of which elements are accessed so that we
485 // can add one argument for each.
487 // Arguments that are directly loaded will have a zero element value here, to
488 // handle cases where there are both a direct load and GEP accesses.
490 std::map<Argument*, ScalarizeTable> ScalarizedElements;
492 // OriginalLoads - Keep track of a representative load instruction from the
493 // original function so that we can tell the alias analysis implementation
494 // what the new GEP/Load instructions we are inserting look like.
495 std::map<IndicesVector, LoadInst*> OriginalLoads;
497 // Attributes - Keep track of the parameter attributes for the arguments
498 // that we are *not* promoting. For the ones that we do promote, the parameter
499 // attributes are lost
500 SmallVector<AttributeWithIndex, 8> AttributesVec;
501 const AttrListPtr &PAL = F->getAttributes();
503 // Add any return attributes.
504 if (Attributes attrs = PAL.getRetAttributes())
505 AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
507 // First, determine the new argument list
508 unsigned ArgIndex = 1;
509 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
510 ++I, ++ArgIndex) {
511 if (ByValArgsToTransform.count(I)) {
512 // Simple byval argument? Just add all the struct element types.
513 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
514 const StructType *STy = cast<StructType>(AgTy);
515 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
516 Params.push_back(STy->getElementType(i));
517 ++NumByValArgsPromoted;
518 } else if (!ArgsToPromote.count(I)) {
519 // Unchanged argument
520 Params.push_back(I->getType());
521 if (Attributes attrs = PAL.getParamAttributes(ArgIndex))
522 AttributesVec.push_back(AttributeWithIndex::get(Params.size(), attrs));
523 } else if (I->use_empty()) {
524 // Dead argument (which are always marked as promotable)
525 ++NumArgumentsDead;
526 } else {
527 // Okay, this is being promoted. This means that the only uses are loads
528 // or GEPs which are only used by loads
530 // In this table, we will track which indices are loaded from the argument
531 // (where direct loads are tracked as no indices).
532 ScalarizeTable &ArgIndices = ScalarizedElements[I];
533 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
534 ++UI) {
535 Instruction *User = cast<Instruction>(*UI);
536 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
537 IndicesVector Indices;
538 Indices.reserve(User->getNumOperands() - 1);
539 // Since loads will only have a single operand, and GEPs only a single
540 // non-index operand, this will record direct loads without any indices,
541 // and gep+loads with the GEP indices.
542 for (User::op_iterator II = User->op_begin() + 1, IE = User->op_end();
543 II != IE; ++II)
544 Indices.push_back(cast<ConstantInt>(*II)->getSExtValue());
545 // GEPs with a single 0 index can be merged with direct loads
546 if (Indices.size() == 1 && Indices.front() == 0)
547 Indices.clear();
548 ArgIndices.insert(Indices);
549 LoadInst *OrigLoad;
550 if (LoadInst *L = dyn_cast<LoadInst>(User))
551 OrigLoad = L;
552 else
553 // Take any load, we will use it only to update Alias Analysis
554 OrigLoad = cast<LoadInst>(User->use_back());
555 OriginalLoads[Indices] = OrigLoad;
558 // Add a parameter to the function for each element passed in.
559 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
560 E = ArgIndices.end(); SI != E; ++SI) {
561 // not allowed to dereference ->begin() if size() is 0
562 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(),
563 SI->begin(),
564 SI->end()));
565 assert(Params.back());
568 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
569 ++NumArgumentsPromoted;
570 else
571 ++NumAggregatesPromoted;
575 // Add any function attributes.
576 if (Attributes attrs = PAL.getFnAttributes())
577 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
579 const Type *RetTy = FTy->getReturnType();
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()) {
585 ExtraArgHack = true;
586 Params.push_back(Type::getInt32Ty(F->getContext()));
589 // Construct the new function type using the new arguments.
590 FunctionType *NFTy = FunctionType::get(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);
597 DEBUG(errs() << "ARG PROMOTION: Promoting to:" << *NF << "\n"
598 << "From: " << *F);
600 // Recompute the parameter attributes list based on the new arguments for
601 // the function.
602 NF->setAttributes(AttrListPtr::get(AttributesVec.begin(), AttributesVec.end()));
603 AttributesVec.clear();
605 F->getParent()->getFunctionList().insert(F, NF);
606 NF->takeName(F);
608 // Get the alias analysis information that we need to update to reflect our
609 // changes.
610 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
612 // Get the callgraph information that we need to update to reflect our
613 // changes.
614 CallGraph &CG = getAnalysis<CallGraph>();
616 // Get a new callgraph node for NF.
617 CallGraphNode *NF_CGN = CG.getOrInsertFunction(NF);
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
634 // appropriate.
635 CallSite::arg_iterator AI = CS.arg_begin();
636 ArgIndex = 1;
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] = {
650 ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
651 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
652 Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
653 Value *Idx = GetElementPtrInst::Create(*AI, Idxs, Idxs+2,
654 (*AI)->getName()+"."+utostr(i),
655 Call);
656 // TODO: Tell AA about the new values?
657 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
659 } else if (!I->use_empty()) {
660 // Non-dead argument: insert GEPs and loads as appropriate.
661 ScalarizeTable &ArgIndices = ScalarizedElements[I];
662 // Store the Value* version of the indices in here, but declare it now
663 // for reuse
664 std::vector<Value*> Ops;
665 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
666 E = ArgIndices.end(); SI != E; ++SI) {
667 Value *V = *AI;
668 LoadInst *OrigLoad = OriginalLoads[*SI];
669 if (!SI->empty()) {
670 Ops.reserve(SI->size());
671 const Type *ElTy = V->getType();
672 for (IndicesVector::const_iterator II = SI->begin(),
673 IE = SI->end(); II != IE; ++II) {
674 // Use i32 to index structs, and i64 for others (pointers/arrays).
675 // This satisfies GEP constraints.
676 const Type *IdxTy = (isa<StructType>(ElTy) ?
677 Type::getInt32Ty(F->getContext()) :
678 Type::getInt64Ty(F->getContext()));
679 Ops.push_back(ConstantInt::get(IdxTy, *II));
680 // Keep track of the type we're currently indexing
681 ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(*II);
683 // And create a GEP to extract those indices
684 V = GetElementPtrInst::Create(V, Ops.begin(), Ops.end(),
685 V->getName()+".idx", Call);
686 Ops.clear();
687 AA.copyValue(OrigLoad->getOperand(0), V);
689 Args.push_back(new LoadInst(V, V->getName()+".val", Call));
690 AA.copyValue(OrigLoad, Args.back());
694 if (ExtraArgHack)
695 Args.push_back(Constant::getNullValue(Type::getInt32Ty(F->getContext())));
697 // Push any varargs arguments on the list
698 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
699 Args.push_back(*AI);
700 if (Attributes Attrs = CallPAL.getParamAttributes(ArgIndex))
701 AttributesVec.push_back(AttributeWithIndex::get(Args.size(), Attrs));
704 // Add any function attributes.
705 if (Attributes attrs = CallPAL.getFnAttributes())
706 AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
708 Instruction *New;
709 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
710 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
711 Args.begin(), Args.end(), "", Call);
712 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
713 cast<InvokeInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
714 AttributesVec.end()));
715 } else {
716 New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
717 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
718 cast<CallInst>(New)->setAttributes(AttrListPtr::get(AttributesVec.begin(),
719 AttributesVec.end()));
720 if (cast<CallInst>(Call)->isTailCall())
721 cast<CallInst>(New)->setTailCall();
723 Args.clear();
724 AttributesVec.clear();
726 // Update the alias analysis implementation to know that we are replacing
727 // the old call with a new one.
728 AA.replaceWithNewValue(Call, New);
730 // Update the callgraph to know that the callsite has been transformed.
731 CallGraphNode *CalleeNode = CG[Call->getParent()->getParent()];
732 CalleeNode->removeCallEdgeFor(Call);
733 CalleeNode->addCalledFunction(New, NF_CGN);
735 if (!Call->use_empty()) {
736 Call->replaceAllUsesWith(New);
737 New->takeName(Call);
740 // Finally, remove the old call from the program, reducing the use-count of
741 // F.
742 Call->eraseFromParent();
745 // Since we have now created the new function, splice the body of the old
746 // function right into the new function, leaving the old rotting hulk of the
747 // function empty.
748 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
750 // Loop over the argument list, transfering uses of the old arguments over to
751 // the new arguments, also transfering over the names as well.
753 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
754 I2 = NF->arg_begin(); I != E; ++I) {
755 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
756 // If this is an unmodified argument, move the name and users over to the
757 // new version.
758 I->replaceAllUsesWith(I2);
759 I2->takeName(I);
760 AA.replaceWithNewValue(I, I2);
761 ++I2;
762 continue;
765 if (ByValArgsToTransform.count(I)) {
766 // In the callee, we create an alloca, and store each of the new incoming
767 // arguments into the alloca.
768 Instruction *InsertPt = NF->begin()->begin();
770 // Just add all the struct element types.
771 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
772 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
773 const StructType *STy = cast<StructType>(AgTy);
774 Value *Idxs[2] = {
775 ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
777 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
778 Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
779 Value *Idx =
780 GetElementPtrInst::Create(TheAlloca, Idxs, Idxs+2,
781 TheAlloca->getName()+"."+Twine(i),
782 InsertPt);
783 I2->setName(I->getName()+"."+Twine(i));
784 new StoreInst(I2++, Idx, InsertPt);
787 // Anything that used the arg should now use the alloca.
788 I->replaceAllUsesWith(TheAlloca);
789 TheAlloca->takeName(I);
790 AA.replaceWithNewValue(I, TheAlloca);
791 continue;
794 if (I->use_empty()) {
795 AA.deleteValue(I);
796 continue;
799 // Otherwise, if we promoted this argument, then all users are load
800 // instructions (or GEPs with only load users), and all loads should be
801 // using the new argument that we added.
802 ScalarizeTable &ArgIndices = ScalarizedElements[I];
804 while (!I->use_empty()) {
805 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
806 assert(ArgIndices.begin()->empty() &&
807 "Load element should sort to front!");
808 I2->setName(I->getName()+".val");
809 LI->replaceAllUsesWith(I2);
810 AA.replaceWithNewValue(LI, I2);
811 LI->eraseFromParent();
812 DEBUG(errs() << "*** Promoted load of argument '" << I->getName()
813 << "' in function '" << F->getName() << "'\n");
814 } else {
815 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
816 IndicesVector Operands;
817 Operands.reserve(GEP->getNumIndices());
818 for (User::op_iterator II = GEP->idx_begin(), IE = GEP->idx_end();
819 II != IE; ++II)
820 Operands.push_back(cast<ConstantInt>(*II)->getSExtValue());
822 // GEPs with a single 0 index can be merged with direct loads
823 if (Operands.size() == 1 && Operands.front() == 0)
824 Operands.clear();
826 Function::arg_iterator TheArg = I2;
827 for (ScalarizeTable::iterator It = ArgIndices.begin();
828 *It != Operands; ++It, ++TheArg) {
829 assert(It != ArgIndices.end() && "GEP not handled??");
832 std::string NewName = I->getName();
833 for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
834 NewName += "." + utostr(Operands[i]);
836 NewName += ".val";
837 TheArg->setName(NewName);
839 DEBUG(errs() << "*** Promoted agg argument '" << TheArg->getName()
840 << "' of function '" << NF->getName() << "'\n");
842 // All of the uses must be load instructions. Replace them all with
843 // the argument specified by ArgNo.
844 while (!GEP->use_empty()) {
845 LoadInst *L = cast<LoadInst>(GEP->use_back());
846 L->replaceAllUsesWith(TheArg);
847 AA.replaceWithNewValue(L, TheArg);
848 L->eraseFromParent();
850 AA.deleteValue(GEP);
851 GEP->eraseFromParent();
855 // Increment I2 past all of the arguments added for this promoted pointer.
856 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
857 ++I2;
860 // Notify the alias analysis implementation that we inserted a new argument.
861 if (ExtraArgHack)
862 AA.copyValue(Constant::getNullValue(Type::getInt32Ty(F->getContext())),
863 NF->arg_begin());
866 // Tell the alias analysis that the old function is about to disappear.
867 AA.replaceWithNewValue(F, NF);
870 NF_CGN->stealCalledFunctionsFrom(CG[F]);
872 // Now that the old function is dead, delete it.
873 delete CG.removeFunctionFromModule(F);
875 return NF_CGN;