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 more than
21 // three operands to the function, because passing thousands of operands for a
22 // large array or structure is unprofitable! This limit is can be configured or
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 ArgPromotion(unsigned maxElements = 3) : CallGraphSCCPass((intptr_t)&ID),
70 maxElements(maxElements) {}
73 bool PromoteArguments(CallGraphNode *CGN);
74 bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const;
75 Function *DoPromotion(Function *F,
76 SmallPtrSet<Argument*, 8> &ArgsToPromote,
77 SmallPtrSet<Argument*, 8> &ByValArgsToTransform);
78 /// The maximum number of elements to expand, or 0 for unlimited.
83 char ArgPromotion::ID = 0;
84 static RegisterPass<ArgPromotion>
85 X("argpromotion", "Promote 'by reference' arguments to scalars");
87 Pass *llvm::createArgumentPromotionPass(unsigned maxElements) {
88 return new ArgPromotion(maxElements);
91 bool ArgPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
92 bool Changed = false, LocalChange;
94 do { // Iterate until we stop promoting from this SCC.
96 // Attempt to promote arguments from all functions in this SCC.
97 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
98 LocalChange |= PromoteArguments(SCC[i]);
99 Changed |= LocalChange; // Remember that we changed something.
100 } while (LocalChange);
105 /// PromoteArguments - This method checks the specified function to see if there
106 /// are any promotable arguments and if it is safe to promote the function (for
107 /// example, all callers are direct). If safe to promote some arguments, it
108 /// calls the DoPromotion method.
110 bool ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
111 Function *F = CGN->getFunction();
113 // Make sure that it is local to this module.
114 if (!F || !F->hasInternalLinkage()) return false;
116 // First check: see if there are any pointer arguments! If not, quick exit.
117 SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs;
119 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
120 I != E; ++I, ++ArgNo)
121 if (isa<PointerType>(I->getType()))
122 PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo));
123 if (PointerArgs.empty()) return false;
125 // Second check: make sure that all callers are direct callers. We can't
126 // transform functions that have indirect callers.
127 for (Value::use_iterator UI = F->use_begin(), E = F->use_end();
129 CallSite CS = CallSite::get(*UI);
130 if (!CS.getInstruction()) // "Taking the address" of the function
133 // Ensure that this call site is CALLING the function, not passing it as
135 if (UI.getOperandNo() != 0)
139 // Check to see which arguments are promotable. If an argument is promotable,
140 // add it to ArgsToPromote.
141 SmallPtrSet<Argument*, 8> ArgsToPromote;
142 SmallPtrSet<Argument*, 8> ByValArgsToTransform;
143 for (unsigned i = 0; i != PointerArgs.size(); ++i) {
144 bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, ParamAttr::ByVal);
146 // If this is a byval argument, and if the aggregate type is small, just
147 // pass the elements, which is always safe.
148 Argument *PtrArg = PointerArgs[i].first;
150 const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
151 if (const StructType *STy = dyn_cast<StructType>(AgTy)) {
152 if (maxElements > 0 && STy->getNumElements() > maxElements) {
153 DOUT << "argpromotion disable promoting argument '"
154 << PtrArg->getName() << "' because it would require adding more "
155 << "than " << maxElements << " arguments to the function.\n";
157 // If all the elements are single-value types, we can promote it.
158 bool AllSimple = true;
159 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
160 if (!STy->getElementType(i)->isSingleValueType()) {
165 // Safe to transform, don't even bother trying to "promote" it.
166 // Passing the elements as a scalar will allow scalarrepl to hack on
167 // the new alloca we introduce.
169 ByValArgsToTransform.insert(PtrArg);
176 // Otherwise, see if we can promote the pointer to its value.
177 if (isSafeToPromoteArgument(PtrArg, isByVal))
178 ArgsToPromote.insert(PtrArg);
181 // No promotable pointer arguments.
182 if (ArgsToPromote.empty() && ByValArgsToTransform.empty()) return false;
184 Function *NewF = DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
186 // Update the call graph to know that the function has been transformed.
187 getAnalysis<CallGraph>().changeFunction(F, NewF);
191 /// IsAlwaysValidPointer - Return true if the specified pointer is always legal
193 static bool IsAlwaysValidPointer(Value *V) {
194 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
195 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V))
196 return IsAlwaysValidPointer(GEP->getOperand(0));
197 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
198 if (CE->getOpcode() == Instruction::GetElementPtr)
199 return IsAlwaysValidPointer(CE->getOperand(0));
204 /// AllCalleesPassInValidPointerForArgument - Return true if we can prove that
205 /// all callees pass in a valid pointer for the specified function argument.
206 static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
207 Function *Callee = Arg->getParent();
209 unsigned ArgNo = std::distance(Callee->arg_begin(),
210 Function::arg_iterator(Arg));
212 // Look at all call sites of the function. At this pointer we know we only
213 // have direct callees.
214 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
216 CallSite CS = CallSite::get(*UI);
217 assert(CS.getInstruction() && "Should only have direct calls!");
219 if (!IsAlwaysValidPointer(CS.getArgument(ArgNo)))
226 /// isSafeToPromoteArgument - As you might guess from the name of this method,
227 /// it checks to see if it is both safe and useful to promote the argument.
228 /// This method limits promotion of aggregates to only promote up to three
229 /// elements of the aggregate in order to avoid exploding the number of
230 /// arguments passed in.
231 bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
232 // We can only promote this argument if all of the uses are loads, or are GEP
233 // instructions (with constant indices) that are subsequently loaded.
235 // We can also only promote the load if we can guarantee that it will happen.
236 // Promoting a load causes the load to be unconditionally executed in the
237 // caller, so we can't turn a conditional load into an unconditional load in
239 bool SafeToUnconditionallyLoad = false;
240 if (isByVal) // ByVal arguments are always safe to load from.
241 SafeToUnconditionallyLoad = true;
243 BasicBlock *EntryBlock = Arg->getParent()->begin();
244 SmallVector<LoadInst*, 16> Loads;
245 std::vector<SmallVector<ConstantInt*, 8> > GEPIndices;
246 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
248 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
249 if (LI->isVolatile()) return false; // Don't hack volatile loads
252 // If this load occurs in the entry block, then the pointer is
253 // unconditionally loaded.
254 SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock;
255 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
256 if (GEP->use_empty()) {
257 // Dead GEP's cause trouble later. Just remove them if we run into
259 getAnalysis<AliasAnalysis>().deleteValue(GEP);
260 GEP->eraseFromParent();
261 return isSafeToPromoteArgument(Arg, isByVal);
263 // Ensure that all of the indices are constants.
264 SmallVector<ConstantInt*, 8> Operands;
265 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
266 if (ConstantInt *C = dyn_cast<ConstantInt>(GEP->getOperand(i)))
267 Operands.push_back(C);
269 return false; // Not a constant operand GEP!
271 // Ensure that the only users of the GEP are load instructions.
272 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
274 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
275 if (LI->isVolatile()) return false; // Don't hack volatile loads
278 // If this load occurs in the entry block, then the pointer is
279 // unconditionally loaded.
280 SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock;
285 // See if there is already a GEP with these indices. If not, check to
286 // make sure that we aren't promoting too many elements. If so, nothing
288 if (std::find(GEPIndices.begin(), GEPIndices.end(), Operands) ==
290 if (maxElements > 0 && GEPIndices.size() == maxElements) {
291 DOUT << "argpromotion disable promoting argument '"
292 << Arg->getName() << "' because it would require adding more "
293 << "than " << maxElements << " arguments to the function.\n";
294 // We limit aggregate promotion to only promoting up to a fixed number
295 // of elements of the aggregate.
298 GEPIndices.push_back(Operands);
301 return false; // Not a load or a GEP.
304 if (Loads.empty()) return true; // No users, this is a dead argument.
306 // If we decide that we want to promote this argument, the value is going to
307 // be unconditionally loaded in all callees. This is only safe to do if the
308 // pointer was going to be unconditionally loaded anyway (i.e. there is a load
309 // of the pointer in the entry block of the function) or if we can prove that
310 // all pointers passed in are always to legal locations (for example, no null
311 // pointers are passed in, no pointers to free'd memory, etc).
312 if (!SafeToUnconditionallyLoad &&
313 !AllCalleesPassInValidPointerForArgument(Arg))
314 return false; // Cannot prove that this is safe!!
316 // Okay, now we know that the argument is only used by load instructions and
317 // it is safe to unconditionally load the pointer. Use alias analysis to
318 // check to see if the pointer is guaranteed to not be modified from entry of
319 // the function to each of the load instructions.
321 // Because there could be several/many load instructions, remember which
322 // blocks we know to be transparent to the load.
323 SmallPtrSet<BasicBlock*, 16> TranspBlocks;
325 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
326 TargetData &TD = getAnalysis<TargetData>();
328 for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
329 // Check to see if the load is invalidated from the start of the block to
331 LoadInst *Load = Loads[i];
332 BasicBlock *BB = Load->getParent();
334 const PointerType *LoadTy =
335 cast<PointerType>(Load->getOperand(0)->getType());
336 unsigned LoadSize = (unsigned)TD.getTypeStoreSize(LoadTy->getElementType());
338 if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize))
339 return false; // Pointer is invalidated!
341 // Now check every path from the entry block to the load for transparency.
342 // To do this, we perform a depth first search on the inverse CFG from the
344 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
345 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
346 I = idf_ext_begin(*PI, TranspBlocks),
347 E = idf_ext_end(*PI, TranspBlocks); I != E; ++I)
348 if (AA.canBasicBlockModify(**I, Arg, LoadSize))
352 // If the path from the entry of the function to each load is free of
353 // instructions that potentially invalidate the load, we can make the
359 /// GEPIdxComparator - Provide a strong ordering for GEP indices. All Value*
360 /// elements are instances of ConstantInt.
362 struct GEPIdxComparator {
363 bool operator()(const std::vector<Value*> &LHS,
364 const std::vector<Value*> &RHS) const {
366 for (; idx < LHS.size() && idx < RHS.size(); ++idx) {
367 if (LHS[idx] != RHS[idx]) {
368 return cast<ConstantInt>(LHS[idx])->getZExtValue() <
369 cast<ConstantInt>(RHS[idx])->getZExtValue();
373 // Return less than if we ran out of stuff in LHS and we didn't run out of
375 return idx == LHS.size() && idx != RHS.size();
381 /// DoPromotion - This method actually performs the promotion of the specified
382 /// arguments, and returns the new function. At this point, we know that it's
384 Function *ArgPromotion::DoPromotion(Function *F,
385 SmallPtrSet<Argument*, 8> &ArgsToPromote,
386 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
388 // Start by computing a new prototype for the function, which is the same as
389 // the old function, but has modified arguments.
390 const FunctionType *FTy = F->getFunctionType();
391 std::vector<const Type*> Params;
393 typedef std::set<std::vector<Value*>, GEPIdxComparator> ScalarizeTable;
395 // ScalarizedElements - If we are promoting a pointer that has elements
396 // accessed out of it, keep track of which elements are accessed so that we
397 // can add one argument for each.
399 // Arguments that are directly loaded will have a zero element value here, to
400 // handle cases where there are both a direct load and GEP accesses.
402 std::map<Argument*, ScalarizeTable> ScalarizedElements;
404 // OriginalLoads - Keep track of a representative load instruction from the
405 // original function so that we can tell the alias analysis implementation
406 // what the new GEP/Load instructions we are inserting look like.
407 std::map<std::vector<Value*>, LoadInst*> OriginalLoads;
409 // ParamAttrs - Keep track of the parameter attributes for the arguments
410 // that we are *not* promoting. For the ones that we do promote, the parameter
411 // attributes are lost
412 SmallVector<ParamAttrsWithIndex, 8> ParamAttrsVec;
413 const PAListPtr &PAL = F->getParamAttrs();
415 // Add any return attributes.
416 if (ParameterAttributes attrs = PAL.getParamAttrs(0))
417 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
419 unsigned ArgIndex = 1;
420 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
422 if (ByValArgsToTransform.count(I)) {
423 // Just add all the struct element types.
424 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
425 const StructType *STy = cast<StructType>(AgTy);
426 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
427 Params.push_back(STy->getElementType(i));
428 ++NumByValArgsPromoted;
429 } else if (!ArgsToPromote.count(I)) {
430 Params.push_back(I->getType());
431 if (ParameterAttributes attrs = PAL.getParamAttrs(ArgIndex))
432 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), attrs));
433 } else if (I->use_empty()) {
436 // Okay, this is being promoted. Check to see if there are any GEP uses
438 ScalarizeTable &ArgIndices = ScalarizedElements[I];
439 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
441 Instruction *User = cast<Instruction>(*UI);
442 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
443 std::vector<Value*> Indices(User->op_begin()+1, User->op_end());
444 ArgIndices.insert(Indices);
446 if (LoadInst *L = dyn_cast<LoadInst>(User))
449 OrigLoad = cast<LoadInst>(User->use_back());
450 OriginalLoads[Indices] = OrigLoad;
453 // Add a parameter to the function for each element passed in.
454 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
455 E = ArgIndices.end(); SI != E; ++SI)
456 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(),
460 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
461 ++NumArgumentsPromoted;
463 ++NumAggregatesPromoted;
467 const Type *RetTy = FTy->getReturnType();
469 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
470 // have zero fixed arguments.
471 bool ExtraArgHack = false;
472 if (Params.empty() && FTy->isVarArg()) {
474 Params.push_back(Type::Int32Ty);
477 // Construct the new function type using the new arguments.
478 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
480 // Create the new function body and insert it into the module...
481 Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
482 NF->copyAttributesFrom(F);
484 // Recompute the parameter attributes list based on the new arguments for
486 NF->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end()));
487 ParamAttrsVec.clear();
489 F->getParent()->getFunctionList().insert(F, NF);
492 // Get the alias analysis information that we need to update to reflect our
494 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
496 // Loop over all of the callers of the function, transforming the call sites
497 // to pass in the loaded pointers.
499 SmallVector<Value*, 16> Args;
500 while (!F->use_empty()) {
501 CallSite CS = CallSite::get(F->use_back());
502 Instruction *Call = CS.getInstruction();
503 const PAListPtr &CallPAL = CS.getParamAttrs();
505 // Add any return attributes.
506 if (ParameterAttributes attrs = CallPAL.getParamAttrs(0))
507 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
509 // Loop over the operands, inserting GEP and loads in the caller as
511 CallSite::arg_iterator AI = CS.arg_begin();
513 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
514 I != E; ++I, ++AI, ++ArgIndex)
515 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
516 Args.push_back(*AI); // Unmodified argument
518 if (ParameterAttributes Attrs = CallPAL.getParamAttrs(ArgIndex))
519 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
521 } else if (ByValArgsToTransform.count(I)) {
522 // Emit a GEP and load for each element of the struct.
523 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
524 const StructType *STy = cast<StructType>(AgTy);
525 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
526 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
527 Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
528 Value *Idx = GetElementPtrInst::Create(*AI, Idxs, Idxs+2,
529 (*AI)->getName()+"."+utostr(i),
531 // TODO: Tell AA about the new values?
532 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
534 } else if (!I->use_empty()) {
535 // Non-dead argument: insert GEPs and loads as appropriate.
536 ScalarizeTable &ArgIndices = ScalarizedElements[I];
537 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
538 E = ArgIndices.end(); SI != E; ++SI) {
540 LoadInst *OrigLoad = OriginalLoads[*SI];
542 V = GetElementPtrInst::Create(V, SI->begin(), SI->end(),
543 V->getName()+".idx", Call);
544 AA.copyValue(OrigLoad->getOperand(0), V);
546 Args.push_back(new LoadInst(V, V->getName()+".val", Call));
547 AA.copyValue(OrigLoad, Args.back());
552 Args.push_back(Constant::getNullValue(Type::Int32Ty));
554 // Push any varargs arguments on the list
555 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
557 if (ParameterAttributes Attrs = CallPAL.getParamAttrs(ArgIndex))
558 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
562 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
563 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
564 Args.begin(), Args.end(), "", Call);
565 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
566 cast<InvokeInst>(New)->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(),
567 ParamAttrsVec.end()));
569 New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
570 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
571 cast<CallInst>(New)->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(),
572 ParamAttrsVec.end()));
573 if (cast<CallInst>(Call)->isTailCall())
574 cast<CallInst>(New)->setTailCall();
577 ParamAttrsVec.clear();
579 // Update the alias analysis implementation to know that we are replacing
580 // the old call with a new one.
581 AA.replaceWithNewValue(Call, New);
583 if (!Call->use_empty()) {
584 Call->replaceAllUsesWith(New);
588 // Finally, remove the old call from the program, reducing the use-count of
590 Call->eraseFromParent();
593 // Since we have now created the new function, splice the body of the old
594 // function right into the new function, leaving the old rotting hulk of the
596 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
598 // Loop over the argument list, transfering uses of the old arguments over to
599 // the new arguments, also transfering over the names as well.
601 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
602 I2 = NF->arg_begin(); I != E; ++I) {
603 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
604 // If this is an unmodified argument, move the name and users over to the
606 I->replaceAllUsesWith(I2);
608 AA.replaceWithNewValue(I, I2);
613 if (ByValArgsToTransform.count(I)) {
614 // In the callee, we create an alloca, and store each of the new incoming
615 // arguments into the alloca.
616 Instruction *InsertPt = NF->begin()->begin();
618 // Just add all the struct element types.
619 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
620 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
621 const StructType *STy = cast<StructType>(AgTy);
622 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
624 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
625 Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
626 Value *Idx = GetElementPtrInst::Create(TheAlloca, Idxs, Idxs+2,
627 TheAlloca->getName()+"."+utostr(i),
629 I2->setName(I->getName()+"."+utostr(i));
630 new StoreInst(I2++, Idx, InsertPt);
633 // Anything that used the arg should now use the alloca.
634 I->replaceAllUsesWith(TheAlloca);
635 TheAlloca->takeName(I);
636 AA.replaceWithNewValue(I, TheAlloca);
640 if (I->use_empty()) {
645 // Otherwise, if we promoted this argument, then all users are load
646 // instructions, and all loads should be using the new argument that we
648 ScalarizeTable &ArgIndices = ScalarizedElements[I];
650 while (!I->use_empty()) {
651 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
652 assert(ArgIndices.begin()->empty() &&
653 "Load element should sort to front!");
654 I2->setName(I->getName()+".val");
655 LI->replaceAllUsesWith(I2);
656 AA.replaceWithNewValue(LI, I2);
657 LI->eraseFromParent();
658 DOUT << "*** Promoted load of argument '" << I->getName()
659 << "' in function '" << F->getName() << "'\n";
661 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
662 std::vector<Value*> Operands(GEP->op_begin()+1, GEP->op_end());
664 Function::arg_iterator TheArg = I2;
665 for (ScalarizeTable::iterator It = ArgIndices.begin();
666 *It != Operands; ++It, ++TheArg) {
667 assert(It != ArgIndices.end() && "GEP not handled??");
670 std::string NewName = I->getName();
671 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
672 if (ConstantInt *CI = dyn_cast<ConstantInt>(Operands[i]))
673 NewName += "." + CI->getValue().toStringUnsigned(10);
676 TheArg->setName(NewName+".val");
678 DOUT << "*** Promoted agg argument '" << TheArg->getName()
679 << "' of function '" << F->getName() << "'\n";
681 // All of the uses must be load instructions. Replace them all with
682 // the argument specified by ArgNo.
683 while (!GEP->use_empty()) {
684 LoadInst *L = cast<LoadInst>(GEP->use_back());
685 L->replaceAllUsesWith(TheArg);
686 AA.replaceWithNewValue(L, TheArg);
687 L->eraseFromParent();
690 GEP->eraseFromParent();
694 // Increment I2 past all of the arguments added for this promoted pointer.
695 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
699 // Notify the alias analysis implementation that we inserted a new argument.
701 AA.copyValue(Constant::getNullValue(Type::Int32Ty), NF->arg_begin());
704 // Tell the alias analysis that the old function is about to disappear.
705 AA.replaceWithNewValue(F, NF);
707 // Now that the old function is dead, delete it.
708 F->eraseFromParent();