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 // 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!
24 // Note that this transformation could also be done for arguments that are only
25 // stored to (returning the value instead), but does not currently. This case
26 // would be best handled when and if LLVM begins supporting multiple return
27 // values from functions.
29 //===----------------------------------------------------------------------===//
31 #define DEBUG_TYPE "argpromotion"
32 #include "llvm/Transforms/IPO.h"
33 #include "llvm/Constants.h"
34 #include "llvm/DerivedTypes.h"
35 #include "llvm/Module.h"
36 #include "llvm/CallGraphSCCPass.h"
37 #include "llvm/Instructions.h"
38 #include "llvm/ParameterAttributes.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() : CallGraphSCCPass((intptr_t)&ID) {}
72 bool PromoteArguments(CallGraphNode *CGN);
73 bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const;
74 Function *DoPromotion(Function *F,
75 SmallPtrSet<Argument*, 8> &ArgsToPromote,
76 SmallPtrSet<Argument*, 8> &ByValArgsToTransform);
79 char ArgPromotion::ID = 0;
80 RegisterPass<ArgPromotion> X("argpromotion",
81 "Promote 'by reference' arguments to scalars");
84 Pass *llvm::createArgumentPromotionPass() {
85 return new ArgPromotion();
88 bool ArgPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
89 bool Changed = false, LocalChange;
91 do { // Iterate until we stop promoting from this SCC.
93 // Attempt to promote arguments from all functions in this SCC.
94 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
95 LocalChange |= PromoteArguments(SCC[i]);
96 Changed |= LocalChange; // Remember that we changed something.
97 } while (LocalChange);
102 /// PromoteArguments - This method checks the specified function to see if there
103 /// are any promotable arguments and if it is safe to promote the function (for
104 /// example, all callers are direct). If safe to promote some arguments, it
105 /// calls the DoPromotion method.
107 bool ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
108 Function *F = CGN->getFunction();
110 // Make sure that it is local to this module.
111 if (!F || !F->hasInternalLinkage()) return false;
113 // First check: see if there are any pointer arguments! If not, quick exit.
114 SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs;
116 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
117 I != E; ++I, ++ArgNo)
118 if (isa<PointerType>(I->getType()))
119 PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo));
120 if (PointerArgs.empty()) return false;
122 // Second check: make sure that all callers are direct callers. We can't
123 // transform functions that have indirect callers.
124 for (Value::use_iterator UI = F->use_begin(), E = F->use_end();
126 CallSite CS = CallSite::get(*UI);
127 if (!CS.getInstruction()) // "Taking the address" of the function
130 // Ensure that this call site is CALLING the function, not passing it as
132 if (UI.getOperandNo() != 0)
136 // Check to see which arguments are promotable. If an argument is promotable,
137 // add it to ArgsToPromote.
138 SmallPtrSet<Argument*, 8> ArgsToPromote;
139 SmallPtrSet<Argument*, 8> ByValArgsToTransform;
140 for (unsigned i = 0; i != PointerArgs.size(); ++i) {
141 bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, ParamAttr::ByVal);
143 // If this is a byval argument, and if the aggregate type is small, just
144 // pass the elements, which is always safe.
145 Argument *PtrArg = PointerArgs[i].first;
147 const Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
148 if (const StructType *STy = dyn_cast<StructType>(AgTy))
149 if (STy->getNumElements() <= 3) {
150 // If all the elements are first class types, we can promote it.
151 bool AllSimple = true;
152 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
153 if (!STy->getElementType(i)->isFirstClassType()) {
158 // Safe to transform, don't even bother trying to "promote" it.
159 // Passing the elements as a scalar will allow scalarrepl to hack on
160 // the new alloca we introduce.
162 ByValArgsToTransform.insert(PtrArg);
168 // Otherwise, see if we can promote the pointer to its value.
169 if (isSafeToPromoteArgument(PtrArg, isByVal))
170 ArgsToPromote.insert(PtrArg);
173 // No promotable pointer arguments.
174 if (ArgsToPromote.empty() && ByValArgsToTransform.empty()) return false;
176 Function *NewF = DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
178 // Update the call graph to know that the function has been transformed.
179 getAnalysis<CallGraph>().changeFunction(F, NewF);
183 /// IsAlwaysValidPointer - Return true if the specified pointer is always legal
185 static bool IsAlwaysValidPointer(Value *V) {
186 if (isa<AllocaInst>(V) || isa<GlobalVariable>(V)) return true;
187 if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(V))
188 return IsAlwaysValidPointer(GEP->getOperand(0));
189 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V))
190 if (CE->getOpcode() == Instruction::GetElementPtr)
191 return IsAlwaysValidPointer(CE->getOperand(0));
196 /// AllCalleesPassInValidPointerForArgument - Return true if we can prove that
197 /// all callees pass in a valid pointer for the specified function argument.
198 static bool AllCalleesPassInValidPointerForArgument(Argument *Arg) {
199 Function *Callee = Arg->getParent();
201 unsigned ArgNo = std::distance(Callee->arg_begin(),
202 Function::arg_iterator(Arg));
204 // Look at all call sites of the function. At this pointer we know we only
205 // have direct callees.
206 for (Value::use_iterator UI = Callee->use_begin(), E = Callee->use_end();
208 CallSite CS = CallSite::get(*UI);
209 assert(CS.getInstruction() && "Should only have direct calls!");
211 if (!IsAlwaysValidPointer(CS.getArgument(ArgNo)))
218 /// isSafeToPromoteArgument - As you might guess from the name of this method,
219 /// it checks to see if it is both safe and useful to promote the argument.
220 /// This method limits promotion of aggregates to only promote up to three
221 /// elements of the aggregate in order to avoid exploding the number of
222 /// arguments passed in.
223 bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg, bool isByVal) const {
224 // We can only promote this argument if all of the uses are loads, or are GEP
225 // instructions (with constant indices) that are subsequently loaded.
227 // We can also only promote the load if we can guarantee that it will happen.
228 // Promoting a load causes the load to be unconditionally executed in the
229 // caller, so we can't turn a conditional load into an unconditional load in
231 bool SafeToUnconditionallyLoad = false;
232 if (isByVal) // ByVal arguments are always safe to load from.
233 SafeToUnconditionallyLoad = true;
235 BasicBlock *EntryBlock = Arg->getParent()->begin();
236 SmallVector<LoadInst*, 16> Loads;
237 std::vector<SmallVector<ConstantInt*, 8> > GEPIndices;
238 for (Value::use_iterator UI = Arg->use_begin(), E = Arg->use_end();
240 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
241 if (LI->isVolatile()) return false; // Don't hack volatile loads
244 // If this load occurs in the entry block, then the pointer is
245 // unconditionally loaded.
246 SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock;
247 } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(*UI)) {
248 if (GEP->use_empty()) {
249 // Dead GEP's cause trouble later. Just remove them if we run into
251 getAnalysis<AliasAnalysis>().deleteValue(GEP);
252 GEP->eraseFromParent();
253 return isSafeToPromoteArgument(Arg, isByVal);
255 // Ensure that all of the indices are constants.
256 SmallVector<ConstantInt*, 8> Operands;
257 for (unsigned i = 1, e = GEP->getNumOperands(); i != e; ++i)
258 if (ConstantInt *C = dyn_cast<ConstantInt>(GEP->getOperand(i)))
259 Operands.push_back(C);
261 return false; // Not a constant operand GEP!
263 // Ensure that the only users of the GEP are load instructions.
264 for (Value::use_iterator UI = GEP->use_begin(), E = GEP->use_end();
266 if (LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
267 if (LI->isVolatile()) return false; // Don't hack volatile loads
270 // If this load occurs in the entry block, then the pointer is
271 // unconditionally loaded.
272 SafeToUnconditionallyLoad |= LI->getParent() == EntryBlock;
277 // See if there is already a GEP with these indices. If not, check to
278 // make sure that we aren't promoting too many elements. If so, nothing
280 if (std::find(GEPIndices.begin(), GEPIndices.end(), Operands) ==
282 if (GEPIndices.size() == 3) {
283 DOUT << "argpromotion disable promoting argument '"
284 << Arg->getName() << "' because it would require adding more "
285 << "than 3 arguments to the function.\n";
286 // We limit aggregate promotion to only promoting up to three elements
290 GEPIndices.push_back(Operands);
293 return false; // Not a load or a GEP.
296 if (Loads.empty()) return true; // No users, this is a dead argument.
298 // If we decide that we want to promote this argument, the value is going to
299 // be unconditionally loaded in all callees. This is only safe to do if the
300 // pointer was going to be unconditionally loaded anyway (i.e. there is a load
301 // of the pointer in the entry block of the function) or if we can prove that
302 // all pointers passed in are always to legal locations (for example, no null
303 // pointers are passed in, no pointers to free'd memory, etc).
304 if (!SafeToUnconditionallyLoad &&
305 !AllCalleesPassInValidPointerForArgument(Arg))
306 return false; // Cannot prove that this is safe!!
308 // Okay, now we know that the argument is only used by load instructions and
309 // it is safe to unconditionally load the pointer. Use alias analysis to
310 // check to see if the pointer is guaranteed to not be modified from entry of
311 // the function to each of the load instructions.
313 // Because there could be several/many load instructions, remember which
314 // blocks we know to be transparent to the load.
315 SmallPtrSet<BasicBlock*, 16> TranspBlocks;
317 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
318 TargetData &TD = getAnalysis<TargetData>();
320 for (unsigned i = 0, e = Loads.size(); i != e; ++i) {
321 // Check to see if the load is invalidated from the start of the block to
323 LoadInst *Load = Loads[i];
324 BasicBlock *BB = Load->getParent();
326 const PointerType *LoadTy =
327 cast<PointerType>(Load->getOperand(0)->getType());
328 unsigned LoadSize = (unsigned)TD.getTypeStoreSize(LoadTy->getElementType());
330 if (AA.canInstructionRangeModify(BB->front(), *Load, Arg, LoadSize))
331 return false; // Pointer is invalidated!
333 // Now check every path from the entry block to the load for transparency.
334 // To do this, we perform a depth first search on the inverse CFG from the
336 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
337 for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
338 I = idf_ext_begin(*PI, TranspBlocks),
339 E = idf_ext_end(*PI, TranspBlocks); I != E; ++I)
340 if (AA.canBasicBlockModify(**I, Arg, LoadSize))
344 // If the path from the entry of the function to each load is free of
345 // instructions that potentially invalidate the load, we can make the
351 /// GEPIdxComparator - Provide a strong ordering for GEP indices. All Value*
352 /// elements are instances of ConstantInt.
354 struct GEPIdxComparator {
355 bool operator()(const std::vector<Value*> &LHS,
356 const std::vector<Value*> &RHS) const {
358 for (; idx < LHS.size() && idx < RHS.size(); ++idx) {
359 if (LHS[idx] != RHS[idx]) {
360 return cast<ConstantInt>(LHS[idx])->getZExtValue() <
361 cast<ConstantInt>(RHS[idx])->getZExtValue();
365 // Return less than if we ran out of stuff in LHS and we didn't run out of
367 return idx == LHS.size() && idx != RHS.size();
373 /// DoPromotion - This method actually performs the promotion of the specified
374 /// arguments, and returns the new function. At this point, we know that it's
376 Function *ArgPromotion::DoPromotion(Function *F,
377 SmallPtrSet<Argument*, 8> &ArgsToPromote,
378 SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
380 // Start by computing a new prototype for the function, which is the same as
381 // the old function, but has modified arguments.
382 const FunctionType *FTy = F->getFunctionType();
383 std::vector<const Type*> Params;
385 typedef std::set<std::vector<Value*>, GEPIdxComparator> ScalarizeTable;
387 // ScalarizedElements - If we are promoting a pointer that has elements
388 // accessed out of it, keep track of which elements are accessed so that we
389 // can add one argument for each.
391 // Arguments that are directly loaded will have a zero element value here, to
392 // handle cases where there are both a direct load and GEP accesses.
394 std::map<Argument*, ScalarizeTable> ScalarizedElements;
396 // OriginalLoads - Keep track of a representative load instruction from the
397 // original function so that we can tell the alias analysis implementation
398 // what the new GEP/Load instructions we are inserting look like.
399 std::map<std::vector<Value*>, LoadInst*> OriginalLoads;
401 // ParamAttrs - Keep track of the parameter attributes for the arguments
402 // that we are *not* promoting. For the ones that we do promote, the parameter
403 // attributes are lost
404 ParamAttrsVector ParamAttrsVec;
405 const ParamAttrsList *PAL = F->getParamAttrs();
407 // Add any return attributes.
408 if (unsigned attrs = PAL ? PAL->getParamAttrs(0) : 0)
409 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
411 unsigned ArgIndex = 1;
412 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
414 if (ByValArgsToTransform.count(I)) {
415 // Just add all the struct element types.
416 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
417 const StructType *STy = cast<StructType>(AgTy);
418 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
419 Params.push_back(STy->getElementType(i));
420 ++NumByValArgsPromoted;
421 } else if (!ArgsToPromote.count(I)) {
422 Params.push_back(I->getType());
423 if (unsigned attrs = PAL ? PAL->getParamAttrs(ArgIndex) : 0)
424 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), attrs));
425 } else if (I->use_empty()) {
428 // Okay, this is being promoted. Check to see if there are any GEP uses
430 ScalarizeTable &ArgIndices = ScalarizedElements[I];
431 for (Value::use_iterator UI = I->use_begin(), E = I->use_end(); UI != E;
433 Instruction *User = cast<Instruction>(*UI);
434 assert(isa<LoadInst>(User) || isa<GetElementPtrInst>(User));
435 std::vector<Value*> Indices(User->op_begin()+1, User->op_end());
436 ArgIndices.insert(Indices);
438 if (LoadInst *L = dyn_cast<LoadInst>(User))
441 OrigLoad = cast<LoadInst>(User->use_back());
442 OriginalLoads[Indices] = OrigLoad;
445 // Add a parameter to the function for each element passed in.
446 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
447 E = ArgIndices.end(); SI != E; ++SI)
448 Params.push_back(GetElementPtrInst::getIndexedType(I->getType(),
452 if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
453 ++NumArgumentsPromoted;
455 ++NumAggregatesPromoted;
459 const Type *RetTy = FTy->getReturnType();
461 // Work around LLVM bug PR56: the CWriter cannot emit varargs functions which
462 // have zero fixed arguments.
463 bool ExtraArgHack = false;
464 if (Params.empty() && FTy->isVarArg()) {
466 Params.push_back(Type::Int32Ty);
469 // Construct the new function type using the new arguments.
470 FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
472 // Create the new function body and insert it into the module...
473 Function *NF = new Function(NFTy, F->getLinkage(), F->getName());
474 NF->setCallingConv(F->getCallingConv());
476 // Recompute the parameter attributes list based on the new arguments for
478 NF->setParamAttrs(ParamAttrsList::get(ParamAttrsVec));
479 ParamAttrsVec.clear(); PAL = 0;
481 if (F->hasCollector())
482 NF->setCollector(F->getCollector());
483 F->getParent()->getFunctionList().insert(F, NF);
485 // Get the alias analysis information that we need to update to reflect our
487 AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
489 // Loop over all of the callers of the function, transforming the call sites
490 // to pass in the loaded pointers.
492 SmallVector<Value*, 16> Args;
493 while (!F->use_empty()) {
494 CallSite CS = CallSite::get(F->use_back());
495 Instruction *Call = CS.getInstruction();
496 PAL = CS.getParamAttrs();
498 // Add any return attributes.
499 if (unsigned attrs = PAL ? PAL->getParamAttrs(0) : 0)
500 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
502 // Loop over the operands, inserting GEP and loads in the caller as
504 CallSite::arg_iterator AI = CS.arg_begin();
506 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
507 I != E; ++I, ++AI, ++ArgIndex)
508 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
509 Args.push_back(*AI); // Unmodified argument
511 if (unsigned Attrs = PAL ? PAL->getParamAttrs(ArgIndex) : 0)
512 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
514 } else if (ByValArgsToTransform.count(I)) {
515 // Emit a GEP and load for each element of the struct.
516 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
517 const StructType *STy = cast<StructType>(AgTy);
518 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
519 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
520 Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
521 Value *Idx = new GetElementPtrInst(*AI, Idxs, Idxs+2,
522 (*AI)->getName()+"."+utostr(i),
524 // TODO: Tell AA about the new values?
525 Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
527 } else if (!I->use_empty()) {
528 // Non-dead argument: insert GEPs and loads as appropriate.
529 ScalarizeTable &ArgIndices = ScalarizedElements[I];
530 for (ScalarizeTable::iterator SI = ArgIndices.begin(),
531 E = ArgIndices.end(); SI != E; ++SI) {
533 LoadInst *OrigLoad = OriginalLoads[*SI];
535 V = new GetElementPtrInst(V, SI->begin(), SI->end(),
536 V->getName()+".idx", Call);
537 AA.copyValue(OrigLoad->getOperand(0), V);
539 Args.push_back(new LoadInst(V, V->getName()+".val", Call));
540 AA.copyValue(OrigLoad, Args.back());
545 Args.push_back(Constant::getNullValue(Type::Int32Ty));
547 // Push any varargs arguments on the list
548 for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
550 if (unsigned Attrs = PAL ? PAL->getParamAttrs(ArgIndex) : 0)
551 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
555 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
556 New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
557 Args.begin(), Args.end(), "", Call);
558 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
559 cast<InvokeInst>(New)->setParamAttrs(ParamAttrsList::get(ParamAttrsVec));
561 New = new CallInst(NF, Args.begin(), Args.end(), "", Call);
562 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
563 cast<CallInst>(New)->setParamAttrs(ParamAttrsList::get(ParamAttrsVec));
564 if (cast<CallInst>(Call)->isTailCall())
565 cast<CallInst>(New)->setTailCall();
568 ParamAttrsVec.clear();
570 // Update the alias analysis implementation to know that we are replacing
571 // the old call with a new one.
572 AA.replaceWithNewValue(Call, New);
574 if (!Call->use_empty()) {
575 Call->replaceAllUsesWith(New);
579 // Finally, remove the old call from the program, reducing the use-count of
581 Call->eraseFromParent();
584 // Since we have now created the new function, splice the body of the old
585 // function right into the new function, leaving the old rotting hulk of the
587 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
589 // Loop over the argument list, transfering uses of the old arguments over to
590 // the new arguments, also transfering over the names as well.
592 for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(),
593 I2 = NF->arg_begin(); I != E; ++I) {
594 if (!ArgsToPromote.count(I) && !ByValArgsToTransform.count(I)) {
595 // If this is an unmodified argument, move the name and users over to the
597 I->replaceAllUsesWith(I2);
599 AA.replaceWithNewValue(I, I2);
604 if (ByValArgsToTransform.count(I)) {
605 // In the callee, we create an alloca, and store each of the new incoming
606 // arguments into the alloca.
607 Instruction *InsertPt = NF->begin()->begin();
609 // Just add all the struct element types.
610 const Type *AgTy = cast<PointerType>(I->getType())->getElementType();
611 Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
612 const StructType *STy = cast<StructType>(AgTy);
613 Value *Idxs[2] = { ConstantInt::get(Type::Int32Ty, 0), 0 };
615 for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
616 Idxs[1] = ConstantInt::get(Type::Int32Ty, i);
617 Value *Idx = new GetElementPtrInst(TheAlloca, Idxs, Idxs+2,
618 TheAlloca->getName()+"."+utostr(i),
620 I2->setName(I->getName()+"."+utostr(i));
621 new StoreInst(I2++, Idx, InsertPt);
624 // Anything that used the arg should now use the alloca.
625 I->replaceAllUsesWith(TheAlloca);
626 TheAlloca->takeName(I);
627 AA.replaceWithNewValue(I, TheAlloca);
631 if (I->use_empty()) {
636 // Otherwise, if we promoted this argument, then all users are load
637 // instructions, and all loads should be using the new argument that we
639 ScalarizeTable &ArgIndices = ScalarizedElements[I];
641 while (!I->use_empty()) {
642 if (LoadInst *LI = dyn_cast<LoadInst>(I->use_back())) {
643 assert(ArgIndices.begin()->empty() &&
644 "Load element should sort to front!");
645 I2->setName(I->getName()+".val");
646 LI->replaceAllUsesWith(I2);
647 AA.replaceWithNewValue(LI, I2);
648 LI->eraseFromParent();
649 DOUT << "*** Promoted load of argument '" << I->getName()
650 << "' in function '" << F->getName() << "'\n";
652 GetElementPtrInst *GEP = cast<GetElementPtrInst>(I->use_back());
653 std::vector<Value*> Operands(GEP->op_begin()+1, GEP->op_end());
655 Function::arg_iterator TheArg = I2;
656 for (ScalarizeTable::iterator It = ArgIndices.begin();
657 *It != Operands; ++It, ++TheArg) {
658 assert(It != ArgIndices.end() && "GEP not handled??");
661 std::string NewName = I->getName();
662 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
663 if (ConstantInt *CI = dyn_cast<ConstantInt>(Operands[i]))
664 NewName += "." + CI->getValue().toStringUnsigned(10);
667 TheArg->setName(NewName+".val");
669 DOUT << "*** Promoted agg argument '" << TheArg->getName()
670 << "' of function '" << F->getName() << "'\n";
672 // All of the uses must be load instructions. Replace them all with
673 // the argument specified by ArgNo.
674 while (!GEP->use_empty()) {
675 LoadInst *L = cast<LoadInst>(GEP->use_back());
676 L->replaceAllUsesWith(TheArg);
677 AA.replaceWithNewValue(L, TheArg);
678 L->eraseFromParent();
681 GEP->eraseFromParent();
685 // Increment I2 past all of the arguments added for this promoted pointer.
686 for (unsigned i = 0, e = ArgIndices.size(); i != e; ++i)
690 // Notify the alias analysis implementation that we inserted a new argument.
692 AA.copyValue(Constant::getNullValue(Type::Int32Ty), NF->arg_begin());
695 // Tell the alias analysis that the old function is about to disappear.
696 AA.replaceWithNewValue(F, NF);
698 // Now that the old function is dead, delete it.
699 F->eraseFromParent();