1 //===-- StructRetPromotion.cpp - Promote sret arguments -000000------------===//
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 // TODO : Describe this pass.
11 //===----------------------------------------------------------------------===//
13 #define DEBUG_TYPE "sretpromotion"
14 #include "llvm/Transforms/IPO.h"
15 #include "llvm/Constants.h"
16 #include "llvm/DerivedTypes.h"
17 #include "llvm/Module.h"
18 #include "llvm/CallGraphSCCPass.h"
19 #include "llvm/Instructions.h"
20 #include "llvm/Analysis/CallGraph.h"
21 #include "llvm/Support/CallSite.h"
22 #include "llvm/Support/CFG.h"
23 #include "llvm/Support/Debug.h"
24 #include "llvm/ADT/Statistic.h"
25 #include "llvm/ADT/SmallVector.h"
26 #include "llvm/ADT/Statistic.h"
27 #include "llvm/Support/Compiler.h"
30 STATISTIC(NumRejectedSRETUses , "Number of sret rejected due to unexpected uses");
31 STATISTIC(NumSRET , "Number of sret promoted");
33 /// SRETPromotion - This pass removes sret parameter and updates
34 /// function to use multiple return value.
36 struct VISIBILITY_HIDDEN SRETPromotion : public CallGraphSCCPass {
37 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
38 CallGraphSCCPass::getAnalysisUsage(AU);
41 virtual bool runOnSCC(const std::vector<CallGraphNode *> &SCC);
42 static char ID; // Pass identification, replacement for typeid
43 SRETPromotion() : CallGraphSCCPass((intptr_t)&ID) {}
46 bool PromoteReturn(CallGraphNode *CGN);
47 bool isSafeToUpdateAllCallers(Function *F);
48 Function *cloneFunctionBody(Function *F, const StructType *STy);
49 void updateCallSites(Function *F, Function *NF);
50 bool nestedStructType(const StructType *STy);
53 char SRETPromotion::ID = 0;
54 RegisterPass<SRETPromotion> X("sretpromotion",
55 "Promote sret arguments to multiple ret values");
58 Pass *llvm::createStructRetPromotionPass() {
59 return new SRETPromotion();
62 bool SRETPromotion::runOnSCC(const std::vector<CallGraphNode *> &SCC) {
65 for (unsigned i = 0, e = SCC.size(); i != e; ++i)
66 Changed |= PromoteReturn(SCC[i]);
71 /// PromoteReturn - This method promotes function that uses StructRet paramater
72 /// into a function that uses mulitple return value.
73 bool SRETPromotion::PromoteReturn(CallGraphNode *CGN) {
74 Function *F = CGN->getFunction();
76 if (!F || F->isDeclaration() || !F->hasInternalLinkage())
79 // Make sure that function returns struct.
80 if (F->arg_size() == 0 || !F->hasStructRetAttr() || F->doesNotReturn())
83 assert (F->getReturnType() == Type::VoidTy && "Invalid function return type");
84 Function::arg_iterator AI = F->arg_begin();
85 const llvm::PointerType *FArgType = dyn_cast<PointerType>(AI->getType());
86 assert (FArgType && "Invalid sret paramater type");
87 const llvm::StructType *STy =
88 dyn_cast<StructType>(FArgType->getElementType());
89 assert (STy && "Invalid sret parameter element type");
91 if (nestedStructType(STy))
94 // Check if it is ok to perform this promotion.
95 if (isSafeToUpdateAllCallers(F) == false) {
96 NumRejectedSRETUses++;
101 // [1] Replace use of sret parameter
102 AllocaInst *TheAlloca = new AllocaInst (STy, NULL, "mrv",
103 F->getEntryBlock().begin());
104 Value *NFirstArg = F->arg_begin();
105 NFirstArg->replaceAllUsesWith(TheAlloca);
107 // [2] Find and replace ret instructions
108 SmallVector<Value *,4> RetVals;
109 for (Function::iterator FI = F->begin(), FE = F->end(); FI != FE; ++FI)
110 for(BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ) {
113 if (isa<ReturnInst>(I)) {
115 for (unsigned idx = 0; idx < STy->getNumElements(); ++idx) {
116 SmallVector<Value*, 2> GEPIdx;
117 GEPIdx.push_back(ConstantInt::get(Type::Int32Ty, 0));
118 GEPIdx.push_back(ConstantInt::get(Type::Int32Ty, idx));
119 Value *NGEPI = GetElementPtrInst::Create(TheAlloca, GEPIdx.begin(),
122 Value *NV = new LoadInst(NGEPI, "mrv.ld", I);
123 RetVals.push_back(NV);
126 ReturnInst *NR = ReturnInst::Create(&RetVals[0], RetVals.size(), I);
127 I->replaceAllUsesWith(NR);
128 I->eraseFromParent();
132 // [3] Create the new function body and insert it into the module.
133 Function *NF = cloneFunctionBody(F, STy);
135 // [4] Update all call sites to use new function
136 updateCallSites(F, NF);
138 F->eraseFromParent();
139 getAnalysis<CallGraph>().changeFunction(F, NF);
143 // Check if it is ok to perform this promotion.
144 bool SRETPromotion::isSafeToUpdateAllCallers(Function *F) {
147 // No users. OK to modify signature.
150 for (Value::use_iterator FnUseI = F->use_begin(), FnUseE = F->use_end();
151 FnUseI != FnUseE; ++FnUseI) {
153 CallSite CS = CallSite::get(*FnUseI);
154 Instruction *Call = CS.getInstruction();
155 CallSite::arg_iterator AI = CS.arg_begin();
156 Value *FirstArg = *AI;
158 if (!isa<AllocaInst>(FirstArg))
161 // Check FirstArg's users.
162 for (Value::use_iterator ArgI = FirstArg->use_begin(),
163 ArgE = FirstArg->use_end(); ArgI != ArgE; ++ArgI) {
165 // If FirstArg user is a CallInst that does not correspond to current
166 // call site then this function F is not suitable for sret promotion.
167 if (CallInst *CI = dyn_cast<CallInst>(ArgI)) {
171 // If FirstArg user is a GEP whose all users are not LoadInst then
172 // this function F is not suitable for sret promotion.
173 else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(ArgI)) {
174 // TODO : Use dom info and insert PHINodes to collect get results
175 // from multiple call sites for this GEP.
176 if (GEP->getParent() != Call->getParent())
178 for (Value::use_iterator GEPI = GEP->use_begin(), GEPE = GEP->use_end();
179 GEPI != GEPE; ++GEPI)
180 if (!isa<LoadInst>(GEPI))
183 // Any other FirstArg users make this function unsuitable for sret
193 /// cloneFunctionBody - Create a new function based on F and
194 /// insert it into module. Remove first argument. Use STy as
195 /// the return type for new function.
196 Function *SRETPromotion::cloneFunctionBody(Function *F,
197 const StructType *STy) {
199 const FunctionType *FTy = F->getFunctionType();
200 std::vector<const Type*> Params;
202 // ParamAttrs - Keep track of the parameter attributes for the arguments.
203 SmallVector<ParamAttrsWithIndex, 8> ParamAttrsVec;
204 const PAListPtr &PAL = F->getParamAttrs();
206 // Add any return attributes.
207 if (ParameterAttributes attrs = PAL.getParamAttrs(0))
208 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
210 // Skip first argument.
211 Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
213 // 0th parameter attribute is reserved for return type.
214 // 1th parameter attribute is for first 1st sret argument.
215 unsigned ParamIndex = 2;
217 Params.push_back(I->getType());
218 if (ParameterAttributes Attrs = PAL.getParamAttrs(ParamIndex))
219 ParamAttrsVec.push_back(ParamAttrsWithIndex::get(ParamIndex - 1, Attrs));
224 FunctionType *NFTy = FunctionType::get(STy, Params, FTy->isVarArg());
225 Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
226 NF->setCallingConv(F->getCallingConv());
227 NF->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end()));
228 F->getParent()->getFunctionList().insert(F, NF);
229 NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
234 Function::arg_iterator NI = NF->arg_begin();
237 I->replaceAllUsesWith(NI);
246 /// updateCallSites - Update all sites that call F to use NF.
247 void SRETPromotion::updateCallSites(Function *F, Function *NF) {
249 SmallVector<Value*, 16> Args;
251 // ParamAttrs - Keep track of the parameter attributes for the arguments.
252 SmallVector<ParamAttrsWithIndex, 8> ArgAttrsVec;
254 for (Value::use_iterator FUI = F->use_begin(), FUE = F->use_end();
256 CallSite CS = CallSite::get(*FUI);
258 Instruction *Call = CS.getInstruction();
260 const PAListPtr &PAL = F->getParamAttrs();
261 // Add any return attributes.
262 if (ParameterAttributes attrs = PAL.getParamAttrs(0))
263 ArgAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
265 // Copy arguments, however skip first one.
266 CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
267 Value *FirstCArg = *AI;
269 // 0th parameter attribute is reserved for return type.
270 // 1th parameter attribute is for first 1st sret argument.
271 unsigned ParamIndex = 2;
274 if (ParameterAttributes Attrs = PAL.getParamAttrs(ParamIndex))
275 ArgAttrsVec.push_back(ParamAttrsWithIndex::get(ParamIndex - 1, Attrs));
281 PAListPtr NewPAL = PAListPtr::get(ArgAttrsVec.begin(), ArgAttrsVec.end());
283 // Build new call instruction.
285 if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
286 New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
287 Args.begin(), Args.end(), "", Call);
288 cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
289 cast<InvokeInst>(New)->setParamAttrs(NewPAL);
291 New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
292 cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
293 cast<CallInst>(New)->setParamAttrs(NewPAL);
294 if (cast<CallInst>(Call)->isTailCall())
295 cast<CallInst>(New)->setTailCall();
301 // Update all users of sret parameter to extract value using getresult.
302 for (Value::use_iterator UI = FirstCArg->use_begin(),
303 UE = FirstCArg->use_end(); UI != UE; ) {
305 CallInst *C2 = dyn_cast<CallInst>(U2);
306 if (C2 && (C2 == Call))
308 else if (GetElementPtrInst *UGEP = dyn_cast<GetElementPtrInst>(U2)) {
309 ConstantInt *Idx = dyn_cast<ConstantInt>(UGEP->getOperand(2));
310 assert (Idx && "Unexpected getelementptr index!");
311 Value *GR = new GetResultInst(New, Idx->getZExtValue(), "gr", UGEP);
312 for (Value::use_iterator GI = UGEP->use_begin(),
313 GE = UGEP->use_end(); GI != GE; ++GI) {
314 if (LoadInst *L = dyn_cast<LoadInst>(*GI)) {
315 L->replaceAllUsesWith(GR);
316 L->eraseFromParent();
319 UGEP->eraseFromParent();
321 else assert( 0 && "Unexpected sret parameter use");
323 Call->eraseFromParent();
327 /// nestedStructType - Return true if STy includes any
328 /// other aggregate types
329 bool SRETPromotion::nestedStructType(const StructType *STy) {
330 unsigned Num = STy->getNumElements();
331 for (unsigned i = 0; i < Num; i++) {
332 const Type *Ty = STy->getElementType(i);
333 if (!Ty->isFirstClassType() && Ty != Type::VoidTy)