+++ /dev/null
-//===-- StructRetPromotion.cpp - Promote sret arguments -------------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This pass finds functions that return a struct (using a pointer to the struct
-// as the first argument of the function, marked with the 'sret' attribute) and
-// replaces them with a new function that simply returns each of the elements of
-// that struct (using multiple return values).
-//
-// This pass works under a number of conditions:
-// 1. The returned struct must not contain other structs
-// 2. The returned struct must only be used to load values from
-// 3. The placeholder struct passed in is the result of an alloca
-//
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "sretpromotion"
-#include "llvm/Transforms/IPO.h"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Module.h"
-#include "llvm/CallGraphSCCPass.h"
-#include "llvm/Instructions.h"
-#include "llvm/Analysis/CallGraph.h"
-#include "llvm/Support/CallSite.h"
-#include "llvm/Support/CFG.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Support/raw_ostream.h"
-using namespace llvm;
-
-STATISTIC(NumRejectedSRETUses , "Number of sret rejected due to unexpected uses");
-STATISTIC(NumSRET , "Number of sret promoted");
-namespace {
- /// SRETPromotion - This pass removes sret parameter and updates
- /// function to use multiple return value.
- ///
- struct SRETPromotion : public CallGraphSCCPass {
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- CallGraphSCCPass::getAnalysisUsage(AU);
- }
-
- virtual bool runOnSCC(CallGraphSCC &SCC);
- static char ID; // Pass identification, replacement for typeid
- SRETPromotion() : CallGraphSCCPass(ID) {
- initializeSRETPromotionPass(*PassRegistry::getPassRegistry());
- }
-
- private:
- CallGraphNode *PromoteReturn(CallGraphNode *CGN);
- bool isSafeToUpdateAllCallers(Function *F);
- Function *cloneFunctionBody(Function *F, const StructType *STy);
- CallGraphNode *updateCallSites(Function *F, Function *NF);
- };
-}
-
-char SRETPromotion::ID = 0;
-INITIALIZE_PASS_BEGIN(SRETPromotion, "sretpromotion",
- "Promote sret arguments to multiple ret values", false, false)
-INITIALIZE_AG_DEPENDENCY(CallGraph)
-INITIALIZE_PASS_END(SRETPromotion, "sretpromotion",
- "Promote sret arguments to multiple ret values", false, false)
-
-Pass *llvm::createStructRetPromotionPass() {
- return new SRETPromotion();
-}
-
-bool SRETPromotion::runOnSCC(CallGraphSCC &SCC) {
- bool Changed = false;
-
- for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); I != E; ++I)
- if (CallGraphNode *NewNode = PromoteReturn(*I)) {
- SCC.ReplaceNode(*I, NewNode);
- Changed = true;
- }
-
- return Changed;
-}
-
-/// PromoteReturn - This method promotes function that uses StructRet paramater
-/// into a function that uses multiple return values.
-CallGraphNode *SRETPromotion::PromoteReturn(CallGraphNode *CGN) {
- Function *F = CGN->getFunction();
-
- if (!F || F->isDeclaration() || !F->hasLocalLinkage())
- return 0;
-
- // Make sure that function returns struct.
- if (F->arg_size() == 0 || !F->hasStructRetAttr() || F->doesNotReturn())
- return 0;
-
- DEBUG(dbgs() << "SretPromotion: Looking at sret function "
- << F->getName() << "\n");
-
- assert(F->getReturnType()->isVoidTy() && "Invalid function return type");
- Function::arg_iterator AI = F->arg_begin();
- const llvm::PointerType *FArgType = dyn_cast<PointerType>(AI->getType());
- assert(FArgType && "Invalid sret parameter type");
- const llvm::StructType *STy =
- dyn_cast<StructType>(FArgType->getElementType());
- assert(STy && "Invalid sret parameter element type");
-
- // Check if it is ok to perform this promotion.
- if (isSafeToUpdateAllCallers(F) == false) {
- DEBUG(dbgs() << "SretPromotion: Not all callers can be updated\n");
- ++NumRejectedSRETUses;
- return 0;
- }
-
- DEBUG(dbgs() << "SretPromotion: sret argument will be promoted\n");
- ++NumSRET;
- // [1] Replace use of sret parameter
- AllocaInst *TheAlloca = new AllocaInst(STy, NULL, "mrv",
- F->getEntryBlock().begin());
- Value *NFirstArg = F->arg_begin();
- NFirstArg->replaceAllUsesWith(TheAlloca);
-
- // [2] Find and replace ret instructions
- for (Function::iterator FI = F->begin(), FE = F->end(); FI != FE; ++FI)
- for(BasicBlock::iterator BI = FI->begin(), BE = FI->end(); BI != BE; ) {
- Instruction *I = BI;
- ++BI;
- if (isa<ReturnInst>(I)) {
- Value *NV = new LoadInst(TheAlloca, "mrv.ld", I);
- ReturnInst *NR = ReturnInst::Create(F->getContext(), NV, I);
- I->replaceAllUsesWith(NR);
- I->eraseFromParent();
- }
- }
-
- // [3] Create the new function body and insert it into the module.
- Function *NF = cloneFunctionBody(F, STy);
-
- // [4] Update all call sites to use new function
- CallGraphNode *NF_CFN = updateCallSites(F, NF);
-
- CallGraph &CG = getAnalysis<CallGraph>();
- NF_CFN->stealCalledFunctionsFrom(CG[F]);
-
- delete CG.removeFunctionFromModule(F);
- return NF_CFN;
-}
-
-// Check if it is ok to perform this promotion.
-bool SRETPromotion::isSafeToUpdateAllCallers(Function *F) {
-
- if (F->use_empty())
- // No users. OK to modify signature.
- return true;
-
- for (Value::use_iterator FnUseI = F->use_begin(), FnUseE = F->use_end();
- FnUseI != FnUseE; ++FnUseI) {
- // The function is passed in as an argument to (possibly) another function,
- // we can't change it!
- CallSite CS(*FnUseI);
- Instruction *Call = CS.getInstruction();
- // The function is used by something else than a call or invoke instruction,
- // we can't change it!
- if (!Call || !CS.isCallee(FnUseI))
- return false;
- CallSite::arg_iterator AI = CS.arg_begin();
- Value *FirstArg = *AI;
-
- if (!isa<AllocaInst>(FirstArg))
- return false;
-
- // Check FirstArg's users.
- for (Value::use_iterator ArgI = FirstArg->use_begin(),
- ArgE = FirstArg->use_end(); ArgI != ArgE; ++ArgI) {
- User *U = *ArgI;
- // If FirstArg user is a CallInst that does not correspond to current
- // call site then this function F is not suitable for sret promotion.
- if (CallInst *CI = dyn_cast<CallInst>(U)) {
- if (CI != Call)
- return false;
- }
- // If FirstArg user is a GEP whose all users are not LoadInst then
- // this function F is not suitable for sret promotion.
- else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
- // TODO : Use dom info and insert PHINodes to collect get results
- // from multiple call sites for this GEP.
- if (GEP->getParent() != Call->getParent())
- return false;
- for (Value::use_iterator GEPI = GEP->use_begin(), GEPE = GEP->use_end();
- GEPI != GEPE; ++GEPI)
- if (!isa<LoadInst>(*GEPI))
- return false;
- }
- // Any other FirstArg users make this function unsuitable for sret
- // promotion.
- else
- return false;
- }
- }
-
- return true;
-}
-
-/// cloneFunctionBody - Create a new function based on F and
-/// insert it into module. Remove first argument. Use STy as
-/// the return type for new function.
-Function *SRETPromotion::cloneFunctionBody(Function *F,
- const StructType *STy) {
-
- const FunctionType *FTy = F->getFunctionType();
- std::vector<const Type*> Params;
-
- // Attributes - Keep track of the parameter attributes for the arguments.
- SmallVector<AttributeWithIndex, 8> AttributesVec;
- const AttrListPtr &PAL = F->getAttributes();
-
- // Add any return attributes.
- if (Attributes attrs = PAL.getRetAttributes())
- AttributesVec.push_back(AttributeWithIndex::get(0, attrs));
-
- // Skip first argument.
- Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
- ++I;
- // 0th parameter attribute is reserved for return type.
- // 1th parameter attribute is for first 1st sret argument.
- unsigned ParamIndex = 2;
- while (I != E) {
- Params.push_back(I->getType());
- if (Attributes Attrs = PAL.getParamAttributes(ParamIndex))
- AttributesVec.push_back(AttributeWithIndex::get(ParamIndex - 1, Attrs));
- ++I;
- ++ParamIndex;
- }
-
- // Add any fn attributes.
- if (Attributes attrs = PAL.getFnAttributes())
- AttributesVec.push_back(AttributeWithIndex::get(~0, attrs));
-
-
- FunctionType *NFTy = FunctionType::get(STy, Params, FTy->isVarArg());
- Function *NF = Function::Create(NFTy, F->getLinkage());
- NF->takeName(F);
- NF->copyAttributesFrom(F);
- NF->setAttributes(AttrListPtr::get(AttributesVec.begin(), AttributesVec.end()));
- F->getParent()->getFunctionList().insert(F, NF);
- NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
-
- // Replace arguments
- I = F->arg_begin();
- E = F->arg_end();
- Function::arg_iterator NI = NF->arg_begin();
- ++I;
- while (I != E) {
- I->replaceAllUsesWith(NI);
- NI->takeName(I);
- ++I;
- ++NI;
- }
-
- return NF;
-}
-
-/// updateCallSites - Update all sites that call F to use NF.
-CallGraphNode *SRETPromotion::updateCallSites(Function *F, Function *NF) {
- CallGraph &CG = getAnalysis<CallGraph>();
- SmallVector<Value*, 16> Args;
-
- // Attributes - Keep track of the parameter attributes for the arguments.
- SmallVector<AttributeWithIndex, 8> ArgAttrsVec;
-
- // Get a new callgraph node for NF.
- CallGraphNode *NF_CGN = CG.getOrInsertFunction(NF);
-
- while (!F->use_empty()) {
- CallSite CS(*F->use_begin());
- Instruction *Call = CS.getInstruction();
-
- const AttrListPtr &PAL = F->getAttributes();
- // Add any return attributes.
- if (Attributes attrs = PAL.getRetAttributes())
- ArgAttrsVec.push_back(AttributeWithIndex::get(0, attrs));
-
- // Copy arguments, however skip first one.
- CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
- Value *FirstCArg = *AI;
- ++AI;
- // 0th parameter attribute is reserved for return type.
- // 1th parameter attribute is for first 1st sret argument.
- unsigned ParamIndex = 2;
- while (AI != AE) {
- Args.push_back(*AI);
- if (Attributes Attrs = PAL.getParamAttributes(ParamIndex))
- ArgAttrsVec.push_back(AttributeWithIndex::get(ParamIndex - 1, Attrs));
- ++ParamIndex;
- ++AI;
- }
-
- // Add any function attributes.
- if (Attributes attrs = PAL.getFnAttributes())
- ArgAttrsVec.push_back(AttributeWithIndex::get(~0, attrs));
-
- AttrListPtr NewPAL = AttrListPtr::get(ArgAttrsVec.begin(), ArgAttrsVec.end());
-
- // Build new call instruction.
- Instruction *New;
- if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
- New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
- Args.begin(), Args.end(), "", Call);
- cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
- cast<InvokeInst>(New)->setAttributes(NewPAL);
- } else {
- New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
- cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
- cast<CallInst>(New)->setAttributes(NewPAL);
- if (cast<CallInst>(Call)->isTailCall())
- cast<CallInst>(New)->setTailCall();
- }
- Args.clear();
- ArgAttrsVec.clear();
- New->takeName(Call);
-
- // Update the callgraph to know that the callsite has been transformed.
- CallGraphNode *CalleeNode = CG[Call->getParent()->getParent()];
- CalleeNode->removeCallEdgeFor(Call);
- CalleeNode->addCalledFunction(New, NF_CGN);
-
- // Update all users of sret parameter to extract value using extractvalue.
- for (Value::use_iterator UI = FirstCArg->use_begin(),
- UE = FirstCArg->use_end(); UI != UE; ) {
- User *U2 = *UI++;
- CallInst *C2 = dyn_cast<CallInst>(U2);
- if (C2 && (C2 == Call))
- continue;
-
- GetElementPtrInst *UGEP = cast<GetElementPtrInst>(U2);
- ConstantInt *Idx = cast<ConstantInt>(UGEP->getOperand(2));
- Value *GR = ExtractValueInst::Create(New, Idx->getZExtValue(),
- "evi", UGEP);
- while(!UGEP->use_empty()) {
- // isSafeToUpdateAllCallers has checked that all GEP uses are
- // LoadInsts
- LoadInst *L = cast<LoadInst>(*UGEP->use_begin());
- L->replaceAllUsesWith(GR);
- L->eraseFromParent();
- }
- UGEP->eraseFromParent();
- continue;
- }
- Call->eraseFromParent();
- }
-
- return NF_CGN;
-}
-
projects / oota-llvm.git / commitdiff