-//===-- StructRetPromotion.cpp - Promote sret arguments -000000------------===//
+//===-- StructRetPromotion.cpp - Promote sret arguments ------------------===//
//
// The LLVM Compiler Infrastructure
//
//
//===----------------------------------------------------------------------===//
//
-// TODO : Describe this pass.
+// 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"
void updateCallSites(Function *F, Function *NF);
bool nestedStructType(const StructType *STy);
};
-
- char SRETPromotion::ID = 0;
- RegisterPass<SRETPromotion> X("sretpromotion",
- "Promote sret arguments to multiple ret values");
}
+char SRETPromotion::ID = 0;
+static RegisterPass<SRETPromotion>
+X("sretpromotion", "Promote sret arguments to multiple ret values");
+
Pass *llvm::createStructRetPromotionPass() {
return new SRETPromotion();
}
if (F->arg_size() == 0 || !F->hasStructRetAttr() || F->doesNotReturn())
return false;
+ DOUT << "SretPromotion: Looking at sret function " << F->getNameStart() << "\n";
+
assert (F->getReturnType() == Type::VoidTy && "Invalid function return type");
Function::arg_iterator AI = F->arg_begin();
const llvm::PointerType *FArgType = dyn_cast<PointerType>(AI->getType());
- assert (FArgType && "Invalid sret paramater type");
+ assert (FArgType && "Invalid sret parameter type");
const llvm::StructType *STy =
dyn_cast<StructType>(FArgType->getElementType());
assert (STy && "Invalid sret parameter element type");
- if (nestedStructType(STy))
- return false;
-
// Check if it is ok to perform this promotion.
if (isSafeToUpdateAllCallers(F) == false) {
+ DOUT << "SretPromotion: Not all callers can be updated\n";
NumRejectedSRETUses++;
return false;
}
+ DOUT << "SretPromotion: sret argument will be promoted\n";
NumSRET++;
// [1] Replace use of sret parameter
AllocaInst *TheAlloca = new AllocaInst (STy, NULL, "mrv",
NFirstArg->replaceAllUsesWith(TheAlloca);
// [2] Find and replace ret instructions
- SmallVector<Value *,4> RetVals;
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)) {
- RetVals.clear();
- for (unsigned idx = 0; idx < STy->getNumElements(); ++idx) {
- SmallVector<Value*, 2> GEPIdx;
- GEPIdx.push_back(ConstantInt::get(Type::Int32Ty, 0));
- GEPIdx.push_back(ConstantInt::get(Type::Int32Ty, idx));
- Value *NGEPI = GetElementPtrInst::Create(TheAlloca, GEPIdx.begin(),
- GEPIdx.end(),
- "mrv.gep", I);
- Value *NV = new LoadInst(NGEPI, "mrv.ld", I);
- RetVals.push_back(NV);
- }
-
- ReturnInst *NR = ReturnInst::Create(&RetVals[0], RetVals.size(), I);
+ Value *NV = new LoadInst(TheAlloca, "mrv.ld", I);
+ ReturnInst *NR = ReturnInst::Create(NV, I);
I->replaceAllUsesWith(NR);
I->eraseFromParent();
}
return true;
}
- // Check if it is ok to perform this promotion.
+// Check if it is ok to perform this promotion.
bool SRETPromotion::isSafeToUpdateAllCallers(Function *F) {
if (F->use_empty())
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!
+ if (FnUseI.getOperandNo() != 0)
+ return false;
CallSite CS = CallSite::get(*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)
+ return false;
CallSite::arg_iterator AI = CS.arg_begin();
Value *FirstArg = *AI;
}
FunctionType *NFTy = FunctionType::get(STy, Params, FTy->isVarArg());
- Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
- NF->setCallingConv(F->getCallingConv());
+ Function *NF = Function::Create(NFTy, F->getLinkage());
+ NF->takeName(F);
+ NF->copyAttributesFrom(F);
NF->setParamAttrs(PAListPtr::get(ParamAttrsVec.begin(), ParamAttrsVec.end()));
F->getParent()->getFunctionList().insert(F, NF);
NF->getBasicBlockList().splice(NF->begin(), F->getBasicBlockList());
// ParamAttrs - Keep track of the parameter attributes for the arguments.
SmallVector<ParamAttrsWithIndex, 8> ArgAttrsVec;
- for (Value::use_iterator FUI = F->use_begin(), FUE = F->use_end();
- FUI != FUE;) {
- CallSite CS = CallSite::get(*FUI);
- ++FUI;
+ while (!F->use_empty()) {
+ CallSite CS = CallSite::get(*F->use_begin());
Instruction *Call = CS.getInstruction();
const PAListPtr &PAL = F->getParamAttrs();
ArgAttrsVec.clear();
New->takeName(Call);
- // Update all users of sret parameter to extract value using getresult.
+ // 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++;
else if (GetElementPtrInst *UGEP = dyn_cast<GetElementPtrInst>(U2)) {
ConstantInt *Idx = dyn_cast<ConstantInt>(UGEP->getOperand(2));
assert (Idx && "Unexpected getelementptr index!");
- Value *GR = new GetResultInst(New, Idx->getZExtValue(), "gr", UGEP);
- for (Value::use_iterator GI = UGEP->use_begin(),
- GE = UGEP->use_end(); GI != GE; ++GI) {
- if (LoadInst *L = dyn_cast<LoadInst>(*GI)) {
- L->replaceAllUsesWith(GR);
- L->eraseFromParent();
- }
+ 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();
}
unsigned Num = STy->getNumElements();
for (unsigned i = 0; i < Num; i++) {
const Type *Ty = STy->getElementType(i);
- if (!Ty->isFirstClassType() && Ty != Type::VoidTy)
+ if (!Ty->isSingleValueType() && Ty != Type::VoidTy)
return true;
}
return false;
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