-//===-- 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"
#include "llvm/Module.h"
#include "llvm/CallGraphSCCPass.h"
#include "llvm/Instructions.h"
-#include "llvm/ParamAttrsList.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/CFG.h"
bool isSafeToUpdateAllCallers(Function *F);
Function *cloneFunctionBody(Function *F, const StructType *STy);
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();
}
bool SRETPromotion::PromoteReturn(CallGraphNode *CGN) {
Function *F = CGN->getFunction();
- // Make sure that it is local to this module.
- if (!F || !F->hasInternalLinkage())
+ if (!F || F->isDeclaration() || !F->hasInternalLinkage())
return false;
// Make sure that function returns struct.
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");
// 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",
F->getEntryBlock().begin());
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 = new GetElementPtrInst(TheAlloca, GEPIdx.begin(), GEPIdx.end(),
- "mrv.gep", I);
- Value *NV = new LoadInst(NGEPI, "mrv.ld", I);
- RetVals.push_back(NV);
- }
-
- ReturnInst *NR = new ReturnInst(&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;
// 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>(ArgI)) {
+ // 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))
std::vector<const Type*> Params;
// ParamAttrs - Keep track of the parameter attributes for the arguments.
- ParamAttrsVector ParamAttrsVec;
- const ParamAttrsList *PAL = F->getParamAttrs();
+ SmallVector<ParamAttrsWithIndex, 8> ParamAttrsVec;
+ const PAListPtr &PAL = F->getParamAttrs();
// Add any return attributes.
- if (ParameterAttributes attrs = PAL ? PAL->getParamAttrs(0) : ParamAttr::None)
+ if (ParameterAttributes attrs = PAL.getParamAttrs(0))
ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
// Skip first argument.
Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
++I;
- unsigned ParamIndex = 1; // 0th parameter attribute is reserved for return type.
+ // 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 (ParameterAttributes attrs = PAL ? PAL->getParamAttrs(ParamIndex) :
- ParamAttr::None)
- ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Params.size(), attrs));
+ if (ParameterAttributes Attrs = PAL.getParamAttrs(ParamIndex))
+ ParamAttrsVec.push_back(ParamAttrsWithIndex::get(ParamIndex - 1, Attrs));
++I;
++ParamIndex;
}
FunctionType *NFTy = FunctionType::get(STy, Params, FTy->isVarArg());
- Function *NF = new Function(NFTy, F->getLinkage(), F->getName());
- NF->setCallingConv(F->getCallingConv());
- NF->setParamAttrs(ParamAttrsList::get(ParamAttrsVec));
+ 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());
SmallVector<Value*, 16> Args;
// ParamAttrs - Keep track of the parameter attributes for the arguments.
- ParamAttrsVector ParamAttrsVec;
+ 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 ParamAttrsList *PAL = F->getParamAttrs();
+ const PAListPtr &PAL = F->getParamAttrs();
// Add any return attributes.
- if (ParameterAttributes attrs = PAL ? PAL->getParamAttrs(0) : ParamAttr::None)
- ParamAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
+ if (ParameterAttributes attrs = PAL.getParamAttrs(0))
+ ArgAttrsVec.push_back(ParamAttrsWithIndex::get(0, attrs));
// Copy arguments, however skip first one.
CallSite::arg_iterator AI = CS.arg_begin(), AE = CS.arg_end();
Value *FirstCArg = *AI;
++AI;
- unsigned ParamIndex = 1; // 0th parameter attribute is reserved for return type.
+ // 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 (ParameterAttributes Attrs = PAL ? PAL->getParamAttrs(ParamIndex) :
- ParamAttr::None)
- ParamAttrsVec.push_back(ParamAttrsWithIndex::get(Args.size(), Attrs));
+ if (ParameterAttributes Attrs = PAL.getParamAttrs(ParamIndex))
+ ArgAttrsVec.push_back(ParamAttrsWithIndex::get(ParamIndex - 1, Attrs));
++ParamIndex;
++AI;
}
+
+ PAListPtr NewPAL = PAListPtr::get(ArgAttrsVec.begin(), ArgAttrsVec.end());
+
// Build new call instruction.
Instruction *New;
if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
- New = new InvokeInst(NF, II->getNormalDest(), II->getUnwindDest(),
- Args.begin(), Args.end(), "", Call);
+ New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
+ Args.begin(), Args.end(), "", Call);
cast<InvokeInst>(New)->setCallingConv(CS.getCallingConv());
- cast<InvokeInst>(New)->setParamAttrs(ParamAttrsList::get(ParamAttrsVec));
+ cast<InvokeInst>(New)->setParamAttrs(NewPAL);
} else {
- New = new CallInst(NF, Args.begin(), Args.end(), "", Call);
+ New = CallInst::Create(NF, Args.begin(), Args.end(), "", Call);
cast<CallInst>(New)->setCallingConv(CS.getCallingConv());
- cast<CallInst>(New)->setParamAttrs(ParamAttrsList::get(ParamAttrsVec));
+ cast<CallInst>(New)->setParamAttrs(NewPAL);
if (cast<CallInst>(Call)->isTailCall())
cast<CallInst>(New)->setTailCall();
}
Args.clear();
- ParamAttrsVec.clear();
+ 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++;
if (C2 && (C2 == Call))
continue;
else if (GetElementPtrInst *UGEP = dyn_cast<GetElementPtrInst>(U2)) {
- Value *GR = new GetResultInst(New, 5, "xxx", 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();
- }
+ ConstantInt *Idx = dyn_cast<ConstantInt>(UGEP->getOperand(2));
+ assert (Idx && "Unexpected getelementptr index!");
+ 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();
}
Call->eraseFromParent();
}
}
+
+/// nestedStructType - Return true if STy includes any
+/// other aggregate types
+bool SRETPromotion::nestedStructType(const StructType *STy) {
+ unsigned Num = STy->getNumElements();
+ for (unsigned i = 0; i < Num; i++) {
+ const Type *Ty = STy->getElementType(i);
+ if (!Ty->isSingleValueType() && Ty != Type::VoidTy)
+ return true;
+ }
+ return false;
+}
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