//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "argpromotion"
#include "llvm/Transforms/IPO.h"
#include "llvm/ADT/DepthFirstIterator.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/CallGraphSCCPass.h"
+#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DebugInfo.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/LLVMContext.h"
#include <set>
using namespace llvm;
+#define DEBUG_TYPE "argpromotion"
+
STATISTIC(NumArgumentsPromoted , "Number of pointer arguments promoted");
STATISTIC(NumAggregatesPromoted, "Number of aggregate arguments promoted");
STATISTIC(NumByValArgsPromoted , "Number of byval arguments promoted");
typedef std::vector<uint64_t> IndicesVector;
private:
+ bool isDenselyPacked(Type *type, const DataLayout &DL);
+ bool canPaddingBeAccessed(Argument *Arg);
CallGraphNode *PromoteArguments(CallGraphNode *CGN);
bool isSafeToPromoteArgument(Argument *Arg, bool isByVal) const;
CallGraphNode *DoPromotion(Function *F,
- SmallPtrSet<Argument*, 8> &ArgsToPromote,
- SmallPtrSet<Argument*, 8> &ByValArgsToTransform);
+ SmallPtrSetImpl<Argument*> &ArgsToPromote,
+ SmallPtrSetImpl<Argument*> &ByValArgsToTransform);
+
+ using llvm::Pass::doInitialization;
+ bool doInitialization(CallGraph &CG) override;
/// The maximum number of elements to expand, or 0 for unlimited.
unsigned maxElements;
+ DenseMap<const Function *, DISubprogram *> FunctionDIs;
};
}
return Changed;
}
+/// \brief Checks if a type could have padding bytes.
+bool ArgPromotion::isDenselyPacked(Type *type, const DataLayout &DL) {
+
+ // There is no size information, so be conservative.
+ if (!type->isSized())
+ return false;
+
+ // If the alloc size is not equal to the storage size, then there are padding
+ // bytes. For x86_fp80 on x86-64, size: 80 alloc size: 128.
+ if (DL.getTypeSizeInBits(type) != DL.getTypeAllocSizeInBits(type))
+ return false;
+
+ if (!isa<CompositeType>(type))
+ return true;
+
+ // For homogenous sequential types, check for padding within members.
+ if (SequentialType *seqTy = dyn_cast<SequentialType>(type))
+ return isa<PointerType>(seqTy) ||
+ isDenselyPacked(seqTy->getElementType(), DL);
+
+ // Check for padding within and between elements of a struct.
+ StructType *StructTy = cast<StructType>(type);
+ const StructLayout *Layout = DL.getStructLayout(StructTy);
+ uint64_t StartPos = 0;
+ for (unsigned i = 0, E = StructTy->getNumElements(); i < E; ++i) {
+ Type *ElTy = StructTy->getElementType(i);
+ if (!isDenselyPacked(ElTy, DL))
+ return false;
+ if (StartPos != Layout->getElementOffsetInBits(i))
+ return false;
+ StartPos += DL.getTypeAllocSizeInBits(ElTy);
+ }
+
+ return true;
+}
+
+/// \brief Checks if the padding bytes of an argument could be accessed.
+bool ArgPromotion::canPaddingBeAccessed(Argument *arg) {
+
+ assert(arg->hasByValAttr());
+
+ // Track all the pointers to the argument to make sure they are not captured.
+ SmallPtrSet<Value *, 16> PtrValues;
+ PtrValues.insert(arg);
+
+ // Track all of the stores.
+ SmallVector<StoreInst *, 16> Stores;
+
+ // Scan through the uses recursively to make sure the pointer is always used
+ // sanely.
+ SmallVector<Value *, 16> WorkList;
+ WorkList.insert(WorkList.end(), arg->user_begin(), arg->user_end());
+ while (!WorkList.empty()) {
+ Value *V = WorkList.back();
+ WorkList.pop_back();
+ if (isa<GetElementPtrInst>(V) || isa<PHINode>(V)) {
+ if (PtrValues.insert(V).second)
+ WorkList.insert(WorkList.end(), V->user_begin(), V->user_end());
+ } else if (StoreInst *Store = dyn_cast<StoreInst>(V)) {
+ Stores.push_back(Store);
+ } else if (!isa<LoadInst>(V)) {
+ return true;
+ }
+ }
+
+// Check to make sure the pointers aren't captured
+ for (StoreInst *Store : Stores)
+ if (PtrValues.count(Store->getValueOperand()))
+ return true;
+
+ return false;
+}
+
/// PromoteArguments - This method checks the specified function to see if there
/// are any promotable arguments and if it is safe to promote the function (for
/// example, all callers are direct). If safe to promote some arguments, it
Function *F = CGN->getFunction();
// Make sure that it is local to this module.
- if (!F || !F->hasLocalLinkage()) return 0;
+ if (!F || !F->hasLocalLinkage()) return nullptr;
+
+ // Don't promote arguments for variadic functions. Adding, removing, or
+ // changing non-pack parameters can change the classification of pack
+ // parameters. Frontends encode that classification at the call site in the
+ // IR, while in the callee the classification is determined dynamically based
+ // on the number of registers consumed so far.
+ if (F->isVarArg()) return nullptr;
// First check: see if there are any pointer arguments! If not, quick exit.
SmallVector<Argument*, 16> PointerArgs;
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E; ++I)
if (I->getType()->isPointerTy())
PointerArgs.push_back(I);
- if (PointerArgs.empty()) return 0;
+ if (PointerArgs.empty()) return nullptr;
// Second check: make sure that all callers are direct callers. We can't
// transform functions that have indirect callers. Also see if the function
for (Use &U : F->uses()) {
CallSite CS(U.getUser());
// Must be a direct call.
- if (CS.getInstruction() == 0 || !CS.isCallee(&U)) return 0;
+ if (CS.getInstruction() == nullptr || !CS.isCallee(&U)) return nullptr;
if (CS.getInstruction()->getParent()->getParent() == F)
isSelfRecursive = true;
}
+ const DataLayout &DL = F->getParent()->getDataLayout();
+
// Check to see which arguments are promotable. If an argument is promotable,
// add it to ArgsToPromote.
SmallPtrSet<Argument*, 8> ArgsToPromote;
Argument *PtrArg = PointerArgs[i];
Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();
+ // Replace sret attribute with noalias. This reduces register pressure by
+ // avoiding a register copy.
+ if (PtrArg->hasStructRetAttr()) {
+ unsigned ArgNo = PtrArg->getArgNo();
+ F->setAttributes(
+ F->getAttributes()
+ .removeAttribute(F->getContext(), ArgNo + 1, Attribute::StructRet)
+ .addAttribute(F->getContext(), ArgNo + 1, Attribute::NoAlias));
+ for (Use &U : F->uses()) {
+ CallSite CS(U.getUser());
+ CS.setAttributes(
+ CS.getAttributes()
+ .removeAttribute(F->getContext(), ArgNo + 1,
+ Attribute::StructRet)
+ .addAttribute(F->getContext(), ArgNo + 1, Attribute::NoAlias));
+ }
+ }
+
// If this is a byval argument, and if the aggregate type is small, just
- // pass the elements, which is always safe. This does not apply to
- // inalloca.
- if (PtrArg->hasByValAttr()) {
+ // pass the elements, which is always safe, if the passed value is densely
+ // packed or if we can prove the padding bytes are never accessed. This does
+ // not apply to inalloca.
+ bool isSafeToPromote =
+ PtrArg->hasByValAttr() &&
+ (isDenselyPacked(AgTy, DL) || !canPaddingBeAccessed(PtrArg));
+ if (isSafeToPromote) {
if (StructType *STy = dyn_cast<StructType>(AgTy)) {
if (maxElements > 0 && STy->getNumElements() > maxElements) {
DEBUG(dbgs() << "argpromotion disable promoting argument '"
// No promotable pointer arguments.
if (ArgsToPromote.empty() && ByValArgsToTransform.empty())
- return 0;
+ return nullptr;
return DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
}
/// all callees pass in a valid pointer for the specified function argument.
static bool AllCallersPassInValidPointerForArgument(Argument *Arg) {
Function *Callee = Arg->getParent();
+ const DataLayout &DL = Callee->getParent()->getDataLayout();
unsigned ArgNo = Arg->getArgNo();
CallSite CS(U);
assert(CS && "Should only have direct calls!");
- if (!CS.getArgument(ArgNo)->isDereferenceablePointer())
+ if (!isDereferenceablePointer(CS.getArgument(ArgNo), DL))
return false;
}
return true;
// of elements of the aggregate.
return false;
}
- ToPromote.insert(Operands);
+ ToPromote.insert(std::move(Operands));
}
}
LoadInst *Load = Loads[i];
BasicBlock *BB = Load->getParent();
- AliasAnalysis::Location Loc = AA.getLocation(Load);
- if (AA.canInstructionRangeModify(BB->front(), *Load, Loc))
+ AliasAnalysis::Location Loc = MemoryLocation::get(Load);
+ if (AA.canInstructionRangeModRef(BB->front(), *Load, Loc,
+ AliasAnalysis::Mod))
return false; // Pointer is invalidated!
// Now check every path from the entry block to the load for transparency.
// To do this, we perform a depth first search on the inverse CFG from the
// loading block.
- for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
- BasicBlock *P = *PI;
- for (idf_ext_iterator<BasicBlock*, SmallPtrSet<BasicBlock*, 16> >
- I = idf_ext_begin(P, TranspBlocks),
- E = idf_ext_end(P, TranspBlocks); I != E; ++I)
- if (AA.canBasicBlockModify(**I, Loc))
+ for (BasicBlock *P : predecessors(BB)) {
+ for (BasicBlock *TranspBB : inverse_depth_first_ext(P, TranspBlocks))
+ if (AA.canBasicBlockModify(*TranspBB, Loc))
return false;
}
}
/// arguments, and returns the new function. At this point, we know that it's
/// safe to do so.
CallGraphNode *ArgPromotion::DoPromotion(Function *F,
- SmallPtrSet<Argument*, 8> &ArgsToPromote,
- SmallPtrSet<Argument*, 8> &ByValArgsToTransform) {
+ SmallPtrSetImpl<Argument*> &ArgsToPromote,
+ SmallPtrSetImpl<Argument*> &ByValArgsToTransform) {
// Start by computing a new prototype for the function, which is the same as
// the old function, but has modified arguments.
FunctionType *FTy = F->getFunctionType();
std::vector<Type*> Params;
- typedef std::set<IndicesVector> ScalarizeTable;
+ typedef std::set<std::pair<Type *, IndicesVector>> ScalarizeTable;
// ScalarizedElements - If we are promoting a pointer that has elements
// accessed out of it, keep track of which elements are accessed so that we
// Simple byval argument? Just add all the struct element types.
Type *AgTy = cast<PointerType>(I->getType())->getElementType();
StructType *STy = cast<StructType>(AgTy);
- for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
- Params.push_back(STy->getElementType(i));
+ Params.insert(Params.end(), STy->element_begin(), STy->element_end());
++NumByValArgsPromoted;
} else if (!ArgsToPromote.count(I)) {
// Unchanged argument
ScalarizeTable &ArgIndices = ScalarizedElements[I];
for (User *U : I->users()) {
Instruction *UI = cast<Instruction>(U);
- assert(isa<LoadInst>(UI) || isa<GetElementPtrInst>(UI));
+ Type *SrcTy;
+ if (LoadInst *L = dyn_cast<LoadInst>(UI))
+ SrcTy = L->getType();
+ else
+ SrcTy = cast<GetElementPtrInst>(UI)->getSourceElementType();
IndicesVector Indices;
Indices.reserve(UI->getNumOperands() - 1);
// Since loads will only have a single operand, and GEPs only a single
// GEPs with a single 0 index can be merged with direct loads
if (Indices.size() == 1 && Indices.front() == 0)
Indices.clear();
- ArgIndices.insert(Indices);
+ ArgIndices.insert(std::make_pair(SrcTy, Indices));
LoadInst *OrigLoad;
if (LoadInst *L = dyn_cast<LoadInst>(UI))
OrigLoad = L;
for (ScalarizeTable::iterator SI = ArgIndices.begin(),
E = ArgIndices.end(); SI != E; ++SI) {
// not allowed to dereference ->begin() if size() is 0
- Params.push_back(GetElementPtrInst::getIndexedType(I->getType(), *SI));
+ Params.push_back(GetElementPtrInst::getIndexedType(
+ cast<PointerType>(I->getType()->getScalarType())->getElementType(),
+ SI->second));
assert(Params.back());
}
- if (ArgIndices.size() == 1 && ArgIndices.begin()->empty())
+ if (ArgIndices.size() == 1 && ArgIndices.begin()->second.empty())
++NumArgumentsPromoted;
else
++NumAggregatesPromoted;
Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
NF->copyAttributesFrom(F);
-
+ // Patch the pointer to LLVM function in debug info descriptor.
+ auto DI = FunctionDIs.find(F);
+ if (DI != FunctionDIs.end()) {
+ DISubprogram *SP = DI->second;
+ SP->replaceFunction(NF);
+ // Ensure the map is updated so it can be reused on subsequent argument
+ // promotions of the same function.
+ FunctionDIs.erase(DI);
+ FunctionDIs[NF] = SP;
+ }
+
DEBUG(dbgs() << "ARG PROMOTION: Promoting to:" << *NF << "\n"
<< "From: " << *F);
Type *AgTy = cast<PointerType>(I->getType())->getElementType();
StructType *STy = cast<StructType>(AgTy);
Value *Idxs[2] = {
- ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
+ ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), nullptr };
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
- Value *Idx = GetElementPtrInst::Create(*AI, Idxs,
- (*AI)->getName()+"."+utostr(i),
- Call);
+ Value *Idx = GetElementPtrInst::Create(
+ STy, *AI, Idxs, (*AI)->getName() + "." + Twine(i), Call);
// TODO: Tell AA about the new values?
Args.push_back(new LoadInst(Idx, Idx->getName()+".val", Call));
}
for (ScalarizeTable::iterator SI = ArgIndices.begin(),
E = ArgIndices.end(); SI != E; ++SI) {
Value *V = *AI;
- LoadInst *OrigLoad = OriginalLoads[std::make_pair(I, *SI)];
- if (!SI->empty()) {
- Ops.reserve(SI->size());
+ LoadInst *OrigLoad = OriginalLoads[std::make_pair(I, SI->second)];
+ if (!SI->second.empty()) {
+ Ops.reserve(SI->second.size());
Type *ElTy = V->getType();
- for (IndicesVector::const_iterator II = SI->begin(),
- IE = SI->end(); II != IE; ++II) {
+ for (IndicesVector::const_iterator II = SI->second.begin(),
+ IE = SI->second.end();
+ II != IE; ++II) {
// Use i32 to index structs, and i64 for others (pointers/arrays).
// This satisfies GEP constraints.
Type *IdxTy = (ElTy->isStructTy() ?
ElTy = cast<CompositeType>(ElTy)->getTypeAtIndex(*II);
}
// And create a GEP to extract those indices.
- V = GetElementPtrInst::Create(V, Ops, V->getName()+".idx", Call);
+ V = GetElementPtrInst::Create(SI->first, V, Ops,
+ V->getName() + ".idx", Call);
Ops.clear();
AA.copyValue(OrigLoad->getOperand(0), V);
}
// of the previous load.
LoadInst *newLoad = new LoadInst(V, V->getName()+".val", Call);
newLoad->setAlignment(OrigLoad->getAlignment());
- // Transfer the TBAA info too.
- newLoad->setMetadata(LLVMContext::MD_tbaa,
- OrigLoad->getMetadata(LLVMContext::MD_tbaa));
+ // Transfer the AA info too.
+ AAMDNodes AAInfo;
+ OrigLoad->getAAMetadata(AAInfo);
+ newLoad->setAAMetadata(AAInfo);
+
Args.push_back(newLoad);
AA.copyValue(OrigLoad, Args.back());
}
if (cast<CallInst>(Call)->isTailCall())
cast<CallInst>(New)->setTailCall();
}
+ New->setDebugLoc(Call->getDebugLoc());
Args.clear();
AttributesVec.clear();
// Update the callgraph to know that the callsite has been transformed.
CallGraphNode *CalleeNode = CG[Call->getParent()->getParent()];
- CalleeNode->replaceCallEdge(Call, New, NF_CGN);
+ CalleeNode->replaceCallEdge(CS, CallSite(New), NF_CGN);
if (!Call->use_empty()) {
Call->replaceAllUsesWith(New);
// Just add all the struct element types.
Type *AgTy = cast<PointerType>(I->getType())->getElementType();
- Value *TheAlloca = new AllocaInst(AgTy, 0, "", InsertPt);
+ Value *TheAlloca = new AllocaInst(AgTy, nullptr, "", InsertPt);
StructType *STy = cast<StructType>(AgTy);
Value *Idxs[2] = {
- ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), 0 };
+ ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), nullptr };
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
- Value *Idx =
- GetElementPtrInst::Create(TheAlloca, Idxs,
- TheAlloca->getName()+"."+Twine(i),
- InsertPt);
+ Value *Idx = GetElementPtrInst::Create(
+ AgTy, TheAlloca, Idxs, TheAlloca->getName() + "." + Twine(i),
+ InsertPt);
I2->setName(I->getName()+"."+Twine(i));
new StoreInst(I2++, Idx, InsertPt);
}
while (!I->use_empty()) {
if (LoadInst *LI = dyn_cast<LoadInst>(I->user_back())) {
- assert(ArgIndices.begin()->empty() &&
+ assert(ArgIndices.begin()->second.empty() &&
"Load element should sort to front!");
I2->setName(I->getName()+".val");
LI->replaceAllUsesWith(I2);
Function::arg_iterator TheArg = I2;
for (ScalarizeTable::iterator It = ArgIndices.begin();
- *It != Operands; ++It, ++TheArg) {
+ It->second != Operands; ++It, ++TheArg) {
assert(It != ArgIndices.end() && "GEP not handled??");
}
return NF_CGN;
}
+
+bool ArgPromotion::doInitialization(CallGraph &CG) {
+ FunctionDIs = makeSubprogramMap(CG.getModule());
+ return CallGraphSCCPass::doInitialization(CG);
+}
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