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llvm / llvm-project / llvm / 49a8cd29ed54c64b3b1fd80612508262a4a7b519 / . / lib / Transforms / IPO / AttributorAttributes.cpp
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//===- AttributorAttributes.cpp - Attributes for Attributor deduction -----===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// See the Attributor.h file comment and the class descriptions in that file for
// more information.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO/Attributor.h"
#include "llvm/ADT/SCCIterator.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/AssumeBundleQueries.h"
#include "llvm/Analysis/AssumptionCache.h"
#include "llvm/Analysis/CaptureTracking.h"
#include "llvm/Analysis/LazyValueInfo.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Analysis/ScalarEvolution.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/NoFolder.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Transforms/IPO/ArgumentPromotion.h"
#include "llvm/Transforms/Utils/Local.h"
#include <cassert>
using namespace llvm;
#define DEBUG_TYPE "attributor"
static cl::opt<bool> ManifestInternal(
"attributor-manifest-internal", cl::Hidden,
cl::desc("Manifest Attributor internal string attributes."),
cl::init(false));
static cl::opt<int> MaxHeapToStackSize("max-heap-to-stack-size", cl::init(128),
cl::Hidden);
template <>
unsigned llvm::PotentialConstantIntValuesState::MaxPotentialValues = 0;
static cl::opt<unsigned, true> MaxPotentialValues(
"attributor-max-potential-values", cl::Hidden,
cl::desc("Maximum number of potential values to be "
"tracked for each position."),
cl::location(llvm::PotentialConstantIntValuesState::MaxPotentialValues),
cl::init(7));
STATISTIC(NumAAs, "Number of abstract attributes created");
// Some helper macros to deal with statistics tracking.
//
// Usage:
// For simple IR attribute tracking overload trackStatistics in the abstract
// attribute and choose the right STATS_DECLTRACK_********* macro,
// e.g.,:
// void trackStatistics() const override {
// STATS_DECLTRACK_ARG_ATTR(returned)
// }
// If there is a single "increment" side one can use the macro
// STATS_DECLTRACK with a custom message. If there are multiple increment
// sides, STATS_DECL and STATS_TRACK can also be used separately.
//
#define BUILD_STAT_MSG_IR_ATTR(TYPE, NAME) \
("Number of " #TYPE " marked '" #NAME "'")
#define BUILD_STAT_NAME(NAME, TYPE) NumIR##TYPE##_##NAME
#define STATS_DECL_(NAME, MSG) STATISTIC(NAME, MSG);
#define STATS_DECL(NAME, TYPE, MSG) \
STATS_DECL_(BUILD_STAT_NAME(NAME, TYPE), MSG);
#define STATS_TRACK(NAME, TYPE) ++(BUILD_STAT_NAME(NAME, TYPE));
#define STATS_DECLTRACK(NAME, TYPE, MSG) \
{ \
STATS_DECL(NAME, TYPE, MSG) \
STATS_TRACK(NAME, TYPE) \
}
#define STATS_DECLTRACK_ARG_ATTR(NAME) \
STATS_DECLTRACK(NAME, Arguments, BUILD_STAT_MSG_IR_ATTR(arguments, NAME))
#define STATS_DECLTRACK_CSARG_ATTR(NAME) \
STATS_DECLTRACK(NAME, CSArguments, \
BUILD_STAT_MSG_IR_ATTR(call site arguments, NAME))
#define STATS_DECLTRACK_FN_ATTR(NAME) \
STATS_DECLTRACK(NAME, Function, BUILD_STAT_MSG_IR_ATTR(functions, NAME))
#define STATS_DECLTRACK_CS_ATTR(NAME) \
STATS_DECLTRACK(NAME, CS, BUILD_STAT_MSG_IR_ATTR(call site, NAME))
#define STATS_DECLTRACK_FNRET_ATTR(NAME) \
STATS_DECLTRACK(NAME, FunctionReturn, \
BUILD_STAT_MSG_IR_ATTR(function returns, NAME))
#define STATS_DECLTRACK_CSRET_ATTR(NAME) \
STATS_DECLTRACK(NAME, CSReturn, \
BUILD_STAT_MSG_IR_ATTR(call site returns, NAME))
#define STATS_DECLTRACK_FLOATING_ATTR(NAME) \
STATS_DECLTRACK(NAME, Floating, \
("Number of floating values known to be '" #NAME "'"))
// Specialization of the operator<< for abstract attributes subclasses. This
// disambiguates situations where multiple operators are applicable.
namespace llvm {
#define PIPE_OPERATOR(CLASS) \
raw_ostream &operator<<(raw_ostream &OS, const CLASS &AA) { \
return OS << static_cast<const AbstractAttribute &>(AA); \
}
PIPE_OPERATOR(AAIsDead)
PIPE_OPERATOR(AANoUnwind)
PIPE_OPERATOR(AANoSync)
PIPE_OPERATOR(AANoRecurse)
PIPE_OPERATOR(AAWillReturn)
PIPE_OPERATOR(AANoReturn)
PIPE_OPERATOR(AAReturnedValues)
PIPE_OPERATOR(AANonNull)
PIPE_OPERATOR(AANoAlias)
PIPE_OPERATOR(AADereferenceable)
PIPE_OPERATOR(AAAlign)
PIPE_OPERATOR(AANoCapture)
PIPE_OPERATOR(AAValueSimplify)
PIPE_OPERATOR(AANoFree)
PIPE_OPERATOR(AAHeapToStack)
PIPE_OPERATOR(AAReachability)
PIPE_OPERATOR(AAMemoryBehavior)
PIPE_OPERATOR(AAMemoryLocation)
PIPE_OPERATOR(AAValueConstantRange)
PIPE_OPERATOR(AAPrivatizablePtr)
PIPE_OPERATOR(AAUndefinedBehavior)
PIPE_OPERATOR(AAPotentialValues)
PIPE_OPERATOR(AANoUndef)
#undef PIPE_OPERATOR
} // namespace llvm
namespace {
static Optional<ConstantInt *>
getAssumedConstantInt(Attributor &A, const Value &V,
const AbstractAttribute &AA,
bool &UsedAssumedInformation) {
Optional<Constant *> C = A.getAssumedConstant(V, AA, UsedAssumedInformation);
if (C.hasValue())
return dyn_cast_or_null<ConstantInt>(C.getValue());
return llvm::None;
}
/// Get pointer operand of memory accessing instruction. If \p I is
/// not a memory accessing instruction, return nullptr. If \p AllowVolatile,
/// is set to false and the instruction is volatile, return nullptr.
static const Value *getPointerOperand(const Instruction *I,
bool AllowVolatile) {
if (!AllowVolatile && I->isVolatile())
return nullptr;
if (auto *LI = dyn_cast<LoadInst>(I)) {
return LI->getPointerOperand();
}
if (auto *SI = dyn_cast<StoreInst>(I)) {
return SI->getPointerOperand();
}
if (auto *CXI = dyn_cast<AtomicCmpXchgInst>(I)) {
return CXI->getPointerOperand();
}
if (auto *RMWI = dyn_cast<AtomicRMWInst>(I)) {
return RMWI->getPointerOperand();
}
return nullptr;
}
/// Helper function to create a pointer of type \p ResTy, based on \p Ptr, and
/// advanced by \p Offset bytes. To aid later analysis the method tries to build
/// getelement pointer instructions that traverse the natural type of \p Ptr if
/// possible. If that fails, the remaining offset is adjusted byte-wise, hence
/// through a cast to i8*.
///
/// TODO: This could probably live somewhere more prominantly if it doesn't
/// already exist.
static Value *constructPointer(Type *ResTy, Type *PtrElemTy, Value *Ptr,
int64_t Offset, IRBuilder<NoFolder> &IRB,
const DataLayout &DL) {
assert(Offset >= 0 && "Negative offset not supported yet!");
LLVM_DEBUG(dbgs() << "Construct pointer: " << *Ptr << " + " << Offset
<< "-bytes as " << *ResTy << "\n");
if (Offset) {
SmallVector<Value *, 4> Indices;
std::string GEPName = Ptr->getName().str() + ".0";
// Add 0 index to look through the pointer.
assert((uint64_t)Offset < DL.getTypeAllocSize(PtrElemTy) &&
"Offset out of bounds");
Indices.push_back(Constant::getNullValue(IRB.getInt32Ty()));
Type *Ty = PtrElemTy;
do {
auto *STy = dyn_cast<StructType>(Ty);
if (!STy)
// Non-aggregate type, we cast and make byte-wise progress now.
break;
const StructLayout *SL = DL.getStructLayout(STy);
if (int64_t(SL->getSizeInBytes()) < Offset)
break;
uint64_t Idx = SL->getElementContainingOffset(Offset);
assert(Idx < STy->getNumElements() && "Offset calculation error!");
uint64_t Rem = Offset - SL->getElementOffset(Idx);
Ty = STy->getElementType(Idx);
LLVM_DEBUG(errs() << "Ty: " << *Ty << " Offset: " << Offset
<< " Idx: " << Idx << " Rem: " << Rem << "\n");
GEPName += "." + std::to_string(Idx);
Indices.push_back(ConstantInt::get(IRB.getInt32Ty(), Idx));
Offset = Rem;
} while (Offset);
// Create a GEP for the indices collected above.
Ptr = IRB.CreateGEP(PtrElemTy, Ptr, Indices, GEPName);
// If an offset is left we use byte-wise adjustment.
if (Offset) {
Ptr = IRB.CreateBitCast(Ptr, IRB.getInt8PtrTy());
Ptr = IRB.CreateGEP(IRB.getInt8Ty(), Ptr, IRB.getInt32(Offset),
GEPName + ".b" + Twine(Offset));
}
}
// Ensure the result has the requested type.
Ptr = IRB.CreateBitOrPointerCast(Ptr, ResTy, Ptr->getName() + ".cast");
LLVM_DEBUG(dbgs() << "Constructed pointer: " << *Ptr << "\n");
return Ptr;
}
/// Recursively visit all values that might become \p IRP at some point. This
/// will be done by looking through cast instructions, selects, phis, and calls
/// with the "returned" attribute. Once we cannot look through the value any
/// further, the callback \p VisitValueCB is invoked and passed the current
/// value, the \p State, and a flag to indicate if we stripped anything.
/// Stripped means that we unpacked the value associated with \p IRP at least
/// once. Note that the value used for the callback may still be the value
/// associated with \p IRP (due to PHIs). To limit how much effort is invested,
/// we will never visit more values than specified by \p MaxValues.
template <typename AAType, typename StateTy>
static bool genericValueTraversal(
Attributor &A, IRPosition IRP, const AAType &QueryingAA, StateTy &State,
function_ref<bool(Value &, const Instruction *, StateTy &, bool)>
VisitValueCB,
const Instruction *CtxI, bool UseValueSimplify = true, int MaxValues = 16,
function_ref<Value *(Value *)> StripCB = nullptr) {
const AAIsDead *LivenessAA = nullptr;
if (IRP.getAnchorScope())
LivenessAA = &A.getAAFor<AAIsDead>(
QueryingAA, IRPosition::function(*IRP.getAnchorScope()),
DepClassTy::NONE);
bool AnyDead = false;
using Item = std::pair<Value *, const Instruction *>;
SmallSet<Item, 16> Visited;
SmallVector<Item, 16> Worklist;
Worklist.push_back({&IRP.getAssociatedValue(), CtxI});
int Iteration = 0;
do {
Item I = Worklist.pop_back_val();
Value *V = I.first;
CtxI = I.second;
if (StripCB)
V = StripCB(V);
// Check if we should process the current value. To prevent endless
// recursion keep a record of the values we followed!
if (!Visited.insert(I).second)
continue;
// Make sure we limit the compile time for complex expressions.
if (Iteration++ >= MaxValues)
return false;
// Explicitly look through calls with a "returned" attribute if we do
// not have a pointer as stripPointerCasts only works on them.
Value *NewV = nullptr;
if (V->getType()->isPointerTy()) {
NewV = V->stripPointerCasts();
} else {
auto *CB = dyn_cast<CallBase>(V);
if (CB && CB->getCalledFunction()) {
for (Argument &Arg : CB->getCalledFunction()->args())
if (Arg.hasReturnedAttr()) {
NewV = CB->getArgOperand(Arg.getArgNo());
break;
}
}
}
if (NewV && NewV != V) {
Worklist.push_back({NewV, CtxI});
continue;
}
// Look through select instructions, visit both potential values.
if (auto *SI = dyn_cast<SelectInst>(V)) {
Worklist.push_back({SI->getTrueValue(), CtxI});
Worklist.push_back({SI->getFalseValue(), CtxI});
continue;
}
// Look through phi nodes, visit all live operands.
if (auto *PHI = dyn_cast<PHINode>(V)) {
assert(LivenessAA &&
"Expected liveness in the presence of instructions!");
for (unsigned u = 0, e = PHI->getNumIncomingValues(); u < e; u++) {
BasicBlock *IncomingBB = PHI->getIncomingBlock(u);
if (A.isAssumedDead(*IncomingBB->getTerminator(), &QueryingAA,
LivenessAA,
/* CheckBBLivenessOnly */ true)) {
AnyDead = true;
continue;
}
Worklist.push_back(
{PHI->getIncomingValue(u), IncomingBB->getTerminator()});
}
continue;
}
if (UseValueSimplify && !isa<Constant>(V)) {
bool UsedAssumedInformation = false;
Optional<Constant *> C =
A.getAssumedConstant(*V, QueryingAA, UsedAssumedInformation);
if (!C.hasValue())
continue;
if (Value *NewV = C.getValue()) {
Worklist.push_back({NewV, CtxI});
continue;
}
}
// Once a leaf is reached we inform the user through the callback.
if (!VisitValueCB(*V, CtxI, State, Iteration > 1))
return false;
} while (!Worklist.empty());
// If we actually used liveness information so we have to record a dependence.
if (AnyDead)
A.recordDependence(*LivenessAA, QueryingAA, DepClassTy::OPTIONAL);
// All values have been visited.
return true;
}
const Value *stripAndAccumulateMinimalOffsets(
Attributor &A, const AbstractAttribute &QueryingAA, const Value *Val,
const DataLayout &DL, APInt &Offset, bool AllowNonInbounds,
bool UseAssumed = false) {
auto AttributorAnalysis = [&](Value &V, APInt &ROffset) -> bool {
const IRPosition &Pos = IRPosition::value(V);
// Only track dependence if we are going to use the assumed info.
const AAValueConstantRange &ValueConstantRangeAA =
A.getAAFor<AAValueConstantRange>(QueryingAA, Pos,
UseAssumed ? DepClassTy::OPTIONAL
: DepClassTy::NONE);
ConstantRange Range = UseAssumed ? ValueConstantRangeAA.getAssumed()
: ValueConstantRangeAA.getKnown();
// We can only use the lower part of the range because the upper part can
// be higher than what the value can really be.
ROffset = Range.getSignedMin();
return true;
};
return Val->stripAndAccumulateConstantOffsets(DL, Offset, AllowNonInbounds,
AttributorAnalysis);
}
static const Value *getMinimalBaseOfAccsesPointerOperand(
Attributor &A, const AbstractAttribute &QueryingAA, const Instruction *I,
int64_t &BytesOffset, const DataLayout &DL, bool AllowNonInbounds = false) {
const Value *Ptr = getPointerOperand(I, /* AllowVolatile */ false);
if (!Ptr)
return nullptr;
APInt OffsetAPInt(DL.getIndexTypeSizeInBits(Ptr->getType()), 0);
const Value *Base = stripAndAccumulateMinimalOffsets(
A, QueryingAA, Ptr, DL, OffsetAPInt, AllowNonInbounds);
BytesOffset = OffsetAPInt.getSExtValue();
return Base;
}
static const Value *
getBasePointerOfAccessPointerOperand(const Instruction *I, int64_t &BytesOffset,
const DataLayout &DL,
bool AllowNonInbounds = false) {
const Value *Ptr = getPointerOperand(I, /* AllowVolatile */ false);
if (!Ptr)
return nullptr;
return GetPointerBaseWithConstantOffset(Ptr, BytesOffset, DL,
AllowNonInbounds);
}
/// Helper function to clamp a state \p S of type \p StateType with the
/// information in \p R and indicate/return if \p S did change (as-in update is
/// required to be run again).
template <typename StateType>
ChangeStatus clampStateAndIndicateChange(StateType &S, const StateType &R) {
auto Assumed = S.getAssumed();
S ^= R;
return Assumed == S.getAssumed() ? ChangeStatus::UNCHANGED
: ChangeStatus::CHANGED;
}
/// Clamp the information known for all returned values of a function
/// (identified by \p QueryingAA) into \p S.
template <typename AAType, typename StateType = typename AAType::StateType>
static void clampReturnedValueStates(
Attributor &A, const AAType &QueryingAA, StateType &S,
const IRPosition::CallBaseContext *CBContext = nullptr) {
LLVM_DEBUG(dbgs() << "[Attributor] Clamp return value states for "
<< QueryingAA << " into " << S << "\n");
assert((QueryingAA.getIRPosition().getPositionKind() ==
IRPosition::IRP_RETURNED ||
QueryingAA.getIRPosition().getPositionKind() ==
IRPosition::IRP_CALL_SITE_RETURNED) &&
"Can only clamp returned value states for a function returned or call "
"site returned position!");
// Use an optional state as there might not be any return values and we want
// to join (IntegerState::operator&) the state of all there are.
Optional<StateType> T;
// Callback for each possibly returned value.
auto CheckReturnValue = [&](Value &RV) -> bool {
const IRPosition &RVPos = IRPosition::value(RV, CBContext);
const AAType &AA =
A.getAAFor<AAType>(QueryingAA, RVPos, DepClassTy::REQUIRED);
LLVM_DEBUG(dbgs() << "[Attributor] RV: " << RV << " AA: " << AA.getAsStr()
<< " @ " << RVPos << "\n");
const StateType &AAS = AA.getState();
if (T.hasValue())
*T &= AAS;
else
T = AAS;
LLVM_DEBUG(dbgs() << "[Attributor] AA State: " << AAS << " RV State: " << T
<< "\n");
return T->isValidState();
};
if (!A.checkForAllReturnedValues(CheckReturnValue, QueryingAA))
S.indicatePessimisticFixpoint();
else if (T.hasValue())
S ^= *T;
}
/// Helper class for generic deduction: return value -> returned position.
template <typename AAType, typename BaseType,
typename StateType = typename BaseType::StateType,
bool PropagateCallBaseContext = false>
struct AAReturnedFromReturnedValues : public BaseType {
AAReturnedFromReturnedValues(const IRPosition &IRP, Attributor &A)
: BaseType(IRP, A) {}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
StateType S(StateType::getBestState(this->getState()));
clampReturnedValueStates<AAType, StateType>(
A, *this, S,
PropagateCallBaseContext ? this->getCallBaseContext() : nullptr);
// TODO: If we know we visited all returned values, thus no are assumed
// dead, we can take the known information from the state T.
return clampStateAndIndicateChange<StateType>(this->getState(), S);
}
};
/// Clamp the information known at all call sites for a given argument
/// (identified by \p QueryingAA) into \p S.
template <typename AAType, typename StateType = typename AAType::StateType>
static void clampCallSiteArgumentStates(Attributor &A, const AAType &QueryingAA,
StateType &S) {
LLVM_DEBUG(dbgs() << "[Attributor] Clamp call site argument states for "
<< QueryingAA << " into " << S << "\n");
assert(QueryingAA.getIRPosition().getPositionKind() ==
IRPosition::IRP_ARGUMENT &&
"Can only clamp call site argument states for an argument position!");
// Use an optional state as there might not be any return values and we want
// to join (IntegerState::operator&) the state of all there are.
Optional<StateType> T;
// The argument number which is also the call site argument number.
unsigned ArgNo = QueryingAA.getIRPosition().getCallSiteArgNo();
auto CallSiteCheck = [&](AbstractCallSite ACS) {
const IRPosition &ACSArgPos = IRPosition::callsite_argument(ACS, ArgNo);
// Check if a coresponding argument was found or if it is on not associated
// (which can happen for callback calls).
if (ACSArgPos.getPositionKind() == IRPosition::IRP_INVALID)
return false;
const AAType &AA =
A.getAAFor<AAType>(QueryingAA, ACSArgPos, DepClassTy::REQUIRED);
LLVM_DEBUG(dbgs() << "[Attributor] ACS: " << *ACS.getInstruction()
<< " AA: " << AA.getAsStr() << " @" << ACSArgPos << "\n");
const StateType &AAS = AA.getState();
if (T.hasValue())
*T &= AAS;
else
T = AAS;
LLVM_DEBUG(dbgs() << "[Attributor] AA State: " << AAS << " CSA State: " << T
<< "\n");
return T->isValidState();
};
bool AllCallSitesKnown;
if (!A.checkForAllCallSites(CallSiteCheck, QueryingAA, true,
AllCallSitesKnown))
S.indicatePessimisticFixpoint();
else if (T.hasValue())
S ^= *T;
}
/// This function is the bridge between argument position and the call base
/// context.
template <typename AAType, typename BaseType,
typename StateType = typename AAType::StateType>
bool getArgumentStateFromCallBaseContext(Attributor &A,
BaseType &QueryingAttribute,
IRPosition &Pos, StateType &State) {
assert((Pos.getPositionKind() == IRPosition::IRP_ARGUMENT) &&
"Expected an 'argument' position !");
const CallBase *CBContext = Pos.getCallBaseContext();
if (!CBContext)
return false;
int ArgNo = Pos.getCallSiteArgNo();
assert(ArgNo >= 0 && "Invalid Arg No!");
const auto &AA = A.getAAFor<AAType>(
QueryingAttribute, IRPosition::callsite_argument(*CBContext, ArgNo),
DepClassTy::REQUIRED);
const StateType &CBArgumentState =
static_cast<const StateType &>(AA.getState());
LLVM_DEBUG(dbgs() << "[Attributor] Briding Call site context to argument"
<< "Position:" << Pos << "CB Arg state:" << CBArgumentState
<< "\n");
// NOTE: If we want to do call site grouping it should happen here.
State ^= CBArgumentState;
return true;
}
/// Helper class for generic deduction: call site argument -> argument position.
template <typename AAType, typename BaseType,
typename StateType = typename AAType::StateType,
bool BridgeCallBaseContext = false>
struct AAArgumentFromCallSiteArguments : public BaseType {
AAArgumentFromCallSiteArguments(const IRPosition &IRP, Attributor &A)
: BaseType(IRP, A) {}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
StateType S = StateType::getBestState(this->getState());
if (BridgeCallBaseContext) {
bool Success =
getArgumentStateFromCallBaseContext<AAType, BaseType, StateType>(
A, *this, this->getIRPosition(), S);
if (Success)
return clampStateAndIndicateChange<StateType>(this->getState(), S);
}
clampCallSiteArgumentStates<AAType, StateType>(A, *this, S);
// TODO: If we know we visited all incoming values, thus no are assumed
// dead, we can take the known information from the state T.
return clampStateAndIndicateChange<StateType>(this->getState(), S);
}
};
/// Helper class for generic replication: function returned -> cs returned.
template <typename AAType, typename BaseType,
typename StateType = typename BaseType::StateType,
bool IntroduceCallBaseContext = false>
struct AACallSiteReturnedFromReturned : public BaseType {
AACallSiteReturnedFromReturned(const IRPosition &IRP, Attributor &A)
: BaseType(IRP, A) {}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
assert(this->getIRPosition().getPositionKind() ==
IRPosition::IRP_CALL_SITE_RETURNED &&
"Can only wrap function returned positions for call site returned "
"positions!");
auto &S = this->getState();
const Function *AssociatedFunction =
this->getIRPosition().getAssociatedFunction();
if (!AssociatedFunction)
return S.indicatePessimisticFixpoint();
CallBase &CBContext = static_cast<CallBase &>(this->getAnchorValue());
if (IntroduceCallBaseContext)
LLVM_DEBUG(dbgs() << "[Attributor] Introducing call base context:"
<< CBContext << "\n");
IRPosition FnPos = IRPosition::returned(
*AssociatedFunction, IntroduceCallBaseContext ? &CBContext : nullptr);
const AAType &AA = A.getAAFor<AAType>(*this, FnPos, DepClassTy::REQUIRED);
return clampStateAndIndicateChange(S, AA.getState());
}
};
/// Helper function to accumulate uses.
template <class AAType, typename StateType = typename AAType::StateType>
static void followUsesInContext(AAType &AA, Attributor &A,
MustBeExecutedContextExplorer &Explorer,
const Instruction *CtxI,
SetVector<const Use *> &Uses,
StateType &State) {
auto EIt = Explorer.begin(CtxI), EEnd = Explorer.end(CtxI);
for (unsigned u = 0; u < Uses.size(); ++u) {
const Use *U = Uses[u];
if (const Instruction *UserI = dyn_cast<Instruction>(U->getUser())) {
bool Found = Explorer.findInContextOf(UserI, EIt, EEnd);
if (Found && AA.followUseInMBEC(A, U, UserI, State))
for (const Use &Us : UserI->uses())
Uses.insert(&Us);
}
}
}
/// Use the must-be-executed-context around \p I to add information into \p S.
/// The AAType class is required to have `followUseInMBEC` method with the
/// following signature and behaviour:
///
/// bool followUseInMBEC(Attributor &A, const Use *U, const Instruction *I)
/// U - Underlying use.
/// I - The user of the \p U.
/// Returns true if the value should be tracked transitively.
///
template <class AAType, typename StateType = typename AAType::StateType>
static void followUsesInMBEC(AAType &AA, Attributor &A, StateType &S,
Instruction &CtxI) {
// Container for (transitive) uses of the associated value.
SetVector<const Use *> Uses;
for (const Use &U : AA.getIRPosition().getAssociatedValue().uses())
Uses.insert(&U);
MustBeExecutedContextExplorer &Explorer =
A.getInfoCache().getMustBeExecutedContextExplorer();
followUsesInContext<AAType>(AA, A, Explorer, &CtxI, Uses, S);
if (S.isAtFixpoint())
return;
SmallVector<const BranchInst *, 4> BrInsts;
auto Pred = [&](const Instruction *I) {
if (const BranchInst *Br = dyn_cast<BranchInst>(I))
if (Br->isConditional())
BrInsts.push_back(Br);
return true;
};
// Here, accumulate conditional branch instructions in the context. We
// explore the child paths and collect the known states. The disjunction of
// those states can be merged to its own state. Let ParentState_i be a state
// to indicate the known information for an i-th branch instruction in the
// context. ChildStates are created for its successors respectively.
//
// ParentS_1 = ChildS_{1, 1} /\ ChildS_{1, 2} /\ ... /\ ChildS_{1, n_1}
// ParentS_2 = ChildS_{2, 1} /\ ChildS_{2, 2} /\ ... /\ ChildS_{2, n_2}
// ...
// ParentS_m = ChildS_{m, 1} /\ ChildS_{m, 2} /\ ... /\ ChildS_{m, n_m}
//
// Known State |= ParentS_1 \/ ParentS_2 \/... \/ ParentS_m
//
// FIXME: Currently, recursive branches are not handled. For example, we
// can't deduce that ptr must be dereferenced in below function.
//
// void f(int a, int c, int *ptr) {
// if(a)
// if (b) {
// *ptr = 0;
// } else {
// *ptr = 1;
// }
// else {
// if (b) {
// *ptr = 0;
// } else {
// *ptr = 1;
// }
// }
// }
Explorer.checkForAllContext(&CtxI, Pred);
for (const BranchInst *Br : BrInsts) {
StateType ParentState;
// The known state of the parent state is a conjunction of children's
// known states so it is initialized with a best state.
ParentState.indicateOptimisticFixpoint();
for (const BasicBlock *BB : Br->successors()) {
StateType ChildState;
size_t BeforeSize = Uses.size();
followUsesInContext(AA, A, Explorer, &BB->front(), Uses, ChildState);
// Erase uses which only appear in the child.
for (auto It = Uses.begin() + BeforeSize; It != Uses.end();)
It = Uses.erase(It);
ParentState &= ChildState;
}
// Use only known state.
S += ParentState;
}
}
/// -----------------------NoUnwind Function Attribute--------------------------
struct AANoUnwindImpl : AANoUnwind {
AANoUnwindImpl(const IRPosition &IRP, Attributor &A) : AANoUnwind(IRP, A) {}
const std::string getAsStr() const override {
return getAssumed() ? "nounwind" : "may-unwind";
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
auto Opcodes = {
(unsigned)Instruction::Invoke, (unsigned)Instruction::CallBr,
(unsigned)Instruction::Call, (unsigned)Instruction::CleanupRet,
(unsigned)Instruction::CatchSwitch, (unsigned)Instruction::Resume};
auto CheckForNoUnwind = [&](Instruction &I) {
if (!I.mayThrow())
return true;
if (const auto *CB = dyn_cast<CallBase>(&I)) {
const auto &NoUnwindAA = A.getAAFor<AANoUnwind>(
*this, IRPosition::callsite_function(*CB), DepClassTy::REQUIRED);
return NoUnwindAA.isAssumedNoUnwind();
}
return false;
};
if (!A.checkForAllInstructions(CheckForNoUnwind, *this, Opcodes))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
};
struct AANoUnwindFunction final : public AANoUnwindImpl {
AANoUnwindFunction(const IRPosition &IRP, Attributor &A)
: AANoUnwindImpl(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_FN_ATTR(nounwind) }
};
/// NoUnwind attribute deduction for a call sites.
struct AANoUnwindCallSite final : AANoUnwindImpl {
AANoUnwindCallSite(const IRPosition &IRP, Attributor &A)
: AANoUnwindImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AANoUnwindImpl::initialize(A);
Function *F = getAssociatedFunction();
if (!F || F->isDeclaration())
indicatePessimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
// TODO: Once we have call site specific value information we can provide
// call site specific liveness information and then it makes
// sense to specialize attributes for call sites arguments instead of
// redirecting requests to the callee argument.
Function *F = getAssociatedFunction();
const IRPosition &FnPos = IRPosition::function(*F);
auto &FnAA = A.getAAFor<AANoUnwind>(*this, FnPos, DepClassTy::REQUIRED);
return clampStateAndIndicateChange(getState(), FnAA.getState());
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_CS_ATTR(nounwind); }
};
/// --------------------- Function Return Values -------------------------------
/// "Attribute" that collects all potential returned values and the return
/// instructions that they arise from.
///
/// If there is a unique returned value R, the manifest method will:
/// - mark R with the "returned" attribute, if R is an argument.
class AAReturnedValuesImpl : public AAReturnedValues, public AbstractState {
/// Mapping of values potentially returned by the associated function to the
/// return instructions that might return them.
MapVector<Value *, SmallSetVector<ReturnInst *, 4>> ReturnedValues;
/// Mapping to remember the number of returned values for a call site such
/// that we can avoid updates if nothing changed.
DenseMap<const CallBase *, unsigned> NumReturnedValuesPerKnownAA;
/// Set of unresolved calls returned by the associated function.
SmallSetVector<CallBase *, 4> UnresolvedCalls;
/// State flags
///
///{
bool IsFixed = false;
bool IsValidState = true;
///}
public:
AAReturnedValuesImpl(const IRPosition &IRP, Attributor &A)
: AAReturnedValues(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
// Reset the state.
IsFixed = false;
IsValidState = true;
ReturnedValues.clear();
Function *F = getAssociatedFunction();
if (!F || F->isDeclaration()) {
indicatePessimisticFixpoint();
return;
}
assert(!F->getReturnType()->isVoidTy() &&
"Did not expect a void return type!");
// The map from instruction opcodes to those instructions in the function.
auto &OpcodeInstMap = A.getInfoCache().getOpcodeInstMapForFunction(*F);
// Look through all arguments, if one is marked as returned we are done.
for (Argument &Arg : F->args()) {
if (Arg.hasReturnedAttr()) {
auto &ReturnInstSet = ReturnedValues[&Arg];
if (auto *Insts = OpcodeInstMap.lookup(Instruction::Ret))
for (Instruction *RI : *Insts)
ReturnInstSet.insert(cast<ReturnInst>(RI));
indicateOptimisticFixpoint();
return;
}
}
if (!A.isFunctionIPOAmendable(*F))
indicatePessimisticFixpoint();
}
/// See AbstractAttribute::manifest(...).
ChangeStatus manifest(Attributor &A) override;
/// See AbstractAttribute::getState(...).
AbstractState &getState() override { return *this; }
/// See AbstractAttribute::getState(...).
const AbstractState &getState() const override { return *this; }
/// See AbstractAttribute::updateImpl(Attributor &A).
ChangeStatus updateImpl(Attributor &A) override;
llvm::iterator_range<iterator> returned_values() override {
return llvm::make_range(ReturnedValues.begin(), ReturnedValues.end());
}
llvm::iterator_range<const_iterator> returned_values() const override {
return llvm::make_range(ReturnedValues.begin(), ReturnedValues.end());
}
const SmallSetVector<CallBase *, 4> &getUnresolvedCalls() const override {
return UnresolvedCalls;
}
/// Return the number of potential return values, -1 if unknown.
size_t getNumReturnValues() const override {
return isValidState() ? ReturnedValues.size() : -1;
}
/// Return an assumed unique return value if a single candidate is found. If
/// there cannot be one, return a nullptr. If it is not clear yet, return the
/// Optional::NoneType.
Optional<Value *> getAssumedUniqueReturnValue(Attributor &A) const;
/// See AbstractState::checkForAllReturnedValues(...).
bool checkForAllReturnedValuesAndReturnInsts(
function_ref<bool(Value &, const SmallSetVector<ReturnInst *, 4> &)> Pred)
const override;
/// Pretty print the attribute similar to the IR representation.
const std::string getAsStr() const override;
/// See AbstractState::isAtFixpoint().
bool isAtFixpoint() const override { return IsFixed; }
/// See AbstractState::isValidState().
bool isValidState() const override { return IsValidState; }
/// See AbstractState::indicateOptimisticFixpoint(...).
ChangeStatus indicateOptimisticFixpoint() override {
IsFixed = true;
return ChangeStatus::UNCHANGED;
}
ChangeStatus indicatePessimisticFixpoint() override {
IsFixed = true;
IsValidState = false;
return ChangeStatus::CHANGED;
}
};
ChangeStatus AAReturnedValuesImpl::manifest(Attributor &A) {
ChangeStatus Changed = ChangeStatus::UNCHANGED;
// Bookkeeping.
assert(isValidState());
STATS_DECLTRACK(KnownReturnValues, FunctionReturn,
"Number of function with known return values");
// Check if we have an assumed unique return value that we could manifest.
Optional<Value *> UniqueRV = getAssumedUniqueReturnValue(A);
if (!UniqueRV.hasValue() || !UniqueRV.getValue())
return Changed;
// Bookkeeping.
STATS_DECLTRACK(UniqueReturnValue, FunctionReturn,
"Number of function with unique return");
// Callback to replace the uses of CB with the constant C.
auto ReplaceCallSiteUsersWith = [&A](CallBase &CB, Constant &C) {
if (CB.use_empty())
return ChangeStatus::UNCHANGED;
if (A.changeValueAfterManifest(CB, C))
return ChangeStatus::CHANGED;
return ChangeStatus::UNCHANGED;
};
// If the assumed unique return value is an argument, annotate it.
if (auto *UniqueRVArg = dyn_cast<Argument>(UniqueRV.getValue())) {
if (UniqueRVArg->getType()->canLosslesslyBitCastTo(
getAssociatedFunction()->getReturnType())) {
getIRPosition() = IRPosition::argument(*UniqueRVArg);
Changed = IRAttribute::manifest(A);
}
} else if (auto *RVC = dyn_cast<Constant>(UniqueRV.getValue())) {
// We can replace the returned value with the unique returned constant.
Value &AnchorValue = getAnchorValue();
if (Function *F = dyn_cast<Function>(&AnchorValue)) {
for (const Use &U : F->uses())
if (CallBase *CB = dyn_cast<CallBase>(U.getUser()))
if (CB->isCallee(&U)) {
Constant *RVCCast =
CB->getType() == RVC->getType()
? RVC
: ConstantExpr::getTruncOrBitCast(RVC, CB->getType());
Changed = ReplaceCallSiteUsersWith(*CB, *RVCCast) | Changed;
}
} else {
assert(isa<CallBase>(AnchorValue) &&
"Expcected a function or call base anchor!");
Constant *RVCCast =
AnchorValue.getType() == RVC->getType()
? RVC
: ConstantExpr::getTruncOrBitCast(RVC, AnchorValue.getType());
Changed = ReplaceCallSiteUsersWith(cast<CallBase>(AnchorValue), *RVCCast);
}
if (Changed == ChangeStatus::CHANGED)
STATS_DECLTRACK(UniqueConstantReturnValue, FunctionReturn,
"Number of function returns replaced by constant return");
}
return Changed;
}
const std::string AAReturnedValuesImpl::getAsStr() const {
return (isAtFixpoint() ? "returns(#" : "may-return(#") +
(isValidState() ? std::to_string(getNumReturnValues()) : "?") +
")[#UC: " + std::to_string(UnresolvedCalls.size()) + "]";
}
Optional<Value *>
AAReturnedValuesImpl::getAssumedUniqueReturnValue(Attributor &A) const {
// If checkForAllReturnedValues provides a unique value, ignoring potential
// undef values that can also be present, it is assumed to be the actual
// return value and forwarded to the caller of this method. If there are
// multiple, a nullptr is returned indicating there cannot be a unique
// returned value.
Optional<Value *> UniqueRV;
auto Pred = [&](Value &RV) -> bool {
// If we found a second returned value and neither the current nor the saved
// one is an undef, there is no unique returned value. Undefs are special
// since we can pretend they have any value.
if (UniqueRV.hasValue() && UniqueRV != &RV &&
!(isa<UndefValue>(RV) || isa<UndefValue>(UniqueRV.getValue()))) {
UniqueRV = nullptr;
return false;
}
// Do not overwrite a value with an undef.
if (!UniqueRV.hasValue() || !isa<UndefValue>(RV))
UniqueRV = &RV;
return true;
};
if (!A.checkForAllReturnedValues(Pred, *this))
UniqueRV = nullptr;
return UniqueRV;
}
bool AAReturnedValuesImpl::checkForAllReturnedValuesAndReturnInsts(
function_ref<bool(Value &, const SmallSetVector<ReturnInst *, 4> &)> Pred)
const {
if (!isValidState())
return false;
// Check all returned values but ignore call sites as long as we have not
// encountered an overdefined one during an update.
for (auto &It : ReturnedValues) {
Value *RV = It.first;
CallBase *CB = dyn_cast<CallBase>(RV);
if (CB && !UnresolvedCalls.count(CB))
continue;
if (!Pred(*RV, It.second))
return false;
}
return true;
}
ChangeStatus AAReturnedValuesImpl::updateImpl(Attributor &A) {
size_t NumUnresolvedCalls = UnresolvedCalls.size();
bool Changed = false;
// State used in the value traversals starting in returned values.
struct RVState {
// The map in which we collect return values -> return instrs.
decltype(ReturnedValues) &RetValsMap;
// The flag to indicate a change.
bool &Changed;
// The return instrs we come from.
SmallSetVector<ReturnInst *, 4> RetInsts;
};
// Callback for a leaf value returned by the associated function.
auto VisitValueCB = [](Value &Val, const Instruction *, RVState &RVS,
bool) -> bool {
auto Size = RVS.RetValsMap[&Val].size();
RVS.RetValsMap[&Val].insert(RVS.RetInsts.begin(), RVS.RetInsts.end());
bool Inserted = RVS.RetValsMap[&Val].size() != Size;
RVS.Changed |= Inserted;
LLVM_DEBUG({
if (Inserted)
dbgs() << "[AAReturnedValues] 1 Add new returned value " << Val
<< " => " << RVS.RetInsts.size() << "\n";
});
return true;
};
// Helper method to invoke the generic value traversal.
auto VisitReturnedValue = [&](Value &RV, RVState &RVS,
const Instruction *CtxI) {
IRPosition RetValPos = IRPosition::value(RV);
return genericValueTraversal<AAReturnedValues, RVState>(
A, RetValPos, *this, RVS, VisitValueCB, CtxI,
/* UseValueSimplify */ false);
};
// Callback for all "return intructions" live in the associated function.
auto CheckReturnInst = [this, &VisitReturnedValue, &Changed](Instruction &I) {
ReturnInst &Ret = cast<ReturnInst>(I);
RVState RVS({ReturnedValues, Changed, {}});
RVS.RetInsts.insert(&Ret);
return VisitReturnedValue(*Ret.getReturnValue(), RVS, &I);
};
// Start by discovering returned values from all live returned instructions in
// the associated function.
if (!A.checkForAllInstructions(CheckReturnInst, *this, {Instruction::Ret}))
return indicatePessimisticFixpoint();
// Once returned values "directly" present in the code are handled we try to
// resolve returned calls. To avoid modifications to the ReturnedValues map
// while we iterate over it we kept record of potential new entries in a copy
// map, NewRVsMap.
decltype(ReturnedValues) NewRVsMap;
auto HandleReturnValue = [&](Value *RV,
SmallSetVector<ReturnInst *, 4> &RIs) {
LLVM_DEBUG(dbgs() << "[AAReturnedValues] Returned value: " << *RV << " by #"
<< RIs.size() << " RIs\n");
CallBase *CB = dyn_cast<CallBase>(RV);
if (!CB || UnresolvedCalls.count(CB))
return;
if (!CB->getCalledFunction()) {
LLVM_DEBUG(dbgs() << "[AAReturnedValues] Unresolved call: " << *CB
<< "\n");
UnresolvedCalls.insert(CB);
return;
}
// TODO: use the function scope once we have call site AAReturnedValues.
const auto &RetValAA = A.getAAFor<AAReturnedValues>(
*this, IRPosition::function(*CB->getCalledFunction()),
DepClassTy::REQUIRED);
LLVM_DEBUG(dbgs() << "[AAReturnedValues] Found another AAReturnedValues: "
<< RetValAA << "\n");
// Skip dead ends, thus if we do not know anything about the returned
// call we mark it as unresolved and it will stay that way.
if (!RetValAA.getState().isValidState()) {
LLVM_DEBUG(dbgs() << "[AAReturnedValues] Unresolved call: " << *CB
<< "\n");
UnresolvedCalls.insert(CB);
return;
}
// Do not try to learn partial information. If the callee has unresolved
// return values we will treat the call as unresolved/opaque.
auto &RetValAAUnresolvedCalls = RetValAA.getUnresolvedCalls();
if (!RetValAAUnresolvedCalls.empty()) {
UnresolvedCalls.insert(CB);
return;
}
// Now check if we can track transitively returned values. If possible, thus
// if all return value can be represented in the current scope, do so.
bool Unresolved = false;
for (auto &RetValAAIt : RetValAA.returned_values()) {
Value *RetVal = RetValAAIt.first;
if (isa<Argument>(RetVal) || isa<CallBase>(RetVal) ||
isa<Constant>(RetVal))
continue;
// Anything that did not fit in the above categories cannot be resolved,
// mark the call as unresolved.
LLVM_DEBUG(dbgs() << "[AAReturnedValues] transitively returned value "
"cannot be translated: "
<< *RetVal << "\n");
UnresolvedCalls.insert(CB);
Unresolved = true;
break;
}
if (Unresolved)
return;
// Now track transitively returned values.
unsigned &NumRetAA = NumReturnedValuesPerKnownAA[CB];
if (NumRetAA == RetValAA.getNumReturnValues()) {
LLVM_DEBUG(dbgs() << "[AAReturnedValues] Skip call as it has not "
"changed since it was seen last\n");
return;
}
NumRetAA = RetValAA.getNumReturnValues();
for (auto &RetValAAIt : RetValAA.returned_values()) {
Value *RetVal = RetValAAIt.first;
if (Argument *Arg = dyn_cast<Argument>(RetVal)) {
// Arguments are mapped to call site operands and we begin the traversal
// again.
bool Unused = false;
RVState RVS({NewRVsMap, Unused, RetValAAIt.second});
VisitReturnedValue(*CB->getArgOperand(Arg->getArgNo()), RVS, CB);
continue;
}
if (isa<CallBase>(RetVal)) {
// Call sites are resolved by the callee attribute over time, no need to
// do anything for us.
continue;
}
if (isa<Constant>(RetVal)) {
// Constants are valid everywhere, we can simply take them.
NewRVsMap[RetVal].insert(RIs.begin(), RIs.end());
continue;
}
}
};
for (auto &It : ReturnedValues)
HandleReturnValue(It.first, It.second);
// Because processing the new information can again lead to new return values
// we have to be careful and iterate until this iteration is complete. The
// idea is that we are in a stable state at the end of an update. All return
// values have been handled and properly categorized. We might not update
// again if we have not requested a non-fix attribute so we cannot "wait" for
// the next update to analyze a new return value.
while (!NewRVsMap.empty()) {
auto It = std::move(NewRVsMap.back());
NewRVsMap.pop_back();
assert(!It.second.empty() && "Entry does not add anything.");
auto &ReturnInsts = ReturnedValues[It.first];
for (ReturnInst *RI : It.second)
if (ReturnInsts.insert(RI)) {
LLVM_DEBUG(dbgs() << "[AAReturnedValues] Add new returned value "
<< *It.first << " => " << *RI << "\n");
HandleReturnValue(It.first, ReturnInsts);
Changed = true;
}
}
Changed |= (NumUnresolvedCalls != UnresolvedCalls.size());
return Changed ? ChangeStatus::CHANGED : ChangeStatus::UNCHANGED;
}
struct AAReturnedValuesFunction final : public AAReturnedValuesImpl {
AAReturnedValuesFunction(const IRPosition &IRP, Attributor &A)
: AAReturnedValuesImpl(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_ARG_ATTR(returned) }
};
/// Returned values information for a call sites.
struct AAReturnedValuesCallSite final : AAReturnedValuesImpl {
AAReturnedValuesCallSite(const IRPosition &IRP, Attributor &A)
: AAReturnedValuesImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
// TODO: Once we have call site specific value information we can provide
// call site specific liveness information and then it makes
// sense to specialize attributes for call sites instead of
// redirecting requests to the callee.
llvm_unreachable("Abstract attributes for returned values are not "
"supported for call sites yet!");
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
return indicatePessimisticFixpoint();
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {}
};
/// ------------------------ NoSync Function Attribute -------------------------
struct AANoSyncImpl : AANoSync {
AANoSyncImpl(const IRPosition &IRP, Attributor &A) : AANoSync(IRP, A) {}
const std::string getAsStr() const override {
return getAssumed() ? "nosync" : "may-sync";
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// Helper function used to determine whether an instruction is non-relaxed
/// atomic. In other words, if an atomic instruction does not have unordered
/// or monotonic ordering
static bool isNonRelaxedAtomic(Instruction *I);
/// Helper function specific for intrinsics which are potentially volatile
static bool isNoSyncIntrinsic(Instruction *I);
};
bool AANoSyncImpl::isNonRelaxedAtomic(Instruction *I) {
if (!I->isAtomic())
return false;
if (auto *FI = dyn_cast<FenceInst>(I))
// All legal orderings for fence are stronger than monotonic.
return FI->getSyncScopeID() != SyncScope::SingleThread;
else if (auto *AI = dyn_cast<AtomicCmpXchgInst>(I)) {
// Unordered is not a legal ordering for cmpxchg.
return (AI->getSuccessOrdering() != AtomicOrdering::Monotonic ||
AI->getFailureOrdering() != AtomicOrdering::Monotonic);
}
AtomicOrdering Ordering;
switch (I->getOpcode()) {
case Instruction::AtomicRMW:
Ordering = cast<AtomicRMWInst>(I)->getOrdering();
break;
case Instruction::Store:
Ordering = cast<StoreInst>(I)->getOrdering();
break;
case Instruction::Load:
Ordering = cast<LoadInst>(I)->getOrdering();
break;
default:
llvm_unreachable(
"New atomic operations need to be known in the attributor.");
}
return (Ordering != AtomicOrdering::Unordered &&
Ordering != AtomicOrdering::Monotonic);
}
/// Return true if this intrinsic is nosync. This is only used for intrinsics
/// which would be nosync except that they have a volatile flag. All other
/// intrinsics are simply annotated with the nosync attribute in Intrinsics.td.
bool AANoSyncImpl::isNoSyncIntrinsic(Instruction *I) {
if (auto *MI = dyn_cast<MemIntrinsic>(I))
return !MI->isVolatile();
return false;
}
ChangeStatus AANoSyncImpl::updateImpl(Attributor &A) {
auto CheckRWInstForNoSync = [&](Instruction &I) {
/// We are looking for volatile instructions or Non-Relaxed atomics.
if (const auto *CB = dyn_cast<CallBase>(&I)) {
if (CB->hasFnAttr(Attribute::NoSync))
return true;
if (isNoSyncIntrinsic(&I))
return true;
const auto &NoSyncAA = A.getAAFor<AANoSync>(
*this, IRPosition::callsite_function(*CB), DepClassTy::REQUIRED);
return NoSyncAA.isAssumedNoSync();
}
if (!I.isVolatile() && !isNonRelaxedAtomic(&I))
return true;
return false;
};
auto CheckForNoSync = [&](Instruction &I) {
// At this point we handled all read/write effects and they are all
// nosync, so they can be skipped.
if (I.mayReadOrWriteMemory())
return true;
// non-convergent and readnone imply nosync.
return !cast<CallBase>(I).isConvergent();
};
if (!A.checkForAllReadWriteInstructions(CheckRWInstForNoSync, *this) ||
!A.checkForAllCallLikeInstructions(CheckForNoSync, *this))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
struct AANoSyncFunction final : public AANoSyncImpl {
AANoSyncFunction(const IRPosition &IRP, Attributor &A)
: AANoSyncImpl(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_FN_ATTR(nosync) }
};
/// NoSync attribute deduction for a call sites.
struct AANoSyncCallSite final : AANoSyncImpl {
AANoSyncCallSite(const IRPosition &IRP, Attributor &A)
: AANoSyncImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AANoSyncImpl::initialize(A);
Function *F = getAssociatedFunction();
if (!F || F->isDeclaration())
indicatePessimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
// TODO: Once we have call site specific value information we can provide
// call site specific liveness information and then it makes
// sense to specialize attributes for call sites arguments instead of
// redirecting requests to the callee argument.
Function *F = getAssociatedFunction();
const IRPosition &FnPos = IRPosition::function(*F);
auto &FnAA = A.getAAFor<AANoSync>(*this, FnPos, DepClassTy::REQUIRED);
return clampStateAndIndicateChange(getState(), FnAA.getState());
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_CS_ATTR(nosync); }
};
/// ------------------------ No-Free Attributes ----------------------------
struct AANoFreeImpl : public AANoFree {
AANoFreeImpl(const IRPosition &IRP, Attributor &A) : AANoFree(IRP, A) {}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
auto CheckForNoFree = [&](Instruction &I) {
const auto &CB = cast<CallBase>(I);
if (CB.hasFnAttr(Attribute::NoFree))
return true;
const auto &NoFreeAA = A.getAAFor<AANoFree>(
*this, IRPosition::callsite_function(CB), DepClassTy::REQUIRED);
return NoFreeAA.isAssumedNoFree();
};
if (!A.checkForAllCallLikeInstructions(CheckForNoFree, *this))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// See AbstractAttribute::getAsStr().
const std::string getAsStr() const override {
return getAssumed() ? "nofree" : "may-free";
}
};
struct AANoFreeFunction final : public AANoFreeImpl {
AANoFreeFunction(const IRPosition &IRP, Attributor &A)
: AANoFreeImpl(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_FN_ATTR(nofree) }
};
/// NoFree attribute deduction for a call sites.
struct AANoFreeCallSite final : AANoFreeImpl {
AANoFreeCallSite(const IRPosition &IRP, Attributor &A)
: AANoFreeImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AANoFreeImpl::initialize(A);
Function *F = getAssociatedFunction();
if (!F || F->isDeclaration())
indicatePessimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
// TODO: Once we have call site specific value information we can provide
// call site specific liveness information and then it makes
// sense to specialize attributes for call sites arguments instead of
// redirecting requests to the callee argument.
Function *F = getAssociatedFunction();
const IRPosition &FnPos = IRPosition::function(*F);
auto &FnAA = A.getAAFor<AANoFree>(*this, FnPos, DepClassTy::REQUIRED);
return clampStateAndIndicateChange(getState(), FnAA.getState());
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_CS_ATTR(nofree); }
};
/// NoFree attribute for floating values.
struct AANoFreeFloating : AANoFreeImpl {
AANoFreeFloating(const IRPosition &IRP, Attributor &A)
: AANoFreeImpl(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override{STATS_DECLTRACK_FLOATING_ATTR(nofree)}
/// See Abstract Attribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
const IRPosition &IRP = getIRPosition();
const auto &NoFreeAA = A.getAAFor<AANoFree>(
*this, IRPosition::function_scope(IRP), DepClassTy::OPTIONAL);
if (NoFreeAA.isAssumedNoFree())
return ChangeStatus::UNCHANGED;
Value &AssociatedValue = getIRPosition().getAssociatedValue();
auto Pred = [&](const Use &U, bool &Follow) -> bool {
Instruction *UserI = cast<Instruction>(U.getUser());
if (auto *CB = dyn_cast<CallBase>(UserI)) {
if (CB->isBundleOperand(&U))
return false;
if (!CB->isArgOperand(&U))
return true;
unsigned ArgNo = CB->getArgOperandNo(&U);
const auto &NoFreeArg = A.getAAFor<AANoFree>(
*this, IRPosition::callsite_argument(*CB, ArgNo),
DepClassTy::REQUIRED);
return NoFreeArg.isAssumedNoFree();
}
if (isa<GetElementPtrInst>(UserI) || isa<BitCastInst>(UserI) ||
isa<PHINode>(UserI) || isa<SelectInst>(UserI)) {
Follow = true;
return true;
}
if (isa<ReturnInst>(UserI))
return true;
// Unknown user.
return false;
};
if (!A.checkForAllUses(Pred, *this, AssociatedValue))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
};
/// NoFree attribute for a call site argument.
struct AANoFreeArgument final : AANoFreeFloating {
AANoFreeArgument(const IRPosition &IRP, Attributor &A)
: AANoFreeFloating(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_ARG_ATTR(nofree) }
};
/// NoFree attribute for call site arguments.
struct AANoFreeCallSiteArgument final : AANoFreeFloating {
AANoFreeCallSiteArgument(const IRPosition &IRP, Attributor &A)
: AANoFreeFloating(IRP, A) {}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
// TODO: Once we have call site specific value information we can provide
// call site specific liveness information and then it makes
// sense to specialize attributes for call sites arguments instead of
// redirecting requests to the callee argument.
Argument *Arg = getAssociatedArgument();
if (!Arg)
return indicatePessimisticFixpoint();
const IRPosition &ArgPos = IRPosition::argument(*Arg);
auto &ArgAA = A.getAAFor<AANoFree>(*this, ArgPos, DepClassTy::REQUIRED);
return clampStateAndIndicateChange(getState(), ArgAA.getState());
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override{STATS_DECLTRACK_CSARG_ATTR(nofree)};
};
/// NoFree attribute for function return value.
struct AANoFreeReturned final : AANoFreeFloating {
AANoFreeReturned(const IRPosition &IRP, Attributor &A)
: AANoFreeFloating(IRP, A) {
llvm_unreachable("NoFree is not applicable to function returns!");
}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
llvm_unreachable("NoFree is not applicable to function returns!");
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
llvm_unreachable("NoFree is not applicable to function returns!");
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {}
};
/// NoFree attribute deduction for a call site return value.
struct AANoFreeCallSiteReturned final : AANoFreeFloating {
AANoFreeCallSiteReturned(const IRPosition &IRP, Attributor &A)
: AANoFreeFloating(IRP, A) {}
ChangeStatus manifest(Attributor &A) override {
return ChangeStatus::UNCHANGED;
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_CSRET_ATTR(nofree) }
};
/// ------------------------ NonNull Argument Attribute ------------------------
static int64_t getKnownNonNullAndDerefBytesForUse(
Attributor &A, const AbstractAttribute &QueryingAA, Value &AssociatedValue,
const Use *U, const Instruction *I, bool &IsNonNull, bool &TrackUse) {
TrackUse = false;
const Value *UseV = U->get();
if (!UseV->getType()->isPointerTy())
return 0;
// We need to follow common pointer manipulation uses to the accesses they
// feed into. We can try to be smart to avoid looking through things we do not
// like for now, e.g., non-inbounds GEPs.
if (isa<CastInst>(I)) {
TrackUse = true;
return 0;
}
if (isa<GetElementPtrInst>(I)) {
TrackUse = true;
return 0;
}
Type *PtrTy = UseV->getType();
const Function *F = I->getFunction();
bool NullPointerIsDefined =
F ? llvm::NullPointerIsDefined(F, PtrTy->getPointerAddressSpace()) : true;
const DataLayout &DL = A.getInfoCache().getDL();
if (const auto *CB = dyn_cast<CallBase>(I)) {
if (CB->isBundleOperand(U)) {
if (RetainedKnowledge RK = getKnowledgeFromUse(
U, {Attribute::NonNull, Attribute::Dereferenceable})) {
IsNonNull |=
(RK.AttrKind == Attribute::NonNull || !NullPointerIsDefined);
return RK.ArgValue;
}
return 0;
}
if (CB->isCallee(U)) {
IsNonNull |= !NullPointerIsDefined;
return 0;
}
unsigned ArgNo = CB->getArgOperandNo(U);
IRPosition IRP = IRPosition::callsite_argument(*CB, ArgNo);
// As long as we only use known information there is no need to track
// dependences here.
auto &DerefAA =
A.getAAFor<AADereferenceable>(QueryingAA, IRP, DepClassTy::NONE);
IsNonNull |= DerefAA.isKnownNonNull();
return DerefAA.getKnownDereferenceableBytes();
}
int64_t Offset;
const Value *Base =
getMinimalBaseOfAccsesPointerOperand(A, QueryingAA, I, Offset, DL);
if (Base) {
if (Base == &AssociatedValue &&
getPointerOperand(I, /* AllowVolatile */ false) == UseV) {
int64_t DerefBytes =
(int64_t)DL.getTypeStoreSize(PtrTy->getPointerElementType()) + Offset;
IsNonNull |= !NullPointerIsDefined;
return std::max(int64_t(0), DerefBytes);
}
}
/// Corner case when an offset is 0.
Base = getBasePointerOfAccessPointerOperand(I, Offset, DL,
/*AllowNonInbounds*/ true);
if (Base) {
if (Offset == 0 && Base == &AssociatedValue &&
getPointerOperand(I, /* AllowVolatile */ false) == UseV) {
int64_t DerefBytes =
(int64_t)DL.getTypeStoreSize(PtrTy->getPointerElementType());
IsNonNull |= !NullPointerIsDefined;
return std::max(int64_t(0), DerefBytes);
}
}
return 0;
}
struct AANonNullImpl : AANonNull {
AANonNullImpl(const IRPosition &IRP, Attributor &A)
: AANonNull(IRP, A),
NullIsDefined(NullPointerIsDefined(
getAnchorScope(),
getAssociatedValue().getType()->getPointerAddressSpace())) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
Value &V = getAssociatedValue();
if (!NullIsDefined &&
hasAttr({Attribute::NonNull, Attribute::Dereferenceable},
/* IgnoreSubsumingPositions */ false, &A)) {
indicateOptimisticFixpoint();
return;
}
if (isa<ConstantPointerNull>(V)) {
indicatePessimisticFixpoint();
return;
}
AANonNull::initialize(A);
bool CanBeNull, CanBeFreed;
if (V.getPointerDereferenceableBytes(A.getDataLayout(), CanBeNull,
CanBeFreed)) {
if (!CanBeNull) {
indicateOptimisticFixpoint();
return;
}
}
if (isa<GlobalValue>(&getAssociatedValue())) {
indicatePessimisticFixpoint();
return;
}
if (Instruction *CtxI = getCtxI())
followUsesInMBEC(*this, A, getState(), *CtxI);
}
/// See followUsesInMBEC
bool followUseInMBEC(Attributor &A, const Use *U, const Instruction *I,
AANonNull::StateType &State) {
bool IsNonNull = false;
bool TrackUse = false;
getKnownNonNullAndDerefBytesForUse(A, *this, getAssociatedValue(), U, I,
IsNonNull, TrackUse);
State.setKnown(IsNonNull);
return TrackUse;
}
/// See AbstractAttribute::getAsStr().
const std::string getAsStr() const override {
return getAssumed() ? "nonnull" : "may-null";
}
/// Flag to determine if the underlying value can be null and still allow
/// valid accesses.
const bool NullIsDefined;
};
/// NonNull attribute for a floating value.
struct AANonNullFloating : public AANonNullImpl {
AANonNullFloating(const IRPosition &IRP, Attributor &A)
: AANonNullImpl(IRP, A) {}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
const DataLayout &DL = A.getDataLayout();
DominatorTree *DT = nullptr;
AssumptionCache *AC = nullptr;
InformationCache &InfoCache = A.getInfoCache();
if (const Function *Fn = getAnchorScope()) {
DT = InfoCache.getAnalysisResultForFunction<DominatorTreeAnalysis>(*Fn);
AC = InfoCache.getAnalysisResultForFunction<AssumptionAnalysis>(*Fn);
}
auto VisitValueCB = [&](Value &V, const Instruction *CtxI,
AANonNull::StateType &T, bool Stripped) -> bool {
const auto &AA = A.getAAFor<AANonNull>(*this, IRPosition::value(V),
DepClassTy::REQUIRED);
if (!Stripped && this == &AA) {
if (!isKnownNonZero(&V, DL, 0, AC, CtxI, DT))
T.indicatePessimisticFixpoint();
} else {
// Use abstract attribute information.
const AANonNull::StateType &NS = AA.getState();
T ^= NS;
}
return T.isValidState();
};
StateType T;
if (!genericValueTraversal<AANonNull, StateType>(
A, getIRPosition(), *this, T, VisitValueCB, getCtxI()))
return indicatePessimisticFixpoint();
return clampStateAndIndicateChange(getState(), T);
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_FNRET_ATTR(nonnull) }
};
/// NonNull attribute for function return value.
struct AANonNullReturned final
: AAReturnedFromReturnedValues<AANonNull, AANonNull> {
AANonNullReturned(const IRPosition &IRP, Attributor &A)
: AAReturnedFromReturnedValues<AANonNull, AANonNull>(IRP, A) {}
/// See AbstractAttribute::getAsStr().
const std::string getAsStr() const override {
return getAssumed() ? "nonnull" : "may-null";
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_FNRET_ATTR(nonnull) }
};
/// NonNull attribute for function argument.
struct AANonNullArgument final
: AAArgumentFromCallSiteArguments<AANonNull, AANonNullImpl> {
AANonNullArgument(const IRPosition &IRP, Attributor &A)
: AAArgumentFromCallSiteArguments<AANonNull, AANonNullImpl>(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_ARG_ATTR(nonnull) }
};
struct AANonNullCallSiteArgument final : AANonNullFloating {
AANonNullCallSiteArgument(const IRPosition &IRP, Attributor &A)
: AANonNullFloating(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_CSARG_ATTR(nonnull) }
};
/// NonNull attribute for a call site return position.
struct AANonNullCallSiteReturned final
: AACallSiteReturnedFromReturned<AANonNull, AANonNullImpl> {
AANonNullCallSiteReturned(const IRPosition &IRP, Attributor &A)
: AACallSiteReturnedFromReturned<AANonNull, AANonNullImpl>(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_CSRET_ATTR(nonnull) }
};
/// ------------------------ No-Recurse Attributes ----------------------------
struct AANoRecurseImpl : public AANoRecurse {
AANoRecurseImpl(const IRPosition &IRP, Attributor &A) : AANoRecurse(IRP, A) {}
/// See AbstractAttribute::getAsStr()
const std::string getAsStr() const override {
return getAssumed() ? "norecurse" : "may-recurse";
}
};
struct AANoRecurseFunction final : AANoRecurseImpl {
AANoRecurseFunction(const IRPosition &IRP, Attributor &A)
: AANoRecurseImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AANoRecurseImpl::initialize(A);
if (const Function *F = getAnchorScope())
if (A.getInfoCache().getSccSize(*F) != 1)
indicatePessimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
// If all live call sites are known to be no-recurse, we are as well.
auto CallSitePred = [&](AbstractCallSite ACS) {
const auto &NoRecurseAA = A.getAAFor<AANoRecurse>(
*this, IRPosition::function(*ACS.getInstruction()->getFunction()),
DepClassTy::NONE);
return NoRecurseAA.isKnownNoRecurse();
};
bool AllCallSitesKnown;
if (A.checkForAllCallSites(CallSitePred, *this, true, AllCallSitesKnown)) {
// If we know all call sites and all are known no-recurse, we are done.
// If all known call sites, which might not be all that exist, are known
// to be no-recurse, we are not done but we can continue to assume
// no-recurse. If one of the call sites we have not visited will become
// live, another update is triggered.
if (AllCallSitesKnown)
indicateOptimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
// If the above check does not hold anymore we look at the calls.
auto CheckForNoRecurse = [&](Instruction &I) {
const auto &CB = cast<CallBase>(I);
if (CB.hasFnAttr(Attribute::NoRecurse))
return true;
const auto &NoRecurseAA = A.getAAFor<AANoRecurse>(
*this, IRPosition::callsite_function(CB), DepClassTy::REQUIRED);
if (!NoRecurseAA.isAssumedNoRecurse())
return false;
// Recursion to the same function
if (CB.getCalledFunction() == getAnchorScope())
return false;
return true;
};
if (!A.checkForAllCallLikeInstructions(CheckForNoRecurse, *this))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
void trackStatistics() const override { STATS_DECLTRACK_FN_ATTR(norecurse) }
};
/// NoRecurse attribute deduction for a call sites.
struct AANoRecurseCallSite final : AANoRecurseImpl {
AANoRecurseCallSite(const IRPosition &IRP, Attributor &A)
: AANoRecurseImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AANoRecurseImpl::initialize(A);
Function *F = getAssociatedFunction();
if (!F || F->isDeclaration())
indicatePessimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
// TODO: Once we have call site specific value information we can provide
// call site specific liveness information and then it makes
// sense to specialize attributes for call sites arguments instead of
// redirecting requests to the callee argument.
Function *F = getAssociatedFunction();
const IRPosition &FnPos = IRPosition::function(*F);
auto &FnAA = A.getAAFor<AANoRecurse>(*this, FnPos, DepClassTy::REQUIRED);
return clampStateAndIndicateChange(getState(), FnAA.getState());
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_CS_ATTR(norecurse); }
};
/// -------------------- Undefined-Behavior Attributes ------------------------
struct AAUndefinedBehaviorImpl : public AAUndefinedBehavior {
AAUndefinedBehaviorImpl(const IRPosition &IRP, Attributor &A)
: AAUndefinedBehavior(IRP, A) {}
/// See AbstractAttribute::updateImpl(...).
// through a pointer (i.e. also branches etc.)
ChangeStatus updateImpl(Attributor &A) override {
const size_t UBPrevSize = KnownUBInsts.size();
const size_t NoUBPrevSize = AssumedNoUBInsts.size();
auto InspectMemAccessInstForUB = [&](Instruction &I) {
// Skip instructions that are already saved.
if (AssumedNoUBInsts.count(&I) || KnownUBInsts.count(&I))
return true;
// If we reach here, we know we have an instruction
// that accesses memory through a pointer operand,
// for which getPointerOperand() should give it to us.
const Value *PtrOp = getPointerOperand(&I, /* AllowVolatile */ true);
assert(PtrOp &&
"Expected pointer operand of memory accessing instruction");
// Either we stopped and the appropriate action was taken,
// or we got back a simplified value to continue.
Optional<Value *> SimplifiedPtrOp = stopOnUndefOrAssumed(A, PtrOp, &I);
if (!SimplifiedPtrOp.hasValue())
return true;
const Value *PtrOpVal = SimplifiedPtrOp.getValue();
// A memory access through a pointer is considered UB
// only if the pointer has constant null value.
// TODO: Expand it to not only check constant values.
if (!isa<ConstantPointerNull>(PtrOpVal)) {
AssumedNoUBInsts.insert(&I);
return true;
}
const Type *PtrTy = PtrOpVal->getType();
// Because we only consider instructions inside functions,
// assume that a parent function exists.
const Function *F = I.getFunction();
// A memory access using constant null pointer is only considered UB
// if null pointer is _not_ defined for the target platform.
if (llvm::NullPointerIsDefined(F, PtrTy->getPointerAddressSpace()))
AssumedNoUBInsts.insert(&I);
else
KnownUBInsts.insert(&I);
return true;
};
auto InspectBrInstForUB = [&](Instruction &I) {
// A conditional branch instruction is considered UB if it has `undef`
// condition.
// Skip instructions that are already saved.
if (AssumedNoUBInsts.count(&I) || KnownUBInsts.count(&I))
return true;
// We know we have a branch instruction.
auto BrInst = cast<BranchInst>(&I);
// Unconditional branches are never considered UB.
if (BrInst->isUnconditional())
return true;
// Either we stopped and the appropriate action was taken,
// or we got back a simplified value to continue.
Optional<Value *> SimplifiedCond =
stopOnUndefOrAssumed(A, BrInst->getCondition(), BrInst);
if (!SimplifiedCond.hasValue())
return true;
AssumedNoUBInsts.insert(&I);
return true;
};
auto InspectCallSiteForUB = [&](Instruction &I) {
// Check whether a callsite always cause UB or not
// Skip instructions that are already saved.
if (AssumedNoUBInsts.count(&I) || KnownUBInsts.count(&I))
return true;
// Check nonnull and noundef argument attribute violation for each
// callsite.
CallBase &CB = cast<CallBase>(I);
Function *Callee = CB.getCalledFunction();
if (!Callee)
return true;
for (unsigned idx = 0; idx < CB.getNumArgOperands(); idx++) {
// If current argument is known to be simplified to null pointer and the
// corresponding argument position is known to have nonnull attribute,
// the argument is poison. Furthermore, if the argument is poison and
// the position is known to have noundef attriubte, this callsite is
// considered UB.
if (idx >= Callee->arg_size())
break;
Value *ArgVal = CB.getArgOperand(idx);
if (!ArgVal)
continue;
// Here, we handle three cases.
// (1) Not having a value means it is dead. (we can replace the value
// with undef)
// (2) Simplified to undef. The argument violate noundef attriubte.
// (3) Simplified to null pointer where known to be nonnull.
// The argument is a poison value and violate noundef attribute.
IRPosition CalleeArgumentIRP = IRPosition::callsite_argument(CB, idx);
auto &NoUndefAA =
A.getAAFor<AANoUndef>(*this, CalleeArgumentIRP, DepClassTy::NONE);
if (!NoUndefAA.isKnownNoUndef())
continue;
auto &ValueSimplifyAA = A.getAAFor<AAValueSimplify>(
*this, IRPosition::value(*ArgVal), DepClassTy::NONE);
if (!ValueSimplifyAA.isKnown())
continue;
Optional<Value *> SimplifiedVal =
ValueSimplifyAA.getAssumedSimplifiedValue(A);
if (!SimplifiedVal.hasValue() ||
isa<UndefValue>(*SimplifiedVal.getValue())) {
KnownUBInsts.insert(&I);
continue;
}
if (!ArgVal->getType()->isPointerTy() ||
!isa<ConstantPointerNull>(*SimplifiedVal.getValue()))
continue;
auto &NonNullAA =
A.getAAFor<AANonNull>(*this, CalleeArgumentIRP, DepClassTy::NONE);
if (NonNullAA.isKnownNonNull())
KnownUBInsts.insert(&I);
}
return true;
};
auto InspectReturnInstForUB =
[&](Value &V, const SmallSetVector<ReturnInst *, 4> RetInsts) {
// Check if a return instruction always cause UB or not
// Note: It is guaranteed that the returned position of the anchor
// scope has noundef attribute when this is called.
// We also ensure the return position is not "assumed dead"
// because the returned value was then potentially simplified to
// `undef` in AAReturnedValues without removing the `noundef`
// attribute yet.
// When the returned position has noundef attriubte, UB occur in the
// following cases.
// (1) Returned value is known to be undef.
// (2) The value is known to be a null pointer and the returned
// position has nonnull attribute (because the returned value is
// poison).
bool FoundUB = false;
if (isa<UndefValue>(V)) {
FoundUB = true;
} else {
if (isa<ConstantPointerNull>(V)) {
auto &NonNullAA = A.getAAFor<AANonNull>(
*this, IRPosition::returned(*getAnchorScope()),
DepClassTy::NONE);
if (NonNullAA.isKnownNonNull())
FoundUB = true;
}
}
if (FoundUB)
for (ReturnInst *RI : RetInsts)
KnownUBInsts.insert(RI);
return true;
};
A.checkForAllInstructions(InspectMemAccessInstForUB, *this,
{Instruction::Load, Instruction::Store,
Instruction::AtomicCmpXchg,
Instruction::AtomicRMW},
/* CheckBBLivenessOnly */ true);
A.checkForAllInstructions(InspectBrInstForUB, *this, {Instruction::Br},
/* CheckBBLivenessOnly */ true);
A.checkForAllCallLikeInstructions(InspectCallSiteForUB, *this);
// If the returned position of the anchor scope has noundef attriubte, check
// all returned instructions.
if (!getAnchorScope()->getReturnType()->isVoidTy()) {
const IRPosition &ReturnIRP = IRPosition::returned(*getAnchorScope());
if (!A.isAssumedDead(ReturnIRP, this, nullptr)) {
auto &RetPosNoUndefAA =
A.getAAFor<AANoUndef>(*this, ReturnIRP, DepClassTy::NONE);
if (RetPosNoUndefAA.isKnownNoUndef())
A.checkForAllReturnedValuesAndReturnInsts(InspectReturnInstForUB,
*this);
}
}
if (NoUBPrevSize != AssumedNoUBInsts.size() ||
UBPrevSize != KnownUBInsts.size())
return ChangeStatus::CHANGED;
return ChangeStatus::UNCHANGED;
}
bool isKnownToCauseUB(Instruction *I) const override {
return KnownUBInsts.count(I);
}
bool isAssumedToCauseUB(Instruction *I) const override {
// In simple words, if an instruction is not in the assumed to _not_
// cause UB, then it is assumed UB (that includes those
// in the KnownUBInsts set). The rest is boilerplate
// is to ensure that it is one of the instructions we test
// for UB.
switch (I->getOpcode()) {
case Instruction::Load:
case Instruction::Store:
case Instruction::AtomicCmpXchg:
case Instruction::AtomicRMW:
return !AssumedNoUBInsts.count(I);
case Instruction::Br: {
auto BrInst = cast<BranchInst>(I);
if (BrInst->isUnconditional())
return false;
return !AssumedNoUBInsts.count(I);
} break;
default:
return false;
}
return false;
}
ChangeStatus manifest(Attributor &A) override {
if (KnownUBInsts.empty())
return ChangeStatus::UNCHANGED;
for (Instruction *I : KnownUBInsts)
A.changeToUnreachableAfterManifest(I);
return ChangeStatus::CHANGED;
}
/// See AbstractAttribute::getAsStr()
const std::string getAsStr() const override {
return getAssumed() ? "undefined-behavior" : "no-ub";
}
/// Note: The correctness of this analysis depends on the fact that the
/// following 2 sets will stop changing after some point.
/// "Change" here means that their size changes.
/// The size of each set is monotonically increasing
/// (we only add items to them) and it is upper bounded by the number of
/// instructions in the processed function (we can never save more
/// elements in either set than this number). Hence, at some point,
/// they will stop increasing.
/// Consequently, at some point, both sets will have stopped
/// changing, effectively making the analysis reach a fixpoint.
/// Note: These 2 sets are disjoint and an instruction can be considered
/// one of 3 things:
/// 1) Known to cause UB (AAUndefinedBehavior could prove it) and put it in
/// the KnownUBInsts set.
/// 2) Assumed to cause UB (in every updateImpl, AAUndefinedBehavior
/// has a reason to assume it).
/// 3) Assumed to not cause UB. very other instruction - AAUndefinedBehavior
/// could not find a reason to assume or prove that it can cause UB,
/// hence it assumes it doesn't. We have a set for these instructions
/// so that we don't reprocess them in every update.
/// Note however that instructions in this set may cause UB.
protected:
/// A set of all live instructions _known_ to cause UB.
SmallPtrSet<Instruction *, 8> KnownUBInsts;
private:
/// A set of all the (live) instructions that are assumed to _not_ cause UB.
SmallPtrSet<Instruction *, 8> AssumedNoUBInsts;
// Should be called on updates in which if we're processing an instruction
// \p I that depends on a value \p V, one of the following has to happen:
// - If the value is assumed, then stop.
// - If the value is known but undef, then consider it UB.
// - Otherwise, do specific processing with the simplified value.
// We return None in the first 2 cases to signify that an appropriate
// action was taken and the caller should stop.
// Otherwise, we return the simplified value that the caller should
// use for specific processing.
Optional<Value *> stopOnUndefOrAssumed(Attributor &A, const Value *V,
Instruction *I) {
const auto &ValueSimplifyAA = A.getAAFor<AAValueSimplify>(
*this, IRPosition::value(*V), DepClassTy::REQUIRED);
Optional<Value *> SimplifiedV =
ValueSimplifyAA.getAssumedSimplifiedValue(A);
if (!ValueSimplifyAA.isKnown()) {
// Don't depend on assumed values.
return llvm::None;
}
if (!SimplifiedV.hasValue()) {
// If it is known (which we tested above) but it doesn't have a value,
// then we can assume `undef` and hence the instruction is UB.
KnownUBInsts.insert(I);
return llvm::None;
}
Value *Val = SimplifiedV.getValue();
if (isa<UndefValue>(Val)) {
KnownUBInsts.insert(I);
return llvm::None;
}
return Val;
}
};
struct AAUndefinedBehaviorFunction final : AAUndefinedBehaviorImpl {
AAUndefinedBehaviorFunction(const IRPosition &IRP, Attributor &A)
: AAUndefinedBehaviorImpl(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL(UndefinedBehaviorInstruction, Instruction,
"Number of instructions known to have UB");
BUILD_STAT_NAME(UndefinedBehaviorInstruction, Instruction) +=
KnownUBInsts.size();
}
};
/// ------------------------ Will-Return Attributes ----------------------------
// Helper function that checks whether a function has any cycle which we don't
// know if it is bounded or not.
// Loops with maximum trip count are considered bounded, any other cycle not.
static bool mayContainUnboundedCycle(Function &F, Attributor &A) {
ScalarEvolution *SE =
A.getInfoCache().getAnalysisResultForFunction<ScalarEvolutionAnalysis>(F);
LoopInfo *LI = A.getInfoCache().getAnalysisResultForFunction<LoopAnalysis>(F);
// If either SCEV or LoopInfo is not available for the function then we assume
// any cycle to be unbounded cycle.
// We use scc_iterator which uses Tarjan algorithm to find all the maximal
// SCCs.To detect if there's a cycle, we only need to find the maximal ones.
if (!SE || !LI) {
for (scc_iterator<Function *> SCCI = scc_begin(&F); !SCCI.isAtEnd(); ++SCCI)
if (SCCI.hasCycle())
return true;
return false;
}
// If there's irreducible control, the function may contain non-loop cycles.
if (mayContainIrreducibleControl(F, LI))
return true;
// Any loop that does not have a max trip count is considered unbounded cycle.
for (auto *L : LI->getLoopsInPreorder()) {
if (!SE->getSmallConstantMaxTripCount(L))
return true;
}
return false;
}
struct AAWillReturnImpl : public AAWillReturn {
AAWillReturnImpl(const IRPosition &IRP, Attributor &A)
: AAWillReturn(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AAWillReturn::initialize(A);
if (isImpliedByMustprogressAndReadonly(A, /* KnownOnly */ true)) {
indicateOptimisticFixpoint();
return;
}
}
/// Check for `mustprogress` and `readonly` as they imply `willreturn`.
bool isImpliedByMustprogressAndReadonly(Attributor &A, bool KnownOnly) {
// Check for `mustprogress` in the scope and the associated function which
// might be different if this is a call site.
if ((!getAnchorScope() || !getAnchorScope()->mustProgress()) &&
(!getAssociatedFunction() || !getAssociatedFunction()->mustProgress()))
return false;
const auto &MemAA = A.getAAFor<AAMemoryBehavior>(*this, getIRPosition(),
DepClassTy::NONE);
if (!MemAA.isAssumedReadOnly())
return false;
if (KnownOnly && !MemAA.isKnownReadOnly())
return false;
if (!MemAA.isKnownReadOnly())
A.recordDependence(MemAA, *this, DepClassTy::OPTIONAL);
return true;
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
if (isImpliedByMustprogressAndReadonly(A, /* KnownOnly */ false))
return ChangeStatus::UNCHANGED;
auto CheckForWillReturn = [&](Instruction &I) {
IRPosition IPos = IRPosition::callsite_function(cast<CallBase>(I));
const auto &WillReturnAA =
A.getAAFor<AAWillReturn>(*this, IPos, DepClassTy::REQUIRED);
if (WillReturnAA.isKnownWillReturn())
return true;
if (!WillReturnAA.isAssumedWillReturn())
return false;
const auto &NoRecurseAA =
A.getAAFor<AANoRecurse>(*this, IPos, DepClassTy::REQUIRED);
return NoRecurseAA.isAssumedNoRecurse();
};
if (!A.checkForAllCallLikeInstructions(CheckForWillReturn, *this))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// See AbstractAttribute::getAsStr()
const std::string getAsStr() const override {
return getAssumed() ? "willreturn" : "may-noreturn";
}
};
struct AAWillReturnFunction final : AAWillReturnImpl {
AAWillReturnFunction(const IRPosition &IRP, Attributor &A)
: AAWillReturnImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AAWillReturnImpl::initialize(A);
Function *F = getAnchorScope();
if (!F || F->isDeclaration() || mayContainUnboundedCycle(*F, A))
indicatePessimisticFixpoint();
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_FN_ATTR(willreturn) }
};
/// WillReturn attribute deduction for a call sites.
struct AAWillReturnCallSite final : AAWillReturnImpl {
AAWillReturnCallSite(const IRPosition &IRP, Attributor &A)
: AAWillReturnImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AAWillReturnImpl::initialize(A);
Function *F = getAssociatedFunction();
if (!F || !A.isFunctionIPOAmendable(*F))
indicatePessimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
if (isImpliedByMustprogressAndReadonly(A, /* KnownOnly */ false))
return ChangeStatus::UNCHANGED;
// TODO: Once we have call site specific value information we can provide
// call site specific liveness information and then it makes
// sense to specialize attributes for call sites arguments instead of
// redirecting requests to the callee argument.
Function *F = getAssociatedFunction();
const IRPosition &FnPos = IRPosition::function(*F);
auto &FnAA = A.getAAFor<AAWillReturn>(*this, FnPos, DepClassTy::REQUIRED);
return clampStateAndIndicateChange(getState(), FnAA.getState());
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_CS_ATTR(willreturn); }
};
/// -------------------AAReachability Attribute--------------------------
struct AAReachabilityImpl : AAReachability {
AAReachabilityImpl(const IRPosition &IRP, Attributor &A)
: AAReachability(IRP, A) {}
const std::string getAsStr() const override {
// TODO: Return the number of reachable queries.
return "reachable";
}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override { indicatePessimisticFixpoint(); }
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
return indicatePessimisticFixpoint();
}
};
struct AAReachabilityFunction final : public AAReachabilityImpl {
AAReachabilityFunction(const IRPosition &IRP, Attributor &A)
: AAReachabilityImpl(IRP, A) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_FN_ATTR(reachable); }
};
/// ------------------------ NoAlias Argument Attribute ------------------------
struct AANoAliasImpl : AANoAlias {
AANoAliasImpl(const IRPosition &IRP, Attributor &A) : AANoAlias(IRP, A) {
assert(getAssociatedType()->isPointerTy() &&
"Noalias is a pointer attribute");
}
const std::string getAsStr() const override {
return getAssumed() ? "noalias" : "may-alias";
}
};
/// NoAlias attribute for a floating value.
struct AANoAliasFloating final : AANoAliasImpl {
AANoAliasFloating(const IRPosition &IRP, Attributor &A)
: AANoAliasImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AANoAliasImpl::initialize(A);
Value *Val = &getAssociatedValue();
do {
CastInst *CI = dyn_cast<CastInst>(Val);
if (!CI)
break;
Value *Base = CI->getOperand(0);
if (!Base->hasOneUse())
break;
Val = Base;
} while (true);
if (!Val->getType()->isPointerTy()) {
indicatePessimisticFixpoint();
return;
}
if (isa<AllocaInst>(Val))
indicateOptimisticFixpoint();
else if (isa<ConstantPointerNull>(Val) &&
!NullPointerIsDefined(getAnchorScope(),
Val->getType()->getPointerAddressSpace()))
indicateOptimisticFixpoint();
else if (Val != &getAssociatedValue()) {
const auto &ValNoAliasAA = A.getAAFor<AANoAlias>(
*this, IRPosition::value(*Val), DepClassTy::OPTIONAL);
if (ValNoAliasAA.isKnownNoAlias())
indicateOptimisticFixpoint();
}
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
// TODO: Implement this.
return indicatePessimisticFixpoint();
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECLTRACK_FLOATING_ATTR(noalias)
}
};
/// NoAlias attribute for an argument.
struct AANoAliasArgument final
: AAArgumentFromCallSiteArguments<AANoAlias, AANoAliasImpl> {
using Base = AAArgumentFromCallSiteArguments<AANoAlias, AANoAliasImpl>;
AANoAliasArgument(const IRPosition &IRP, Attributor &A) : Base(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
Base::initialize(A);
// See callsite argument attribute and callee argument attribute.
if (hasAttr({Attribute::ByVal}))
indicateOptimisticFixpoint();
}
/// See AbstractAttribute::update(...).
ChangeStatus updateImpl(Attributor &A) override {
// We have to make sure no-alias on the argument does not break
// synchronization when this is a callback argument, see also [1] below.
// If synchronization cannot be affected, we delegate to the base updateImpl
// function, otherwise we give up for now.
// If the function is no-sync, no-alias cannot break synchronization.
const auto &NoSyncAA =
A.getAAFor<AANoSync>(*this, IRPosition::function_scope(getIRPosition()),
DepClassTy::OPTIONAL);
if (NoSyncAA.isAssumedNoSync())
return Base::updateImpl(A);
// If the argument is read-only, no-alias cannot break synchronization.
const auto &MemBehaviorAA = A.getAAFor<AAMemoryBehavior>(
*this, getIRPosition(), DepClassTy::OPTIONAL);
if (MemBehaviorAA.isAssumedReadOnly())
return Base::updateImpl(A);
// If the argument is never passed through callbacks, no-alias cannot break
// synchronization.
bool AllCallSitesKnown;
if (A.checkForAllCallSites(
[](AbstractCallSite ACS) { return !ACS.isCallbackCall(); }, *this,
true, AllCallSitesKnown))
return Base::updateImpl(A);
// TODO: add no-alias but make sure it doesn't break synchronization by
// introducing fake uses. See:
// [1] Compiler Optimizations for OpenMP, J. Doerfert and H. Finkel,
// International Workshop on OpenMP 2018,
// http://compilers.cs.uni-saarland.de/people/doerfert/par_opt18.pdf
return indicatePessimisticFixpoint();
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_ARG_ATTR(noalias) }
};
struct AANoAliasCallSiteArgument final : AANoAliasImpl {
AANoAliasCallSiteArgument(const IRPosition &IRP, Attributor &A)
: AANoAliasImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
// See callsite argument attribute and callee argument attribute.
const auto &CB = cast<CallBase>(getAnchorValue());
if (CB.paramHasAttr(getCallSiteArgNo(), Attribute::NoAlias))
indicateOptimisticFixpoint();
Value &Val = getAssociatedValue();
if (isa<ConstantPointerNull>(Val) &&
!NullPointerIsDefined(getAnchorScope(),
Val.getType()->getPointerAddressSpace()))
indicateOptimisticFixpoint();
}
/// Determine if the underlying value may alias with the call site argument
/// \p OtherArgNo of \p ICS (= the underlying call site).
bool mayAliasWithArgument(Attributor &A, AAResults *&AAR,
const AAMemoryBehavior &MemBehaviorAA,
const CallBase &CB, unsigned OtherArgNo) {
// We do not need to worry about aliasing with the underlying IRP.
if (this->getCalleeArgNo() == (int)OtherArgNo)
return false;
// If it is not a pointer or pointer vector we do not alias.
const Value *ArgOp = CB.getArgOperand(OtherArgNo);
if (!ArgOp->getType()->isPtrOrPtrVectorTy())
return false;
auto &CBArgMemBehaviorAA = A.getAAFor<AAMemoryBehavior>(
*this, IRPosition::callsite_argument(CB, OtherArgNo), DepClassTy::NONE);
// If the argument is readnone, there is no read-write aliasing.
if (CBArgMemBehaviorAA.isAssumedReadNone()) {
A.recordDependence(CBArgMemBehaviorAA, *this, DepClassTy::OPTIONAL);
return false;
}
// If the argument is readonly and the underlying value is readonly, there
// is no read-write aliasing.
bool IsReadOnly = MemBehaviorAA.isAssumedReadOnly();
if (CBArgMemBehaviorAA.isAssumedReadOnly() && IsReadOnly) {
A.recordDependence(MemBehaviorAA, *this, DepClassTy::OPTIONAL);
A.recordDependence(CBArgMemBehaviorAA, *this, DepClassTy::OPTIONAL);
return false;
}
// We have to utilize actual alias analysis queries so we need the object.
if (!AAR)
AAR = A.getInfoCache().getAAResultsForFunction(*getAnchorScope());
// Try to rule it out at the call site.
bool IsAliasing = !AAR || !AAR->isNoAlias(&getAssociatedValue(), ArgOp);
LLVM_DEBUG(dbgs() << "[NoAliasCSArg] Check alias between "
"callsite arguments: "
<< getAssociatedValue() << " " << *ArgOp << " => "
<< (IsAliasing ? "" : "no-") << "alias \n");
return IsAliasing;
}
bool
isKnownNoAliasDueToNoAliasPreservation(Attributor &A, AAResults *&AAR,
const AAMemoryBehavior &MemBehaviorAA,
const AANoAlias &NoAliasAA) {
// We can deduce "noalias" if the following conditions hold.
// (i) Associated value is assumed to be noalias in the definition.
// (ii) Associated value is assumed to be no-capture in all the uses
// possibly executed before this callsite.
// (iii) There is no other pointer argument which could alias with the
// value.
bool AssociatedValueIsNoAliasAtDef = NoAliasAA.isAssumedNoAlias();
if (!AssociatedValueIsNoAliasAtDef) {
LLVM_DEBUG(dbgs() << "[AANoAlias] " << getAssociatedValue()
<< " is not no-alias at the definition\n");
return false;
}
A.recordDependence(NoAliasAA, *this, DepClassTy::OPTIONAL);
const IRPosition &VIRP = IRPosition::value(getAssociatedValue());
const Function *ScopeFn = VIRP.getAnchorScope();
auto &NoCaptureAA = A.getAAFor<AANoCapture>(*this, VIRP, DepClassTy::NONE);
// Check whether the value is captured in the scope using AANoCapture.
// Look at CFG and check only uses possibly executed before this
// callsite.
auto UsePred = [&](const Use &U, bool &Follow) -> bool {
Instruction *UserI = cast<Instruction>(U.getUser());
// If UserI is the curr instruction and there is a single potential use of
// the value in UserI we allow the use.
// TODO: We should inspect the operands and allow those that cannot alias
// with the value.
if (UserI == getCtxI() && UserI->getNumOperands() == 1)
return true;
if (ScopeFn) {
const auto &ReachabilityAA = A.getAAFor<AAReachability>(
*this, IRPosition::function(*ScopeFn), DepClassTy::OPTIONAL);
if (!ReachabilityAA.isAssumedReachable(A, *UserI, *getCtxI()))
return true;
if (auto *CB = dyn_cast<CallBase>(UserI)) {
if (CB->isArgOperand(&U)) {
unsigned ArgNo = CB->getArgOperandNo(&U);
const auto &NoCaptureAA = A.getAAFor<AANoCapture>(
*this, IRPosition::callsite_argument(*CB, ArgNo),
DepClassTy::OPTIONAL);
if (NoCaptureAA.isAssumedNoCapture())
return true;
}
}
}
// For cases which can potentially have more users
if (isa<GetElementPtrInst>(U) || isa<BitCastInst>(U) || isa<PHINode>(U) ||
isa<SelectInst>(U)) {
Follow = true;
return true;
}
LLVM_DEBUG(dbgs() << "[AANoAliasCSArg] Unknown user: " << *U << "\n");
return false;
};
if (!NoCaptureAA.isAssumedNoCaptureMaybeReturned()) {
if (!A.checkForAllUses(UsePred, *this, getAssociatedValue())) {
LLVM_DEBUG(
dbgs() << "[AANoAliasCSArg] " << getAssociatedValue()
<< " cannot be noalias as it is potentially captured\n");
return false;
}
}
A.recordDependence(NoCaptureAA, *this, DepClassTy::OPTIONAL);
// Check there is no other pointer argument which could alias with the
// value passed at this call site.
// TODO: AbstractCallSite
const auto &CB = cast<CallBase>(getAnchorValue());
for (unsigned OtherArgNo = 0; OtherArgNo < CB.getNumArgOperands();
OtherArgNo++)
if (mayAliasWithArgument(A, AAR, MemBehaviorAA, CB, OtherArgNo))
return false;
return true;
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override {
// If the argument is readnone we are done as there are no accesses via the
// argument.
auto &MemBehaviorAA =
A.getAAFor<AAMemoryBehavior>(*this, getIRPosition(), DepClassTy::NONE);
if (MemBehaviorAA.isAssumedReadNone()) {
A.recordDependence(MemBehaviorAA, *this, DepClassTy::OPTIONAL);
return ChangeStatus::UNCHANGED;
}
const IRPosition &VIRP = IRPosition::value(getAssociatedValue());
const auto &NoAliasAA =
A.getAAFor<AANoAlias>(*this, VIRP, DepClassTy::NONE);
AAResults *AAR = nullptr;
if (isKnownNoAliasDueToNoAliasPreservation(A, AAR, MemBehaviorAA,
NoAliasAA)) {
LLVM_DEBUG(
dbgs() << "[AANoAlias] No-Alias deduced via no-alias preservation\n");
return ChangeStatus::UNCHANGED;
}
return indicatePessimisticFixpoint();
}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECLTRACK_CSARG_ATTR(noalias) }
};
/// NoAlias attribute for function return value.
struct AANoAliasReturned final : AANoAliasImpl {
AANoAliasReturned(const IRPosition &IRP, Attributor &A)
: AANoAliasImpl(IRP, A) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
AANoAliasImpl::initialize(A);
Function *F = getAssociatedFunction();