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26e58466de
llvm-capstone/llvm/lib/Transforms/IPO/Attributor.cpp
Johannes Doerfert 26e58466de [Attributor] Use the cached data layout directly 
This removes the warning by using the new DL member.
It also simplifies the code.

llvm-svn: 368625
2019-08-12 22:21:09 +00:00

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//===- Attributor.cpp - Module-wide attribute 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
//
//===----------------------------------------------------------------------===//
//
// This file implements an inter procedural pass that deduces and/or propagating
// attributes. This is done in an abstract interpretation style fixpoint
// iteration. 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/DepthFirstIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/CaptureTracking.h"
#include "llvm/Analysis/EHPersonalities.h"
#include "llvm/Analysis/GlobalsModRef.h"
#include "llvm/Analysis/Loads.h"
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/IR/Argument.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/Local.h"
#include <cassert>
using namespace llvm;
#define DEBUG_TYPE "attributor"
STATISTIC(NumFnWithExactDefinition,
"Number of function with exact definitions");
STATISTIC(NumFnWithoutExactDefinition,
"Number of function without exact definitions");
STATISTIC(NumAttributesTimedOut,
"Number of abstract attributes timed out before fixpoint");
STATISTIC(NumAttributesValidFixpoint,
"Number of abstract attributes in a valid fixpoint state");
STATISTIC(NumAttributesManifested,
"Number of abstract attributes manifested in IR");
// 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_DECL_AND_TRACK_********* macro,
// e.g.,:
// void trackStatistics() const override {
// STATS_DECL_AND_TRACK_ARG_ATTR(returned)
// }
// If there is a single "increment" side one can use the macro
// STATS_DECL_AND_TRACK with a custom message. If there are multiple increment
// sides, STATS_DECL and STATS_TRACK can also be used separatly.
//
#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, TYPE, MSG) STATISTIC(BUILD_STAT_NAME(NAME, TYPE), MSG);
#define STATS_TRACK(NAME, TYPE) ++(BUILD_STAT_NAME(NAME, TYPE));
#define STATS_DECL_AND_TRACK(NAME, TYPE, MSG) \
STATS_DECL(NAME, TYPE, MSG) \
STATS_TRACK(NAME, TYPE)
#define STATS_DECL_AND_TRACK_ARG_ATTR(NAME) \
STATS_DECL_AND_TRACK(NAME, Arguments, BUILD_STAT_MSG_IR_ATTR(arguments, NAME))
#define STATS_DECL_AND_TRACK_CSARG_ATTR(NAME) \
STATS_DECL_AND_TRACK(NAME, CSArguments, \
BUILD_STAT_MSG_IR_ATTR(call site arguments, NAME))
#define STATS_DECL_AND_TRACK_FN_ATTR(NAME) \
STATS_DECL_AND_TRACK(NAME, Function, BUILD_STAT_MSG_IR_ATTR(functions, NAME))
#define STATS_DECL_AND_TRACK_FNRET_ATTR(NAME) \
STATS_DECL_AND_TRACK(NAME, FunctionReturn, \
BUILD_STAT_MSG_IR_ATTR(function returns, NAME));
// TODO: Determine a good default value.
//
// In the LLVM-TS and SPEC2006, 32 seems to not induce compile time overheads
// (when run with the first 5 abstract attributes). The results also indicate
// that we never reach 32 iterations but always find a fixpoint sooner.
//
// This will become more evolved once we perform two interleaved fixpoint
// iterations: bottom-up and top-down.
static cl::opt<unsigned>
MaxFixpointIterations("attributor-max-iterations", cl::Hidden,
cl::desc("Maximal number of fixpoint iterations."),
cl::init(32));
static cl::opt<bool> DisableAttributor(
"attributor-disable", cl::Hidden,
cl::desc("Disable the attributor inter-procedural deduction pass."),
cl::init(true));
static cl::opt<bool> VerifyAttributor(
"attributor-verify", cl::Hidden,
cl::desc("Verify the Attributor deduction and "
"manifestation of attributes -- may issue false-positive errors"),
cl::init(false));
/// Logic operators for the change status enum class.
///
///{
ChangeStatus llvm::operator|(ChangeStatus l, ChangeStatus r) {
return l == ChangeStatus::CHANGED ? l : r;
}
ChangeStatus llvm::operator&(ChangeStatus l, ChangeStatus r) {
return l == ChangeStatus::UNCHANGED ? l : r;
}
///}
template <typename StateTy>
using followValueCB_t = std::function<bool(Value *, StateTy &State)>;
template <typename StateTy>
using visitValueCB_t = std::function<void(Value *, StateTy &State)>;
/// Recursively visit all values that might become \p InitV at some point. This
/// will be done by looking through cast instructions, selects, phis, and calls
/// with the "returned" attribute. The callback \p FollowValueCB is asked before
/// a potential origin value is looked at. If no \p FollowValueCB is passed, a
/// default one is used that will make sure we visit every value only once. Once
/// we cannot look through the value any further, the callback \p VisitValueCB
/// is invoked and passed the current value and the \p State. To limit how much
/// effort is invested, we will never visit more than \p MaxValues values.
template <typename StateTy>
static bool genericValueTraversal(
Value *InitV, StateTy &State, visitValueCB_t<StateTy> &VisitValueCB,
followValueCB_t<StateTy> *FollowValueCB = nullptr, int MaxValues = 8) {
SmallPtrSet<Value *, 16> Visited;
followValueCB_t<bool> DefaultFollowValueCB = [&](Value *Val, bool &) {
return Visited.insert(Val).second;
};
if (!FollowValueCB)
FollowValueCB = &DefaultFollowValueCB;
SmallVector<Value *, 16> Worklist;
Worklist.push_back(InitV);
int Iteration = 0;
do {
Value *V = Worklist.pop_back_val();
// Check if we should process the current value. To prevent endless
// recursion keep a record of the values we followed!
if (!(*FollowValueCB)(V, State))
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.
if (V->getType()->isPointerTy()) {
V = V->stripPointerCasts();
} else {
CallSite CS(V);
if (CS && CS.getCalledFunction()) {
Value *NewV = nullptr;
for (Argument &Arg : CS.getCalledFunction()->args())
if (Arg.hasReturnedAttr()) {
NewV = CS.getArgOperand(Arg.getArgNo());
break;
}
if (NewV) {
Worklist.push_back(NewV);
continue;
}
}
}
// Look through select instructions, visit both potential values.
if (auto *SI = dyn_cast<SelectInst>(V)) {
Worklist.push_back(SI->getTrueValue());
Worklist.push_back(SI->getFalseValue());
continue;
}
// Look through phi nodes, visit all operands.
if (auto *PHI = dyn_cast<PHINode>(V)) {
Worklist.append(PHI->op_begin(), PHI->op_end());
continue;
}
// Once a leaf is reached we inform the user through the callback.
VisitValueCB(V, State);
} while (!Worklist.empty());
// All values have been visited.
return true;
}
/// Return true if \p New is equal or worse than \p Old.
static bool isEqualOrWorse(const Attribute &New, const Attribute &Old) {
if (!Old.isIntAttribute())
return true;
return Old.getValueAsInt() >= New.getValueAsInt();
}
/// Return true if the information provided by \p Attr was added to the
/// attribute list \p Attrs. This is only the case if it was not already present
/// in \p Attrs at the position describe by \p PK and \p AttrIdx.
static bool addIfNotExistent(LLVMContext &Ctx, const Attribute &Attr,
AttributeList &Attrs, int AttrIdx) {
if (Attr.isEnumAttribute()) {
Attribute::AttrKind Kind = Attr.getKindAsEnum();
if (Attrs.hasAttribute(AttrIdx, Kind))
if (isEqualOrWorse(Attr, Attrs.getAttribute(AttrIdx, Kind)))
return false;
Attrs = Attrs.addAttribute(Ctx, AttrIdx, Attr);
return true;
}
if (Attr.isStringAttribute()) {
StringRef Kind = Attr.getKindAsString();
if (Attrs.hasAttribute(AttrIdx, Kind))
if (isEqualOrWorse(Attr, Attrs.getAttribute(AttrIdx, Kind)))
return false;
Attrs = Attrs.addAttribute(Ctx, AttrIdx, Attr);
return true;
}
if (Attr.isIntAttribute()) {
Attribute::AttrKind Kind = Attr.getKindAsEnum();
if (Attrs.hasAttribute(AttrIdx, Kind))
if (isEqualOrWorse(Attr, Attrs.getAttribute(AttrIdx, Kind)))
return false;
Attrs = Attrs.removeAttribute(Ctx, AttrIdx, Kind);
Attrs = Attrs.addAttribute(Ctx, AttrIdx, Attr);
return true;
}
llvm_unreachable("Expected enum or string attribute!");
}
ChangeStatus AbstractAttribute::update(Attributor &A) {
ChangeStatus HasChanged = ChangeStatus::UNCHANGED;
if (getState().isAtFixpoint())
return HasChanged;
LLVM_DEBUG(dbgs() << "[Attributor] Update: " << *this << "\n");
HasChanged = updateImpl(A);
LLVM_DEBUG(dbgs() << "[Attributor] Update " << HasChanged << " " << *this
<< "\n");
return HasChanged;
}
ChangeStatus
IRAttributeManifest::manifestAttrs(Attributor &A, IRPosition &IRP,
const ArrayRef<Attribute> &DeducedAttrs) {
assert(IRP.getAssociatedValue() &&
"Attempted to manifest an attribute without associated value!");
ChangeStatus HasChanged = ChangeStatus::UNCHANGED;
Function &ScopeFn = IRP.getAnchorScope();
LLVMContext &Ctx = ScopeFn.getContext();
IRPosition::Kind PK = IRP.getPositionKind();
// In the following some generic code that will manifest attributes in
// DeducedAttrs if they improve the current IR. Due to the different
// annotation positions we use the underlying AttributeList interface.
AttributeList Attrs;
switch (PK) {
case IRPosition::IRP_ARGUMENT:
case IRPosition::IRP_FUNCTION:
case IRPosition::IRP_RETURNED:
Attrs = ScopeFn.getAttributes();
break;
case IRPosition::IRP_CALL_SITE_ARGUMENT:
Attrs = ImmutableCallSite(&IRP.getAnchorValue()).getAttributes();
break;
}
for (const Attribute &Attr : DeducedAttrs) {
if (!addIfNotExistent(Ctx, Attr, Attrs, IRP.getAttrIdx()))
continue;
HasChanged = ChangeStatus::CHANGED;
}
if (HasChanged == ChangeStatus::UNCHANGED)
return HasChanged;
switch (PK) {
case IRPosition::IRP_ARGUMENT:
case IRPosition::IRP_FUNCTION:
case IRPosition::IRP_RETURNED:
ScopeFn.setAttributes(Attrs);
break;
case IRPosition::IRP_CALL_SITE_ARGUMENT:
CallSite(&IRP.getAnchorValue()).setAttributes(Attrs);
}
return HasChanged;
}
/// -----------------------NoUnwind Function Attribute--------------------------
struct AANoUnwindImpl : AANoUnwind {
IRPositionConstructorForward(AANoUnwindImpl, AANoUnwind);
const std::string getAsStr() const override {
return getAssumed() ? "nounwind" : "may-unwind";
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
};
struct AANoUnwindFunction final : public AANoUnwindImpl {
AANoUnwindFunction(Function &F) : AANoUnwindImpl(F, IRP_FUNCTION) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_FN_ATTR(nounwind)
}
};
ChangeStatus AANoUnwindImpl::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
// The map from instruction opcodes to those instructions in the function.
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;
auto *NoUnwindAA = A.getAAFor<AANoUnwind>(*this, I);
return NoUnwindAA && NoUnwindAA->isAssumedNoUnwind();
};
if (!A.checkForAllInstructions(F, CheckForNoUnwind, *this, Opcodes))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// --------------------- 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.
///
/// TODO: We should use liveness during construction of the returned values map
/// and before we set HasOverdefinedReturnedCalls.
class AAReturnedValuesImpl : public AAReturnedValues, public AbstractState {
/// Mapping of values potentially returned by the associated function to the
/// return instructions that might return them.
DenseMap<Value *, SmallPtrSet<ReturnInst *, 2>> ReturnedValues;
/// State flags
///
///{
bool IsFixed;
bool IsValidState;
bool HasOverdefinedReturnedCalls;
///}
/// Collect values that could become \p V in the set \p Values, each mapped to
/// \p ReturnInsts.
void collectValuesRecursively(
Attributor &A, Value *V, SmallPtrSetImpl<ReturnInst *> &ReturnInsts,
DenseMap<Value *, SmallPtrSet<ReturnInst *, 2>> &Values) {
visitValueCB_t<bool> VisitValueCB = [&](Value *Val, bool &) {
assert(!isa<Instruction>(Val) ||
&getAnchorScope() == cast<Instruction>(Val)->getFunction());
Values[Val].insert(ReturnInsts.begin(), ReturnInsts.end());
};
bool UnusedBool;
bool Success = genericValueTraversal(V, UnusedBool, VisitValueCB);
// If we did abort the above traversal we haven't see all the values.
// Consequently, we cannot know if the information we would derive is
// accurate so we give up early.
if (!Success)
indicatePessimisticFixpoint();
}
public:
IRPositionConstructorForward(AAReturnedValuesImpl, AAReturnedValues);
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
// Reset the state.
setAssociatedValue(nullptr);
IsFixed = false;
IsValidState = true;
HasOverdefinedReturnedCalls = false;
ReturnedValues.clear();
Function &F = getAnchorScope();
// 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];
for (Instruction *RI : OpcodeInstMap[Instruction::Ret])
ReturnInstSet.insert(cast<ReturnInst>(RI));
indicateOptimisticFixpoint();
return;
}
}
// If no argument was marked as returned we look at all return instructions
// and collect potentially returned values.
for (Instruction *RI : OpcodeInstMap[Instruction::Ret]) {
SmallPtrSet<ReturnInst *, 1> RISet({cast<ReturnInst>(RI)});
collectValuesRecursively(A, cast<ReturnInst>(RI)->getReturnValue(), RISet,
ReturnedValues);
}
}
/// 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;
/// Return the number of potential return values, -1 if unknown.
size_t getNumReturnValues() const {
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(
const function_ref<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
&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;
IsValidState &= true;
return ChangeStatus::UNCHANGED;
}
ChangeStatus indicatePessimisticFixpoint() override {
IsFixed = true;
IsValidState = false;
return ChangeStatus::CHANGED;
}
};
struct AAReturnedValuesFunction final : public AAReturnedValuesImpl {
AAReturnedValuesFunction(Function &F)
: AAReturnedValuesImpl(F, IRP_FUNCTION) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_ARG_ATTR(returned)
}
};
ChangeStatus AAReturnedValuesImpl::manifest(Attributor &A) {
ChangeStatus Changed = ChangeStatus::UNCHANGED;
// Bookkeeping.
assert(isValidState());
STATS_DECL_AND_TRACK(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_DECL_AND_TRACK(UniqueReturnValue, FunctionReturn,
"Number of function with unique return");
// If the assumed unique return value is an argument, annotate it.
if (auto *UniqueRVArg = dyn_cast<Argument>(UniqueRV.getValue())) {
setAssociatedValue(UniqueRVArg);
setAttributeIdx(UniqueRVArg->getArgNo() + AttributeList::FirstArgIndex);
Changed = IRAttribute::manifest(A) | Changed;
}
return Changed;
}
const std::string AAReturnedValuesImpl::getAsStr() const {
return (isAtFixpoint() ? "returns(#" : "may-return(#") +
(isValidState() ? std::to_string(getNumReturnValues()) : "?") +
")[OD: " + std::to_string(HasOverdefinedReturnedCalls) + "]";
}
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(getAnchorScope(), Pred, *this))
UniqueRV = nullptr;
return UniqueRV;
}
bool AAReturnedValuesImpl::checkForAllReturnedValuesAndReturnInsts(
const function_ref<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
&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;
const SmallPtrSetImpl<ReturnInst *> &RetInsts = It.second;
ImmutableCallSite ICS(RV);
if (ICS && !HasOverdefinedReturnedCalls)
continue;
if (!Pred(*RV, RetInsts))
return false;
}
return true;
}
ChangeStatus AAReturnedValuesImpl::updateImpl(Attributor &A) {
// Check if we know of any values returned by the associated function,
// if not, we are done.
if (getNumReturnValues() == 0) {
indicateOptimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
// Check if any of the returned values is a call site we can refine.
decltype(ReturnedValues) AddRVs;
bool HasCallSite = false;
// Keep track of any change to trigger updates on dependent attributes.
ChangeStatus Changed = ChangeStatus::UNCHANGED;
auto *LivenessAA = A.getAAFor<AAIsDead>(*this, getAnchorScope());
// Look at all returned call sites.
for (auto &It : ReturnedValues) {
SmallPtrSet<ReturnInst *, 2> &ReturnInsts = It.second;
Value *RV = It.first;
LLVM_DEBUG(dbgs() << "[AAReturnedValues] Potentially returned value " << *RV
<< "\n");
// Only call sites can change during an update, ignore the rest.
CallSite RetCS(RV);
if (!RetCS)
continue;
// For now, any call site we see will prevent us from directly fixing the
// state. However, if the information on the callees is fixed, the call
// sites will be removed and we will fix the information for this state.
HasCallSite = true;
// Ignore dead ReturnValues.
if (LivenessAA &&
!LivenessAA->isLiveInstSet(ReturnInsts.begin(), ReturnInsts.end())) {
LLVM_DEBUG(dbgs() << "[AAReturnedValues] all returns are assumed dead, "
"skip it for now\n");
continue;
}
// Try to find a assumed unique return value for the called function.
auto *RetCSAA = A.getAAFor<AAReturnedValuesImpl>(*this, *RV);
if (!RetCSAA) {
if (!HasOverdefinedReturnedCalls)
Changed = ChangeStatus::CHANGED;
HasOverdefinedReturnedCalls = true;
LLVM_DEBUG(dbgs() << "[AAReturnedValues] Returned call site (" << *RV
<< ") with " << (RetCSAA ? "invalid" : "no")
<< " associated state\n");
continue;
}
// Try to find a assumed unique return value for the called function.
Optional<Value *> AssumedUniqueRV = RetCSAA->getAssumedUniqueReturnValue(A);
// If no assumed unique return value was found due to the lack of
// candidates, we may need to resolve more calls (through more update
// iterations) or the called function will not return. Either way, we simply
// stick with the call sites as return values. Because there were not
// multiple possibilities, we do not treat it as overdefined.
if (!AssumedUniqueRV.hasValue())
continue;
// If multiple, non-refinable values were found, there cannot be a unique
// return value for the called function. The returned call is overdefined!
if (!AssumedUniqueRV.getValue()) {
if (!HasOverdefinedReturnedCalls)
Changed = ChangeStatus::CHANGED;
HasOverdefinedReturnedCalls = true;
LLVM_DEBUG(dbgs() << "[AAReturnedValues] Returned call site has multiple "
"potentially returned values\n");
continue;
}
LLVM_DEBUG({
bool UniqueRVIsKnown = RetCSAA->isAtFixpoint();
dbgs() << "[AAReturnedValues] Returned call site "
<< (UniqueRVIsKnown ? "known" : "assumed")
<< " unique return value: " << *AssumedUniqueRV << "\n";
});
// The assumed unique return value.
Value *AssumedRetVal = AssumedUniqueRV.getValue();
// If the assumed unique return value is an argument, lookup the matching
// call site operand and recursively collect new returned values.
// If it is not an argument, it is just put into the set of returned values
// as we would have already looked through casts, phis, and similar values.
if (Argument *AssumedRetArg = dyn_cast<Argument>(AssumedRetVal))
collectValuesRecursively(A,
RetCS.getArgOperand(AssumedRetArg->getArgNo()),
ReturnInsts, AddRVs);
else
AddRVs[AssumedRetVal].insert(ReturnInsts.begin(), ReturnInsts.end());
}
for (auto &It : AddRVs) {
assert(!It.second.empty() && "Entry does not add anything.");
auto &ReturnInsts = ReturnedValues[It.first];
for (ReturnInst *RI : It.second)
if (ReturnInsts.insert(RI).second) {
LLVM_DEBUG(dbgs() << "[AAReturnedValues] Add new returned value "
<< *It.first << " => " << *RI << "\n");
Changed = ChangeStatus::CHANGED;
}
}
// If there is no call site in the returned values we are done.
if (!HasCallSite) {
indicateOptimisticFixpoint();
return ChangeStatus::CHANGED;
}
return Changed;
}
/// ------------------------ NoSync Function Attribute -------------------------
struct AANoSyncImpl : AANoSync {
IRPositionConstructorForward(AANoSyncImpl, AANoSync);
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 used to determine whether an instruction is volatile.
static bool isVolatile(Instruction *I);
/// Helper function uset to check if intrinsic is volatile (memcpy, memmove,
/// memset).
static bool isNoSyncIntrinsic(Instruction *I);
};
struct AANoSyncFunction final : public AANoSyncImpl {
AANoSyncFunction(Function &F) : AANoSyncImpl(F, IRP_FUNCTION) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECL_AND_TRACK_FN_ATTR(nosync) }
};
bool AANoSyncImpl::isNonRelaxedAtomic(Instruction *I) {
if (!I->isAtomic())
return false;
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;
case Instruction::Fence: {
auto *FI = cast<FenceInst>(I);
if (FI->getSyncScopeID() == SyncScope::SingleThread)
return false;
Ordering = FI->getOrdering();
break;
}
case Instruction::AtomicCmpXchg: {
AtomicOrdering Success = cast<AtomicCmpXchgInst>(I)->getSuccessOrdering();
AtomicOrdering Failure = cast<AtomicCmpXchgInst>(I)->getFailureOrdering();
// Only if both are relaxed, than it can be treated as relaxed.
// Otherwise it is non-relaxed.
if (Success != AtomicOrdering::Unordered &&
Success != AtomicOrdering::Monotonic)
return true;
if (Failure != AtomicOrdering::Unordered &&
Failure != AtomicOrdering::Monotonic)
return true;
return false;
}
default:
llvm_unreachable(
"New atomic operations need to be known in the attributor.");
}
// Relaxed.
if (Ordering == AtomicOrdering::Unordered ||
Ordering == AtomicOrdering::Monotonic)
return false;
return true;
}
/// Checks if an intrinsic is nosync. Currently only checks mem* intrinsics.
/// FIXME: We should ipmrove the handling of intrinsics.
bool AANoSyncImpl::isNoSyncIntrinsic(Instruction *I) {
if (auto *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
/// Element wise atomic memory intrinsics are can only be unordered,
/// therefore nosync.
case Intrinsic::memset_element_unordered_atomic:
case Intrinsic::memmove_element_unordered_atomic:
case Intrinsic::memcpy_element_unordered_atomic:
return true;
case Intrinsic::memset:
case Intrinsic::memmove:
case Intrinsic::memcpy:
if (!cast<MemIntrinsic>(II)->isVolatile())
return true;
return false;
default:
return false;
}
}
return false;
}
bool AANoSyncImpl::isVolatile(Instruction *I) {
assert(!ImmutableCallSite(I) && !isa<CallBase>(I) &&
"Calls should not be checked here");
switch (I->getOpcode()) {
case Instruction::AtomicRMW:
return cast<AtomicRMWInst>(I)->isVolatile();
case Instruction::Store:
return cast<StoreInst>(I)->isVolatile();
case Instruction::Load:
return cast<LoadInst>(I)->isVolatile();
case Instruction::AtomicCmpXchg:
return cast<AtomicCmpXchgInst>(I)->isVolatile();
default:
return false;
}
}
ChangeStatus AANoSyncImpl::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
auto CheckRWInstForNoSync = [&](Instruction &I) {
/// We are looking for volatile instructions or Non-Relaxed atomics.
/// FIXME: We should ipmrove the handling of intrinsics.
ImmutableCallSite ICS(&I);
auto *NoSyncAA = A.getAAFor<AANoSyncImpl>(*this, I);
if (isa<IntrinsicInst>(&I) && isNoSyncIntrinsic(&I))
return true;
if (ICS && (!NoSyncAA || !NoSyncAA->isAssumedNoSync()) &&
!ICS.hasFnAttr(Attribute::NoSync))
return false;
if (ICS)
return true;
if (!isVolatile(&I) && !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 !ImmutableCallSite(&I).isConvergent();
};
if (!A.checkForAllReadWriteInstructions(F, CheckRWInstForNoSync, *this) ||
!A.checkForAllCallLikeInstructions(F, CheckForNoSync, *this))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// ------------------------ No-Free Attributes ----------------------------
struct AANoFreeImpl : public AANoFree {
IRPositionConstructorForward(AANoFreeImpl, AANoFree);
/// See AbstractAttribute::getAsStr().
const std::string getAsStr() const override {
return getAssumed() ? "nofree" : "may-free";
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
};
struct AANoFreeFunction final : public AANoFreeImpl {
AANoFreeFunction(Function &F) : AANoFreeImpl(F, IRP_FUNCTION) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override { STATS_DECL_AND_TRACK_FN_ATTR(nofree) }
};
ChangeStatus AANoFreeImpl::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
auto CheckForNoFree = [&](Instruction &I) {
if (ImmutableCallSite(&I).hasFnAttr(Attribute::NoFree))
return true;
auto *NoFreeAA = A.getAAFor<AANoFreeImpl>(*this, I);
return NoFreeAA && NoFreeAA->isAssumedNoFree();
};
if (!A.checkForAllCallLikeInstructions(F, CheckForNoFree, *this))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// ------------------------ NonNull Argument Attribute ------------------------
struct AANonNullImpl : AANonNull {
IRPositionConstructorForward(AANonNullImpl, AANonNull);
/// See AbstractAttribute::getAsStr().
const std::string getAsStr() const override {
return getAssumed() ? "nonnull" : "may-null";
}
/// Generate a predicate that checks if a given value is assumed nonnull.
/// The generated function returns true if a value satisfies any of
/// following conditions.
/// (i) A value is known nonZero(=nonnull).
/// (ii) A value is associated with AANonNull and its isAssumedNonNull() is
/// true.
std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
generatePredicate(Attributor &);
};
std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
AANonNullImpl::generatePredicate(Attributor &A) {
// FIXME: The `AAReturnedValues` should provide the predicate with the
// `ReturnInst` vector as well such that we can use the control flow sensitive
// version of `isKnownNonZero`. This should fix `test11` in
// `test/Transforms/FunctionAttrs/nonnull.ll`
std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> Pred =
[&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &RetInsts) -> bool {
if (isKnownNonZero(&RV, A.getDataLayout()))
return true;
auto *NonNullAA = A.getAAFor<AANonNull>(*this, RV);
ImmutableCallSite ICS(&RV);
if ((!NonNullAA || !NonNullAA->isAssumedNonNull()) &&
(!ICS || !ICS.hasRetAttr(Attribute::NonNull)))
return false;
return true;
};
return Pred;
}
/// NonNull attribute for function return value.
struct AANonNullReturned final : AANonNullImpl {
AANonNullReturned(Function &F) : AANonNullImpl(F, IRP_RETURNED) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
Function &F = getAnchorScope();
// Already nonnull.
if (F.getAttributes().hasAttribute(AttributeList::ReturnIndex,
Attribute::NonNull) ||
F.getAttributes().hasAttribute(AttributeList::ReturnIndex,
Attribute::Dereferenceable))
indicateOptimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_FNRET_ATTR(nonnull)
}
};
ChangeStatus AANonNullReturned::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> Pred =
this->generatePredicate(A);
if (!A.checkForAllReturnedValuesAndReturnInsts(F, Pred, *this))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// NonNull attribute for function argument.
struct AANonNullArgument final : AANonNullImpl {
AANonNullArgument(Argument &A) : AANonNullImpl(A) {}
/// See AbstractAttriubute::initialize(...).
void initialize(Attributor &A) override {
Argument *Arg = cast<Argument>(getAssociatedValue());
if (Arg->hasNonNullAttr())
indicateOptimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_ARG_ATTR(nonnull)
}
};
/// NonNull attribute for a call site argument.
struct AANonNullCallSiteArgument final : AANonNullImpl {
AANonNullCallSiteArgument(Instruction &I, unsigned ArgNo)
: AANonNullImpl(CallSite(&I).getArgOperand(ArgNo), I, ArgNo) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
CallSite CS(&getAnchorValue());
if (CS.paramHasAttr(getArgNo(), getAttrKind()) ||
CS.paramHasAttr(getArgNo(), Attribute::Dereferenceable) ||
isKnownNonZero(getAssociatedValue(), A.getDataLayout()))
indicateOptimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(Attributor &A).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_CSARG_ATTR(nonnull)
}
};
ChangeStatus AANonNullArgument::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
unsigned ArgNo = getArgNo();
// Callback function
std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) {
assert(CS && "Sanity check: Call site was not initialized properly!");
auto *NonNullAA =
A.getAAFor<AANonNullImpl>(*this, *CS.getInstruction(), ArgNo);
// Check that NonNullAA is AANonNullCallSiteArgument.
if (NonNullAA) {
ImmutableCallSite ICS(&NonNullAA->getAnchorValue());
if (ICS && CS.getInstruction() == ICS.getInstruction())
return NonNullAA->isAssumedNonNull();
return false;
}
if (CS.paramHasAttr(ArgNo, Attribute::NonNull))
return true;
Value *V = CS.getArgOperand(ArgNo);
if (isKnownNonZero(V, A.getDataLayout()))
return true;
return false;
};
if (!A.checkForAllCallSites(F, CallSiteCheck, *this, true))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
ChangeStatus AANonNullCallSiteArgument::updateImpl(Attributor &A) {
// NOTE: Never look at the argument of the callee in this method.
// If we do this, "nonnull" is always deduced because of the assumption.
Value &V = *getAssociatedValue();
auto *NonNullAA = A.getAAFor<AANonNull>(*this, V);
if (!NonNullAA || !NonNullAA->isAssumedNonNull())
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// ------------------------ Will-Return Attributes ----------------------------
struct AAWillReturnImpl : public AAWillReturn {
IRPositionConstructorForward(AAWillReturnImpl, AAWillReturn);
/// See AbstractAttribute::getAsStr()
const std::string getAsStr() const override {
return getAssumed() ? "willreturn" : "may-noreturn";
}
};
struct AAWillReturnFunction final : AAWillReturnImpl {
AAWillReturnFunction(Function &F) : AAWillReturnImpl(F, IRP_FUNCTION) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override;
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_FN_ATTR(willreturn)
}
};
// Helper function that checks whether a function has any cycle.
// TODO: Replace with more efficent code
bool containsCycle(Function &F) {
SmallPtrSet<BasicBlock *, 32> Visited;
// Traverse BB by dfs and check whether successor is already visited.
for (BasicBlock *BB : depth_first(&F)) {
Visited.insert(BB);
for (auto *SuccBB : successors(BB)) {
if (Visited.count(SuccBB))
return true;
}
}
return false;
}
// Helper function that checks the function have a loop which might become an
// endless loop
// FIXME: Any cycle is regarded as endless loop for now.
// We have to allow some patterns.
bool containsPossiblyEndlessLoop(Function &F) { return containsCycle(F); }
void AAWillReturnFunction::initialize(Attributor &A) {
Function &F = getAnchorScope();
if (containsPossiblyEndlessLoop(F))
indicatePessimisticFixpoint();
}
ChangeStatus AAWillReturnFunction::updateImpl(Attributor &A) {
const Function &F = getAnchorScope();
// The map from instruction opcodes to those instructions in the function.
auto CheckForWillReturn = [&](Instruction &I) {
ImmutableCallSite ICS(&I);
if (ICS.hasFnAttr(Attribute::WillReturn))
return true;
auto *WillReturnAA = A.getAAFor<AAWillReturn>(*this, I);
if (!WillReturnAA || !WillReturnAA->isAssumedWillReturn())
return false;
// FIXME: Prohibit any recursion for now.
if (ICS.hasFnAttr(Attribute::NoRecurse))
return true;
auto *NoRecurseAA = A.getAAFor<AANoRecurse>(*this, I);
return NoRecurseAA && NoRecurseAA->isAssumedNoRecurse();
};
if (!A.checkForAllCallLikeInstructions(F, CheckForWillReturn, *this))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// ------------------------ NoAlias Argument Attribute ------------------------
struct AANoAliasImpl : AANoAlias {
IRPositionConstructorForward(AANoAliasImpl, AANoAlias);
const std::string getAsStr() const override {
return getAssumed() ? "noalias" : "may-alias";
}
};
/// NoAlias attribute for function return value.
struct AANoAliasReturned final : AANoAliasImpl {
AANoAliasReturned(Function &F) : AANoAliasImpl(F, IRP_RETURNED) {}
/// See AbstractAttriubute::initialize(...).
void initialize(Attributor &A) override {
Function &F = getAnchorScope();
// Already noalias.
if (F.returnDoesNotAlias()) {
indicateOptimisticFixpoint();
return;
}
}
/// See AbstractAttribute::updateImpl(...).
virtual ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_FNRET_ATTR(noalias)
}
};
ChangeStatus AANoAliasReturned::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
auto CheckReturnValue = [&](Value &RV) -> bool {
if (Constant *C = dyn_cast<Constant>(&RV))
if (C->isNullValue() || isa<UndefValue>(C))
return true;
/// For now, we can only deduce noalias if we have call sites.
/// FIXME: add more support.
ImmutableCallSite ICS(&RV);
if (!ICS)
return false;
if (!ICS.returnDoesNotAlias()) {
auto *NoAliasAA = A.getAAFor<AANoAlias>(*this, RV);
if (!NoAliasAA || !NoAliasAA->isAssumedNoAlias())
return false;
}
/// FIXME: We can improve capture check in two ways:
/// 1. Use the AANoCapture facilities.
/// 2. Use the location of return insts for escape queries.
if (PointerMayBeCaptured(&RV, /* ReturnCaptures */ false,
/* StoreCaptures */ true))
return false;
return true;
};
if (!A.checkForAllReturnedValues(F, CheckReturnValue, *this))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// -------------------AAIsDead Function Attribute-----------------------
struct AAIsDeadImpl : public AAIsDead {
IRPositionConstructorForward(AAIsDeadImpl, AAIsDead);
void initialize(Attributor &A) override {
const Function &F = getAnchorScope();
ToBeExploredPaths.insert(&(F.getEntryBlock().front()));
AssumedLiveBlocks.insert(&(F.getEntryBlock()));
for (size_t i = 0; i < ToBeExploredPaths.size(); ++i)
if (const Instruction *NextNoReturnI =
findNextNoReturn(A, ToBeExploredPaths[i]))
NoReturnCalls.insert(NextNoReturnI);
}
/// Find the next assumed noreturn instruction in the block of \p I starting
/// from, thus including, \p I.
///
/// The caller is responsible to monitor the ToBeExploredPaths set as new
/// instructions discovered in other basic block will be placed in there.
///
/// \returns The next assumed noreturn instructions in the block of \p I
/// starting from, thus including, \p I.
const Instruction *findNextNoReturn(Attributor &A, const Instruction *I);
/// See AbstractAttribute::getAsStr().
const std::string getAsStr() const override {
return "Live[#BB " + std::to_string(AssumedLiveBlocks.size()) + "/" +
std::to_string(getAnchorScope().size()) + "][#NRI " +
std::to_string(NoReturnCalls.size()) + "]";
}
/// See AbstractAttribute::manifest(...).
ChangeStatus manifest(Attributor &A) override {
assert(getState().isValidState() &&
"Attempted to manifest an invalid state!");
ChangeStatus HasChanged = ChangeStatus::UNCHANGED;
const Function &F = getAnchorScope();
// Flag to determine if we can change an invoke to a call assuming the
// callee is nounwind. This is not possible if the personality of the
// function allows to catch asynchronous exceptions.
bool Invoke2CallAllowed = !mayCatchAsynchronousExceptions(F);
for (const Instruction *NRC : NoReturnCalls) {
Instruction *I = const_cast<Instruction *>(NRC);
BasicBlock *BB = I->getParent();
Instruction *SplitPos = I->getNextNode();
if (auto *II = dyn_cast<InvokeInst>(I)) {
// If we keep the invoke the split position is at the beginning of the
// normal desitination block (it invokes a noreturn function after all).
BasicBlock *NormalDestBB = II->getNormalDest();
SplitPos = &NormalDestBB->front();
/// Invoke is replaced with a call and unreachable is placed after it if
/// the callee is nounwind and noreturn. Otherwise, we keep the invoke
/// and only place an unreachable in the normal successor.
if (Invoke2CallAllowed) {
if (Function *Callee = II->getCalledFunction()) {
auto *AANoUnw = A.getAAFor<AANoUnwind>(*this, *Callee);
if (Callee->hasFnAttribute(Attribute::NoUnwind) ||
(AANoUnw && AANoUnw->isAssumedNoUnwind())) {
LLVM_DEBUG(dbgs()
<< "[AAIsDead] Replace invoke with call inst\n");
// We do not need an invoke (II) but instead want a call followed
// by an unreachable. However, we do not remove II as other
// abstract attributes might have it cached as part of their
// results. Given that we modify the CFG anyway, we simply keep II
// around but in a new dead block. To avoid II being live through
// a different edge we have to ensure the block we place it in is
// only reached from the current block of II and then not reached
// at all when we insert the unreachable.
SplitBlockPredecessors(NormalDestBB, {BB}, ".i2c");
CallInst *CI = createCallMatchingInvoke(II);
CI->insertBefore(II);
CI->takeName(II);
II->replaceAllUsesWith(CI);
SplitPos = CI->getNextNode();
}
}
}
}
BB = SplitPos->getParent();
SplitBlock(BB, SplitPos);
changeToUnreachable(BB->getTerminator(), /* UseLLVMTrap */ false);
HasChanged = ChangeStatus::CHANGED;
}
return HasChanged;
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AAIsDead::isAssumedDead(BasicBlock *).
bool isAssumedDead(const BasicBlock *BB) const override {
assert(BB->getParent() == &getAnchorScope() &&
"BB must be in the same anchor scope function.");
if (!getAssumed())
return false;
return !AssumedLiveBlocks.count(BB);
}
/// See AAIsDead::isKnownDead(BasicBlock *).
bool isKnownDead(const BasicBlock *BB) const override {
return getKnown() && isAssumedDead(BB);
}
/// See AAIsDead::isAssumed(Instruction *I).
bool isAssumedDead(const Instruction *I) const override {
assert(I->getParent()->getParent() == &getAnchorScope() &&
"Instruction must be in the same anchor scope function.");
if (!getAssumed())
return false;
// If it is not in AssumedLiveBlocks then it for sure dead.
// Otherwise, it can still be after noreturn call in a live block.
if (!AssumedLiveBlocks.count(I->getParent()))
return true;
// If it is not after a noreturn call, than it is live.
return isAfterNoReturn(I);
}
/// See AAIsDead::isKnownDead(Instruction *I).
bool isKnownDead(const Instruction *I) const override {
return getKnown() && isAssumedDead(I);
}
/// Check if instruction is after noreturn call, in other words, assumed dead.
bool isAfterNoReturn(const Instruction *I) const;
/// Determine if \p F might catch asynchronous exceptions.
static bool mayCatchAsynchronousExceptions(const Function &F) {
return F.hasPersonalityFn() && !canSimplifyInvokeNoUnwind(&F);
}
/// Collection of to be explored paths.
SmallSetVector<const Instruction *, 8> ToBeExploredPaths;
/// Collection of all assumed live BasicBlocks.
DenseSet<const BasicBlock *> AssumedLiveBlocks;
/// Collection of calls with noreturn attribute, assumed or knwon.
SmallSetVector<const Instruction *, 4> NoReturnCalls;
};
struct AAIsDeadFunction final : public AAIsDeadImpl {
AAIsDeadFunction(Function &F) : AAIsDeadImpl(F, IRP_FUNCTION) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL(DeadBlocks, Function,
"Number of basic blocks classified as dead");
BUILD_STAT_NAME(DeadBlocks, Function) +=
getAnchorScope().size() - AssumedLiveBlocks.size();
STATS_DECL(PartiallyDeadBlocks, Function,
"Number of basic blocks classified as partially dead");
BUILD_STAT_NAME(PartiallyDeadBlocks, Function) += NoReturnCalls.size();
}
};
bool AAIsDeadImpl::isAfterNoReturn(const Instruction *I) const {
const Instruction *PrevI = I->getPrevNode();
while (PrevI) {
if (NoReturnCalls.count(PrevI))
return true;
PrevI = PrevI->getPrevNode();
}
return false;
}
const Instruction *AAIsDeadImpl::findNextNoReturn(Attributor &A,
const Instruction *I) {
const BasicBlock *BB = I->getParent();
const Function &F = *BB->getParent();
// Flag to determine if we can change an invoke to a call assuming the callee
// is nounwind. This is not possible if the personality of the function allows
// to catch asynchronous exceptions.
bool Invoke2CallAllowed = !mayCatchAsynchronousExceptions(F);
// TODO: We should have a function that determines if an "edge" is dead.
// Edges could be from an instruction to the next or from a terminator
// to the successor. For now, we need to special case the unwind block
// of InvokeInst below.
while (I) {
ImmutableCallSite ICS(I);
if (ICS) {
// Regarless of the no-return property of an invoke instruction we only
// learn that the regular successor is not reachable through this
// instruction but the unwind block might still be.
if (auto *Invoke = dyn_cast<InvokeInst>(I)) {
// Use nounwind to justify the unwind block is dead as well.
auto *AANoUnw = A.getAAFor<AANoUnwind>(*this, *Invoke);
if (!Invoke2CallAllowed ||
(!AANoUnw || !AANoUnw->isAssumedNoUnwind())) {
AssumedLiveBlocks.insert(Invoke->getUnwindDest());
ToBeExploredPaths.insert(&Invoke->getUnwindDest()->front());
}
}
auto *NoReturnAA = A.getAAFor<AANoReturn>(*this, *I);
if (ICS.hasFnAttr(Attribute::NoReturn) ||
(NoReturnAA && NoReturnAA->isAssumedNoReturn()))
return I;
}
I = I->getNextNode();
}
// get new paths (reachable blocks).
for (const BasicBlock *SuccBB : successors(BB)) {
AssumedLiveBlocks.insert(SuccBB);
ToBeExploredPaths.insert(&SuccBB->front());
}
// No noreturn instruction found.
return nullptr;
}
ChangeStatus AAIsDeadImpl::updateImpl(Attributor &A) {
// Temporary collection to iterate over existing noreturn instructions. This
// will alow easier modification of NoReturnCalls collection
SmallVector<const Instruction *, 8> NoReturnChanged;
ChangeStatus Status = ChangeStatus::UNCHANGED;
for (const Instruction *I : NoReturnCalls)
NoReturnChanged.push_back(I);
for (const Instruction *I : NoReturnChanged) {
size_t Size = ToBeExploredPaths.size();
const Instruction *NextNoReturnI = findNextNoReturn(A, I);
if (NextNoReturnI != I) {
Status = ChangeStatus::CHANGED;
NoReturnCalls.remove(I);
if (NextNoReturnI)
NoReturnCalls.insert(NextNoReturnI);
}
// Explore new paths.
while (Size != ToBeExploredPaths.size()) {
Status = ChangeStatus::CHANGED;
if (const Instruction *NextNoReturnI =
findNextNoReturn(A, ToBeExploredPaths[Size++]))
NoReturnCalls.insert(NextNoReturnI);
}
}
LLVM_DEBUG(
dbgs() << "[AAIsDead] AssumedLiveBlocks: " << AssumedLiveBlocks.size()
<< " Total number of blocks: " << getAnchorScope().size() << "\n");
// If we know everything is live there is no need to query for liveness.
if (NoReturnCalls.empty() &&
getAnchorScope().size() == AssumedLiveBlocks.size()) {
// Indicating a pessimistic fixpoint will cause the state to be "invalid"
// which will cause the Attributor to not return the AAIsDead on request,
// which will prevent us from querying isAssumedDead().
indicatePessimisticFixpoint();
assert(!isValidState() && "Expected an invalid state!");
}
return Status;
}
/// -------------------- Dereferenceable Argument Attribute --------------------
struct DerefState : AbstractState {
/// State representing for dereferenceable bytes.
IntegerState DerefBytesState;
/// State representing that whether the value is nonnull or global.
IntegerState NonNullGlobalState;
/// Bits encoding for NonNullGlobalState.
enum {
DEREF_NONNULL = 1 << 0,
DEREF_GLOBAL = 1 << 1,
};
/// See AbstractState::isValidState()
bool isValidState() const override { return DerefBytesState.isValidState(); }
/// See AbstractState::isAtFixpoint()
bool isAtFixpoint() const override {
return !isValidState() || (DerefBytesState.isAtFixpoint() &&
NonNullGlobalState.isAtFixpoint());
}
/// See AbstractState::indicateOptimisticFixpoint(...)
ChangeStatus indicateOptimisticFixpoint() override {
DerefBytesState.indicateOptimisticFixpoint();
NonNullGlobalState.indicateOptimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// See AbstractState::indicatePessimisticFixpoint(...)
ChangeStatus indicatePessimisticFixpoint() override {
DerefBytesState.indicatePessimisticFixpoint();
NonNullGlobalState.indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
/// Update known dereferenceable bytes.
void takeKnownDerefBytesMaximum(uint64_t Bytes) {
DerefBytesState.takeKnownMaximum(Bytes);
}
/// Update assumed dereferenceable bytes.
void takeAssumedDerefBytesMinimum(uint64_t Bytes) {
DerefBytesState.takeAssumedMinimum(Bytes);
}
/// Update assumed NonNullGlobalState
void updateAssumedNonNullGlobalState(bool IsNonNull, bool IsGlobal) {
if (!IsNonNull)
NonNullGlobalState.removeAssumedBits(DEREF_NONNULL);
if (!IsGlobal)
NonNullGlobalState.removeAssumedBits(DEREF_GLOBAL);
}
/// Equality for DerefState.
bool operator==(const DerefState &R) {
return this->DerefBytesState == R.DerefBytesState &&
this->NonNullGlobalState == R.NonNullGlobalState;
}
};
struct AADereferenceableImpl : AADereferenceable, DerefState {
IRPositionConstructorForward(AADereferenceableImpl, AADereferenceable);
using StateType = DerefState;
/// See AbstractAttribute::getState()
/// {
StateType &getState() override { return *this; }
const StateType &getState() const override { return *this; }
/// }
/// See AADereferenceable::getAssumedDereferenceableBytes().
uint32_t getAssumedDereferenceableBytes() const override {
return DerefBytesState.getAssumed();
}
/// See AADereferenceable::getKnownDereferenceableBytes().
uint32_t getKnownDereferenceableBytes() const override {
return DerefBytesState.getKnown();
}
// Helper function for syncing nonnull state.
void syncNonNull(const AANonNull *NonNullAA) {
if (!NonNullAA) {
NonNullGlobalState.removeAssumedBits(DEREF_NONNULL);
return;
}
if (NonNullAA->isKnownNonNull())
NonNullGlobalState.addKnownBits(DEREF_NONNULL);
if (!NonNullAA->isAssumedNonNull())
NonNullGlobalState.removeAssumedBits(DEREF_NONNULL);
}
/// See AADereferenceable::isAssumedGlobal().
bool isAssumedGlobal() const override {
return NonNullGlobalState.isAssumed(DEREF_GLOBAL);
}
/// See AADereferenceable::isKnownGlobal().
bool isKnownGlobal() const override {
return NonNullGlobalState.isKnown(DEREF_GLOBAL);
}
/// See AADereferenceable::isAssumedNonNull().
bool isAssumedNonNull() const override {
return NonNullGlobalState.isAssumed(DEREF_NONNULL);
}
/// See AADereferenceable::isKnownNonNull().
bool isKnownNonNull() const override {
return NonNullGlobalState.isKnown(DEREF_NONNULL);
}
void getDeducedAttributes(LLVMContext &Ctx,
SmallVectorImpl<Attribute> &Attrs) const override {
// TODO: Add *_globally support
if (isAssumedNonNull())
Attrs.emplace_back(Attribute::getWithDereferenceableBytes(
Ctx, getAssumedDereferenceableBytes()));
else
Attrs.emplace_back(Attribute::getWithDereferenceableOrNullBytes(
Ctx, getAssumedDereferenceableBytes()));
}
uint64_t computeAssumedDerefenceableBytes(Attributor &A, Value &V,
bool &IsNonNull, bool &IsGlobal);
void initialize(Attributor &A) override {
Function &F = getAnchorScope();
unsigned AttrIdx = getIRPosition().getAttrIdx();
for (Attribute::AttrKind AK :
{Attribute::Dereferenceable, Attribute::DereferenceableOrNull})
if (F.getAttributes().hasAttribute(AttrIdx, AK))
takeKnownDerefBytesMaximum(F.getAttribute(AttrIdx, AK).getValueAsInt());
}
/// See AbstractAttribute::getAsStr().
const std::string getAsStr() const override {
if (!getAssumedDereferenceableBytes())
return "unknown-dereferenceable";
return std::string("dereferenceable") +
(isAssumedNonNull() ? "" : "_or_null") +
(isAssumedGlobal() ? "_globally" : "") + "<" +
std::to_string(getKnownDereferenceableBytes()) + "-" +
std::to_string(getAssumedDereferenceableBytes()) + ">";
}
};
struct AADereferenceableReturned final : AADereferenceableImpl {
AADereferenceableReturned(Function &F)
: AADereferenceableImpl(F, IRP_RETURNED) {}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_FNRET_ATTR(dereferenceable)
}
};
// Helper function that returns dereferenceable bytes.
static uint64_t calcDifferenceIfBaseIsNonNull(int64_t DerefBytes,
int64_t Offset, bool IsNonNull) {
if (!IsNonNull)
return 0;
return std::max((int64_t)0, DerefBytes - Offset);
}
uint64_t AADereferenceableImpl::computeAssumedDerefenceableBytes(
Attributor &A, Value &V, bool &IsNonNull, bool &IsGlobal) {
// TODO: Tracking the globally flag.
IsGlobal = false;
// First, we try to get information about V from Attributor.
if (auto *DerefAA = A.getAAFor<AADereferenceable>(*this, V)) {
IsNonNull &= DerefAA->isAssumedNonNull();
return DerefAA->getAssumedDereferenceableBytes();
}
// Otherwise, we try to compute assumed bytes from base pointer.
const DataLayout &DL = A.getDataLayout();
unsigned IdxWidth =
DL.getIndexSizeInBits(V.getType()->getPointerAddressSpace());
APInt Offset(IdxWidth, 0);
Value *Base = V.stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
if (auto *BaseDerefAA = A.getAAFor<AADereferenceable>(*this, *Base)) {
IsNonNull &= Offset != 0;
return calcDifferenceIfBaseIsNonNull(
BaseDerefAA->getAssumedDereferenceableBytes(), Offset.getSExtValue(),
Offset != 0 || BaseDerefAA->isAssumedNonNull());
}
// Then, use IR information.
if (isDereferenceablePointer(Base, Base->getType(), DL))
return calcDifferenceIfBaseIsNonNull(
DL.getTypeStoreSize(Base->getType()->getPointerElementType()),
Offset.getSExtValue(),
!NullPointerIsDefined(&getAnchorScope(),
V.getType()->getPointerAddressSpace()));
IsNonNull = false;
return 0;
}
ChangeStatus AADereferenceableReturned::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
auto BeforeState = static_cast<DerefState>(*this);
syncNonNull(A.getAAFor<AANonNull>(*this, F));
bool IsNonNull = isAssumedNonNull();
bool IsGlobal = isAssumedGlobal();
auto CheckReturnValue = [&](Value &RV) -> bool {
takeAssumedDerefBytesMinimum(
computeAssumedDerefenceableBytes(A, RV, IsNonNull, IsGlobal));
return isValidState();
};
if (A.checkForAllReturnedValues(F, CheckReturnValue, *this)) {
updateAssumedNonNullGlobalState(IsNonNull, IsGlobal);
return BeforeState == static_cast<DerefState>(*this)
? ChangeStatus::UNCHANGED
: ChangeStatus::CHANGED;
}
return indicatePessimisticFixpoint();
}
struct AADereferenceableArgument final : AADereferenceableImpl {
AADereferenceableArgument(Argument &A) : AADereferenceableImpl(A) {}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_ARG_ATTR(dereferenceable)
}
};
ChangeStatus AADereferenceableArgument::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
Argument &Arg = cast<Argument>(getAnchorValue());
auto BeforeState = static_cast<DerefState>(*this);
unsigned ArgNo = Arg.getArgNo();
syncNonNull(A.getAAFor<AANonNull>(*this, F, ArgNo));
bool IsNonNull = isAssumedNonNull();
bool IsGlobal = isAssumedGlobal();
// Callback function
std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) -> bool {
assert(CS && "Sanity check: Call site was not initialized properly!");
// Check that DereferenceableAA is AADereferenceableCallSiteArgument.
if (auto *DereferenceableAA =
A.getAAFor<AADereferenceable>(*this, *CS.getInstruction(), ArgNo)) {
ImmutableCallSite ICS(
&DereferenceableAA->getIRPosition().getAnchorValue());
if (ICS && CS.getInstruction() == ICS.getInstruction()) {
takeAssumedDerefBytesMinimum(
DereferenceableAA->getAssumedDereferenceableBytes());
IsNonNull &= DereferenceableAA->isAssumedNonNull();
IsGlobal &= DereferenceableAA->isAssumedGlobal();
return isValidState();
}
}
takeAssumedDerefBytesMinimum(computeAssumedDerefenceableBytes(
A, *CS.getArgOperand(ArgNo), IsNonNull, IsGlobal));
return isValidState();
};
if (!A.checkForAllCallSites(F, CallSiteCheck, *this, true))
return indicatePessimisticFixpoint();
updateAssumedNonNullGlobalState(IsNonNull, IsGlobal);
return BeforeState == static_cast<DerefState>(*this) ? ChangeStatus::UNCHANGED
: ChangeStatus::CHANGED;
}
/// Dereferenceable attribute for a call site argument.
struct AADereferenceableCallSiteArgument final : AADereferenceableImpl {
AADereferenceableCallSiteArgument(Instruction &I, unsigned ArgNo)
: AADereferenceableImpl(CallSite(&I).getArgOperand(ArgNo), I, ArgNo) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
CallSite CS(&getAnchorValue());
if (CS.paramHasAttr(getArgNo(), Attribute::Dereferenceable))
takeKnownDerefBytesMaximum(CS.getDereferenceableBytes(getArgNo()));
if (CS.paramHasAttr(getArgNo(), Attribute::DereferenceableOrNull))
takeKnownDerefBytesMaximum(CS.getDereferenceableOrNullBytes(getArgNo()));
}
/// See AbstractAttribute::updateImpl(Attributor &A).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_CSARG_ATTR(dereferenceable)
}
};
ChangeStatus AADereferenceableCallSiteArgument::updateImpl(Attributor &A) {
// NOTE: Never look at the argument of the callee in this method.
// If we do this, "dereferenceable" is always deduced because of the
// assumption.
Value &V = *getAssociatedValue();
auto BeforeState = static_cast<DerefState>(*this);
syncNonNull(A.getAAFor<AANonNull>(*this, getAnchorValue(), getArgNo()));
bool IsNonNull = isAssumedNonNull();
bool IsGlobal = isKnownGlobal();
takeAssumedDerefBytesMinimum(
computeAssumedDerefenceableBytes(A, V, IsNonNull, IsGlobal));
updateAssumedNonNullGlobalState(IsNonNull, IsGlobal);
return BeforeState == static_cast<DerefState>(*this) ? ChangeStatus::UNCHANGED
: ChangeStatus::CHANGED;
}
// ------------------------ Align Argument Attribute ------------------------
struct AAAlignImpl : AAAlign {
IRPositionConstructorForward(AAAlignImpl, AAAlign);
// Max alignemnt value allowed in IR
static const unsigned MAX_ALIGN = 1U << 29;
const std::string getAsStr() const override {
return getAssumedAlign() ? ("align<" + std::to_string(getKnownAlign()) +
"-" + std::to_string(getAssumedAlign()) + ">")
: "unknown-align";
}
/// See AbstractAttriubute::initialize(...).
void initialize(Attributor &A) override {
takeAssumedMinimum(MAX_ALIGN);
Function &F = getAnchorScope();
unsigned AttrIdx = getAttrIdx();
// Already the function has align attribute on return value or argument.
if (F.getAttributes().hasAttribute(AttrIdx, Attribute::Alignment))
addKnownBits(
F.getAttribute(AttrIdx, Attribute::Alignment).getAlignment());
}
/// See AbstractAttribute::getDeducedAttributes
virtual void
getDeducedAttributes(LLVMContext &Ctx,
SmallVectorImpl<Attribute> &Attrs) const override {
Attrs.emplace_back(Attribute::getWithAlignment(Ctx, getAssumedAlign()));
}
};
/// Align attribute for function return value.
struct AAAlignReturned final : AAAlignImpl {
AAAlignReturned(Function &F) : AAAlignImpl(F, IRP_RETURNED) {}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_FNRET_ATTR(aligned)
}
};
ChangeStatus AAAlignReturned::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
// Currently, align<n> is deduced if alignments in return values are assumed
// as greater than n. We reach pessimistic fixpoint if any of the return value
// wouldn't have align. If no assumed state was used for reasoning, an
// optimistic fixpoint is reached earlier.
base_t BeforeState = getAssumed();
auto CheckReturnValue =
[&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &RetInsts) -> bool {
auto *AlignAA = A.getAAFor<AAAlign>(*this, RV);
if (AlignAA)
takeAssumedMinimum(AlignAA->getAssumedAlign());
else
// Use IR information.
takeAssumedMinimum(RV.getPointerAlignment(A.getDataLayout()));
return isValidState();
};
if (!A.checkForAllReturnedValuesAndReturnInsts(F, CheckReturnValue, *this))
return indicatePessimisticFixpoint();
return (getAssumed() != BeforeState) ? ChangeStatus::CHANGED
: ChangeStatus::UNCHANGED;
}
/// Align attribute for function argument.
struct AAAlignArgument final : AAAlignImpl {
AAAlignArgument(Argument &A) : AAAlignImpl(A) {}
/// See AbstractAttribute::updateImpl(...).
virtual ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override{STATS_DECL_AND_TRACK_ARG_ATTR(aligned)};
};
ChangeStatus AAAlignArgument::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
Argument &Arg = cast<Argument>(getAnchorValue());
unsigned ArgNo = Arg.getArgNo();
const DataLayout &DL = A.getDataLayout();
auto BeforeState = getAssumed();
// Callback function
std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) {
assert(CS && "Sanity check: Call site was not initialized properly!");
auto *AlignAA = A.getAAFor<AAAlign>(*this, *CS.getInstruction(), ArgNo);
// Check that AlignAA is AAAlignCallSiteArgument.
if (AlignAA) {
ImmutableCallSite ICS(&AlignAA->getIRPosition().getAnchorValue());
if (ICS && CS.getInstruction() == ICS.getInstruction()) {
takeAssumedMinimum(AlignAA->getAssumedAlign());
return isValidState();
}
}
Value *V = CS.getArgOperand(ArgNo);
takeAssumedMinimum(V->getPointerAlignment(DL));
return isValidState();
};
if (!A.checkForAllCallSites(F, CallSiteCheck, *this, true))
indicatePessimisticFixpoint();
return BeforeState == getAssumed() ? ChangeStatus::UNCHANGED
: ChangeStatus ::CHANGED;
}
struct AAAlignCallSiteArgument final : AAAlignImpl {
AAAlignCallSiteArgument(Instruction &I, unsigned ArgNo)
: AAAlignImpl(CallSite(&I).getArgOperand(ArgNo), I, ArgNo) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
CallSite CS(&getAnchorValue());
takeKnownMaximum(
getAssociatedValue()->getPointerAlignment(A.getDataLayout()));
}
/// See AbstractAttribute::updateImpl(Attributor &A).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_CSARG_ATTR(aligned)
}
};
ChangeStatus AAAlignCallSiteArgument::updateImpl(Attributor &A) {
// NOTE: Never look at the argument of the callee in this method.
// If we do this, "align" is always deduced because of the assumption.
auto BeforeState = getAssumed();
Value &V = *getAssociatedValue();
auto *AlignAA = A.getAAFor<AAAlign>(*this, V);
if (AlignAA)
takeAssumedMinimum(AlignAA->getAssumedAlign());
else
indicatePessimisticFixpoint();
return BeforeState == getAssumed() ? ChangeStatus::UNCHANGED
: ChangeStatus::CHANGED;
}
/// ------------------ Function No-Return Attribute ----------------------------
struct AANoReturnImpl : public AANoReturn {
IRPositionConstructorForward(AANoReturnImpl, AANoReturn);
/// See AbstractAttribute::getAsStr().
const std::string getAsStr() const override {
return getAssumed() ? "noreturn" : "may-return";
}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
Function &F = getAnchorScope();
if (F.hasFnAttribute(getAttrKind()))
indicateOptimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(Attributor &A).
virtual ChangeStatus updateImpl(Attributor &A) override {
const Function &F = getAnchorScope();
auto CheckForNoReturn = [](Instruction &) { return false; };
if (!A.checkForAllInstructions(F, CheckForNoReturn, *this,
{(unsigned)Instruction::Ret}))
return indicatePessimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
};
struct AANoReturnFunction final : AANoReturnImpl {
AANoReturnFunction(Function &F) : AANoReturnImpl(F, IRP_FUNCTION) {}
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
STATS_DECL_AND_TRACK_FN_ATTR(noreturn)
}
};
/// ----------------------------------------------------------------------------
/// Attributor
/// ----------------------------------------------------------------------------
bool Attributor::checkForAllCallSites(Function &F,
std::function<bool(CallSite)> &Pred,
const AbstractAttribute &QueryingAA,
bool RequireAllCallSites) {
// We can try to determine information from
// the call sites. However, this is only possible all call sites are known,
// hence the function has internal linkage.
if (RequireAllCallSites && !F.hasInternalLinkage()) {
LLVM_DEBUG(
dbgs()
<< "Attributor: Function " << F.getName()
<< " has no internal linkage, hence not all call sites are known\n");
return false;
}
for (const Use &U : F.uses()) {
Instruction *I = cast<Instruction>(U.getUser());
Function *AnchorValue = I->getParent()->getParent();
auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, *AnchorValue);
// Skip dead calls.
if (LivenessAA && LivenessAA->isAssumedDead(I))
continue;
CallSite CS(U.getUser());
if (!CS || !CS.isCallee(&U) || !CS.getCaller()->hasExactDefinition()) {
if (!RequireAllCallSites)
continue;
LLVM_DEBUG(dbgs() << "Attributor: User " << *U.getUser()
<< " is an invalid use of " << F.getName() << "\n");
return false;
}
if (Pred(CS))
continue;
LLVM_DEBUG(dbgs() << "Attributor: Call site callback failed for "
<< *CS.getInstruction() << "\n");
return false;
}
return true;
}
bool Attributor::checkForAllReturnedValuesAndReturnInsts(
const Function &F,
const function_ref<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
&Pred,
const AbstractAttribute &QueryingAA) {
auto *AARetVal = getAAFor<AAReturnedValues>(QueryingAA, F);
if (!AARetVal)
return false;
auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);
if (!LivenessAA)
return AARetVal->checkForAllReturnedValuesAndReturnInsts(Pred);
auto LivenessFilter = [&](Value &RV,
const SmallPtrSetImpl<ReturnInst *> &ReturnInsts) {
SmallPtrSet<ReturnInst *, 4> FilteredReturnInsts;
for (ReturnInst *RI : ReturnInsts)
if (!LivenessAA->isAssumedDead(RI))
FilteredReturnInsts.insert(RI);
if (!FilteredReturnInsts.empty())
return Pred(RV, FilteredReturnInsts);
return true;
};
return AARetVal->checkForAllReturnedValuesAndReturnInsts(LivenessFilter);
}
bool Attributor::checkForAllReturnedValues(
const Function &F, const function_ref<bool(Value &)> &Pred,
const AbstractAttribute &QueryingAA) {
auto *AARetVal = getAAFor<AAReturnedValues>(QueryingAA, F);
if (!AARetVal)
return false;
auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);
if (!LivenessAA)
return AARetVal->checkForAllReturnedValuesAndReturnInsts(
[&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &) {
return Pred(RV);
});
auto LivenessFilter = [&](Value &RV,
const SmallPtrSetImpl<ReturnInst *> &ReturnInsts) {
if (LivenessAA->isLiveInstSet(ReturnInsts.begin(), ReturnInsts.end()))
return Pred(RV);
return true;
};
return AARetVal->checkForAllReturnedValuesAndReturnInsts(LivenessFilter);
}
bool Attributor::checkForAllInstructions(
const Function &F, const llvm::function_ref<bool(Instruction &)> &Pred,
const AbstractAttribute &QueryingAA, const ArrayRef<unsigned> &Opcodes) {
auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);
auto &OpcodeInstMap = InfoCache.getOpcodeInstMapForFunction(F);
for (unsigned Opcode : Opcodes) {
for (Instruction *I : OpcodeInstMap[Opcode]) {
// Skip dead instructions.
if (LivenessAA && LivenessAA->isAssumedDead(I))
continue;
if (!Pred(*I))
return false;
}
}
return true;
}
bool Attributor::checkForAllReadWriteInstructions(
const Function &F, const llvm::function_ref<bool(Instruction &)> &Pred,
AbstractAttribute &QueryingAA) {
auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);
for (Instruction *I : InfoCache.getReadOrWriteInstsForFunction(F)) {
// Skip dead instructions.
if (LivenessAA && LivenessAA->isAssumedDead(I))
continue;
if (!Pred(*I))
return false;
}
return true;
}
ChangeStatus Attributor::run() {
// Initialize all abstract attributes.
for (AbstractAttribute *AA : AllAbstractAttributes)
AA->initialize(*this);
LLVM_DEBUG(dbgs() << "[Attributor] Identified and initialized "
<< AllAbstractAttributes.size()
<< " abstract attributes.\n");
// Now that all abstract attributes are collected and initialized we start
// the abstract analysis.
unsigned IterationCounter = 1;
SmallVector<AbstractAttribute *, 64> ChangedAAs;
SetVector<AbstractAttribute *> Worklist;
Worklist.insert(AllAbstractAttributes.begin(), AllAbstractAttributes.end());
do {
LLVM_DEBUG(dbgs() << "\n\n[Attributor] #Iteration: " << IterationCounter
<< ", Worklist size: " << Worklist.size() << "\n");
// Add all abstract attributes that are potentially dependent on one that
// changed to the work list.
for (AbstractAttribute *ChangedAA : ChangedAAs) {
auto &QuerriedAAs = QueryMap[ChangedAA];
Worklist.insert(QuerriedAAs.begin(), QuerriedAAs.end());
}
// Reset the changed set.
ChangedAAs.clear();
// Update all abstract attribute in the work list and record the ones that
// changed.
for (AbstractAttribute *AA : Worklist)
if (AA->update(*this) == ChangeStatus::CHANGED)
ChangedAAs.push_back(AA);
// Reset the work list and repopulate with the changed abstract attributes.
// Note that dependent ones are added above.
Worklist.clear();
Worklist.insert(ChangedAAs.begin(), ChangedAAs.end());
} while (!Worklist.empty() && ++IterationCounter < MaxFixpointIterations);
LLVM_DEBUG(dbgs() << "\n[Attributor] Fixpoint iteration done after: "
<< IterationCounter << "/" << MaxFixpointIterations
<< " iterations\n");
bool FinishedAtFixpoint = Worklist.empty();
// Reset abstract arguments not settled in a sound fixpoint by now. This
// happens when we stopped the fixpoint iteration early. Note that only the
// ones marked as "changed" *and* the ones transitively depending on them
// need to be reverted to a pessimistic state. Others might not be in a
// fixpoint state but we can use the optimistic results for them anyway.
SmallPtrSet<AbstractAttribute *, 32> Visited;
for (unsigned u = 0; u < ChangedAAs.size(); u++) {
AbstractAttribute *ChangedAA = ChangedAAs[u];
if (!Visited.insert(ChangedAA).second)
continue;
AbstractState &State = ChangedAA->getState();
if (!State.isAtFixpoint()) {
State.indicatePessimisticFixpoint();
NumAttributesTimedOut++;
}
auto &QuerriedAAs = QueryMap[ChangedAA];
ChangedAAs.append(QuerriedAAs.begin(), QuerriedAAs.end());
}
LLVM_DEBUG({
if (!Visited.empty())
dbgs() << "\n[Attributor] Finalized " << Visited.size()
<< " abstract attributes.\n";
});
unsigned NumManifested = 0;
unsigned NumAtFixpoint = 0;
ChangeStatus ManifestChange = ChangeStatus::UNCHANGED;
for (AbstractAttribute *AA : AllAbstractAttributes) {
AbstractState &State = AA->getState();
// If there is not already a fixpoint reached, we can now take the
// optimistic state. This is correct because we enforced a pessimistic one
// on abstract attributes that were transitively dependent on a changed one
// already above.
if (!State.isAtFixpoint())
State.indicateOptimisticFixpoint();
// If the state is invalid, we do not try to manifest it.
if (!State.isValidState())
continue;
// Manifest the state and record if we changed the IR.
ChangeStatus LocalChange = AA->manifest(*this);
if (LocalChange == ChangeStatus::CHANGED && AreStatisticsEnabled())
AA->trackStatistics();
ManifestChange = ManifestChange | LocalChange;
NumAtFixpoint++;
NumManifested += (LocalChange == ChangeStatus::CHANGED);
}
(void)NumManifested;
(void)NumAtFixpoint;
LLVM_DEBUG(dbgs() << "\n[Attributor] Manifested " << NumManifested
<< " arguments while " << NumAtFixpoint
<< " were in a valid fixpoint state\n");
// If verification is requested, we finished this run at a fixpoint, and the
// IR was changed, we re-run the whole fixpoint analysis, starting at
// re-initialization of the arguments. This re-run should not result in an IR
// change. Though, the (virtual) state of attributes at the end of the re-run
// might be more optimistic than the known state or the IR state if the better
// state cannot be manifested.
if (VerifyAttributor && FinishedAtFixpoint &&
ManifestChange == ChangeStatus::CHANGED) {
VerifyAttributor = false;
ChangeStatus VerifyStatus = run();
if (VerifyStatus != ChangeStatus::UNCHANGED)
llvm_unreachable(
"Attributor verification failed, re-run did result in an IR change "
"even after a fixpoint was reached in the original run. (False "
"positives possible!)");
VerifyAttributor = true;
}
NumAttributesManifested += NumManifested;
NumAttributesValidFixpoint += NumAtFixpoint;
return ManifestChange;
}
/// Helper function that checks if an abstract attribute of type \p AAType
/// should be created for \p V (with argument number \p ArgNo) and if so creates
/// and registers it with the Attributor \p A.
///
/// This method will look at the provided whitelist. If one is given and the
/// kind \p AAType::ID is not contained, no abstract attribute is created.
///
/// \returns The created abstract argument, or nullptr if none was created.
template <typename AAType, typename ValueType, typename... ArgsTy>
static AAType *checkAndRegisterAA(const Function &F, Attributor &A,
DenseSet<const char *> *Whitelist,
ValueType &V, int ArgNo, ArgsTy... Args) {
if (Whitelist && !Whitelist->count(&AAType::ID))
return nullptr;
return &A.registerAA<AAType>(*new AAType(V, Args...), ArgNo);
}
void Attributor::identifyDefaultAbstractAttributes(
Function &F, DenseSet<const char *> *Whitelist) {
// Check for dead BasicBlocks in every function.
// We need dead instruction detection because we do not want to deal with
// broken IR in which SSA rules do not apply.
checkAndRegisterAA<AAIsDeadFunction>(F, *this, /* Whitelist */ nullptr, F,
-1);
// Every function might be "will-return".
checkAndRegisterAA<AAWillReturnFunction>(F, *this, Whitelist, F, -1);
// Every function can be nounwind.
checkAndRegisterAA<AANoUnwindFunction>(F, *this, Whitelist, F, -1);
// Every function might be marked "nosync"
checkAndRegisterAA<AANoSyncFunction>(F, *this, Whitelist, F, -1);
// Every function might be "no-free".
checkAndRegisterAA<AANoFreeFunction>(F, *this, Whitelist, F, -1);
// Every function might be "no-return".
checkAndRegisterAA<AANoReturnFunction>(F, *this, Whitelist, F, -1);
// Return attributes are only appropriate if the return type is non void.
Type *ReturnType = F.getReturnType();
if (!ReturnType->isVoidTy()) {
// Argument attribute "returned" --- Create only one per function even
// though it is an argument attribute.
checkAndRegisterAA<AAReturnedValuesFunction>(F, *this, Whitelist, F, -1);
if (ReturnType->isPointerTy()) {
// Every function with pointer return type might be marked align.
checkAndRegisterAA<AAAlignReturned>(F, *this, Whitelist, F, -1);
// Every function with pointer return type might be marked nonnull.
checkAndRegisterAA<AANonNullReturned>(F, *this, Whitelist, F, -1);
// Every function with pointer return type might be marked noalias.
checkAndRegisterAA<AANoAliasReturned>(F, *this, Whitelist, F, -1);
// Every function with pointer return type might be marked
// dereferenceable.
checkAndRegisterAA<AADereferenceableReturned>(F, *this, Whitelist, F, -1);
}
}
for (Argument &Arg : F.args()) {
if (Arg.getType()->isPointerTy()) {
// Every argument with pointer type might be marked nonnull.
checkAndRegisterAA<AANonNullArgument>(F, *this, Whitelist, Arg,
Arg.getArgNo());
// Every argument with pointer type might be marked dereferenceable.
checkAndRegisterAA<AADereferenceableArgument>(F, *this, Whitelist, Arg,
Arg.getArgNo());
// Every argument with pointer type might be marked align.
checkAndRegisterAA<AAAlignArgument>(F, *this, Whitelist, Arg,
Arg.getArgNo());
}
}
// Walk all instructions to find more attribute opportunities and also
// interesting instructions that might be queried by abstract attributes
// during their initialization or update.
auto &ReadOrWriteInsts = InfoCache.FuncRWInstsMap[&F];
auto &InstOpcodeMap = InfoCache.FuncInstOpcodeMap[&F];
for (Instruction &I : instructions(&F)) {
bool IsInterestingOpcode = false;
// To allow easy access to all instructions in a function with a given
// opcode we store them in the InfoCache. As not all opcodes are interesting
// to concrete attributes we only cache the ones that are as identified in
// the following switch.
// Note: There are no concrete attributes now so this is initially empty.
switch (I.getOpcode()) {
default:
assert((!ImmutableCallSite(&I)) && (!isa<CallBase>(&I)) &&
"New call site/base instruction type needs to be known int the "
"attributor.");
break;
case Instruction::Call:
case Instruction::CallBr:
case Instruction::Invoke:
case Instruction::CleanupRet:
case Instruction::CatchSwitch:
case Instruction::Resume:
case Instruction::Ret:
IsInterestingOpcode = true;
}
if (IsInterestingOpcode)
InstOpcodeMap[I.getOpcode()].push_back(&I);
if (I.mayReadOrWriteMemory())
ReadOrWriteInsts.push_back(&I);
CallSite CS(&I);
if (CS && CS.getCalledFunction()) {
for (int i = 0, e = CS.getCalledFunction()->arg_size(); i < e; i++) {
if (!CS.getArgument(i)->getType()->isPointerTy())
continue;
// Call site argument attribute "non-null".
checkAndRegisterAA<AANonNullCallSiteArgument>(F, *this, Whitelist, I, i,
i);
// Call site argument attribute "dereferenceable".
checkAndRegisterAA<AADereferenceableCallSiteArgument>(
F, *this, Whitelist, I, i, i);
// Call site argument attribute "align".
checkAndRegisterAA<AAAlignCallSiteArgument>(F, *this, Whitelist, I, i,
i);
}
}
}
}
/// Helpers to ease debugging through output streams and print calls.
///
///{
raw_ostream &llvm::operator<<(raw_ostream &OS, ChangeStatus S) {
return OS << (S == ChangeStatus::CHANGED ? "changed" : "unchanged");
}
raw_ostream &llvm::operator<<(raw_ostream &OS, IRPosition::Kind AP) {
switch (AP) {
case IRPosition::IRP_ARGUMENT:
return OS << "arg";
case IRPosition::IRP_CALL_SITE_ARGUMENT:
return OS << "cs_arg";
case IRPosition::IRP_FUNCTION:
return OS << "fn";
case IRPosition::IRP_RETURNED:
return OS << "fn_ret";
}
llvm_unreachable("Unknown attribute position!");
}
raw_ostream &llvm::operator<<(raw_ostream &OS, const IRPosition &Pos) {
const Value *AV = Pos.getAssociatedValue();
return OS << "{" << Pos.getPositionKind() << ":"
<< (AV ? AV->getName() : "n/a") << " ["
<< Pos.getAnchorValue().getName() << "@" << Pos.getArgNo() << "]}";
}
raw_ostream &llvm::operator<<(raw_ostream &OS, const IntegerState &S) {
return OS << "(" << S.getKnown() << "-" << S.getAssumed() << ")"
<< static_cast<const AbstractState &>(S);
}
raw_ostream &llvm::operator<<(raw_ostream &OS, const AbstractState &S) {
return OS << (!S.isValidState() ? "top" : (S.isAtFixpoint() ? "fix" : ""));
}
raw_ostream &llvm::operator<<(raw_ostream &OS, const AbstractAttribute &AA) {
AA.print(OS);
return OS;
}
void AbstractAttribute::print(raw_ostream &OS) const {
OS << "[P: " << getIRPosition() << "][" << getAsStr() << "][S: " << getState()
<< "]";
}
///}
/// ----------------------------------------------------------------------------
/// Pass (Manager) Boilerplate
/// ----------------------------------------------------------------------------
static bool runAttributorOnModule(Module &M) {
if (DisableAttributor)
return false;
LLVM_DEBUG(dbgs() << "[Attributor] Run on module with " << M.size()
<< " functions.\n");
// Create an Attributor and initially empty information cache that is filled
// while we identify default attribute opportunities.
InformationCache InfoCache(M.getDataLayout());
Attributor A(InfoCache);
for (Function &F : M) {
// TODO: Not all attributes require an exact definition. Find a way to
// enable deduction for some but not all attributes in case the
// definition might be changed at runtime, see also
// http://lists.llvm.org/pipermail/llvm-dev/2018-February/121275.html.
// TODO: We could always determine abstract attributes and if sufficient
// information was found we could duplicate the functions that do not
// have an exact definition.
if (!F.hasExactDefinition()) {
NumFnWithoutExactDefinition++;
continue;
}
// For now we ignore naked and optnone functions.
if (F.hasFnAttribute(Attribute::Naked) ||
F.hasFnAttribute(Attribute::OptimizeNone))
continue;
NumFnWithExactDefinition++;
// Populate the Attributor with abstract attribute opportunities in the
// function and the information cache with IR information.
A.identifyDefaultAbstractAttributes(F);
}
return A.run() == ChangeStatus::CHANGED;
}
PreservedAnalyses AttributorPass::run(Module &M, ModuleAnalysisManager &AM) {
if (runAttributorOnModule(M)) {
// FIXME: Think about passes we will preserve and add them here.
return PreservedAnalyses::none();
}
return PreservedAnalyses::all();
}
namespace {
struct AttributorLegacyPass : public ModulePass {
static char ID;
AttributorLegacyPass() : ModulePass(ID) {
initializeAttributorLegacyPassPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &M) override {
if (skipModule(M))
return false;
return runAttributorOnModule(M);
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
// FIXME: Think about passes we will preserve and add them here.
AU.setPreservesCFG();
}
};
} // end anonymous namespace
Pass *llvm::createAttributorLegacyPass() { return new AttributorLegacyPass(); }
char AttributorLegacyPass::ID = 0;
const char AAReturnedValues::ID = 0;
const char AANoUnwind::ID = 0;
const char AANoSync::ID = 0;
const char AANoFree::ID = 0;
const char AANonNull::ID = 0;
const char AANoRecurse::ID = 0;
const char AAWillReturn::ID = 0;
const char AANoAlias::ID = 0;
const char AANoReturn::ID = 0;
const char AAIsDead::ID = 0;
const char AADereferenceable::ID = 0;
const char AAAlign::ID = 0;
INITIALIZE_PASS_BEGIN(AttributorLegacyPass, "attributor",
"Deduce and propagate attributes", false, false)
INITIALIZE_PASS_END(AttributorLegacyPass, "attributor",
"Deduce and propagate attributes", false, false)
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