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llvm-project/llvm/lib/Transforms/IPO/Attributor.cpp
Johannes Doerfert da4d811707 [Attributor][FIX] Indicate a missing update change 
User of AAReturnedValues need to know if HasOverdefinedReturnedCalls
changed from false to true as it will impact the result of the return
value traversal (calls are not ignored anymore).

This will be tested with the tests in D59978.

llvm-svn: 367581
2019-08-01 16:21:54 +00:00

2621 lines
86 KiB
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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/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");
STATISTIC(NumFnNoUnwind, "Number of functions marked nounwind");
STATISTIC(NumFnUniqueReturned, "Number of function with unique return");
STATISTIC(NumFnKnownReturns, "Number of function with known return values");
STATISTIC(NumFnArgumentReturned,
"Number of function arguments marked returned");
STATISTIC(NumFnNoSync, "Number of functions marked nosync");
STATISTIC(NumFnNoFree, "Number of functions marked nofree");
STATISTIC(NumFnReturnedNonNull,
"Number of function return values marked nonnull");
STATISTIC(NumFnArgumentNonNull, "Number of function arguments marked nonnull");
STATISTIC(NumCSArgumentNonNull, "Number of call site arguments marked nonnull");
STATISTIC(NumFnWillReturn, "Number of functions marked willreturn");
STATISTIC(NumFnArgumentNoAlias, "Number of function arguments marked noalias");
STATISTIC(NumFnReturnedDereferenceable,
"Number of function return values marked dereferenceable");
STATISTIC(NumFnArgumentDereferenceable,
"Number of function arguments marked dereferenceable");
STATISTIC(NumCSArgumentDereferenceable,
"Number of call site arguments marked dereferenceable");
STATISTIC(NumFnReturnedAlign, "Number of function return values marked align");
STATISTIC(NumFnArgumentAlign, "Number of function arguments marked align");
STATISTIC(NumCSArgumentAlign, "Number of call site arguments marked align");
// 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;
}
///}
/// Helper to adjust the statistics.
static void bookkeeping(AbstractAttribute::ManifestPosition MP,
const Attribute &Attr) {
if (!AreStatisticsEnabled())
return;
switch (Attr.getKindAsEnum()) {
case Attribute::Alignment:
switch (MP) {
case AbstractAttribute::MP_RETURNED:
NumFnReturnedAlign++;
break;
case AbstractAttribute::MP_ARGUMENT:
NumFnArgumentAlign++;
break;
case AbstractAttribute::MP_CALL_SITE_ARGUMENT:
NumCSArgumentAlign++;
break;
default:
break;
}
break;
case Attribute::Dereferenceable:
switch (MP) {
case AbstractAttribute::MP_RETURNED:
NumFnReturnedDereferenceable++;
break;
case AbstractAttribute::MP_ARGUMENT:
NumFnArgumentDereferenceable++;
break;
case AbstractAttribute::MP_CALL_SITE_ARGUMENT:
NumCSArgumentDereferenceable++;
break;
default:
break;
}
break;
case Attribute::NoUnwind:
NumFnNoUnwind++;
return;
case Attribute::Returned:
NumFnArgumentReturned++;
return;
case Attribute::NoSync:
NumFnNoSync++;
break;
case Attribute::NoFree:
NumFnNoFree++;
break;
case Attribute::NonNull:
switch (MP) {
case AbstractAttribute::MP_RETURNED:
NumFnReturnedNonNull++;
break;
case AbstractAttribute::MP_ARGUMENT:
NumFnArgumentNonNull++;
break;
case AbstractAttribute::MP_CALL_SITE_ARGUMENT:
NumCSArgumentNonNull++;
break;
default:
break;
}
break;
case Attribute::WillReturn:
NumFnWillReturn++;
break;
case Attribute::NoAlias:
NumFnArgumentNoAlias++;
return;
default:
return;
}
}
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;
}
/// Helper to identify the correct offset into an attribute list.
static unsigned getAttrIndex(AbstractAttribute::ManifestPosition MP,
unsigned ArgNo = 0) {
switch (MP) {
case AbstractAttribute::MP_ARGUMENT:
case AbstractAttribute::MP_CALL_SITE_ARGUMENT:
return ArgNo + AttributeList::FirstArgIndex;
case AbstractAttribute::MP_FUNCTION:
return AttributeList::FunctionIndex;
case AbstractAttribute::MP_RETURNED:
return AttributeList::ReturnIndex;
}
llvm_unreachable("Unknown manifest position!");
}
/// 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 MP and \p ArgNo.
static bool addIfNotExistent(LLVMContext &Ctx, const Attribute &Attr,
AttributeList &Attrs,
AbstractAttribute::ManifestPosition MP,
unsigned ArgNo = 0) {
unsigned AttrIdx = getAttrIndex(MP, ArgNo);
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 AbstractAttribute::manifest(Attributor &A) {
assert(getState().isValidState() &&
"Attempted to manifest an invalid state!");
assert(getAssociatedValue() &&
"Attempted to manifest an attribute without associated value!");
ChangeStatus HasChanged = ChangeStatus::UNCHANGED;
SmallVector<Attribute, 4> DeducedAttrs;
getDeducedAttributes(DeducedAttrs);
Function &ScopeFn = getAnchorScope();
LLVMContext &Ctx = ScopeFn.getContext();
ManifestPosition MP = getManifestPosition();
AttributeList Attrs;
SmallVector<unsigned, 4> ArgNos;
// 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.
// Note that MP_CALL_SITE_ARGUMENT can annotate multiple locations.
switch (MP) {
case MP_ARGUMENT:
ArgNos.push_back(cast<Argument>(getAssociatedValue())->getArgNo());
Attrs = ScopeFn.getAttributes();
break;
case MP_FUNCTION:
case MP_RETURNED:
ArgNos.push_back(0);
Attrs = ScopeFn.getAttributes();
break;
case MP_CALL_SITE_ARGUMENT: {
CallSite CS(&getAnchoredValue());
for (unsigned u = 0, e = CS.getNumArgOperands(); u != e; u++)
if (CS.getArgOperand(u) == getAssociatedValue())
ArgNos.push_back(u);
Attrs = CS.getAttributes();
}
}
for (const Attribute &Attr : DeducedAttrs) {
for (unsigned ArgNo : ArgNos) {
if (!addIfNotExistent(Ctx, Attr, Attrs, MP, ArgNo))
continue;
HasChanged = ChangeStatus::CHANGED;
bookkeeping(MP, Attr);
}
}
if (HasChanged == ChangeStatus::UNCHANGED)
return HasChanged;
switch (MP) {
case MP_ARGUMENT:
case MP_FUNCTION:
case MP_RETURNED:
ScopeFn.setAttributes(Attrs);
break;
case MP_CALL_SITE_ARGUMENT:
CallSite(&getAnchoredValue()).setAttributes(Attrs);
}
return HasChanged;
}
Function &AbstractAttribute::getAnchorScope() {
Value &V = getAnchoredValue();
if (isa<Function>(V))
return cast<Function>(V);
if (isa<Argument>(V))
return *cast<Argument>(V).getParent();
if (isa<Instruction>(V))
return *cast<Instruction>(V).getFunction();
llvm_unreachable("No scope for anchored value found!");
}
const Function &AbstractAttribute::getAnchorScope() const {
return const_cast<AbstractAttribute *>(this)->getAnchorScope();
}
// Helper function that returns argument index of value.
// If the value is not an argument, this returns -1.
static int getArgNo(Value &V) {
if (auto *Arg = dyn_cast<Argument>(&V))
return Arg->getArgNo();
return -1;
}
/// -----------------------NoUnwind Function Attribute--------------------------
struct AANoUnwindFunction : AANoUnwind, BooleanState {
AANoUnwindFunction(Function &F, InformationCache &InfoCache)
: AANoUnwind(F, InfoCache) {}
/// See AbstractAttribute::getState()
/// {
AbstractState &getState() override { return *this; }
const AbstractState &getState() const override { return *this; }
/// }
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override { return MP_FUNCTION; }
const std::string getAsStr() const override {
return getAssumed() ? "nounwind" : "may-unwind";
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AANoUnwind::isAssumedNoUnwind().
bool isAssumedNoUnwind() const override { return getAssumed(); }
/// See AANoUnwind::isKnownNoUnwind().
bool isKnownNoUnwind() const override { return getKnown(); }
};
ChangeStatus AANoUnwindFunction::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
// The map from instruction opcodes to those instructions in the function.
auto &OpcodeInstMap = InfoCache.getOpcodeInstMapForFunction(F);
auto Opcodes = {
(unsigned)Instruction::Invoke, (unsigned)Instruction::CallBr,
(unsigned)Instruction::Call, (unsigned)Instruction::CleanupRet,
(unsigned)Instruction::CatchSwitch, (unsigned)Instruction::Resume};
for (unsigned Opcode : Opcodes) {
for (Instruction *I : OpcodeInstMap[Opcode]) {
if (!I->mayThrow())
continue;
auto *NoUnwindAA = A.getAAFor<AANoUnwind>(*this, *I);
if (!NoUnwindAA || !NoUnwindAA->isAssumedNoUnwind()) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
}
}
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.
class AAReturnedValuesImpl final : public AAReturnedValues, 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:
/// See AbstractAttribute::AbstractAttribute(...).
AAReturnedValuesImpl(Function &F, InformationCache &InfoCache)
: AAReturnedValues(F, InfoCache) {
// We do not have an associated argument yet.
AssociatedVal = nullptr;
}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
// Reset the state.
AssociatedVal = nullptr;
IsFixed = false;
IsValidState = true;
HasOverdefinedReturnedCalls = false;
ReturnedValues.clear();
Function &F = cast<Function>(getAnchoredValue());
// The map from instruction opcodes to those instructions in the function.
auto &OpcodeInstMap = InfoCache.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::getManifestPosition().
ManifestPosition getManifestPosition() const override { return MP_ARGUMENT; }
/// 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() const;
/// See AbstractState::checkForallReturnedValues(...).
bool
checkForallReturnedValues(std::function<bool(Value &)> &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(...).
void indicateOptimisticFixpoint() override {
IsFixed = true;
IsValidState &= true;
}
void indicatePessimisticFixpoint() override {
IsFixed = true;
IsValidState = false;
}
};
ChangeStatus AAReturnedValuesImpl::manifest(Attributor &A) {
ChangeStatus Changed = ChangeStatus::UNCHANGED;
// Bookkeeping.
assert(isValidState());
NumFnKnownReturns++;
// Check if we have an assumed unique return value that we could manifest.
Optional<Value *> UniqueRV = getAssumedUniqueReturnValue();
if (!UniqueRV.hasValue() || !UniqueRV.getValue())
return Changed;
// Bookkeeping.
NumFnUniqueReturned++;
// If the assumed unique return value is an argument, annotate it.
if (auto *UniqueRVArg = dyn_cast<Argument>(UniqueRV.getValue())) {
AssociatedVal = UniqueRVArg;
Changed = AbstractAttribute::manifest(A) | Changed;
}
return Changed;
}
const std::string AAReturnedValuesImpl::getAsStr() const {
return (isAtFixpoint() ? "returns(#" : "may-return(#") +
(isValidState() ? std::to_string(getNumReturnValues()) : "?") + ")";
}
Optional<Value *> AAReturnedValuesImpl::getAssumedUniqueReturnValue() 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;
std::function<bool(Value &)> 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 (!checkForallReturnedValues(Pred))
UniqueRV = nullptr;
return UniqueRV;
}
bool AAReturnedValuesImpl::checkForallReturnedValues(
std::function<bool(Value &)> &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;
ImmutableCallSite ICS(RV);
if (ICS && !HasOverdefinedReturnedCalls)
continue;
if (!Pred(*RV))
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;
// 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;
// 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();
// 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 AANoSyncFunction : AANoSync, BooleanState {
AANoSyncFunction(Function &F, InformationCache &InfoCache)
: AANoSync(F, InfoCache) {}
/// See AbstractAttribute::getState()
/// {
AbstractState &getState() override { return *this; }
const AbstractState &getState() const override { return *this; }
/// }
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override { return MP_FUNCTION; }
const std::string getAsStr() const override {
return getAssumed() ? "nosync" : "may-sync";
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AANoSync::isAssumedNoSync()
bool isAssumedNoSync() const override { return getAssumed(); }
/// See AANoSync::isKnownNoSync()
bool isKnownNoSync() const override { return getKnown(); }
/// 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);
};
bool AANoSyncFunction::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 AANoSyncFunction::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 AANoSyncFunction::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 AANoSyncFunction::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
/// We are looking for volatile instructions or Non-Relaxed atomics.
/// FIXME: We should ipmrove the handling of intrinsics.
for (Instruction *I : InfoCache.getReadOrWriteInstsForFunction(F)) {
ImmutableCallSite ICS(I);
auto *NoSyncAA = A.getAAFor<AANoSyncFunction>(*this, *I);
if (isa<IntrinsicInst>(I) && isNoSyncIntrinsic(I))
continue;
if (ICS && (!NoSyncAA || !NoSyncAA->isAssumedNoSync()) &&
!ICS.hasFnAttr(Attribute::NoSync)) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
if (ICS)
continue;
if (!isVolatile(I) && !isNonRelaxedAtomic(I))
continue;
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
auto &OpcodeInstMap = InfoCache.getOpcodeInstMapForFunction(F);
auto Opcodes = {(unsigned)Instruction::Invoke, (unsigned)Instruction::CallBr,
(unsigned)Instruction::Call};
for (unsigned Opcode : Opcodes) {
for (Instruction *I : OpcodeInstMap[Opcode]) {
// At this point we handled all read/write effects and they are all
// nosync, so they can be skipped.
if (I->mayReadOrWriteMemory())
continue;
ImmutableCallSite ICS(I);
// non-convergent and readnone imply nosync.
if (!ICS.isConvergent())
continue;
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
}
return ChangeStatus::UNCHANGED;
}
/// ------------------------ No-Free Attributes ----------------------------
struct AANoFreeFunction : AbstractAttribute, BooleanState {
/// See AbstractAttribute::AbstractAttribute(...).
AANoFreeFunction(Function &F, InformationCache &InfoCache)
: AbstractAttribute(F, InfoCache) {}
/// See AbstractAttribute::getState()
///{
AbstractState &getState() override { return *this; }
const AbstractState &getState() const override { return *this; }
///}
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override { return MP_FUNCTION; }
/// See AbstractAttribute::getAsStr().
const std::string getAsStr() const override {
return getAssumed() ? "nofree" : "may-free";
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::getAttrKind().
Attribute::AttrKind getAttrKind() const override { return ID; }
/// Return true if "nofree" is assumed.
bool isAssumedNoFree() const { return getAssumed(); }
/// Return true if "nofree" is known.
bool isKnownNoFree() const { return getKnown(); }
/// The identifier used by the Attributor for this class of attributes.
static constexpr Attribute::AttrKind ID = Attribute::NoFree;
};
ChangeStatus AANoFreeFunction::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
// The map from instruction opcodes to those instructions in the function.
auto &OpcodeInstMap = InfoCache.getOpcodeInstMapForFunction(F);
for (unsigned Opcode :
{(unsigned)Instruction::Invoke, (unsigned)Instruction::CallBr,
(unsigned)Instruction::Call}) {
for (Instruction *I : OpcodeInstMap[Opcode]) {
auto ICS = ImmutableCallSite(I);
auto *NoFreeAA = A.getAAFor<AANoFreeFunction>(*this, *I);
if ((!NoFreeAA || !NoFreeAA->isAssumedNoFree()) &&
!ICS.hasFnAttr(Attribute::NoFree)) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
}
}
return ChangeStatus::UNCHANGED;
}
/// ------------------------ NonNull Argument Attribute ------------------------
struct AANonNullImpl : AANonNull, BooleanState {
AANonNullImpl(Value &V, InformationCache &InfoCache)
: AANonNull(V, InfoCache) {}
AANonNullImpl(Value *AssociatedVal, Value &AnchoredValue,
InformationCache &InfoCache)
: AANonNull(AssociatedVal, AnchoredValue, InfoCache) {}
/// See AbstractAttribute::getState()
/// {
AbstractState &getState() override { return *this; }
const AbstractState &getState() const override { return *this; }
/// }
/// See AbstractAttribute::getAsStr().
const std::string getAsStr() const override {
return getAssumed() ? "nonnull" : "may-null";
}
/// See AANonNull::isAssumedNonNull().
bool isAssumedNonNull() const override { return getAssumed(); }
/// See AANonNull::isKnownNonNull().
bool isKnownNonNull() const override { return getKnown(); }
/// 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 &)> generatePredicate(Attributor &);
};
std::function<bool(Value &)> 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 &)> Pred = [&](Value &RV) -> bool {
if (isKnownNonZero(&RV, getAnchorScope().getParent()->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 : AANonNullImpl {
AANonNullReturned(Function &F, InformationCache &InfoCache)
: AANonNullImpl(F, InfoCache) {}
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override { return MP_RETURNED; }
/// See AbstractAttriubute::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;
};
ChangeStatus AANonNullReturned::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
auto *AARetVal = A.getAAFor<AAReturnedValues>(*this, F);
if (!AARetVal) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
std::function<bool(Value &)> Pred = this->generatePredicate(A);
if (!AARetVal->checkForallReturnedValues(Pred)) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
return ChangeStatus::UNCHANGED;
}
/// NonNull attribute for function argument.
struct AANonNullArgument : AANonNullImpl {
AANonNullArgument(Argument &A, InformationCache &InfoCache)
: AANonNullImpl(A, InfoCache) {}
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override { return MP_ARGUMENT; }
/// 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;
};
/// NonNull attribute for a call site argument.
struct AANonNullCallSiteArgument : AANonNullImpl {
/// See AANonNullImpl::AANonNullImpl(...).
AANonNullCallSiteArgument(CallSite CS, unsigned ArgNo,
InformationCache &InfoCache)
: AANonNullImpl(CS.getArgOperand(ArgNo), *CS.getInstruction(), InfoCache),
ArgNo(ArgNo) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
CallSite CS(&getAnchoredValue());
if (CS.paramHasAttr(ArgNo, getAttrKind()) ||
CS.paramHasAttr(ArgNo, Attribute::Dereferenceable) ||
isKnownNonZero(getAssociatedValue(),
getAnchorScope().getParent()->getDataLayout()))
indicateOptimisticFixpoint();
}
/// See AbstractAttribute::updateImpl(Attributor &A).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override {
return MP_CALL_SITE_ARGUMENT;
};
// Return argument index of associated value.
int getArgNo() const { return ArgNo; }
private:
unsigned ArgNo;
};
ChangeStatus AANonNullArgument::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
Argument &Arg = cast<Argument>(getAnchoredValue());
unsigned ArgNo = Arg.getArgNo();
// Callback function
std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) {
assert(CS && "Sanity check: Call site was not initialized properly!");
auto *NonNullAA = A.getAAFor<AANonNull>(*this, *CS.getInstruction(), ArgNo);
// Check that NonNullAA is AANonNullCallSiteArgument.
if (NonNullAA) {
ImmutableCallSite ICS(&NonNullAA->getAnchoredValue());
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, getAnchorScope().getParent()->getDataLayout()))
return true;
return false;
};
if (!A.checkForAllCallSites(F, CallSiteCheck, true)) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
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()) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
return ChangeStatus::UNCHANGED;
}
/// ------------------------ Will-Return Attributes ----------------------------
struct AAWillReturnImpl : public AAWillReturn, BooleanState {
/// See AbstractAttribute::AbstractAttribute(...).
AAWillReturnImpl(Function &F, InformationCache &InfoCache)
: AAWillReturn(F, InfoCache) {}
/// See AAWillReturn::isKnownWillReturn().
bool isKnownWillReturn() const override { return getKnown(); }
/// See AAWillReturn::isAssumedWillReturn().
bool isAssumedWillReturn() const override { return getAssumed(); }
/// See AbstractAttribute::getState(...).
AbstractState &getState() override { return *this; }
/// See AbstractAttribute::getState(...).
const AbstractState &getState() const override { return *this; }
/// See AbstractAttribute::getAsStr()
const std::string getAsStr() const override {
return getAssumed() ? "willreturn" : "may-noreturn";
}
};
struct AAWillReturnFunction final : AAWillReturnImpl {
/// See AbstractAttribute::AbstractAttribute(...).
AAWillReturnFunction(Function &F, InformationCache &InfoCache)
: AAWillReturnImpl(F, InfoCache) {}
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override { return MP_FUNCTION; }
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override;
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
};
// 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) {
Function &F = getAnchorScope();
// The map from instruction opcodes to those instructions in the function.
auto &OpcodeInstMap = InfoCache.getOpcodeInstMapForFunction(F);
for (unsigned Opcode :
{(unsigned)Instruction::Invoke, (unsigned)Instruction::CallBr,
(unsigned)Instruction::Call}) {
for (Instruction *I : OpcodeInstMap[Opcode]) {
auto ICS = ImmutableCallSite(I);
if (ICS.hasFnAttr(Attribute::WillReturn))
continue;
auto *WillReturnAA = A.getAAFor<AAWillReturn>(*this, *I);
if (!WillReturnAA || !WillReturnAA->isAssumedWillReturn()) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
auto *NoRecurseAA = A.getAAFor<AANoRecurse>(*this, *I);
// FIXME: (i) Prohibit any recursion for now.
// (ii) AANoRecurse isn't implemented yet so currently any call is
// regarded as having recursion.
// Code below should be
// if ((!NoRecurseAA || !NoRecurseAA->isAssumedNoRecurse()) &&
if (!NoRecurseAA && !ICS.hasFnAttr(Attribute::NoRecurse)) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
}
}
return ChangeStatus::UNCHANGED;
}
/// ------------------------ NoAlias Argument Attribute ------------------------
struct AANoAliasImpl : AANoAlias, BooleanState {
AANoAliasImpl(Value &V, InformationCache &InfoCache)
: AANoAlias(V, InfoCache) {}
/// See AbstractAttribute::getState()
/// {
AbstractState &getState() override { return *this; }
const AbstractState &getState() const override { return *this; }
/// }
const std::string getAsStr() const override {
return getAssumed() ? "noalias" : "may-alias";
}
/// See AANoAlias::isAssumedNoAlias().
bool isAssumedNoAlias() const override { return getAssumed(); }
/// See AANoAlias::isKnowndNoAlias().
bool isKnownNoAlias() const override { return getKnown(); }
};
/// NoAlias attribute for function return value.
struct AANoAliasReturned : AANoAliasImpl {
AANoAliasReturned(Function &F, InformationCache &InfoCache)
: AANoAliasImpl(F, InfoCache) {}
/// See AbstractAttribute::getManifestPosition().
virtual ManifestPosition getManifestPosition() const override {
return MP_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;
};
ChangeStatus AANoAliasReturned::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
auto *AARetValImpl = A.getAAFor<AAReturnedValuesImpl>(*this, F);
if (!AARetValImpl) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
std::function<bool(Value &)> Pred = [&](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;
auto *NoAliasAA = A.getAAFor<AANoAlias>(*this, RV);
if (!ICS.returnDoesNotAlias() &&
(!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 (!AARetValImpl->checkForallReturnedValues(Pred)) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
return ChangeStatus::UNCHANGED;
}
/// -------------------AAIsDead Function Attribute-----------------------
struct AAIsDeadFunction : AAIsDead, BooleanState {
AAIsDeadFunction(Function &F, InformationCache &InfoCache)
: AAIsDead(F, InfoCache) {}
/// See AbstractAttribute::getState()
/// {
AbstractState &getState() override { return *this; }
const AbstractState &getState() const override { return *this; }
/// }
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override { return MP_FUNCTION; }
void initialize(Attributor &A) override {
Function &F = getAnchorScope();
ToBeExploredPaths.insert(&(F.getEntryBlock().front()));
AssumedLiveBlocks.insert(&(F.getEntryBlock()));
for (size_t i = 0; i < ToBeExploredPaths.size(); ++i)
explorePath(A, ToBeExploredPaths[i]);
}
/// Explores new instructions starting from \p I. If instruction is dead, stop
/// and return true if it discovered a new instruction.
bool explorePath(Attributor &A, Instruction *I);
const std::string getAsStr() const override {
return "LiveBBs(" + std::to_string(AssumedLiveBlocks.size()) + "/" +
std::to_string(getAnchorScope().size()) + ")";
}
/// See AbstractAttribute::manifest(...).
ChangeStatus manifest(Attributor &A) override {
assert(getState().isValidState() &&
"Attempted to manifest an invalid state!");
ChangeStatus HasChanged = ChangeStatus::UNCHANGED;
for (Instruction *I : NoReturnCalls) {
BasicBlock *BB = I->getParent();
/// Invoke is replaced with a call and unreachable is placed after it.
if (auto *II = dyn_cast<InvokeInst>(I)) {
changeToCall(II);
changeToUnreachable(BB->getTerminator(), /* UseLLVMTrap */ false);
LLVM_DEBUG(dbgs() << "[AAIsDead] Replaced invoke with call inst\n");
continue;
}
SplitBlock(BB, I->getNextNode());
changeToUnreachable(BB->getTerminator(), /* UseLLVMTrap */ false);
HasChanged = ChangeStatus::CHANGED;
}
return HasChanged;
}
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
/// See AAIsDead::isAssumedDead().
bool isAssumedDead(BasicBlock *BB) const override {
if (!getAssumed())
return false;
return !AssumedLiveBlocks.count(BB);
}
/// See AAIsDead::isKnownDead().
bool isKnownDead(BasicBlock *BB) const override {
if (!getKnown())
return false;
return !AssumedLiveBlocks.count(BB);
}
/// Collection of to be explored paths.
SmallSetVector<Instruction *, 8> ToBeExploredPaths;
/// Collection of all assumed live BasicBlocks.
DenseSet<BasicBlock *> AssumedLiveBlocks;
/// Collection of calls with noreturn attribute, assumed or knwon.
SmallSetVector<Instruction *, 4> NoReturnCalls;
};
bool AAIsDeadFunction::explorePath(Attributor &A, Instruction *I) {
BasicBlock *BB = I->getParent();
while (I) {
ImmutableCallSite ICS(I);
if (ICS) {
auto *NoReturnAA = A.getAAFor<AANoReturn>(*this, *I);
if (NoReturnAA && NoReturnAA->isAssumedNoReturn()) {
if (!NoReturnCalls.insert(I))
// If I is already in the NoReturnCalls set, then it stayed noreturn
// and we didn't discover any new instructions.
return false;
// Discovered new noreturn call, return true to indicate that I is not
// noreturn anymore and should be deleted from NoReturnCalls.
return true;
}
if (ICS.hasFnAttr(Attribute::NoReturn)) {
if (!NoReturnCalls.insert(I))
return false;
return true;
}
}
I = I->getNextNode();
}
// get new paths (reachable blocks).
for (BasicBlock *SuccBB : successors(BB)) {
Instruction *Inst = &(SuccBB->front());
AssumedLiveBlocks.insert(SuccBB);
ToBeExploredPaths.insert(Inst);
}
return true;
}
ChangeStatus AAIsDeadFunction::updateImpl(Attributor &A) {
// Temporary collection to iterate over existing noreturn instructions. This
// will alow easier modification of NoReturnCalls collection
SmallVector<Instruction *, 8> NoReturnChanged;
ChangeStatus Status = ChangeStatus::UNCHANGED;
for (Instruction *I : NoReturnCalls)
NoReturnChanged.push_back(I);
for (Instruction *I : NoReturnChanged) {
size_t Size = ToBeExploredPaths.size();
// Still noreturn.
if (!explorePath(A, I))
continue;
NoReturnCalls.remove(I);
// No new paths.
if (Size == ToBeExploredPaths.size())
continue;
// At least one new path.
Status = ChangeStatus::CHANGED;
// explore new paths.
while (Size != ToBeExploredPaths.size())
explorePath(A, ToBeExploredPaths[Size++]);
}
LLVM_DEBUG(
dbgs() << "[AAIsDead] AssumedLiveBlocks: " << AssumedLiveBlocks.size()
<< "Total number of blocks: " << getAnchorScope().size() << "\n");
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 DerefBytesState.isAtFixpoint() && NonNullGlobalState.isAtFixpoint();
}
/// See AbstractState::indicateOptimisticFixpoint(...)
void indicateOptimisticFixpoint() override {
DerefBytesState.indicateOptimisticFixpoint();
NonNullGlobalState.indicateOptimisticFixpoint();
}
/// See AbstractState::indicatePessimisticFixpoint(...)
void indicatePessimisticFixpoint() override {
DerefBytesState.indicatePessimisticFixpoint();
NonNullGlobalState.indicatePessimisticFixpoint();
}
/// 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 {
AADereferenceableImpl(Value &V, InformationCache &InfoCache)
: AADereferenceable(V, InfoCache) {}
AADereferenceableImpl(Value *AssociatedVal, Value &AnchoredValue,
InformationCache &InfoCache)
: AADereferenceable(AssociatedVal, AnchoredValue, InfoCache) {}
/// See AbstractAttribute::getState()
/// {
AbstractState &getState() override { return *this; }
const AbstractState &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(SmallVectorImpl<Attribute> &Attrs) const override {
LLVMContext &Ctx = AnchoredVal.getContext();
// 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 =
getAttrIndex(getManifestPosition(), getArgNo(getAnchoredValue()));
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 : AADereferenceableImpl {
AADereferenceableReturned(Function &F, InformationCache &InfoCache)
: AADereferenceableImpl(F, InfoCache) {}
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override { return MP_RETURNED; }
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
};
// 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 = getAnchorScope().getParent()->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));
auto *AARetVal = A.getAAFor<AAReturnedValues>(*this, F);
if (!AARetVal) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
bool IsNonNull = isAssumedNonNull();
bool IsGlobal = isAssumedGlobal();
std::function<bool(Value &)> Pred = [&](Value &RV) -> bool {
takeAssumedDerefBytesMinimum(
computeAssumedDerefenceableBytes(A, RV, IsNonNull, IsGlobal));
return isValidState();
};
if (AARetVal->checkForallReturnedValues(Pred)) {
updateAssumedNonNullGlobalState(IsNonNull, IsGlobal);
return BeforeState == static_cast<DerefState>(*this)
? ChangeStatus::UNCHANGED
: ChangeStatus::CHANGED;
}
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
struct AADereferenceableArgument : AADereferenceableImpl {
AADereferenceableArgument(Argument &A, InformationCache &InfoCache)
: AADereferenceableImpl(A, InfoCache) {}
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override { return MP_ARGUMENT; }
/// See AbstractAttribute::updateImpl(...).
ChangeStatus updateImpl(Attributor &A) override;
};
ChangeStatus AADereferenceableArgument::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
Argument &Arg = cast<Argument>(getAnchoredValue());
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->getAnchoredValue());
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, true)) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
updateAssumedNonNullGlobalState(IsNonNull, IsGlobal);
return BeforeState == static_cast<DerefState>(*this) ? ChangeStatus::UNCHANGED
: ChangeStatus::CHANGED;
}
/// Dereferenceable attribute for a call site argument.
struct AADereferenceableCallSiteArgument : AADereferenceableImpl {
/// See AADereferenceableImpl::AADereferenceableImpl(...).
AADereferenceableCallSiteArgument(CallSite CS, unsigned ArgNo,
InformationCache &InfoCache)
: AADereferenceableImpl(CS.getArgOperand(ArgNo), *CS.getInstruction(),
InfoCache),
ArgNo(ArgNo) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
CallSite CS(&getAnchoredValue());
if (CS.paramHasAttr(ArgNo, Attribute::Dereferenceable))
takeKnownDerefBytesMaximum(CS.getDereferenceableBytes(ArgNo));
if (CS.paramHasAttr(ArgNo, Attribute::DereferenceableOrNull))
takeKnownDerefBytesMaximum(CS.getDereferenceableOrNullBytes(ArgNo));
}
/// See AbstractAttribute::updateImpl(Attributor &A).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override {
return MP_CALL_SITE_ARGUMENT;
};
// Return argument index of associated value.
int getArgNo() const { return ArgNo; }
private:
unsigned ArgNo;
};
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, getAnchoredValue(), ArgNo));
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, IntegerState {
// Max alignemnt value allowed in IR
static const unsigned MAX_ALIGN = 1U << 29;
AAAlignImpl(Value *AssociatedVal, Value &AnchoredValue,
InformationCache &InfoCache)
: AAAlign(AssociatedVal, AnchoredValue, InfoCache),
IntegerState(MAX_ALIGN) {}
AAAlignImpl(Value &V, InformationCache &InfoCache)
: AAAlignImpl(&V, V, InfoCache) {}
/// See AbstractAttribute::getState()
/// {
AbstractState &getState() override { return *this; }
const AbstractState &getState() const override { return *this; }
/// }
virtual const std::string getAsStr() const override {
return getAssumedAlign() ? ("align<" + std::to_string(getKnownAlign()) +
"-" + std::to_string(getAssumedAlign()) + ">")
: "unknown-align";
}
/// See AAAlign::getAssumedAlign().
unsigned getAssumedAlign() const override { return getAssumed(); }
/// See AAAlign::getKnownAlign().
unsigned getKnownAlign() const override { return getKnown(); }
/// See AbstractAttriubute::initialize(...).
void initialize(Attributor &A) override {
Function &F = getAnchorScope();
unsigned AttrIdx =
getAttrIndex(getManifestPosition(), getArgNo(getAnchoredValue()));
// Already the function has align attribute on return value or argument.
if (F.getAttributes().hasAttribute(AttrIdx, ID))
addKnownBits(F.getAttribute(AttrIdx, ID).getAlignment());
}
/// See AbstractAttribute::getDeducedAttributes
virtual void
getDeducedAttributes(SmallVectorImpl<Attribute> &Attrs) const override {
LLVMContext &Ctx = AnchoredVal.getContext();
Attrs.emplace_back(Attribute::getWithAlignment(Ctx, getAssumedAlign()));
}
};
/// Align attribute for function return value.
struct AAAlignReturned : AAAlignImpl {
AAAlignReturned(Function &F, InformationCache &InfoCache)
: AAAlignImpl(F, InfoCache) {}
/// See AbstractAttribute::getManifestPosition().
virtual ManifestPosition getManifestPosition() const override {
return MP_RETURNED;
}
/// See AbstractAttribute::updateImpl(...).
virtual ChangeStatus updateImpl(Attributor &A) override;
};
ChangeStatus AAAlignReturned::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
auto *AARetValImpl = A.getAAFor<AAReturnedValuesImpl>(*this, F);
if (!AARetValImpl) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
// 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();
std::function<bool(Value &)> Pred = [&](Value &RV) -> bool {
auto *AlignAA = A.getAAFor<AAAlign>(*this, RV);
if (AlignAA)
takeAssumedMinimum(AlignAA->getAssumedAlign());
else
// Use IR information.
takeAssumedMinimum(RV.getPointerAlignment(
getAnchorScope().getParent()->getDataLayout()));
return isValidState();
};
if (!AARetValImpl->checkForallReturnedValues(Pred)) {
indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
return (getAssumed() != BeforeState) ? ChangeStatus::CHANGED
: ChangeStatus::UNCHANGED;
}
/// Align attribute for function argument.
struct AAAlignArgument : AAAlignImpl {
AAAlignArgument(Argument &A, InformationCache &InfoCache)
: AAAlignImpl(A, InfoCache) {}
/// See AbstractAttribute::getManifestPosition().
virtual ManifestPosition getManifestPosition() const override {
return MP_ARGUMENT;
}
/// See AbstractAttribute::updateImpl(...).
virtual ChangeStatus updateImpl(Attributor &A) override;
};
ChangeStatus AAAlignArgument::updateImpl(Attributor &A) {
Function &F = getAnchorScope();
Argument &Arg = cast<Argument>(getAnchoredValue());
unsigned ArgNo = Arg.getArgNo();
const DataLayout &DL = F.getParent()->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->getAnchoredValue());
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, true))
indicatePessimisticFixpoint();
return BeforeState == getAssumed() ? ChangeStatus::UNCHANGED
: ChangeStatus ::CHANGED;
}
struct AAAlignCallSiteArgument : AAAlignImpl {
/// See AANonNullImpl::AANonNullImpl(...).
AAAlignCallSiteArgument(CallSite CS, unsigned ArgNo,
InformationCache &InfoCache)
: AAAlignImpl(CS.getArgOperand(ArgNo), *CS.getInstruction(), InfoCache),
ArgNo(ArgNo) {}
/// See AbstractAttribute::initialize(...).
void initialize(Attributor &A) override {
CallSite CS(&getAnchoredValue());
takeKnownMaximum(getAssociatedValue()->getPointerAlignment(
getAnchorScope().getParent()->getDataLayout()));
}
/// See AbstractAttribute::updateImpl(Attributor &A).
ChangeStatus updateImpl(Attributor &A) override;
/// See AbstractAttribute::getManifestPosition().
ManifestPosition getManifestPosition() const override {
return MP_CALL_SITE_ARGUMENT;
};
// Return argument index of associated value.
int getArgNo() const { return ArgNo; }
private:
unsigned ArgNo;
};
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;
}
/// ----------------------------------------------------------------------------
/// Attributor
/// ----------------------------------------------------------------------------
bool Attributor::checkForAllCallSites(Function &F,
std::function<bool(CallSite)> &Pred,
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()) {
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;
}
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);
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;
}
void Attributor::identifyDefaultAbstractAttributes(
Function &F, InformationCache &InfoCache,
DenseSet</* Attribute::AttrKind */ unsigned> *Whitelist) {
// Every function can be nounwind.
registerAA(*new AANoUnwindFunction(F, InfoCache));
// Every function might be marked "nosync"
registerAA(*new AANoSyncFunction(F, InfoCache));
// Every function might be "no-free".
registerAA(*new AANoFreeFunction(F, InfoCache));
// 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.
if (!Whitelist || Whitelist->count(AAReturnedValues::ID))
registerAA(*new AAReturnedValuesImpl(F, InfoCache));
if (ReturnType->isPointerTy()) {
// Every function with pointer return type might be marked align.
if (!Whitelist || Whitelist->count(AAAlignReturned::ID))
registerAA(*new AAAlignReturned(F, InfoCache));
// Every function with pointer return type might be marked nonnull.
if (!Whitelist || Whitelist->count(AANonNullReturned::ID))
registerAA(*new AANonNullReturned(F, InfoCache));
// Every function with pointer return type might be marked noalias.
if (!Whitelist || Whitelist->count(AANoAliasReturned::ID))
registerAA(*new AANoAliasReturned(F, InfoCache));
// Every function with pointer return type might be marked
// dereferenceable.
if (ReturnType->isPointerTy() &&
(!Whitelist || Whitelist->count(AADereferenceableReturned::ID)))
registerAA(*new AADereferenceableReturned(F, InfoCache));
}
}
for (Argument &Arg : F.args()) {
if (Arg.getType()->isPointerTy()) {
// Every argument with pointer type might be marked nonnull.
if (!Whitelist || Whitelist->count(AANonNullArgument::ID))
registerAA(*new AANonNullArgument(Arg, InfoCache));
// Every argument with pointer type might be marked dereferenceable.
if (!Whitelist || Whitelist->count(AADereferenceableArgument::ID))
registerAA(*new AADereferenceableArgument(Arg, InfoCache));
// Every argument with pointer type might be marked align.
if (!Whitelist || Whitelist->count(AAAlignArgument::ID))
registerAA(*new AAAlignArgument(Arg, InfoCache));
}
}
// Every function might be "will-return".
registerAA(*new AAWillReturnFunction(F, InfoCache));
// Check for dead BasicBlocks in every function.
registerAA(*new AAIsDeadFunction(F, InfoCache));
// 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".
if (!Whitelist || Whitelist->count(AANonNullCallSiteArgument::ID))
registerAA(*new AANonNullCallSiteArgument(CS, i, InfoCache), i);
// Call site argument attribute "dereferenceable".
if (!Whitelist ||
Whitelist->count(AADereferenceableCallSiteArgument::ID))
registerAA(*new AADereferenceableCallSiteArgument(CS, i, InfoCache),
i);
// Call site argument attribute "align".
if (!Whitelist || Whitelist->count(AAAlignCallSiteArgument::ID))
registerAA(*new AAAlignCallSiteArgument(CS, i, InfoCache), 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,
AbstractAttribute::ManifestPosition AP) {
switch (AP) {
case AbstractAttribute::MP_ARGUMENT:
return OS << "arg";
case AbstractAttribute::MP_CALL_SITE_ARGUMENT:
return OS << "cs_arg";
case AbstractAttribute::MP_FUNCTION:
return OS << "fn";
case AbstractAttribute::MP_RETURNED:
return OS << "fn_ret";
}
llvm_unreachable("Unknown attribute position!");
}
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 << "[" << getManifestPosition() << "][" << getAsStr() << "]["
<< AnchoredVal.getName() << "]";
}
///}
/// ----------------------------------------------------------------------------
/// 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.
Attributor A;
InformationCache 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, InfoCache);
}
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;
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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