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//===- Attributor.h --- Module-wide attribute deduction ---------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Attributor: An inter procedural (abstract) "attribute" deduction framework.
//
// The Attributor framework is an inter procedural abstract analysis (fixpoint
// iteration analysis). The goal is to allow easy deduction of new attributes as
// well as information exchange between abstract attributes in-flight.
//
// The Attributor class is the driver and the link between the various abstract
// attributes. The Attributor will iterate until a fixpoint state is reached by
// all abstract attributes in-flight, or until it will enforce a pessimistic fix
// point because an iteration limit is reached.
//
// Abstract attributes, derived from the AbstractAttribute class, actually
// describe properties of the code. They can correspond to actual LLVM-IR
// attributes, or they can be more general, ultimately unrelated to LLVM-IR
// attributes. The latter is useful when an abstract attributes provides
// information to other abstract attributes in-flight but we might not want to
// manifest the information. The Attributor allows to query in-flight abstract
// attributes through the `Attributor::getAAFor` method (see the method
// description for an example). If the method is used by an abstract attribute
// P, and it results in an abstract attribute Q, the Attributor will
// automatically capture a potential dependence from Q to P. This dependence
// will cause P to be reevaluated whenever Q changes in the future.
//
// The Attributor will only reevaluated abstract attributes that might have
// changed since the last iteration. That means that the Attribute will not
// revisit all instructions/blocks/functions in the module but only query
// an update from a subset of the abstract attributes.
//
// The update method `AbstractAttribute::updateImpl` is implemented by the
// specific "abstract attribute" subclasses. The method is invoked whenever the
// currently assumed state (see the AbstractState class) might not be valid
// anymore. This can, for example, happen if the state was dependent on another
// abstract attribute that changed. In every invocation, the update method has
// to adjust the internal state of an abstract attribute to a point that is
// justifiable by the underlying IR and the current state of abstract attributes
// in-flight. Since the IR is given and assumed to be valid, the information
// derived from it can be assumed to hold. However, information derived from
// other abstract attributes is conditional on various things. If the justifying
// state changed, the `updateImpl` has to revisit the situation and potentially
// find another justification or limit the optimistic assumes made.
//
// Change is the key in this framework. Until a state of no-change, thus a
// fixpoint, is reached, the Attributor will query the abstract attributes
// in-flight to re-evaluate their state. If the (current) state is too
// optimistic, hence it cannot be justified anymore through other abstract
// attributes or the state of the IR, the state of the abstract attribute will
// have to change. Generally, we assume abstract attribute state to be a finite
// height lattice and the update function to be monotone. However, these
// conditions are not enforced because the iteration limit will guarantee
// termination. If an optimistic fixpoint is reached, or a pessimistic fix
// point is enforced after a timeout, the abstract attributes are tasked to
// manifest their result in the IR for passes to come.
//
// Attribute manifestation is not mandatory. If desired, there is support to
// generate a single or multiple LLVM-IR attributes already in the helper struct
// IRAttribute. In the simplest case, a subclass inherits from IRAttribute with
// a proper Attribute::AttrKind as template parameter. The Attributor
// manifestation framework will then create and place a new attribute if it is
// allowed to do so (based on the abstract state). Other use cases can be
// achieved by overloading AbstractAttribute or IRAttribute methods.
//
//
// The "mechanics" of adding a new "abstract attribute":
// - Define a class (transitively) inheriting from AbstractAttribute and one
// (which could be the same) that (transitively) inherits from AbstractState.
// For the latter, consider the already available BooleanState and
// {Inc,Dec,Bit}IntegerState if they fit your needs, e.g., you require only a
// number tracking or bit-encoding.
// - Implement all pure methods. Also use overloading if the attribute is not
// conforming with the "default" behavior: A (set of) LLVM-IR attribute(s) for
// an argument, call site argument, function return value, or function. See
// the class and method descriptions for more information on the two
// "Abstract" classes and their respective methods.
// - Register opportunities for the new abstract attribute in the
// `Attributor::identifyDefaultAbstractAttributes` method if it should be
// counted as a 'default' attribute.
// - Add sufficient tests.
// - Add a Statistics object for bookkeeping. If it is a simple (set of)
// attribute(s) manifested through the Attributor manifestation framework, see
// the bookkeeping function in Attributor.cpp.
// - If instructions with a certain opcode are interesting to the attribute, add
// that opcode to the switch in `Attributor::identifyAbstractAttributes`. This
// will make it possible to query all those instructions through the
// `InformationCache::getOpcodeInstMapForFunction` interface and eliminate the
// need to traverse the IR repeatedly.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_TRANSFORMS_IPO_ATTRIBUTOR_H
#define LLVM_TRANSFORMS_IPO_ATTRIBUTOR_H
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/SCCIterator.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/CallGraph.h"
#include "llvm/Analysis/MustExecute.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/ConstantRange.h"
#include "llvm/IR/PassManager.h"
namespace llvm {
struct AbstractAttribute;
struct InformationCache;
struct AAIsDead;
class Function;
/// Simple enum classes that forces properties to be spelled out explicitly.
///
///{
enum class ChangeStatus {
CHANGED,
UNCHANGED,
};
ChangeStatus operator|(ChangeStatus l, ChangeStatus r);
ChangeStatus operator&(ChangeStatus l, ChangeStatus r);
enum class DepClassTy {
REQUIRED,
OPTIONAL,
};
///}
/// Helper to describe and deal with positions in the LLVM-IR.
///
/// A position in the IR is described by an anchor value and an "offset" that
/// could be the argument number, for call sites and arguments, or an indicator
/// of the "position kind". The kinds, specified in the Kind enum below, include
/// the locations in the attribute list, i.a., function scope and return value,
/// as well as a distinction between call sites and functions. Finally, there
/// are floating values that do not have a corresponding attribute list
/// position.
struct IRPosition {
virtual ~IRPosition() {}
/// The positions we distinguish in the IR.
///
/// The values are chosen such that the KindOrArgNo member has a value >= 1
/// if it is an argument or call site argument while a value < 1 indicates the
/// respective kind of that value.
enum Kind : int {
IRP_INVALID = -6, ///< An invalid position.
IRP_FLOAT = -5, ///< A position that is not associated with a spot suitable
///< for attributes. This could be any value or instruction.
IRP_RETURNED = -4, ///< An attribute for the function return value.
IRP_CALL_SITE_RETURNED = -3, ///< An attribute for a call site return value.
IRP_FUNCTION = -2, ///< An attribute for a function (scope).
IRP_CALL_SITE = -1, ///< An attribute for a call site (function scope).
IRP_ARGUMENT = 0, ///< An attribute for a function argument.
IRP_CALL_SITE_ARGUMENT = 1, ///< An attribute for a call site argument.
};
/// Default constructor available to create invalid positions implicitly. All
/// other positions need to be created explicitly through the appropriate
/// static member function.
IRPosition() : AnchorVal(nullptr), KindOrArgNo(IRP_INVALID) { verify(); }
/// Create a position describing the value of \p V.
static const IRPosition value(const Value &V) {
if (auto *Arg = dyn_cast<Argument>(&V))
return IRPosition::argument(*Arg);
if (auto *CB = dyn_cast<CallBase>(&V))
return IRPosition::callsite_returned(*CB);
return IRPosition(const_cast<Value &>(V), IRP_FLOAT);
}
/// Create a position describing the function scope of \p F.
static const IRPosition function(const Function &F) {
return IRPosition(const_cast<Function &>(F), IRP_FUNCTION);
}
/// Create a position describing the returned value of \p F.
static const IRPosition returned(const Function &F) {
return IRPosition(const_cast<Function &>(F), IRP_RETURNED);
}
/// Create a position describing the argument \p Arg.
static const IRPosition argument(const Argument &Arg) {
return IRPosition(const_cast<Argument &>(Arg), Kind(Arg.getArgNo()));
}
/// Create a position describing the function scope of \p CB.
static const IRPosition callsite_function(const CallBase &CB) {
return IRPosition(const_cast<CallBase &>(CB), IRP_CALL_SITE);
}
/// Create a position describing the returned value of \p CB.
static const IRPosition callsite_returned(const CallBase &CB) {
return IRPosition(const_cast<CallBase &>(CB), IRP_CALL_SITE_RETURNED);
}
/// Create a position describing the argument of \p CB at position \p ArgNo.
static const IRPosition callsite_argument(const CallBase &CB,
unsigned ArgNo) {
return IRPosition(const_cast<CallBase &>(CB), Kind(ArgNo));
}
/// Create a position describing the function scope of \p ICS.
static const IRPosition callsite_function(ImmutableCallSite ICS) {
return IRPosition::callsite_function(cast<CallBase>(*ICS.getInstruction()));
}
/// Create a position describing the returned value of \p ICS.
static const IRPosition callsite_returned(ImmutableCallSite ICS) {
return IRPosition::callsite_returned(cast<CallBase>(*ICS.getInstruction()));
}
/// Create a position describing the argument of \p ICS at position \p ArgNo.
static const IRPosition callsite_argument(ImmutableCallSite ICS,
unsigned ArgNo) {
return IRPosition::callsite_argument(cast<CallBase>(*ICS.getInstruction()),
ArgNo);
}
/// Create a position describing the argument of \p ACS at position \p ArgNo.
static const IRPosition callsite_argument(AbstractCallSite ACS,
unsigned ArgNo) {
int CSArgNo = ACS.getCallArgOperandNo(ArgNo);
if (CSArgNo >= 0)
return IRPosition::callsite_argument(
cast<CallBase>(*ACS.getInstruction()), CSArgNo);
return IRPosition();
}
/// Create a position with function scope matching the "context" of \p IRP.
/// If \p IRP is a call site (see isAnyCallSitePosition()) then the result
/// will be a call site position, otherwise the function position of the
/// associated function.
static const IRPosition function_scope(const IRPosition &IRP) {
if (IRP.isAnyCallSitePosition()) {
return IRPosition::callsite_function(
cast<CallBase>(IRP.getAnchorValue()));
}
assert(IRP.getAssociatedFunction());
return IRPosition::function(*IRP.getAssociatedFunction());
}
bool operator==(const IRPosition &RHS) const {
return (AnchorVal == RHS.AnchorVal) && (KindOrArgNo == RHS.KindOrArgNo);
}
bool operator!=(const IRPosition &RHS) const { return !(*this == RHS); }
/// Return the value this abstract attribute is anchored with.
///
/// The anchor value might not be the associated value if the latter is not
/// sufficient to determine where arguments will be manifested. This is, so
/// far, only the case for call site arguments as the value is not sufficient
/// to pinpoint them. Instead, we can use the call site as an anchor.
Value &getAnchorValue() const {
assert(KindOrArgNo != IRP_INVALID &&
"Invalid position does not have an anchor value!");
return *AnchorVal;
}
/// Return the associated function, if any.
Function *getAssociatedFunction() const {
if (auto *CB = dyn_cast<CallBase>(AnchorVal))
return CB->getCalledFunction();
assert(KindOrArgNo != IRP_INVALID &&
"Invalid position does not have an anchor scope!");
Value &V = getAnchorValue();
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();
return nullptr;
}
/// Return the associated argument, if any.
Argument *getAssociatedArgument() const;
/// Return true if the position refers to a function interface, that is the
/// function scope, the function return, or an argument.
bool isFnInterfaceKind() const {
switch (getPositionKind()) {
case IRPosition::IRP_FUNCTION:
case IRPosition::IRP_RETURNED:
case IRPosition::IRP_ARGUMENT:
return true;
default:
return false;
}
}
/// Return the Function surrounding the anchor value.
Function *getAnchorScope() const {
Value &V = getAnchorValue();
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();
return nullptr;
}
/// Return the context instruction, if any.
Instruction *getCtxI() const {
Value &V = getAnchorValue();
if (auto *I = dyn_cast<Instruction>(&V))
return I;
if (auto *Arg = dyn_cast<Argument>(&V))
if (!Arg->getParent()->isDeclaration())
return &Arg->getParent()->getEntryBlock().front();
if (auto *F = dyn_cast<Function>(&V))
if (!F->isDeclaration())
return &(F->getEntryBlock().front());
return nullptr;
}
/// Return the value this abstract attribute is associated with.
Value &getAssociatedValue() const {
assert(KindOrArgNo != IRP_INVALID &&
"Invalid position does not have an associated value!");
if (getArgNo() < 0 || isa<Argument>(AnchorVal))
return *AnchorVal;
assert(isa<CallBase>(AnchorVal) && "Expected a call base!");
return *cast<CallBase>(AnchorVal)->getArgOperand(getArgNo());
}
/// Return the argument number of the associated value if it is an argument or
/// call site argument, otherwise a negative value.
int getArgNo() const { return KindOrArgNo; }
/// Return the index in the attribute list for this position.
unsigned getAttrIdx() const {
switch (getPositionKind()) {
case IRPosition::IRP_INVALID:
case IRPosition::IRP_FLOAT:
break;
case IRPosition::IRP_FUNCTION:
case IRPosition::IRP_CALL_SITE:
return AttributeList::FunctionIndex;
case IRPosition::IRP_RETURNED:
case IRPosition::IRP_CALL_SITE_RETURNED:
return AttributeList::ReturnIndex;
case IRPosition::IRP_ARGUMENT:
case IRPosition::IRP_CALL_SITE_ARGUMENT:
return KindOrArgNo + AttributeList::FirstArgIndex;
}
llvm_unreachable(
"There is no attribute index for a floating or invalid position!");
}
/// Return the associated position kind.
Kind getPositionKind() const {
if (getArgNo() >= 0) {
assert(((isa<Argument>(getAnchorValue()) &&
isa<Argument>(getAssociatedValue())) ||
isa<CallBase>(getAnchorValue())) &&
"Expected argument or call base due to argument number!");
if (isa<CallBase>(getAnchorValue()))
return IRP_CALL_SITE_ARGUMENT;
return IRP_ARGUMENT;
}
assert(KindOrArgNo < 0 &&
"Expected (call site) arguments to never reach this point!");
return Kind(KindOrArgNo);
}
/// TODO: Figure out if the attribute related helper functions should live
/// here or somewhere else.
/// Return true if any kind in \p AKs existing in the IR at a position that
/// will affect this one. See also getAttrs(...).
/// \param IgnoreSubsumingPositions Flag to determine if subsuming positions,
/// e.g., the function position if this is an
/// argument position, should be ignored.
bool hasAttr(ArrayRef<Attribute::AttrKind> AKs,
bool IgnoreSubsumingPositions = false) const;
/// Return the attributes of any kind in \p AKs existing in the IR at a
/// position that will affect this one. While each position can only have a
/// single attribute of any kind in \p AKs, there are "subsuming" positions
/// that could have an attribute as well. This method returns all attributes
/// found in \p Attrs.
/// \param IgnoreSubsumingPositions Flag to determine if subsuming positions,
/// e.g., the function position if this is an
/// argument position, should be ignored.
void getAttrs(ArrayRef<Attribute::AttrKind> AKs,
SmallVectorImpl<Attribute> &Attrs,
bool IgnoreSubsumingPositions = false) const;
/// Return the attribute of kind \p AK existing in the IR at this position.
Attribute getAttr(Attribute::AttrKind AK) const {
if (getPositionKind() == IRP_INVALID || getPositionKind() == IRP_FLOAT)
return Attribute();
AttributeList AttrList;
if (ImmutableCallSite ICS = ImmutableCallSite(&getAnchorValue()))
AttrList = ICS.getAttributes();
else
AttrList = getAssociatedFunction()->getAttributes();
if (AttrList.hasAttribute(getAttrIdx(), AK))
return AttrList.getAttribute(getAttrIdx(), AK);
return Attribute();
}
/// Remove the attribute of kind \p AKs existing in the IR at this position.
void removeAttrs(ArrayRef<Attribute::AttrKind> AKs) const {
if (getPositionKind() == IRP_INVALID || getPositionKind() == IRP_FLOAT)
return;
AttributeList AttrList;
CallSite CS = CallSite(&getAnchorValue());
if (CS)
AttrList = CS.getAttributes();
else
AttrList = getAssociatedFunction()->getAttributes();
LLVMContext &Ctx = getAnchorValue().getContext();
for (Attribute::AttrKind AK : AKs)
AttrList = AttrList.removeAttribute(Ctx, getAttrIdx(), AK);
if (CS)
CS.setAttributes(AttrList);
else
getAssociatedFunction()->setAttributes(AttrList);
}
bool isAnyCallSitePosition() const {
switch (getPositionKind()) {
case IRPosition::IRP_CALL_SITE:
case IRPosition::IRP_CALL_SITE_RETURNED:
case IRPosition::IRP_CALL_SITE_ARGUMENT:
return true;
default:
return false;
}
}
/// Special DenseMap key values.
///
///{
static const IRPosition EmptyKey;
static const IRPosition TombstoneKey;
///}
private:
/// Private constructor for special values only!
explicit IRPosition(int KindOrArgNo)
: AnchorVal(0), KindOrArgNo(KindOrArgNo) {}
/// IRPosition anchored at \p AnchorVal with kind/argument numbet \p PK.
explicit IRPosition(Value &AnchorVal, Kind PK)
: AnchorVal(&AnchorVal), KindOrArgNo(PK) {
verify();
}
/// Verify internal invariants.
void verify();
protected:
/// The value this position is anchored at.
Value *AnchorVal;
/// The argument number, if non-negative, or the position "kind".
int KindOrArgNo;
};
/// Helper that allows IRPosition as a key in a DenseMap.
template <> struct DenseMapInfo<IRPosition> {
static inline IRPosition getEmptyKey() { return IRPosition::EmptyKey; }
static inline IRPosition getTombstoneKey() {
return IRPosition::TombstoneKey;
}
static unsigned getHashValue(const IRPosition &IRP) {
return (DenseMapInfo<Value *>::getHashValue(&IRP.getAnchorValue()) << 4) ^
(unsigned(IRP.getArgNo()));
}
static bool isEqual(const IRPosition &LHS, const IRPosition &RHS) {
return LHS == RHS;
}
};
/// A visitor class for IR positions.
///
/// Given a position P, the SubsumingPositionIterator allows to visit "subsuming
/// positions" wrt. attributes/information. Thus, if a piece of information
/// holds for a subsuming position, it also holds for the position P.
///
/// The subsuming positions always include the initial position and then,
/// depending on the position kind, additionally the following ones:
/// - for IRP_RETURNED:
/// - the function (IRP_FUNCTION)
/// - for IRP_ARGUMENT:
/// - the function (IRP_FUNCTION)
/// - for IRP_CALL_SITE:
/// - the callee (IRP_FUNCTION), if known
/// - for IRP_CALL_SITE_RETURNED:
/// - the callee (IRP_RETURNED), if known
/// - the call site (IRP_FUNCTION)
/// - the callee (IRP_FUNCTION), if known
/// - for IRP_CALL_SITE_ARGUMENT:
/// - the argument of the callee (IRP_ARGUMENT), if known
/// - the callee (IRP_FUNCTION), if known
/// - the position the call site argument is associated with if it is not
/// anchored to the call site, e.g., if it is an argument then the argument
/// (IRP_ARGUMENT)
class SubsumingPositionIterator {
SmallVector<IRPosition, 4> IRPositions;
using iterator = decltype(IRPositions)::iterator;
public:
SubsumingPositionIterator(const IRPosition &IRP);
iterator begin() { return IRPositions.begin(); }
iterator end() { return IRPositions.end(); }
};
/// Wrapper for FunctoinAnalysisManager.
struct AnalysisGetter {
template <typename Analysis>
typename Analysis::Result *getAnalysis(const Function &F) {
if (!MAM || !F.getParent())
return nullptr;
auto &FAM = MAM->getResult<FunctionAnalysisManagerModuleProxy>(
const_cast<Module &>(*F.getParent()))
.getManager();
return &FAM.getResult<Analysis>(const_cast<Function &>(F));
}
template <typename Analysis>
typename Analysis::Result *getAnalysis(const Module &M) {
if (!MAM)
return nullptr;
return &MAM->getResult<Analysis>(const_cast<Module &>(M));
}
AnalysisGetter(ModuleAnalysisManager &MAM) : MAM(&MAM) {}
AnalysisGetter() {}
private:
ModuleAnalysisManager *MAM = nullptr;
};
/// Data structure to hold cached (LLVM-IR) information.
///
/// All attributes are given an InformationCache object at creation time to
/// avoid inspection of the IR by all of them individually. This default
/// InformationCache will hold information required by 'default' attributes,
/// thus the ones deduced when Attributor::identifyDefaultAbstractAttributes(..)
/// is called.
///
/// If custom abstract attributes, registered manually through
/// Attributor::registerAA(...), need more information, especially if it is not
/// reusable, it is advised to inherit from the InformationCache and cast the
/// instance down in the abstract attributes.
struct InformationCache {
InformationCache(const Module &M, AnalysisGetter &AG)
: DL(M.getDataLayout()), Explorer(/* ExploreInterBlock */ true), AG(AG) {
CallGraph *CG = AG.getAnalysis<CallGraphAnalysis>(M);
if (!CG)
return;
DenseMap<const Function *, unsigned> SccSize;
for (scc_iterator<CallGraph *> I = scc_begin(CG); !I.isAtEnd(); ++I) {
for (CallGraphNode *Node : *I)
SccSize[Node->getFunction()] = I->size();
}
SccSizeOpt = std::move(SccSize);
}
/// A map type from opcodes to instructions with this opcode.
using OpcodeInstMapTy = DenseMap<unsigned, SmallVector<Instruction *, 32>>;
/// Return the map that relates "interesting" opcodes with all instructions
/// with that opcode in \p F.
OpcodeInstMapTy &getOpcodeInstMapForFunction(const Function &F) {
return FuncInstOpcodeMap[&F];
}
/// A vector type to hold instructions.
using InstructionVectorTy = std::vector<Instruction *>;
/// Return the instructions in \p F that may read or write memory.
InstructionVectorTy &getReadOrWriteInstsForFunction(const Function &F) {
return FuncRWInstsMap[&F];
}
/// Return MustBeExecutedContextExplorer
MustBeExecutedContextExplorer &getMustBeExecutedContextExplorer() {
return Explorer;
}
/// Return TargetLibraryInfo for function \p F.
TargetLibraryInfo *getTargetLibraryInfoForFunction(const Function &F) {
return AG.getAnalysis<TargetLibraryAnalysis>(F);
}
/// Return AliasAnalysis Result for function \p F.
AAResults *getAAResultsForFunction(const Function &F) {
return AG.getAnalysis<AAManager>(F);
}
/// Return the analysis result from a pass \p AP for function \p F.
template <typename AP>
typename AP::Result *getAnalysisResultForFunction(const Function &F) {
return AG.getAnalysis<AP>(F);
}
/// Return SCC size on call graph for function \p F.
unsigned getSccSize(const Function &F) {
if (!SccSizeOpt.hasValue())
return 0;
return (SccSizeOpt.getValue())[&F];
}
/// Return datalayout used in the module.
const DataLayout &getDL() { return DL; }
private:
/// A map type from functions to opcode to instruction maps.
using FuncInstOpcodeMapTy = DenseMap<const Function *, OpcodeInstMapTy>;
/// A map type from functions to their read or write instructions.
using FuncRWInstsMapTy = DenseMap<const Function *, InstructionVectorTy>;
/// A nested map that remembers all instructions in a function with a certain
/// instruction opcode (Instruction::getOpcode()).
FuncInstOpcodeMapTy FuncInstOpcodeMap;
/// A map from functions to their instructions that may read or write memory.
FuncRWInstsMapTy FuncRWInstsMap;
/// The datalayout used in the module.
const DataLayout &DL;
/// MustBeExecutedContextExplorer
MustBeExecutedContextExplorer Explorer;
/// Getters for analysis.
AnalysisGetter &AG;
/// Cache result for scc size in the call graph
Optional<DenseMap<const Function *, unsigned>> SccSizeOpt;
/// Give the Attributor access to the members so
/// Attributor::identifyDefaultAbstractAttributes(...) can initialize them.
friend struct Attributor;
};
/// The fixpoint analysis framework that orchestrates the attribute deduction.
///
/// The Attributor provides a general abstract analysis framework (guided
/// fixpoint iteration) as well as helper functions for the deduction of
/// (LLVM-IR) attributes. However, also other code properties can be deduced,
/// propagated, and ultimately manifested through the Attributor framework. This
/// is particularly useful if these properties interact with attributes and a
/// co-scheduled deduction allows to improve the solution. Even if not, thus if
/// attributes/properties are completely isolated, they should use the
/// Attributor framework to reduce the number of fixpoint iteration frameworks
/// in the code base. Note that the Attributor design makes sure that isolated
/// attributes are not impacted, in any way, by others derived at the same time
/// if there is no cross-reasoning performed.
///
/// The public facing interface of the Attributor is kept simple and basically
/// allows abstract attributes to one thing, query abstract attributes
/// in-flight. There are two reasons to do this:
/// a) The optimistic state of one abstract attribute can justify an
/// optimistic state of another, allowing to framework to end up with an
/// optimistic (=best possible) fixpoint instead of one based solely on
/// information in the IR.
/// b) This avoids reimplementing various kinds of lookups, e.g., to check
/// for existing IR attributes, in favor of a single lookups interface
/// provided by an abstract attribute subclass.
///
/// NOTE: The mechanics of adding a new "concrete" abstract attribute are
/// described in the file comment.
struct Attributor {
/// Constructor
///
/// \param InfoCache Cache to hold various information accessible for
/// the abstract attributes.
/// \param DepRecomputeInterval Number of iterations until the dependences
/// between abstract attributes are recomputed.
/// \param Whitelist If not null, a set limiting the attribute opportunities.
Attributor(InformationCache &InfoCache, unsigned DepRecomputeInterval,
DenseSet<const char *> *Whitelist = nullptr)
: InfoCache(InfoCache), DepRecomputeInterval(DepRecomputeInterval),
Whitelist(Whitelist) {}
~Attributor() {
DeleteContainerPointers(AllAbstractAttributes);
for (auto &It : ArgumentReplacementMap)
DeleteContainerPointers(It.second);
}
/// Run the analyses until a fixpoint is reached or enforced (timeout).
///
/// The attributes registered with this Attributor can be used after as long
/// as the Attributor is not destroyed (it owns the attributes now).
///
/// \Returns CHANGED if the IR was changed, otherwise UNCHANGED.
ChangeStatus run(Module &M);
/// Lookup an abstract attribute of type \p AAType at position \p IRP. While
/// no abstract attribute is found equivalent positions are checked, see
/// SubsumingPositionIterator. Thus, the returned abstract attribute
/// might be anchored at a different position, e.g., the callee if \p IRP is a
/// call base.
///
/// This method is the only (supported) way an abstract attribute can retrieve
/// information from another abstract attribute. As an example, take an
/// abstract attribute that determines the memory access behavior for a
/// argument (readnone, readonly, ...). It should use `getAAFor` to get the
/// most optimistic information for other abstract attributes in-flight, e.g.
/// the one reasoning about the "captured" state for the argument or the one
/// reasoning on the memory access behavior of the function as a whole.
///
/// If the flag \p TrackDependence is set to false the dependence from
/// \p QueryingAA to the return abstract attribute is not automatically
/// recorded. This should only be used if the caller will record the
/// dependence explicitly if necessary, thus if it the returned abstract
/// attribute is used for reasoning. To record the dependences explicitly use
/// the `Attributor::recordDependence` method.
template <typename AAType>
const AAType &getAAFor(const AbstractAttribute &QueryingAA,
const IRPosition &IRP, bool TrackDependence = true,
DepClassTy DepClass = DepClassTy::REQUIRED) {
return getOrCreateAAFor<AAType>(IRP, &QueryingAA, TrackDependence,
DepClass);
}
/// Explicitly record a dependence from \p FromAA to \p ToAA, that is if
/// \p FromAA changes \p ToAA should be updated as well.
///
/// This method should be used in conjunction with the `getAAFor` method and
/// with the TrackDependence flag passed to the method set to false. This can
/// be beneficial to avoid false dependences but it requires the users of
/// `getAAFor` to explicitly record true dependences through this method.
/// The \p DepClass flag indicates if the dependence is striclty necessary.
/// That means for required dependences, if \p FromAA changes to an invalid
/// state, \p ToAA can be moved to a pessimistic fixpoint because it required
/// information from \p FromAA but none are available anymore.
void recordDependence(const AbstractAttribute &FromAA,
const AbstractAttribute &ToAA, DepClassTy DepClass);
/// Introduce a new abstract attribute into the fixpoint analysis.
///
/// Note that ownership of the attribute is given to the Attributor. It will
/// invoke delete for the Attributor on destruction of the Attributor.
///
/// Attributes are identified by their IR position (AAType::getIRPosition())
/// and the address of their static member (see AAType::ID).
template <typename AAType> AAType ®isterAA(AAType &AA) {
static_assert(std::is_base_of<AbstractAttribute, AAType>::value,
"Cannot register an attribute with a type not derived from "
"'AbstractAttribute'!");
// Put the attribute in the lookup map structure and the container we use to
// keep track of all attributes.
const IRPosition &IRP = AA.getIRPosition();
auto &KindToAbstractAttributeMap = AAMap[IRP];
assert(!KindToAbstractAttributeMap.count(&AAType::ID) &&
"Attribute already in map!");
KindToAbstractAttributeMap[&AAType::ID] = &AA;
AllAbstractAttributes.push_back(&AA);
return AA;
}
/// Return the internal information cache.
InformationCache &getInfoCache() { return InfoCache; }
/// Determine opportunities to derive 'default' attributes in \p F and create
/// abstract attribute objects for them.
///
/// \param F The function that is checked for attribute opportunities.
///
/// Note that abstract attribute instances are generally created even if the
/// IR already contains the information they would deduce. The most important
/// reason for this is the single interface, the one of the abstract attribute
/// instance, which can be queried without the need to look at the IR in
/// various places.
void identifyDefaultAbstractAttributes(Function &F);
/// Initialize the information cache for queries regarding function \p F.
///
/// This method needs to be called for all function that might be looked at
/// through the information cache interface *prior* to looking at them.
void initializeInformationCache(Function &F);
/// Mark the internal function \p F as live.
///
/// This will trigger the identification and initialization of attributes for
/// \p F.
void markLiveInternalFunction(const Function &F) {
assert(F.hasLocalLinkage() &&
"Only local linkage is assumed dead initially.");
identifyDefaultAbstractAttributes(const_cast<Function &>(F));
}
/// Record that \p U is to be replaces with \p NV after information was
/// manifested. This also triggers deletion of trivially dead istructions.
bool changeUseAfterManifest(Use &U, Value &NV) {
Value *&V = ToBeChangedUses[&U];
if (V && (V->stripPointerCasts() == NV.stripPointerCasts() ||
isa_and_nonnull<UndefValue>(V)))
return false;
assert((!V || V == &NV || isa<UndefValue>(NV)) &&
"Use was registered twice for replacement with different values!");
V = &NV;
return true;
}
/// Helper function to replace all uses of \p V with \p NV. Return true if
/// there is any change.
bool changeValueAfterManifest(Value &V, Value &NV) {
bool Changed = false;
for (auto &U : V.uses())
Changed |= changeUseAfterManifest(U, NV);
return Changed;
}
/// Get pointer operand of memory accessing instruction. If \p I is
/// not a memory accessing instruction, return nullptr. If \p AllowVolatile,
/// is set to false and the instruction is volatile, return nullptr.
static const Value *getPointerOperand(const Instruction *I,
bool AllowVolatile) {
if (auto *LI = dyn_cast<LoadInst>(I)) {
if (!AllowVolatile && LI->isVolatile())
return nullptr;
return LI->getPointerOperand();
}
if (auto *SI = dyn_cast<StoreInst>(I)) {
if (!AllowVolatile && SI->isVolatile())
return nullptr;
return SI->getPointerOperand();
}
if (auto *CXI = dyn_cast<AtomicCmpXchgInst>(I)) {
if (!AllowVolatile && CXI->isVolatile())
return nullptr;
return CXI->getPointerOperand();
}
if (auto *RMWI = dyn_cast<AtomicRMWInst>(I)) {
if (!AllowVolatile && RMWI->isVolatile())
return nullptr;
return RMWI->getPointerOperand();
}
return nullptr;
}
/// Record that \p I is to be replaced with `unreachable` after information
/// was manifested.
void changeToUnreachableAfterManifest(Instruction *I) {
ToBeChangedToUnreachableInsts.insert(I);
}
/// Record that \p II has at least one dead successor block. This information
/// is used, e.g., to replace \p II with a call, after information was
/// manifested.
void registerInvokeWithDeadSuccessor(InvokeInst &II) {
InvokeWithDeadSuccessor.push_back(&II);
}
/// Record that \p I is deleted after information was manifested. This also
/// triggers deletion of trivially dead istructions.
void deleteAfterManifest(Instruction &I) { ToBeDeletedInsts.insert(&I); }
/// Record that \p BB is deleted after information was manifested. This also
/// triggers deletion of trivially dead istructions.
void deleteAfterManifest(BasicBlock &BB) { ToBeDeletedBlocks.insert(&BB); }
/// Record that \p F is deleted after information was manifested.
void deleteAfterManifest(Function &F) { ToBeDeletedFunctions.insert(&F); }
/// Return true if \p AA (or its context instruction) is assumed dead.
///
/// If \p LivenessAA is not provided it is queried.
bool isAssumedDead(const AbstractAttribute &AA, const AAIsDead *LivenessAA);
/// Check \p Pred on all (transitive) uses of \p V.
///
/// This method will evaluate \p Pred on all (transitive) uses of the
/// associated value and return true if \p Pred holds every time.
bool checkForAllUses(const function_ref<bool(const Use &, bool &)> &Pred,
const AbstractAttribute &QueryingAA, const Value &V);
/// Helper struct used in the communication between an abstract attribute (AA)
/// that wants to change the signature of a function and the Attributor which
/// applies the changes. The struct is partially initialized with the
/// information from the AA (see the constructor). All other members are
/// provided by the Attributor prior to invoking any callbacks.
struct ArgumentReplacementInfo {
/// Callee repair callback type
///
/// The function repair callback is invoked once to rewire the replacement
/// arguments in the body of the new function. The argument replacement info
/// is passed, as build from the registerFunctionSignatureRewrite call, as
/// well as the replacement function and an iteratore to the first
/// replacement argument.
using CalleeRepairCBTy = std::function<void(
const ArgumentReplacementInfo &, Function &, Function::arg_iterator)>;
/// Abstract call site (ACS) repair callback type
///
/// The abstract call site repair callback is invoked once on every abstract
/// call site of the replaced function (\see ReplacedFn). The callback needs
/// to provide the operands for the call to the new replacement function.
/// The number and type of the operands appended to the provided vector
/// (second argument) is defined by the number and types determined through
/// the replacement type vector (\see ReplacementTypes). The first argument
/// is the ArgumentReplacementInfo object registered with the Attributor
/// through the registerFunctionSignatureRewrite call.
using ACSRepairCBTy =
std::function<void(const ArgumentReplacementInfo &, AbstractCallSite,
SmallVectorImpl<Value *> &)>;
/// Simple getters, see the corresponding members for details.
///{
Attributor &getAttributor() const { return A; }
const Function &getReplacedFn() const { return ReplacedFn; }
const Argument &getReplacedArg() const { return ReplacedArg; }
unsigned getNumReplacementArgs() const { return ReplacementTypes.size(); }
const SmallVectorImpl<Type *> &getReplacementTypes() const {
return ReplacementTypes;
}
///}
private:
/// Constructor that takes the argument to be replaced, the types of
/// the replacement arguments, as well as callbacks to repair the call sites
/// and new function after the replacement happened.
ArgumentReplacementInfo(Attributor &A, Argument &Arg,
ArrayRef<Type *> ReplacementTypes,
CalleeRepairCBTy &&CalleeRepairCB,
ACSRepairCBTy &&ACSRepairCB)
: A(A), ReplacedFn(*Arg.getParent()), ReplacedArg(Arg),
ReplacementTypes(ReplacementTypes.begin(), ReplacementTypes.end()),
CalleeRepairCB(std::move(CalleeRepairCB)),
ACSRepairCB(std::move(ACSRepairCB)) {}
/// Reference to the attributor to allow access from the callbacks.
Attributor &A;
/// The "old" function replaced by ReplacementFn.
const Function &ReplacedFn;
/// The "old" argument replaced by new ones defined via ReplacementTypes.
const Argument &ReplacedArg;
/// The types of the arguments replacing ReplacedArg.
const SmallVector<Type *, 8> ReplacementTypes;
/// Callee repair callback, see CalleeRepairCBTy.
const CalleeRepairCBTy CalleeRepairCB;
/// Abstract call site (ACS) repair callback, see ACSRepairCBTy.
const ACSRepairCBTy ACSRepairCB;
/// Allow access to the private members from the Attributor.
friend struct Attributor;
};
/// Register a rewrite for a function signature.
///
/// The argument \p Arg is replaced with new ones defined by the number,
/// order, and types in \p ReplacementTypes. The rewiring at the call sites is
/// done through \p ACSRepairCB and at the callee site through
/// \p CalleeRepairCB.
///
/// \returns True, if the replacement was registered, false otherwise.
bool registerFunctionSignatureRewrite(
Argument &Arg, ArrayRef<Type *> ReplacementTypes,
ArgumentReplacementInfo::CalleeRepairCBTy &&CalleeRepairCB,
ArgumentReplacementInfo::ACSRepairCBTy &&ACSRepairCB);
/// Check \p Pred on all function call sites.
///
/// This method will evaluate \p Pred on call sites and return
/// true if \p Pred holds in every call sites. However, this is only possible
/// all call sites are known, hence the function has internal linkage.
bool checkForAllCallSites(const function_ref<bool(AbstractCallSite)> &Pred,
const AbstractAttribute &QueryingAA,
bool RequireAllCallSites);
/// Check \p Pred on all values potentially returned by \p F.
///
/// This method will evaluate \p Pred on all values potentially returned by
/// the function associated with \p QueryingAA. The returned values are
/// matched with their respective return instructions. Returns true if \p Pred
/// holds on all of them.
bool checkForAllReturnedValuesAndReturnInsts(
const function_ref<bool(Value &, const SmallSetVector<ReturnInst *, 4> &)>
&Pred,
const AbstractAttribute &QueryingAA);
/// Check \p Pred on all values potentially returned by the function
/// associated with \p QueryingAA.
///
/// This is the context insensitive version of the method above.
bool checkForAllReturnedValues(const function_ref<bool(Value &)> &Pred,
const AbstractAttribute &QueryingAA);
/// Check \p Pred on all instructions with an opcode present in \p Opcodes.
///
/// This method will evaluate \p Pred on all instructions with an opcode
/// present in \p Opcode and return true if \p Pred holds on all of them.
bool checkForAllInstructions(const function_ref<bool(Instruction &)> &Pred,
const AbstractAttribute &QueryingAA,
const ArrayRef<unsigned> &Opcodes);
/// Check \p Pred on all call-like instructions (=CallBased derived).
///
/// See checkForAllCallLikeInstructions(...) for more information.
bool
checkForAllCallLikeInstructions(const function_ref<bool(Instruction &)> &Pred,
const AbstractAttribute &QueryingAA) {
return checkForAllInstructions(Pred, QueryingAA,
{(unsigned)Instruction::Invoke,
(unsigned)Instruction::CallBr,
(unsigned)Instruction::Call});
}
/// Check \p Pred on all Read/Write instructions.
///
/// This method will evaluate \p Pred on all instructions that read or write
/// to memory present in the information cache and return true if \p Pred
/// holds on all of them.
bool checkForAllReadWriteInstructions(
const llvm::function_ref<bool(Instruction &)> &Pred,
AbstractAttribute &QueryingAA);
/// Return the data layout associated with the anchor scope.
const DataLayout &getDataLayout() const { return InfoCache.DL; }
private:
/// Check \p Pred on all call sites of \p Fn.
///
/// This method will evaluate \p Pred on call sites and return
/// true if \p Pred holds in every call sites. However, this is only possible
/// all call sites are known, hence the function has internal linkage.
bool checkForAllCallSites(const function_ref<bool(AbstractCallSite)> &Pred,
const Function &Fn, bool RequireAllCallSites,
const AbstractAttribute *QueryingAA);
/// The private version of getAAFor that allows to omit a querying abstract
/// attribute. See also the public getAAFor method.
template <typename AAType>
const AAType &getOrCreateAAFor(const IRPosition &IRP,
const AbstractAttribute *QueryingAA = nullptr,
bool TrackDependence = false,
DepClassTy DepClass = DepClassTy::OPTIONAL) {
if (const AAType *AAPtr =
lookupAAFor<AAType>(IRP, QueryingAA, TrackDependence))
return *AAPtr;
// No matching attribute found, create one.
// Use the static create method.
auto &AA = AAType::createForPosition(IRP, *this);
registerAA(AA);
// For now we ignore naked and optnone functions.
bool Invalidate = Whitelist && !Whitelist->count(&AAType::ID);
if (const Function *Fn = IRP.getAnchorScope())
Invalidate |= Fn->hasFnAttribute(Attribute::Naked) ||
Fn->hasFnAttribute(Attribute::OptimizeNone);
// Bootstrap the new attribute with an initial update to propagate
// information, e.g., function -> call site. If it is not on a given
// whitelist we will not perform updates at all.
if (Invalidate) {
AA.getState().indicatePessimisticFixpoint();
return AA;
}
AA.initialize(*this);
AA.update(*this);
if (TrackDependence && AA.getState().isValidState())
recordDependence(AA, const_cast<AbstractAttribute &>(*QueryingAA),
DepClass);
return AA;
}
/// Return the attribute of \p AAType for \p IRP if existing.
template <typename AAType>
const AAType *lookupAAFor(const IRPosition &IRP,
const AbstractAttribute *QueryingAA = nullptr,
bool TrackDependence = false,
DepClassTy DepClass = DepClassTy::OPTIONAL) {
static_assert(std::is_base_of<AbstractAttribute, AAType>::value,
"Cannot query an attribute with a type not derived from "
"'AbstractAttribute'!");
assert((QueryingAA || !TrackDependence) &&
"Cannot track dependences without a QueryingAA!");
// Lookup the abstract attribute of type AAType. If found, return it after
// registering a dependence of QueryingAA on the one returned attribute.
const auto &KindToAbstractAttributeMap = AAMap.lookup(IRP);
if (AAType *AA = static_cast<AAType *>(
KindToAbstractAttributeMap.lookup(&AAType::ID))) {
// Do not register a dependence on an attribute with an invalid state.
if (TrackDependence && AA->getState().isValidState())
recordDependence(*AA, const_cast<AbstractAttribute &>(*QueryingAA),
DepClass);
return AA;
}
return nullptr;
}
/// Apply all requested function signature rewrites
/// (\see registerFunctionSignatureRewrite) and return Changed if the module
/// was altered.
ChangeStatus rewriteFunctionSignatures();
/// The set of all abstract attributes.
///{
using AAVector = SmallVector<AbstractAttribute *, 64>;
AAVector AllAbstractAttributes;
///}
/// A nested map to lookup abstract attributes based on the argument position
/// on the outer level, and the addresses of the static member (AAType::ID) on
/// the inner level.
///{
using KindToAbstractAttributeMap =
DenseMap<const char *, AbstractAttribute *>;
DenseMap<IRPosition, KindToAbstractAttributeMap> AAMap;
///}
/// A map from abstract attributes to the ones that queried them through calls
/// to the getAAFor<...>(...) method.
///{
struct QueryMapValueTy {
/// Set of abstract attributes which were used but not necessarily required
/// for a potential optimistic state.
SetVector<AbstractAttribute *> OptionalAAs;
/// Set of abstract attributes which were used and which were necessarily
/// required for any potential optimistic state.
SetVector<AbstractAttribute *> RequiredAAs;
};
using QueryMapTy = MapVector<const AbstractAttribute *, QueryMapValueTy>;
QueryMapTy QueryMap;
///}
/// Map to remember all requested signature changes (= argument replacements).
DenseMap<Function *, SmallVector<ArgumentReplacementInfo *, 8>>
ArgumentReplacementMap;
/// The information cache that holds pre-processed (LLVM-IR) information.
InformationCache &InfoCache;
/// Set if the attribute currently updated did query a non-fix attribute.
bool QueriedNonFixAA;
/// Number of iterations until the dependences between abstract attributes are
/// recomputed.
const unsigned DepRecomputeInterval;
/// If not null, a set limiting the attribute opportunities.
const DenseSet<const char *> *Whitelist;
/// A set to remember the functions we already assume to be live and visited.
DenseSet<const Function *> VisitedFunctions;
/// Uses we replace with a new value after manifest is done. We will remove
/// then trivially dead instructions as well.
DenseMap<Use *, Value *> ToBeChangedUses;
/// Instructions we replace with `unreachable` insts after manifest is done.
SmallDenseSet<WeakVH, 16> ToBeChangedToUnreachableInsts;
/// Invoke instructions with at least a single dead successor block.
SmallVector<WeakVH, 16> InvokeWithDeadSuccessor;
/// Functions, blocks, and instructions we delete after manifest is done.
///
///{
SmallPtrSet<Function *, 8> ToBeDeletedFunctions;
SmallPtrSet<BasicBlock *, 8> ToBeDeletedBlocks;
SmallPtrSet<Instruction *, 8> ToBeDeletedInsts;
///}
};
/// An interface to query the internal state of an abstract attribute.
///
/// The abstract state is a minimal interface that allows the Attributor to
/// communicate with the abstract attributes about their internal state without
/// enforcing or exposing implementation details, e.g., the (existence of an)
/// underlying lattice.
///
/// It is sufficient to be able to query if a state is (1) valid or invalid, (2)
/// at a fixpoint, and to indicate to the state that (3) an optimistic fixpoint
/// was reached or (4) a pessimistic fixpoint was enforced.
///
/// All methods need to be implemented by the subclass. For the common use case,
/// a single boolean state or a bit-encoded state, the BooleanState and
/// {Inc,Dec,Bit}IntegerState classes are already provided. An abstract
/// attribute can inherit from them to get the abstract state interface and
/// additional methods to directly modify the state based if needed. See the
/// class comments for help.
struct AbstractState {
virtual ~AbstractState() {}
/// Return if this abstract state is in a valid state. If false, no
/// information provided should be used.
virtual bool isValidState() const = 0;
/// Return if this abstract state is fixed, thus does not need to be updated
/// if information changes as it cannot change itself.
virtual bool isAtFixpoint() const = 0;
/// Indicate that the abstract state should converge to the optimistic state.
///
/// This will usually make the optimistically assumed state the known to be
/// true state.
///
/// \returns ChangeStatus::UNCHANGED as the assumed value should not change.
virtual ChangeStatus indicateOptimisticFixpoint() = 0;
/// Indicate that the abstract state should converge to the pessimistic state.
///
/// This will usually revert the optimistically assumed state to the known to
/// be true state.
///
/// \returns ChangeStatus::CHANGED as the assumed value may change.
virtual ChangeStatus indicatePessimisticFixpoint() = 0;
};
/// Simple state with integers encoding.
///
/// The interface ensures that the assumed bits are always a subset of the known
/// bits. Users can only add known bits and, except through adding known bits,
/// they can only remove assumed bits. This should guarantee monotoniticy and
/// thereby the existence of a fixpoint (if used corretly). The fixpoint is
/// reached when the assumed and known state/bits are equal. Users can
/// force/inidicate a fixpoint. If an optimistic one is indicated, the known
/// state will catch up with the assumed one, for a pessimistic fixpoint it is
/// the other way around.
template <typename base_ty, base_ty BestState, base_ty WorstState>
struct IntegerStateBase : public AbstractState {
using base_t = base_ty;
/// Return the best possible representable state.
static constexpr base_t getBestState() { return BestState; }
/// Return the worst possible representable state.
static constexpr base_t getWorstState() { return WorstState; }
/// See AbstractState::isValidState()
/// NOTE: For now we simply pretend that the worst possible state is invalid.
bool isValidState() const override { return Assumed != getWorstState(); }
/// See AbstractState::isAtFixpoint()
bool isAtFixpoint() const override { return Assumed == Known; }
/// See AbstractState::indicateOptimisticFixpoint(...)
ChangeStatus indicateOptimisticFixpoint() override {
Known = Assumed;
return ChangeStatus::UNCHANGED;
}
/// See AbstractState::indicatePessimisticFixpoint(...)
ChangeStatus indicatePessimisticFixpoint() override {
Assumed = Known;
return ChangeStatus::CHANGED;
}
/// Return the known state encoding
base_t getKnown() const { return Known; }
/// Return the assumed state encoding.
base_t getAssumed() const { return Assumed; }
/// Equality for IntegerStateBase.
bool
operator==(const IntegerStateBase<base_t, BestState, WorstState> &R) const {
return this->getAssumed() == R.getAssumed() &&
this->getKnown() == R.getKnown();
}
/// Inequality for IntegerStateBase.
bool
operator!=(const IntegerStateBase<base_t, BestState, WorstState> &R) const {
return !(*this == R);
}
/// "Clamp" this state with \p R. The result is subtype dependent but it is
/// intended that only information assumed in both states will be assumed in
/// this one afterwards.
void operator^=(const IntegerStateBase<base_t, BestState, WorstState> &R) {
handleNewAssumedValue(R.getAssumed());
}
void operator|=(const IntegerStateBase<base_t, BestState, WorstState> &R) {
joinOR(R.getAssumed(), R.getKnown());
}
void operator&=(const IntegerStateBase<base_t, BestState, WorstState> &R) {
joinAND(R.getAssumed(), R.getKnown());
}
protected:
/// Handle a new assumed value \p Value. Subtype dependent.
virtual void handleNewAssumedValue(base_t Value) = 0;
/// Handle a new known value \p Value. Subtype dependent.
virtual void handleNewKnownValue(base_t Value) = 0;
/// Handle a value \p Value. Subtype dependent.
virtual void joinOR(base_t AssumedValue, base_t KnownValue) = 0;
/// Handle a new assumed value \p Value. Subtype dependent.
virtual void joinAND(base_t AssumedValue, base_t KnownValue) = 0;
/// The known state encoding in an integer of type base_t.
base_t Known = getWorstState();
/// The assumed state encoding in an integer of type base_t.
base_t Assumed = getBestState();
};
/// Specialization of the integer state for a bit-wise encoding.
template <typename base_ty = uint32_t, base_ty BestState = ~base_ty(0),
base_ty WorstState = 0>
struct BitIntegerState
: public IntegerStateBase<base_ty, BestState, WorstState> {
using base_t = base_ty;
/// Return true if the bits set in \p BitsEncoding are "known bits".
bool isKnown(base_t BitsEncoding) const {
return (this->Known & BitsEncoding) == BitsEncoding;
}
/// Return true if the bits set in \p BitsEncoding are "assumed bits".
bool isAssumed(base_t BitsEncoding) const {
return (this->Assumed & BitsEncoding) == BitsEncoding;
}
/// Add the bits in \p BitsEncoding to the "known bits".
BitIntegerState &addKnownBits(base_t Bits) {
// Make sure we never miss any "known bits".
this->Assumed |= Bits;
this->Known |= Bits;
return *this;
}
/// Remove the bits in \p BitsEncoding from the "assumed bits" if not known.
BitIntegerState &removeAssumedBits(base_t BitsEncoding) {
return intersectAssumedBits(~BitsEncoding);
}
/// Remove the bits in \p BitsEncoding from the "known bits".
BitIntegerState &removeKnownBits(base_t BitsEncoding) {
this->Known = (this->Known & ~BitsEncoding);
return *this;
}
/// Keep only "assumed bits" also set in \p BitsEncoding but all known ones.
BitIntegerState &intersectAssumedBits(base_t BitsEncoding) {
// Make sure we never loose any "known bits".
this->Assumed = (this->Assumed & BitsEncoding) | this->Known;
return *this;
}
private:
void handleNewAssumedValue(base_t Value) override {
intersectAssumedBits(Value);
}
void handleNewKnownValue(base_t Value) override { addKnownBits(Value); }
void joinOR(base_t AssumedValue, base_t KnownValue) override {
this->Known |= KnownValue;
this->Assumed |= AssumedValue;
}
void joinAND(base_t AssumedValue, base_t KnownValue) override {
this->Known &= KnownValue;
this->Assumed &= AssumedValue;
}
};
/// Specialization of the integer state for an increasing value, hence ~0u is
/// the best state and 0 the worst.
template <typename base_ty = uint32_t, base_ty BestState = ~base_ty(0),
base_ty WorstState = 0>
struct IncIntegerState
: public IntegerStateBase<base_ty, BestState, WorstState> {
using base_t = base_ty;
/// Take minimum of assumed and \p Value.
IncIntegerState &takeAssumedMinimum(base_t Value) {
// Make sure we never loose "known value".
this->Assumed = std::max(std::min(this->Assumed, Value), this->Known);
return *this;
}
/// Take maximum of known and \p Value.
IncIntegerState &takeKnownMaximum(base_t Value) {
// Make sure we never loose "known value".
this->Assumed = std::max(Value, this->Assumed);
this->Known = std::max(Value, this->Known);
return *this;
}
private:
void handleNewAssumedValue(base_t Value) override {
takeAssumedMinimum(Value);
}
void handleNewKnownValue(base_t Value) override { takeKnownMaximum(Value); }
void joinOR(base_t AssumedValue, base_t KnownValue) override {
this->Known = std::max(this->Known, KnownValue);
this->Assumed = std::max(this->Assumed, AssumedValue);
}
void joinAND(base_t AssumedValue, base_t KnownValue) override {
this->Known = std::min(this->Known, KnownValue);
this->Assumed = std::min(this->Assumed, AssumedValue);
}
};
/// Specialization of the integer state for a decreasing value, hence 0 is the
/// best state and ~0u the worst.
template <typename base_ty = uint32_t>
struct DecIntegerState : public IntegerStateBase<base_ty, 0, ~base_ty(0)> {
using base_t = base_ty;
/// Take maximum of assumed and \p Value.
DecIntegerState &takeAssumedMaximum(base_t Value) {
// Make sure we never loose "known value".
this->Assumed = std::min(std::max(this->Assumed, Value), this->Known);
return *this;
}
/// Take minimum of known and \p Value.
DecIntegerState &takeKnownMinimum(base_t Value) {
// Make sure we never loose "known value".
this->Assumed = std::min(Value, this->Assumed);
this->Known = std::min(Value, this->Known);
return *this;
}
private:
void handleNewAssumedValue(base_t Value) override {
takeAssumedMaximum(Value);
}
void handleNewKnownValue(base_t Value) override { takeKnownMinimum(Value); }
void joinOR(base_t AssumedValue, base_t KnownValue) override {
this->Assumed = std::min(this->Assumed, KnownValue);
this->Assumed = std::min(this->Assumed, AssumedValue);
}
void joinAND(base_t AssumedValue, base_t KnownValue) override {
this->Assumed = std::max(this->Assumed, KnownValue);
this->Assumed = std::max(this->Assumed, AssumedValue);
}
};
/// Simple wrapper for a single bit (boolean) state.
struct BooleanState : public IntegerStateBase<bool, 1, 0> {
using base_t = IntegerStateBase::base_t;
/// Set the assumed value to \p Value but never below the known one.
void setAssumed(bool Value) { Assumed &= (Known | Value); }
/// Set the known and asssumed value to \p Value.
void setKnown(bool Value) {
Known |= Value;
Assumed |= Value;
}
/// Return true if the state is assumed to hold.
bool isAssumed() const { return getAssumed(); }
/// Return true if the state is known to hold.
bool isKnown() const { return getKnown(); }
private:
void handleNewAssumedValue(base_t Value) override {
if (!Value)
Assumed = Known;
}
void handleNewKnownValue(base_t Value) override {
if (Value)
Known = (Assumed = Value);
}
void joinOR(base_t AssumedValue, base_t KnownValue) override {
Known |= KnownValue;
Assumed |= AssumedValue;
}
void joinAND(base_t AssumedValue, base_t KnownValue) override {
Known &= KnownValue;
Assumed &= AssumedValue;
}
};
/// State for an integer range.
struct IntegerRangeState : public AbstractState {
/// Bitwidth of the associated value.
uint32_t BitWidth;
/// State representing assumed range, initially set to empty.
ConstantRange Assumed;
/// State representing known range, initially set to [-inf, inf].
ConstantRange Known;
IntegerRangeState(uint32_t BitWidth)
: BitWidth(BitWidth), Assumed(ConstantRange::getEmpty(BitWidth)),
Known(ConstantRange::getFull(BitWidth)) {}
/// Return the worst possible representable state.
static ConstantRange getWorstState(uint32_t BitWidth) {
return ConstantRange::getFull(BitWidth);
}
/// Return the best possible representable state.
static ConstantRange getBestState(uint32_t BitWidth) {
return ConstantRange::getEmpty(BitWidth);
}
/// Return associated values' bit width.
uint32_t getBitWidth() const { return BitWidth; }
/// See AbstractState::isValidState()
bool isValidState() const override {
return BitWidth > 0 && !Assumed.isFullSet();
}
/// See AbstractState::isAtFixpoint()
bool isAtFixpoint() const override { return Assumed == Known; }
/// See AbstractState::indicateOptimisticFixpoint(...)
ChangeStatus indicateOptimisticFixpoint() override {
Known = Assumed;
return ChangeStatus::CHANGED;
}
/// See AbstractState::indicatePessimisticFixpoint(...)
ChangeStatus indicatePessimisticFixpoint() override {
Assumed = Known;
return ChangeStatus::CHANGED;
}
/// Return the known state encoding
ConstantRange getKnown() const { return Known; }
/// Return the assumed state encoding.
ConstantRange getAssumed() const { return Assumed; }
/// Unite assumed range with the passed state.
void unionAssumed(const ConstantRange &R) {
// Don't loose a known range.
Assumed = Assumed.unionWith(R).intersectWith(Known);
}
/// See IntegerRangeState::unionAssumed(..).
void unionAssumed(const IntegerRangeState &R) {
unionAssumed(R.getAssumed());
}
/// Unite known range with the passed state.
void unionKnown(const ConstantRange &R) {
// Don't loose a known range.
Known = Known.unionWith(R);
Assumed = Assumed.unionWith(Known);
}
/// See IntegerRangeState::unionKnown(..).
void unionKnown(const IntegerRangeState &R) { unionKnown(R.getKnown()); }
/// Intersect known range with the passed state.
void intersectKnown(const ConstantRange &R) {
Assumed = Assumed.intersectWith(R);
Known = Known.intersectWith(R);
}
/// See IntegerRangeState::intersectKnown(..).
void intersectKnown(const IntegerRangeState &R) {
intersectKnown(R.getKnown());
}
/// Equality for IntegerRangeState.
bool operator==(const IntegerRangeState &R) const {
return getAssumed() == R.getAssumed() && getKnown() == R.getKnown();
}
/// "Clamp" this state with \p R. The result is subtype dependent but it is
/// intended that only information assumed in both states will be assumed in
/// this one afterwards.
IntegerRangeState operator^=(const IntegerRangeState &R) {
// NOTE: `^=` operator seems like `intersect` but in this case, we need to
// take `union`.
unionAssumed(R);
return *this;
}
IntegerRangeState operator&=(const IntegerRangeState &R) {
// NOTE: `&=` operator seems like `intersect` but in this case, we need to
// take `union`.
unionKnown(R);
unionAssumed(R);
return *this;
}
};
/// Helper struct necessary as the modular build fails if the virtual method
/// IRAttribute::manifest is defined in the Attributor.cpp.
struct IRAttributeManifest {
static ChangeStatus manifestAttrs(Attributor &A, const IRPosition &IRP,
const ArrayRef<Attribute> &DeducedAttrs);
};
/// Helper to tie a abstract state implementation to an abstract attribute.
template <typename StateTy, typename Base>
struct StateWrapper : public StateTy, public Base {
/// Provide static access to the type of the state.
using StateType = StateTy;
/// See AbstractAttribute::getState(...).
StateType &getState() override { return *this; }
/// See AbstractAttribute::getState(...).
const AbstractState &getState() const override { return *this; }
};
/// Helper class that provides common functionality to manifest IR attributes.
template <Attribute::AttrKind AK, typename Base>
struct IRAttribute : public IRPosition, public Base {
IRAttribute(const IRPosition &IRP) : IRPosition(IRP) {}
~IRAttribute() {}
/// See AbstractAttribute::initialize(...).
virtual void initialize(Attributor &A) override {
const IRPosition &IRP = this->getIRPosition();
if (isa<UndefValue>(IRP.getAssociatedValue()) || hasAttr(getAttrKind())) {
this->getState().indicateOptimisticFixpoint();
return;
}
bool IsFnInterface = IRP.isFnInterfaceKind();
const Function *FnScope = IRP.getAnchorScope();
// 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 (IsFnInterface && (!FnScope || !FnScope->hasExactDefinition()))
this->getState().indicatePessimisticFixpoint();
}
/// See AbstractAttribute::manifest(...).
ChangeStatus manifest(Attributor &A) override {
if (isa<UndefValue>(getIRPosition().getAssociatedValue()))
return ChangeStatus::UNCHANGED;
SmallVector<Attribute, 4> DeducedAttrs;
getDeducedAttributes(getAnchorValue().getContext(), DeducedAttrs);
return IRAttributeManifest::manifestAttrs(A, getIRPosition(), DeducedAttrs);
}
/// Return the kind that identifies the abstract attribute implementation.
Attribute::AttrKind getAttrKind() const { return AK; }
/// Return the deduced attributes in \p Attrs.
virtual void getDeducedAttributes(LLVMContext &Ctx,
SmallVectorImpl<Attribute> &Attrs) const {
Attrs.emplace_back(Attribute::get(Ctx, getAttrKind()));
}
/// Return an IR position, see struct IRPosition.
const IRPosition &getIRPosition() const override { return *this; }
};
/// Base struct for all "concrete attribute" deductions.
///
/// The abstract attribute is a minimal interface that allows the Attributor to
/// orchestrate the abstract/fixpoint analysis. The design allows to hide away
/// implementation choices made for the subclasses but also to structure their
/// implementation and simplify the use of other abstract attributes in-flight.
///
/// To allow easy creation of new attributes, most methods have default
/// implementations. The ones that do not are generally straight forward, except
/// `AbstractAttribute::updateImpl` which is the location of most reasoning
/// associated with the abstract attribute. The update is invoked by the
/// Attributor in case the situation used to justify the current optimistic
/// state might have changed. The Attributor determines this automatically
/// by monitoring the `Attributor::getAAFor` calls made by abstract attributes.
///
/// The `updateImpl` method should inspect the IR and other abstract attributes
/// in-flight to justify the best possible (=optimistic) state. The actual
/// implementation is, similar to the underlying abstract state encoding, not
/// exposed. In the most common case, the `updateImpl` will go through a list of
/// reasons why its optimistic state is valid given the current information. If
/// any combination of them holds and is sufficient to justify the current
/// optimistic state, the method shall return UNCHAGED. If not, the optimistic
/// state is adjusted to the situation and the method shall return CHANGED.
///
/// If the manifestation of the "concrete attribute" deduced by the subclass
/// differs from the "default" behavior, which is a (set of) LLVM-IR
/// attribute(s) for an argument, call site argument, function return value, or
/// function, the `AbstractAttribute::manifest` method should be overloaded.
///
/// NOTE: If the state obtained via getState() is INVALID, thus if
/// AbstractAttribute::getState().isValidState() returns false, no
/// information provided by the methods of this class should be used.
/// NOTE: The Attributor currently has certain limitations to what we can do.
/// As a general rule of thumb, "concrete" abstract attributes should *for
/// now* only perform "backward" information propagation. That means
/// optimistic information obtained through abstract attributes should
/// only be used at positions that precede the origin of the information
/// with regards to the program flow. More practically, information can
/// *now* be propagated from instructions to their enclosing function, but
/// *not* from call sites to the called function. The mechanisms to allow
/// both directions will be added in the future.
/// NOTE: The mechanics of adding a new "concrete" abstract attribute are
/// described in the file comment.
struct AbstractAttribute {
using StateType = AbstractState;
/// Virtual destructor.
virtual ~AbstractAttribute() {}
/// Initialize the state with the information in the Attributor \p A.
///
/// This function is called by the Attributor once all abstract attributes
/// have been identified. It can and shall be used for task like:
/// - identify existing knowledge in the IR and use it for the "known state"
/// - perform any work that is not going to change over time, e.g., determine
/// a subset of the IR, or attributes in-flight, that have to be looked at
/// in the `updateImpl` method.
virtual void initialize(Attributor &A) {}
/// Return the internal abstract state for inspection.
virtual StateType &getState() = 0;
virtual const StateType &getState() const = 0;
/// Return an IR position, see struct IRPosition.
virtual const IRPosition &getIRPosition() const = 0;
/// Helper functions, for debug purposes only.
///{
virtual void print(raw_ostream &OS) const;
void dump() const { print(dbgs()); }
/// This function should return the "summarized" assumed state as string.
virtual const std::string getAsStr() const = 0;
///}
/// Allow the Attributor access to the protected methods.
friend struct Attributor;
protected:
/// Hook for the Attributor to trigger an update of the internal state.
///
/// If this attribute is already fixed, this method will return UNCHANGED,
/// otherwise it delegates to `AbstractAttribute::updateImpl`.
///
/// \Return CHANGED if the internal state changed, otherwise UNCHANGED.
ChangeStatus update(Attributor &A);
/// Hook for the Attributor to trigger the manifestation of the information
/// represented by the abstract attribute in the LLVM-IR.
///
/// \Return CHANGED if the IR was altered, otherwise UNCHANGED.
virtual ChangeStatus manifest(Attributor &A) {
return ChangeStatus::UNCHANGED;
}
/// Hook to enable custom statistic tracking, called after manifest that
/// resulted in a change if statistics are enabled.
///
/// We require subclasses to provide an implementation so we remember to
/// add statistics for them.
virtual void trackStatistics() const = 0;
/// The actual update/transfer function which has to be implemented by the
/// derived classes.
///
/// If it is called, the environment has changed and we have to determine if
/// the current information is still valid or adjust it otherwise.
///
/// \Return CHANGED if the internal state changed, otherwise UNCHANGED.
virtual ChangeStatus updateImpl(Attributor &A) = 0;
};
/// Forward declarations of output streams for debug purposes.
///
///{
raw_ostream &operator<<(raw_ostream &OS, const AbstractAttribute &AA);
raw_ostream &operator<<(raw_ostream &OS, ChangeStatus S);
raw_ostream &operator<<(raw_ostream &OS, IRPosition::Kind);
raw_ostream &operator<<(raw_ostream &OS, const IRPosition &);
raw_ostream &operator<<(raw_ostream &OS, const AbstractState &State);
template <typename base_ty, base_ty BestState, base_ty WorstState>
raw_ostream &
operator<<(raw_ostream &OS,
const IntegerStateBase<base_ty, BestState, WorstState> &State);
raw_ostream &operator<<(raw_ostream &OS, const IntegerRangeState &State);
///}
struct AttributorPass : public PassInfoMixin<AttributorPass> {
PreservedAnalyses run(Module &M, ModuleAnalysisManager &AM);
};
Pass *createAttributorLegacyPass();
/// ----------------------------------------------------------------------------
/// Abstract Attribute Classes
/// ----------------------------------------------------------------------------
/// An abstract attribute for the returned values of a function.
struct AAReturnedValues
: public IRAttribute<Attribute::Returned, AbstractAttribute> {
AAReturnedValues(const IRPosition &IRP) : IRAttribute(IRP) {}
/// 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;
/// Check \p Pred on all returned values.
///
/// This method will evaluate \p Pred on returned values and return
/// true if (1) all returned values are known, and (2) \p Pred returned true
/// for all returned values.
///
/// Note: Unlike the Attributor::checkForAllReturnedValuesAndReturnInsts
/// method, this one will not filter dead return instructions.
virtual bool checkForAllReturnedValuesAndReturnInsts(
const function_ref<bool(Value &, const SmallSetVector<ReturnInst *, 4> &)>
&Pred) const = 0;
using iterator =
MapVector<Value *, SmallSetVector<ReturnInst *, 4>>::iterator;
using const_iterator =
MapVector<Value *, SmallSetVector<ReturnInst *, 4>>::const_iterator;
virtual llvm::iterator_range<iterator> returned_values() = 0;
virtual llvm::iterator_range<const_iterator> returned_values() const = 0;
virtual size_t getNumReturnValues() const = 0;
virtual const SmallSetVector<CallBase *, 4> &getUnresolvedCalls() const = 0;
/// Create an abstract attribute view for the position \p IRP.
static AAReturnedValues &createForPosition(const IRPosition &IRP,
Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
struct AANoUnwind
: public IRAttribute<Attribute::NoUnwind,
StateWrapper<BooleanState, AbstractAttribute>> {
AANoUnwind(const IRPosition &IRP) : IRAttribute(IRP) {}
/// Returns true if nounwind is assumed.
bool isAssumedNoUnwind() const { return getAssumed(); }
/// Returns true if nounwind is known.
bool isKnownNoUnwind() const { return getKnown(); }
/// Create an abstract attribute view for the position \p IRP.
static AANoUnwind &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
struct AANoSync
: public IRAttribute<Attribute::NoSync,
StateWrapper<BooleanState, AbstractAttribute>> {
AANoSync(const IRPosition &IRP) : IRAttribute(IRP) {}
/// Returns true if "nosync" is assumed.
bool isAssumedNoSync() const { return getAssumed(); }
/// Returns true if "nosync" is known.
bool isKnownNoSync() const { return getKnown(); }
/// Create an abstract attribute view for the position \p IRP.
static AANoSync &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract interface for all nonnull attributes.
struct AANonNull
: public IRAttribute<Attribute::NonNull,
StateWrapper<BooleanState, AbstractAttribute>> {
AANonNull(const IRPosition &IRP) : IRAttribute(IRP) {}
/// Return true if we assume that the underlying value is nonnull.
bool isAssumedNonNull() const { return getAssumed(); }
/// Return true if we know that underlying value is nonnull.
bool isKnownNonNull() const { return getKnown(); }
/// Create an abstract attribute view for the position \p IRP.
static AANonNull &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract attribute for norecurse.
struct AANoRecurse
: public IRAttribute<Attribute::NoRecurse,
StateWrapper<BooleanState, AbstractAttribute>> {
AANoRecurse(const IRPosition &IRP) : IRAttribute(IRP) {}
/// Return true if "norecurse" is assumed.
bool isAssumedNoRecurse() const { return getAssumed(); }
/// Return true if "norecurse" is known.
bool isKnownNoRecurse() const { return getKnown(); }
/// Create an abstract attribute view for the position \p IRP.
static AANoRecurse &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract attribute for willreturn.
struct AAWillReturn
: public IRAttribute<Attribute::WillReturn,
StateWrapper<BooleanState, AbstractAttribute>> {
AAWillReturn(const IRPosition &IRP) : IRAttribute(IRP) {}
/// Return true if "willreturn" is assumed.
bool isAssumedWillReturn() const { return getAssumed(); }
/// Return true if "willreturn" is known.
bool isKnownWillReturn() const { return getKnown(); }
/// Create an abstract attribute view for the position \p IRP.
static AAWillReturn &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract attribute for undefined behavior.
struct AAUndefinedBehavior
: public StateWrapper<BooleanState, AbstractAttribute>,
public IRPosition {
AAUndefinedBehavior(const IRPosition &IRP) : IRPosition(IRP) {}
/// Return true if "undefined behavior" is assumed.
bool isAssumedToCauseUB() const { return getAssumed(); }
/// Return true if "undefined behavior" is assumed for a specific instruction.
virtual bool isAssumedToCauseUB(Instruction *I) const = 0;
/// Return true if "undefined behavior" is known.
bool isKnownToCauseUB() const { return getKnown(); }
/// Return true if "undefined behavior" is known for a specific instruction.
virtual bool isKnownToCauseUB(Instruction *I) const = 0;
/// Return an IR position, see struct IRPosition.
const IRPosition &getIRPosition() const override { return *this; }
/// Create an abstract attribute view for the position \p IRP.
static AAUndefinedBehavior &createForPosition(const IRPosition &IRP,
Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract interface to determine reachability of point A to B.
struct AAReachability : public StateWrapper<BooleanState, AbstractAttribute>,
public IRPosition {
AAReachability(const IRPosition &IRP) : IRPosition(IRP) {}
/// Returns true if 'From' instruction is assumed to reach, 'To' instruction.
/// Users should provide two positions they are interested in, and the class
/// determines (and caches) reachability.
bool isAssumedReachable(const Instruction *From,
const Instruction *To) const {
return true;
}
/// Returns true if 'From' instruction is known to reach, 'To' instruction.
/// Users should provide two positions they are interested in, and the class
/// determines (and caches) reachability.
bool isKnownReachable(const Instruction *From, const Instruction *To) const {
return true;
}
/// Return an IR position, see struct IRPosition.
const IRPosition &getIRPosition() const override { return *this; }
/// Create an abstract attribute view for the position \p IRP.
static AAReachability &createForPosition(const IRPosition &IRP,
Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract interface for all noalias attributes.
struct AANoAlias
: public IRAttribute<Attribute::NoAlias,
StateWrapper<BooleanState, AbstractAttribute>> {
AANoAlias(const IRPosition &IRP) : IRAttribute(IRP) {}
/// Return true if we assume that the underlying value is alias.
bool isAssumedNoAlias() const { return getAssumed(); }
/// Return true if we know that underlying value is noalias.
bool isKnownNoAlias() const { return getKnown(); }
/// Create an abstract attribute view for the position \p IRP.
static AANoAlias &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An AbstractAttribute for nofree.
struct AANoFree
: public IRAttribute<Attribute::NoFree,
StateWrapper<BooleanState, AbstractAttribute>> {
AANoFree(const IRPosition &IRP) : IRAttribute(IRP) {}
/// Return true if "nofree" is assumed.
bool isAssumedNoFree() const { return getAssumed(); }
/// Return true if "nofree" is known.
bool isKnownNoFree() const { return getKnown(); }
/// Create an abstract attribute view for the position \p IRP.
static AANoFree &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An AbstractAttribute for noreturn.
struct AANoReturn
: public IRAttribute<Attribute::NoReturn,
StateWrapper<BooleanState, AbstractAttribute>> {
AANoReturn(const IRPosition &IRP) : IRAttribute(IRP) {}
/// Return true if the underlying object is assumed to never return.
bool isAssumedNoReturn() const { return getAssumed(); }
/// Return true if the underlying object is known to never return.
bool isKnownNoReturn() const { return getKnown(); }
/// Create an abstract attribute view for the position \p IRP.
static AANoReturn &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract interface for liveness abstract attribute.
struct AAIsDead : public StateWrapper<BooleanState, AbstractAttribute>,
public IRPosition {
AAIsDead(const IRPosition &IRP) : IRPosition(IRP) {}
/// Returns true if the underlying value is assumed dead.
virtual bool isAssumedDead() const = 0;
/// Returns true if \p BB is assumed dead.
virtual bool isAssumedDead(const BasicBlock *BB) const = 0;
/// Returns true if \p BB is known dead.
virtual bool isKnownDead(const BasicBlock *BB) const = 0;
/// Returns true if \p I is assumed dead.
virtual bool isAssumedDead(const Instruction *I) const = 0;
/// Returns true if \p I is known dead.
virtual bool isKnownDead(const Instruction *I) const = 0;
/// This method is used to check if at least one instruction in a collection
/// of instructions is live.
template <typename T> bool isLiveInstSet(T begin, T end) const {
for (const auto &I : llvm::make_range(begin, end)) {
assert(I->getFunction() == getIRPosition().getAssociatedFunction() &&
"Instruction must be in the same anchor scope function.");
if (!isAssumedDead(I))
return true;
}
return false;
}
/// Return an IR position, see struct IRPosition.
const IRPosition &getIRPosition() const override { return *this; }
/// Create an abstract attribute view for the position \p IRP.
static AAIsDead &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// State for dereferenceable attribute
struct DerefState : AbstractState {
/// State representing for dereferenceable bytes.
IncIntegerState<> DerefBytesState;
/// Map representing for accessed memory offsets and sizes.
/// A key is Offset and a value is size.
/// If there is a load/store instruction something like,
/// p[offset] = v;
/// (offset, sizeof(v)) will be inserted to this map.
/// std::map is used because we want to iterate keys in ascending order.
std::map<int64_t, uint64_t> AccessedBytesMap;
/// Helper function to calculate dereferenceable bytes from current known
/// bytes and accessed bytes.
///
/// int f(int *A){
/// *A = 0;
/// *(A+2) = 2;
/// *(A+1) = 1;
/// *(A+10) = 10;
/// }
/// ```
/// In that case, AccessedBytesMap is `{0:4, 4:4, 8:4, 40:4}`.
/// AccessedBytesMap is std::map so it is iterated in accending order on
/// key(Offset). So KnownBytes will be updated like this:
///
/// |Access | KnownBytes
/// |(0, 4)| 0 -> 4
/// |(4, 4)| 4 -> 8
/// |(8, 4)| 8 -> 12
/// |(40, 4) | 12 (break)
void computeKnownDerefBytesFromAccessedMap() {
int64_t KnownBytes = DerefBytesState.getKnown();
for (auto &Access : AccessedBytesMap) {
if (KnownBytes < Access.first)
break;
KnownBytes = std::max(KnownBytes, Access.first + (int64_t)Access.second);
}
DerefBytesState.takeKnownMaximum(KnownBytes);
}
/// State representing that whether the value is globaly dereferenceable.
BooleanState GlobalState;
/// See AbstractState::isValidState()
bool isValidState() const override { return DerefBytesState.isValidState(); }
/// See AbstractState::isAtFixpoint()
bool isAtFixpoint() const override {
return !isValidState() ||
(DerefBytesState.isAtFixpoint() && GlobalState.isAtFixpoint());
}
/// See AbstractState::indicateOptimisticFixpoint(...)
ChangeStatus indicateOptimisticFixpoint() override {
DerefBytesState.indicateOptimisticFixpoint();
GlobalState.indicateOptimisticFixpoint();
return ChangeStatus::UNCHANGED;
}
/// See AbstractState::indicatePessimisticFixpoint(...)
ChangeStatus indicatePessimisticFixpoint() override {
DerefBytesState.indicatePessimisticFixpoint();
GlobalState.indicatePessimisticFixpoint();
return ChangeStatus::CHANGED;
}
/// Update known dereferenceable bytes.
void takeKnownDerefBytesMaximum(uint64_t Bytes) {
DerefBytesState.takeKnownMaximum(Bytes);
// Known bytes might increase.
computeKnownDerefBytesFromAccessedMap();
}
/// Update assumed dereferenceable bytes.
void takeAssumedDerefBytesMinimum(uint64_t Bytes) {
DerefBytesState.takeAssumedMinimum(Bytes);
}
/// Add accessed bytes to the map.
void addAccessedBytes(int64_t Offset, uint64_t Size) {
AccessedBytesMap[Offset] = std::max(AccessedBytesMap[Offset], Size);
// Known bytes might increase.
computeKnownDerefBytesFromAccessedMap();
}
/// Equality for DerefState.
bool operator==(const DerefState &R) {
return this->DerefBytesState == R.DerefBytesState &&
this->GlobalState == R.GlobalState;
}
/// Inequality for DerefState.
bool operator!=(const DerefState &R) { return !(*this == R); }
/// See IntegerStateBase::operator^=
DerefState operator^=(const DerefState &R) {
DerefBytesState ^= R.DerefBytesState;
GlobalState ^= R.GlobalState;
return *this;
}
/// See IntegerStateBase::operator&=
DerefState operator&=(const DerefState &R) {
DerefBytesState &= R.DerefBytesState;
GlobalState &= R.GlobalState;
return *this;
}
/// See IntegerStateBase::operator|=
DerefState operator|=(const DerefState &R) {
DerefBytesState |= R.DerefBytesState;
GlobalState |= R.GlobalState;
return *this;
}
protected:
const AANonNull *NonNullAA = nullptr;
};
/// An abstract interface for all dereferenceable attribute.
struct AADereferenceable
: public IRAttribute<Attribute::Dereferenceable,
StateWrapper<DerefState, AbstractAttribute>> {
AADereferenceable(const IRPosition &IRP) : IRAttribute(IRP) {}
/// Return true if we assume that the underlying value is nonnull.
bool isAssumedNonNull() const {
return NonNullAA && NonNullAA->isAssumedNonNull();
}
/// Return true if we know that the underlying value is nonnull.
bool isKnownNonNull() const {
return NonNullAA && NonNullAA->isKnownNonNull();
}
/// Return true if we assume that underlying value is
/// dereferenceable(_or_null) globally.
bool isAssumedGlobal() const { return GlobalState.getAssumed(); }
/// Return true if we know that underlying value is
/// dereferenceable(_or_null) globally.
bool isKnownGlobal() const { return GlobalState.getKnown(); }
/// Return assumed dereferenceable bytes.
uint32_t getAssumedDereferenceableBytes() const {
return DerefBytesState.getAssumed();
}
/// Return known dereferenceable bytes.
uint32_t getKnownDereferenceableBytes() const {
return DerefBytesState.getKnown();
}
/// Create an abstract attribute view for the position \p IRP.
static AADereferenceable &createForPosition(const IRPosition &IRP,
Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
using AAAlignmentStateType =
IncIntegerState<uint32_t, /* maximal alignment */ 1U << 29, 0>;
/// An abstract interface for all align attributes.
struct AAAlign : public IRAttribute<
Attribute::Alignment,
StateWrapper<AAAlignmentStateType, AbstractAttribute>> {
AAAlign(const IRPosition &IRP) : IRAttribute(IRP) {}
/// Return assumed alignment.
unsigned getAssumedAlign() const { return getAssumed(); }
/// Return known alignment.
unsigned getKnownAlign() const { return getKnown(); }
/// Create an abstract attribute view for the position \p IRP.
static AAAlign &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract interface for all nocapture attributes.
struct AANoCapture
: public IRAttribute<
Attribute::NoCapture,
StateWrapper<BitIntegerState<uint16_t, 7, 0>, AbstractAttribute>> {
AANoCapture(const IRPosition &IRP) : IRAttribute(IRP) {}
/// State encoding bits. A set bit in the state means the property holds.
/// NO_CAPTURE is the best possible state, 0 the worst possible state.
enum {
NOT_CAPTURED_IN_MEM = 1 << 0,
NOT_CAPTURED_IN_INT = 1 << 1,
NOT_CAPTURED_IN_RET = 1 << 2,
/// If we do not capture the value in memory or through integers we can only
/// communicate it back as a derived pointer.
NO_CAPTURE_MAYBE_RETURNED = NOT_CAPTURED_IN_MEM | NOT_CAPTURED_IN_INT,
/// If we do not capture the value in memory, through integers, or as a
/// derived pointer we know it is not captured.
NO_CAPTURE =
NOT_CAPTURED_IN_MEM | NOT_CAPTURED_IN_INT | NOT_CAPTURED_IN_RET,
};
/// Return true if we know that the underlying value is not captured in its
/// respective scope.
bool isKnownNoCapture() const { return isKnown(NO_CAPTURE); }
/// Return true if we assume that the underlying value is not captured in its
/// respective scope.
bool isAssumedNoCapture() const { return isAssumed(NO_CAPTURE); }
/// Return true if we know that the underlying value is not captured in its
/// respective scope but we allow it to escape through a "return".
bool isKnownNoCaptureMaybeReturned() const {
return isKnown(NO_CAPTURE_MAYBE_RETURNED);
}
/// Return true if we assume that the underlying value is not captured in its
/// respective scope but we allow it to escape through a "return".
bool isAssumedNoCaptureMaybeReturned() const {
return isAssumed(NO_CAPTURE_MAYBE_RETURNED);
}
/// Create an abstract attribute view for the position \p IRP.
static AANoCapture &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract interface for value simplify abstract attribute.
struct AAValueSimplify : public StateWrapper<BooleanState, AbstractAttribute>,
public IRPosition {
AAValueSimplify(const IRPosition &IRP) : IRPosition(IRP) {}
/// Return an IR position, see struct IRPosition.
const IRPosition &getIRPosition() const { return *this; }
/// Return an assumed simplified value if a single candidate is found. If
/// there cannot be one, return original value. If it is not clear yet, return
/// the Optional::NoneType.
virtual Optional<Value *> getAssumedSimplifiedValue(Attributor &A) const = 0;
/// Create an abstract attribute view for the position \p IRP.
static AAValueSimplify &createForPosition(const IRPosition &IRP,
Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
struct AAHeapToStack : public StateWrapper<BooleanState, AbstractAttribute>,
public IRPosition {
AAHeapToStack(const IRPosition &IRP) : IRPosition(IRP) {}
/// Returns true if HeapToStack conversion is assumed to be possible.
bool isAssumedHeapToStack() const { return getAssumed(); }
/// Returns true if HeapToStack conversion is known to be possible.
bool isKnownHeapToStack() const { return getKnown(); }
/// Return an IR position, see struct IRPosition.
const IRPosition &getIRPosition() const { return *this; }
/// Create an abstract attribute view for the position \p IRP.
static AAHeapToStack &createForPosition(const IRPosition &IRP, Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract interface for all memory related attributes.
struct AAMemoryBehavior
: public IRAttribute<
Attribute::ReadNone,
StateWrapper<BitIntegerState<uint8_t, 3>, AbstractAttribute>> {
AAMemoryBehavior(const IRPosition &IRP) : IRAttribute(IRP) {}
/// State encoding bits. A set bit in the state means the property holds.
/// BEST_STATE is the best possible state, 0 the worst possible state.
enum {
NO_READS = 1 << 0,
NO_WRITES = 1 << 1,
NO_ACCESSES = NO_READS | NO_WRITES,
BEST_STATE = NO_ACCESSES,
};
/// Return true if we know that the underlying value is not read or accessed
/// in its respective scope.
bool isKnownReadNone() const { return isKnown(NO_ACCESSES); }
/// Return true if we assume that the underlying value is not read or accessed
/// in its respective scope.
bool isAssumedReadNone() const { return isAssumed(NO_ACCESSES); }
/// Return true if we know that the underlying value is not accessed
/// (=written) in its respective scope.
bool isKnownReadOnly() const { return isKnown(NO_WRITES); }
/// Return true if we assume that the underlying value is not accessed
/// (=written) in its respective scope.
bool isAssumedReadOnly() const { return isAssumed(NO_WRITES); }
/// Return true if we know that the underlying value is not read in its
/// respective scope.
bool isKnownWriteOnly() const { return isKnown(NO_READS); }
/// Return true if we assume that the underlying value is not read in its
/// respective scope.
bool isAssumedWriteOnly() const { return isAssumed(NO_READS); }
/// Create an abstract attribute view for the position \p IRP.
static AAMemoryBehavior &createForPosition(const IRPosition &IRP,
Attributor &A);
/// Unique ID (due to the unique address)
static const char ID;
};
/// An abstract interface for range value analysis.
struct AAValueConstantRange : public IntegerRangeState,
public AbstractAttribute,
public IRPosition {
AAValueConstantRange(const IRPosition &IRP)
: IntegerRangeState(
IRP.getAssociatedValue().getType()->getIntegerBitWidth()),
IRPosition(IRP) {}
/// Return an IR position, see struct IRPosition.
const IRPosition &getIRPosition() const override { return *this; }
/// See AbstractAttribute::getState(...).
IntegerRangeState &getState() override { return *this; }
const AbstractState &getState() const override { return *this; }
/// Create an abstract attribute view for the position \p IRP.
static AAValueConstantRange &createForPosition(const IRPosition &IRP,
Attributor &A);
/// Return an assumed range for the assocaited value a program point \p CtxI.
/// If \p I is nullptr, simply return an assumed range.
virtual ConstantRange
getAssumedConstantRange(Attributor &A,
const Instruction *CtxI = nullptr) const = 0;
/// Return a known range for the assocaited value at a program point \p CtxI.
/// If \p I is nullptr, simply return a known range.
virtual ConstantRange
getKnownConstantRange(Attributor &A,
const Instruction *CtxI = nullptr) const = 0;
/// Return an assumed constant for the assocaited value a program point \p
/// CtxI.
Optional<ConstantInt *>
getAssumedConstantInt(Attributor &A, const Instruction *CtxI = nullptr) const {
ConstantRange RangeV = getAssumedConstantRange(A, CtxI);
if (auto *C = RangeV.getSingleElement())
return cast<ConstantInt>(
ConstantInt::get(getAssociatedValue().getType(), *C));
if (RangeV.isEmptySet())
return llvm::None;
return nullptr;
}
/// Unique ID (due to the unique address)
static const char ID;
};
} // end namespace llvm
#endif // LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H
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