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AliasAnalysis.h
//===- llvm/Analysis/AliasAnalysis.h - Alias Analysis Interface -*- 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
//
//===----------------------------------------------------------------------===//
//
// This file defines the generic AliasAnalysis interface, which is used as the
// common interface used by all clients of alias analysis information, and
// implemented by all alias analysis implementations. Mod/Ref information is
// also captured by this interface.
//
// Implementations of this interface must implement the various virtual methods,
// which automatically provides functionality for the entire suite of client
// APIs.
//
// This API identifies memory regions with the MemoryLocation class. The pointer
// component specifies the base memory address of the region. The Size specifies
// the maximum size (in address units) of the memory region, or
// MemoryLocation::UnknownSize if the size is not known. The TBAA tag
// identifies the "type" of the memory reference; see the
// TypeBasedAliasAnalysis class for details.
//
// Some non-obvious details include:
// - Pointers that point to two completely different objects in memory never
// alias, regardless of the value of the Size component.
// - NoAlias doesn't imply inequal pointers. The most obvious example of this
// is two pointers to constant memory. Even if they are equal, constant
// memory is never stored to, so there will never be any dependencies.
// In this and other situations, the pointers may be both NoAlias and
// MustAlias at the same time. The current API can only return one result,
// though this is rarely a problem in practice.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_ANALYSIS_ALIASANALYSIS_H
#define LLVM_ANALYSIS_ALIASANALYSIS_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/Analysis/MemoryLocation.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/PassManager.h"
#include "llvm/Pass.h"
#include <cstdint>
#include <functional>
#include <memory>
#include <vector>
namespace llvm {
class AnalysisUsage;
class BasicAAResult;
class BasicBlock;
class DominatorTree;
class OrderedBasicBlock;
class Value;
/// The possible results of an alias query.
///
/// These results are always computed between two MemoryLocation objects as
/// a query to some alias analysis.
///
/// Note that these are unscoped enumerations because we would like to support
/// implicitly testing a result for the existence of any possible aliasing with
/// a conversion to bool, but an "enum class" doesn't support this. The
/// canonical names from the literature are suffixed and unique anyways, and so
/// they serve as global constants in LLVM for these results.
///
/// See docs/AliasAnalysis.html for more information on the specific meanings
/// of these values.
enum AliasResult : uint8_t {
/// The two locations do not alias at all.
///
/// This value is arranged to convert to false, while all other values
/// convert to true. This allows a boolean context to convert the result to
/// a binary flag indicating whether there is the possibility of aliasing.
NoAlias = 0,
/// The two locations may or may not alias. This is the least precise result.
MayAlias,
/// The two locations alias, but only due to a partial overlap.
PartialAlias,
/// The two locations precisely alias each other.
MustAlias,
};
/// << operator for AliasResult.
raw_ostream &operator<<(raw_ostream &OS, AliasResult AR);
/// Flags indicating whether a memory access modifies or references memory.
///
/// This is no access at all, a modification, a reference, or both
/// a modification and a reference. These are specifically structured such that
/// they form a three bit matrix and bit-tests for 'mod' or 'ref' or 'must'
/// work with any of the possible values.
enum class ModRefInfo : uint8_t {
/// Must is provided for completeness, but no routines will return only
/// Must today. See definition of Must below.
Must = 0,
/// The access may reference the value stored in memory,
/// a mustAlias relation was found, and no mayAlias or partialAlias found.
MustRef = 1,
/// The access may modify the value stored in memory,
/// a mustAlias relation was found, and no mayAlias or partialAlias found.
MustMod = 2,
/// The access may reference, modify or both the value stored in memory,
/// a mustAlias relation was found, and no mayAlias or partialAlias found.
MustModRef = MustRef | MustMod,
/// The access neither references nor modifies the value stored in memory.
NoModRef = 4,
/// The access may reference the value stored in memory.
Ref = NoModRef | MustRef,
/// The access may modify the value stored in memory.
Mod = NoModRef | MustMod,
/// The access may reference and may modify the value stored in memory.
ModRef = Ref | Mod,
/// About Must:
/// Must is set in a best effort manner.
/// We usually do not try our best to infer Must, instead it is merely
/// another piece of "free" information that is presented when available.
/// Must set means there was certainly a MustAlias found. For calls,
/// where multiple arguments are checked (argmemonly), this translates to
/// only MustAlias or NoAlias was found.
/// Must is not set for RAR accesses, even if the two locations must
/// alias. The reason is that two read accesses translate to an early return
/// of NoModRef. An additional alias check to set Must may be
/// expensive. Other cases may also not set Must(e.g. callCapturesBefore).
/// We refer to Must being *set* when the most significant bit is *cleared*.
/// Conversely we *clear* Must information by *setting* the Must bit to 1.
};
LLVM_NODISCARD inline bool isNoModRef(const ModRefInfo MRI) {
return (static_cast<int>(MRI) & static_cast<int>(ModRefInfo::MustModRef)) ==
static_cast<int>(ModRefInfo::Must);
}
LLVM_NODISCARD inline bool isModOrRefSet(const ModRefInfo MRI) {
return static_cast<int>(MRI) & static_cast<int>(ModRefInfo::MustModRef);
}
LLVM_NODISCARD inline bool isModAndRefSet(const ModRefInfo MRI) {
return (static_cast<int>(MRI) & static_cast<int>(ModRefInfo::MustModRef)) ==
static_cast<int>(ModRefInfo::MustModRef);
}
LLVM_NODISCARD inline bool isModSet(const ModRefInfo MRI) {
return static_cast<int>(MRI) & static_cast<int>(ModRefInfo::MustMod);
}
LLVM_NODISCARD inline bool isRefSet(const ModRefInfo MRI) {
return static_cast<int>(MRI) & static_cast<int>(ModRefInfo::MustRef);
}
LLVM_NODISCARD inline bool isMustSet(const ModRefInfo MRI) {
return !(static_cast<int>(MRI) & static_cast<int>(ModRefInfo::NoModRef));
}
LLVM_NODISCARD inline ModRefInfo setMod(const ModRefInfo MRI) {
return ModRefInfo(static_cast<int>(MRI) |
static_cast<int>(ModRefInfo::MustMod));
}
LLVM_NODISCARD inline ModRefInfo setRef(const ModRefInfo MRI) {
return ModRefInfo(static_cast<int>(MRI) |
static_cast<int>(ModRefInfo::MustRef));
}
LLVM_NODISCARD inline ModRefInfo setMust(const ModRefInfo MRI) {
return ModRefInfo(static_cast<int>(MRI) &
static_cast<int>(ModRefInfo::MustModRef));
}
LLVM_NODISCARD inline ModRefInfo setModAndRef(const ModRefInfo MRI) {
return ModRefInfo(static_cast<int>(MRI) |
static_cast<int>(ModRefInfo::MustModRef));
}
LLVM_NODISCARD inline ModRefInfo clearMod(const ModRefInfo MRI) {
return ModRefInfo(static_cast<int>(MRI) & static_cast<int>(ModRefInfo::Ref));
}
LLVM_NODISCARD inline ModRefInfo clearRef(const ModRefInfo MRI) {
return ModRefInfo(static_cast<int>(MRI) & static_cast<int>(ModRefInfo::Mod));
}
LLVM_NODISCARD inline ModRefInfo clearMust(const ModRefInfo MRI) {
return ModRefInfo(static_cast<int>(MRI) |
static_cast<int>(ModRefInfo::NoModRef));
}
LLVM_NODISCARD inline ModRefInfo unionModRef(const ModRefInfo MRI1,
const ModRefInfo MRI2) {
return ModRefInfo(static_cast<int>(MRI1) | static_cast<int>(MRI2));
}
LLVM_NODISCARD inline ModRefInfo intersectModRef(const ModRefInfo MRI1,
const ModRefInfo MRI2) {
return ModRefInfo(static_cast<int>(MRI1) & static_cast<int>(MRI2));
}
/// The locations at which a function might access memory.
///
/// These are primarily used in conjunction with the \c AccessKind bits to
/// describe both the nature of access and the locations of access for a
/// function call.
enum FunctionModRefLocation {
/// Base case is no access to memory.
FMRL_Nowhere = 0,
/// Access to memory via argument pointers.
FMRL_ArgumentPointees = 8,
/// Memory that is inaccessible via LLVM IR.
FMRL_InaccessibleMem = 16,
/// Access to any memory.
FMRL_Anywhere = 32 | FMRL_InaccessibleMem | FMRL_ArgumentPointees
};
/// Summary of how a function affects memory in the program.
///
/// Loads from constant globals are not considered memory accesses for this
/// interface. Also, functions may freely modify stack space local to their
/// invocation without having to report it through these interfaces.
enum FunctionModRefBehavior {
/// This function does not perform any non-local loads or stores to memory.
///
/// This property corresponds to the GCC 'const' attribute.
/// This property corresponds to the LLVM IR 'readnone' attribute.
/// This property corresponds to the IntrNoMem LLVM intrinsic flag.
FMRB_DoesNotAccessMemory =
FMRL_Nowhere | static_cast<int>(ModRefInfo::NoModRef),
/// The only memory references in this function (if it has any) are
/// non-volatile loads from objects pointed to by its pointer-typed
/// arguments, with arbitrary offsets.
///
/// This property corresponds to the IntrReadArgMem LLVM intrinsic flag.
FMRB_OnlyReadsArgumentPointees =
FMRL_ArgumentPointees | static_cast<int>(ModRefInfo::Ref),
/// The only memory references in this function (if it has any) are
/// non-volatile loads and stores from objects pointed to by its
/// pointer-typed arguments, with arbitrary offsets.
///
/// This property corresponds to the IntrArgMemOnly LLVM intrinsic flag.
FMRB_OnlyAccessesArgumentPointees =
FMRL_ArgumentPointees | static_cast<int>(ModRefInfo::ModRef),
/// The only memory references in this function (if it has any) are
/// references of memory that is otherwise inaccessible via LLVM IR.
///
/// This property corresponds to the LLVM IR inaccessiblememonly attribute.
FMRB_OnlyAccessesInaccessibleMem =
FMRL_InaccessibleMem | static_cast<int>(ModRefInfo::ModRef),
/// The function may perform non-volatile loads and stores of objects
/// pointed to by its pointer-typed arguments, with arbitrary offsets, and
/// it may also perform loads and stores of memory that is otherwise
/// inaccessible via LLVM IR.
///
/// This property corresponds to the LLVM IR
/// inaccessiblemem_or_argmemonly attribute.
FMRB_OnlyAccessesInaccessibleOrArgMem = FMRL_InaccessibleMem |
FMRL_ArgumentPointees |
static_cast<int>(ModRefInfo::ModRef),
/// This function does not perform any non-local stores or volatile loads,
/// but may read from any memory location.
///
/// This property corresponds to the GCC 'pure' attribute.
/// This property corresponds to the LLVM IR 'readonly' attribute.
/// This property corresponds to the IntrReadMem LLVM intrinsic flag.
FMRB_OnlyReadsMemory = FMRL_Anywhere | static_cast<int>(ModRefInfo::Ref),
// This function does not read from memory anywhere, but may write to any
// memory location.
//
// This property corresponds to the LLVM IR 'writeonly' attribute.
// This property corresponds to the IntrWriteMem LLVM intrinsic flag.
FMRB_DoesNotReadMemory = FMRL_Anywhere | static_cast<int>(ModRefInfo::Mod),
/// This indicates that the function could not be classified into one of the
/// behaviors above.
FMRB_UnknownModRefBehavior =
FMRL_Anywhere | static_cast<int>(ModRefInfo::ModRef)
};
// Wrapper method strips bits significant only in FunctionModRefBehavior,
// to obtain a valid ModRefInfo. The benefit of using the wrapper is that if
// ModRefInfo enum changes, the wrapper can be updated to & with the new enum
// entry with all bits set to 1.
LLVM_NODISCARD inline ModRefInfo
createModRefInfo(const FunctionModRefBehavior FMRB) {
return ModRefInfo(FMRB & static_cast<int>(ModRefInfo::ModRef));
}
/// This class stores info we want to provide to or retain within an alias
/// query. By default, the root query is stateless and starts with a freshly
/// constructed info object. Specific alias analyses can use this query info to
/// store per-query state that is important for recursive or nested queries to
/// avoid recomputing. To enable preserving this state across multiple queries
/// where safe (due to the IR not changing), use a `BatchAAResults` wrapper.
/// The information stored in an `AAQueryInfo` is currently limitted to the
/// caches used by BasicAA, but can further be extended to fit other AA needs.
class AAQueryInfo {
public:
using LocPair = std::pair<MemoryLocation, MemoryLocation>;
using AliasCacheT = SmallDenseMap<LocPair, AliasResult, 8>;
AliasCacheT AliasCache;
using IsCapturedCacheT = SmallDenseMap<const Value *, bool, 8>;
IsCapturedCacheT IsCapturedCache;
AAQueryInfo() : AliasCache(), IsCapturedCache() {}
};
class BatchAAResults;
class AAResults {
public:
// Make these results default constructable and movable. We have to spell
// these out because MSVC won't synthesize them.
AAResults(const TargetLibraryInfo &TLI) : TLI(TLI) {}
AAResults(AAResults &&Arg);
~AAResults();
/// Register a specific AA result.
template <typename AAResultT> void addAAResult(AAResultT &AAResult) {
// FIXME: We should use a much lighter weight system than the usual
// polymorphic pattern because we don't own AAResult. It should
// ideally involve two pointers and no separate allocation.
AAs.emplace_back(new Model<AAResultT>(AAResult, *this));
}
/// Register a function analysis ID that the results aggregation depends on.
///
/// This is used in the new pass manager to implement the invalidation logic
/// where we must invalidate the results aggregation if any of our component
/// analyses become invalid.
void addAADependencyID(AnalysisKey *ID) { AADeps.push_back(ID); }
/// Handle invalidation events in the new pass manager.
///
/// The aggregation is invalidated if any of the underlying analyses is
/// invalidated.
bool invalidate(Function &F, const PreservedAnalyses &PA,
FunctionAnalysisManager::Invalidator &Inv);
//===--------------------------------------------------------------------===//
/// \name Alias Queries
/// @{
/// The main low level interface to the alias analysis implementation.
/// Returns an AliasResult indicating whether the two pointers are aliased to
/// each other. This is the interface that must be implemented by specific
/// alias analysis implementations.
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB);
/// A convenience wrapper around the primary \c alias interface.
AliasResult alias(const Value *V1, LocationSize V1Size, const Value *V2,
LocationSize V2Size) {
return alias(MemoryLocation(V1, V1Size), MemoryLocation(V2, V2Size));
}
/// A convenience wrapper around the primary \c alias interface.
AliasResult alias(const Value *V1, const Value *V2) {
return alias(V1, LocationSize::unknown(), V2, LocationSize::unknown());
}
/// A trivial helper function to check to see if the specified pointers are
/// no-alias.
bool isNoAlias(const MemoryLocation &LocA, const MemoryLocation &LocB) {
return alias(LocA, LocB) == NoAlias;
}
/// A convenience wrapper around the \c isNoAlias helper interface.
bool isNoAlias(const Value *V1, LocationSize V1Size, const Value *V2,
LocationSize V2Size) {
return isNoAlias(MemoryLocation(V1, V1Size), MemoryLocation(V2, V2Size));
}
/// A convenience wrapper around the \c isNoAlias helper interface.
bool isNoAlias(const Value *V1, const Value *V2) {
return isNoAlias(MemoryLocation(V1), MemoryLocation(V2));
}
/// A trivial helper function to check to see if the specified pointers are
/// must-alias.
bool isMustAlias(const MemoryLocation &LocA, const MemoryLocation &LocB) {
return alias(LocA, LocB) == MustAlias;
}
/// A convenience wrapper around the \c isMustAlias helper interface.
bool isMustAlias(const Value *V1, const Value *V2) {
return alias(V1, LocationSize::precise(1), V2, LocationSize::precise(1)) ==
MustAlias;
}
/// Checks whether the given location points to constant memory, or if
/// \p OrLocal is true whether it points to a local alloca.
bool pointsToConstantMemory(const MemoryLocation &Loc, bool OrLocal = false);
/// A convenience wrapper around the primary \c pointsToConstantMemory
/// interface.
bool pointsToConstantMemory(const Value *P, bool OrLocal = false) {
return pointsToConstantMemory(MemoryLocation(P), OrLocal);
}
/// @}
//===--------------------------------------------------------------------===//
/// \name Simple mod/ref information
/// @{
/// Get the ModRef info associated with a pointer argument of a call. The
/// result's bits are set to indicate the allowed aliasing ModRef kinds. Note
/// that these bits do not necessarily account for the overall behavior of
/// the function, but rather only provide additional per-argument
/// information. This never sets ModRefInfo::Must.
ModRefInfo getArgModRefInfo(const CallBase *Call, unsigned ArgIdx);
/// Return the behavior of the given call site.
FunctionModRefBehavior getModRefBehavior(const CallBase *Call);
/// Return the behavior when calling the given function.
FunctionModRefBehavior getModRefBehavior(const Function *F);
/// Checks if the specified call is known to never read or write memory.
///
/// Note that if the call only reads from known-constant memory, it is also
/// legal to return true. Also, calls that unwind the stack are legal for
/// this predicate.
///
/// Many optimizations (such as CSE and LICM) can be performed on such calls
/// without worrying about aliasing properties, and many calls have this
/// property (e.g. calls to 'sin' and 'cos').
///
/// This property corresponds to the GCC 'const' attribute.
bool doesNotAccessMemory(const CallBase *Call) {
return getModRefBehavior(Call) == FMRB_DoesNotAccessMemory;
}
/// Checks if the specified function is known to never read or write memory.
///
/// Note that if the function only reads from known-constant memory, it is
/// also legal to return true. Also, function that unwind the stack are legal
/// for this predicate.
///
/// Many optimizations (such as CSE and LICM) can be performed on such calls
/// to such functions without worrying about aliasing properties, and many
/// functions have this property (e.g. 'sin' and 'cos').
///
/// This property corresponds to the GCC 'const' attribute.
bool doesNotAccessMemory(const Function *F) {
return getModRefBehavior(F) == FMRB_DoesNotAccessMemory;
}
/// Checks if the specified call is known to only read from non-volatile
/// memory (or not access memory at all).
///
/// Calls that unwind the stack are legal for this predicate.
///
/// This property allows many common optimizations to be performed in the
/// absence of interfering store instructions, such as CSE of strlen calls.
///
/// This property corresponds to the GCC 'pure' attribute.
bool onlyReadsMemory(const CallBase *Call) {
return onlyReadsMemory(getModRefBehavior(Call));
}
/// Checks if the specified function is known to only read from non-volatile
/// memory (or not access memory at all).
///
/// Functions that unwind the stack are legal for this predicate.
///
/// This property allows many common optimizations to be performed in the
/// absence of interfering store instructions, such as CSE of strlen calls.
///
/// This property corresponds to the GCC 'pure' attribute.
bool onlyReadsMemory(const Function *F) {
return onlyReadsMemory(getModRefBehavior(F));
}
/// Checks if functions with the specified behavior are known to only read
/// from non-volatile memory (or not access memory at all).
static bool onlyReadsMemory(FunctionModRefBehavior MRB) {
return !isModSet(createModRefInfo(MRB));
}
/// Checks if functions with the specified behavior are known to only write
/// memory (or not access memory at all).
static bool doesNotReadMemory(FunctionModRefBehavior MRB) {
return !isRefSet(createModRefInfo(MRB));
}
/// Checks if functions with the specified behavior are known to read and
/// write at most from objects pointed to by their pointer-typed arguments
/// (with arbitrary offsets).
static bool onlyAccessesArgPointees(FunctionModRefBehavior MRB) {
return !(MRB & FMRL_Anywhere & ~FMRL_ArgumentPointees);
}
/// Checks if functions with the specified behavior are known to potentially
/// read or write from objects pointed to be their pointer-typed arguments
/// (with arbitrary offsets).
static bool doesAccessArgPointees(FunctionModRefBehavior MRB) {
return isModOrRefSet(createModRefInfo(MRB)) &&
(MRB & FMRL_ArgumentPointees);
}
/// Checks if functions with the specified behavior are known to read and
/// write at most from memory that is inaccessible from LLVM IR.
static bool onlyAccessesInaccessibleMem(FunctionModRefBehavior MRB) {
return !(MRB & FMRL_Anywhere & ~FMRL_InaccessibleMem);
}
/// Checks if functions with the specified behavior are known to potentially
/// read or write from memory that is inaccessible from LLVM IR.
static bool doesAccessInaccessibleMem(FunctionModRefBehavior MRB) {
return isModOrRefSet(createModRefInfo(MRB)) && (MRB & FMRL_InaccessibleMem);
}
/// Checks if functions with the specified behavior are known to read and
/// write at most from memory that is inaccessible from LLVM IR or objects
/// pointed to by their pointer-typed arguments (with arbitrary offsets).
static bool onlyAccessesInaccessibleOrArgMem(FunctionModRefBehavior MRB) {
return !(MRB & FMRL_Anywhere &
~(FMRL_InaccessibleMem | FMRL_ArgumentPointees));
}
/// getModRefInfo (for call sites) - Return information about whether
/// a particular call site modifies or reads the specified memory location.
ModRefInfo getModRefInfo(const CallBase *Call, const MemoryLocation &Loc);
/// getModRefInfo (for call sites) - A convenience wrapper.
ModRefInfo getModRefInfo(const CallBase *Call, const Value *P,
LocationSize Size) {
return getModRefInfo(Call, MemoryLocation(P, Size));
}
/// getModRefInfo (for loads) - Return information about whether
/// a particular load modifies or reads the specified memory location.
ModRefInfo getModRefInfo(const LoadInst *L, const MemoryLocation &Loc);
/// getModRefInfo (for loads) - A convenience wrapper.
ModRefInfo getModRefInfo(const LoadInst *L, const Value *P,
LocationSize Size) {
return getModRefInfo(L, MemoryLocation(P, Size));
}
/// getModRefInfo (for stores) - Return information about whether
/// a particular store modifies or reads the specified memory location.
ModRefInfo getModRefInfo(const StoreInst *S, const MemoryLocation &Loc);
/// getModRefInfo (for stores) - A convenience wrapper.
ModRefInfo getModRefInfo(const StoreInst *S, const Value *P,
LocationSize Size) {
return getModRefInfo(S, MemoryLocation(P, Size));
}
/// getModRefInfo (for fences) - Return information about whether
/// a particular store modifies or reads the specified memory location.
ModRefInfo getModRefInfo(const FenceInst *S, const MemoryLocation &Loc);
/// getModRefInfo (for fences) - A convenience wrapper.
ModRefInfo getModRefInfo(const FenceInst *S, const Value *P,
LocationSize Size) {
return getModRefInfo(S, MemoryLocation(P, Size));
}
/// getModRefInfo (for cmpxchges) - Return information about whether
/// a particular cmpxchg modifies or reads the specified memory location.
ModRefInfo getModRefInfo(const AtomicCmpXchgInst *CX,
const MemoryLocation &Loc);
/// getModRefInfo (for cmpxchges) - A convenience wrapper.
ModRefInfo getModRefInfo(const AtomicCmpXchgInst *CX, const Value *P,
LocationSize Size) {
return getModRefInfo(CX, MemoryLocation(P, Size));
}
/// getModRefInfo (for atomicrmws) - Return information about whether
/// a particular atomicrmw modifies or reads the specified memory location.
ModRefInfo getModRefInfo(const AtomicRMWInst *RMW, const MemoryLocation &Loc);
/// getModRefInfo (for atomicrmws) - A convenience wrapper.
ModRefInfo getModRefInfo(const AtomicRMWInst *RMW, const Value *P,
LocationSize Size) {
return getModRefInfo(RMW, MemoryLocation(P, Size));
}
/// getModRefInfo (for va_args) - Return information about whether
/// a particular va_arg modifies or reads the specified memory location.
ModRefInfo getModRefInfo(const VAArgInst *I, const MemoryLocation &Loc);
/// getModRefInfo (for va_args) - A convenience wrapper.
ModRefInfo getModRefInfo(const VAArgInst *I, const Value *P,
LocationSize Size) {
return getModRefInfo(I, MemoryLocation(P, Size));
}
/// getModRefInfo (for catchpads) - Return information about whether
/// a particular catchpad modifies or reads the specified memory location.
ModRefInfo getModRefInfo(const CatchPadInst *I, const MemoryLocation &Loc);
/// getModRefInfo (for catchpads) - A convenience wrapper.
ModRefInfo getModRefInfo(const CatchPadInst *I, const Value *P,
LocationSize Size) {
return getModRefInfo(I, MemoryLocation(P, Size));
}
/// getModRefInfo (for catchrets) - Return information about whether
/// a particular catchret modifies or reads the specified memory location.
ModRefInfo getModRefInfo(const CatchReturnInst *I, const MemoryLocation &Loc);
/// getModRefInfo (for catchrets) - A convenience wrapper.
ModRefInfo getModRefInfo(const CatchReturnInst *I, const Value *P,
LocationSize Size) {
return getModRefInfo(I, MemoryLocation(P, Size));
}
/// Check whether or not an instruction may read or write the optionally
/// specified memory location.
///
///
/// An instruction that doesn't read or write memory may be trivially LICM'd
/// for example.
///
/// For function calls, this delegates to the alias-analysis specific
/// call-site mod-ref behavior queries. Otherwise it delegates to the specific
/// helpers above.
ModRefInfo getModRefInfo(const Instruction *I,
const Optional<MemoryLocation> &OptLoc) {
AAQueryInfo AAQIP;
return getModRefInfo(I, OptLoc, AAQIP);
}
/// A convenience wrapper for constructing the memory location.
ModRefInfo getModRefInfo(const Instruction *I, const Value *P,
LocationSize Size) {
return getModRefInfo(I, MemoryLocation(P, Size));
}
/// Return information about whether a call and an instruction may refer to
/// the same memory locations.
ModRefInfo getModRefInfo(Instruction *I, const CallBase *Call);
/// Return information about whether two call sites may refer to the same set
/// of memory locations. See the AA documentation for details:
/// http://llvm.org/docs/AliasAnalysis.html#ModRefInfo
ModRefInfo getModRefInfo(const CallBase *Call1, const CallBase *Call2);
/// Return information about whether a particular call site modifies
/// or reads the specified memory location \p MemLoc before instruction \p I
/// in a BasicBlock. An ordered basic block \p OBB can be used to speed up
/// instruction ordering queries inside the BasicBlock containing \p I.
/// Early exits in callCapturesBefore may lead to ModRefInfo::Must not being
/// set.
ModRefInfo callCapturesBefore(const Instruction *I,
const MemoryLocation &MemLoc, DominatorTree *DT,
OrderedBasicBlock *OBB = nullptr);
/// A convenience wrapper to synthesize a memory location.
ModRefInfo callCapturesBefore(const Instruction *I, const Value *P,
LocationSize Size, DominatorTree *DT,
OrderedBasicBlock *OBB = nullptr) {
return callCapturesBefore(I, MemoryLocation(P, Size), DT, OBB);
}
/// @}
//===--------------------------------------------------------------------===//
/// \name Higher level methods for querying mod/ref information.
/// @{
/// Check if it is possible for execution of the specified basic block to
/// modify the location Loc.
bool canBasicBlockModify(const BasicBlock &BB, const MemoryLocation &Loc);
/// A convenience wrapper synthesizing a memory location.
bool canBasicBlockModify(const BasicBlock &BB, const Value *P,
LocationSize Size) {
return canBasicBlockModify(BB, MemoryLocation(P, Size));
}
/// Check if it is possible for the execution of the specified instructions
/// to mod\ref (according to the mode) the location Loc.
///
/// The instructions to consider are all of the instructions in the range of
/// [I1,I2] INCLUSIVE. I1 and I2 must be in the same basic block.
bool canInstructionRangeModRef(const Instruction &I1, const Instruction &I2,
const MemoryLocation &Loc,
const ModRefInfo Mode);
/// A convenience wrapper synthesizing a memory location.
bool canInstructionRangeModRef(const Instruction &I1, const Instruction &I2,
const Value *Ptr, LocationSize Size,
const ModRefInfo Mode) {
return canInstructionRangeModRef(I1, I2, MemoryLocation(Ptr, Size), Mode);
}
private:
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB,
AAQueryInfo &AAQI);
bool pointsToConstantMemory(const MemoryLocation &Loc, AAQueryInfo &AAQI,
bool OrLocal = false);
ModRefInfo getModRefInfo(Instruction *I, const CallBase *Call2,
AAQueryInfo &AAQIP);
ModRefInfo getModRefInfo(const CallBase *Call, const MemoryLocation &Loc,
AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const CallBase *Call1, const CallBase *Call2,
AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const VAArgInst *V, const MemoryLocation &Loc,
AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const LoadInst *L, const MemoryLocation &Loc,
AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const StoreInst *S, const MemoryLocation &Loc,
AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const FenceInst *S, const MemoryLocation &Loc,
AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const AtomicCmpXchgInst *CX,
const MemoryLocation &Loc, AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const AtomicRMWInst *RMW, const MemoryLocation &Loc,
AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const CatchPadInst *I, const MemoryLocation &Loc,
AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const CatchReturnInst *I, const MemoryLocation &Loc,
AAQueryInfo &AAQI);
ModRefInfo getModRefInfo(const Instruction *I,
const Optional<MemoryLocation> &OptLoc,
AAQueryInfo &AAQIP) {
if (OptLoc == None) {
if (const auto *Call = dyn_cast<CallBase>(I)) {
return createModRefInfo(getModRefBehavior(Call));
}
}
const MemoryLocation &Loc = OptLoc.getValueOr(MemoryLocation());
switch (I->getOpcode()) {
case Instruction::VAArg:
return getModRefInfo((const VAArgInst *)I, Loc, AAQIP);
case Instruction::Load:
return getModRefInfo((const LoadInst *)I, Loc, AAQIP);
case Instruction::Store:
return getModRefInfo((const StoreInst *)I, Loc, AAQIP);
case Instruction::Fence:
return getModRefInfo((const FenceInst *)I, Loc, AAQIP);
case Instruction::AtomicCmpXchg:
return getModRefInfo((const AtomicCmpXchgInst *)I, Loc, AAQIP);
case Instruction::AtomicRMW:
return getModRefInfo((const AtomicRMWInst *)I, Loc, AAQIP);
case Instruction::Call:
return getModRefInfo((const CallInst *)I, Loc, AAQIP);
case Instruction::Invoke:
return getModRefInfo((const InvokeInst *)I, Loc, AAQIP);
case Instruction::CatchPad:
return getModRefInfo((const CatchPadInst *)I, Loc, AAQIP);
case Instruction::CatchRet:
return getModRefInfo((const CatchReturnInst *)I, Loc, AAQIP);
default:
return ModRefInfo::NoModRef;
}
}
class Concept;
template <typename T> class Model;
template <typename T> friend class AAResultBase;
const TargetLibraryInfo &TLI;
std::vector<std::unique_ptr<Concept>> AAs;
std::vector<AnalysisKey *> AADeps;
friend class BatchAAResults;
};
/// This class is a wrapper over an AAResults, and it is intended to be used
/// only when there are no IR changes inbetween queries. BatchAAResults is
/// reusing the same `AAQueryInfo` to preserve the state across queries,
/// esentially making AA work in "batch mode". The internal state cannot be
/// cleared, so to go "out-of-batch-mode", the user must either use AAResults,
/// or create a new BatchAAResults.
class BatchAAResults {
AAResults &AA;
AAQueryInfo AAQI;
public:
BatchAAResults(AAResults &AAR) : AA(AAR), AAQI() {}
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB) {
return AA.alias(LocA, LocB, AAQI);
}
bool pointsToConstantMemory(const MemoryLocation &Loc, bool OrLocal = false) {
return AA.pointsToConstantMemory(Loc, AAQI, OrLocal);
}
ModRefInfo getModRefInfo(const CallBase *Call, const MemoryLocation &Loc) {
return AA.getModRefInfo(Call, Loc, AAQI);
}
ModRefInfo getModRefInfo(const CallBase *Call1, const CallBase *Call2) {
return AA.getModRefInfo(Call1, Call2, AAQI);
}
ModRefInfo getModRefInfo(const Instruction *I,
const Optional<MemoryLocation> &OptLoc) {
return AA.getModRefInfo(I, OptLoc, AAQI);
}
ModRefInfo getModRefInfo(Instruction *I, const CallBase *Call2) {
return AA.getModRefInfo(I, Call2, AAQI);
}
ModRefInfo getArgModRefInfo(const CallBase *Call, unsigned ArgIdx) {
return AA.getArgModRefInfo(Call, ArgIdx);
}
FunctionModRefBehavior getModRefBehavior(const CallBase *Call) {
return AA.getModRefBehavior(Call);
}
};
/// Temporary typedef for legacy code that uses a generic \c AliasAnalysis
/// pointer or reference.
using AliasAnalysis = AAResults;
/// A private abstract base class describing the concept of an individual alias
/// analysis implementation.
///
/// This interface is implemented by any \c Model instantiation. It is also the
/// interface which a type used to instantiate the model must provide.
///
/// All of these methods model methods by the same name in the \c
/// AAResults class. Only differences and specifics to how the
/// implementations are called are documented here.
class AAResults::Concept {
public:
virtual ~Concept() = 0;
/// An update API used internally by the AAResults to provide
/// a handle back to the top level aggregation.
virtual void setAAResults(AAResults *NewAAR) = 0;
//===--------------------------------------------------------------------===//
/// \name Alias Queries
/// @{
/// The main low level interface to the alias analysis implementation.
/// Returns an AliasResult indicating whether the two pointers are aliased to
/// each other. This is the interface that must be implemented by specific
/// alias analysis implementations.
virtual AliasResult alias(const MemoryLocation &LocA,
const MemoryLocation &LocB, AAQueryInfo &AAQI) = 0;
/// Checks whether the given location points to constant memory, or if
/// \p OrLocal is true whether it points to a local alloca.
virtual bool pointsToConstantMemory(const MemoryLocation &Loc,
AAQueryInfo &AAQI, bool OrLocal) = 0;
/// @}
//===--------------------------------------------------------------------===//
/// \name Simple mod/ref information
/// @{
/// Get the ModRef info associated with a pointer argument of a callsite. The
/// result's bits are set to indicate the allowed aliasing ModRef kinds. Note
/// that these bits do not necessarily account for the overall behavior of
/// the function, but rather only provide additional per-argument
/// information.
virtual ModRefInfo getArgModRefInfo(const CallBase *Call,
unsigned ArgIdx) = 0;
/// Return the behavior of the given call site.
virtual FunctionModRefBehavior getModRefBehavior(const CallBase *Call) = 0;
/// Return the behavior when calling the given function.
virtual FunctionModRefBehavior getModRefBehavior(const Function *F) = 0;
/// getModRefInfo (for call sites) - Return information about whether
/// a particular call site modifies or reads the specified memory location.
virtual ModRefInfo getModRefInfo(const CallBase *Call,
const MemoryLocation &Loc,
AAQueryInfo &AAQI) = 0;
/// Return information about whether two call sites may refer to the same set
/// of memory locations. See the AA documentation for details:
/// http://llvm.org/docs/AliasAnalysis.html#ModRefInfo
virtual ModRefInfo getModRefInfo(const CallBase *Call1, const CallBase *Call2,
AAQueryInfo &AAQI) = 0;
/// @}
};
/// A private class template which derives from \c Concept and wraps some other
/// type.
///
/// This models the concept by directly forwarding each interface point to the
/// wrapped type which must implement a compatible interface. This provides
/// a type erased binding.
template <typename AAResultT> class AAResults::Model final : public Concept {
AAResultT &Result;
public:
explicit Model(AAResultT &Result, AAResults &AAR) : Result(Result) {
Result.setAAResults(&AAR);
}
~Model() override = default;
void setAAResults(AAResults *NewAAR) override { Result.setAAResults(NewAAR); }
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB,
AAQueryInfo &AAQI) override {
return Result.alias(LocA, LocB, AAQI);
}
bool pointsToConstantMemory(const MemoryLocation &Loc, AAQueryInfo &AAQI,
bool OrLocal) override {
return Result.pointsToConstantMemory(Loc, AAQI, OrLocal);
}
ModRefInfo getArgModRefInfo(const CallBase *Call, unsigned ArgIdx) override {
return Result.getArgModRefInfo(Call, ArgIdx);
}
FunctionModRefBehavior getModRefBehavior(const CallBase *Call) override {
return Result.getModRefBehavior(Call);
}
FunctionModRefBehavior getModRefBehavior(const Function *F) override {
return Result.getModRefBehavior(F);
}
ModRefInfo getModRefInfo(const CallBase *Call, const MemoryLocation &Loc,
AAQueryInfo &AAQI) override {
return Result.getModRefInfo(Call, Loc, AAQI);
}
ModRefInfo getModRefInfo(const CallBase *Call1, const CallBase *Call2,
AAQueryInfo &AAQI) override {
return Result.getModRefInfo(Call1, Call2, AAQI);
}
};
/// A CRTP-driven "mixin" base class to help implement the function alias
/// analysis results concept.
///
/// Because of the nature of many alias analysis implementations, they often
/// only implement a subset of the interface. This base class will attempt to
/// implement the remaining portions of the interface in terms of simpler forms
/// of the interface where possible, and otherwise provide conservatively
/// correct fallback implementations.
///
/// Implementors of an alias analysis should derive from this CRTP, and then
/// override specific methods that they wish to customize. There is no need to
/// use virtual anywhere, the CRTP base class does static dispatch to the
/// derived type passed into it.
template <typename DerivedT> class AAResultBase {
// Expose some parts of the interface only to the AAResults::Model
// for wrapping. Specifically, this allows the model to call our
// setAAResults method without exposing it as a fully public API.
friend class AAResults::Model<DerivedT>;
/// A pointer to the AAResults object that this AAResult is
/// aggregated within. May be null if not aggregated.
AAResults *AAR = nullptr;
/// Helper to dispatch calls back through the derived type.
DerivedT &derived() { return static_cast<DerivedT &>(*this); }
/// A setter for the AAResults pointer, which is used to satisfy the
/// AAResults::Model contract.
void setAAResults(AAResults *NewAAR) { AAR = NewAAR; }
protected:
/// This proxy class models a common pattern where we delegate to either the
/// top-level \c AAResults aggregation if one is registered, or to the
/// current result if none are registered.
class AAResultsProxy {
AAResults *AAR;
DerivedT &CurrentResult;
public:
AAResultsProxy(AAResults *AAR, DerivedT &CurrentResult)
: AAR(AAR), CurrentResult(CurrentResult) {}
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB,
AAQueryInfo &AAQI) {
return AAR ? AAR->alias(LocA, LocB, AAQI)
: CurrentResult.alias(LocA, LocB, AAQI);
}
bool pointsToConstantMemory(const MemoryLocation &Loc, AAQueryInfo &AAQI,
bool OrLocal) {
return AAR ? AAR->pointsToConstantMemory(Loc, AAQI, OrLocal)
: CurrentResult.pointsToConstantMemory(Loc, AAQI, OrLocal);
}
ModRefInfo getArgModRefInfo(const CallBase *Call, unsigned ArgIdx) {
return AAR ? AAR->getArgModRefInfo(Call, ArgIdx)
: CurrentResult.getArgModRefInfo(Call, ArgIdx);
}
FunctionModRefBehavior getModRefBehavior(const CallBase *Call) {
return AAR ? AAR->getModRefBehavior(Call)
: CurrentResult.getModRefBehavior(Call);
}
FunctionModRefBehavior getModRefBehavior(const Function *F) {
return AAR ? AAR->getModRefBehavior(F) : CurrentResult.getModRefBehavior(F);
}
ModRefInfo getModRefInfo(const CallBase *Call, const MemoryLocation &Loc,
AAQueryInfo &AAQI) {
return AAR ? AAR->getModRefInfo(Call, Loc, AAQI)
: CurrentResult.getModRefInfo(Call, Loc, AAQI);
}
ModRefInfo getModRefInfo(const CallBase *Call1, const CallBase *Call2,
AAQueryInfo &AAQI) {
return AAR ? AAR->getModRefInfo(Call1, Call2, AAQI)
: CurrentResult.getModRefInfo(Call1, Call2, AAQI);
}
};
explicit AAResultBase() = default;
// Provide all the copy and move constructors so that derived types aren't
// constrained.
AAResultBase(const AAResultBase &Arg) {}
AAResultBase(AAResultBase &&Arg) {}
/// Get a proxy for the best AA result set to query at this time.
///
/// When this result is part of a larger aggregation, this will proxy to that
/// aggregation. When this result is used in isolation, it will just delegate
/// back to the derived class's implementation.
///
/// Note that callers of this need to take considerable care to not cause
/// performance problems when they use this routine, in the case of a large
/// number of alias analyses being aggregated, it can be expensive to walk
/// back across the chain.
AAResultsProxy getBestAAResults() { return AAResultsProxy(AAR, derived()); }
public:
AliasResult alias(const MemoryLocation &LocA, const MemoryLocation &LocB,
AAQueryInfo &AAQI) {
return MayAlias;
}
bool pointsToConstantMemory(const MemoryLocation &Loc, AAQueryInfo &AAQI,
bool OrLocal) {
return false;
}
ModRefInfo getArgModRefInfo(const CallBase *Call, unsigned ArgIdx) {
return ModRefInfo::ModRef;
}
FunctionModRefBehavior getModRefBehavior(const CallBase *Call) {
return FMRB_UnknownModRefBehavior;
}
FunctionModRefBehavior getModRefBehavior(const Function *F) {
return FMRB_UnknownModRefBehavior;
}
ModRefInfo getModRefInfo(const CallBase *Call, const MemoryLocation &Loc,
AAQueryInfo &AAQI) {
return ModRefInfo::ModRef;
}
ModRefInfo getModRefInfo(const CallBase *Call1, const CallBase *Call2,
AAQueryInfo &AAQI) {
return ModRefInfo::ModRef;
}
};
/// Return true if this pointer is returned by a noalias function.
bool isNoAliasCall(const Value *V);
/// Return true if this is an argument with the noalias attribute.
bool isNoAliasArgument(const Value *V);
/// Return true if this pointer refers to a distinct and identifiable object.
/// This returns true for:
/// Global Variables and Functions (but not Global Aliases)
/// Allocas
/// ByVal and NoAlias Arguments
/// NoAlias returns (e.g. calls to malloc)
///
bool isIdentifiedObject(const Value *V);
/// Return true if V is umabigously identified at the function-level.
/// Different IdentifiedFunctionLocals can't alias.
/// Further, an IdentifiedFunctionLocal can not alias with any function
/// arguments other than itself, which is not necessarily true for
/// IdentifiedObjects.
bool isIdentifiedFunctionLocal(const Value *V);
/// A manager for alias analyses.
///
/// This class can have analyses registered with it and when run, it will run
/// all of them and aggregate their results into single AA results interface
/// that dispatches across all of the alias analysis results available.
///
/// Note that the order in which analyses are registered is very significant.
/// That is the order in which the results will be aggregated and queried.
///
/// This manager effectively wraps the AnalysisManager for registering alias
/// analyses. When you register your alias analysis with this manager, it will
/// ensure the analysis itself is registered with its AnalysisManager.
///
/// The result of this analysis is only invalidated if one of the particular
/// aggregated AA results end up being invalidated. This removes the need to
/// explicitly preserve the results of `AAManager`. Note that analyses should no
/// longer be registered once the `AAManager` is run.
class AAManager : public AnalysisInfoMixin<AAManager> {
public:
using Result = AAResults;
/// Register a specific AA result.
template <typename AnalysisT> void registerFunctionAnalysis() {
ResultGetters.push_back(&getFunctionAAResultImpl<AnalysisT>);
}
/// Register a specific AA result.
template <typename AnalysisT> void registerModuleAnalysis() {
ResultGetters.push_back(&getModuleAAResultImpl<AnalysisT>);
}
Result run(Function &F, FunctionAnalysisManager &AM) {
Result R(AM.getResult<TargetLibraryAnalysis>(F));
for (auto &Getter : ResultGetters)
(*Getter)(F, AM, R);
return R;
}
private:
friend AnalysisInfoMixin<AAManager>;
static AnalysisKey Key;
SmallVector<void (*)(Function &F, FunctionAnalysisManager &AM,
AAResults &AAResults),
4> ResultGetters;
template <typename AnalysisT>
static void getFunctionAAResultImpl(Function &F,
FunctionAnalysisManager &AM,
AAResults &AAResults) {
AAResults.addAAResult(AM.template getResult<AnalysisT>(F));
AAResults.addAADependencyID(AnalysisT::ID());
}
template <typename AnalysisT>
static void getModuleAAResultImpl(Function &F, FunctionAnalysisManager &AM,
AAResults &AAResults) {
auto &MAMProxy = AM.getResult<ModuleAnalysisManagerFunctionProxy>(F);
auto &MAM = MAMProxy.getManager();
if (auto *R = MAM.template getCachedResult<AnalysisT>(*F.getParent())) {
AAResults.addAAResult(*R);
MAMProxy
.template registerOuterAnalysisInvalidation<AnalysisT, AAManager>();
}
}
};
/// A wrapper pass to provide the legacy pass manager access to a suitably
/// prepared AAResults object.
class AAResultsWrapperPass : public FunctionPass {
std::unique_ptr<AAResults> AAR;
public:
static char ID;
AAResultsWrapperPass();
AAResults &getAAResults() { return *AAR; }
const AAResults &getAAResults() const { return *AAR; }
bool runOnFunction(Function &F) override;
void getAnalysisUsage(AnalysisUsage &AU) const override;
};
/// A wrapper pass for external alias analyses. This just squirrels away the
/// callback used to run any analyses and register their results.
struct ExternalAAWrapperPass : ImmutablePass {
using CallbackT = std::function<void(Pass &, Function &, AAResults &)>;
CallbackT CB;
static char ID;
ExternalAAWrapperPass();
explicit ExternalAAWrapperPass(CallbackT CB);
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesAll();
}
};
FunctionPass *createAAResultsWrapperPass();
/// A wrapper pass around a callback which can be used to populate the
/// AAResults in the AAResultsWrapperPass from an external AA.
///
/// The callback provided here will be used each time we prepare an AAResults
/// object, and will receive a reference to the function wrapper pass, the
/// function, and the AAResults object to populate. This should be used when
/// setting up a custom pass pipeline to inject a hook into the AA results.
ImmutablePass *createExternalAAWrapperPass(
std::function<void(Pass &, Function &, AAResults &)> Callback);
/// A helper for the legacy pass manager to create a \c AAResults
/// object populated to the best of our ability for a particular function when
/// inside of a \c ModulePass or a \c CallGraphSCCPass.
///
/// If a \c ModulePass or a \c CallGraphSCCPass calls \p
/// createLegacyPMAAResults, it also needs to call \p addUsedAAAnalyses in \p
/// getAnalysisUsage.
AAResults createLegacyPMAAResults(Pass &P, Function &F, BasicAAResult &BAR);
/// A helper for the legacy pass manager to populate \p AU to add uses to make
/// sure the analyses required by \p createLegacyPMAAResults are available.
void getAAResultsAnalysisUsage(AnalysisUsage &AU);
} // end namespace llvm
#endif // LLVM_ANALYSIS_ALIASANALYSIS_H
