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//===- llvm/ModuleSummaryIndex.h - Module Summary Index ---------*- C++ -*-===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
/// @file
/// ModuleSummaryIndex.h This file contains the declarations the classes that
/// hold the module index and summary for function importing.
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/TinyPtrVector.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/Allocator.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/ScaledNumber.h"
#include "llvm/Support/StringSaver.h"
#include <algorithm>
#include <array>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <map>
#include <memory>
#include <set>
#include <string>
#include <utility>
#include <vector>
namespace llvm {
namespace yaml {
template <typename T> struct MappingTraits;
} // end namespace yaml
/// Class to accumulate and hold information about a callee.
struct CalleeInfo {
enum class HotnessType : uint8_t {
Unknown = 0,
Cold = 1,
None = 2,
Hot = 3,
Critical = 4
// The size of the bit-field might need to be adjusted if more values are
// added to HotnessType enum.
uint32_t Hotness : 3;
/// The value stored in RelBlockFreq has to be interpreted as the digits of
/// a scaled number with a scale of \p -ScaleShift.
uint32_t RelBlockFreq : 29;
static constexpr int32_t ScaleShift = 8;
static constexpr uint64_t MaxRelBlockFreq = (1 << 29) - 1;
: Hotness(static_cast<uint32_t>(HotnessType::Unknown)), RelBlockFreq(0) {}
explicit CalleeInfo(HotnessType Hotness, uint64_t RelBF)
: Hotness(static_cast<uint32_t>(Hotness)), RelBlockFreq(RelBF) {}
void updateHotness(const HotnessType OtherHotness) {
Hotness = std::max(Hotness, static_cast<uint32_t>(OtherHotness));
HotnessType getHotness() const { return HotnessType(Hotness); }
/// Update \p RelBlockFreq from \p BlockFreq and \p EntryFreq
/// BlockFreq is divided by EntryFreq and added to RelBlockFreq. To represent
/// fractional values, the result is represented as a fixed point number with
/// scale of -ScaleShift.
void updateRelBlockFreq(uint64_t BlockFreq, uint64_t EntryFreq) {
if (EntryFreq == 0)
using Scaled64 = ScaledNumber<uint64_t>;
Scaled64 Temp(BlockFreq, ScaleShift);
Temp /= Scaled64::get(EntryFreq);
uint64_t Sum =
SaturatingAdd<uint64_t>(Temp.toInt<uint64_t>(), RelBlockFreq);
Sum = std::min(Sum, uint64_t(MaxRelBlockFreq));
RelBlockFreq = static_cast<uint32_t>(Sum);
inline const char *getHotnessName(CalleeInfo::HotnessType HT) {
switch (HT) {
case CalleeInfo::HotnessType::Unknown:
return "unknown";
case CalleeInfo::HotnessType::Cold:
return "cold";
case CalleeInfo::HotnessType::None:
return "none";
case CalleeInfo::HotnessType::Hot:
return "hot";
case CalleeInfo::HotnessType::Critical:
return "critical";
llvm_unreachable("invalid hotness");
class GlobalValueSummary;
using GlobalValueSummaryList = std::vector<std::unique_ptr<GlobalValueSummary>>;
struct GlobalValueSummaryInfo {
union NameOrGV {
NameOrGV(bool HaveGVs) {
if (HaveGVs)
GV = nullptr;
Name = "";
/// The GlobalValue corresponding to this summary. This is only used in
/// per-module summaries and when the IR is available. E.g. when module
/// analysis is being run, or when parsing both the IR and the summary
/// from assembly.
const GlobalValue *GV;
/// Summary string representation. This StringRef points to BC module
/// string table and is valid until module data is stored in memory.
/// This is guaranteed to happen until runThinLTOBackend function is
/// called, so it is safe to use this field during thin link. This field
/// is only valid if summary index was loaded from BC file.
StringRef Name;
} U;
GlobalValueSummaryInfo(bool HaveGVs) : U(HaveGVs) {}
/// List of global value summary structures for a particular value held
/// in the GlobalValueMap. Requires a vector in the case of multiple
/// COMDAT values of the same name.
GlobalValueSummaryList SummaryList;
/// Map from global value GUID to corresponding summary structures. Use a
/// std::map rather than a DenseMap so that pointers to the map's value_type
/// (which are used by ValueInfo) are not invalidated by insertion. Also it will
/// likely incur less overhead, as the value type is not very small and the size
/// of the map is unknown, resulting in inefficiencies due to repeated
/// insertions and resizing.
using GlobalValueSummaryMapTy =
std::map<GlobalValue::GUID, GlobalValueSummaryInfo>;
/// Struct that holds a reference to a particular GUID in a global value
/// summary.
struct ValueInfo {
PointerIntPair<const GlobalValueSummaryMapTy::value_type *, 2, int>
ValueInfo() = default;
ValueInfo(bool HaveGVs, const GlobalValueSummaryMapTy::value_type *R) {
operator bool() const { return getRef(); }
GlobalValue::GUID getGUID() const { return getRef()->first; }
const GlobalValue *getValue() const {
return getRef()->second.U.GV;
ArrayRef<std::unique_ptr<GlobalValueSummary>> getSummaryList() const {
return getRef()->second.SummaryList;
StringRef name() const {
return haveGVs() ? getRef()->second.U.GV->getName()
: getRef()->second.U.Name;
bool haveGVs() const { return RefAndFlags.getInt() & 0x1; }
bool isReadOnly() const { return RefAndFlags.getInt() & 0x2; }
void setReadOnly() { RefAndFlags.setInt(RefAndFlags.getInt() | 0x2); }
const GlobalValueSummaryMapTy::value_type *getRef() const {
return RefAndFlags.getPointer();
bool isDSOLocal() const;
inline raw_ostream &operator<<(raw_ostream &OS, const ValueInfo &VI) {
OS << VI.getGUID();
if (!
OS << " (" << << ")";
return OS;
inline bool operator==(const ValueInfo &A, const ValueInfo &B) {
assert(A.getRef() && B.getRef() &&
"Need ValueInfo with non-null Ref for comparison");
return A.getRef() == B.getRef();
inline bool operator!=(const ValueInfo &A, const ValueInfo &B) {
assert(A.getRef() && B.getRef() &&
"Need ValueInfo with non-null Ref for comparison");
return A.getRef() != B.getRef();
inline bool operator<(const ValueInfo &A, const ValueInfo &B) {
assert(A.getRef() && B.getRef() &&
"Need ValueInfo with non-null Ref to compare GUIDs");
return A.getGUID() < B.getGUID();
template <> struct DenseMapInfo<ValueInfo> {
static inline ValueInfo getEmptyKey() {
return ValueInfo(false, (GlobalValueSummaryMapTy::value_type *)-8);
static inline ValueInfo getTombstoneKey() {
return ValueInfo(false, (GlobalValueSummaryMapTy::value_type *)-16);
static inline bool isSpecialKey(ValueInfo V) {
return V == getTombstoneKey() || V == getEmptyKey();
static bool isEqual(ValueInfo L, ValueInfo R) {
// We are not supposed to mix ValueInfo(s) with different HaveGVs flag
// in a same container.
assert(isSpecialKey(L) || isSpecialKey(R) || (L.haveGVs() == R.haveGVs()));
return L.getRef() == R.getRef();
static unsigned getHashValue(ValueInfo I) { return (uintptr_t)I.getRef(); }
/// Function and variable summary information to aid decisions and
/// implementation of importing.
class GlobalValueSummary {
/// Sububclass discriminator (for dyn_cast<> et al.)
enum SummaryKind : unsigned { AliasKind, FunctionKind, GlobalVarKind };
/// Group flags (Linkage, NotEligibleToImport, etc.) as a bitfield.
struct GVFlags {
/// The linkage type of the associated global value.
/// One use is to flag values that have local linkage types and need to
/// have module identifier appended before placing into the combined
/// index, to disambiguate from other values with the same name.
/// In the future this will be used to update and optimize linkage
/// types based on global summary-based analysis.
unsigned Linkage : 4;
/// Indicate if the global value cannot be imported (e.g. it cannot
/// be renamed or references something that can't be renamed).
unsigned NotEligibleToImport : 1;
/// In per-module summary, indicate that the global value must be considered
/// a live root for index-based liveness analysis. Used for special LLVM
/// values such as llvm.global_ctors that the linker does not know about.
/// In combined summary, indicate that the global value is live.
unsigned Live : 1;
/// Indicates that the linker resolved the symbol to a definition from
/// within the same linkage unit.
unsigned DSOLocal : 1;
/// Convenience Constructors
explicit GVFlags(GlobalValue::LinkageTypes Linkage,
bool NotEligibleToImport, bool Live, bool IsLocal)
: Linkage(Linkage), NotEligibleToImport(NotEligibleToImport),
Live(Live), DSOLocal(IsLocal) {}
/// Kind of summary for use in dyn_cast<> et al.
SummaryKind Kind;
GVFlags Flags;
/// This is the hash of the name of the symbol in the original file. It is
/// identical to the GUID for global symbols, but differs for local since the
/// GUID includes the module level id in the hash.
GlobalValue::GUID OriginalName = 0;
/// Path of module IR containing value's definition, used to locate
/// module during importing.
/// This is only used during parsing of the combined index, or when
/// parsing the per-module index for creation of the combined summary index,
/// not during writing of the per-module index which doesn't contain a
/// module path string table.
StringRef ModulePath;
/// List of values referenced by this global value's definition
/// (either by the initializer of a global variable, or referenced
/// from within a function). This does not include functions called, which
/// are listed in the derived FunctionSummary object.
std::vector<ValueInfo> RefEdgeList;
GlobalValueSummary(SummaryKind K, GVFlags Flags, std::vector<ValueInfo> Refs)
: Kind(K), Flags(Flags), RefEdgeList(std::move(Refs)) {
assert((K != AliasKind || Refs.empty()) &&
"Expect no references for AliasSummary");
virtual ~GlobalValueSummary() = default;
/// Returns the hash of the original name, it is identical to the GUID for
/// externally visible symbols, but not for local ones.
GlobalValue::GUID getOriginalName() const { return OriginalName; }
/// Initialize the original name hash in this summary.
void setOriginalName(GlobalValue::GUID Name) { OriginalName = Name; }
/// Which kind of summary subclass this is.
SummaryKind getSummaryKind() const { return Kind; }
/// Set the path to the module containing this function, for use in
/// the combined index.
void setModulePath(StringRef ModPath) { ModulePath = ModPath; }
/// Get the path to the module containing this function.
StringRef modulePath() const { return ModulePath; }
/// Get the flags for this GlobalValue (see \p struct GVFlags).
GVFlags flags() const { return Flags; }
/// Return linkage type recorded for this global value.
GlobalValue::LinkageTypes linkage() const {
return static_cast<GlobalValue::LinkageTypes>(Flags.Linkage);
/// Sets the linkage to the value determined by global summary-based
/// optimization. Will be applied in the ThinLTO backends.
void setLinkage(GlobalValue::LinkageTypes Linkage) {
Flags.Linkage = Linkage;
/// Return true if this global value can't be imported.
bool notEligibleToImport() const { return Flags.NotEligibleToImport; }
bool isLive() const { return Flags.Live; }
void setLive(bool Live) { Flags.Live = Live; }
void setDSOLocal(bool Local) { Flags.DSOLocal = Local; }
bool isDSOLocal() const { return Flags.DSOLocal; }
/// Flag that this global value cannot be imported.
void setNotEligibleToImport() { Flags.NotEligibleToImport = true; }
/// Return the list of values referenced by this global value definition.
ArrayRef<ValueInfo> refs() const { return RefEdgeList; }
/// If this is an alias summary, returns the summary of the aliased object (a
/// global variable or function), otherwise returns itself.
GlobalValueSummary *getBaseObject();
const GlobalValueSummary *getBaseObject() const;
friend class ModuleSummaryIndex;
/// Alias summary information.
class AliasSummary : public GlobalValueSummary {
GlobalValueSummary *AliaseeSummary;
// AliaseeGUID is only set and accessed when we are building a combined index
// via the BitcodeReader.
GlobalValue::GUID AliaseeGUID;
AliasSummary(GVFlags Flags)
: GlobalValueSummary(AliasKind, Flags, ArrayRef<ValueInfo>{}),
AliaseeSummary(nullptr), AliaseeGUID(0) {}
/// Check if this is an alias summary.
static bool classof(const GlobalValueSummary *GVS) {
return GVS->getSummaryKind() == AliasKind;
void setAliasee(GlobalValueSummary *Aliasee) { AliaseeSummary = Aliasee; }
void setAliaseeGUID(GlobalValue::GUID GUID) { AliaseeGUID = GUID; }
bool hasAliasee() const { return !!AliaseeSummary; }
const GlobalValueSummary &getAliasee() const {
assert(AliaseeSummary && "Unexpected missing aliasee summary");
return *AliaseeSummary;
GlobalValueSummary &getAliasee() {
return const_cast<GlobalValueSummary &>(
static_cast<const AliasSummary *>(this)->getAliasee());
bool hasAliaseeGUID() const { return AliaseeGUID != 0; }
const GlobalValue::GUID &getAliaseeGUID() const {
assert(AliaseeGUID && "Unexpected missing aliasee GUID");
return AliaseeGUID;
const inline GlobalValueSummary *GlobalValueSummary::getBaseObject() const {
if (auto *AS = dyn_cast<AliasSummary>(this))
return &AS->getAliasee();
return this;
inline GlobalValueSummary *GlobalValueSummary::getBaseObject() {
if (auto *AS = dyn_cast<AliasSummary>(this))
return &AS->getAliasee();
return this;
/// Function summary information to aid decisions and implementation of
/// importing.
class FunctionSummary : public GlobalValueSummary {
/// <CalleeValueInfo, CalleeInfo> call edge pair.
using EdgeTy = std::pair<ValueInfo, CalleeInfo>;
/// Types for -force-summary-edges-cold debugging option.
enum ForceSummaryHotnessType : unsigned {
/// An "identifier" for a virtual function. This contains the type identifier
/// represented as a GUID and the offset from the address point to the virtual
/// function pointer, where "address point" is as defined in the Itanium ABI:
struct VFuncId {
GlobalValue::GUID GUID;
uint64_t Offset;
/// A specification for a virtual function call with all constant integer
/// arguments. This is used to perform virtual constant propagation on the
/// summary.
struct ConstVCall {
VFuncId VFunc;
std::vector<uint64_t> Args;
/// All type identifier related information. Because these fields are
/// relatively uncommon we only allocate space for them if necessary.
struct TypeIdInfo {
/// List of type identifiers used by this function in llvm.type.test
/// intrinsics referenced by something other than an llvm.assume intrinsic,
/// represented as GUIDs.
std::vector<GlobalValue::GUID> TypeTests;
/// List of virtual calls made by this function using (respectively)
/// llvm.assume(llvm.type.test) or llvm.type.checked.load intrinsics that do
/// not have all constant integer arguments.
std::vector<VFuncId> TypeTestAssumeVCalls, TypeCheckedLoadVCalls;
/// List of virtual calls made by this function using (respectively)
/// llvm.assume(llvm.type.test) or llvm.type.checked.load intrinsics with
/// all constant integer arguments.
std::vector<ConstVCall> TypeTestAssumeConstVCalls,
/// Flags specific to function summaries.
struct FFlags {
// Function attribute flags. Used to track if a function accesses memory,
// recurses or aliases.
unsigned ReadNone : 1;
unsigned ReadOnly : 1;
unsigned NoRecurse : 1;
unsigned ReturnDoesNotAlias : 1;
// Indicate if the global value cannot be inlined.
unsigned NoInline : 1;
/// Create an empty FunctionSummary (with specified call edges).
/// Used to represent external nodes and the dummy root node.
static FunctionSummary
makeDummyFunctionSummary(std::vector<FunctionSummary::EdgeTy> Edges) {
return FunctionSummary(
/*NotEligibleToImport=*/true, /*Live=*/true, /*IsLocal=*/false),
/*InsCount=*/0, FunctionSummary::FFlags{}, /*EntryCount=*/0,
std::vector<ValueInfo>(), std::move(Edges),
/// A dummy node to reference external functions that aren't in the index
static FunctionSummary ExternalNode;
/// Number of instructions (ignoring debug instructions, e.g.) computed
/// during the initial compile step when the summary index is first built.
unsigned InstCount;
/// Function summary specific flags.
FFlags FunFlags;
/// The synthesized entry count of the function.
/// This is only populated during ThinLink phase and remains unused while
/// generating per-module summaries.
uint64_t EntryCount = 0;
/// List of <CalleeValueInfo, CalleeInfo> call edge pairs from this function.
std::vector<EdgeTy> CallGraphEdgeList;
std::unique_ptr<TypeIdInfo> TIdInfo;
FunctionSummary(GVFlags Flags, unsigned NumInsts, FFlags FunFlags,
uint64_t EntryCount, std::vector<ValueInfo> Refs,
std::vector<EdgeTy> CGEdges,
std::vector<GlobalValue::GUID> TypeTests,
std::vector<VFuncId> TypeTestAssumeVCalls,
std::vector<VFuncId> TypeCheckedLoadVCalls,
std::vector<ConstVCall> TypeTestAssumeConstVCalls,
std::vector<ConstVCall> TypeCheckedLoadConstVCalls)
: GlobalValueSummary(FunctionKind, Flags, std::move(Refs)),
InstCount(NumInsts), FunFlags(FunFlags), EntryCount(EntryCount),
CallGraphEdgeList(std::move(CGEdges)) {
if (!TypeTests.empty() || !TypeTestAssumeVCalls.empty() ||
!TypeCheckedLoadVCalls.empty() || !TypeTestAssumeConstVCalls.empty() ||
TIdInfo = llvm::make_unique<TypeIdInfo>(TypeIdInfo{
std::move(TypeTests), std::move(TypeTestAssumeVCalls),
// Gets the number of immutable refs in RefEdgeList
unsigned immutableRefCount() const;
/// Check if this is a function summary.
static bool classof(const GlobalValueSummary *GVS) {
return GVS->getSummaryKind() == FunctionKind;
/// Get function summary flags.
FFlags fflags() const { return FunFlags; }
/// Get the instruction count recorded for this function.
unsigned instCount() const { return InstCount; }
/// Get the synthetic entry count for this function.
uint64_t entryCount() const { return EntryCount; }
/// Set the synthetic entry count for this function.
void setEntryCount(uint64_t EC) { EntryCount = EC; }
/// Return the list of <CalleeValueInfo, CalleeInfo> pairs.
ArrayRef<EdgeTy> calls() const { return CallGraphEdgeList; }
/// Returns the list of type identifiers used by this function in
/// llvm.type.test intrinsics other than by an llvm.assume intrinsic,
/// represented as GUIDs.
ArrayRef<GlobalValue::GUID> type_tests() const {
if (TIdInfo)
return TIdInfo->TypeTests;
return {};
/// Returns the list of virtual calls made by this function using
/// llvm.assume(llvm.type.test) intrinsics that do not have all constant
/// integer arguments.
ArrayRef<VFuncId> type_test_assume_vcalls() const {
if (TIdInfo)
return TIdInfo->TypeTestAssumeVCalls;
return {};
/// Returns the list of virtual calls made by this function using
/// llvm.type.checked.load intrinsics that do not have all constant integer
/// arguments.
ArrayRef<VFuncId> type_checked_load_vcalls() const {
if (TIdInfo)
return TIdInfo->TypeCheckedLoadVCalls;
return {};
/// Returns the list of virtual calls made by this function using
/// llvm.assume(llvm.type.test) intrinsics with all constant integer
/// arguments.
ArrayRef<ConstVCall> type_test_assume_const_vcalls() const {
if (TIdInfo)
return TIdInfo->TypeTestAssumeConstVCalls;
return {};
/// Returns the list of virtual calls made by this function using
/// llvm.type.checked.load intrinsics with all constant integer arguments.
ArrayRef<ConstVCall> type_checked_load_const_vcalls() const {
if (TIdInfo)
return TIdInfo->TypeCheckedLoadConstVCalls;
return {};
/// Add a type test to the summary. This is used by WholeProgramDevirt if we
/// were unable to devirtualize a checked call.
void addTypeTest(GlobalValue::GUID Guid) {
if (!TIdInfo)
TIdInfo = llvm::make_unique<TypeIdInfo>();
const TypeIdInfo *getTypeIdInfo() const { return TIdInfo.get(); };
friend struct GraphTraits<ValueInfo>;
template <> struct DenseMapInfo<FunctionSummary::VFuncId> {
static FunctionSummary::VFuncId getEmptyKey() { return {0, uint64_t(-1)}; }
static FunctionSummary::VFuncId getTombstoneKey() {
return {0, uint64_t(-2)};
static bool isEqual(FunctionSummary::VFuncId L, FunctionSummary::VFuncId R) {
return L.GUID == R.GUID && L.Offset == R.Offset;
static unsigned getHashValue(FunctionSummary::VFuncId I) { return I.GUID; }
template <> struct DenseMapInfo<FunctionSummary::ConstVCall> {
static FunctionSummary::ConstVCall getEmptyKey() {
return {{0, uint64_t(-1)}, {}};
static FunctionSummary::ConstVCall getTombstoneKey() {
return {{0, uint64_t(-2)}, {}};
static bool isEqual(FunctionSummary::ConstVCall L,
FunctionSummary::ConstVCall R) {
return DenseMapInfo<FunctionSummary::VFuncId>::isEqual(L.VFunc, R.VFunc) &&
L.Args == R.Args;
static unsigned getHashValue(FunctionSummary::ConstVCall I) {
return I.VFunc.GUID;
/// Global variable summary information to aid decisions and
/// implementation of importing.
/// Global variable summary has extra flag, telling if it is
/// modified during the program run or not. This affects ThinLTO
/// internalization
class GlobalVarSummary : public GlobalValueSummary {
struct GVarFlags {
GVarFlags(bool ReadOnly = false) : ReadOnly(ReadOnly) {}
unsigned ReadOnly : 1;
} VarFlags;
GlobalVarSummary(GVFlags Flags, GVarFlags VarFlags,
std::vector<ValueInfo> Refs)
: GlobalValueSummary(GlobalVarKind, Flags, std::move(Refs)),
VarFlags(VarFlags) {}
/// Check if this is a global variable summary.
static bool classof(const GlobalValueSummary *GVS) {
return GVS->getSummaryKind() == GlobalVarKind;
GVarFlags varflags() const { return VarFlags; }
void setReadOnly(bool RO) { VarFlags.ReadOnly = RO; }
bool isReadOnly() const { return VarFlags.ReadOnly; }
struct TypeTestResolution {
/// Specifies which kind of type check we should emit for this byte array.
/// See for full
/// details on each kind of check; the enumerators are described with
/// reference to that document.
enum Kind {
Unsat, ///< Unsatisfiable type (i.e. no global has this type metadata)
ByteArray, ///< Test a byte array (first example)
Inline, ///< Inlined bit vector ("Short Inline Bit Vectors")
Single, ///< Single element (last example in "Short Inline Bit Vectors")
AllOnes, ///< All-ones bit vector ("Eliminating Bit Vector Checks for
/// All-Ones Bit Vectors")
} TheKind = Unsat;
/// Range of size-1 expressed as a bit width. For example, if the size is in
/// range [1,256], this number will be 8. This helps generate the most compact
/// instruction sequences.
unsigned SizeM1BitWidth = 0;
// The following fields are only used if the target does not support the use
// of absolute symbols to store constants. Their meanings are the same as the
// corresponding fields in LowerTypeTestsModule::TypeIdLowering in
// LowerTypeTests.cpp.
uint64_t AlignLog2 = 0;
uint64_t SizeM1 = 0;
uint8_t BitMask = 0;
uint64_t InlineBits = 0;
struct WholeProgramDevirtResolution {
enum Kind {
Indir, ///< Just do a regular virtual call
SingleImpl, ///< Single implementation devirtualization
BranchFunnel, ///< When retpoline mitigation is enabled, use a branch funnel
///< that is defined in the merged module. Otherwise same as
///< Indir.
} TheKind = Indir;
std::string SingleImplName;
struct ByArg {
enum Kind {
Indir, ///< Just do a regular virtual call
UniformRetVal, ///< Uniform return value optimization
UniqueRetVal, ///< Unique return value optimization
VirtualConstProp, ///< Virtual constant propagation
} TheKind = Indir;
/// Additional information for the resolution:
/// - UniformRetVal: the uniform return value.
/// - UniqueRetVal: the return value associated with the unique vtable (0 or
/// 1).
uint64_t Info = 0;
// The following fields are only used if the target does not support the use
// of absolute symbols to store constants.
uint32_t Byte = 0;
uint32_t Bit = 0;
/// Resolutions for calls with all constant integer arguments (excluding the
/// first argument, "this"), where the key is the argument vector.
std::map<std::vector<uint64_t>, ByArg> ResByArg;
struct TypeIdSummary {
TypeTestResolution TTRes;
/// Mapping from byte offset to whole-program devirt resolution for that
/// (typeid, byte offset) pair.
std::map<uint64_t, WholeProgramDevirtResolution> WPDRes;
/// 160 bits SHA1
using ModuleHash = std::array<uint32_t, 5>;
/// Type used for iterating through the global value summary map.
using const_gvsummary_iterator = GlobalValueSummaryMapTy::const_iterator;
using gvsummary_iterator = GlobalValueSummaryMapTy::iterator;
/// String table to hold/own module path strings, which additionally holds the
/// module ID assigned to each module during the plugin step, as well as a hash
/// of the module. The StringMap makes a copy of and owns inserted strings.
using ModulePathStringTableTy = StringMap<std::pair<uint64_t, ModuleHash>>;
/// Map of global value GUID to its summary, used to identify values defined in
/// a particular module, and provide efficient access to their summary.
using GVSummaryMapTy = DenseMap<GlobalValue::GUID, GlobalValueSummary *>;
/// Map of a type GUID to type id string and summary (multimap used
/// in case of GUID conflicts).
using TypeIdSummaryMapTy =
std::multimap<GlobalValue::GUID, std::pair<std::string, TypeIdSummary>>;
/// Class to hold module path string table and global value map,
/// and encapsulate methods for operating on them.
class ModuleSummaryIndex {
/// Map from value name to list of summary instances for values of that
/// name (may be duplicates in the COMDAT case, e.g.).
GlobalValueSummaryMapTy GlobalValueMap;
/// Holds strings for combined index, mapping to the corresponding module ID.
ModulePathStringTableTy ModulePathStringTable;
/// Mapping from type identifier GUIDs to type identifier and its summary
/// information.
TypeIdSummaryMapTy TypeIdMap;
/// Mapping from original ID to GUID. If original ID can map to multiple
/// GUIDs, it will be mapped to 0.
std::map<GlobalValue::GUID, GlobalValue::GUID> OidGuidMap;
/// Indicates that summary-based GlobalValue GC has run, and values with
/// GVFlags::Live==false are really dead. Otherwise, all values must be
/// considered live.
bool WithGlobalValueDeadStripping = false;
/// Indicates that summary-based synthetic entry count propagation has run
bool HasSyntheticEntryCounts = false;
/// Indicates that distributed backend should skip compilation of the
/// module. Flag is suppose to be set by distributed ThinLTO indexing
/// when it detected that the module is not needed during the final
/// linking. As result distributed backend should just output a minimal
/// valid object file.
bool SkipModuleByDistributedBackend = false;
/// If true then we're performing analysis of IR module, or parsing along with
/// the IR from assembly. The value of 'false' means we're reading summary
/// from BC or YAML source. Affects the type of value stored in NameOrGV
/// union.
bool HaveGVs;
// True if the index was created for a module compiled with -fsplit-lto-unit.
bool EnableSplitLTOUnit;
// True if some of the modules were compiled with -fsplit-lto-unit and
// some were not. Set when the combined index is created during the thin link.
bool PartiallySplitLTOUnits = false;
std::set<std::string> CfiFunctionDefs;
std::set<std::string> CfiFunctionDecls;
// Used in cases where we want to record the name of a global, but
// don't have the string owned elsewhere (e.g. the Strtab on a module).
StringSaver Saver;
BumpPtrAllocator Alloc;
// YAML I/O support.
friend yaml::MappingTraits<ModuleSummaryIndex>;
GlobalValueSummaryMapTy::value_type *
getOrInsertValuePtr(GlobalValue::GUID GUID) {
return &*GlobalValueMap.emplace(GUID, GlobalValueSummaryInfo(HaveGVs))
// See HaveGVs variable comment.
ModuleSummaryIndex(bool HaveGVs, bool EnableSplitLTOUnit = false)
: HaveGVs(HaveGVs), EnableSplitLTOUnit(EnableSplitLTOUnit), Saver(Alloc) {
bool haveGVs() const { return HaveGVs; }
gvsummary_iterator begin() { return GlobalValueMap.begin(); }
const_gvsummary_iterator begin() const { return GlobalValueMap.begin(); }
gvsummary_iterator end() { return GlobalValueMap.end(); }
const_gvsummary_iterator end() const { return GlobalValueMap.end(); }
size_t size() const { return GlobalValueMap.size(); }
/// Convenience function for doing a DFS on a ValueInfo. Marks the function in
/// the FunctionHasParent map.
static void discoverNodes(ValueInfo V,
std::map<ValueInfo, bool> &FunctionHasParent) {
if (!V.getSummaryList().size())
return; // skip external functions that don't have summaries
// Mark discovered if we haven't yet
auto S = FunctionHasParent.emplace(V, false);
// Stop if we've already discovered this node
if (!S.second)
FunctionSummary *F =
assert(F != nullptr && "Expected FunctionSummary node");
for (auto &C : F->calls()) {
// Insert node if necessary
auto S = FunctionHasParent.emplace(C.first, true);
// Skip nodes that we're sure have parents
if (!S.second && S.first->second)
if (S.second)
discoverNodes(C.first, FunctionHasParent);
S.first->second = true;
// Calculate the callgraph root
FunctionSummary calculateCallGraphRoot() {
// Functions that have a parent will be marked in FunctionHasParent pair.
// Once we've marked all functions, the functions in the map that are false
// have no parent (so they're the roots)
std::map<ValueInfo, bool> FunctionHasParent;
for (auto &S : *this) {
// Skip external functions
if (!S.second.SummaryList.size() ||
discoverNodes(ValueInfo(HaveGVs, &S), FunctionHasParent);
std::vector<FunctionSummary::EdgeTy> Edges;
// create edges to all roots in the Index
for (auto &P : FunctionHasParent) {
if (P.second)
continue; // skip over non-root nodes
Edges.push_back(std::make_pair(P.first, CalleeInfo{}));
if (Edges.empty()) {
// Failed to find root - return an empty node
return FunctionSummary::makeDummyFunctionSummary({});
auto CallGraphRoot = FunctionSummary::makeDummyFunctionSummary(Edges);
return CallGraphRoot;
bool withGlobalValueDeadStripping() const {
return WithGlobalValueDeadStripping;
void setWithGlobalValueDeadStripping() {
WithGlobalValueDeadStripping = true;
bool hasSyntheticEntryCounts() const { return HasSyntheticEntryCounts; }
void setHasSyntheticEntryCounts() { HasSyntheticEntryCounts = true; }
bool skipModuleByDistributedBackend() const {
return SkipModuleByDistributedBackend;
void setSkipModuleByDistributedBackend() {
SkipModuleByDistributedBackend = true;
bool enableSplitLTOUnit() const { return EnableSplitLTOUnit; }
void setEnableSplitLTOUnit() { EnableSplitLTOUnit = true; }
bool partiallySplitLTOUnits() const { return PartiallySplitLTOUnits; }
void setPartiallySplitLTOUnits() { PartiallySplitLTOUnits = true; }
bool isGlobalValueLive(const GlobalValueSummary *GVS) const {
return !WithGlobalValueDeadStripping || GVS->isLive();
bool isGUIDLive(GlobalValue::GUID GUID) const;
/// Return a ValueInfo for the index value_type (convenient when iterating
/// index).
ValueInfo getValueInfo(const GlobalValueSummaryMapTy::value_type &R) const {
return ValueInfo(HaveGVs, &R);
/// Return a ValueInfo for GUID if it exists, otherwise return ValueInfo().
ValueInfo getValueInfo(GlobalValue::GUID GUID) const {
auto I = GlobalValueMap.find(GUID);
return ValueInfo(HaveGVs, I == GlobalValueMap.end() ? nullptr : &*I);
/// Return a ValueInfo for \p GUID.
ValueInfo getOrInsertValueInfo(GlobalValue::GUID GUID) {
return ValueInfo(HaveGVs, getOrInsertValuePtr(GUID));
// Save a string in the Index. Use before passing Name to
// getOrInsertValueInfo when the string isn't owned elsewhere (e.g. on the
// module's Strtab).
StringRef saveString(StringRef String) { return; }
/// Return a ValueInfo for \p GUID setting value \p Name.
ValueInfo getOrInsertValueInfo(GlobalValue::GUID GUID, StringRef Name) {
auto VP = getOrInsertValuePtr(GUID);
VP->second.U.Name = Name;
return ValueInfo(HaveGVs, VP);
/// Return a ValueInfo for \p GV and mark it as belonging to GV.
ValueInfo getOrInsertValueInfo(const GlobalValue *GV) {
auto VP = getOrInsertValuePtr(GV->getGUID());
VP->second.U.GV = GV;
return ValueInfo(HaveGVs, VP);
/// Return the GUID for \p OriginalId in the OidGuidMap.
GlobalValue::GUID getGUIDFromOriginalID(GlobalValue::GUID OriginalID) const {
const auto I = OidGuidMap.find(OriginalID);
return I == OidGuidMap.end() ? 0 : I->second;
std::set<std::string> &cfiFunctionDefs() { return CfiFunctionDefs; }
const std::set<std::string> &cfiFunctionDefs() const { return CfiFunctionDefs; }
std::set<std::string> &cfiFunctionDecls() { return CfiFunctionDecls; }
const std::set<std::string> &cfiFunctionDecls() const { return CfiFunctionDecls; }
/// Add a global value summary for a value.
void addGlobalValueSummary(const GlobalValue &GV,
std::unique_ptr<GlobalValueSummary> Summary) {
addGlobalValueSummary(getOrInsertValueInfo(&GV), std::move(Summary));
/// Add a global value summary for a value of the given name.
void addGlobalValueSummary(StringRef ValueName,
std::unique_ptr<GlobalValueSummary> Summary) {
/// Add a global value summary for the given ValueInfo.
void addGlobalValueSummary(ValueInfo VI,
std::unique_ptr<GlobalValueSummary> Summary) {
addOriginalName(VI.getGUID(), Summary->getOriginalName());
// Here we have a notionally const VI, but the value it points to is owned
// by the non-const *this.
const_cast<GlobalValueSummaryMapTy::value_type *>(VI.getRef())
/// Add an original name for the value of the given GUID.
void addOriginalName(GlobalValue::GUID ValueGUID,
GlobalValue::GUID OrigGUID) {
if (OrigGUID == 0 || ValueGUID == OrigGUID)
if (OidGuidMap.count(OrigGUID) && OidGuidMap[OrigGUID] != ValueGUID)
OidGuidMap[OrigGUID] = 0;
OidGuidMap[OrigGUID] = ValueGUID;
/// Find the summary for global \p GUID in module \p ModuleId, or nullptr if
/// not found.
GlobalValueSummary *findSummaryInModule(GlobalValue::GUID ValueGUID,
StringRef ModuleId) const {
auto CalleeInfo = getValueInfo(ValueGUID);
if (!CalleeInfo) {
return nullptr; // This function does not have a summary
auto Summary =
[&](const std::unique_ptr<GlobalValueSummary> &Summary) {
return Summary->modulePath() == ModuleId;
if (Summary == CalleeInfo.getSummaryList().end())
return nullptr;
return Summary->get();
/// Returns the first GlobalValueSummary for \p GV, asserting that there
/// is only one if \p PerModuleIndex.
GlobalValueSummary *getGlobalValueSummary(const GlobalValue &GV,
bool PerModuleIndex = true) const {
assert(GV.hasName() && "Can't get GlobalValueSummary for GV with no name");
return getGlobalValueSummary(GV.getGUID(), PerModuleIndex);
/// Returns the first GlobalValueSummary for \p ValueGUID, asserting that
/// there
/// is only one if \p PerModuleIndex.
GlobalValueSummary *getGlobalValueSummary(GlobalValue::GUID ValueGUID,
bool PerModuleIndex = true) const;
/// Table of modules, containing module hash and id.
const StringMap<std::pair<uint64_t, ModuleHash>> &modulePaths() const {
return ModulePathStringTable;
/// Table of modules, containing hash and id.
StringMap<std::pair<uint64_t, ModuleHash>> &modulePaths() {
return ModulePathStringTable;
/// Get the module ID recorded for the given module path.
uint64_t getModuleId(const StringRef ModPath) const {
return ModulePathStringTable.lookup(ModPath).first;
/// Get the module SHA1 hash recorded for the given module path.
const ModuleHash &getModuleHash(const StringRef ModPath) const {
auto It = ModulePathStringTable.find(ModPath);
assert(It != ModulePathStringTable.end() && "Module not registered");
return It->second.second;
/// Convenience method for creating a promoted global name
/// for the given value name of a local, and its original module's ID.
static std::string getGlobalNameForLocal(StringRef Name, ModuleHash ModHash) {
SmallString<256> NewName(Name);
NewName += ".llvm.";
NewName += utostr((uint64_t(ModHash[0]) << 32) |
ModHash[1]); // Take the first 64 bits
return NewName.str();
/// Helper to obtain the unpromoted name for a global value (or the original
/// name if not promoted).
static StringRef getOriginalNameBeforePromote(StringRef Name) {
std::pair<StringRef, StringRef> Pair = Name.split(".llvm.");
return Pair.first;
typedef ModulePathStringTableTy::value_type ModuleInfo;
/// Add a new module with the given \p Hash, mapped to the given \p
/// ModID, and return a reference to the module.
ModuleInfo *addModule(StringRef ModPath, uint64_t ModId,
ModuleHash Hash = ModuleHash{{0}}) {
return &*ModulePathStringTable.insert({ModPath, {ModId, Hash}}).first;
/// Return module entry for module with the given \p ModPath.
ModuleInfo *getModule(StringRef ModPath) {
auto It = ModulePathStringTable.find(ModPath);
assert(It != ModulePathStringTable.end() && "Module not registered");
return &*It;
/// Check if the given Module has any functions available for exporting
/// in the index. We consider any module present in the ModulePathStringTable
/// to have exported functions.
bool hasExportedFunctions(const Module &M) const {
return ModulePathStringTable.count(M.getModuleIdentifier());
const TypeIdSummaryMapTy &typeIds() const { return TypeIdMap; }
/// Return an existing or new TypeIdSummary entry for \p TypeId.
/// This accessor can mutate the map and therefore should not be used in
/// the ThinLTO backends.
TypeIdSummary &getOrInsertTypeIdSummary(StringRef TypeId) {
auto TidIter = TypeIdMap.equal_range(GlobalValue::getGUID(TypeId));
for (auto It = TidIter.first; It != TidIter.second; ++It)
if (It->second.first == TypeId)
return It->second.second;
auto It = TypeIdMap.insert(
{GlobalValue::getGUID(TypeId), {TypeId, TypeIdSummary()}});
return It->second.second;
/// This returns either a pointer to the type id summary (if present in the
/// summary map) or null (if not present). This may be used when importing.
const TypeIdSummary *getTypeIdSummary(StringRef TypeId) const {
auto TidIter = TypeIdMap.equal_range(GlobalValue::getGUID(TypeId));
for (auto It = TidIter.first; It != TidIter.second; ++It)
if (It->second.first == TypeId)
return &It->second.second;
return nullptr;
/// Collect for the given module the list of functions it defines
/// (GUID -> Summary).
void collectDefinedFunctionsForModule(StringRef ModulePath,
GVSummaryMapTy &GVSummaryMap) const;
/// Collect for each module the list of Summaries it defines (GUID ->
/// Summary).
void collectDefinedGVSummariesPerModule(
StringMap<GVSummaryMapTy> &ModuleToDefinedGVSummaries) const;
/// Print to an output stream.
void print(raw_ostream &OS, bool IsForDebug = false) const;
/// Dump to stderr (for debugging).
void dump() const;
/// Export summary to dot file for GraphViz.
void exportToDot(raw_ostream& OS) const;
/// Print out strongly connected components for debugging.
void dumpSCCs(raw_ostream &OS);
/// Analyze index and detect unmodified globals
void propagateConstants(const DenseSet<GlobalValue::GUID> &PreservedSymbols);
/// GraphTraits definition to build SCC for the index
template <> struct GraphTraits<ValueInfo> {
typedef ValueInfo NodeRef;
using EdgeRef = FunctionSummary::EdgeTy &;
static NodeRef valueInfoFromEdge(FunctionSummary::EdgeTy &P) {
return P.first;
using ChildIteratorType =
using ChildEdgeIteratorType = std::vector<FunctionSummary::EdgeTy>::iterator;
static NodeRef getEntryNode(ValueInfo V) { return V; }
static ChildIteratorType child_begin(NodeRef N) {
if (!N.getSummaryList().size()) // handle external function
return ChildIteratorType(
FunctionSummary *F =
return ChildIteratorType(F->CallGraphEdgeList.begin(), &valueInfoFromEdge);
static ChildIteratorType child_end(NodeRef N) {
if (!N.getSummaryList().size()) // handle external function
return ChildIteratorType(
FunctionSummary *F =
return ChildIteratorType(F->CallGraphEdgeList.end(), &valueInfoFromEdge);
static ChildEdgeIteratorType child_edge_begin(NodeRef N) {
if (!N.getSummaryList().size()) // handle external function
return FunctionSummary::ExternalNode.CallGraphEdgeList.begin();
FunctionSummary *F =
return F->CallGraphEdgeList.begin();
static ChildEdgeIteratorType child_edge_end(NodeRef N) {
if (!N.getSummaryList().size()) // handle external function
return FunctionSummary::ExternalNode.CallGraphEdgeList.end();
FunctionSummary *F =
return F->CallGraphEdgeList.end();
static NodeRef edge_dest(EdgeRef E) { return E.first; }
template <>
struct GraphTraits<ModuleSummaryIndex *> : public GraphTraits<ValueInfo> {
static NodeRef getEntryNode(ModuleSummaryIndex *I) {
std::unique_ptr<GlobalValueSummary> Root =
GlobalValueSummaryInfo G(I->haveGVs());
static auto P =
GlobalValueSummaryMapTy::value_type(GlobalValue::GUID(0), std::move(G));
return ValueInfo(I->haveGVs(), &P);
static inline bool canImportGlobalVar(GlobalValueSummary *S) {
// We don't import GV with references, because it can result
// in promotion of local variables in the source module.
return !GlobalValue::isInterposableLinkage(S->linkage()) &&
!S->notEligibleToImport() && S->refs().empty();
} // end namespace llvm