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//===-- InstrProfiling.cpp - Frontend instrumentation based profiling -----===//
// 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
// This pass lowers instrprof_* intrinsics emitted by a frontend for profiling.
// It also builds the data structures and initialization code needed for
// updating execution counts and emitting the profile at runtime.
#include "llvm/Transforms/Instrumentation/InstrProfiling.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Constant.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Dominators.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/Instruction.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Transforms/Utils/ModuleUtils.h"
#include "llvm/Transforms/Utils/SSAUpdater.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <string>
using namespace llvm;
#define DEBUG_TYPE "instrprof"
namespace {
cl::opt<bool> DoHashBasedCounterSplit(
cl::desc("Rename counter variable of a comdat function based on cfg hash"),
cl::opt<bool> RuntimeCounterRelocation(
cl::desc("Enable relocating counters at runtime."),
cl::opt<bool> ValueProfileStaticAlloc(
cl::desc("Do static counter allocation for value profiler"),
cl::opt<double> NumCountersPerValueSite(
cl::desc("The average number of profile counters allocated "
"per value profiling site."),
// This is set to a very small value because in real programs, only
// a very small percentage of value sites have non-zero targets, e.g, 1/30.
// For those sites with non-zero profile, the average number of targets
// is usually smaller than 2.
cl::opt<bool> AtomicCounterUpdateAll(
"instrprof-atomic-counter-update-all", cl::ZeroOrMore,
cl::desc("Make all profile counter updates atomic (for testing only)"),
cl::opt<bool> AtomicCounterUpdatePromoted(
"atomic-counter-update-promoted", cl::ZeroOrMore,
cl::desc("Do counter update using atomic fetch add "
" for promoted counters only"),
cl::opt<bool> AtomicFirstCounter(
"atomic-first-counter", cl::ZeroOrMore,
cl::desc("Use atomic fetch add for first counter in a function (usually "
"the entry counter)"),
// If the option is not specified, the default behavior about whether
// counter promotion is done depends on how instrumentaiton lowering
// pipeline is setup, i.e., the default value of true of this option
// does not mean the promotion will be done by default. Explicitly
// setting this option can override the default behavior.
cl::opt<bool> DoCounterPromotion("do-counter-promotion", cl::ZeroOrMore,
cl::desc("Do counter register promotion"),
cl::opt<unsigned> MaxNumOfPromotionsPerLoop(
cl::ZeroOrMore, "max-counter-promotions-per-loop", cl::init(20),
cl::desc("Max number counter promotions per loop to avoid"
" increasing register pressure too much"));
// A debug option
MaxNumOfPromotions(cl::ZeroOrMore, "max-counter-promotions", cl::init(-1),
cl::desc("Max number of allowed counter promotions"));
cl::opt<unsigned> SpeculativeCounterPromotionMaxExiting(
cl::ZeroOrMore, "speculative-counter-promotion-max-exiting", cl::init(3),
cl::desc("The max number of exiting blocks of a loop to allow "
" speculative counter promotion"));
cl::opt<bool> SpeculativeCounterPromotionToLoop(
cl::ZeroOrMore, "speculative-counter-promotion-to-loop", cl::init(false),
cl::desc("When the option is false, if the target block is in a loop, "
"the promotion will be disallowed unless the promoted counter "
" update can be further/iteratively promoted into an acyclic "
" region."));
cl::opt<bool> IterativeCounterPromotion(
cl::ZeroOrMore, "iterative-counter-promotion", cl::init(true),
cl::desc("Allow counter promotion across the whole loop nest."));
cl::opt<bool> SkipRetExitBlock(
cl::ZeroOrMore, "skip-ret-exit-block", cl::init(true),
cl::desc("Suppress counter promotion if exit blocks contain ret."));
class InstrProfilingLegacyPass : public ModulePass {
InstrProfiling InstrProf;
static char ID;
InstrProfilingLegacyPass() : ModulePass(ID) {}
InstrProfilingLegacyPass(const InstrProfOptions &Options, bool IsCS = false)
: ModulePass(ID), InstrProf(Options, IsCS) {
StringRef getPassName() const override {
return "Frontend instrumentation-based coverage lowering";
bool runOnModule(Module &M) override {
auto GetTLI = [this](Function &F) -> TargetLibraryInfo & {
return this->getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
return, GetTLI);
void getAnalysisUsage(AnalysisUsage &AU) const override {
/// A helper class to promote one counter RMW operation in the loop
/// into register update.
/// RWM update for the counter will be sinked out of the loop after
/// the transformation.
class PGOCounterPromoterHelper : public LoadAndStorePromoter {
Instruction *L, Instruction *S, SSAUpdater &SSA, Value *Init,
BasicBlock *PH, ArrayRef<BasicBlock *> ExitBlocks,
ArrayRef<Instruction *> InsertPts,
DenseMap<Loop *, SmallVector<LoadStorePair, 8>> &LoopToCands,
LoopInfo &LI)
: LoadAndStorePromoter({L, S}, SSA), Store(S), ExitBlocks(ExitBlocks),
InsertPts(InsertPts), LoopToCandidates(LoopToCands), LI(LI) {
SSA.AddAvailableValue(PH, Init);
void doExtraRewritesBeforeFinalDeletion() override {
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
BasicBlock *ExitBlock = ExitBlocks[i];
Instruction *InsertPos = InsertPts[i];
// Get LiveIn value into the ExitBlock. If there are multiple
// predecessors, the value is defined by a PHI node in this
// block.
Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock);
Value *Addr = cast<StoreInst>(Store)->getPointerOperand();
Type *Ty = LiveInValue->getType();
IRBuilder<> Builder(InsertPos);
if (AtomicCounterUpdatePromoted)
// automic update currently can only be promoted across the current
// loop, not the whole loop nest.
Builder.CreateAtomicRMW(AtomicRMWInst::Add, Addr, LiveInValue,
else {
LoadInst *OldVal = Builder.CreateLoad(Ty, Addr, "pgocount.promoted");
auto *NewVal = Builder.CreateAdd(OldVal, LiveInValue);
auto *NewStore = Builder.CreateStore(NewVal, Addr);
// Now update the parent loop's candidate list:
if (IterativeCounterPromotion) {
auto *TargetLoop = LI.getLoopFor(ExitBlock);
if (TargetLoop)
LoopToCandidates[TargetLoop].emplace_back(OldVal, NewStore);
Instruction *Store;
ArrayRef<BasicBlock *> ExitBlocks;
ArrayRef<Instruction *> InsertPts;
DenseMap<Loop *, SmallVector<LoadStorePair, 8>> &LoopToCandidates;
LoopInfo &LI;
/// A helper class to do register promotion for all profile counter
/// updates in a loop.
class PGOCounterPromoter {
DenseMap<Loop *, SmallVector<LoadStorePair, 8>> &LoopToCands,
Loop &CurLoop, LoopInfo &LI, BlockFrequencyInfo *BFI)
: LoopToCandidates(LoopToCands), ExitBlocks(), InsertPts(), L(CurLoop),
// Skip collection of ExitBlocks and InsertPts for loops that will not be
// able to have counters promoted.
SmallVector<BasicBlock *, 8> LoopExitBlocks;
SmallPtrSet<BasicBlock *, 8> BlockSet;
if (!isPromotionPossible(&L, LoopExitBlocks))
for (BasicBlock *ExitBlock : LoopExitBlocks) {
if (BlockSet.insert(ExitBlock).second) {
bool run(int64_t *NumPromoted) {
// Skip 'infinite' loops:
if (ExitBlocks.size() == 0)
return false;
// Skip if any of the ExitBlocks contains a ret instruction.
// This is to prevent dumping of incomplete profile -- if the
// the loop is a long running loop and dump is called in the middle
// of the loop, the result profile is incomplete.
// FIXME: add other heuristics to detect long running loops.
if (SkipRetExitBlock) {
for (auto BB : ExitBlocks)
if (isa<ReturnInst>(BB->getTerminator()))
return false;
unsigned MaxProm = getMaxNumOfPromotionsInLoop(&L);
if (MaxProm == 0)
return false;
unsigned Promoted = 0;
for (auto &Cand : LoopToCandidates[&L]) {
SmallVector<PHINode *, 4> NewPHIs;
SSAUpdater SSA(&NewPHIs);
Value *InitVal = ConstantInt::get(Cand.first->getType(), 0);
// If BFI is set, we will use it to guide the promotions.
if (BFI) {
auto *BB = Cand.first->getParent();
auto InstrCount = BFI->getBlockProfileCount(BB);
if (!InstrCount)
auto PreheaderCount = BFI->getBlockProfileCount(L.getLoopPreheader());
// If the average loop trip count is not greater than 1.5, we skip
// promotion.
if (PreheaderCount &&
(PreheaderCount.getValue() * 3) >= (InstrCount.getValue() * 2))
PGOCounterPromoterHelper Promoter(Cand.first, Cand.second, SSA, InitVal,
L.getLoopPreheader(), ExitBlocks,
InsertPts, LoopToCandidates, LI);<Instruction *, 2>({Cand.first, Cand.second}));
if (Promoted >= MaxProm)
if (MaxNumOfPromotions != -1 && *NumPromoted >= MaxNumOfPromotions)
LLVM_DEBUG(dbgs() << Promoted << " counters promoted for loop (depth="
<< L.getLoopDepth() << ")\n");
return Promoted != 0;
bool allowSpeculativeCounterPromotion(Loop *LP) {
SmallVector<BasicBlock *, 8> ExitingBlocks;
// Not considierered speculative.
if (ExitingBlocks.size() == 1)
return true;
if (ExitingBlocks.size() > SpeculativeCounterPromotionMaxExiting)
return false;
return true;
// Check whether the loop satisfies the basic conditions needed to perform
// Counter Promotions.
bool isPromotionPossible(Loop *LP,
const SmallVectorImpl<BasicBlock *> &LoopExitBlocks) {
// We can't insert into a catchswitch.
if (llvm::any_of(LoopExitBlocks, [](BasicBlock *Exit) {
return isa<CatchSwitchInst>(Exit->getTerminator());
return false;
if (!LP->hasDedicatedExits())
return false;
BasicBlock *PH = LP->getLoopPreheader();
if (!PH)
return false;
return true;
// Returns the max number of Counter Promotions for LP.
unsigned getMaxNumOfPromotionsInLoop(Loop *LP) {
SmallVector<BasicBlock *, 8> LoopExitBlocks;
if (!isPromotionPossible(LP, LoopExitBlocks))
return 0;
SmallVector<BasicBlock *, 8> ExitingBlocks;
// If BFI is set, we do more aggressive promotions based on BFI.
if (BFI)
return (unsigned)-1;
// Not considierered speculative.
if (ExitingBlocks.size() == 1)
return MaxNumOfPromotionsPerLoop;
if (ExitingBlocks.size() > SpeculativeCounterPromotionMaxExiting)
return 0;
// Whether the target block is in a loop does not matter:
if (SpeculativeCounterPromotionToLoop)
return MaxNumOfPromotionsPerLoop;
// Now check the target block:
unsigned MaxProm = MaxNumOfPromotionsPerLoop;
for (auto *TargetBlock : LoopExitBlocks) {
auto *TargetLoop = LI.getLoopFor(TargetBlock);
if (!TargetLoop)
unsigned MaxPromForTarget = getMaxNumOfPromotionsInLoop(TargetLoop);
unsigned PendingCandsInTarget = LoopToCandidates[TargetLoop].size();
MaxProm =
std::min(MaxProm, std::max(MaxPromForTarget, PendingCandsInTarget) -
return MaxProm;
DenseMap<Loop *, SmallVector<LoadStorePair, 8>> &LoopToCandidates;
SmallVector<BasicBlock *, 8> ExitBlocks;
SmallVector<Instruction *, 8> InsertPts;
Loop &L;
LoopInfo &LI;
BlockFrequencyInfo *BFI;
enum class ValueProfilingCallType {
// Individual values are tracked. Currently used for indiret call target
// profiling.
// MemOp: the memop size value profiling.
} // end anonymous namespace
PreservedAnalyses InstrProfiling::run(Module &M, ModuleAnalysisManager &AM) {
FunctionAnalysisManager &FAM =
auto GetTLI = [&FAM](Function &F) -> TargetLibraryInfo & {
return FAM.getResult<TargetLibraryAnalysis>(F);
if (!run(M, GetTLI))
return PreservedAnalyses::all();
return PreservedAnalyses::none();
char InstrProfilingLegacyPass::ID = 0;
InstrProfilingLegacyPass, "instrprof",
"Frontend instrumentation-based coverage lowering.", false, false)
InstrProfilingLegacyPass, "instrprof",
"Frontend instrumentation-based coverage lowering.", false, false)
ModulePass *
llvm::createInstrProfilingLegacyPass(const InstrProfOptions &Options,
bool IsCS) {
return new InstrProfilingLegacyPass(Options, IsCS);
static InstrProfIncrementInst *castToIncrementInst(Instruction *Instr) {
InstrProfIncrementInst *Inc = dyn_cast<InstrProfIncrementInstStep>(Instr);
if (Inc)
return Inc;
return dyn_cast<InstrProfIncrementInst>(Instr);
bool InstrProfiling::lowerIntrinsics(Function *F) {
bool MadeChange = false;
for (BasicBlock &BB : *F) {
for (auto I = BB.begin(), E = BB.end(); I != E;) {
auto Instr = I++;
InstrProfIncrementInst *Inc = castToIncrementInst(&*Instr);
if (Inc) {
MadeChange = true;
} else if (auto *Ind = dyn_cast<InstrProfValueProfileInst>(Instr)) {
MadeChange = true;
if (!MadeChange)
return false;
return true;
bool InstrProfiling::isRuntimeCounterRelocationEnabled() const {
if (RuntimeCounterRelocation.getNumOccurrences() > 0)
return RuntimeCounterRelocation;
return TT.isOSFuchsia();
bool InstrProfiling::isCounterPromotionEnabled() const {
if (DoCounterPromotion.getNumOccurrences() > 0)
return DoCounterPromotion;
return Options.DoCounterPromotion;
void InstrProfiling::promoteCounterLoadStores(Function *F) {
if (!isCounterPromotionEnabled())
DominatorTree DT(*F);
LoopInfo LI(DT);
DenseMap<Loop *, SmallVector<LoadStorePair, 8>> LoopPromotionCandidates;
std::unique_ptr<BlockFrequencyInfo> BFI;
if (Options.UseBFIInPromotion) {
std::unique_ptr<BranchProbabilityInfo> BPI;
BPI.reset(new BranchProbabilityInfo(*F, LI, &GetTLI(*F)));
BFI.reset(new BlockFrequencyInfo(*F, *BPI, LI));
for (const auto &LoadStore : PromotionCandidates) {
auto *CounterLoad = LoadStore.first;
auto *CounterStore = LoadStore.second;
BasicBlock *BB = CounterLoad->getParent();
Loop *ParentLoop = LI.getLoopFor(BB);
if (!ParentLoop)
LoopPromotionCandidates[ParentLoop].emplace_back(CounterLoad, CounterStore);
SmallVector<Loop *, 4> Loops = LI.getLoopsInPreorder();
// Do a post-order traversal of the loops so that counter updates can be
// iteratively hoisted outside the loop nest.
for (auto *Loop : llvm::reverse(Loops)) {
PGOCounterPromoter Promoter(LoopPromotionCandidates, *Loop, LI, BFI.get());;
/// Check if the module contains uses of any profiling intrinsics.
static bool containsProfilingIntrinsics(Module &M) {
if (auto *F = M.getFunction(
if (!F->use_empty())
return true;
if (auto *F = M.getFunction(
if (!F->use_empty())
return true;
if (auto *F = M.getFunction(
if (!F->use_empty())
return true;
return false;
bool InstrProfiling::run(
Module &M, std::function<const TargetLibraryInfo &(Function &F)> GetTLI) {
this->M = &M;
this->GetTLI = std::move(GetTLI);
NamesVar = nullptr;
NamesSize = 0;
TT = Triple(M.getTargetTriple());
// Emit the runtime hook even if no counters are present.
bool MadeChange = emitRuntimeHook();
// Improve compile time by avoiding linear scans when there is no work.
GlobalVariable *CoverageNamesVar =
if (!containsProfilingIntrinsics(M) && !CoverageNamesVar)
return MadeChange;
// We did not know how many value sites there would be inside
// the instrumented function. This is counting the number of instrumented
// target value sites to enter it as field in the profile data variable.
for (Function &F : M) {
InstrProfIncrementInst *FirstProfIncInst = nullptr;
for (BasicBlock &BB : F)
for (auto I = BB.begin(), E = BB.end(); I != E; I++)
if (auto *Ind = dyn_cast<InstrProfValueProfileInst>(I))
else if (FirstProfIncInst == nullptr)
FirstProfIncInst = dyn_cast<InstrProfIncrementInst>(I);
// Value profiling intrinsic lowering requires per-function profile data
// variable to be created first.
if (FirstProfIncInst != nullptr)
for (Function &F : M)
MadeChange |= lowerIntrinsics(&F);
if (CoverageNamesVar) {
MadeChange = true;
if (!MadeChange)
return false;
return true;
static FunctionCallee getOrInsertValueProfilingCall(
Module &M, const TargetLibraryInfo &TLI,
ValueProfilingCallType CallType = ValueProfilingCallType::Default) {
LLVMContext &Ctx = M.getContext();
auto *ReturnTy = Type::getVoidTy(M.getContext());
AttributeList AL;
if (auto AK = TLI.getExtAttrForI32Param(false))
AL = AL.addParamAttribute(M.getContext(), 2, AK);
assert((CallType == ValueProfilingCallType::Default ||
CallType == ValueProfilingCallType::MemOp) &&
"Must be Default or MemOp");
Type *ParamTypes[] = {
#define VALUE_PROF_FUNC_PARAM(ParamType, ParamName, ParamLLVMType) ParamLLVMType
#include "llvm/ProfileData/"
auto *ValueProfilingCallTy =
FunctionType::get(ReturnTy, makeArrayRef(ParamTypes), false);
StringRef FuncName = CallType == ValueProfilingCallType::Default
? getInstrProfValueProfFuncName()
: getInstrProfValueProfMemOpFuncName();
return M.getOrInsertFunction(FuncName, ValueProfilingCallTy, AL);
void InstrProfiling::computeNumValueSiteCounts(InstrProfValueProfileInst *Ind) {
GlobalVariable *Name = Ind->getName();
uint64_t ValueKind = Ind->getValueKind()->getZExtValue();
uint64_t Index = Ind->getIndex()->getZExtValue();
auto It = ProfileDataMap.find(Name);
if (It == ProfileDataMap.end()) {
PerFunctionProfileData PD;
PD.NumValueSites[ValueKind] = Index + 1;
ProfileDataMap[Name] = PD;
} else if (It->second.NumValueSites[ValueKind] <= Index)
It->second.NumValueSites[ValueKind] = Index + 1;
void InstrProfiling::lowerValueProfileInst(InstrProfValueProfileInst *Ind) {
GlobalVariable *Name = Ind->getName();
auto It = ProfileDataMap.find(Name);
assert(It != ProfileDataMap.end() && It->second.DataVar &&
"value profiling detected in function with no counter incerement");
GlobalVariable *DataVar = It->second.DataVar;
uint64_t ValueKind = Ind->getValueKind()->getZExtValue();
uint64_t Index = Ind->getIndex()->getZExtValue();
for (uint32_t Kind = IPVK_First; Kind < ValueKind; ++Kind)
Index += It->second.NumValueSites[Kind];
IRBuilder<> Builder(Ind);
bool IsMemOpSize = (Ind->getValueKind()->getZExtValue() ==
CallInst *Call = nullptr;
auto *TLI = &GetTLI(*Ind->getFunction());
// To support value profiling calls within Windows exception handlers, funclet
// information contained within operand bundles needs to be copied over to
// the library call. This is required for the IR to be processed by the
// WinEHPrepare pass.
SmallVector<OperandBundleDef, 1> OpBundles;
if (!IsMemOpSize) {
Value *Args[3] = {Ind->getTargetValue(),
Builder.CreateBitCast(DataVar, Builder.getInt8PtrTy()),
Call = Builder.CreateCall(getOrInsertValueProfilingCall(*M, *TLI), Args,
} else {
Value *Args[3] = {Ind->getTargetValue(),
Builder.CreateBitCast(DataVar, Builder.getInt8PtrTy()),
Call = Builder.CreateCall(
getOrInsertValueProfilingCall(*M, *TLI, ValueProfilingCallType::MemOp),
Args, OpBundles);
if (auto AK = TLI->getExtAttrForI32Param(false))
Call->addParamAttr(2, AK);
void InstrProfiling::lowerIncrement(InstrProfIncrementInst *Inc) {
GlobalVariable *Counters = getOrCreateRegionCounters(Inc);
IRBuilder<> Builder(Inc);
uint64_t Index = Inc->getIndex()->getZExtValue();
Value *Addr = Builder.CreateConstInBoundsGEP2_64(Counters->getValueType(),
Counters, 0, Index);
if (isRuntimeCounterRelocationEnabled()) {
Type *Int64Ty = Type::getInt64Ty(M->getContext());
Type *Int64PtrTy = Type::getInt64PtrTy(M->getContext());
Function *Fn = Inc->getParent()->getParent();
Instruction &I = Fn->getEntryBlock().front();
LoadInst *LI = dyn_cast<LoadInst>(&I);
if (!LI) {
IRBuilder<> Builder(&I);
Type *Int64Ty = Type::getInt64Ty(M->getContext());
GlobalVariable *Bias = M->getGlobalVariable(getInstrProfCounterBiasVarName());
if (!Bias) {
Bias = new GlobalVariable(*M, Int64Ty, false, GlobalValue::LinkOnceODRLinkage,
LI = Builder.CreateLoad(Int64Ty, Bias);
auto *Add = Builder.CreateAdd(Builder.CreatePtrToInt(Addr, Int64Ty), LI);
Addr = Builder.CreateIntToPtr(Add, Int64PtrTy);
if (Options.Atomic || AtomicCounterUpdateAll ||
(Index == 0 && AtomicFirstCounter)) {
Builder.CreateAtomicRMW(AtomicRMWInst::Add, Addr, Inc->getStep(),
MaybeAlign(), AtomicOrdering::Monotonic);
} else {
Value *IncStep = Inc->getStep();
Value *Load = Builder.CreateLoad(IncStep->getType(), Addr, "pgocount");
auto *Count = Builder.CreateAdd(Load, Inc->getStep());
auto *Store = Builder.CreateStore(Count, Addr);
if (isCounterPromotionEnabled())
PromotionCandidates.emplace_back(cast<Instruction>(Load), Store);
void InstrProfiling::lowerCoverageData(GlobalVariable *CoverageNamesVar) {
ConstantArray *Names =
for (unsigned I = 0, E = Names->getNumOperands(); I < E; ++I) {
Constant *NC = Names->getOperand(I);
Value *V = NC->stripPointerCasts();
assert(isa<GlobalVariable>(V) && "Missing reference to function name");
GlobalVariable *Name = cast<GlobalVariable>(V);
/// Get the name of a profiling variable for a particular function.
static std::string getVarName(InstrProfIncrementInst *Inc, StringRef Prefix) {
StringRef NamePrefix = getInstrProfNameVarPrefix();
StringRef Name = Inc->getName()->getName().substr(NamePrefix.size());
Function *F = Inc->getParent()->getParent();
Module *M = F->getParent();
if (!DoHashBasedCounterSplit || !isIRPGOFlagSet(M) ||
return (Prefix + Name).str();
uint64_t FuncHash = Inc->getHash()->getZExtValue();
SmallVector<char, 24> HashPostfix;
if (Name.endswith((Twine(".") + Twine(FuncHash)).toStringRef(HashPostfix)))
return (Prefix + Name).str();
return (Prefix + Name + "." + Twine(FuncHash)).str();
static inline bool shouldRecordFunctionAddr(Function *F) {
// Check the linkage
bool HasAvailableExternallyLinkage = F->hasAvailableExternallyLinkage();
if (!F->hasLinkOnceLinkage() && !F->hasLocalLinkage() &&
return true;
// A function marked 'alwaysinline' with available_externally linkage can't
// have its address taken. Doing so would create an undefined external ref to
// the function, which would fail to link.
if (HasAvailableExternallyLinkage &&
return false;
// Prohibit function address recording if the function is both internal and
// COMDAT. This avoids the profile data variable referencing internal symbols
// in COMDAT.
if (F->hasLocalLinkage() && F->hasComdat())
return false;
// Check uses of this function for other than direct calls or invokes to it.
// Inline virtual functions have linkeOnceODR linkage. When a key method
// exists, the vtable will only be emitted in the TU where the key method
// is defined. In a TU where vtable is not available, the function won't
// be 'addresstaken'. If its address is not recorded here, the profile data
// with missing address may be picked by the linker leading to missing
// indirect call target info.
return F->hasAddressTaken() || F->hasLinkOnceLinkage();
static bool needsRuntimeRegistrationOfSectionRange(const Triple &TT) {
// Don't do this for Darwin. compiler-rt uses linker magic.
if (TT.isOSDarwin())
return false;
// Use linker script magic to get data/cnts/name start/end.
if (TT.isOSLinux() || TT.isOSFreeBSD() || TT.isOSNetBSD() ||
TT.isOSSolaris() || TT.isOSFuchsia() || TT.isPS4CPU() ||
return false;
return true;
GlobalVariable *
InstrProfiling::getOrCreateRegionCounters(InstrProfIncrementInst *Inc) {
GlobalVariable *NamePtr = Inc->getName();
auto It = ProfileDataMap.find(NamePtr);
PerFunctionProfileData PD;
if (It != ProfileDataMap.end()) {
if (It->second.RegionCounters)
return It->second.RegionCounters;
PD = It->second;
// Match the linkage and visibility of the name global. COFF supports using
// comdats with internal symbols, so do that if we can.
Function *Fn = Inc->getParent()->getParent();
GlobalValue::LinkageTypes Linkage = NamePtr->getLinkage();
GlobalValue::VisibilityTypes Visibility = NamePtr->getVisibility();
if (TT.isOSBinFormatCOFF()) {
Linkage = GlobalValue::InternalLinkage;
Visibility = GlobalValue::DefaultVisibility;
// Move the name variable to the right section. Place them in a COMDAT group
// if the associated function is a COMDAT. This will make sure that only one
// copy of counters of the COMDAT function will be emitted after linking. Keep
// in mind that this pass may run before the inliner, so we need to create a
// new comdat group for the counters and profiling data. If we use the comdat
// of the parent function, that will result in relocations against discarded
// sections.
bool NeedComdat = needsComdatForCounter(*Fn, *M);
if (NeedComdat) {
if (TT.isOSBinFormatCOFF()) {
// For COFF, put the counters, data, and values each into their own
// comdats. We can't use a group because the Visual C++ linker will
// report duplicate symbol errors if there are multiple external symbols
// with the same name marked IMAGE_COMDAT_SELECT_ASSOCIATIVE.
Linkage = GlobalValue::LinkOnceODRLinkage;
Visibility = GlobalValue::HiddenVisibility;
std::string DataVarName = getVarName(Inc, getInstrProfDataVarPrefix());
auto MaybeSetComdat = [=](GlobalVariable *GV) {
// For ELF, when not using COMDAT, put counters, data and values into
// a noduplicates COMDAT which is lowered to a zero-flag section group.
// This allows linker GC to discard the entire group when the function
// is discarded.
bool UseComdat = (NeedComdat || TT.isOSBinFormatELF());
if (UseComdat) {
auto GroupName = TT.isOSBinFormatCOFF() ? GV->getName() : DataVarName;
Comdat *C = M->getOrInsertComdat(GroupName);
if (!NeedComdat)
uint64_t NumCounters = Inc->getNumCounters()->getZExtValue();
LLVMContext &Ctx = M->getContext();
ArrayType *CounterTy = ArrayType::get(Type::getInt64Ty(Ctx), NumCounters);
// Create the counters variable.
auto *CounterPtr =
new GlobalVariable(*M, CounterTy, false, Linkage,
getVarName(Inc, getInstrProfCountersVarPrefix()));
getInstrProfSectionName(IPSK_cnts, TT.getObjectFormat()));
auto *Int8PtrTy = Type::getInt8PtrTy(Ctx);
// Allocate statically the array of pointers to value profile nodes for
// the current function.
Constant *ValuesPtrExpr = ConstantPointerNull::get(Int8PtrTy);
if (ValueProfileStaticAlloc && !needsRuntimeRegistrationOfSectionRange(TT)) {
uint64_t NS = 0;
for (uint32_t Kind = IPVK_First; Kind <= IPVK_Last; ++Kind)
NS += PD.NumValueSites[Kind];
if (NS) {
ArrayType *ValuesTy = ArrayType::get(Type::getInt64Ty(Ctx), NS);
auto *ValuesVar =
new GlobalVariable(*M, ValuesTy, false, Linkage,
getVarName(Inc, getInstrProfValuesVarPrefix()));
getInstrProfSectionName(IPSK_vals, TT.getObjectFormat()));
ValuesPtrExpr =
ConstantExpr::getBitCast(ValuesVar, Type::getInt8PtrTy(Ctx));
// Create data variable.
auto *Int16Ty = Type::getInt16Ty(Ctx);
auto *Int16ArrayTy = ArrayType::get(Int16Ty, IPVK_Last + 1);
Type *DataTypes[] = {
#define INSTR_PROF_DATA(Type, LLVMType, Name, Init) LLVMType,
#include "llvm/ProfileData/"
auto *DataTy = StructType::get(Ctx, makeArrayRef(DataTypes));
Constant *FunctionAddr = shouldRecordFunctionAddr(Fn)
? ConstantExpr::getBitCast(Fn, Int8PtrTy)
: ConstantPointerNull::get(Int8PtrTy);
Constant *Int16ArrayVals[IPVK_Last + 1];
for (uint32_t Kind = IPVK_First; Kind <= IPVK_Last; ++Kind)
Int16ArrayVals[Kind] = ConstantInt::get(Int16Ty, PD.NumValueSites[Kind]);
Constant *DataVals[] = {
#define INSTR_PROF_DATA(Type, LLVMType, Name, Init) Init,
#include "llvm/ProfileData/"
auto *Data =
new GlobalVariable(*M, DataTy, false, Linkage,
ConstantStruct::get(DataTy, DataVals), DataVarName);
Data->setSection(getInstrProfSectionName(IPSK_data, TT.getObjectFormat()));
PD.RegionCounters = CounterPtr;
PD.DataVar = Data;
ProfileDataMap[NamePtr] = PD;
// Mark the data variable as used so that it isn't stripped out.
// Now that the linkage set by the FE has been passed to the data and counter
// variables, reset Name variable's linkage and visibility to private so that
// it can be removed later by the compiler.
// Collect the referenced names to be used by emitNameData.
return CounterPtr;
void InstrProfiling::emitVNodes() {
if (!ValueProfileStaticAlloc)
// For now only support this on platforms that do
// not require runtime registration to discover
// named section start/end.
if (needsRuntimeRegistrationOfSectionRange(TT))
size_t TotalNS = 0;
for (auto &PD : ProfileDataMap) {
for (uint32_t Kind = IPVK_First; Kind <= IPVK_Last; ++Kind)
TotalNS += PD.second.NumValueSites[Kind];
if (!TotalNS)
uint64_t NumCounters = TotalNS * NumCountersPerValueSite;
// Heuristic for small programs with very few total value sites.
// The default value of vp-counters-per-site is chosen based on
// the observation that large apps usually have a low percentage
// of value sites that actually have any profile data, and thus
// the average number of counters per site is low. For small
// apps with very few sites, this may not be true. Bump up the
// number of counters in this case.
NumCounters = std::max(INSTR_PROF_MIN_VAL_COUNTS, (int)NumCounters * 2);
auto &Ctx = M->getContext();
Type *VNodeTypes[] = {
#define INSTR_PROF_VALUE_NODE(Type, LLVMType, Name, Init) LLVMType,
#include "llvm/ProfileData/"
auto *VNodeTy = StructType::get(Ctx, makeArrayRef(VNodeTypes));
ArrayType *VNodesTy = ArrayType::get(VNodeTy, NumCounters);
auto *VNodesVar = new GlobalVariable(
*M, VNodesTy, false, GlobalValue::PrivateLinkage,
Constant::getNullValue(VNodesTy), getInstrProfVNodesVarName());
getInstrProfSectionName(IPSK_vnodes, TT.getObjectFormat()));
// VNodesVar is used by runtime but not referenced via relocation by other
// sections. Conservatively make it linker retained.
void InstrProfiling::emitNameData() {
std::string UncompressedData;
if (ReferencedNames.empty())
std::string CompressedNameStr;
if (Error E = collectPGOFuncNameStrings(ReferencedNames, CompressedNameStr,
DoInstrProfNameCompression)) {
report_fatal_error(toString(std::move(E)), false);
auto &Ctx = M->getContext();
auto *NamesVal = ConstantDataArray::getString(
Ctx, StringRef(CompressedNameStr), false);
NamesVar = new GlobalVariable(*M, NamesVal->getType(), true,
GlobalValue::PrivateLinkage, NamesVal,
NamesSize = CompressedNameStr.size();
getInstrProfSectionName(IPSK_name, TT.getObjectFormat()));
// On COFF, it's important to reduce the alignment down to 1 to prevent the
// linker from inserting padding before the start of the names section or
// between names entries.
// NamesVar is used by runtime but not referenced via relocation by other
// sections. Conservatively make it linker retained.
for (auto *NamePtr : ReferencedNames)
void InstrProfiling::emitRegistration() {
if (!needsRuntimeRegistrationOfSectionRange(TT))
// Construct the function.
auto *VoidTy = Type::getVoidTy(M->getContext());
auto *VoidPtrTy = Type::getInt8PtrTy(M->getContext());
auto *Int64Ty = Type::getInt64Ty(M->getContext());
auto *RegisterFTy = FunctionType::get(VoidTy, false);
auto *RegisterF = Function::Create(RegisterFTy, GlobalValue::InternalLinkage,
getInstrProfRegFuncsName(), M);
if (Options.NoRedZone)
auto *RuntimeRegisterTy = FunctionType::get(VoidTy, VoidPtrTy, false);
auto *RuntimeRegisterF =
Function::Create(RuntimeRegisterTy, GlobalVariable::ExternalLinkage,
getInstrProfRegFuncName(), M);
IRBuilder<> IRB(BasicBlock::Create(M->getContext(), "", RegisterF));
for (Value *Data : CompilerUsedVars)
if (!isa<Function>(Data))
IRB.CreateCall(RuntimeRegisterF, IRB.CreateBitCast(Data, VoidPtrTy));
for (Value *Data : UsedVars)
if (Data != NamesVar && !isa<Function>(Data))
IRB.CreateCall(RuntimeRegisterF, IRB.CreateBitCast(Data, VoidPtrTy));
if (NamesVar) {
Type *ParamTypes[] = {VoidPtrTy, Int64Ty};
auto *NamesRegisterTy =
FunctionType::get(VoidTy, makeArrayRef(ParamTypes), false);
auto *NamesRegisterF =
Function::Create(NamesRegisterTy, GlobalVariable::ExternalLinkage,
getInstrProfNamesRegFuncName(), M);
IRB.CreateCall(NamesRegisterF, {IRB.CreateBitCast(NamesVar, VoidPtrTy),
bool InstrProfiling::emitRuntimeHook() {
// We expect the linker to be invoked with -u<hook_var> flag for Linux or
// Fuchsia, in which case there is no need to emit the user function.
if (TT.isOSLinux() || TT.isOSFuchsia())
return false;
// If the module's provided its own runtime, we don't need to do anything.
if (M->getGlobalVariable(getInstrProfRuntimeHookVarName()))
return false;
// Declare an external variable that will pull in the runtime initialization.
auto *Int32Ty = Type::getInt32Ty(M->getContext());
auto *Var =
new GlobalVariable(*M, Int32Ty, false, GlobalValue::ExternalLinkage,
nullptr, getInstrProfRuntimeHookVarName());
// Make a function that uses it.
auto *User = Function::Create(FunctionType::get(Int32Ty, false),
getInstrProfRuntimeHookVarUseFuncName(), M);
if (Options.NoRedZone)
if (TT.supportsCOMDAT())
IRBuilder<> IRB(BasicBlock::Create(M->getContext(), "", User));
auto *Load = IRB.CreateLoad(Int32Ty, Var);
// Mark the user variable as used so that it isn't stripped out.
return true;
void InstrProfiling::emitUses() {
// The metadata sections are parallel arrays. Optimizers (e.g.
// GlobalOpt/ConstantMerge) may not discard associated sections as a unit, so
// we conservatively retain all unconditionally in the compiler.
// On ELF, the linker can guarantee the associated sections will be retained
// or discarded as a unit, so llvm.compiler.used is sufficient. Otherwise,
// conservatively make all of them retained by the linker.
if (TT.isOSBinFormatELF())
appendToCompilerUsed(*M, CompilerUsedVars);
appendToUsed(*M, CompilerUsedVars);
// We do not add proper references from used metadata sections to NamesVar and
// VNodesVar, so we have to be conservative and place them in llvm.used
// regardless of the target,
appendToUsed(*M, UsedVars);
void InstrProfiling::emitInitialization() {
// Create ProfileFileName variable. Don't don't this for the
// context-sensitive instrumentation lowering: This lowering is after
// LTO/ThinLTO linking. Pass PGOInstrumentationGenCreateVar should
// have already create the variable before LTO/ThinLTO linking.
if (!IsCS)
createProfileFileNameVar(*M, Options.InstrProfileOutput);
Function *RegisterF = M->getFunction(getInstrProfRegFuncsName());
if (!RegisterF)
// Create the initialization function.
auto *VoidTy = Type::getVoidTy(M->getContext());
auto *F = Function::Create(FunctionType::get(VoidTy, false),
getInstrProfInitFuncName(), M);
if (Options.NoRedZone)
// Add the basic block and the necessary calls.
IRBuilder<> IRB(BasicBlock::Create(M->getContext(), "", F));
IRB.CreateCall(RegisterF, {});
appendToGlobalCtors(*M, F, 0);