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llvm-project/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp

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//===-- PGOInstrumentation.cpp - MST-based PGO Instrumentation ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements PGO instrumentation using a minimum spanning tree based
// on the following paper:
// [1] Donald E. Knuth, Francis R. Stevenson. Optimal measurement of points
// for program frequency counts. BIT Numerical Mathematics 1973, Volume 13,
// Issue 3, pp 313-322
// The idea of the algorithm based on the fact that for each node (except for
// the entry and exit), the sum of incoming edge counts equals the sum of
// outgoing edge counts. The count of edge on spanning tree can be derived from
// those edges not on the spanning tree. Knuth proves this method instruments
// the minimum number of edges.
//
// The minimal spanning tree here is actually a maximum weight tree -- on-tree
// edges have higher frequencies (more likely to execute). The idea is to
// instrument those less frequently executed edges to reduce the runtime
// overhead of instrumented binaries.
//
// This file contains two passes:
// (1) Pass PGOInstrumentationGen which instruments the IR to generate edge
// count profile, and generates the instrumentation for indirect call
// profiling.
// (2) Pass PGOInstrumentationUse which reads the edge count profile and
// annotates the branch weights. It also reads the indirect call value
// profiling records and annotate the indirect call instructions.
//
// To get the precise counter information, These two passes need to invoke at
// the same compilation point (so they see the same IR). For pass
// PGOInstrumentationGen, the real work is done in instrumentOneFunc(). For
// pass PGOInstrumentationUse, the real work in done in class PGOUseFunc and
// the profile is opened in module level and passed to each PGOUseFunc instance.
// The shared code for PGOInstrumentationGen and PGOInstrumentationUse is put
// in class FuncPGOInstrumentation.
//
// Class PGOEdge represents a CFG edge and some auxiliary information. Class
// BBInfo contains auxiliary information for each BB. These two classes are used
// in pass PGOInstrumentationGen. Class PGOUseEdge and UseBBInfo are the derived
// class of PGOEdge and BBInfo, respectively. They contains extra data structure
// used in populating profile counters.
// The MST implementation is in Class CFGMST (CFGMST.h).
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/PGOInstrumentation.h"
#include "CFGMST.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/CFG.h"
#include "llvm/Analysis/IndirectCallSiteVisitor.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/DiagnosticInfo.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/ProfileData/InstrProfReader.h"
#include "llvm/ProfileData/ProfileCommon.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/JamCRC.h"
#include "llvm/Transforms/Instrumentation.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include <algorithm>
#include <string>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "pgo-instrumentation"
STATISTIC(NumOfPGOInstrument, "Number of edges instrumented.");
STATISTIC(NumOfPGOSelectInsts, "Number of select instruction instrumented.");
STATISTIC(NumOfPGOEdge, "Number of edges.");
STATISTIC(NumOfPGOBB, "Number of basic-blocks.");
STATISTIC(NumOfPGOSplit, "Number of critical edge splits.");
STATISTIC(NumOfPGOFunc, "Number of functions having valid profile counts.");
STATISTIC(NumOfPGOMismatch, "Number of functions having mismatch profile.");
STATISTIC(NumOfPGOMissing, "Number of functions without profile.");
STATISTIC(NumOfPGOICall, "Number of indirect call value instrumentations.");
// Command line option to specify the file to read profile from. This is
// mainly used for testing.
static cl::opt<std::string>
PGOTestProfileFile("pgo-test-profile-file", cl::init(""), cl::Hidden,
cl::value_desc("filename"),
cl::desc("Specify the path of profile data file. This is"
"mainly for test purpose."));
// Command line option to disable value profiling. The default is false:
// i.e. value profiling is enabled by default. This is for debug purpose.
static cl::opt<bool> DisableValueProfiling("disable-vp", cl::init(false),
cl::Hidden,
cl::desc("Disable Value Profiling"));
// Command line option to set the maximum number of VP annotations to write to
// the metadata for a single indirect call callsite.
static cl::opt<unsigned> MaxNumAnnotations(
"icp-max-annotations", cl::init(3), cl::Hidden, cl::ZeroOrMore,
cl::desc("Max number of annotations for a single indirect "
"call callsite"));
// Command line option to control appending FunctionHash to the name of a COMDAT
// function. This is to avoid the hash mismatch caused by the preinliner.
static cl::opt<bool> DoComdatRenaming(
"do-comdat-renaming", cl::init(true), cl::Hidden,
cl::desc("Append function hash to the name of COMDAT function to avoid "
"function hash mismatch due to the preinliner"));
// Command line option to enable/disable the warning about missing profile
// information.
static cl::opt<bool> PGOWarnMissing("pgo-warn-missing-function",
cl::init(false),
cl::Hidden);
// Command line option to enable/disable the warning about a hash mismatch in
// the profile data.
static cl::opt<bool> NoPGOWarnMismatch("no-pgo-warn-mismatch", cl::init(false),
cl::Hidden);
// Command line option to enable/disable select instruction instrumentation.
static cl::opt<bool> PGOInstrSelect("pgo-instr-select", cl::init(true),
cl::Hidden);
namespace {
/// The select instruction visitor plays three roles specified
/// by the mode. In \c VM_counting mode, it simply counts the number of
/// select instructions. In \c VM_instrument mode, it inserts code to count
/// the number times TrueValue of select is taken. In \c VM_annotate mode,
/// it reads the profile data and annotate the select instruction with metadata.
enum VisitMode { VM_counting, VM_instrument, VM_annotate };
class PGOUseFunc;
/// Instruction Visitor class to visit select instructions.
struct SelectInstVisitor : public InstVisitor<SelectInstVisitor> {
Function &F;
unsigned NSIs = 0; // Number of select instructions instrumented.
VisitMode Mode = VM_counting; // Visiting mode.
unsigned *CurCtrIdx = nullptr; // Pointer to current counter index.
unsigned TotalNumCtrs = 0; // Total number of counters
GlobalVariable *FuncNameVar = nullptr;
uint64_t FuncHash = 0;
PGOUseFunc *UseFunc = nullptr;
SelectInstVisitor(Function &Func) : F(Func) {}
void countSelects(Function &Func) {
Mode = VM_counting;
visit(Func);
}
// Visit the IR stream and instrument all select instructions. \p
// Ind is a pointer to the counter index variable; \p TotalNC
// is the total number of counters; \p FNV is the pointer to the
// PGO function name var; \p FHash is the function hash.
void instrumentSelects(Function &Func, unsigned *Ind, unsigned TotalNC,
GlobalVariable *FNV, uint64_t FHash) {
Mode = VM_instrument;
CurCtrIdx = Ind;
TotalNumCtrs = TotalNC;
FuncHash = FHash;
FuncNameVar = FNV;
visit(Func);
}
// Visit the IR stream and annotate all select instructions.
void annotateSelects(Function &Func, PGOUseFunc *UF, unsigned *Ind) {
Mode = VM_annotate;
UseFunc = UF;
CurCtrIdx = Ind;
visit(Func);
}
void instrumentOneSelectInst(SelectInst &SI);
void annotateOneSelectInst(SelectInst &SI);
// Visit \p SI instruction and perform tasks according to visit mode.
void visitSelectInst(SelectInst &SI);
unsigned getNumOfSelectInsts() const { return NSIs; }
};
class PGOInstrumentationGenLegacyPass : public ModulePass {
public:
static char ID;
PGOInstrumentationGenLegacyPass() : ModulePass(ID) {
initializePGOInstrumentationGenLegacyPassPass(
*PassRegistry::getPassRegistry());
}
const char *getPassName() const override {
return "PGOInstrumentationGenPass";
}
private:
bool runOnModule(Module &M) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<BlockFrequencyInfoWrapperPass>();
}
};
class PGOInstrumentationUseLegacyPass : public ModulePass {
public:
static char ID;
// Provide the profile filename as the parameter.
PGOInstrumentationUseLegacyPass(std::string Filename = "")
: ModulePass(ID), ProfileFileName(std::move(Filename)) {
if (!PGOTestProfileFile.empty())
ProfileFileName = PGOTestProfileFile;
initializePGOInstrumentationUseLegacyPassPass(
*PassRegistry::getPassRegistry());
}
const char *getPassName() const override {
return "PGOInstrumentationUsePass";
}
private:
std::string ProfileFileName;
bool runOnModule(Module &M) override;
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<BlockFrequencyInfoWrapperPass>();
}
};
} // end anonymous namespace
char PGOInstrumentationGenLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(PGOInstrumentationGenLegacyPass, "pgo-instr-gen",
"PGO instrumentation.", false, false)
INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
INITIALIZE_PASS_END(PGOInstrumentationGenLegacyPass, "pgo-instr-gen",
"PGO instrumentation.", false, false)
ModulePass *llvm::createPGOInstrumentationGenLegacyPass() {
return new PGOInstrumentationGenLegacyPass();
}
char PGOInstrumentationUseLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(PGOInstrumentationUseLegacyPass, "pgo-instr-use",
"Read PGO instrumentation profile.", false, false)
INITIALIZE_PASS_DEPENDENCY(BlockFrequencyInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(BranchProbabilityInfoWrapperPass)
INITIALIZE_PASS_END(PGOInstrumentationUseLegacyPass, "pgo-instr-use",
"Read PGO instrumentation profile.", false, false)
ModulePass *llvm::createPGOInstrumentationUseLegacyPass(StringRef Filename) {
return new PGOInstrumentationUseLegacyPass(Filename.str());
}
namespace {
/// \brief An MST based instrumentation for PGO
///
/// Implements a Minimum Spanning Tree (MST) based instrumentation for PGO
/// in the function level.
struct PGOEdge {
// This class implements the CFG edges. Note the CFG can be a multi-graph.
// So there might be multiple edges with same SrcBB and DestBB.
const BasicBlock *SrcBB;
const BasicBlock *DestBB;
uint64_t Weight;
bool InMST;
bool Removed;
bool IsCritical;
PGOEdge(const BasicBlock *Src, const BasicBlock *Dest, unsigned W = 1)
: SrcBB(Src), DestBB(Dest), Weight(W), InMST(false), Removed(false),
IsCritical(false) {}
// Return the information string of an edge.
const std::string infoString() const {
return (Twine(Removed ? "-" : " ") + (InMST ? " " : "*") +
(IsCritical ? "c" : " ") + " W=" + Twine(Weight)).str();
}
};
// This class stores the auxiliary information for each BB.
struct BBInfo {
BBInfo *Group;
uint32_t Index;
uint32_t Rank;
BBInfo(unsigned IX) : Group(this), Index(IX), Rank(0) {}
// Return the information string of this object.
const std::string infoString() const {
return (Twine("Index=") + Twine(Index)).str();
}
};
// This class implements the CFG edges. Note the CFG can be a multi-graph.
template <class Edge, class BBInfo> class FuncPGOInstrumentation {
private:
Function &F;
void computeCFGHash();
void renameComdatFunction();
// A map that stores the Comdat group in function F.
std::unordered_multimap<Comdat *, GlobalValue *> &ComdatMembers;
public:
SelectInstVisitor SIVisitor;
std::string FuncName;
GlobalVariable *FuncNameVar;
// CFG hash value for this function.
uint64_t FunctionHash;
// The Minimum Spanning Tree of function CFG.
CFGMST<Edge, BBInfo> MST;
// Give an edge, find the BB that will be instrumented.
// Return nullptr if there is no BB to be instrumented.
BasicBlock *getInstrBB(Edge *E);
// Return the auxiliary BB information.
BBInfo &getBBInfo(const BasicBlock *BB) const { return MST.getBBInfo(BB); }
// Dump edges and BB information.
void dumpInfo(std::string Str = "") const {
MST.dumpEdges(dbgs(), Twine("Dump Function ") + FuncName + " Hash: " +
Twine(FunctionHash) + "\t" + Str);
}
FuncPGOInstrumentation(
Function &Func,
std::unordered_multimap<Comdat *, GlobalValue *> &ComdatMembers,
bool CreateGlobalVar = false, BranchProbabilityInfo *BPI = nullptr,
BlockFrequencyInfo *BFI = nullptr)
: F(Func), ComdatMembers(ComdatMembers), SIVisitor(Func), FunctionHash(0),
MST(F, BPI, BFI) {
// This should be done before CFG hash computation.
SIVisitor.countSelects(Func);
NumOfPGOSelectInsts += SIVisitor.getNumOfSelectInsts();
FuncName = getPGOFuncName(F);
computeCFGHash();
if (ComdatMembers.size())
renameComdatFunction();
DEBUG(dumpInfo("after CFGMST"));
NumOfPGOBB += MST.BBInfos.size();
for (auto &E : MST.AllEdges) {
if (E->Removed)
continue;
NumOfPGOEdge++;
if (!E->InMST)
NumOfPGOInstrument++;
}
if (CreateGlobalVar)
FuncNameVar = createPGOFuncNameVar(F, FuncName);
}
// Return the number of profile counters needed for the function.
unsigned getNumCounters() {
unsigned NumCounters = 0;
for (auto &E : this->MST.AllEdges) {
if (!E->InMST && !E->Removed)
NumCounters++;
}
return NumCounters + SIVisitor.getNumOfSelectInsts();
}
};
// Compute Hash value for the CFG: the lower 32 bits are CRC32 of the index
// value of each BB in the CFG. The higher 32 bits record the number of edges.
template <class Edge, class BBInfo>
void FuncPGOInstrumentation<Edge, BBInfo>::computeCFGHash() {
std::vector<char> Indexes;
JamCRC JC;
for (auto &BB : F) {
const TerminatorInst *TI = BB.getTerminator();
for (unsigned I = 0, E = TI->getNumSuccessors(); I != E; ++I) {
BasicBlock *Succ = TI->getSuccessor(I);
uint32_t Index = getBBInfo(Succ).Index;
for (int J = 0; J < 4; J++)
Indexes.push_back((char)(Index >> (J * 8)));
}
}
JC.update(Indexes);
FunctionHash = (uint64_t)SIVisitor.getNumOfSelectInsts() << 56 |
(uint64_t)findIndirectCallSites(F).size() << 48 |
(uint64_t)MST.AllEdges.size() << 32 | JC.getCRC();
}
// Check if we can safely rename this Comdat function.
static bool canRenameComdat(
Function &F,
std::unordered_multimap<Comdat *, GlobalValue *> &ComdatMembers) {
if (F.getName().empty())
return false;
if (!needsComdatForCounter(F, *(F.getParent())))
return false;
// Only safe to do if this function may be discarded if it is not used
// in the compilation unit.
if (!GlobalValue::isDiscardableIfUnused(F.getLinkage()))
return false;
// For AvailableExternallyLinkage functions.
if (!F.hasComdat()) {
assert(F.getLinkage() == GlobalValue::AvailableExternallyLinkage);
return true;
}
// FIXME: Current only handle those Comdat groups that only containing one
// function and function aliases.
// (1) For a Comdat group containing multiple functions, we need to have a
// unique postfix based on the hashes for each function. There is a
// non-trivial code refactoring to do this efficiently.
// (2) Variables can not be renamed, so we can not rename Comdat function in a
// group including global vars.
Comdat *C = F.getComdat();
for (auto &&CM : make_range(ComdatMembers.equal_range(C))) {
if (dyn_cast<GlobalAlias>(CM.second))
continue;
Function *FM = dyn_cast<Function>(CM.second);
if (FM != &F)
return false;
}
return true;
}
// Append the CFGHash to the Comdat function name.
template <class Edge, class BBInfo>
void FuncPGOInstrumentation<Edge, BBInfo>::renameComdatFunction() {
if (!canRenameComdat(F, ComdatMembers))
return;
std::string NewFuncName =
Twine(F.getName() + "." + Twine(FunctionHash)).str();
F.setName(Twine(NewFuncName));
FuncName = Twine(FuncName + "." + Twine(FunctionHash)).str();
Comdat *NewComdat;
Module *M = F.getParent();
// For AvailableExternallyLinkage functions, change the linkage to
// LinkOnceODR and put them into comdat. This is because after renaming, there
// is no backup external copy available for the function.
if (!F.hasComdat()) {
assert(F.getLinkage() == GlobalValue::AvailableExternallyLinkage);
NewComdat = M->getOrInsertComdat(StringRef(NewFuncName));
F.setLinkage(GlobalValue::LinkOnceODRLinkage);
F.setComdat(NewComdat);
return;
}
// This function belongs to a single function Comdat group.
Comdat *OrigComdat = F.getComdat();
std::string NewComdatName =
Twine(OrigComdat->getName() + "." + Twine(FunctionHash)).str();
NewComdat = M->getOrInsertComdat(StringRef(NewComdatName));
NewComdat->setSelectionKind(OrigComdat->getSelectionKind());
for (auto &&CM : make_range(ComdatMembers.equal_range(OrigComdat))) {
if (GlobalAlias *GA = dyn_cast<GlobalAlias>(CM.second)) {
// For aliases, change the name directly.
assert(dyn_cast<Function>(GA->getAliasee()->stripPointerCasts()) == &F);
GA->setName(Twine(GA->getName() + "." + Twine(FunctionHash)));
continue;
}
// Must be a function.
Function *CF = dyn_cast<Function>(CM.second);
assert(CF);
CF->setComdat(NewComdat);
}
}
// Given a CFG E to be instrumented, find which BB to place the instrumented
// code. The function will split the critical edge if necessary.
template <class Edge, class BBInfo>
BasicBlock *FuncPGOInstrumentation<Edge, BBInfo>::getInstrBB(Edge *E) {
if (E->InMST || E->Removed)
return nullptr;
BasicBlock *SrcBB = const_cast<BasicBlock *>(E->SrcBB);
BasicBlock *DestBB = const_cast<BasicBlock *>(E->DestBB);
// For a fake edge, instrument the real BB.
if (SrcBB == nullptr)
return DestBB;
if (DestBB == nullptr)
return SrcBB;
// Instrument the SrcBB if it has a single successor,
// otherwise, the DestBB if this is not a critical edge.
TerminatorInst *TI = SrcBB->getTerminator();
if (TI->getNumSuccessors() <= 1)
return SrcBB;
if (!E->IsCritical)
return DestBB;
// For a critical edge, we have to split. Instrument the newly
// created BB.
NumOfPGOSplit++;
DEBUG(dbgs() << "Split critical edge: " << getBBInfo(SrcBB).Index << " --> "
<< getBBInfo(DestBB).Index << "\n");
unsigned SuccNum = GetSuccessorNumber(SrcBB, DestBB);
BasicBlock *InstrBB = SplitCriticalEdge(TI, SuccNum);
assert(InstrBB && "Critical edge is not split");
E->Removed = true;
return InstrBB;
}
// Visit all edge and instrument the edges not in MST, and do value profiling.
// Critical edges will be split.
static void instrumentOneFunc(
Function &F, Module *M, BranchProbabilityInfo *BPI, BlockFrequencyInfo *BFI,
std::unordered_multimap<Comdat *, GlobalValue *> &ComdatMembers) {
FuncPGOInstrumentation<PGOEdge, BBInfo> FuncInfo(F, ComdatMembers, true, BPI,
BFI);
unsigned NumCounters = FuncInfo.getNumCounters();
uint32_t I = 0;
Type *I8PtrTy = Type::getInt8PtrTy(M->getContext());
for (auto &E : FuncInfo.MST.AllEdges) {
BasicBlock *InstrBB = FuncInfo.getInstrBB(E.get());
if (!InstrBB)
continue;
IRBuilder<> Builder(InstrBB, InstrBB->getFirstInsertionPt());
assert(Builder.GetInsertPoint() != InstrBB->end() &&
"Cannot get the Instrumentation point");
Builder.CreateCall(
Intrinsic::getDeclaration(M, Intrinsic::instrprof_increment),
{llvm::ConstantExpr::getBitCast(FuncInfo.FuncNameVar, I8PtrTy),
Builder.getInt64(FuncInfo.FunctionHash), Builder.getInt32(NumCounters),
Builder.getInt32(I++)});
}
// Now instrument select instructions:
FuncInfo.SIVisitor.instrumentSelects(F, &I, NumCounters, FuncInfo.FuncNameVar,
FuncInfo.FunctionHash);
assert(I == NumCounters);
if (DisableValueProfiling)
return;
unsigned NumIndirectCallSites = 0;
for (auto &I : findIndirectCallSites(F)) {
CallSite CS(I);
Value *Callee = CS.getCalledValue();
DEBUG(dbgs() << "Instrument one indirect call: CallSite Index = "
<< NumIndirectCallSites << "\n");
IRBuilder<> Builder(I);
assert(Builder.GetInsertPoint() != I->getParent()->end() &&
"Cannot get the Instrumentation point");
Builder.CreateCall(
Intrinsic::getDeclaration(M, Intrinsic::instrprof_value_profile),
{llvm::ConstantExpr::getBitCast(FuncInfo.FuncNameVar, I8PtrTy),
Builder.getInt64(FuncInfo.FunctionHash),
Builder.CreatePtrToInt(Callee, Builder.getInt64Ty()),
Builder.getInt32(llvm::InstrProfValueKind::IPVK_IndirectCallTarget),
Builder.getInt32(NumIndirectCallSites++)});
}
NumOfPGOICall += NumIndirectCallSites;
}
// This class represents a CFG edge in profile use compilation.
struct PGOUseEdge : public PGOEdge {
bool CountValid;
uint64_t CountValue;
PGOUseEdge(const BasicBlock *Src, const BasicBlock *Dest, unsigned W = 1)
: PGOEdge(Src, Dest, W), CountValid(false), CountValue(0) {}
// Set edge count value
void setEdgeCount(uint64_t Value) {
CountValue = Value;
CountValid = true;
}
// Return the information string for this object.
const std::string infoString() const {
if (!CountValid)
return PGOEdge::infoString();
return (Twine(PGOEdge::infoString()) + " Count=" + Twine(CountValue))
.str();
}
};
typedef SmallVector<PGOUseEdge *, 2> DirectEdges;
// This class stores the auxiliary information for each BB.
struct UseBBInfo : public BBInfo {
uint64_t CountValue;
bool CountValid;
int32_t UnknownCountInEdge;
int32_t UnknownCountOutEdge;
DirectEdges InEdges;
DirectEdges OutEdges;
UseBBInfo(unsigned IX)
: BBInfo(IX), CountValue(0), CountValid(false), UnknownCountInEdge(0),
UnknownCountOutEdge(0) {}
UseBBInfo(unsigned IX, uint64_t C)
: BBInfo(IX), CountValue(C), CountValid(true), UnknownCountInEdge(0),
UnknownCountOutEdge(0) {}
// Set the profile count value for this BB.
void setBBInfoCount(uint64_t Value) {
CountValue = Value;
CountValid = true;
}
// Return the information string of this object.
const std::string infoString() const {
if (!CountValid)
return BBInfo::infoString();
return (Twine(BBInfo::infoString()) + " Count=" + Twine(CountValue)).str();
}
};
// Sum up the count values for all the edges.
static uint64_t sumEdgeCount(const ArrayRef<PGOUseEdge *> Edges) {
uint64_t Total = 0;
for (auto &E : Edges) {
if (E->Removed)
continue;
Total += E->CountValue;
}
return Total;
}
class PGOUseFunc {
public:
PGOUseFunc(Function &Func, Module *Modu,
std::unordered_multimap<Comdat *, GlobalValue *> &ComdatMembers,
BranchProbabilityInfo *BPI = nullptr,
BlockFrequencyInfo *BFI = nullptr)
: F(Func), M(Modu), FuncInfo(Func, ComdatMembers, false, BPI, BFI),
FreqAttr(FFA_Normal) {}
// Read counts for the instrumented BB from profile.
bool readCounters(IndexedInstrProfReader *PGOReader);
// Populate the counts for all BBs.
void populateCounters();
// Set the branch weights based on the count values.
void setBranchWeights();
// Annotate the indirect call sites.
void annotateIndirectCallSites();
// The hotness of the function from the profile count.
enum FuncFreqAttr { FFA_Normal, FFA_Cold, FFA_Hot };
// Return the function hotness from the profile.
FuncFreqAttr getFuncFreqAttr() const { return FreqAttr; }
// Return the function hash.
uint64_t getFuncHash() const { return FuncInfo.FunctionHash; }
// Return the profile record for this function;
InstrProfRecord &getProfileRecord() { return ProfileRecord; }
// Return the auxiliary BB information.
UseBBInfo &getBBInfo(const BasicBlock *BB) const {
return FuncInfo.getBBInfo(BB);
}
private:
Function &F;
Module *M;
// This member stores the shared information with class PGOGenFunc.
FuncPGOInstrumentation<PGOUseEdge, UseBBInfo> FuncInfo;
// The maximum count value in the profile. This is only used in PGO use
// compilation.
uint64_t ProgramMaxCount;
// ProfileRecord for this function.
InstrProfRecord ProfileRecord;
// Function hotness info derived from profile.
FuncFreqAttr FreqAttr;
// Find the Instrumented BB and set the value.
void setInstrumentedCounts(const std::vector<uint64_t> &CountFromProfile);
// Set the edge counter value for the unknown edge -- there should be only
// one unknown edge.
void setEdgeCount(DirectEdges &Edges, uint64_t Value);
// Return FuncName string;
const std::string getFuncName() const { return FuncInfo.FuncName; }
// Set the hot/cold inline hints based on the count values.
// FIXME: This function should be removed once the functionality in
// the inliner is implemented.
void markFunctionAttributes(uint64_t EntryCount, uint64_t MaxCount) {
if (ProgramMaxCount == 0)
return;
// Threshold of the hot functions.
const BranchProbability HotFunctionThreshold(1, 100);
// Threshold of the cold functions.
const BranchProbability ColdFunctionThreshold(2, 10000);
if (EntryCount >= HotFunctionThreshold.scale(ProgramMaxCount))
FreqAttr = FFA_Hot;
else if (MaxCount <= ColdFunctionThreshold.scale(ProgramMaxCount))
FreqAttr = FFA_Cold;
}
};
// Visit all the edges and assign the count value for the instrumented
// edges and the BB.
void PGOUseFunc::setInstrumentedCounts(
const std::vector<uint64_t> &CountFromProfile) {
assert(FuncInfo.getNumCounters() == CountFromProfile.size());
// Use a worklist as we will update the vector during the iteration.
std::vector<PGOUseEdge *> WorkList;
for (auto &E : FuncInfo.MST.AllEdges)
WorkList.push_back(E.get());
uint32_t I = 0;
for (auto &E : WorkList) {
BasicBlock *InstrBB = FuncInfo.getInstrBB(E);
if (!InstrBB)
continue;
uint64_t CountValue = CountFromProfile[I++];
if (!E->Removed) {
getBBInfo(InstrBB).setBBInfoCount(CountValue);
E->setEdgeCount(CountValue);
continue;
}
// Need to add two new edges.
BasicBlock *SrcBB = const_cast<BasicBlock *>(E->SrcBB);
BasicBlock *DestBB = const_cast<BasicBlock *>(E->DestBB);
// Add new edge of SrcBB->InstrBB.
PGOUseEdge &NewEdge = FuncInfo.MST.addEdge(SrcBB, InstrBB, 0);
NewEdge.setEdgeCount(CountValue);
// Add new edge of InstrBB->DestBB.
PGOUseEdge &NewEdge1 = FuncInfo.MST.addEdge(InstrBB, DestBB, 0);
NewEdge1.setEdgeCount(CountValue);
NewEdge1.InMST = true;
getBBInfo(InstrBB).setBBInfoCount(CountValue);
}
// Now annotate select instructions
FuncInfo.SIVisitor.annotateSelects(F, this, &I);
assert(I == CountFromProfile.size());
}
// Set the count value for the unknown edge. There should be one and only one
// unknown edge in Edges vector.
void PGOUseFunc::setEdgeCount(DirectEdges &Edges, uint64_t Value) {
for (auto &E : Edges) {
if (E->CountValid)
continue;
E->setEdgeCount(Value);
getBBInfo(E->SrcBB).UnknownCountOutEdge--;
getBBInfo(E->DestBB).UnknownCountInEdge--;
return;
}
llvm_unreachable("Cannot find the unknown count edge");
}
// Read the profile from ProfileFileName and assign the value to the
// instrumented BB and the edges. This function also updates ProgramMaxCount.
// Return true if the profile are successfully read, and false on errors.
bool PGOUseFunc::readCounters(IndexedInstrProfReader *PGOReader) {
auto &Ctx = M->getContext();
Expected<InstrProfRecord> Result =
PGOReader->getInstrProfRecord(FuncInfo.FuncName, FuncInfo.FunctionHash);
if (Error E = Result.takeError()) {
handleAllErrors(std::move(E), [&](const InstrProfError &IPE) {
auto Err = IPE.get();
bool SkipWarning = false;
if (Err == instrprof_error::unknown_function) {
NumOfPGOMissing++;
SkipWarning = !PGOWarnMissing;
} else if (Err == instrprof_error::hash_mismatch ||
Err == instrprof_error::malformed) {
NumOfPGOMismatch++;
SkipWarning = NoPGOWarnMismatch;
}
if (SkipWarning)
return;
std::string Msg = IPE.message() + std::string(" ") + F.getName().str();
Ctx.diagnose(
DiagnosticInfoPGOProfile(M->getName().data(), Msg, DS_Warning));
});
return false;
}
ProfileRecord = std::move(Result.get());
std::vector<uint64_t> &CountFromProfile = ProfileRecord.Counts;
NumOfPGOFunc++;
DEBUG(dbgs() << CountFromProfile.size() << " counts\n");
uint64_t ValueSum = 0;
for (unsigned I = 0, S = CountFromProfile.size(); I < S; I++) {
DEBUG(dbgs() << " " << I << ": " << CountFromProfile[I] << "\n");
ValueSum += CountFromProfile[I];
}
DEBUG(dbgs() << "SUM = " << ValueSum << "\n");
getBBInfo(nullptr).UnknownCountOutEdge = 2;
getBBInfo(nullptr).UnknownCountInEdge = 2;
setInstrumentedCounts(CountFromProfile);
ProgramMaxCount = PGOReader->getMaximumFunctionCount();
return true;
}
// Populate the counters from instrumented BBs to all BBs.
// In the end of this operation, all BBs should have a valid count value.
void PGOUseFunc::populateCounters() {
// First set up Count variable for all BBs.
for (auto &E : FuncInfo.MST.AllEdges) {
if (E->Removed)
continue;
const BasicBlock *SrcBB = E->SrcBB;
const BasicBlock *DestBB = E->DestBB;
UseBBInfo &SrcInfo = getBBInfo(SrcBB);
UseBBInfo &DestInfo = getBBInfo(DestBB);
SrcInfo.OutEdges.push_back(E.get());
DestInfo.InEdges.push_back(E.get());
SrcInfo.UnknownCountOutEdge++;
DestInfo.UnknownCountInEdge++;
if (!E->CountValid)
continue;
DestInfo.UnknownCountInEdge--;
SrcInfo.UnknownCountOutEdge--;
}
bool Changes = true;
unsigned NumPasses = 0;
while (Changes) {
NumPasses++;
Changes = false;
// For efficient traversal, it's better to start from the end as most
// of the instrumented edges are at the end.
for (auto &BB : reverse(F)) {
UseBBInfo &Count = getBBInfo(&BB);
if (!Count.CountValid) {
if (Count.UnknownCountOutEdge == 0) {
Count.CountValue = sumEdgeCount(Count.OutEdges);
Count.CountValid = true;
Changes = true;
} else if (Count.UnknownCountInEdge == 0) {
Count.CountValue = sumEdgeCount(Count.InEdges);
Count.CountValid = true;
Changes = true;
}
}
if (Count.CountValid) {
if (Count.UnknownCountOutEdge == 1) {
uint64_t Total = Count.CountValue - sumEdgeCount(Count.OutEdges);
setEdgeCount(Count.OutEdges, Total);
Changes = true;
}
if (Count.UnknownCountInEdge == 1) {
uint64_t Total = Count.CountValue - sumEdgeCount(Count.InEdges);
setEdgeCount(Count.InEdges, Total);
Changes = true;
}
}
}
}
DEBUG(dbgs() << "Populate counts in " << NumPasses << " passes.\n");
#ifndef NDEBUG
// Assert every BB has a valid counter.
for (auto &BB : F)
assert(getBBInfo(&BB).CountValid && "BB count is not valid");
#endif
uint64_t FuncEntryCount = getBBInfo(&*F.begin()).CountValue;
F.setEntryCount(FuncEntryCount);
uint64_t FuncMaxCount = FuncEntryCount;
for (auto &BB : F)
FuncMaxCount = std::max(FuncMaxCount, getBBInfo(&BB).CountValue);
markFunctionAttributes(FuncEntryCount, FuncMaxCount);
DEBUG(FuncInfo.dumpInfo("after reading profile."));
}
static void setProfMetadata(Module *M, Instruction *TI,
ArrayRef<uint64_t> EdgeCounts, uint64_t MaxCount) {
MDBuilder MDB(M->getContext());
assert(MaxCount > 0 && "Bad max count");
uint64_t Scale = calculateCountScale(MaxCount);
SmallVector<unsigned, 4> Weights;
for (const auto &ECI : EdgeCounts)
Weights.push_back(scaleBranchCount(ECI, Scale));
DEBUG(dbgs() << "Weight is: ";
for (const auto &W : Weights) { dbgs() << W << " "; }
dbgs() << "\n";);
TI->setMetadata(llvm::LLVMContext::MD_prof, MDB.createBranchWeights(Weights));
}
// Assign the scaled count values to the BB with multiple out edges.
void PGOUseFunc::setBranchWeights() {
// Generate MD_prof metadata for every branch instruction.
DEBUG(dbgs() << "\nSetting branch weights.\n");
for (auto &BB : F) {
TerminatorInst *TI = BB.getTerminator();
if (TI->getNumSuccessors() < 2)
continue;
if (!isa<BranchInst>(TI) && !isa<SwitchInst>(TI))
continue;
if (getBBInfo(&BB).CountValue == 0)
continue;
// We have a non-zero Branch BB.
const UseBBInfo &BBCountInfo = getBBInfo(&BB);
unsigned Size = BBCountInfo.OutEdges.size();
SmallVector<uint64_t, 2> EdgeCounts(Size, 0);
uint64_t MaxCount = 0;
for (unsigned s = 0; s < Size; s++) {
const PGOUseEdge *E = BBCountInfo.OutEdges[s];
const BasicBlock *SrcBB = E->SrcBB;
const BasicBlock *DestBB = E->DestBB;
if (DestBB == nullptr)
continue;
unsigned SuccNum = GetSuccessorNumber(SrcBB, DestBB);
uint64_t EdgeCount = E->CountValue;
if (EdgeCount > MaxCount)
MaxCount = EdgeCount;
EdgeCounts[SuccNum] = EdgeCount;
}
setProfMetadata(M, TI, EdgeCounts, MaxCount);
}
}
void SelectInstVisitor::instrumentOneSelectInst(SelectInst &SI) {
Module *M = F.getParent();
IRBuilder<> Builder(&SI);
Type *Int64Ty = Builder.getInt64Ty();
Type *I8PtrTy = Builder.getInt8PtrTy();
auto *Step = Builder.CreateZExt(SI.getCondition(), Int64Ty);
Builder.CreateCall(
Intrinsic::getDeclaration(M, Intrinsic::instrprof_increment_step),
{llvm::ConstantExpr::getBitCast(FuncNameVar, I8PtrTy),
Builder.getInt64(FuncHash),
Builder.getInt32(TotalNumCtrs), Builder.getInt32(*CurCtrIdx), Step});
++(*CurCtrIdx);
}
void SelectInstVisitor::annotateOneSelectInst(SelectInst &SI) {
std::vector<uint64_t> &CountFromProfile = UseFunc->getProfileRecord().Counts;
assert(*CurCtrIdx < CountFromProfile.size() &&
"Out of bound access of counters");
uint64_t SCounts[2];
SCounts[0] = CountFromProfile[*CurCtrIdx]; // True count
++(*CurCtrIdx);
uint64_t TotalCount = UseFunc->getBBInfo(SI.getParent()).CountValue;
// False Count
SCounts[1] = (TotalCount > SCounts[0] ? TotalCount - SCounts[0] : 0);
uint64_t MaxCount = std::max(SCounts[0], SCounts[1]);
setProfMetadata(F.getParent(), &SI, SCounts, MaxCount);
}
void SelectInstVisitor::visitSelectInst(SelectInst &SI) {
if (!PGOInstrSelect)
return;
// FIXME: do not handle this yet.
if (SI.getCondition()->getType()->isVectorTy())
return;
NSIs++;
switch (Mode) {
case VM_counting:
return;
case VM_instrument:
instrumentOneSelectInst(SI);
break;
case VM_annotate:
annotateOneSelectInst(SI);
break;
default:
assert(false && "Unknown visiting mode");
break;
}
}
// Traverse all the indirect callsites and annotate the instructions.
void PGOUseFunc::annotateIndirectCallSites() {
if (DisableValueProfiling)
return;
// Create the PGOFuncName meta data.
createPGOFuncNameMetadata(F, FuncInfo.FuncName);
unsigned IndirectCallSiteIndex = 0;
auto IndirectCallSites = findIndirectCallSites(F);
unsigned NumValueSites =
ProfileRecord.getNumValueSites(IPVK_IndirectCallTarget);
if (NumValueSites != IndirectCallSites.size()) {
std::string Msg =
std::string("Inconsistent number of indirect call sites: ") +
F.getName().str();
auto &Ctx = M->getContext();
Ctx.diagnose(
DiagnosticInfoPGOProfile(M->getName().data(), Msg, DS_Warning));
return;
}
for (auto &I : IndirectCallSites) {
DEBUG(dbgs() << "Read one indirect call instrumentation: Index="
<< IndirectCallSiteIndex << " out of " << NumValueSites
<< "\n");
annotateValueSite(*M, *I, ProfileRecord, IPVK_IndirectCallTarget,
IndirectCallSiteIndex, MaxNumAnnotations);
IndirectCallSiteIndex++;
}
}
} // end anonymous namespace
// Create a COMDAT variable INSTR_PROF_RAW_VERSION_VAR to make the runtime
// aware this is an ir_level profile so it can set the version flag.
static void createIRLevelProfileFlagVariable(Module &M) {
Type *IntTy64 = Type::getInt64Ty(M.getContext());
uint64_t ProfileVersion = (INSTR_PROF_RAW_VERSION | VARIANT_MASK_IR_PROF);
auto IRLevelVersionVariable = new GlobalVariable(
M, IntTy64, true, GlobalVariable::ExternalLinkage,
Constant::getIntegerValue(IntTy64, APInt(64, ProfileVersion)),
INSTR_PROF_QUOTE(INSTR_PROF_RAW_VERSION_VAR));
IRLevelVersionVariable->setVisibility(GlobalValue::DefaultVisibility);
Triple TT(M.getTargetTriple());
if (!TT.supportsCOMDAT())
IRLevelVersionVariable->setLinkage(GlobalValue::WeakAnyLinkage);
else
IRLevelVersionVariable->setComdat(M.getOrInsertComdat(
StringRef(INSTR_PROF_QUOTE(INSTR_PROF_RAW_VERSION_VAR))));
}
// Collect the set of members for each Comdat in module M and store
// in ComdatMembers.
static void collectComdatMembers(
Module &M,
std::unordered_multimap<Comdat *, GlobalValue *> &ComdatMembers) {
if (!DoComdatRenaming)
return;
for (Function &F : M)
if (Comdat *C = F.getComdat())
ComdatMembers.insert(std::make_pair(C, &F));
for (GlobalVariable &GV : M.globals())
if (Comdat *C = GV.getComdat())
ComdatMembers.insert(std::make_pair(C, &GV));
for (GlobalAlias &GA : M.aliases())
if (Comdat *C = GA.getComdat())
ComdatMembers.insert(std::make_pair(C, &GA));
}
static bool InstrumentAllFunctions(
Module &M, function_ref<BranchProbabilityInfo *(Function &)> LookupBPI,
function_ref<BlockFrequencyInfo *(Function &)> LookupBFI) {
createIRLevelProfileFlagVariable(M);
std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
collectComdatMembers(M, ComdatMembers);
for (auto &F : M) {
if (F.isDeclaration())
continue;
auto *BPI = LookupBPI(F);
auto *BFI = LookupBFI(F);
instrumentOneFunc(F, &M, BPI, BFI, ComdatMembers);
}
return true;
}
bool PGOInstrumentationGenLegacyPass::runOnModule(Module &M) {
if (skipModule(M))
return false;
auto LookupBPI = [this](Function &F) {
return &this->getAnalysis<BranchProbabilityInfoWrapperPass>(F).getBPI();
};
auto LookupBFI = [this](Function &F) {
return &this->getAnalysis<BlockFrequencyInfoWrapperPass>(F).getBFI();
};
return InstrumentAllFunctions(M, LookupBPI, LookupBFI);
}
PreservedAnalyses PGOInstrumentationGen::run(Module &M,
ModuleAnalysisManager &AM) {
auto &FAM = AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
auto LookupBPI = [&FAM](Function &F) {
return &FAM.getResult<BranchProbabilityAnalysis>(F);
};
auto LookupBFI = [&FAM](Function &F) {
return &FAM.getResult<BlockFrequencyAnalysis>(F);
};
if (!InstrumentAllFunctions(M, LookupBPI, LookupBFI))
return PreservedAnalyses::all();
return PreservedAnalyses::none();
}
static bool annotateAllFunctions(
Module &M, StringRef ProfileFileName,
function_ref<BranchProbabilityInfo *(Function &)> LookupBPI,
function_ref<BlockFrequencyInfo *(Function &)> LookupBFI) {
DEBUG(dbgs() << "Read in profile counters: ");
auto &Ctx = M.getContext();
// Read the counter array from file.
auto ReaderOrErr = IndexedInstrProfReader::create(ProfileFileName);
if (Error E = ReaderOrErr.takeError()) {
handleAllErrors(std::move(E), [&](const ErrorInfoBase &EI) {
Ctx.diagnose(
DiagnosticInfoPGOProfile(ProfileFileName.data(), EI.message()));
});
return false;
}
std::unique_ptr<IndexedInstrProfReader> PGOReader =
std::move(ReaderOrErr.get());
if (!PGOReader) {
Ctx.diagnose(DiagnosticInfoPGOProfile(ProfileFileName.data(),
StringRef("Cannot get PGOReader")));
return false;
}
// TODO: might need to change the warning once the clang option is finalized.
if (!PGOReader->isIRLevelProfile()) {
Ctx.diagnose(DiagnosticInfoPGOProfile(
ProfileFileName.data(), "Not an IR level instrumentation profile"));
return false;
}
std::unordered_multimap<Comdat *, GlobalValue *> ComdatMembers;
collectComdatMembers(M, ComdatMembers);
std::vector<Function *> HotFunctions;
std::vector<Function *> ColdFunctions;
for (auto &F : M) {
if (F.isDeclaration())
continue;
auto *BPI = LookupBPI(F);
auto *BFI = LookupBFI(F);
PGOUseFunc Func(F, &M, ComdatMembers, BPI, BFI);
if (!Func.readCounters(PGOReader.get()))
continue;
Func.populateCounters();
Func.setBranchWeights();
Func.annotateIndirectCallSites();
PGOUseFunc::FuncFreqAttr FreqAttr = Func.getFuncFreqAttr();
if (FreqAttr == PGOUseFunc::FFA_Cold)
ColdFunctions.push_back(&F);
else if (FreqAttr == PGOUseFunc::FFA_Hot)
HotFunctions.push_back(&F);
}
M.setProfileSummary(PGOReader->getSummary().getMD(M.getContext()));
// Set function hotness attribute from the profile.
// We have to apply these attributes at the end because their presence
// can affect the BranchProbabilityInfo of any callers, resulting in an
// inconsistent MST between prof-gen and prof-use.
for (auto &F : HotFunctions) {
F->addFnAttr(llvm::Attribute::InlineHint);
DEBUG(dbgs() << "Set inline attribute to function: " << F->getName()
<< "\n");
}
for (auto &F : ColdFunctions) {
F->addFnAttr(llvm::Attribute::Cold);
DEBUG(dbgs() << "Set cold attribute to function: " << F->getName() << "\n");
}
return true;
}
PGOInstrumentationUse::PGOInstrumentationUse(std::string Filename)
: ProfileFileName(std::move(Filename)) {
if (!PGOTestProfileFile.empty())
ProfileFileName = PGOTestProfileFile;
}
PreservedAnalyses PGOInstrumentationUse::run(Module &M,
ModuleAnalysisManager &AM) {
auto &FAM = AM.getResult<FunctionAnalysisManagerModuleProxy>(M).getManager();
auto LookupBPI = [&FAM](Function &F) {
return &FAM.getResult<BranchProbabilityAnalysis>(F);
};
auto LookupBFI = [&FAM](Function &F) {
return &FAM.getResult<BlockFrequencyAnalysis>(F);
};
if (!annotateAllFunctions(M, ProfileFileName, LookupBPI, LookupBFI))
return PreservedAnalyses::all();
return PreservedAnalyses::none();
}
bool PGOInstrumentationUseLegacyPass::runOnModule(Module &M) {
if (skipModule(M))
return false;
auto LookupBPI = [this](Function &F) {
return &this->getAnalysis<BranchProbabilityInfoWrapperPass>(F).getBPI();
};
auto LookupBFI = [this](Function &F) {
return &this->getAnalysis<BlockFrequencyInfoWrapperPass>(F).getBFI();
};
return annotateAllFunctions(M, ProfileFileName, LookupBPI, LookupBFI);
}
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