shylie/llvm-project
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
llvm-project/llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp
Rong Xu 33308f92eb [PGO] Fix select instruction annotation 
Summary:
Select instruction annotation in IR PGO uses the edge count to infer the
branch count. It's currently placed in setInstrumentedCounts() where
no all the BB counts have been computed. This leads to wrong branch weights.
Move the annotation after all BB counts are populated.

Reviewers: davidxl

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D25961

llvm-svn: 285128
2016-10-25 21:47:24 +00:00

1229 lines
44 KiB
C++
Raw Blame History

//===-- 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());
}
StringRef 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());
}
StringRef 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:
std::vector<Instruction *> IndirectCallSites;
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();
IndirectCallSites = findIndirectCallSites(Func);
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)IndirectCallSites.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 OrigName = F.getName().str();
std::string NewFuncName =
Twine(F.getName() + "." + Twine(FunctionHash)).str();
F.setName(Twine(NewFuncName));
GlobalAlias::create(GlobalValue::WeakAnyLinkage, OrigName, &F);
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);
std::string OrigGAName = GA->getName().str();
GA->setName(Twine(GA->getName() + "." + Twine(FunctionHash)));
GlobalAlias::create(GlobalValue::WeakAnyLinkage, OrigGAName, GA);
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 : FuncInfo.IndirectCallSites) {
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),
CountPosition(0), ProfileCountSize(0), 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;
// Position of counter that remains to be read.
uint32_t CountPosition;
// Total size of the profile count for this function.
uint32_t ProfileCountSize;
// 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);
}
ProfileCountSize = CountFromProfile.size();
CountPosition = I;
}
// 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);
// Now annotate select instructions
FuncInfo.SIVisitor.annotateSelects(F, this, &CountPosition);
assert(CountPosition == ProfileCountSize);
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]);
if (MaxCount)
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);
return;
case VM_annotate:
annotateOneSelectInst(SI);
return;
}
llvm_unreachable("Unknown visiting mode");
}
// 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 = FuncInfo.IndirectCallSites;
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);
}
Reference in New Issue View Git Blame Copy Permalink