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llvm-project/clang/lib/CodeGen/CodeGenPGO.cpp

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//===--- CodeGenPGO.cpp - PGO Instrumentation for LLVM CodeGen --*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Instrumentation-based profile-guided optimization
//
//===----------------------------------------------------------------------===//
#include "CodeGenPGO.h"
#include "CodeGenFunction.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/StmtVisitor.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/ProfileData/InstrProfReader.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MD5.h"
using namespace clang;
using namespace CodeGen;
void CodeGenPGO::setFuncName(llvm::Function *Fn) {
RawFuncName = Fn->getName();
// Function names may be prefixed with a binary '1' to indicate
// that the backend should not modify the symbols due to any platform
// naming convention. Do not include that '1' in the PGO profile name.
if (RawFuncName[0] == '\1')
RawFuncName = RawFuncName.substr(1);
if (!Fn->hasLocalLinkage()) {
PrefixedFuncName.reset(new std::string(RawFuncName));
return;
}
// For local symbols, prepend the main file name to distinguish them.
// Do not include the full path in the file name since there's no guarantee
// that it will stay the same, e.g., if the files are checked out from
// version control in different locations.
PrefixedFuncName.reset(new std::string(CGM.getCodeGenOpts().MainFileName));
if (PrefixedFuncName->empty())
PrefixedFuncName->assign("<unknown>");
PrefixedFuncName->append(":");
PrefixedFuncName->append(RawFuncName);
}
static llvm::Function *getRegisterFunc(CodeGenModule &CGM) {
return CGM.getModule().getFunction("__llvm_profile_register_functions");
}
static llvm::BasicBlock *getOrInsertRegisterBB(CodeGenModule &CGM) {
// Don't do this for Darwin. compiler-rt uses linker magic.
if (CGM.getTarget().getTriple().isOSDarwin())
return nullptr;
// Only need to insert this once per module.
if (llvm::Function *RegisterF = getRegisterFunc(CGM))
return &RegisterF->getEntryBlock();
// Construct the function.
auto *VoidTy = llvm::Type::getVoidTy(CGM.getLLVMContext());
auto *RegisterFTy = llvm::FunctionType::get(VoidTy, false);
auto *RegisterF = llvm::Function::Create(RegisterFTy,
llvm::GlobalValue::InternalLinkage,
"__llvm_profile_register_functions",
&CGM.getModule());
RegisterF->setUnnamedAddr(true);
if (CGM.getCodeGenOpts().DisableRedZone)
RegisterF->addFnAttr(llvm::Attribute::NoRedZone);
// Construct and return the entry block.
auto *BB = llvm::BasicBlock::Create(CGM.getLLVMContext(), "", RegisterF);
CGBuilderTy Builder(BB);
Builder.CreateRetVoid();
return BB;
}
static llvm::Constant *getOrInsertRuntimeRegister(CodeGenModule &CGM) {
auto *VoidTy = llvm::Type::getVoidTy(CGM.getLLVMContext());
auto *VoidPtrTy = llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
auto *RuntimeRegisterTy = llvm::FunctionType::get(VoidTy, VoidPtrTy, false);
return CGM.getModule().getOrInsertFunction("__llvm_profile_register_function",
RuntimeRegisterTy);
}
static bool isMachO(const CodeGenModule &CGM) {
return CGM.getTarget().getTriple().isOSBinFormatMachO();
}
static StringRef getCountersSection(const CodeGenModule &CGM) {
return isMachO(CGM) ? "__DATA,__llvm_prf_cnts" : "__llvm_prf_cnts";
}
static StringRef getNameSection(const CodeGenModule &CGM) {
return isMachO(CGM) ? "__DATA,__llvm_prf_names" : "__llvm_prf_names";
}
static StringRef getDataSection(const CodeGenModule &CGM) {
return isMachO(CGM) ? "__DATA,__llvm_prf_data" : "__llvm_prf_data";
}
llvm::GlobalVariable *CodeGenPGO::buildDataVar() {
// Create name variable.
llvm::LLVMContext &Ctx = CGM.getLLVMContext();
auto *VarName = llvm::ConstantDataArray::getString(Ctx, getFuncName(),
false);
auto *Name = new llvm::GlobalVariable(CGM.getModule(), VarName->getType(),
true, VarLinkage, VarName,
getFuncVarName("name"));
Name->setSection(getNameSection(CGM));
Name->setAlignment(1);
// Create data variable.
auto *Int32Ty = llvm::Type::getInt32Ty(Ctx);
auto *Int64Ty = llvm::Type::getInt64Ty(Ctx);
auto *Int8PtrTy = llvm::Type::getInt8PtrTy(Ctx);
auto *Int64PtrTy = llvm::Type::getInt64PtrTy(Ctx);
llvm::Type *DataTypes[] = {
Int32Ty, Int32Ty, Int64Ty, Int8PtrTy, Int64PtrTy
};
auto *DataTy = llvm::StructType::get(Ctx, makeArrayRef(DataTypes));
llvm::Constant *DataVals[] = {
llvm::ConstantInt::get(Int32Ty, getFuncName().size()),
llvm::ConstantInt::get(Int32Ty, NumRegionCounters),
llvm::ConstantInt::get(Int64Ty, FunctionHash),
llvm::ConstantExpr::getBitCast(Name, Int8PtrTy),
llvm::ConstantExpr::getBitCast(RegionCounters, Int64PtrTy)
};
auto *Data =
new llvm::GlobalVariable(CGM.getModule(), DataTy, true, VarLinkage,
llvm::ConstantStruct::get(DataTy, DataVals),
getFuncVarName("data"));
// All the data should be packed into an array in its own section.
Data->setSection(getDataSection(CGM));
Data->setAlignment(8);
// Hide all these symbols so that we correctly get a copy for each
// executable. The profile format expects names and counters to be
// contiguous, so references into shared objects would be invalid.
if (!llvm::GlobalValue::isLocalLinkage(VarLinkage)) {
Name->setVisibility(llvm::GlobalValue::HiddenVisibility);
Data->setVisibility(llvm::GlobalValue::HiddenVisibility);
RegionCounters->setVisibility(llvm::GlobalValue::HiddenVisibility);
}
// Make sure the data doesn't get deleted.
CGM.addUsedGlobal(Data);
return Data;
}
void CodeGenPGO::emitInstrumentationData() {
if (!RegionCounters)
return;
// Build the data.
auto *Data = buildDataVar();
// Register the data.
auto *RegisterBB = getOrInsertRegisterBB(CGM);
if (!RegisterBB)
return;
CGBuilderTy Builder(RegisterBB->getTerminator());
auto *VoidPtrTy = llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
Builder.CreateCall(getOrInsertRuntimeRegister(CGM),
Builder.CreateBitCast(Data, VoidPtrTy));
}
llvm::Function *CodeGenPGO::emitInitialization(CodeGenModule &CGM) {
if (!CGM.getCodeGenOpts().ProfileInstrGenerate)
return nullptr;
assert(CGM.getModule().getFunction("__llvm_profile_init") == nullptr &&
"profile initialization already emitted");
// Get the function to call at initialization.
llvm::Constant *RegisterF = getRegisterFunc(CGM);
if (!RegisterF)
return nullptr;
// Create the initialization function.
auto *VoidTy = llvm::Type::getVoidTy(CGM.getLLVMContext());
auto *F = llvm::Function::Create(llvm::FunctionType::get(VoidTy, false),
llvm::GlobalValue::InternalLinkage,
"__llvm_profile_init", &CGM.getModule());
F->setUnnamedAddr(true);
F->addFnAttr(llvm::Attribute::NoInline);
if (CGM.getCodeGenOpts().DisableRedZone)
F->addFnAttr(llvm::Attribute::NoRedZone);
// Add the basic block and the necessary calls.
CGBuilderTy Builder(llvm::BasicBlock::Create(CGM.getLLVMContext(), "", F));
Builder.CreateCall(RegisterF);
Builder.CreateRetVoid();
return F;
}
namespace {
/// \brief Stable hasher for PGO region counters.
///
/// PGOHash produces a stable hash of a given function's control flow.
///
/// Changing the output of this hash will invalidate all previously generated
/// profiles -- i.e., don't do it.
///
/// \note When this hash does eventually change (years?), we still need to
/// support old hashes. We'll need to pull in the version number from the
/// profile data format and use the matching hash function.
class PGOHash {
uint64_t Working;
unsigned Count;
llvm::MD5 MD5;
static const int NumBitsPerType = 6;
static const unsigned NumTypesPerWord = sizeof(uint64_t) * 8 / NumBitsPerType;
static const unsigned TooBig = 1u << NumBitsPerType;
public:
/// \brief Hash values for AST nodes.
///
/// Distinct values for AST nodes that have region counters attached.
///
/// These values must be stable. All new members must be added at the end,
/// and no members should be removed. Changing the enumeration value for an
/// AST node will affect the hash of every function that contains that node.
enum HashType : unsigned char {
None = 0,
LabelStmt = 1,
WhileStmt,
DoStmt,
ForStmt,
CXXForRangeStmt,
ObjCForCollectionStmt,
SwitchStmt,
CaseStmt,
DefaultStmt,
IfStmt,
CXXTryStmt,
CXXCatchStmt,
ConditionalOperator,
BinaryOperatorLAnd,
BinaryOperatorLOr,
BinaryConditionalOperator,
// Keep this last. It's for the static assert that follows.
LastHashType
};
static_assert(LastHashType <= TooBig, "Too many types in HashType");
// TODO: When this format changes, take in a version number here, and use the
// old hash calculation for file formats that used the old hash.
PGOHash() : Working(0), Count(0) {}
void combine(HashType Type);
uint64_t finalize();
};
const int PGOHash::NumBitsPerType;
const unsigned PGOHash::NumTypesPerWord;
const unsigned PGOHash::TooBig;
/// A RecursiveASTVisitor that fills a map of statements to PGO counters.
struct MapRegionCounters : public RecursiveASTVisitor<MapRegionCounters> {
/// The next counter value to assign.
unsigned NextCounter;
/// The function hash.
PGOHash Hash;
/// The map of statements to counters.
llvm::DenseMap<const Stmt *, unsigned> &CounterMap;
MapRegionCounters(llvm::DenseMap<const Stmt *, unsigned> &CounterMap)
: NextCounter(0), CounterMap(CounterMap) {}
// Blocks and lambdas are handled as separate functions, so we need not
// traverse them in the parent context.
bool TraverseBlockExpr(BlockExpr *BE) { return true; }
bool TraverseLambdaBody(LambdaExpr *LE) { return true; }
bool TraverseCapturedStmt(CapturedStmt *CS) { return true; }
bool VisitDecl(const Decl *D) {
switch (D->getKind()) {
default:
break;
case Decl::Function:
case Decl::CXXMethod:
case Decl::CXXConstructor:
case Decl::CXXDestructor:
case Decl::CXXConversion:
case Decl::ObjCMethod:
case Decl::Block:
case Decl::Captured:
CounterMap[D->getBody()] = NextCounter++;
break;
}
return true;
}
bool VisitStmt(const Stmt *S) {
auto Type = getHashType(S);
if (Type == PGOHash::None)
return true;
CounterMap[S] = NextCounter++;
Hash.combine(Type);
return true;
}
PGOHash::HashType getHashType(const Stmt *S) {
switch (S->getStmtClass()) {
default:
break;
case Stmt::LabelStmtClass:
return PGOHash::LabelStmt;
case Stmt::WhileStmtClass:
return PGOHash::WhileStmt;
case Stmt::DoStmtClass:
return PGOHash::DoStmt;
case Stmt::ForStmtClass:
return PGOHash::ForStmt;
case Stmt::CXXForRangeStmtClass:
return PGOHash::CXXForRangeStmt;
case Stmt::ObjCForCollectionStmtClass:
return PGOHash::ObjCForCollectionStmt;
case Stmt::SwitchStmtClass:
return PGOHash::SwitchStmt;
case Stmt::CaseStmtClass:
return PGOHash::CaseStmt;
case Stmt::DefaultStmtClass:
return PGOHash::DefaultStmt;
case Stmt::IfStmtClass:
return PGOHash::IfStmt;
case Stmt::CXXTryStmtClass:
return PGOHash::CXXTryStmt;
case Stmt::CXXCatchStmtClass:
return PGOHash::CXXCatchStmt;
case Stmt::ConditionalOperatorClass:
return PGOHash::ConditionalOperator;
case Stmt::BinaryConditionalOperatorClass:
return PGOHash::BinaryConditionalOperator;
case Stmt::BinaryOperatorClass: {
const BinaryOperator *BO = cast<BinaryOperator>(S);
if (BO->getOpcode() == BO_LAnd)
return PGOHash::BinaryOperatorLAnd;
if (BO->getOpcode() == BO_LOr)
return PGOHash::BinaryOperatorLOr;
break;
}
}
return PGOHash::None;
}
};
/// A StmtVisitor that propagates the raw counts through the AST and
/// records the count at statements where the value may change.
struct ComputeRegionCounts : public ConstStmtVisitor<ComputeRegionCounts> {
/// PGO state.
CodeGenPGO &PGO;
/// A flag that is set when the current count should be recorded on the
/// next statement, such as at the exit of a loop.
bool RecordNextStmtCount;
/// The map of statements to count values.
llvm::DenseMap<const Stmt *, uint64_t> &CountMap;
/// BreakContinueStack - Keep counts of breaks and continues inside loops.
struct BreakContinue {
uint64_t BreakCount;
uint64_t ContinueCount;
BreakContinue() : BreakCount(0), ContinueCount(0) {}
};
SmallVector<BreakContinue, 8> BreakContinueStack;
ComputeRegionCounts(llvm::DenseMap<const Stmt *, uint64_t> &CountMap,
CodeGenPGO &PGO)
: PGO(PGO), RecordNextStmtCount(false), CountMap(CountMap) {}
void RecordStmtCount(const Stmt *S) {
if (RecordNextStmtCount) {
CountMap[S] = PGO.getCurrentRegionCount();
RecordNextStmtCount = false;
}
}
void VisitStmt(const Stmt *S) {
RecordStmtCount(S);
for (Stmt::const_child_range I = S->children(); I; ++I) {
if (*I)
this->Visit(*I);
}
}
void VisitFunctionDecl(const FunctionDecl *D) {
// Counter tracks entry to the function body.
RegionCounter Cnt(PGO, D->getBody());
Cnt.beginRegion();
CountMap[D->getBody()] = PGO.getCurrentRegionCount();
Visit(D->getBody());
}
// Skip lambda expressions. We visit these as FunctionDecls when we're
// generating them and aren't interested in the body when generating a
// parent context.
void VisitLambdaExpr(const LambdaExpr *LE) {}
void VisitCapturedDecl(const CapturedDecl *D) {
// Counter tracks entry to the capture body.
RegionCounter Cnt(PGO, D->getBody());
Cnt.beginRegion();
CountMap[D->getBody()] = PGO.getCurrentRegionCount();
Visit(D->getBody());
}
void VisitObjCMethodDecl(const ObjCMethodDecl *D) {
// Counter tracks entry to the method body.
RegionCounter Cnt(PGO, D->getBody());
Cnt.beginRegion();
CountMap[D->getBody()] = PGO.getCurrentRegionCount();
Visit(D->getBody());
}
void VisitBlockDecl(const BlockDecl *D) {
// Counter tracks entry to the block body.
RegionCounter Cnt(PGO, D->getBody());
Cnt.beginRegion();
CountMap[D->getBody()] = PGO.getCurrentRegionCount();
Visit(D->getBody());
}
void VisitReturnStmt(const ReturnStmt *S) {
RecordStmtCount(S);
if (S->getRetValue())
Visit(S->getRetValue());
PGO.setCurrentRegionUnreachable();
RecordNextStmtCount = true;
}
void VisitGotoStmt(const GotoStmt *S) {
RecordStmtCount(S);
PGO.setCurrentRegionUnreachable();
RecordNextStmtCount = true;
}
void VisitLabelStmt(const LabelStmt *S) {
RecordNextStmtCount = false;
// Counter tracks the block following the label.
RegionCounter Cnt(PGO, S);
Cnt.beginRegion();
CountMap[S] = PGO.getCurrentRegionCount();
Visit(S->getSubStmt());
}
void VisitBreakStmt(const BreakStmt *S) {
RecordStmtCount(S);
assert(!BreakContinueStack.empty() && "break not in a loop or switch!");
BreakContinueStack.back().BreakCount += PGO.getCurrentRegionCount();
PGO.setCurrentRegionUnreachable();
RecordNextStmtCount = true;
}
void VisitContinueStmt(const ContinueStmt *S) {
RecordStmtCount(S);
assert(!BreakContinueStack.empty() && "continue stmt not in a loop!");
BreakContinueStack.back().ContinueCount += PGO.getCurrentRegionCount();
PGO.setCurrentRegionUnreachable();
RecordNextStmtCount = true;
}
void VisitWhileStmt(const WhileStmt *S) {
RecordStmtCount(S);
// Counter tracks the body of the loop.
RegionCounter Cnt(PGO, S);
BreakContinueStack.push_back(BreakContinue());
// Visit the body region first so the break/continue adjustments can be
// included when visiting the condition.
Cnt.beginRegion();
CountMap[S->getBody()] = PGO.getCurrentRegionCount();
Visit(S->getBody());
Cnt.adjustForControlFlow();
// ...then go back and propagate counts through the condition. The count
// at the start of the condition is the sum of the incoming edges,
// the backedge from the end of the loop body, and the edges from
// continue statements.
BreakContinue BC = BreakContinueStack.pop_back_val();
Cnt.setCurrentRegionCount(Cnt.getParentCount() +
Cnt.getAdjustedCount() + BC.ContinueCount);
CountMap[S->getCond()] = PGO.getCurrentRegionCount();
Visit(S->getCond());
Cnt.adjustForControlFlow();
Cnt.applyAdjustmentsToRegion(BC.BreakCount + BC.ContinueCount);
RecordNextStmtCount = true;
}
void VisitDoStmt(const DoStmt *S) {
RecordStmtCount(S);
// Counter tracks the body of the loop.
RegionCounter Cnt(PGO, S);
BreakContinueStack.push_back(BreakContinue());
Cnt.beginRegion(/*AddIncomingFallThrough=*/true);
CountMap[S->getBody()] = PGO.getCurrentRegionCount();
Visit(S->getBody());
Cnt.adjustForControlFlow();
BreakContinue BC = BreakContinueStack.pop_back_val();
// The count at the start of the condition is equal to the count at the
// end of the body. The adjusted count does not include either the
// fall-through count coming into the loop or the continue count, so add
// both of those separately. This is coincidentally the same equation as
// with while loops but for different reasons.
Cnt.setCurrentRegionCount(Cnt.getParentCount() +
Cnt.getAdjustedCount() + BC.ContinueCount);
CountMap[S->getCond()] = PGO.getCurrentRegionCount();
Visit(S->getCond());
Cnt.adjustForControlFlow();
Cnt.applyAdjustmentsToRegion(BC.BreakCount + BC.ContinueCount);
RecordNextStmtCount = true;
}
void VisitForStmt(const ForStmt *S) {
RecordStmtCount(S);
if (S->getInit())
Visit(S->getInit());
// Counter tracks the body of the loop.
RegionCounter Cnt(PGO, S);
BreakContinueStack.push_back(BreakContinue());
// Visit the body region first. (This is basically the same as a while
// loop; see further comments in VisitWhileStmt.)
Cnt.beginRegion();
CountMap[S->getBody()] = PGO.getCurrentRegionCount();
Visit(S->getBody());
Cnt.adjustForControlFlow();
// The increment is essentially part of the body but it needs to include
// the count for all the continue statements.
if (S->getInc()) {
Cnt.setCurrentRegionCount(PGO.getCurrentRegionCount() +
BreakContinueStack.back().ContinueCount);
CountMap[S->getInc()] = PGO.getCurrentRegionCount();
Visit(S->getInc());
Cnt.adjustForControlFlow();
}
BreakContinue BC = BreakContinueStack.pop_back_val();
// ...then go back and propagate counts through the condition.
if (S->getCond()) {
Cnt.setCurrentRegionCount(Cnt.getParentCount() +
Cnt.getAdjustedCount() +
BC.ContinueCount);
CountMap[S->getCond()] = PGO.getCurrentRegionCount();
Visit(S->getCond());
Cnt.adjustForControlFlow();
}
Cnt.applyAdjustmentsToRegion(BC.BreakCount + BC.ContinueCount);
RecordNextStmtCount = true;
}
void VisitCXXForRangeStmt(const CXXForRangeStmt *S) {
RecordStmtCount(S);
Visit(S->getRangeStmt());
Visit(S->getBeginEndStmt());
// Counter tracks the body of the loop.
RegionCounter Cnt(PGO, S);
BreakContinueStack.push_back(BreakContinue());
// Visit the body region first. (This is basically the same as a while
// loop; see further comments in VisitWhileStmt.)
Cnt.beginRegion();
CountMap[S->getLoopVarStmt()] = PGO.getCurrentRegionCount();
Visit(S->getLoopVarStmt());
Visit(S->getBody());
Cnt.adjustForControlFlow();
// The increment is essentially part of the body but it needs to include
// the count for all the continue statements.
Cnt.setCurrentRegionCount(PGO.getCurrentRegionCount() +
BreakContinueStack.back().ContinueCount);
CountMap[S->getInc()] = PGO.getCurrentRegionCount();
Visit(S->getInc());
Cnt.adjustForControlFlow();
BreakContinue BC = BreakContinueStack.pop_back_val();
// ...then go back and propagate counts through the condition.
Cnt.setCurrentRegionCount(Cnt.getParentCount() +
Cnt.getAdjustedCount() +
BC.ContinueCount);
CountMap[S->getCond()] = PGO.getCurrentRegionCount();
Visit(S->getCond());
Cnt.adjustForControlFlow();
Cnt.applyAdjustmentsToRegion(BC.BreakCount + BC.ContinueCount);
RecordNextStmtCount = true;
}
void VisitObjCForCollectionStmt(const ObjCForCollectionStmt *S) {
RecordStmtCount(S);
Visit(S->getElement());
// Counter tracks the body of the loop.
RegionCounter Cnt(PGO, S);
BreakContinueStack.push_back(BreakContinue());
Cnt.beginRegion();
CountMap[S->getBody()] = PGO.getCurrentRegionCount();
Visit(S->getBody());
BreakContinue BC = BreakContinueStack.pop_back_val();
Cnt.adjustForControlFlow();
Cnt.applyAdjustmentsToRegion(BC.BreakCount + BC.ContinueCount);
RecordNextStmtCount = true;
}
void VisitSwitchStmt(const SwitchStmt *S) {
RecordStmtCount(S);
Visit(S->getCond());
PGO.setCurrentRegionUnreachable();
BreakContinueStack.push_back(BreakContinue());
Visit(S->getBody());
// If the switch is inside a loop, add the continue counts.
BreakContinue BC = BreakContinueStack.pop_back_val();
if (!BreakContinueStack.empty())
BreakContinueStack.back().ContinueCount += BC.ContinueCount;
// Counter tracks the exit block of the switch.
RegionCounter ExitCnt(PGO, S);
ExitCnt.beginRegion();
RecordNextStmtCount = true;
}
void VisitCaseStmt(const CaseStmt *S) {
RecordNextStmtCount = false;
// Counter for this particular case. This counts only jumps from the
// switch header and does not include fallthrough from the case before
// this one.
RegionCounter Cnt(PGO, S);
Cnt.beginRegion(/*AddIncomingFallThrough=*/true);
CountMap[S] = Cnt.getCount();
RecordNextStmtCount = true;
Visit(S->getSubStmt());
}
void VisitDefaultStmt(const DefaultStmt *S) {
RecordNextStmtCount = false;
// Counter for this default case. This does not include fallthrough from
// the previous case.
RegionCounter Cnt(PGO, S);
Cnt.beginRegion(/*AddIncomingFallThrough=*/true);
CountMap[S] = Cnt.getCount();
RecordNextStmtCount = true;
Visit(S->getSubStmt());
}
void VisitIfStmt(const IfStmt *S) {
RecordStmtCount(S);
// Counter tracks the "then" part of an if statement. The count for
// the "else" part, if it exists, will be calculated from this counter.
RegionCounter Cnt(PGO, S);
Visit(S->getCond());
Cnt.beginRegion();
CountMap[S->getThen()] = PGO.getCurrentRegionCount();
Visit(S->getThen());
Cnt.adjustForControlFlow();
if (S->getElse()) {
Cnt.beginElseRegion();
CountMap[S->getElse()] = PGO.getCurrentRegionCount();
Visit(S->getElse());
Cnt.adjustForControlFlow();
}
Cnt.applyAdjustmentsToRegion(0);
RecordNextStmtCount = true;
}
void VisitCXXTryStmt(const CXXTryStmt *S) {
RecordStmtCount(S);
Visit(S->getTryBlock());
for (unsigned I = 0, E = S->getNumHandlers(); I < E; ++I)
Visit(S->getHandler(I));
// Counter tracks the continuation block of the try statement.
RegionCounter Cnt(PGO, S);
Cnt.beginRegion();
RecordNextStmtCount = true;
}
void VisitCXXCatchStmt(const CXXCatchStmt *S) {
RecordNextStmtCount = false;
// Counter tracks the catch statement's handler block.
RegionCounter Cnt(PGO, S);
Cnt.beginRegion();
CountMap[S] = PGO.getCurrentRegionCount();
Visit(S->getHandlerBlock());
}
void VisitAbstractConditionalOperator(
const AbstractConditionalOperator *E) {
RecordStmtCount(E);
// Counter tracks the "true" part of a conditional operator. The
// count in the "false" part will be calculated from this counter.
RegionCounter Cnt(PGO, E);
Visit(E->getCond());
Cnt.beginRegion();
CountMap[E->getTrueExpr()] = PGO.getCurrentRegionCount();
Visit(E->getTrueExpr());
Cnt.adjustForControlFlow();
Cnt.beginElseRegion();
CountMap[E->getFalseExpr()] = PGO.getCurrentRegionCount();
Visit(E->getFalseExpr());
Cnt.adjustForControlFlow();
Cnt.applyAdjustmentsToRegion(0);
RecordNextStmtCount = true;
}
void VisitBinLAnd(const BinaryOperator *E) {
RecordStmtCount(E);
// Counter tracks the right hand side of a logical and operator.
RegionCounter Cnt(PGO, E);
Visit(E->getLHS());
Cnt.beginRegion();
CountMap[E->getRHS()] = PGO.getCurrentRegionCount();
Visit(E->getRHS());
Cnt.adjustForControlFlow();
Cnt.applyAdjustmentsToRegion(0);
RecordNextStmtCount = true;
}
void VisitBinLOr(const BinaryOperator *E) {
RecordStmtCount(E);
// Counter tracks the right hand side of a logical or operator.
RegionCounter Cnt(PGO, E);
Visit(E->getLHS());
Cnt.beginRegion();
CountMap[E->getRHS()] = PGO.getCurrentRegionCount();
Visit(E->getRHS());
Cnt.adjustForControlFlow();
Cnt.applyAdjustmentsToRegion(0);
RecordNextStmtCount = true;
}
};
}
void PGOHash::combine(HashType Type) {
// Check that we never combine 0 and only have six bits.
assert(Type && "Hash is invalid: unexpected type 0");
assert(unsigned(Type) < TooBig && "Hash is invalid: too many types");
// Pass through MD5 if enough work has built up.
if (Count && Count % NumTypesPerWord == 0) {
using namespace llvm::support;
uint64_t Swapped = endian::byte_swap<uint64_t, little>(Working);
MD5.update(llvm::makeArrayRef((uint8_t *)&Swapped, sizeof(Swapped)));
Working = 0;
}
// Accumulate the current type.
++Count;
Working = Working << NumBitsPerType | Type;
}
uint64_t PGOHash::finalize() {
// Use Working as the hash directly if we never used MD5.
if (Count <= NumTypesPerWord)
// No need to byte swap here, since none of the math was endian-dependent.
// This number will be byte-swapped as required on endianness transitions,
// so we will see the same value on the other side.
return Working;
// Check for remaining work in Working.
if (Working)
MD5.update(Working);
// Finalize the MD5 and return the hash.
llvm::MD5::MD5Result Result;
MD5.final(Result);
using namespace llvm::support;
return endian::read<uint64_t, little, unaligned>(Result);
}
static void emitRuntimeHook(CodeGenModule &CGM) {
const char *const RuntimeVarName = "__llvm_profile_runtime";
const char *const RuntimeUserName = "__llvm_profile_runtime_user";
if (CGM.getModule().getGlobalVariable(RuntimeVarName))
return;
// Declare the runtime hook.
llvm::LLVMContext &Ctx = CGM.getLLVMContext();
auto *Int32Ty = llvm::Type::getInt32Ty(Ctx);
auto *Var = new llvm::GlobalVariable(CGM.getModule(), Int32Ty, false,
llvm::GlobalValue::ExternalLinkage,
nullptr, RuntimeVarName);
// Make a function that uses it.
auto *User = llvm::Function::Create(llvm::FunctionType::get(Int32Ty, false),
llvm::GlobalValue::LinkOnceODRLinkage,
RuntimeUserName, &CGM.getModule());
User->addFnAttr(llvm::Attribute::NoInline);
if (CGM.getCodeGenOpts().DisableRedZone)
User->addFnAttr(llvm::Attribute::NoRedZone);
CGBuilderTy Builder(llvm::BasicBlock::Create(CGM.getLLVMContext(), "", User));
auto *Load = Builder.CreateLoad(Var);
Builder.CreateRet(Load);
// Create a use of the function. Now the definition of the runtime variable
// should get pulled in, along with any static initializears.
CGM.addUsedGlobal(User);
}
void CodeGenPGO::assignRegionCounters(const Decl *D, llvm::Function *Fn) {
bool InstrumentRegions = CGM.getCodeGenOpts().ProfileInstrGenerate;
llvm::IndexedInstrProfReader *PGOReader = CGM.getPGOReader();
if (!InstrumentRegions && !PGOReader)
return;
if (D->isImplicit())
return;
setFuncName(Fn);
// Set the linkage for variables based on the function linkage. Usually, we
// want to match it, but available_externally and extern_weak both have the
// wrong semantics.
VarLinkage = Fn->getLinkage();
switch (VarLinkage) {
case llvm::GlobalValue::ExternalWeakLinkage:
VarLinkage = llvm::GlobalValue::LinkOnceAnyLinkage;
break;
case llvm::GlobalValue::AvailableExternallyLinkage:
VarLinkage = llvm::GlobalValue::LinkOnceODRLinkage;
break;
default:
break;
}
mapRegionCounters(D);
if (InstrumentRegions) {
emitRuntimeHook(CGM);
emitCounterVariables();
}
if (PGOReader) {
SourceManager &SM = CGM.getContext().getSourceManager();
loadRegionCounts(PGOReader, SM.isInMainFile(D->getLocation()));
computeRegionCounts(D);
applyFunctionAttributes(PGOReader, Fn);
}
}
void CodeGenPGO::mapRegionCounters(const Decl *D) {
RegionCounterMap.reset(new llvm::DenseMap<const Stmt *, unsigned>);
MapRegionCounters Walker(*RegionCounterMap);
if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D))
Walker.TraverseDecl(const_cast<FunctionDecl *>(FD));
else if (const ObjCMethodDecl *MD = dyn_cast_or_null<ObjCMethodDecl>(D))
Walker.TraverseDecl(const_cast<ObjCMethodDecl *>(MD));
else if (const BlockDecl *BD = dyn_cast_or_null<BlockDecl>(D))
Walker.TraverseDecl(const_cast<BlockDecl *>(BD));
else if (const CapturedDecl *CD = dyn_cast_or_null<CapturedDecl>(D))
Walker.TraverseDecl(const_cast<CapturedDecl *>(CD));
assert(Walker.NextCounter > 0 && "no entry counter mapped for decl");
NumRegionCounters = Walker.NextCounter;
FunctionHash = Walker.Hash.finalize();
}
void CodeGenPGO::computeRegionCounts(const Decl *D) {
StmtCountMap.reset(new llvm::DenseMap<const Stmt *, uint64_t>);
ComputeRegionCounts Walker(*StmtCountMap, *this);
if (const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D))
Walker.VisitFunctionDecl(FD);
else if (const ObjCMethodDecl *MD = dyn_cast_or_null<ObjCMethodDecl>(D))
Walker.VisitObjCMethodDecl(MD);
else if (const BlockDecl *BD = dyn_cast_or_null<BlockDecl>(D))
Walker.VisitBlockDecl(BD);
else if (const CapturedDecl *CD = dyn_cast_or_null<CapturedDecl>(D))
Walker.VisitCapturedDecl(const_cast<CapturedDecl *>(CD));
}
void
CodeGenPGO::applyFunctionAttributes(llvm::IndexedInstrProfReader *PGOReader,
llvm::Function *Fn) {
if (!haveRegionCounts())
return;
uint64_t MaxFunctionCount = PGOReader->getMaximumFunctionCount();
uint64_t FunctionCount = getRegionCount(0);
if (FunctionCount >= (uint64_t)(0.3 * (double)MaxFunctionCount))
// Turn on InlineHint attribute for hot functions.
// FIXME: 30% is from preliminary tuning on SPEC, it may not be optimal.
Fn->addFnAttr(llvm::Attribute::InlineHint);
else if (FunctionCount <= (uint64_t)(0.01 * (double)MaxFunctionCount))
// Turn on Cold attribute for cold functions.
// FIXME: 1% is from preliminary tuning on SPEC, it may not be optimal.
Fn->addFnAttr(llvm::Attribute::Cold);
}
void CodeGenPGO::emitCounterVariables() {
llvm::LLVMContext &Ctx = CGM.getLLVMContext();
llvm::ArrayType *CounterTy = llvm::ArrayType::get(llvm::Type::getInt64Ty(Ctx),
NumRegionCounters);
RegionCounters =
new llvm::GlobalVariable(CGM.getModule(), CounterTy, false, VarLinkage,
llvm::Constant::getNullValue(CounterTy),
getFuncVarName("counters"));
RegionCounters->setAlignment(8);
RegionCounters->setSection(getCountersSection(CGM));
}
void CodeGenPGO::emitCounterIncrement(CGBuilderTy &Builder, unsigned Counter) {
if (!RegionCounters)
return;
llvm::Value *Addr =
Builder.CreateConstInBoundsGEP2_64(RegionCounters, 0, Counter);
llvm::Value *Count = Builder.CreateLoad(Addr, "pgocount");
Count = Builder.CreateAdd(Count, Builder.getInt64(1));
Builder.CreateStore(Count, Addr);
}
void CodeGenPGO::loadRegionCounts(llvm::IndexedInstrProfReader *PGOReader,
bool IsInMainFile) {
CGM.getPGOStats().addVisited(IsInMainFile);
RegionCounts.reset(new std::vector<uint64_t>);
uint64_t Hash;
if (PGOReader->getFunctionCounts(getFuncName(), Hash, *RegionCounts)) {
CGM.getPGOStats().addMissing(IsInMainFile);
RegionCounts.reset();
} else if (Hash != FunctionHash ||
RegionCounts->size() != NumRegionCounters) {
CGM.getPGOStats().addMismatched(IsInMainFile);
RegionCounts.reset();
}
}
void CodeGenPGO::destroyRegionCounters() {
RegionCounterMap.reset();
StmtCountMap.reset();
RegionCounts.reset();
RegionCounters = nullptr;
}
/// \brief Calculate what to divide by to scale weights.
///
/// Given the maximum weight, calculate a divisor that will scale all the
/// weights to strictly less than UINT32_MAX.
static uint64_t calculateWeightScale(uint64_t MaxWeight) {
return MaxWeight < UINT32_MAX ? 1 : MaxWeight / UINT32_MAX + 1;
}
/// \brief Scale an individual branch weight (and add 1).
///
/// Scale a 64-bit weight down to 32-bits using \c Scale.
///
/// According to Laplace's Rule of Succession, it is better to compute the
/// weight based on the count plus 1, so universally add 1 to the value.
///
/// \pre \c Scale was calculated by \a calculateWeightScale() with a weight no
/// greater than \c Weight.
static uint32_t scaleBranchWeight(uint64_t Weight, uint64_t Scale) {
assert(Scale && "scale by 0?");
uint64_t Scaled = Weight / Scale + 1;
assert(Scaled <= UINT32_MAX && "overflow 32-bits");
return Scaled;
}
llvm::MDNode *CodeGenPGO::createBranchWeights(uint64_t TrueCount,
uint64_t FalseCount) {
// Check for empty weights.
if (!TrueCount && !FalseCount)
return nullptr;
// Calculate how to scale down to 32-bits.
uint64_t Scale = calculateWeightScale(std::max(TrueCount, FalseCount));
llvm::MDBuilder MDHelper(CGM.getLLVMContext());
return MDHelper.createBranchWeights(scaleBranchWeight(TrueCount, Scale),
scaleBranchWeight(FalseCount, Scale));
}
llvm::MDNode *CodeGenPGO::createBranchWeights(ArrayRef<uint64_t> Weights) {
// We need at least two elements to create meaningful weights.
if (Weights.size() < 2)
return nullptr;
// Check for empty weights.
uint64_t MaxWeight = *std::max_element(Weights.begin(), Weights.end());
if (MaxWeight == 0)
return nullptr;
// Calculate how to scale down to 32-bits.
uint64_t Scale = calculateWeightScale(MaxWeight);
SmallVector<uint32_t, 16> ScaledWeights;
ScaledWeights.reserve(Weights.size());
for (uint64_t W : Weights)
ScaledWeights.push_back(scaleBranchWeight(W, Scale));
llvm::MDBuilder MDHelper(CGM.getLLVMContext());
return MDHelper.createBranchWeights(ScaledWeights);
}
llvm::MDNode *CodeGenPGO::createLoopWeights(const Stmt *Cond,
RegionCounter &Cnt) {
if (!haveRegionCounts())
return nullptr;
uint64_t LoopCount = Cnt.getCount();
uint64_t CondCount = 0;
bool Found = getStmtCount(Cond, CondCount);
assert(Found && "missing expected loop condition count");
(void)Found;
if (CondCount == 0)
return nullptr;
return createBranchWeights(LoopCount,
std::max(CondCount, LoopCount) - LoopCount);
}
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