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//===- BlockFrequencyInfo.cpp - Block Frequency Analysis ------------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Loops should be simplified before this analysis.
#include "llvm/Analysis/BlockFrequencyInfo.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/iterator.h"
#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/IR/CFG.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/PassManager.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/GraphWriter.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <string>
using namespace llvm;
#define DEBUG_TYPE "block-freq"
static cl::opt<GVDAGType> ViewBlockFreqPropagationDAG(
"view-block-freq-propagation-dags", cl::Hidden,
cl::desc("Pop up a window to show a dag displaying how block "
"frequencies propagation through the CFG."),
cl::values(clEnumValN(GVDT_None, "none", "do not display graphs."),
clEnumValN(GVDT_Fraction, "fraction",
"display a graph using the "
"fractional block frequency representation."),
clEnumValN(GVDT_Integer, "integer",
"display a graph using the raw "
"integer fractional block frequency representation."),
clEnumValN(GVDT_Count, "count", "display a graph using the real "
"profile count if available.")));
namespace llvm {
ViewBlockFreqFuncName("view-bfi-func-name", cl::Hidden,
cl::desc("The option to specify "
"the name of the function "
"whose CFG will be displayed."));
ViewHotFreqPercent("view-hot-freq-percent", cl::init(10), cl::Hidden,
cl::desc("An integer in percent used to specify "
"the hot blocks/edges to be displayed "
"in red: a block or edge whose frequency "
"is no less than the max frequency of the "
"function multiplied by this percent."));
// Command line option to turn on CFG dot or text dump after profile annotation.
cl::opt<PGOViewCountsType> PGOViewCounts(
"pgo-view-counts", cl::Hidden,
cl::desc("A boolean option to show CFG dag or text with "
"block profile counts and branch probabilities "
"right after PGO profile annotation step. The "
"profile counts are computed using branch "
"probabilities from the runtime profile data and "
"block frequency propagation algorithm. To view "
"the raw counts from the profile, use option "
"-pgo-view-raw-counts instead. To limit graph "
"display to only one function, use filtering option "
cl::values(clEnumValN(PGOVCT_None, "none", "do not show."),
clEnumValN(PGOVCT_Graph, "graph", "show a graph."),
clEnumValN(PGOVCT_Text, "text", "show in text.")));
static cl::opt<bool> PrintBlockFreq(
"print-bfi", cl::init(false), cl::Hidden,
cl::desc("Print the block frequency info."));
cl::opt<std::string> PrintBlockFreqFuncName(
"print-bfi-func-name", cl::Hidden,
cl::desc("The option to specify the name of the function "
"whose block frequency info is printed."));
} // namespace llvm
namespace llvm {
static GVDAGType getGVDT() {
if (PGOViewCounts == PGOVCT_Graph)
return GVDT_Count;
return ViewBlockFreqPropagationDAG;
template <>
struct GraphTraits<BlockFrequencyInfo *> {
using NodeRef = const BasicBlock *;
using ChildIteratorType = const_succ_iterator;
using nodes_iterator = pointer_iterator<Function::const_iterator>;
static NodeRef getEntryNode(const BlockFrequencyInfo *G) {
return &G->getFunction()->front();
static ChildIteratorType child_begin(const NodeRef N) {
return succ_begin(N);
static ChildIteratorType child_end(const NodeRef N) { return succ_end(N); }
static nodes_iterator nodes_begin(const BlockFrequencyInfo *G) {
return nodes_iterator(G->getFunction()->begin());
static nodes_iterator nodes_end(const BlockFrequencyInfo *G) {
return nodes_iterator(G->getFunction()->end());
using BFIDOTGTraitsBase =
BFIDOTGraphTraitsBase<BlockFrequencyInfo, BranchProbabilityInfo>;
template <>
struct DOTGraphTraits<BlockFrequencyInfo *> : public BFIDOTGTraitsBase {
explicit DOTGraphTraits(bool isSimple = false)
: BFIDOTGTraitsBase(isSimple) {}
std::string getNodeLabel(const BasicBlock *Node,
const BlockFrequencyInfo *Graph) {
return BFIDOTGTraitsBase::getNodeLabel(Node, Graph, getGVDT());
std::string getNodeAttributes(const BasicBlock *Node,
const BlockFrequencyInfo *Graph) {
return BFIDOTGTraitsBase::getNodeAttributes(Node, Graph,
std::string getEdgeAttributes(const BasicBlock *Node, EdgeIter EI,
const BlockFrequencyInfo *BFI) {
return BFIDOTGTraitsBase::getEdgeAttributes(Node, EI, BFI, BFI->getBPI(),
} // end namespace llvm
BlockFrequencyInfo::BlockFrequencyInfo() = default;
BlockFrequencyInfo::BlockFrequencyInfo(const Function &F,
const BranchProbabilityInfo &BPI,
const LoopInfo &LI) {
calculate(F, BPI, LI);
BlockFrequencyInfo::BlockFrequencyInfo(BlockFrequencyInfo &&Arg)
: BFI(std::move(Arg.BFI)) {}
BlockFrequencyInfo &BlockFrequencyInfo::operator=(BlockFrequencyInfo &&RHS) {
BFI = std::move(RHS.BFI);
return *this;
// Explicitly define the default constructor otherwise it would be implicitly
// defined at the first ODR-use which is the BFI member in the
// LazyBlockFrequencyInfo header. The dtor needs the BlockFrequencyInfoImpl
// template instantiated which is not available in the header.
BlockFrequencyInfo::~BlockFrequencyInfo() = default;
bool BlockFrequencyInfo::invalidate(Function &F, const PreservedAnalyses &PA,
FunctionAnalysisManager::Invalidator &) {
// Check whether the analysis, all analyses on functions, or the function's
// CFG have been preserved.
auto PAC = PA.getChecker<BlockFrequencyAnalysis>();
return !(PAC.preserved() || PAC.preservedSet<AllAnalysesOn<Function>>() ||
void BlockFrequencyInfo::calculate(const Function &F,
const BranchProbabilityInfo &BPI,
const LoopInfo &LI) {
if (!BFI)
BFI.reset(new ImplType);
BFI->calculate(F, BPI, LI);
if (ViewBlockFreqPropagationDAG != GVDT_None &&
(ViewBlockFreqFuncName.empty() ||
F.getName().equals(ViewBlockFreqFuncName))) {
if (PrintBlockFreq &&
(PrintBlockFreqFuncName.empty() ||
F.getName().equals(PrintBlockFreqFuncName))) {
BlockFrequency BlockFrequencyInfo::getBlockFreq(const BasicBlock *BB) const {
return BFI ? BFI->getBlockFreq(BB) : 0;
BlockFrequencyInfo::getBlockProfileCount(const BasicBlock *BB,
bool AllowSynthetic) const {
if (!BFI)
return None;
return BFI->getBlockProfileCount(*getFunction(), BB, AllowSynthetic);
BlockFrequencyInfo::getProfileCountFromFreq(uint64_t Freq) const {
if (!BFI)
return None;
return BFI->getProfileCountFromFreq(*getFunction(), Freq);
bool BlockFrequencyInfo::isIrrLoopHeader(const BasicBlock *BB) {
assert(BFI && "Expected analysis to be available");
return BFI->isIrrLoopHeader(BB);
void BlockFrequencyInfo::setBlockFreq(const BasicBlock *BB, uint64_t Freq) {
assert(BFI && "Expected analysis to be available");
BFI->setBlockFreq(BB, Freq);
void BlockFrequencyInfo::setBlockFreqAndScale(
const BasicBlock *ReferenceBB, uint64_t Freq,
SmallPtrSetImpl<BasicBlock *> &BlocksToScale) {
assert(BFI && "Expected analysis to be available");
// Use 128 bits APInt to avoid overflow.
APInt NewFreq(128, Freq);
APInt OldFreq(128, BFI->getBlockFreq(ReferenceBB).getFrequency());
APInt BBFreq(128, 0);
for (auto *BB : BlocksToScale) {
BBFreq = BFI->getBlockFreq(BB).getFrequency();
// Multiply first by NewFreq and then divide by OldFreq
// to minimize loss of precision.
BBFreq *= NewFreq;
// udiv is an expensive operation in the general case. If this ends up being
// a hot spot, one of the options proposed in
// could be used to avoid this.
BBFreq = BBFreq.udiv(OldFreq);
BFI->setBlockFreq(BB, BBFreq.getLimitedValue());
BFI->setBlockFreq(ReferenceBB, Freq);
/// Pop up a ghostview window with the current block frequency propagation
/// rendered using dot.
void BlockFrequencyInfo::view(StringRef title) const {
ViewGraph(const_cast<BlockFrequencyInfo *>(this), title);
const Function *BlockFrequencyInfo::getFunction() const {
return BFI ? BFI->getFunction() : nullptr;
const BranchProbabilityInfo *BlockFrequencyInfo::getBPI() const {
return BFI ? &BFI->getBPI() : nullptr;
raw_ostream &BlockFrequencyInfo::
printBlockFreq(raw_ostream &OS, const BlockFrequency Freq) const {
return BFI ? BFI->printBlockFreq(OS, Freq) : OS;
raw_ostream &
BlockFrequencyInfo::printBlockFreq(raw_ostream &OS,
const BasicBlock *BB) const {
return BFI ? BFI->printBlockFreq(OS, BB) : OS;
uint64_t BlockFrequencyInfo::getEntryFreq() const {
return BFI ? BFI->getEntryFreq() : 0;
void BlockFrequencyInfo::releaseMemory() { BFI.reset(); }
void BlockFrequencyInfo::print(raw_ostream &OS) const {
if (BFI)
void BlockFrequencyInfo::verifyMatch(BlockFrequencyInfo &Other) const {
if (BFI)
INITIALIZE_PASS_BEGIN(BlockFrequencyInfoWrapperPass, "block-freq",
"Block Frequency Analysis", true, true)
INITIALIZE_PASS_END(BlockFrequencyInfoWrapperPass, "block-freq",
"Block Frequency Analysis", true, true)
char BlockFrequencyInfoWrapperPass::ID = 0;
: FunctionPass(ID) {
BlockFrequencyInfoWrapperPass::~BlockFrequencyInfoWrapperPass() = default;
void BlockFrequencyInfoWrapperPass::print(raw_ostream &OS,
const Module *) const {
void BlockFrequencyInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
void BlockFrequencyInfoWrapperPass::releaseMemory() { BFI.releaseMemory(); }
bool BlockFrequencyInfoWrapperPass::runOnFunction(Function &F) {
BranchProbabilityInfo &BPI =
LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
BFI.calculate(F, BPI, LI);
return false;
AnalysisKey BlockFrequencyAnalysis::Key;
BlockFrequencyInfo BlockFrequencyAnalysis::run(Function &F,
FunctionAnalysisManager &AM) {
BlockFrequencyInfo BFI;
BFI.calculate(F, AM.getResult<BranchProbabilityAnalysis>(F),
return BFI;
BlockFrequencyPrinterPass::run(Function &F, FunctionAnalysisManager &AM) {
OS << "Printing analysis results of BFI for function "
<< "'" << F.getName() << "':"
<< "\n";
return PreservedAnalyses::all();