SplitFunctions.cpp | Explore in Territory

//===- bolt/Passes/SplitFunctions.cpp - Pass for splitting function code --===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the SplitFunctions pass.
//
//===----------------------------------------------------------------------===//

#include "bolt/Passes/SplitFunctions.h"
#include "bolt/Core/BinaryBasicBlock.h"
#include "bolt/Core/BinaryFunction.h"
#include "bolt/Core/FunctionLayout.h"
#include "bolt/Core/ParallelUtilities.h"
#include "bolt/Utils/CommandLineOpts.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/FormatVariadic.h"
#include <algorithm>
#include <iterator>
#include <memory>
#include <numeric>
#include <random>
#include <vector>

#define DEBUG_TYPE …

usingnamespacellvm;
usingnamespacebolt;

namespace {
class DeprecatedSplitFunctionOptionParser : public cl::parser<bool> { … };
} // namespace

namespace opts {

extern cl::OptionCategory BoltOptCategory;

extern cl::opt<bool> SplitEH;
extern cl::opt<unsigned> ExecutionCountThreshold;
extern cl::opt<uint32_t> RandomSeed;

static cl::opt<bool> AggressiveSplitting(
    "split-all-cold", cl::desc("outline as many cold basic blocks as possible"),
    cl::cat(BoltOptCategory));

static cl::opt<unsigned> SplitAlignThreshold(
    "split-align-threshold",
    cl::desc("when deciding to split a function, apply this alignment "
             "while doing the size comparison (see -split-threshold). "
             "Default value: 2."),
    cl::init(2),

    cl::Hidden, cl::cat(BoltOptCategory));

static cl::opt<bool, false, DeprecatedSplitFunctionOptionParser>
    SplitFunctions("split-functions",
                   cl::desc("split functions into fragments"),
                   cl::cat(BoltOptCategory));

static cl::opt<unsigned> SplitThreshold(
    "split-threshold",
    cl::desc("split function only if its main size is reduced by more than "
             "given amount of bytes. Default value: 0, i.e. split iff the "
             "size is reduced. Note that on some architectures the size can "
             "increase after splitting."),
    cl::init(0), cl::Hidden, cl::cat(BoltOptCategory));

static cl::opt<SplitFunctionsStrategy> SplitStrategy(
    "split-strategy", cl::init(SplitFunctionsStrategy::Profile2),
    cl::values(clEnumValN(SplitFunctionsStrategy::Profile2, "profile2",
                          "split each function into a hot and cold fragment "
                          "using profiling information")),
    cl::values(clEnumValN(SplitFunctionsStrategy::CDSplit, "cdsplit",
                          "split each function into a hot, warm, and cold "
                          "fragment using profiling information")),
    cl::values(clEnumValN(
        SplitFunctionsStrategy::Random2, "random2",
        "split each function into a hot and cold fragment at a randomly chosen "
        "split point (ignoring any available profiling information)")),
    cl::values(clEnumValN(
        SplitFunctionsStrategy::RandomN, "randomN",
        "split each function into N fragments at a randomly chosen split "
        "points (ignoring any available profiling information)")),
    cl::values(clEnumValN(
        SplitFunctionsStrategy::All, "all",
        "split all basic blocks of each function into fragments such that each "
        "fragment contains exactly a single basic block")),
    cl::desc("strategy used to partition blocks into fragments"),
    cl::cat(BoltOptCategory));

static cl::opt<double> CallScale(
    "call-scale",
    cl::desc("Call score scale coefficient (when --split-strategy=cdsplit)"),
    cl::init(0.95), cl::ReallyHidden, cl::cat(BoltOptCategory));

static cl::opt<double>
    CallPower("call-power",
              cl::desc("Call score power (when --split-strategy=cdsplit)"),
              cl::init(0.05), cl::ReallyHidden, cl::cat(BoltOptCategory));

static cl::opt<double>
    JumpPower("jump-power",
              cl::desc("Jump score power (when --split-strategy=cdsplit)"),
              cl::init(0.15), cl::ReallyHidden, cl::cat(BoltOptCategory));
} // namespace opts

namespace {
bool hasFullProfile(const BinaryFunction &BF) { … }

bool allBlocksCold(const BinaryFunction &BF) { … }

struct SplitProfile2 final : public SplitStrategy { … };

struct SplitCacheDirected final : public SplitStrategy { … };

struct SplitRandom2 final : public SplitStrategy { … };

struct SplitRandomN final : public SplitStrategy { … };

struct SplitAll final : public SplitStrategy { … };
} // namespace

namespace llvm {
namespace bolt {

bool SplitFunctions::shouldOptimize(const BinaryFunction &BF) const { … }

Error SplitFunctions::runOnFunctions(BinaryContext &BC) { … }

void SplitFunctions::splitFunction(BinaryFunction &BF, SplitStrategy &S) { … }

SplitFunctions::TrampolineSetType
SplitFunctions::createEHTrampolines(BinaryFunction &BF) const { … }

SplitFunctions::BasicBlockOrderType SplitFunctions::mergeEHTrampolines(
    BinaryFunction &BF, SplitFunctions::BasicBlockOrderType &Layout,
    const SplitFunctions::TrampolineSetType &Trampolines) const { … }

} // namespace bolt
} // namespace llvm
llvm/bolt/lib/Passes/SplitFunctions.cpp
