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//===- BPSectionOrderer.cpp -----------------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "BPSectionOrderer.h"
#include "InputSection.h"
#include "Relocations.h"
#include "Symbols.h"
#include "lld/Common/BPSectionOrdererBase.inc"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/StableHashing.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/xxhash.h"
#define DEBUG_TYPE "bp-section-orderer"
using namespace llvm;
using namespace lld::macho;
namespace {
struct BPOrdererMachO;
}
template <> struct lld::BPOrdererTraits<struct BPOrdererMachO> {
using Section = macho::InputSection;
using Symbol = macho::Symbol;
};
namespace {
struct BPOrdererMachO : lld::BPOrderer<BPOrdererMachO> {
static uint64_t getSize(const Section &sec) { return sec.getSize(); }
static bool isCodeSection(const Section &sec) {
return macho::isCodeSection(&sec);
}
static SmallVector<Symbol *, 0> getSymbols(const Section &sec) {
SmallVector<Symbol *, 0> symbols;
for (auto *sym : sec.symbols)
if (auto *d = llvm::dyn_cast_or_null<Defined>(sym))
symbols.emplace_back(d);
return symbols;
}
// Linkage names can be prefixed with "_" or "l_" on Mach-O. See
// Mangler::getNameWithPrefix() for details.
std::optional<StringRef> static getResolvedLinkageName(llvm::StringRef name) {
if (name.consume_front("_") || name.consume_front("l_"))
return name;
return {};
}
static void
getSectionHashes(const Section &sec, llvm::SmallVectorImpl<uint64_t> &hashes,
const llvm::DenseMap<const void *, uint64_t> §ionToIdx) {
constexpr unsigned windowSize = 4;
// Calculate content hashes: k-mers and the last k-1 bytes.
ArrayRef<uint8_t> data = sec.data;
if (data.size() >= windowSize)
for (size_t i = 0; i <= data.size() - windowSize; ++i)
hashes.push_back(llvm::support::endian::read32le(data.data() + i));
for (uint8_t byte : data.take_back(windowSize - 1))
hashes.push_back(byte);
// Calculate relocation hashes
for (const auto &r : sec.relocs) {
if (r.length == 0 || r.referent.isNull() || r.offset >= data.size())
continue;
uint64_t relocHash = getRelocHash(r, sectionToIdx);
uint32_t start = (r.offset < windowSize) ? 0 : r.offset - windowSize + 1;
for (uint32_t i = start; i < r.offset + r.length; i++) {
auto window = data.drop_front(i).take_front(windowSize);
hashes.push_back(xxh3_64bits(window) ^ relocHash);
}
}
llvm::sort(hashes);
hashes.erase(std::unique(hashes.begin(), hashes.end()), hashes.end());
}
static llvm::StringRef getSymName(const Symbol &sym) { return sym.getName(); }
static uint64_t getSymValue(const Symbol &sym) {
if (auto *d = dyn_cast<Defined>(&sym))
return d->value;
return 0;
}
static uint64_t getSymSize(const Symbol &sym) {
if (auto *d = dyn_cast<Defined>(&sym))
return d->size;
return 0;
}
private:
static uint64_t
getRelocHash(const Reloc &reloc,
const llvm::DenseMap<const void *, uint64_t> §ionToIdx) {
auto *isec = reloc.getReferentInputSection();
std::optional<uint64_t> sectionIdx;
if (auto it = sectionToIdx.find(isec); it != sectionToIdx.end())
sectionIdx = it->second;
uint64_t kind = -1, value = 0;
if (isec)
kind = uint64_t(isec->kind());
if (auto *sym = reloc.referent.dyn_cast<Symbol *>()) {
kind = (kind << 8) | uint8_t(sym->kind());
if (auto *d = llvm::dyn_cast<Defined>(sym))
value = d->value;
}
return llvm::stable_hash_combine(kind, sectionIdx.value_or(0), value,
reloc.addend);
}
};
} // namespace
DenseMap<const InputSection *, int> lld::macho::runBalancedPartitioning(
StringRef profilePath, bool forFunctionCompression, bool forDataCompression,
bool compressionSortStartupFunctions, bool verbose) {
// Collect candidate sections and associated symbols.
SmallVector<InputSection *> sections;
DenseMap<CachedHashStringRef, DenseSet<unsigned>> rootSymbolToSectionIdxs;
for (const auto *file : inputFiles) {
for (auto *sec : file->sections) {
for (auto &subsec : sec->subsections) {
auto *isec = subsec.isec;
if (!isec || isec->data.empty())
continue;
size_t idx = sections.size();
sections.emplace_back(isec);
for (auto *sym : BPOrdererMachO::getSymbols(*isec)) {
auto rootName = getRootSymbol(sym->getName());
rootSymbolToSectionIdxs[CachedHashStringRef(rootName)].insert(idx);
if (auto linkageName =
BPOrdererMachO::getResolvedLinkageName(rootName))
rootSymbolToSectionIdxs[CachedHashStringRef(*linkageName)].insert(
idx);
}
}
}
}
return BPOrdererMachO::computeOrder(profilePath, forFunctionCompression,
forDataCompression,
compressionSortStartupFunctions, verbose,
sections, rootSymbolToSectionIdxs);
}
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