[lld] [lld][ELF] Extend profile guided function ordering to ELF binaries (PR #117514)

[Fangrui Song via llvm-commits]

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@@ -0,0 +1,140 @@
+//===- BPSectionOrderer.h ---------------------------------------*- C++ -*-===//
+//
+// 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 uses Balanced Partitioning to order sections to improve startup
+/// time and compressed size.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLD_ELF_BPSECTION_ORDERER_H
+#define LLD_ELF_BPSECTION_ORDERER_H
+
+#include "InputFiles.h"
+#include "InputSection.h"
+#include "Relocations.h"
+#include "Symbols.h"
+#include "lld/Common/SectionOrderer.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/STLFunctionalExtras.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/BinaryFormat/ELF.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/xxhash.h"
+
+namespace lld::elf {
+
+class InputSection;
+
+class ELFSymbol : public BPSymbol {
+  const Symbol *sym;
+
+public:
+  explicit ELFSymbol(const Symbol *s) : sym(s) {}
+
+  llvm::StringRef getName() const override { return sym->getName(); }
+
+  BPSymbol *asDefinedSymbol() override {
+    if (auto *d = llvm::dyn_cast<Defined>(sym))
+      return this;
+    return nullptr;
+  }
+
+  uint64_t getValue() const override {
+    if (auto *d = llvm::dyn_cast<Defined>(sym))
+      return d->value;
+    return 0;
+  }
+
+  uint64_t getSize() const override {
+    if (auto *d = llvm::dyn_cast<Defined>(sym))
+      return d->size;
+    return 0;
+  }
+
+  InputSectionBase *getInputSection() const {
+    if (auto *d = llvm::dyn_cast<Defined>(sym))
+      return llvm::dyn_cast_or_null<InputSectionBase>(d->section);
+    return nullptr;
+  }
+
+  const Symbol *getSymbol() const { return sym; }
+};
+
+class ELFSection : public BPSectionBase {
+  const InputSectionBase *isec;
+  ELFSymbol *symbol;
+  std::vector<BPSymbol *> symbols;
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MaskRay wrote:

`SmallVector<, 0>` to make the struct smaller

https://github.com/llvm/llvm-project/pull/117514