text: //===- OutputSections.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 "OutputSections.h"
  #include "InputChunks.h"
  #include "InputElement.h"
  #include "InputFiles.h"
  #include "OutputSegment.h"
  #include "WriterUtils.h"
  #include "lld/Common/ErrorHandler.h"
  #include "lld/Common/Memory.h"
  #include "llvm/ADT/Twine.h"
  #include "llvm/Support/LEB128.h"
  #include "llvm/Support/Parallel.h"
  
  #define DEBUG_TYPE "lld"
  
  using namespace llvm;
  using namespace llvm::wasm;
  
  namespace lld {
  
  // Returns a string, e.g. "FUNCTION(.text)".
  std::string toString(const wasm::OutputSection &sec) {
    if (!sec.name.empty())
      return (sec.getSectionName() + "(" + sec.name + ")").str();
    return std::string(sec.getSectionName());
  }
  
  namespace wasm {
  static StringRef sectionTypeToString(uint32_t sectionType) {
    switch (sectionType) {
    case WASM_SEC_CUSTOM:
      return "CUSTOM";
    case WASM_SEC_TYPE:
      return "TYPE";
    case WASM_SEC_IMPORT:
      return "IMPORT";
    case WASM_SEC_FUNCTION:
      return "FUNCTION";
    case WASM_SEC_TABLE:
      return "TABLE";
    case WASM_SEC_MEMORY:
      return "MEMORY";
    case WASM_SEC_GLOBAL:
      return "GLOBAL";
    case WASM_SEC_TAG:
      return "TAG";
    case WASM_SEC_EXPORT:
      return "EXPORT";
    case WASM_SEC_START:
      return "START";
    case WASM_SEC_ELEM:
      return "ELEM";
    case WASM_SEC_CODE:
      return "CODE";
    case WASM_SEC_DATA:
      return "DATA";
    case WASM_SEC_DATACOUNT:
      return "DATACOUNT";
    default:
      fatal("invalid section type");
    }
  }
  
  StringRef OutputSection::getSectionName() const {
    return sectionTypeToString(type);
  }
  
  void OutputSection::createHeader(size_t bodySize) {
    raw_string_ostream os(header);
    debugWrite(os.tell(), "section type [" + getSectionName() + "]");
    encodeULEB128(type, os);
    writeUleb128(os, bodySize, "section size");
    os.flush();
    log("createHeader: " + toString(*this) + " body=" + Twine(bodySize) +
        " total=" + Twine(getSize()));
  }
  
  void CodeSection::finalizeContents() {
    raw_string_ostream os(codeSectionHeader);
    writeUleb128(os, functions.size(), "function count");
    os.flush();
    bodySize = codeSectionHeader.size();
  
    for (InputFunction *func : functions) {
      func->outputSec = this;
      func->outSecOff = bodySize;
      func->calculateSize();
      // All functions should have a non-empty body at this point
      assert(func->getSize());
      bodySize += func->getSize();
    }
  
    createHeader(bodySize);
  }
  
  void CodeSection::writeTo(uint8_t *buf) {
    log("writing " + toString(*this) + " offset=" + Twine(offset) +
        " size=" + Twine(getSize()));
    log(" headersize=" + Twine(header.size()));
    log(" codeheadersize=" + Twine(codeSectionHeader.size()));
    buf += offset;
  
    // Write section header
    memcpy(buf, header.data(), header.size());
    buf += header.size();
  
    // Write code section headers
    memcpy(buf, codeSectionHeader.data(), codeSectionHeader.size());
  
    // Write code section bodies
    for (const InputChunk *chunk : functions)
      chunk->writeTo(buf);
  }
  
  uint32_t CodeSection::getNumRelocations() const {
    uint32_t count = 0;
    for (const InputChunk *func : functions)
      count += func->getNumRelocations();
    return count;
  }
  
  void CodeSection::writeRelocations(raw_ostream &os) const {
    for (const InputChunk *c : functions)
      c->writeRelocations(os);
  }
  
  void DataSection::finalizeContents() {
    raw_string_ostream os(dataSectionHeader);
    unsigned segmentCount = std::count_if(
        segments.begin(), segments.end(),
        [](OutputSegment *segment) { return segment->requiredInBinary(); });
  #ifndef NDEBUG
    unsigned activeCount = std::count_if(
        segments.begin(), segments.end(), [](OutputSegment *segment) {
          return (segment->initFlags & WASM_DATA_SEGMENT_IS_PASSIVE) == 0;
        });
  #endif
  
    assert((config->sharedMemory || !config->isPic || config->extendedConst ||
            activeCount <= 1) &&
           "output segments should have been combined by now");
  
    writeUleb128(os, segmentCount, "data segment count");
    os.flush();
    bodySize = dataSectionHeader.size();
    bool is64 = config->is64.getValueOr(false);
  
    for (OutputSegment *segment : segments) {
      if (!segment->requiredInBinary())
        continue;
      raw_string_ostream os(segment->header);
      writeUleb128(os, segment->initFlags, "init flags");
      if (segment->initFlags & WASM_DATA_SEGMENT_HAS_MEMINDEX)
        writeUleb128(os, 0, "memory index");
      if ((segment->initFlags & WASM_DATA_SEGMENT_IS_PASSIVE) == 0) {
        if (config->isPic && config->extendedConst) {
          writeU8(os, WASM_OPCODE_GLOBAL_GET, "global get");
          writeUleb128(os, WasmSym::memoryBase->getGlobalIndex(),
                       "literal (global index)");
          if (segment->startVA) {
            writePtrConst(os, segment->startVA, is64, "offset");
            writeU8(os, is64 ? WASM_OPCODE_I64_ADD : WASM_OPCODE_I32_ADD, "add");
          }
          writeU8(os, WASM_OPCODE_END, "opcode:end");
        } else {
          WasmInitExpr initExpr;
          initExpr.Extended = false;
          if (config->isPic) {
            assert(segment->startVA == 0);
            initExpr.Inst.Opcode = WASM_OPCODE_GLOBAL_GET;
            initExpr.Inst.Value.Global = WasmSym::memoryBase->getGlobalIndex();
          } else {
            initExpr = intConst(segment->startVA, is64);
          }
          writeInitExpr(os, initExpr);
        }
      }
      writeUleb128(os, segment->size, "segment size");
      os.flush();
  
      segment->sectionOffset = bodySize;
      bodySize += segment->header.size() + segment->size;
      log("Data segment: size=" + Twine(segment->size) + ", startVA=" +
          Twine::utohexstr(segment->startVA) + ", name=" + segment->name);
  
      for (InputChunk *inputSeg : segment->inputSegments) {
        inputSeg->outputSec = this;
        inputSeg->outSecOff = segment->sectionOffset + segment->header.size() +
                              inputSeg->outputSegmentOffset;
      }
    }
  
    createHeader(bodySize);
  }
  
  void DataSection::writeTo(uint8_t *buf) {
    log("writing " + toString(*this) + " offset=" + Twine(offset) +
        " size=" + Twine(getSize()) + " body=" + Twine(bodySize));
    buf += offset;
  
    // Write section header
    memcpy(buf, header.data(), header.size());
    buf += header.size();
  
    // Write data section headers
    memcpy(buf, dataSectionHeader.data(), dataSectionHeader.size());
  
    for (const OutputSegment *segment : segments) {
      if (!segment->requiredInBinary())
        continue;
      // Write data segment header
      uint8_t *segStart = buf + segment->sectionOffset;
      memcpy(segStart, segment->header.data(), segment->header.size());
  
      // Write segment data payload
      for (const InputChunk *chunk : segment->inputSegments)
        chunk->writeTo(buf);
    }
  }
  
  uint32_t DataSection::getNumRelocations() const {
    uint32_t count = 0;
    for (const OutputSegment *seg : segments)
      for (const InputChunk *inputSeg : seg->inputSegments)
        count += inputSeg->getNumRelocations();
    return count;
  }
  
  void DataSection::writeRelocations(raw_ostream &os) const {
    for (const OutputSegment *seg : segments)
      for (const InputChunk *c : seg->inputSegments)
        c->writeRelocations(os);
  }
  
  bool DataSection::isNeeded() const {
    for (const OutputSegment *seg : segments)
      if (seg->requiredInBinary())
        return true;
    return false;
  }
  
  // Lots of duplication here with OutputSegment::finalizeInputSegments
  void CustomSection::finalizeInputSections() {
    SyntheticMergedChunk *mergedSection = nullptr;
    std::vector<InputChunk *> newSections;
  
    for (InputChunk *s : inputSections) {
      s->outputSec = this;
      MergeInputChunk *ms = dyn_cast<MergeInputChunk>(s);
      if (!ms) {
        newSections.push_back(s);
        continue;
      }
  
      if (!mergedSection) {
        mergedSection =
            make<SyntheticMergedChunk>(name, 0, WASM_SEG_FLAG_STRINGS);
        newSections.push_back(mergedSection);
        mergedSection->outputSec = this;
      }
      mergedSection->addMergeChunk(ms);
    }
  
    if (!mergedSection)
      return;
  
    mergedSection->finalizeContents();
    inputSections = newSections;
  }
  
  void CustomSection::finalizeContents() {
    finalizeInputSections();
  
    raw_string_ostream os(nameData);
    encodeULEB128(name.size(), os);
    os << name;
    os.flush();
  
    for (InputChunk *section : inputSections) {
      assert(!section->discarded);
      section->outSecOff = payloadSize;
      payloadSize += section->getSize();
    }
  
    createHeader(payloadSize + nameData.size());
  }
  
  void CustomSection::writeTo(uint8_t *buf) {
    log("writing " + toString(*this) + " offset=" + Twine(offset) +
        " size=" + Twine(getSize()) + " chunks=" + Twine(inputSections.size()));
  
    assert(offset);
    buf += offset;
  
    // Write section header
    memcpy(buf, header.data(), header.size());
    buf += header.size();
    memcpy(buf, nameData.data(), nameData.size());
    buf += nameData.size();
  
    // Write custom sections payload
    for (const InputChunk *section : inputSections)
      section->writeTo(buf);
  }
  
  uint32_t CustomSection::getNumRelocations() const {
    uint32_t count = 0;
    for (const InputChunk *inputSect : inputSections)
      count += inputSect->getNumRelocations();
    return count;
  }
  
  void CustomSection::writeRelocations(raw_ostream &os) const {
    for (const InputChunk *s : inputSections)
      s->writeRelocations(os);
  }
  
  } // namespace wasm
  } // namespace lld
  