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/*
* Copyright 2019 WebAssembly Community Group participants
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "wasm-debug.h"
#include "wasm.h"
#ifdef BUILD_LLVM_DWARF
#include "llvm/ObjectYAML/DWARFEmitter.h"
#include "llvm/ObjectYAML/DWARFYAML.h"
#include "llvm/include/llvm/DebugInfo/DWARFContext.h"
std::error_code dwarf2yaml(llvm::DWARFContext& DCtx, llvm::DWARFYAML::Data& Y);
#endif
namespace wasm {
namespace Debug {
bool isDWARFSection(Name name) { return name.startsWith(".debug_"); }
bool hasDWARFSections(const Module& wasm) {
for (auto& section : wasm.userSections) {
if (isDWARFSection(section.name)) {
return true;
}
}
return false;
}
#ifdef BUILD_LLVM_DWARF
struct BinaryenDWARFInfo {
llvm::StringMap<std::unique_ptr<llvm::MemoryBuffer>> sections;
std::unique_ptr<llvm::DWARFContext> context;
BinaryenDWARFInfo(const Module& wasm) {
// Get debug sections from the wasm.
for (auto& section : wasm.userSections) {
if (Name(section.name).startsWith(".debug_")) {
// TODO: efficiency
sections[section.name.substr(1)] = llvm::MemoryBuffer::getMemBufferCopy(
llvm::StringRef(section.data.data(), section.data.size()));
}
}
// Parse debug sections.
uint8_t addrSize = 4;
context = llvm::DWARFContext::create(sections, addrSize);
}
};
void dumpDWARF(const Module& wasm) {
BinaryenDWARFInfo info(wasm);
std::cout << "DWARF debug info\n";
std::cout << "================\n\n";
for (auto& section : wasm.userSections) {
if (Name(section.name).startsWith(".debug_")) {
std::cout << "Contains section " << section.name << " ("
<< section.data.size() << " bytes)\n";
}
}
llvm::DIDumpOptions options;
options.Verbose = true;
info.context->dump(llvm::outs(), options);
}
//
// Big picture: We use a DWARFContext to read data, then DWARFYAML support
// code to write it. That is not the main LLVM Dwarf code used for writing
// object files, but it avoids us create a "fake" MC layer, and provides a
// simple way to write out the debug info. Likely the level of info represented
// in the DWARFYAML::Data object is sufficient for Binaryen's needs, but if not,
// we may need a different approach.
//
// In more detail:
//
// 1. Binary sections => DWARFContext:
//
// llvm::DWARFContext::create(sections..)
//
// 2. DWARFContext => DWARFYAML::Data
//
// std::error_code dwarf2yaml(DWARFContext &DCtx, DWARFYAML::Data &Y) {
//
// 3. DWARFYAML::Data => binary sections
//
// StringMap<std::unique_ptr<MemoryBuffer>>
// EmitDebugSections(llvm::DWARFYAML::Data &DI, bool ApplyFixups);
//
// For modifying data, like line numberes, we can in theory do that either on
// the DWARFContext or DWARFYAML::Data; unclear which is best, but modifying
// the DWARFContext may save us doing fixups in EmitDebugSections.
//
void writeDWARFSections(Module& wasm) {
BinaryenDWARFInfo info(wasm);
// Convert to Data representation, which YAML can use to write.
llvm::DWARFYAML::Data Data;
if (dwarf2yaml(*info.context, Data)) {
Fatal() << "Failed to parse DWARF to YAML";
}
// TODO: Actually update, and remove sections we don't know how to update yet?
// Convert to binary sections.
auto newSections = EmitDebugSections(
Data,
false /* ApplyFixups, should be true if we modify Data, presumably? */);
// Update the custom sections in the wasm.
// TODO: efficiency
for (auto& section : wasm.userSections) {
if (Name(section.name).startsWith(".debug_")) {
auto llvmName = section.name.substr(1);
if (newSections.count(llvmName)) {
auto llvmData = newSections[llvmName]->getBuffer();
section.data.resize(llvmData.size());
std::copy(llvmData.begin(), llvmData.end(), section.data.data());
}
}
}
}
#else // BUILD_LLVM_DWARF
void dumpDWARF(const Module& wasm) {
std::cerr << "warning: no DWARF dumping support present\n";
}
void writeDWARFSections(Module& wasm) {
std::cerr << "warning: no DWARF updating support present\n";
}
#endif // BUILD_LLVM_DWARF
} // namespace Debug
} // namespace wasm
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