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llvm-project/clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp
Yuta Saito 1813fde9cc [WebAssembly] Emit clangast in custom section aligned by 4 bytes 
Emit __clangast in custom section instead of named data segment
to find it while iterating sections.
This could be avoided if all data segements (the wasm sense) were
represented as their own sections (in the llvm sense).
This can be resolved by https://github.com/WebAssembly/tool-conventions/issues/138

And the on-disk hashtable in clangast needs to be aligned by 4 bytes,
so add paddings in name length field in custom section header.

The length of clangast section name can be represented in 1 byte
by leb128, and possible maximum pads are 3 bytes, so the section
name length won't be invalid in theory.

Fixes https://bugs.llvm.org/show_bug.cgi?id=35928

Differential Revision: https://reviews.llvm.org/D74531
2021-10-19 15:50:08 -07:00

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//===--- ObjectFilePCHContainerOperations.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 "clang/CodeGen/ObjectFilePCHContainerOperations.h"
#include "CGDebugInfo.h"
#include "CodeGenModule.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/Expr.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/Basic/CodeGenOptions.h"
#include "clang/Basic/Diagnostic.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/CodeGen/BackendUtil.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Lex/HeaderSearch.h"
#include "clang/Lex/Preprocessor.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Bitstream/BitstreamReader.h"
#include "llvm/DebugInfo/DWARF/DWARFContext.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Object/COFF.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/Path.h"
#include <memory>
#include <utility>
using namespace clang;
#define DEBUG_TYPE "pchcontainer"
namespace {
class PCHContainerGenerator : public ASTConsumer {
DiagnosticsEngine &Diags;
const std::string MainFileName;
const std::string OutputFileName;
ASTContext *Ctx;
ModuleMap &MMap;
const HeaderSearchOptions &HeaderSearchOpts;
const PreprocessorOptions &PreprocessorOpts;
CodeGenOptions CodeGenOpts;
const TargetOptions TargetOpts;
LangOptions LangOpts;
std::unique_ptr<llvm::LLVMContext> VMContext;
std::unique_ptr<llvm::Module> M;
std::unique_ptr<CodeGen::CodeGenModule> Builder;
std::unique_ptr<raw_pwrite_stream> OS;
std::shared_ptr<PCHBuffer> Buffer;
/// Visit every type and emit debug info for it.
struct DebugTypeVisitor : public RecursiveASTVisitor<DebugTypeVisitor> {
clang::CodeGen::CGDebugInfo &DI;
ASTContext &Ctx;
DebugTypeVisitor(clang::CodeGen::CGDebugInfo &DI, ASTContext &Ctx)
: DI(DI), Ctx(Ctx) {}
/// Determine whether this type can be represented in DWARF.
static bool CanRepresent(const Type *Ty) {
return !Ty->isDependentType() && !Ty->isUndeducedType();
}
bool VisitImportDecl(ImportDecl *D) {
if (!D->getImportedOwningModule())
DI.EmitImportDecl(*D);
return true;
}
bool VisitTypeDecl(TypeDecl *D) {
// TagDecls may be deferred until after all decls have been merged and we
// know the complete type. Pure forward declarations will be skipped, but
// they don't need to be emitted into the module anyway.
if (auto *TD = dyn_cast<TagDecl>(D))
if (!TD->isCompleteDefinition())
return true;
QualType QualTy = Ctx.getTypeDeclType(D);
if (!QualTy.isNull() && CanRepresent(QualTy.getTypePtr()))
DI.getOrCreateStandaloneType(QualTy, D->getLocation());
return true;
}
bool VisitObjCInterfaceDecl(ObjCInterfaceDecl *D) {
QualType QualTy(D->getTypeForDecl(), 0);
if (!QualTy.isNull() && CanRepresent(QualTy.getTypePtr()))
DI.getOrCreateStandaloneType(QualTy, D->getLocation());
return true;
}
bool VisitFunctionDecl(FunctionDecl *D) {
if (isa<CXXMethodDecl>(D))
// This is not yet supported. Constructing the `this' argument
// mandates a CodeGenFunction.
return true;
SmallVector<QualType, 16> ArgTypes;
for (auto i : D->parameters())
ArgTypes.push_back(i->getType());
QualType RetTy = D->getReturnType();
QualType FnTy = Ctx.getFunctionType(RetTy, ArgTypes,
FunctionProtoType::ExtProtoInfo());
if (CanRepresent(FnTy.getTypePtr()))
DI.EmitFunctionDecl(D, D->getLocation(), FnTy);
return true;
}
bool VisitObjCMethodDecl(ObjCMethodDecl *D) {
if (!D->getClassInterface())
return true;
bool selfIsPseudoStrong, selfIsConsumed;
SmallVector<QualType, 16> ArgTypes;
ArgTypes.push_back(D->getSelfType(Ctx, D->getClassInterface(),
selfIsPseudoStrong, selfIsConsumed));
ArgTypes.push_back(Ctx.getObjCSelType());
for (auto i : D->parameters())
ArgTypes.push_back(i->getType());
QualType RetTy = D->getReturnType();
QualType FnTy = Ctx.getFunctionType(RetTy, ArgTypes,
FunctionProtoType::ExtProtoInfo());
if (CanRepresent(FnTy.getTypePtr()))
DI.EmitFunctionDecl(D, D->getLocation(), FnTy);
return true;
}
};
public:
PCHContainerGenerator(CompilerInstance &CI, const std::string &MainFileName,
const std::string &OutputFileName,
std::unique_ptr<raw_pwrite_stream> OS,
std::shared_ptr<PCHBuffer> Buffer)
: Diags(CI.getDiagnostics()), MainFileName(MainFileName),
OutputFileName(OutputFileName), Ctx(nullptr),
MMap(CI.getPreprocessor().getHeaderSearchInfo().getModuleMap()),
HeaderSearchOpts(CI.getHeaderSearchOpts()),
PreprocessorOpts(CI.getPreprocessorOpts()),
TargetOpts(CI.getTargetOpts()), LangOpts(CI.getLangOpts()),
OS(std::move(OS)), Buffer(std::move(Buffer)) {
// The debug info output isn't affected by CodeModel and
// ThreadModel, but the backend expects them to be nonempty.
CodeGenOpts.CodeModel = "default";
LangOpts.setThreadModel(LangOptions::ThreadModelKind::Single);
CodeGenOpts.DebugTypeExtRefs = true;
// When building a module MainFileName is the name of the modulemap file.
CodeGenOpts.MainFileName =
LangOpts.CurrentModule.empty() ? MainFileName : LangOpts.CurrentModule;
CodeGenOpts.setDebugInfo(codegenoptions::FullDebugInfo);
CodeGenOpts.setDebuggerTuning(CI.getCodeGenOpts().getDebuggerTuning());
CodeGenOpts.DebugPrefixMap =
CI.getInvocation().getCodeGenOpts().DebugPrefixMap;
}
~PCHContainerGenerator() override = default;
void Initialize(ASTContext &Context) override {
assert(!Ctx && "initialized multiple times");
Ctx = &Context;
VMContext.reset(new llvm::LLVMContext());
M.reset(new llvm::Module(MainFileName, *VMContext));
M->setDataLayout(Ctx->getTargetInfo().getDataLayoutString());
Builder.reset(new CodeGen::CodeGenModule(
*Ctx, HeaderSearchOpts, PreprocessorOpts, CodeGenOpts, *M, Diags));
// Prepare CGDebugInfo to emit debug info for a clang module.
auto *DI = Builder->getModuleDebugInfo();
StringRef ModuleName = llvm::sys::path::filename(MainFileName);
DI->setPCHDescriptor(
{ModuleName, "", OutputFileName, ASTFileSignature::createDISentinel()});
DI->setModuleMap(MMap);
}
bool HandleTopLevelDecl(DeclGroupRef D) override {
if (Diags.hasErrorOccurred())
return true;
// Collect debug info for all decls in this group.
for (auto *I : D)
if (!I->isFromASTFile()) {
DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx);
DTV.TraverseDecl(I);
}
return true;
}
void HandleTopLevelDeclInObjCContainer(DeclGroupRef D) override {
HandleTopLevelDecl(D);
}
void HandleTagDeclDefinition(TagDecl *D) override {
if (Diags.hasErrorOccurred())
return;
if (D->isFromASTFile())
return;
// Anonymous tag decls are deferred until we are building their declcontext.
if (D->getName().empty())
return;
// Defer tag decls until their declcontext is complete.
auto *DeclCtx = D->getDeclContext();
while (DeclCtx) {
if (auto *D = dyn_cast<TagDecl>(DeclCtx))
if (!D->isCompleteDefinition())
return;
DeclCtx = DeclCtx->getParent();
}
DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx);
DTV.TraverseDecl(D);
Builder->UpdateCompletedType(D);
}
void HandleTagDeclRequiredDefinition(const TagDecl *D) override {
if (Diags.hasErrorOccurred())
return;
if (const RecordDecl *RD = dyn_cast<RecordDecl>(D))
Builder->getModuleDebugInfo()->completeRequiredType(RD);
}
void HandleImplicitImportDecl(ImportDecl *D) override {
if (!D->getImportedOwningModule())
Builder->getModuleDebugInfo()->EmitImportDecl(*D);
}
/// Emit a container holding the serialized AST.
void HandleTranslationUnit(ASTContext &Ctx) override {
assert(M && VMContext && Builder);
// Delete these on function exit.
std::unique_ptr<llvm::LLVMContext> VMContext = std::move(this->VMContext);
std::unique_ptr<llvm::Module> M = std::move(this->M);
std::unique_ptr<CodeGen::CodeGenModule> Builder = std::move(this->Builder);
if (Diags.hasErrorOccurred())
return;
M->setTargetTriple(Ctx.getTargetInfo().getTriple().getTriple());
M->setDataLayout(Ctx.getTargetInfo().getDataLayoutString());
// PCH files don't have a signature field in the control block,
// but LLVM detects DWO CUs by looking for a non-zero DWO id.
// We use the lower 64 bits for debug info.
uint64_t Signature =
Buffer->Signature ? Buffer->Signature.truncatedValue() : ~1ULL;
Builder->getModuleDebugInfo()->setDwoId(Signature);
// Finalize the Builder.
if (Builder)
Builder->Release();
// Ensure the target exists.
std::string Error;
auto Triple = Ctx.getTargetInfo().getTriple();
if (!llvm::TargetRegistry::lookupTarget(Triple.getTriple(), Error))
llvm::report_fatal_error(llvm::Twine(Error));
// Emit the serialized Clang AST into its own section.
assert(Buffer->IsComplete && "serialization did not complete");
auto &SerializedAST = Buffer->Data;
auto Size = SerializedAST.size();
if (Triple.isOSBinFormatWasm()) {
// Emit __clangast in custom section instead of named data segment
// to find it while iterating sections.
// This could be avoided if all data segements (the wasm sense) were
// represented as their own sections (in the llvm sense).
// TODO: https://github.com/WebAssembly/tool-conventions/issues/138
llvm::NamedMDNode *MD =
M->getOrInsertNamedMetadata("wasm.custom_sections");
llvm::Metadata *Ops[2] = {
llvm::MDString::get(*VMContext, "__clangast"),
llvm::MDString::get(*VMContext,
StringRef(SerializedAST.data(), Size))};
auto *NameAndContent = llvm::MDTuple::get(*VMContext, Ops);
MD->addOperand(NameAndContent);
} else {
auto Int8Ty = llvm::Type::getInt8Ty(*VMContext);
auto *Ty = llvm::ArrayType::get(Int8Ty, Size);
auto *Data = llvm::ConstantDataArray::getString(
*VMContext, StringRef(SerializedAST.data(), Size),
/*AddNull=*/false);
auto *ASTSym = new llvm::GlobalVariable(
*M, Ty, /*constant*/ true, llvm::GlobalVariable::InternalLinkage,
Data, "__clang_ast");
// The on-disk hashtable needs to be aligned.
ASTSym->setAlignment(llvm::Align(8));
// Mach-O also needs a segment name.
if (Triple.isOSBinFormatMachO())
ASTSym->setSection("__CLANG,__clangast");
// COFF has an eight character length limit.
else if (Triple.isOSBinFormatCOFF())
ASTSym->setSection("clangast");
else
ASTSym->setSection("__clangast");
}
LLVM_DEBUG({
// Print the IR for the PCH container to the debug output.
llvm::SmallString<0> Buffer;
clang::EmitBackendOutput(
Diags, HeaderSearchOpts, CodeGenOpts, TargetOpts, LangOpts,
Ctx.getTargetInfo().getDataLayoutString(), M.get(),
BackendAction::Backend_EmitLL,
std::make_unique<llvm::raw_svector_ostream>(Buffer));
llvm::dbgs() << Buffer;
});
// Use the LLVM backend to emit the pch container.
clang::EmitBackendOutput(Diags, HeaderSearchOpts, CodeGenOpts, TargetOpts,
LangOpts,
Ctx.getTargetInfo().getDataLayoutString(), M.get(),
BackendAction::Backend_EmitObj, std::move(OS));
// Free the memory for the temporary buffer.
llvm::SmallVector<char, 0> Empty;
SerializedAST = std::move(Empty);
}
};
} // anonymous namespace
std::unique_ptr<ASTConsumer>
ObjectFilePCHContainerWriter::CreatePCHContainerGenerator(
CompilerInstance &CI, const std::string &MainFileName,
const std::string &OutputFileName,
std::unique_ptr<llvm::raw_pwrite_stream> OS,
std::shared_ptr<PCHBuffer> Buffer) const {
return std::make_unique<PCHContainerGenerator>(
CI, MainFileName, OutputFileName, std::move(OS), Buffer);
}
StringRef
ObjectFilePCHContainerReader::ExtractPCH(llvm::MemoryBufferRef Buffer) const {
StringRef PCH;
auto OFOrErr = llvm::object::ObjectFile::createObjectFile(Buffer);
if (OFOrErr) {
auto &OF = OFOrErr.get();
bool IsCOFF = isa<llvm::object::COFFObjectFile>(*OF);
// Find the clang AST section in the container.
for (auto &Section : OF->sections()) {
StringRef Name;
if (Expected<StringRef> NameOrErr = Section.getName())
Name = *NameOrErr;
else
consumeError(NameOrErr.takeError());
if ((!IsCOFF && Name == "__clangast") || (IsCOFF && Name == "clangast")) {
if (Expected<StringRef> E = Section.getContents())
return *E;
else {
handleAllErrors(E.takeError(), [&](const llvm::ErrorInfoBase &EIB) {
EIB.log(llvm::errs());
});
return "";
}
}
}
}
handleAllErrors(OFOrErr.takeError(), [&](const llvm::ErrorInfoBase &EIB) {
if (EIB.convertToErrorCode() ==
llvm::object::object_error::invalid_file_type)
// As a fallback, treat the buffer as a raw AST.
PCH = Buffer.getBuffer();
else
EIB.log(llvm::errs());
});
return PCH;
}
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