llvm-project/lldb/source/Plugins/ExpressionParser/Clang/ASTResultSynthesizer.cpp

//===-- ASTResultSynthesizer.cpp --------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "ASTResultSynthesizer.h"

#include "ClangPersistentVariables.h"

#include "lldb/Core/Log.h"
#include "lldb/Symbol/ClangASTContext.h"
#include "lldb/Symbol/ClangASTImporter.h"
#include "lldb/Target/Target.h"
#include "lldb/Utility/LLDBAssert.h"
#include "stdlib.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclGroup.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/Expr.h"
#include "clang/AST/Stmt.h"
#include "clang/Parse/Parser.h"
#include "clang/Sema/SemaDiagnostic.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/raw_ostream.h"

using namespace llvm;
using namespace clang;
using namespace lldb_private;

ASTResultSynthesizer::ASTResultSynthesizer(ASTConsumer *passthrough, bool top_level, Target &target)
    : m_ast_context(NULL),
      m_passthrough(passthrough),
      m_passthrough_sema(NULL),
      m_target(target),
      m_sema(NULL),
      m_top_level(top_level)
{
    if (!m_passthrough)
        return;

    m_passthrough_sema = dyn_cast<SemaConsumer>(passthrough);
}

ASTResultSynthesizer::~ASTResultSynthesizer()
{
}

void
ASTResultSynthesizer::Initialize(ASTContext &Context)
{
    m_ast_context = &Context;

    if (m_passthrough)
        m_passthrough->Initialize(Context);
}

void
ASTResultSynthesizer::TransformTopLevelDecl(Decl* D)
{
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

    if (NamedDecl *named_decl = dyn_cast<NamedDecl>(D))
    {
        if (log && log->GetVerbose())
        {
            if (named_decl->getIdentifier())
                log->Printf("TransformTopLevelDecl(%s)", named_decl->getIdentifier()->getNameStart());
            else if (ObjCMethodDecl *method_decl = dyn_cast<ObjCMethodDecl>(D))
                log->Printf("TransformTopLevelDecl(%s)", method_decl->getSelector().getAsString().c_str());
            else
                log->Printf("TransformTopLevelDecl(<complex>)");
        }

        if (m_top_level)
        {
            RecordPersistentDecl(named_decl);
        }
    }

    if (LinkageSpecDecl *linkage_spec_decl = dyn_cast<LinkageSpecDecl>(D))
    {
        RecordDecl::decl_iterator decl_iterator;

        for (decl_iterator = linkage_spec_decl->decls_begin();
             decl_iterator != linkage_spec_decl->decls_end();
             ++decl_iterator)
        {
            TransformTopLevelDecl(*decl_iterator);
        }
    }
    else if (!m_top_level)
    {
        if (ObjCMethodDecl *method_decl = dyn_cast<ObjCMethodDecl>(D))
        {
            if (m_ast_context && !method_decl->getSelector().getAsString().compare("$__lldb_expr:"))
            {
                RecordPersistentTypes(method_decl);
                SynthesizeObjCMethodResult(method_decl);
            }
        }
        else if (FunctionDecl *function_decl = dyn_cast<FunctionDecl>(D))
        {
            if (m_ast_context && !function_decl->getNameInfo().getAsString().compare("$__lldb_expr"))
            {
                RecordPersistentTypes(function_decl);
                SynthesizeFunctionResult(function_decl);
            }
        }
    }
}

bool
ASTResultSynthesizer::HandleTopLevelDecl(DeclGroupRef D)
{
    DeclGroupRef::iterator decl_iterator;

    for (decl_iterator = D.begin();
         decl_iterator != D.end();
         ++decl_iterator)
    {
        Decl *decl = *decl_iterator;

        TransformTopLevelDecl(decl);
    }

    if (m_passthrough)
        return m_passthrough->HandleTopLevelDecl(D);
    return true;
}

bool
ASTResultSynthesizer::SynthesizeFunctionResult (FunctionDecl *FunDecl)
{
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

    if (!m_sema)
        return false;

    FunctionDecl *function_decl = FunDecl;

    if (!function_decl)
        return false;

    if (log && log->GetVerbose())
    {
        std::string s;
        raw_string_ostream os(s);

        function_decl->print(os);

        os.flush();

        log->Printf ("Untransformed function AST:\n%s", s.c_str());
    }

    Stmt *function_body = function_decl->getBody();
    CompoundStmt *compound_stmt = dyn_cast<CompoundStmt>(function_body);

    bool ret = SynthesizeBodyResult (compound_stmt,
                                     function_decl);

    if (log && log->GetVerbose())
    {
        std::string s;
        raw_string_ostream os(s);

        function_decl->print(os);

        os.flush();

        log->Printf ("Transformed function AST:\n%s", s.c_str());
    }

    return ret;
}

bool
ASTResultSynthesizer::SynthesizeObjCMethodResult (ObjCMethodDecl *MethodDecl)
{
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

    if (!m_sema)
        return false;

    if (!MethodDecl)
        return false;

    if (log && log->GetVerbose())
    {
        std::string s;
        raw_string_ostream os(s);

        MethodDecl->print(os);

        os.flush();

        log->Printf ("Untransformed method AST:\n%s", s.c_str());
    }

    Stmt *method_body = MethodDecl->getBody();

    if (!method_body)
        return false;

    CompoundStmt *compound_stmt = dyn_cast<CompoundStmt>(method_body);

    bool ret = SynthesizeBodyResult (compound_stmt,
                                     MethodDecl);

    if (log && log->GetVerbose())
    {
        std::string s;
        raw_string_ostream os(s);

        MethodDecl->print(os);

        os.flush();

        log->Printf("Transformed method AST:\n%s", s.c_str());
    }

    return ret;
}

bool
ASTResultSynthesizer::SynthesizeBodyResult (CompoundStmt *Body,
                                            DeclContext *DC)
{
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

    ASTContext &Ctx(*m_ast_context);

    if (!Body)
        return false;

    if (Body->body_empty())
        return false;

    Stmt **last_stmt_ptr = Body->body_end() - 1;
    Stmt *last_stmt = *last_stmt_ptr;

    while (dyn_cast<NullStmt>(last_stmt))
    {
        if (last_stmt_ptr != Body->body_begin())
        {
            last_stmt_ptr--;
            last_stmt = *last_stmt_ptr;
        }
        else
        {
            return false;
        }
    }

    Expr *last_expr = dyn_cast<Expr>(last_stmt);

    if (!last_expr)
        // No auxiliary variable necessary; expression returns void
        return true;

    // In C++11, last_expr can be a LValueToRvalue implicit cast.  Strip that off if that's the
    // case.

    do {
        ImplicitCastExpr *implicit_cast = dyn_cast<ImplicitCastExpr>(last_expr);

        if (!implicit_cast)
            break;

        if (implicit_cast->getCastKind() != CK_LValueToRValue)
            break;

        last_expr = implicit_cast->getSubExpr();
    } while (0);

    // is_lvalue is used to record whether the expression returns an assignable Lvalue or an
    // Rvalue.  This is relevant because they are handled differently.
    //
    // For Lvalues
    //
    //   - In AST result synthesis (here!) the expression E is transformed into an initialization
    //     T *$__lldb_expr_result_ptr = &E.
    //
    //   - In structure allocation, a pointer-sized slot is allocated in the struct that is to be
    //     passed into the expression.
    //
    //   - In IR transformations, reads and writes to $__lldb_expr_result_ptr are redirected at
    //     an entry in the struct ($__lldb_arg) passed into the expression.  (Other persistent
    //     variables are treated similarly, having been materialized as references, but in those
    //     cases the value of the reference itself is never modified.)
    //
    //   - During materialization, $0 (the result persistent variable) is ignored.
    //
    //   - During dematerialization, $0 is marked up as a load address with value equal to the
    //     contents of the structure entry.
    //
    // For Rvalues
    //
    //   - In AST result synthesis the expression E is transformed into an initialization
    //     static T $__lldb_expr_result = E.
    //
    //   - In structure allocation, a pointer-sized slot is allocated in the struct that is to be
    //     passed into the expression.
    //
    //   - In IR transformations, an instruction is inserted at the beginning of the function to
    //     dereference the pointer resident in the slot.  Reads and writes to $__lldb_expr_result
    //     are redirected at that dereferenced version.  Guard variables for the static variable
    //     are excised.
    //
    //   - During materialization, $0 (the result persistent variable) is populated with the location
    //     of a newly-allocated area of memory.
    //
    //   - During dematerialization, $0 is ignored.

    bool is_lvalue =
        (last_expr->getValueKind() == VK_LValue || last_expr->getValueKind() == VK_XValue) &&
        (last_expr->getObjectKind() == OK_Ordinary);

    QualType expr_qual_type = last_expr->getType();
    const clang::Type *expr_type = expr_qual_type.getTypePtr();

    if (!expr_type)
        return false;

    if (expr_type->isVoidType())
        return true;

    if (log)
    {
        std::string s = expr_qual_type.getAsString();

        log->Printf("Last statement is an %s with type: %s", (is_lvalue ? "lvalue" : "rvalue"), s.c_str());
    }

    clang::VarDecl *result_decl = NULL;

    if (is_lvalue)
    {
        IdentifierInfo *result_ptr_id;

        if (expr_type->isFunctionType())
            result_ptr_id = &Ctx.Idents.get("$__lldb_expr_result"); // functions actually should be treated like function pointers
        else
            result_ptr_id = &Ctx.Idents.get("$__lldb_expr_result_ptr");

        m_sema->RequireCompleteType(SourceLocation(), expr_qual_type, clang::diag::err_incomplete_type);

        QualType ptr_qual_type;

        if (expr_qual_type->getAs<ObjCObjectType>() != NULL)
            ptr_qual_type = Ctx.getObjCObjectPointerType(expr_qual_type);
        else
            ptr_qual_type = Ctx.getPointerType(expr_qual_type);

        result_decl = VarDecl::Create(Ctx,
                                      DC,
                                      SourceLocation(),
                                      SourceLocation(),
                                      result_ptr_id,
                                      ptr_qual_type,
                                      NULL,
                                      SC_Static);

        if (!result_decl)
            return false;

        ExprResult address_of_expr = m_sema->CreateBuiltinUnaryOp(SourceLocation(), UO_AddrOf, last_expr);

        m_sema->AddInitializerToDecl(result_decl, address_of_expr.get(), true, false);
    }
    else
    {
        IdentifierInfo &result_id = Ctx.Idents.get("$__lldb_expr_result");

        result_decl = VarDecl::Create(Ctx,
                                      DC,
                                      SourceLocation(),
                                      SourceLocation(),
                                      &result_id,
                                      expr_qual_type,
                                      NULL,
                                      SC_Static);

        if (!result_decl)
            return false;

        m_sema->AddInitializerToDecl(result_decl, last_expr, true, false);
    }

    DC->addDecl(result_decl);

    ///////////////////////////////
    // call AddInitializerToDecl
    //

    //m_sema->AddInitializerToDecl(result_decl, last_expr);

    /////////////////////////////////
    // call ConvertDeclToDeclGroup
    //

    Sema::DeclGroupPtrTy result_decl_group_ptr;

    result_decl_group_ptr = m_sema->ConvertDeclToDeclGroup(result_decl);

    ////////////////////////
    // call ActOnDeclStmt
    //

    StmtResult result_initialization_stmt_result(m_sema->ActOnDeclStmt(result_decl_group_ptr,
                                                                       SourceLocation(),
                                                                       SourceLocation()));

    ////////////////////////////////////////////////
    // replace the old statement with the new one
    //

    *last_stmt_ptr = reinterpret_cast<Stmt*>(result_initialization_stmt_result.get());

    return true;
}

void
ASTResultSynthesizer::HandleTranslationUnit(ASTContext &Ctx)
{
    if (m_passthrough)
        m_passthrough->HandleTranslationUnit(Ctx);
}

void
ASTResultSynthesizer::RecordPersistentTypes(DeclContext *FunDeclCtx)
{
    typedef DeclContext::specific_decl_iterator<TypeDecl> TypeDeclIterator;

    for (TypeDeclIterator i = TypeDeclIterator(FunDeclCtx->decls_begin()),
         e = TypeDeclIterator(FunDeclCtx->decls_end());
         i != e;
         ++i)
    {
        MaybeRecordPersistentType(*i);
    }
}

void
ASTResultSynthesizer::MaybeRecordPersistentType(TypeDecl *D)
{
    if (!D->getIdentifier())
        return;

    StringRef name = D->getName();

    if (name.size() == 0 || name[0] != '$')
        return;

    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

    ConstString name_cs(name.str().c_str());

    if (log)
        log->Printf("Recording persistent type %s\n", name_cs.GetCString());

    m_decls.push_back(D);
}

void
ASTResultSynthesizer::RecordPersistentDecl(NamedDecl *D)
{
    lldbassert(m_top_level);

    if (!D->getIdentifier())
        return;

    StringRef name = D->getName();

    if (name.size() == 0)
        return;

    Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));

    ConstString name_cs(name.str().c_str());

    if (log)
        log->Printf("Recording persistent decl %s\n", name_cs.GetCString());

    m_decls.push_back(D);
}

void
ASTResultSynthesizer::CommitPersistentDecls()
{
    for (clang::NamedDecl *decl : m_decls)
    {
        StringRef name = decl->getName();
        ConstString name_cs(name.str().c_str());

        Decl *D_scratch = m_target.GetClangASTImporter()->DeportDecl(
            m_target.GetScratchClangASTContext()->getASTContext(), m_ast_context, decl);

        if (!D_scratch)
        {
            Log *log(lldb_private::GetLogIfAllCategoriesSet(LIBLLDB_LOG_EXPRESSIONS));

            if (log)
            {
                std::string s;
                llvm::raw_string_ostream ss(s);
                decl->dump(ss);
                ss.flush();

                log->Printf("Couldn't commit persistent  decl: %s\n", s.c_str());
            }

            continue;
        }

        if (NamedDecl *NamedDecl_scratch = dyn_cast<NamedDecl>(D_scratch))
            llvm::cast<ClangPersistentVariables>(m_target.GetPersistentExpressionStateForLanguage(lldb::eLanguageTypeC))
                ->RegisterPersistentDecl(name_cs, NamedDecl_scratch);
    }
}

void
ASTResultSynthesizer::HandleTagDeclDefinition(TagDecl *D)
{
    if (m_passthrough)
        m_passthrough->HandleTagDeclDefinition(D);
}

void
ASTResultSynthesizer::CompleteTentativeDefinition(VarDecl *D)
{
    if (m_passthrough)
        m_passthrough->CompleteTentativeDefinition(D);
}

void
ASTResultSynthesizer::HandleVTable(CXXRecordDecl *RD)
{
    if (m_passthrough)
        m_passthrough->HandleVTable(RD);
}

void
ASTResultSynthesizer::PrintStats()
{
    if (m_passthrough)
        m_passthrough->PrintStats();
}

void
ASTResultSynthesizer::InitializeSema(Sema &S)
{
    m_sema = &S;

    if (m_passthrough_sema)
        m_passthrough_sema->InitializeSema(S);
}

void
ASTResultSynthesizer::ForgetSema()
{
    m_sema = NULL;

    if (m_passthrough_sema)
        m_passthrough_sema->ForgetSema();
}