lldb/source/Plugins/ExpressionParser/Clang/ClangExpressionParser.cpp

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

// C Includes
// C++ Includes
// Other libraries and framework includes
#include "clang/AST/ASTContext.h"
#include "clang/AST/ExternalASTSource.h"
#include "clang/Basic/FileManager.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/Version.h"
#include "clang/CodeGen/CodeGenAction.h"
#include "clang/CodeGen/ModuleBuilder.h"
#include "clang/Frontend/CompilerInstance.h"
#include "clang/Frontend/CompilerInvocation.h"
#include "clang/Frontend/FrontendActions.h"
#include "clang/Frontend/FrontendDiagnostic.h"
#include "clang/Frontend/FrontendPluginRegistry.h"
#include "clang/Frontend/TextDiagnosticBuffer.h"
#include "clang/Frontend/TextDiagnosticPrinter.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Parse/ParseAST.h"
#include "clang/Rewrite/Frontend/FrontendActions.h"
#include "clang/Sema/SemaConsumer.h"
#include "clang/StaticAnalyzer/Frontend/FrontendActions.h"

#include "llvm/ADT/StringRef.h"
#include "llvm/ExecutionEngine/ExecutionEngine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/TargetSelect.h"

#include "llvm/ExecutionEngine/MCJIT.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/DynamicLibrary.h"
#include "llvm/Support/Host.h"
#include "llvm/Support/Signals.h"

// Project includes
#include "ClangExpressionParser.h"

#include "ClangASTSource.h"
#include "ClangExpressionHelper.h"
#include "ClangExpressionDeclMap.h"
#include "ClangModulesDeclVendor.h"
#include "ClangPersistentVariables.h"
#include "IRForTarget.h"

#include "lldb/Core/ArchSpec.h"
#include "lldb/Core/DataBufferHeap.h"
#include "lldb/Core/Debugger.h"
#include "lldb/Core/Disassembler.h"
#include "lldb/Core/Log.h"
#include "lldb/Core/Module.h"
#include "lldb/Core/Stream.h"
#include "lldb/Core/StreamFile.h"
#include "lldb/Core/StringList.h"
#include "lldb/Core/StreamString.h"
#include "lldb/Expression/IRExecutionUnit.h"
#include "lldb/Expression/IRDynamicChecks.h"
#include "lldb/Expression/IRInterpreter.h"
#include "lldb/Host/File.h"
#include "lldb/Host/HostInfo.h"
#include "lldb/Symbol/ClangASTContext.h"
#include "lldb/Symbol/SymbolVendor.h"
#include "lldb/Target/ExecutionContext.h"
#include "lldb/Target/ObjCLanguageRuntime.h"
#include "lldb/Target/Process.h"
#include "lldb/Target/Target.h"
#include "lldb/Target/Language.h"

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

//===----------------------------------------------------------------------===//
// Utility Methods for Clang
//===----------------------------------------------------------------------===//

std::string GetBuiltinIncludePath(const char *Argv0) {
    SmallString<128> P(llvm::sys::fs::getMainExecutable(
        Argv0, (void *)(intptr_t) GetBuiltinIncludePath));

    if (!P.empty()) {
        llvm::sys::path::remove_filename(P); // Remove /clang from foo/bin/clang
        llvm::sys::path::remove_filename(P); // Remove /bin   from foo/bin

        // Get foo/lib/clang/<version>/include
        llvm::sys::path::append(P, "lib", "clang", CLANG_VERSION_STRING,
                                "include");
    }

    return P.str();
}

class ClangExpressionParser::LLDBPreprocessorCallbacks : public PPCallbacks
{
    ClangModulesDeclVendor     &m_decl_vendor;
    ClangPersistentVariables   &m_persistent_vars;
    StreamString                m_error_stream;
    bool                        m_has_errors = false;

public:
    LLDBPreprocessorCallbacks(ClangModulesDeclVendor &decl_vendor,
                              ClangPersistentVariables &persistent_vars) :
        m_decl_vendor(decl_vendor),
        m_persistent_vars(persistent_vars)
    {
    }
    
    void
    moduleImport(SourceLocation import_location,
                 clang::ModuleIdPath path,
                 const clang::Module * /*null*/) override
    {
        std::vector<ConstString> string_path;
        
        for (const std::pair<IdentifierInfo *, SourceLocation> &component : path)
        {
            string_path.push_back(ConstString(component.first->getName()));
        }
     
        StreamString error_stream;
        
        ClangModulesDeclVendor::ModuleVector exported_modules;
        
        if (!m_decl_vendor.AddModule(string_path, &exported_modules, m_error_stream))
        {
            m_has_errors = true;
        }
        
        for (ClangModulesDeclVendor::ModuleID module : exported_modules)
        {
            m_persistent_vars.AddHandLoadedClangModule(module);
        }
    }
    
    bool hasErrors()
    {
        return m_has_errors;
    }
    
    const std::string &getErrorString()
    {
        return m_error_stream.GetString();
    }
};

//===----------------------------------------------------------------------===//
// Implementation of ClangExpressionParser
//===----------------------------------------------------------------------===//

ClangExpressionParser::ClangExpressionParser (ExecutionContextScope *exe_scope,
                                              Expression &expr,
                                              bool generate_debug_info) :
    ExpressionParser (exe_scope, expr, generate_debug_info),
    m_compiler (),
    m_code_generator (),
    m_pp_callbacks(nullptr)
{
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

    // 1. Create a new compiler instance.
    m_compiler.reset(new CompilerInstance());
    lldb::LanguageType frame_lang = expr.Language(); // defaults to lldb::eLanguageTypeUnknown
    bool overridden_target_opts = false;
    lldb_private::LanguageRuntime *lang_rt = nullptr;
    lldb::TargetSP target_sp;
    if (exe_scope)
        target_sp = exe_scope->CalculateTarget();

    // If the expression is being evaluated in the context of an existing
    // stack frame, we introspect to see if the language runtime is available.
    auto frame = exe_scope->CalculateStackFrame();

    // Make sure the user hasn't provided a preferred execution language
    // with `expression --language X -- ...`
    if (frame && frame_lang == lldb::eLanguageTypeUnknown)
        frame_lang = frame->GetLanguage();

    if (frame_lang != lldb::eLanguageTypeUnknown)
    {
        lang_rt = exe_scope->CalculateProcess()->GetLanguageRuntime(frame_lang);
        if (log)
            log->Printf("Frame has language of type %s", Language::GetNameForLanguageType(frame_lang));
    }

    // 2. Configure the compiler with a set of default options that are appropriate
    // for most situations.
    if (target_sp && target_sp->GetArchitecture().IsValid())
    {
        std::string triple = target_sp->GetArchitecture().GetTriple().str();
        m_compiler->getTargetOpts().Triple = triple;
        if (log)
            log->Printf("Using %s as the target triple", m_compiler->getTargetOpts().Triple.c_str());
    }
    else
    {
        // If we get here we don't have a valid target and just have to guess.
        // Sometimes this will be ok to just use the host target triple (when we evaluate say "2+3", but other
        // expressions like breakpoint conditions and other things that _are_ target specific really shouldn't just be
        // using the host triple. In such a case the language runtime should expose an overridden options set (3),
        // below.
        m_compiler->getTargetOpts().Triple = llvm::sys::getDefaultTargetTriple();
        if (log)
            log->Printf("Using default target triple of %s", m_compiler->getTargetOpts().Triple.c_str());
    }
    // Now add some special fixes for known architectures:
    // Any arm32 iOS environment, but not on arm64
    if (m_compiler->getTargetOpts().Triple.find("arm64") == std::string::npos &&
        m_compiler->getTargetOpts().Triple.find("arm") != std::string::npos &&
        m_compiler->getTargetOpts().Triple.find("ios") != std::string::npos)
    {
        m_compiler->getTargetOpts().ABI = "apcs-gnu";
    }
    // Supported subsets of x86
    if (target_sp->GetArchitecture().GetMachine() == llvm::Triple::x86 ||
        target_sp->GetArchitecture().GetMachine() == llvm::Triple::x86_64)
    {
        m_compiler->getTargetOpts().Features.push_back("+sse");
        m_compiler->getTargetOpts().Features.push_back("+sse2");
    }

    // 3. Now allow the runtime to provide custom configuration options for the target.
    // In this case, a specialized language runtime is available and we can query it for extra options.
    // For 99% of use cases, this will not be needed and should be provided when basic platform detection is not enough.
    if (lang_rt)
        overridden_target_opts = lang_rt->GetOverrideExprOptions(m_compiler->getTargetOpts());

    if (overridden_target_opts)
        if (log)
        {
            log->Debug("Using overridden target options for the expression evaluation");

            auto opts = m_compiler->getTargetOpts();
            log->Debug("Triple: '%s'", opts.Triple.c_str());
            log->Debug("CPU: '%s'", opts.CPU.c_str());
            log->Debug("FPMath: '%s'", opts.FPMath.c_str());
            log->Debug("ABI: '%s'", opts.ABI.c_str());
            log->Debug("LinkerVersion: '%s'", opts.LinkerVersion.c_str());
            StringList::LogDump(log, opts.FeaturesAsWritten, "FeaturesAsWritten");
            StringList::LogDump(log, opts.Features, "Features");
            StringList::LogDump(log, opts.Reciprocals, "Reciprocals");
        }

    // 4. Create and install the target on the compiler.
    m_compiler->createDiagnostics();
    auto target_info = TargetInfo::CreateTargetInfo(m_compiler->getDiagnostics(), m_compiler->getInvocation().TargetOpts);
    if (log)
    {
        log->Printf("Using SIMD alignment: %d", target_info->getSimdDefaultAlign());
        log->Printf("Target datalayout string: '%s'", target_info->getDataLayoutString());
        log->Printf("Target ABI: '%s'", target_info->getABI().str().c_str());
        log->Printf("Target vector alignment: %d", target_info->getMaxVectorAlign());
    }
    m_compiler->setTarget(target_info);

    assert (m_compiler->hasTarget());

    // 5. Set language options.
    lldb::LanguageType language = expr.Language();

    switch (language)
    {
    case lldb::eLanguageTypeC:
    case lldb::eLanguageTypeC89:
    case lldb::eLanguageTypeC99:
    case lldb::eLanguageTypeC11:
        // FIXME: the following language option is a temporary workaround,
        // to "ask for C, get C++."
        // For now, the expression parser must use C++ anytime the
        // language is a C family language, because the expression parser
        // uses features of C++ to capture values.
        m_compiler->getLangOpts().CPlusPlus = true;
        break;
    case lldb::eLanguageTypeObjC:
        m_compiler->getLangOpts().ObjC1 = true;
        m_compiler->getLangOpts().ObjC2 = true;
        // FIXME: the following language option is a temporary workaround,
        // to "ask for ObjC, get ObjC++" (see comment above).
        m_compiler->getLangOpts().CPlusPlus = true;
        break;
    case lldb::eLanguageTypeC_plus_plus:
    case lldb::eLanguageTypeC_plus_plus_11:
    case lldb::eLanguageTypeC_plus_plus_14:
        m_compiler->getLangOpts().CPlusPlus11 = true;
        m_compiler->getHeaderSearchOpts().UseLibcxx = true;
        // fall thru ...
    case lldb::eLanguageTypeC_plus_plus_03:
        m_compiler->getLangOpts().CPlusPlus = true;
        // FIXME: the following language option is a temporary workaround,
        // to "ask for C++, get ObjC++".  Apple hopes to remove this requirement
        // on non-Apple platforms, but for now it is needed.
        m_compiler->getLangOpts().ObjC1 = true;
        break;
    case lldb::eLanguageTypeObjC_plus_plus:
    case lldb::eLanguageTypeUnknown:
    default:
        m_compiler->getLangOpts().ObjC1 = true;
        m_compiler->getLangOpts().ObjC2 = true;
        m_compiler->getLangOpts().CPlusPlus = true;
        m_compiler->getLangOpts().CPlusPlus11 = true;
        m_compiler->getHeaderSearchOpts().UseLibcxx = true;
        break;
    }

    m_compiler->getLangOpts().Bool = true;
    m_compiler->getLangOpts().WChar = true;
    m_compiler->getLangOpts().Blocks = true;
    m_compiler->getLangOpts().DebuggerSupport = true; // Features specifically for debugger clients
    if (expr.DesiredResultType() == Expression::eResultTypeId)
        m_compiler->getLangOpts().DebuggerCastResultToId = true;

    m_compiler->getLangOpts().CharIsSigned =
            ArchSpec(m_compiler->getTargetOpts().Triple.c_str()).CharIsSignedByDefault();

    // Spell checking is a nice feature, but it ends up completing a
    // lot of types that we didn't strictly speaking need to complete.
    // As a result, we spend a long time parsing and importing debug
    // information.
    m_compiler->getLangOpts().SpellChecking = false;

    lldb::ProcessSP process_sp;
    if (exe_scope)
        process_sp = exe_scope->CalculateProcess();

    if (process_sp && m_compiler->getLangOpts().ObjC1)
    {
        if (process_sp->GetObjCLanguageRuntime())
        {
            if (process_sp->GetObjCLanguageRuntime()->GetRuntimeVersion() == ObjCLanguageRuntime::ObjCRuntimeVersions::eAppleObjC_V2)
                m_compiler->getLangOpts().ObjCRuntime.set(ObjCRuntime::MacOSX, VersionTuple(10, 7));
            else
                m_compiler->getLangOpts().ObjCRuntime.set(ObjCRuntime::FragileMacOSX, VersionTuple(10, 7));

            if (process_sp->GetObjCLanguageRuntime()->HasNewLiteralsAndIndexing())
                m_compiler->getLangOpts().DebuggerObjCLiteral = true;
        }
    }

    m_compiler->getLangOpts().ThreadsafeStatics = false;
    m_compiler->getLangOpts().AccessControl = false; // Debuggers get universal access
    m_compiler->getLangOpts().DollarIdents = true; // $ indicates a persistent variable name

    // Set CodeGen options
    m_compiler->getCodeGenOpts().EmitDeclMetadata = true;
    m_compiler->getCodeGenOpts().InstrumentFunctions = false;
    m_compiler->getCodeGenOpts().DisableFPElim = true;
    m_compiler->getCodeGenOpts().OmitLeafFramePointer = false;
    if (generate_debug_info)
        m_compiler->getCodeGenOpts().setDebugInfo(codegenoptions::FullDebugInfo);
    else
        m_compiler->getCodeGenOpts().setDebugInfo(codegenoptions::NoDebugInfo);

    // Disable some warnings.
    m_compiler->getDiagnostics().setSeverityForGroup(clang::diag::Flavor::WarningOrError,
        "unused-value", clang::diag::Severity::Ignored, SourceLocation());
    m_compiler->getDiagnostics().setSeverityForGroup(clang::diag::Flavor::WarningOrError,
        "odr", clang::diag::Severity::Ignored, SourceLocation());

    // Inform the target of the language options
    //
    // FIXME: We shouldn't need to do this, the target should be immutable once
    // created. This complexity should be lifted elsewhere.
    m_compiler->getTarget().adjust(m_compiler->getLangOpts());

    // 6. Set up the diagnostic buffer for reporting errors

    m_compiler->getDiagnostics().setClient(new clang::TextDiagnosticBuffer);

    // 7. Set up the source management objects inside the compiler

    clang::FileSystemOptions file_system_options;
    m_file_manager.reset(new clang::FileManager(file_system_options));

    if (!m_compiler->hasSourceManager())
        m_compiler->createSourceManager(*m_file_manager.get());

    m_compiler->createFileManager();
    m_compiler->createPreprocessor(TU_Complete);
    
    if (ClangModulesDeclVendor *decl_vendor = target_sp->GetClangModulesDeclVendor())
    {
        ClangPersistentVariables *clang_persistent_vars = llvm::cast<ClangPersistentVariables>(target_sp->GetPersistentExpressionStateForLanguage(lldb::eLanguageTypeC));
        std::unique_ptr<PPCallbacks> pp_callbacks(new LLDBPreprocessorCallbacks(*decl_vendor, *clang_persistent_vars));
        m_pp_callbacks = static_cast<LLDBPreprocessorCallbacks*>(pp_callbacks.get());
        m_compiler->getPreprocessor().addPPCallbacks(std::move(pp_callbacks));
    }
        
    // 8. Most of this we get from the CompilerInstance, but we
    // also want to give the context an ExternalASTSource.
    m_selector_table.reset(new SelectorTable());
    m_builtin_context.reset(new Builtin::Context());

    std::unique_ptr<clang::ASTContext> ast_context(new ASTContext(m_compiler->getLangOpts(),
                                                                  m_compiler->getSourceManager(),
                                                                  m_compiler->getPreprocessor().getIdentifierTable(),
                                                                  *m_selector_table.get(),
                                                                  *m_builtin_context.get()));
    
    ast_context->InitBuiltinTypes(m_compiler->getTarget());

    ClangExpressionHelper *type_system_helper = dyn_cast<ClangExpressionHelper>(m_expr.GetTypeSystemHelper());
    ClangExpressionDeclMap *decl_map = type_system_helper->DeclMap();

    if (decl_map)
    {
        llvm::IntrusiveRefCntPtr<clang::ExternalASTSource> ast_source(decl_map->CreateProxy());
        decl_map->InstallASTContext(ast_context.get());
        ast_context->setExternalSource(ast_source);
    }

    m_ast_context.reset(new ClangASTContext(m_compiler->getTargetOpts().Triple.c_str()));
    m_ast_context->setASTContext(ast_context.get());
    m_compiler->setASTContext(ast_context.release());

    std::string module_name("$__lldb_module");

    m_llvm_context.reset(new LLVMContext());
    m_code_generator.reset(CreateLLVMCodeGen(m_compiler->getDiagnostics(),
                                             module_name,
                                             m_compiler->getHeaderSearchOpts(),
                                             m_compiler->getPreprocessorOpts(),
                                             m_compiler->getCodeGenOpts(),
                                             *m_llvm_context));
}

ClangExpressionParser::~ClangExpressionParser()
{
}

unsigned
ClangExpressionParser::Parse (Stream &stream)
{
    TextDiagnosticBuffer *diag_buf = static_cast<TextDiagnosticBuffer*>(m_compiler->getDiagnostics().getClient());

    diag_buf->FlushDiagnostics (m_compiler->getDiagnostics());

    const char *expr_text = m_expr.Text();

    clang::SourceManager &SourceMgr = m_compiler->getSourceManager();
    bool created_main_file = false;
    if (m_compiler->getCodeGenOpts().getDebugInfo() == codegenoptions::FullDebugInfo)
    {
        std::string temp_source_path;

        int temp_fd = -1;
        llvm::SmallString<PATH_MAX> result_path;
        FileSpec tmpdir_file_spec;
        if (HostInfo::GetLLDBPath(lldb::ePathTypeLLDBTempSystemDir, tmpdir_file_spec))
        {
            tmpdir_file_spec.AppendPathComponent("lldb-%%%%%%.expr");
            temp_source_path = tmpdir_file_spec.GetPath();
            llvm::sys::fs::createUniqueFile(temp_source_path, temp_fd, result_path);
        }
        else
        {
            llvm::sys::fs::createTemporaryFile("lldb", "expr", temp_fd, result_path);
        }
        
        if (temp_fd != -1)
        {
            lldb_private::File file (temp_fd, true);
            const size_t expr_text_len = strlen(expr_text);
            size_t bytes_written = expr_text_len;
            if (file.Write(expr_text, bytes_written).Success())
            {
                if (bytes_written == expr_text_len)
                {
                    file.Close();
                    SourceMgr.setMainFileID(SourceMgr.createFileID(
                        m_file_manager->getFile(result_path),
                        SourceLocation(), SrcMgr::C_User));
                    created_main_file = true;
                }
            }
        }
    }

    if (!created_main_file)
    {
        std::unique_ptr<MemoryBuffer> memory_buffer = MemoryBuffer::getMemBufferCopy(expr_text, __FUNCTION__);
        SourceMgr.setMainFileID(SourceMgr.createFileID(std::move(memory_buffer)));
    }

    diag_buf->BeginSourceFile(m_compiler->getLangOpts(), &m_compiler->getPreprocessor());

    ClangExpressionHelper *type_system_helper = dyn_cast<ClangExpressionHelper>(m_expr.GetTypeSystemHelper());

    ASTConsumer *ast_transformer = type_system_helper->ASTTransformer(m_code_generator.get());

    if (ClangExpressionDeclMap *decl_map = type_system_helper->DeclMap())
        decl_map->InstallCodeGenerator(m_code_generator.get());

    if (ast_transformer)
    {
        ast_transformer->Initialize(m_compiler->getASTContext());
        ParseAST(m_compiler->getPreprocessor(), ast_transformer, m_compiler->getASTContext());
    }
    else
    {
        m_code_generator->Initialize(m_compiler->getASTContext());
        ParseAST(m_compiler->getPreprocessor(), m_code_generator.get(), m_compiler->getASTContext());
    }

    diag_buf->EndSourceFile();

    TextDiagnosticBuffer::const_iterator diag_iterator;

    int num_errors = 0;
    
    if (m_pp_callbacks && m_pp_callbacks->hasErrors())
    {
        num_errors++;
        
        stream.PutCString(m_pp_callbacks->getErrorString().c_str());
    }

    for (diag_iterator = diag_buf->warn_begin();
         diag_iterator != diag_buf->warn_end();
         ++diag_iterator)
        stream.Printf("warning: %s\n", (*diag_iterator).second.c_str());

    for (diag_iterator = diag_buf->err_begin();
         diag_iterator != diag_buf->err_end();
         ++diag_iterator)
    {
        num_errors++;
        stream.Printf("error: %s\n", (*diag_iterator).second.c_str());
    }

    for (diag_iterator = diag_buf->note_begin();
         diag_iterator != diag_buf->note_end();
         ++diag_iterator)
        stream.Printf("note: %s\n", (*diag_iterator).second.c_str());

    if (!num_errors)
    {
        if (type_system_helper->DeclMap() && !type_system_helper->DeclMap()->ResolveUnknownTypes())
        {
            stream.Printf("error: Couldn't infer the type of a variable\n");
            num_errors++;
        }
    }

    return num_errors;
}

static bool FindFunctionInModule (ConstString &mangled_name,
                                  llvm::Module *module,
                                  const char *orig_name)
{
    for (llvm::Module::iterator fi = module->getFunctionList().begin(), fe = module->getFunctionList().end();
         fi != fe;
         ++fi)
    {
        if (fi->getName().str().find(orig_name) != std::string::npos)
        {
            mangled_name.SetCString(fi->getName().str().c_str());
            return true;
        }
    }

    return false;
}

Error
ClangExpressionParser::PrepareForExecution (lldb::addr_t &func_addr,
                                            lldb::addr_t &func_end,
                                            lldb::IRExecutionUnitSP &execution_unit_sp,
                                            ExecutionContext &exe_ctx,
                                            bool &can_interpret,
                                            ExecutionPolicy execution_policy)
{
	func_addr = LLDB_INVALID_ADDRESS;
	func_end = LLDB_INVALID_ADDRESS;
    Log *log(lldb_private::GetLogIfAllCategoriesSet (LIBLLDB_LOG_EXPRESSIONS));

    Error err;

    std::unique_ptr<llvm::Module> llvm_module_ap (m_code_generator->ReleaseModule());

    if (!llvm_module_ap.get())
    {
        err.SetErrorToGenericError();
        err.SetErrorString("IR doesn't contain a module");
        return err;
    }

    // Find the actual name of the function (it's often mangled somehow)

    ConstString function_name;

    if (!FindFunctionInModule(function_name, llvm_module_ap.get(), m_expr.FunctionName()))
    {
        err.SetErrorToGenericError();
        err.SetErrorStringWithFormat("Couldn't find %s() in the module", m_expr.FunctionName());
        return err;
    }
    else
    {
        if (log)
            log->Printf("Found function %s for %s", function_name.AsCString(), m_expr.FunctionName());
    }
    
    SymbolContext sc;
    
    if (lldb::StackFrameSP frame_sp = exe_ctx.GetFrameSP())
    {
        sc = frame_sp->GetSymbolContext(lldb::eSymbolContextEverything);
    }
    else if (lldb::TargetSP target_sp = exe_ctx.GetTargetSP())
    {
        sc.target_sp = target_sp;
    }

    execution_unit_sp.reset(new IRExecutionUnit (m_llvm_context, // handed off here
                                                 llvm_module_ap, // handed off here
                                                 function_name,
                                                 exe_ctx.GetTargetSP(),
                                                 sc,
                                                 m_compiler->getTargetOpts().Features));

    ClangExpressionHelper *type_system_helper = dyn_cast<ClangExpressionHelper>(m_expr.GetTypeSystemHelper());
    ClangExpressionDeclMap *decl_map = type_system_helper->DeclMap(); // result can be NULL

    if (decl_map)
    {
        Stream *error_stream = NULL;
        Target *target = exe_ctx.GetTargetPtr();
        if (target)
            error_stream = target->GetDebugger().GetErrorFile().get();

        IRForTarget ir_for_target(decl_map,
                                  m_expr.NeedsVariableResolution(),
                                  *execution_unit_sp,
                                  error_stream,
                                  function_name.AsCString());

        bool ir_can_run = ir_for_target.runOnModule(*execution_unit_sp->GetModule());

        Error interpret_error;
        Process *process = exe_ctx.GetProcessPtr();

        bool interpret_function_calls = !process ? false : process->CanInterpretFunctionCalls();
        can_interpret = IRInterpreter::CanInterpret(*execution_unit_sp->GetModule(), *execution_unit_sp->GetFunction(), interpret_error, interpret_function_calls);


        if (!ir_can_run)
        {
            err.SetErrorString("The expression could not be prepared to run in the target");
            return err;
        }

        if (!can_interpret && execution_policy == eExecutionPolicyNever)
        {
            err.SetErrorStringWithFormat("Can't run the expression locally: %s", interpret_error.AsCString());
            return err;
        }

        if (!process && execution_policy == eExecutionPolicyAlways)
        {
            err.SetErrorString("Expression needed to run in the target, but the target can't be run");
            return err;
        }

        if (execution_policy == eExecutionPolicyAlways || !can_interpret)
        {
            if (m_expr.NeedsValidation() && process)
            {
                if (!process->GetDynamicCheckers())
                {
                    DynamicCheckerFunctions *dynamic_checkers = new DynamicCheckerFunctions();

                    StreamString install_errors;

                    if (!dynamic_checkers->Install(install_errors, exe_ctx))
                    {
                        if (install_errors.GetString().empty())
                            err.SetErrorString ("couldn't install checkers, unknown error");
                        else
                            err.SetErrorString (install_errors.GetString().c_str());

                        return err;
                    }

                    process->SetDynamicCheckers(dynamic_checkers);

                    if (log)
                        log->Printf("== [ClangUserExpression::Evaluate] Finished installing dynamic checkers ==");
                }

                IRDynamicChecks ir_dynamic_checks(*process->GetDynamicCheckers(), function_name.AsCString());

                if (!ir_dynamic_checks.runOnModule(*execution_unit_sp->GetModule()))
                {
                    err.SetErrorToGenericError();
                    err.SetErrorString("Couldn't add dynamic checks to the expression");
                    return err;
                }
            }

            execution_unit_sp->GetRunnableInfo(err, func_addr, func_end);
        }
    }
    else
    {
        execution_unit_sp->GetRunnableInfo(err, func_addr, func_end);
    }

    return err;
}