// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

#include "vm/compiler/jit/compiler.h"

#include "vm/compiler/assembler/assembler.h"

#include "vm/code_patcher.h"
#include "vm/compiler/aot/precompiler.h"
#include "vm/compiler/assembler/disassembler.h"
#include "vm/compiler/backend/block_scheduler.h"
#include "vm/compiler/backend/branch_optimizer.h"
#include "vm/compiler/backend/constant_propagator.h"
#include "vm/compiler/backend/flow_graph.h"
#include "vm/compiler/backend/flow_graph_compiler.h"
#include "vm/compiler/backend/il_printer.h"
#include "vm/compiler/backend/inliner.h"
#include "vm/compiler/backend/linearscan.h"
#include "vm/compiler/backend/range_analysis.h"
#include "vm/compiler/backend/redundancy_elimination.h"
#include "vm/compiler/backend/type_propagator.h"
#include "vm/compiler/cha.h"
#include "vm/compiler/compiler_pass.h"
#include "vm/compiler/compiler_state.h"
#include "vm/compiler/frontend/bytecode_reader.h"
#include "vm/compiler/frontend/flow_graph_builder.h"
#include "vm/compiler/frontend/kernel_to_il.h"
#include "vm/compiler/jit/jit_call_specializer.h"
#include "vm/dart_entry.h"
#include "vm/debugger.h"
#include "vm/deopt_instructions.h"
#include "vm/exceptions.h"
#include "vm/flags.h"
#include "vm/kernel.h"
#include "vm/kernel_loader.h"  // For kernel::ParseStaticFieldInitializer.
#include "vm/longjump.h"
#include "vm/object.h"
#include "vm/object_store.h"
#include "vm/os.h"
#include "vm/parser.h"
#include "vm/regexp_assembler.h"
#include "vm/regexp_parser.h"
#include "vm/runtime_entry.h"
#include "vm/symbols.h"
#include "vm/tags.h"
#include "vm/thread_registry.h"
#include "vm/timeline.h"
#include "vm/timer.h"

namespace dart {

DEFINE_FLAG(
    int,
    max_deoptimization_counter_threshold,
    16,
    "How many times we allow deoptimization before we disallow optimization.");
DEFINE_FLAG(charp, optimization_filter, NULL, "Optimize only named function");
DEFINE_FLAG(bool, print_flow_graph, false, "Print the IR flow graph.");
DEFINE_FLAG(bool,
            print_flow_graph_optimized,
            false,
            "Print the IR flow graph when optimizing.");
DEFINE_FLAG(bool,
            print_ic_data_map,
            false,
            "Print the deopt-id to ICData map in optimizing compiler.");
DEFINE_FLAG(bool, print_code_source_map, false, "Print code source map.");
DEFINE_FLAG(bool,
            stress_test_background_compilation,
            false,
            "Keep background compiler running all the time");
DEFINE_FLAG(bool,
            stop_on_excessive_deoptimization,
            false,
            "Debugging: stops program if deoptimizing same function too often");
DEFINE_FLAG(bool, trace_compiler, false, "Trace compiler operations.");
DEFINE_FLAG(bool,
            trace_failed_optimization_attempts,
            false,
            "Traces all failed optimization attempts");
DEFINE_FLAG(bool,
            trace_optimizing_compiler,
            false,
            "Trace only optimizing compiler operations.");
DEFINE_FLAG(bool, trace_bailout, false, "Print bailout from ssa compiler.");

DECLARE_FLAG(bool, enable_interpreter);
DECLARE_FLAG(bool, huge_method_cutoff_in_code_size);
DECLARE_FLAG(bool, trace_failed_optimization_attempts);
DECLARE_FLAG(bool, unbox_numeric_fields);

static void PrecompilationModeHandler(bool value) {
  if (value) {
#if defined(TARGET_ARCH_IA32)
    FATAL("Precompilation not supported on IA32");
#endif

    FLAG_background_compilation = false;
    FLAG_enable_mirrors = false;
    // TODO(dacoharkes): Ffi support in AOT
    // https://github.com/dart-lang/sdk/issues/35765
    FLAG_enable_ffi = false;
    FLAG_fields_may_be_reset = true;
    FLAG_interpret_irregexp = true;
    FLAG_lazy_dispatchers = false;
    FLAG_link_natives_lazily = true;
    FLAG_optimization_counter_threshold = -1;
    FLAG_polymorphic_with_deopt = false;
    FLAG_precompiled_mode = true;
    FLAG_reorder_basic_blocks = true;
    FLAG_use_field_guards = false;
    FLAG_use_cha_deopt = false;

#if !defined(DART_PRECOMPILED_RUNTIME)
    // Not present with DART_PRECOMPILED_RUNTIME
    FLAG_unbox_numeric_fields = false;
#endif

#if !defined(PRODUCT) && !defined(DART_PRECOMPILED_RUNTIME)
    // Set flags affecting runtime accordingly for gen_snapshot.
    // These flags are constants with PRODUCT and DART_PRECOMPILED_RUNTIME.
    FLAG_deoptimize_alot = false;  // Used in some tests.
    FLAG_deoptimize_every = 0;     // Used in some tests.
    FLAG_load_deferred_eagerly = true;
    FLAG_use_osr = false;
#endif
  }
}

DEFINE_FLAG_HANDLER(PrecompilationModeHandler,
                    precompilation,
                    "Precompilation mode");

#ifndef DART_PRECOMPILED_RUNTIME

void DartCompilationPipeline::ParseFunction(ParsedFunction* parsed_function) {
  // Nothing to do here.
}

FlowGraph* DartCompilationPipeline::BuildFlowGraph(
    Zone* zone,
    ParsedFunction* parsed_function,
    ZoneGrowableArray<const ICData*>* ic_data_array,
    intptr_t osr_id,
    bool optimized) {
  kernel::FlowGraphBuilder builder(parsed_function, ic_data_array,
                                   /* not building var desc */ NULL,
                                   /* not inlining */ NULL, optimized, osr_id);
  FlowGraph* graph = builder.BuildGraph();
  ASSERT(graph != NULL);
  return graph;
}

void DartCompilationPipeline::FinalizeCompilation(FlowGraph* flow_graph) {}

void IrregexpCompilationPipeline::ParseFunction(
    ParsedFunction* parsed_function) {
  VMTagScope tagScope(parsed_function->thread(),
                      VMTag::kCompileParseRegExpTagId);
  Zone* zone = parsed_function->zone();
  RegExp& regexp = RegExp::Handle(parsed_function->function().regexp());

  const String& pattern = String::Handle(regexp.pattern());

  RegExpCompileData* compile_data = new (zone) RegExpCompileData();
  // Parsing failures are handled in the RegExp factory constructor.
  RegExpParser::ParseRegExp(pattern, regexp.flags(), compile_data);

  regexp.set_num_bracket_expressions(compile_data->capture_count);
  regexp.set_capture_name_map(compile_data->capture_name_map);
  if (compile_data->simple) {
    regexp.set_is_simple();
  } else {
    regexp.set_is_complex();
  }

  parsed_function->SetRegExpCompileData(compile_data);

  // Variables are allocated after compilation.
}

FlowGraph* IrregexpCompilationPipeline::BuildFlowGraph(
    Zone* zone,
    ParsedFunction* parsed_function,
    ZoneGrowableArray<const ICData*>* ic_data_array,
    intptr_t osr_id,
    bool optimized) {
  // Compile to the dart IR.
  RegExpEngine::CompilationResult result =
      RegExpEngine::CompileIR(parsed_function->regexp_compile_data(),
                              parsed_function, *ic_data_array, osr_id);
  backtrack_goto_ = result.backtrack_goto;

  // Allocate variables now that we know the number of locals.
  parsed_function->AllocateIrregexpVariables(result.num_stack_locals);

  // When compiling for OSR, use a depth first search to find the OSR
  // entry and make graph entry jump to it instead of normal entry.
  // Catch entries are always considered reachable, even if they
  // become unreachable after OSR.
  if (osr_id != Compiler::kNoOSRDeoptId) {
    result.graph_entry->RelinkToOsrEntry(zone, result.num_blocks);
  }
  PrologueInfo prologue_info(-1, -1);
  return new (zone) FlowGraph(*parsed_function, result.graph_entry,
                              result.num_blocks, prologue_info);
}

void IrregexpCompilationPipeline::FinalizeCompilation(FlowGraph* flow_graph) {
  backtrack_goto_->ComputeOffsetTable();
}

CompilationPipeline* CompilationPipeline::New(Zone* zone,
                                              const Function& function) {
  if (function.IsIrregexpFunction()) {
    return new (zone) IrregexpCompilationPipeline();
  } else {
    return new (zone) DartCompilationPipeline();
  }
}

// Compile a function. Should call only if the function has not been compiled.
//   Arg0: function object.
DEFINE_RUNTIME_ENTRY(CompileFunction, 1) {
  ASSERT(thread->IsMutatorThread());
  const Function& function = Function::CheckedHandle(zone, arguments.ArgAt(0));
  Object& result = Object::Handle(zone);

  if (FLAG_enable_interpreter && function.IsBytecodeAllowed(zone)) {
    if (!function.HasBytecode()) {
      result = kernel::BytecodeReader::ReadFunctionBytecode(thread, function);
      if (!result.IsNull()) {
        Exceptions::PropagateError(Error::Cast(result));
      }
    }
    if (function.HasBytecode()) {
      // If interpreter is enabled and there is bytecode, LazyCompile stub
      // (which calls CompileFunction) should proceed to InterpretCall in order
      // to enter interpreter. In such case, compilation is postponed and
      // triggered by interpreter later via OptimizeInvokedFunction.
      return;
    }
    // No bytecode, fall back to compilation.
  } else {
    ASSERT(!function.HasCode());
  }

  result = Compiler::CompileFunction(thread, function);
  if (result.IsError()) {
    if (result.IsLanguageError()) {
      Exceptions::ThrowCompileTimeError(LanguageError::Cast(result));
      UNREACHABLE();
    }
    Exceptions::PropagateError(Error::Cast(result));
  }
}

bool Compiler::CanOptimizeFunction(Thread* thread, const Function& function) {
#if !defined(PRODUCT)
  if (Debugger::IsDebugging(thread, function)) {
    // We cannot set breakpoints and single step in optimized code,
    // so do not optimize the function. Bump usage counter down to avoid
    // repeatedly entering the runtime for an optimization attempt.
    function.SetUsageCounter(0);

    // If the optimization counter = 1, the unoptimized code will come back here
    // immediately, causing an infinite compilation loop. The compiler raises
    // the threshold for functions with breakpoints, so we drop the unoptimized
    // to force it to be recompiled.
    if (thread->isolate()->CanOptimizeImmediately()) {
      function.ClearCode();
    }
    return false;
  }
#endif
  if (function.deoptimization_counter() >=
      FLAG_max_deoptimization_counter_threshold) {
    if (FLAG_trace_failed_optimization_attempts ||
        FLAG_stop_on_excessive_deoptimization) {
      THR_Print("Too many deoptimizations: %s\n",
                function.ToFullyQualifiedCString());
      if (FLAG_stop_on_excessive_deoptimization) {
        FATAL("Stop on excessive deoptimization");
      }
    }
    // The function will not be optimized any longer. This situation can occur
    // mostly with small optimization counter thresholds.
    function.SetIsOptimizable(false);
    function.SetUsageCounter(INT_MIN);
    return false;
  }
  if (FLAG_optimization_filter != NULL) {
    // FLAG_optimization_filter is a comma-separated list of strings that are
    // matched against the fully-qualified function name.
    char* save_ptr;  // Needed for strtok_r.
    const char* function_name = function.ToFullyQualifiedCString();
    intptr_t len = strlen(FLAG_optimization_filter) + 1;  // Length with \0.
    char* filter = new char[len];
    strncpy(filter, FLAG_optimization_filter, len);  // strtok modifies arg 1.
    char* token = strtok_r(filter, ",", &save_ptr);
    bool found = false;
    while (token != NULL) {
      if (strstr(function_name, token) != NULL) {
        found = true;
        break;
      }
      token = strtok_r(NULL, ",", &save_ptr);
    }
    delete[] filter;
    if (!found) {
      function.SetUsageCounter(INT_MIN);
      return false;
    }
  }
  if (!function.IsOptimizable()) {
    // Huge methods (code size above --huge_method_cutoff_in_code_size) become
    // non-optimizable only after the code has been generated.
    if (FLAG_trace_failed_optimization_attempts) {
      THR_Print("Not optimizable: %s\n", function.ToFullyQualifiedCString());
    }
    function.SetUsageCounter(INT_MIN);
    return false;
  }
  return true;
}

bool Compiler::IsBackgroundCompilation() {
  // For now: compilation in non mutator thread is the background compoilation.
  return !Thread::Current()->IsMutatorThread();
}

class CompileParsedFunctionHelper : public ValueObject {
 public:
  CompileParsedFunctionHelper(ParsedFunction* parsed_function,
                              bool optimized,
                              intptr_t osr_id)
      : parsed_function_(parsed_function),
        optimized_(optimized),
        osr_id_(osr_id),
        thread_(Thread::Current()),
        loading_invalidation_gen_at_start_(
            isolate()->loading_invalidation_gen()) {}

  RawCode* Compile(CompilationPipeline* pipeline);

 private:
  ParsedFunction* parsed_function() const { return parsed_function_; }
  bool optimized() const { return optimized_; }
  intptr_t osr_id() const { return osr_id_; }
  Thread* thread() const { return thread_; }
  Isolate* isolate() const { return thread_->isolate(); }
  intptr_t loading_invalidation_gen_at_start() const {
    return loading_invalidation_gen_at_start_;
  }
  RawCode* FinalizeCompilation(Assembler* assembler,
                               FlowGraphCompiler* graph_compiler,
                               FlowGraph* flow_graph);
  void CheckIfBackgroundCompilerIsBeingStopped(bool optimizing_compiler);

  ParsedFunction* parsed_function_;
  const bool optimized_;
  const intptr_t osr_id_;
  Thread* const thread_;
  const intptr_t loading_invalidation_gen_at_start_;

  DISALLOW_COPY_AND_ASSIGN(CompileParsedFunctionHelper);
};

RawCode* CompileParsedFunctionHelper::FinalizeCompilation(
    Assembler* assembler,
    FlowGraphCompiler* graph_compiler,
    FlowGraph* flow_graph) {
  ASSERT(!FLAG_precompiled_mode);
  const Function& function = parsed_function()->function();
  Zone* const zone = thread()->zone();

  // CreateDeoptInfo uses the object pool and needs to be done before
  // FinalizeCode.
  Array& deopt_info_array = Array::Handle(zone, Object::empty_array().raw());
  if (!function.ForceOptimize()) {
    deopt_info_array = graph_compiler->CreateDeoptInfo(assembler);
  }

  // Allocates instruction object. Since this occurs only at safepoint,
  // there can be no concurrent access to the instruction page.
  Code& code = Code::Handle(Code::FinalizeCode(
      graph_compiler, assembler, Code::PoolAttachment::kAttachPool, optimized(),
      /*stats=*/nullptr));
  code.set_is_optimized(optimized());
  code.set_owner(function);

  if (!function.IsOptimizable()) {
    // A function with huge unoptimized code can become non-optimizable
    // after generating unoptimized code.
    function.SetUsageCounter(INT_MIN);
  }

  graph_compiler->FinalizePcDescriptors(code);
  code.set_deopt_info_array(deopt_info_array);

  graph_compiler->FinalizeStackMaps(code);
  graph_compiler->FinalizeVarDescriptors(code);
  graph_compiler->FinalizeExceptionHandlers(code);
  graph_compiler->FinalizeCatchEntryMovesMap(code);
  graph_compiler->FinalizeStaticCallTargetsTable(code);
  graph_compiler->FinalizeCodeSourceMap(code);

  if (function.ForceOptimize()) {
    ASSERT(optimized() && thread()->IsMutatorThread());
    code.set_is_optimized(false);
    function.AttachCode(code);
    function.set_unoptimized_code(code);
    function.SetWasCompiled(true);
  } else if (optimized()) {
    // Installs code while at safepoint.
    if (thread()->IsMutatorThread()) {
      const bool is_osr = osr_id() != Compiler::kNoOSRDeoptId;
      if (!is_osr) {
        function.InstallOptimizedCode(code);
      }
      ASSERT(code.owner() == function.raw());
    } else {
      // Background compilation.
      // Before installing code check generation counts if the code may
      // have become invalid.
      const bool trace_compiler =
          FLAG_trace_compiler || FLAG_trace_optimizing_compiler;
      bool code_is_valid = true;
      if (!flow_graph->parsed_function().guarded_fields()->is_empty()) {
        const ZoneGrowableArray<const Field*>& guarded_fields =
            *flow_graph->parsed_function().guarded_fields();
        Field& original = Field::Handle();
        for (intptr_t i = 0; i < guarded_fields.length(); i++) {
          const Field& field = *guarded_fields[i];
          ASSERT(!field.IsOriginal());
          original = field.Original();
          if (!field.IsConsistentWith(original)) {
            code_is_valid = false;
            if (trace_compiler) {
              THR_Print("--> FAIL: Field %s guarded state changed.",
                        field.ToCString());
            }
            break;
          }
        }
      }
      if (loading_invalidation_gen_at_start() !=
          isolate()->loading_invalidation_gen()) {
        code_is_valid = false;
        if (trace_compiler) {
          THR_Print("--> FAIL: Loading invalidation.");
        }
      }
      if (!thread()
               ->compiler_state()
               .cha()
               .IsConsistentWithCurrentHierarchy()) {
        code_is_valid = false;
        if (trace_compiler) {
          THR_Print("--> FAIL: Class hierarchy has new subclasses.");
        }
      }

      // Setting breakpoints at runtime could make a function non-optimizable.
      if (code_is_valid && Compiler::CanOptimizeFunction(thread(), function)) {
        const bool is_osr = osr_id() != Compiler::kNoOSRDeoptId;
        ASSERT(!is_osr);  // OSR is not compiled in background.
        function.InstallOptimizedCode(code);
      } else {
        code = Code::null();
      }
      if (function.usage_counter() < 0) {
        // Reset to 0 so that it can be recompiled if needed.
        if (code_is_valid) {
          function.SetUsageCounter(0);
        } else {
          // Trigger another optimization pass soon.
          function.SetUsageCounter(FLAG_optimization_counter_threshold - 100);
        }
      }
    }

    if (!code.IsNull()) {
      // The generated code was compiled under certain assumptions about
      // class hierarchy and field types. Register these dependencies
      // to ensure that the code will be deoptimized if they are violated.
      thread()->compiler_state().cha().RegisterDependencies(code);

      const ZoneGrowableArray<const Field*>& guarded_fields =
          *flow_graph->parsed_function().guarded_fields();
      Field& field = Field::Handle();
      for (intptr_t i = 0; i < guarded_fields.length(); i++) {
        field = guarded_fields[i]->Original();
        field.RegisterDependentCode(code);
      }
    }
  } else {  // not optimized.
    if (function.ic_data_array() == Array::null()) {
      function.SaveICDataMap(
          graph_compiler->deopt_id_to_ic_data(),
          Array::Handle(zone, graph_compiler->edge_counters_array()));
    }
    function.set_unoptimized_code(code);
    function.AttachCode(code);
    function.SetWasCompiled(true);
    if (function.IsOptimizable() && (function.usage_counter() < 0)) {
      // While doing compilation in background, usage counter is set
      // to INT_MIN. Reset counter so that function can be optimized further.
      function.SetUsageCounter(0);
    }
  }
  if (parsed_function()->HasDeferredPrefixes()) {
    ASSERT(!FLAG_load_deferred_eagerly);
    ZoneGrowableArray<const LibraryPrefix*>* prefixes =
        parsed_function()->deferred_prefixes();
    for (intptr_t i = 0; i < prefixes->length(); i++) {
      (*prefixes)[i]->RegisterDependentCode(code);
    }
  }
  return code.raw();
}

void CompileParsedFunctionHelper::CheckIfBackgroundCompilerIsBeingStopped(
    bool optimizing_compiler) {
  ASSERT(Compiler::IsBackgroundCompilation());
  if (optimizing_compiler) {
    if (!isolate()->optimizing_background_compiler()->is_running()) {
      // The background compiler is being stopped.
      Compiler::AbortBackgroundCompilation(
          DeoptId::kNone, "Optimizing Background compilation is being stopped");
    }
  } else {
    if (FLAG_enable_interpreter &&
        !isolate()->background_compiler()->is_running()) {
      // The background compiler is being stopped.
      Compiler::AbortBackgroundCompilation(
          DeoptId::kNone, "Background compilation is being stopped");
    }
  }
}

// Return null if bailed out.
// If optimized_result_code is not NULL then it is caller's responsibility
// to install code.
RawCode* CompileParsedFunctionHelper::Compile(CompilationPipeline* pipeline) {
  ASSERT(!FLAG_precompiled_mode);
  const Function& function = parsed_function()->function();
  if (optimized() && !function.IsOptimizable()) {
    return Code::null();
  }
  Zone* const zone = thread()->zone();
  HANDLESCOPE(thread());

  // We may reattempt compilation if the function needs to be assembled using
  // far branches on ARM. In the else branch of the setjmp call, done is set to
  // false, and use_far_branches is set to true if there is a longjmp from the
  // ARM assembler. In all other paths through this while loop, done is set to
  // true. use_far_branches is always false on ia32 and x64.
  volatile bool done = false;
  // volatile because the variable may be clobbered by a longjmp.
  volatile bool use_far_branches = false;

  // In the JIT case we allow speculative inlining and have no need for a
  // blacklist, since we don't restart optimization.
  SpeculativeInliningPolicy speculative_policy(/* enable_blacklist= */ false);

  Code* volatile result = &Code::ZoneHandle(zone);
  while (!done) {
    *result = Code::null();
    LongJumpScope jump;
    if (setjmp(*jump.Set()) == 0) {
      FlowGraph* flow_graph = nullptr;
      ZoneGrowableArray<const ICData*>* ic_data_array = nullptr;

      CompilerState compiler_state(thread());

      {
        if (optimized()) {
          // In background compilation the deoptimization counter may have
          // already reached the limit.
          ASSERT(Compiler::IsBackgroundCompilation() ||
                 (function.deoptimization_counter() <
                  FLAG_max_deoptimization_counter_threshold));
        }

        // Extract type feedback before the graph is built, as the graph
        // builder uses it to attach it to nodes.
        ic_data_array = new (zone) ZoneGrowableArray<const ICData*>();

        // Clone ICData for background compilation so that it does not
        // change while compiling.
        const bool clone_ic_data = Compiler::IsBackgroundCompilation();
        function.RestoreICDataMap(ic_data_array, clone_ic_data);

        if (optimized()) {
          if (Compiler::IsBackgroundCompilation() &&
              (function.ic_data_array() == Array::null())) {
            Compiler::AbortBackgroundCompilation(
                DeoptId::kNone, "RestoreICDataMap: ICData array cleared.");
          }
        }

        if (FLAG_print_ic_data_map) {
          for (intptr_t i = 0; i < ic_data_array->length(); i++) {
            if ((*ic_data_array)[i] != NULL) {
              THR_Print("%" Pd " ", i);
              FlowGraphPrinter::PrintICData(*(*ic_data_array)[i]);
            }
          }
        }

        TIMELINE_DURATION(thread(), CompilerVerbose, "BuildFlowGraph");
        flow_graph = pipeline->BuildFlowGraph(
            zone, parsed_function(), ic_data_array, osr_id(), optimized());
      }

      const bool print_flow_graph =
          (FLAG_print_flow_graph ||
           (optimized() && FLAG_print_flow_graph_optimized)) &&
          FlowGraphPrinter::ShouldPrint(function);

      if (print_flow_graph && !optimized()) {
        FlowGraphPrinter::PrintGraph("Unoptimized Compilation", flow_graph);
      }

      BlockScheduler block_scheduler(flow_graph);
      const bool reorder_blocks =
          FlowGraph::ShouldReorderBlocks(function, optimized());
      if (reorder_blocks) {
        TIMELINE_DURATION(thread(), CompilerVerbose,
                          "BlockScheduler::AssignEdgeWeights");
        block_scheduler.AssignEdgeWeights();
      }

      CompilerPassState pass_state(thread(), flow_graph, &speculative_policy);
      pass_state.block_scheduler = &block_scheduler;
      pass_state.reorder_blocks = reorder_blocks;

      if (optimized()) {
        TIMELINE_DURATION(thread(), CompilerVerbose, "OptimizationPasses");

        pass_state.inline_id_to_function.Add(&function);
        // We do not add the token position now because we don't know the
        // position of the inlined call until later. A side effect of this
        // is that the length of |inline_id_to_function| is always larger
        // than the length of |inline_id_to_token_pos| by one.
        // Top scope function has no caller (-1). We do this because we expect
        // all token positions to be at an inlined call.
        pass_state.caller_inline_id.Add(-1);

        JitCallSpecializer call_specializer(flow_graph, &speculative_policy);
        pass_state.call_specializer = &call_specializer;

        CompilerPass::RunPipeline(CompilerPass::kJIT, &pass_state);
      }

      ASSERT(pass_state.inline_id_to_function.length() ==
             pass_state.caller_inline_id.length());
      ObjectPoolBuilder object_pool_builder;
      Assembler assembler(&object_pool_builder, use_far_branches);
      FlowGraphCompiler graph_compiler(
          &assembler, flow_graph, *parsed_function(), optimized(),
          &speculative_policy, pass_state.inline_id_to_function,
          pass_state.inline_id_to_token_pos, pass_state.caller_inline_id,
          ic_data_array);
      {
        TIMELINE_DURATION(thread(), CompilerVerbose, "CompileGraph");
        graph_compiler.CompileGraph();
        pipeline->FinalizeCompilation(flow_graph);
      }
      {
        TIMELINE_DURATION(thread(), CompilerVerbose, "FinalizeCompilation");
        if (thread()->IsMutatorThread()) {
          *result =
              FinalizeCompilation(&assembler, &graph_compiler, flow_graph);
        } else {
          // This part of compilation must be at a safepoint.
          // Stop mutator thread before creating the instruction object and
          // installing code.
          // Mutator thread may not run code while we are creating the
          // instruction object, since the creation of instruction object
          // changes code page access permissions (makes them temporary not
          // executable).
          {
            CheckIfBackgroundCompilerIsBeingStopped(optimized());
            SafepointOperationScope safepoint_scope(thread());
            // Do not Garbage collect during this stage and instead allow the
            // heap to grow.
            NoHeapGrowthControlScope no_growth_control;
            CheckIfBackgroundCompilerIsBeingStopped(optimized());
            *result =
                FinalizeCompilation(&assembler, &graph_compiler, flow_graph);
          }
        }

        // We notify code observers after finalizing the code in order to be
        // outside a [SafepointOperationScope].
        Code::NotifyCodeObservers(function, *result, optimized());
      }
      if (!result->IsNull()) {
#if !defined(PRODUCT)
        if (!function.HasOptimizedCode()) {
          isolate()->debugger()->NotifyCompilation(function);
        }
#endif
        if (FLAG_disassemble && FlowGraphPrinter::ShouldPrint(function)) {
          Disassembler::DisassembleCode(function, *result, optimized());
        } else if (FLAG_disassemble_optimized && optimized() &&
                   FlowGraphPrinter::ShouldPrint(function)) {
          Disassembler::DisassembleCode(function, *result, true);
        }
      }
      // Exit the loop and the function with the correct result value.
      done = true;
    } else {
      // We bailed out or we encountered an error.
      const Error& error = Error::Handle(thread()->StealStickyError());

      if (error.raw() == Object::branch_offset_error().raw()) {
        // Compilation failed due to an out of range branch offset in the
        // assembler. We try again (done = false) with far branches enabled.
        done = false;
        ASSERT(!use_far_branches);
        use_far_branches = true;
      } else if (error.raw() == Object::speculative_inlining_error().raw()) {
        // Can only happen with precompilation.
        UNREACHABLE();
      } else {
        // If the error isn't due to an out of range branch offset, we don't
        // try again (done = true).
        if (FLAG_trace_bailout) {
          THR_Print("%s\n", error.ToErrorCString());
        }
        if (!Compiler::IsBackgroundCompilation() && error.IsLanguageError() &&
            (LanguageError::Cast(error).kind() == Report::kBailout)) {
          // If is is not a background compilation, discard the error if it was
          // not a real error, but just a bailout. If we're it a background
          // compilation this will be dealt with in the caller.
        } else {
          // Otherwise, continue propagating unless we will try again.
          thread()->set_sticky_error(error);
        }
        done = true;
      }
    }
  }
  return result->raw();
}

static RawObject* CompileFunctionHelper(CompilationPipeline* pipeline,
                                        const Function& function,
                                        volatile bool optimized,
                                        intptr_t osr_id) {
  ASSERT(!FLAG_precompiled_mode);
  ASSERT(!optimized || function.WasCompiled() || function.ForceOptimize());
  if (function.ForceOptimize()) optimized = true;
  LongJumpScope jump;
  if (setjmp(*jump.Set()) == 0) {
    Thread* const thread = Thread::Current();
    Isolate* const isolate = thread->isolate();
    StackZone stack_zone(thread);
    Zone* const zone = stack_zone.GetZone();
    const bool trace_compiler =
        FLAG_trace_compiler || (FLAG_trace_optimizing_compiler && optimized);
    Timer per_compile_timer(trace_compiler, "Compilation time");
    per_compile_timer.Start();

    ParsedFunction* parsed_function = new (zone)
        ParsedFunction(thread, Function::ZoneHandle(zone, function.raw()));
    if (trace_compiler) {
      const intptr_t token_size =
          function.end_token_pos().Pos() - function.token_pos().Pos();
      THR_Print("Compiling %s%sfunction %s: '%s' @ token %s, size %" Pd "\n",
                (osr_id == Compiler::kNoOSRDeoptId ? "" : "osr "),
                (optimized ? "optimized " : ""),
                (Compiler::IsBackgroundCompilation() ? "(background)" : ""),
                function.ToFullyQualifiedCString(),
                function.token_pos().ToCString(), token_size);
    }
    // Makes sure no classes are loaded during parsing in background.
    const intptr_t loading_invalidation_gen_at_start =
        isolate->loading_invalidation_gen();
    {
      HANDLESCOPE(thread);
      pipeline->ParseFunction(parsed_function);
    }

    CompileParsedFunctionHelper helper(parsed_function, optimized, osr_id);

    if (Compiler::IsBackgroundCompilation()) {
      ASSERT(function.is_background_optimizable());
      if ((loading_invalidation_gen_at_start !=
           isolate->loading_invalidation_gen())) {
        // Loading occured while parsing. We need to abort here because state
        // changed while compiling.
        Compiler::AbortBackgroundCompilation(
            DeoptId::kNone,
            "Invalidated state during parsing because of script loading");
      }
    }

    const Code& result = Code::Handle(helper.Compile(pipeline));

    if (result.IsNull()) {
      const Error& error = Error::Handle(thread->StealStickyError());

      if (Compiler::IsBackgroundCompilation()) {
        // Try again later, background compilation may abort because of
        // state change during compilation.
        if (FLAG_trace_compiler) {
          THR_Print("Aborted background compilation: %s\n",
                    function.ToFullyQualifiedCString());
        }

        // We got an error during compilation.
        // If it was a bailout, then disable optimization.
        if (error.raw() == Object::background_compilation_error().raw()) {
          if (FLAG_trace_compiler) {
            THR_Print(
                "--> disabling background optimizations for '%s' (will "
                "try to re-compile on isolate thread again)\n",
                function.ToFullyQualifiedCString());
          }

          // Ensure we don't attempt to re-compile the function on the
          // background compiler.
          function.set_is_background_optimizable(false);

          // Trigger another optimization soon on the main thread.
          function.SetUsageCounter(optimized
                                       ? FLAG_optimization_counter_threshold
                                       : FLAG_compilation_counter_threshold);
          return Error::null();
        } else if (error.IsLanguageError() &&
                   LanguageError::Cast(error).kind() == Report::kBailout) {
          if (FLAG_trace_compiler) {
            THR_Print("--> disabling optimizations for '%s'\n",
                      function.ToFullyQualifiedCString());
          }
          function.SetIsOptimizable(false);
          return Error::null();
        } else {
          // The background compiler does not execute Dart code or handle
          // isolate messages.
          ASSERT(!error.IsUnwindError());
          return error.raw();
        }
      }
      if (optimized) {
        if (error.IsLanguageError() &&
            LanguageError::Cast(error).kind() == Report::kBailout) {
          // Functions which cannot deoptimize should never bail out.
          ASSERT(!function.ForceOptimize());
          // Optimizer bailed out. Disable optimizations and never try again.
          if (trace_compiler) {
            THR_Print("--> disabling optimizations for '%s'\n",
                      function.ToFullyQualifiedCString());
          } else if (FLAG_trace_failed_optimization_attempts) {
            THR_Print("Cannot optimize: %s\n",
                      function.ToFullyQualifiedCString());
          }
          function.SetIsOptimizable(false);
          return Error::null();
        }
        return error.raw();
      } else {
        ASSERT(!optimized);
        // The non-optimizing compiler can get an unhandled exception
        // due to OOM or Stack overflow errors, it should not however
        // bail out.
        ASSERT(error.IsUnhandledException() || error.IsUnwindError() ||
               (error.IsLanguageError() &&
                LanguageError::Cast(error).kind() != Report::kBailout));
        return error.raw();
      }
      UNREACHABLE();
    }

    per_compile_timer.Stop();

    if (trace_compiler) {
      THR_Print("--> '%s' entry: %#" Px " size: %" Pd " time: %" Pd64 " us\n",
                function.ToFullyQualifiedCString(),
                Code::Handle(function.CurrentCode()).PayloadStart(),
                Code::Handle(function.CurrentCode()).Size(),
                per_compile_timer.TotalElapsedTime());
    }

    return result.raw();
  } else {
    Thread* const thread = Thread::Current();
    StackZone stack_zone(thread);
    // We got an error during compilation or it is a bailout from background
    // compilation (e.g., during parsing with EnsureIsFinalized).
    const Error& error = Error::Handle(thread->StealStickyError());
    if (error.raw() == Object::background_compilation_error().raw()) {
      // Exit compilation, retry it later.
      if (FLAG_trace_bailout) {
        THR_Print("Aborted background compilation: %s\n",
                  function.ToFullyQualifiedCString());
      }
      return Object::null();
    }
    // Do not attempt to optimize functions that can cause errors.
    function.set_is_optimizable(false);
    return error.raw();
  }
  UNREACHABLE();
  return Object::null();
}

RawObject* Compiler::CompileFunction(Thread* thread, const Function& function) {
#if defined(DART_PRECOMPILER) && !defined(TARGET_ARCH_DBC) &&                  \
    !defined(TARGET_ARCH_IA32)
  if (FLAG_precompiled_mode) {
    return Precompiler::CompileFunction(
        /* precompiler = */ NULL, thread, thread->zone(), function);
  }
#endif

  Isolate* isolate = thread->isolate();
  if (!isolate->compilation_allowed()) {
    FATAL3("Precompilation missed function %s (%s, %s)\n",
           function.ToLibNamePrefixedQualifiedCString(),
           function.token_pos().ToCString(),
           Function::KindToCString(function.kind()));
  }

  VMTagScope tagScope(thread, VMTag::kCompileUnoptimizedTagId);
#if defined(SUPPORT_TIMELINE)
  const char* event_name;
  if (IsBackgroundCompilation()) {
    event_name = "CompileFunctionUnoptimizedBackground";
  } else {
    event_name = "CompileFunction";
  }
  TIMELINE_FUNCTION_COMPILATION_DURATION(thread, event_name, function);
#endif  // defined(SUPPORT_TIMELINE)

  CompilationPipeline* pipeline =
      CompilationPipeline::New(thread->zone(), function);

  const bool optimized = function.ForceOptimize();
  return CompileFunctionHelper(pipeline, function, optimized, kNoOSRDeoptId);
}

RawError* Compiler::EnsureUnoptimizedCode(Thread* thread,
                                          const Function& function) {
  if (function.unoptimized_code() != Object::null()) {
    return Error::null();
  }
  Code& original_code = Code::ZoneHandle(thread->zone());
  if (function.HasCode()) {
    original_code = function.CurrentCode();
  }
  CompilationPipeline* pipeline =
      CompilationPipeline::New(thread->zone(), function);
  const Object& result = Object::Handle(
      CompileFunctionHelper(pipeline, function, false, /* not optimized */
                            kNoOSRDeoptId));
  if (result.IsError()) {
    return Error::Cast(result).raw();
  }
  // Since CompileFunctionHelper replaces the current code, re-attach the
  // the original code if the function was already compiled.
  if (!original_code.IsNull() && result.raw() == function.CurrentCode() &&
      !original_code.IsDisabled()) {
    function.AttachCode(original_code);
  }
  ASSERT(function.unoptimized_code() != Object::null());
  ASSERT(function.unoptimized_code() == result.raw());
  if (FLAG_trace_compiler) {
    THR_Print("Ensure unoptimized code for %s\n", function.ToCString());
  }
  return Error::null();
}

RawObject* Compiler::CompileOptimizedFunction(Thread* thread,
                                              const Function& function,
                                              intptr_t osr_id) {
  VMTagScope tagScope(thread, VMTag::kCompileOptimizedTagId);
#if defined(SUPPORT_TIMELINE)
  const char* event_name;
  if (osr_id != kNoOSRDeoptId) {
    event_name = "CompileFunctionOptimizedOSR";
  } else if (IsBackgroundCompilation()) {
    event_name = "CompileFunctionOptimizedBackground";
  } else {
    event_name = "CompileFunctionOptimized";
  }
  TIMELINE_FUNCTION_COMPILATION_DURATION(thread, event_name, function);
#endif  // defined(SUPPORT_TIMELINE)

  ASSERT(function.ShouldCompilerOptimize());

  CompilationPipeline* pipeline =
      CompilationPipeline::New(thread->zone(), function);
  return CompileFunctionHelper(pipeline, function, /* optimized = */ true,
                               osr_id);
}

void Compiler::ComputeLocalVarDescriptors(const Code& code) {
  ASSERT(!code.is_optimized());
  const Function& function = Function::Handle(code.function());
  ASSERT(code.var_descriptors() == Object::null());
  // IsIrregexpFunction have eager var descriptors generation.
  ASSERT(!function.IsIrregexpFunction());
  if (function.is_declared_in_bytecode()) {
    auto& var_descs = LocalVarDescriptors::Handle();
    if (function.HasBytecode()) {
      const auto& bytecode = Bytecode::Handle(function.bytecode());
      var_descs = bytecode.GetLocalVarDescriptors();
    } else {
      var_descs = Object::empty_var_descriptors().raw();
    }
    code.set_var_descriptors(var_descs);
    return;
  }
  // In background compilation, parser can produce 'errors": bailouts
  // if state changed while compiling in background.
  CompilerState state(Thread::Current());
  LongJumpScope jump;
  if (setjmp(*jump.Set()) == 0) {
    ParsedFunction* parsed_function = new ParsedFunction(
        Thread::Current(), Function::ZoneHandle(function.raw()));
    ZoneGrowableArray<const ICData*>* ic_data_array =
        new ZoneGrowableArray<const ICData*>();
    ZoneGrowableArray<intptr_t>* context_level_array =
        new ZoneGrowableArray<intptr_t>();

    parsed_function->EnsureKernelScopes();
    kernel::FlowGraphBuilder builder(
        parsed_function, ic_data_array, context_level_array,
        /* not inlining */ NULL, false, Compiler::kNoOSRDeoptId);
    builder.BuildGraph();

    const LocalVarDescriptors& var_descs =
        LocalVarDescriptors::Handle(parsed_function->scope()->GetVarDescriptors(
            function, context_level_array));
    ASSERT(!var_descs.IsNull());
    code.set_var_descriptors(var_descs);
  } else {
    // Only possible with background compilation.
    ASSERT(Compiler::IsBackgroundCompilation());
  }
}

RawError* Compiler::CompileAllFunctions(const Class& cls) {
  Thread* thread = Thread::Current();
  Zone* zone = thread->zone();
  Object& result = Object::Handle(zone);
  Array& functions = Array::Handle(zone, cls.functions());
  Function& func = Function::Handle(zone);
  // Class dynamic lives in the vm isolate. Its array fields cannot be set to
  // an empty array.
  if (functions.IsNull()) {
    ASSERT(cls.IsDynamicClass());
    return Error::null();
  }
  // Compile all the regular functions.
  for (int i = 0; i < functions.Length(); i++) {
    func ^= functions.At(i);
    ASSERT(!func.IsNull());
    if (!func.HasCode() && !func.is_abstract() &&
        !func.IsRedirectingFactory()) {
      result = CompileFunction(thread, func);
      if (result.IsError()) {
        return Error::Cast(result).raw();
      }
      ASSERT(!result.IsNull());
    }
  }
  return Error::null();
}

RawError* Compiler::ReadAllBytecode(const Class& cls) {
  Thread* thread = Thread::Current();
  ASSERT(thread->IsMutatorThread());
  Zone* zone = thread->zone();
  Error& error = Error::Handle(zone, cls.EnsureIsFinalized(thread));
  ASSERT(error.IsNull());
  Array& functions = Array::Handle(zone, cls.functions());
  Function& func = Function::Handle(zone);
  // Class dynamic lives in the vm isolate. Its array fields cannot be set to
  // an empty array.
  if (functions.IsNull()) {
    ASSERT(cls.IsDynamicClass());
    return Error::null();
  }
  // Compile all the regular functions.
  for (int i = 0; i < functions.Length(); i++) {
    func ^= functions.At(i);
    ASSERT(!func.IsNull());
    if (func.IsBytecodeAllowed(zone) && !func.HasBytecode() &&
        !func.HasCode()) {
      RawError* error =
          kernel::BytecodeReader::ReadFunctionBytecode(thread, func);
      if (error != Error::null()) {
        return error;
      }
    }
  }
  return Error::null();
}

void Compiler::AbortBackgroundCompilation(intptr_t deopt_id, const char* msg) {
  if (FLAG_trace_compiler) {
    THR_Print("ABORT background compilation: %s\n", msg);
  }
#if !defined(PRODUCT)
  TimelineStream* stream = Timeline::GetCompilerStream();
  ASSERT(stream != NULL);
  TimelineEvent* event = stream->StartEvent();
  if (event != NULL) {
    event->Instant("AbortBackgroundCompilation");
    event->SetNumArguments(1);
    event->CopyArgument(0, "reason", msg);
    event->Complete();
  }
#endif  // !defined(PRODUCT)
  ASSERT(Compiler::IsBackgroundCompilation());
  Thread::Current()->long_jump_base()->Jump(
      deopt_id, Object::background_compilation_error());
}

// C-heap allocated background compilation queue element.
class QueueElement {
 public:
  explicit QueueElement(const Function& function)
      : next_(NULL), function_(function.raw()) {}

  virtual ~QueueElement() {
    next_ = NULL;
    function_ = Function::null();
  }

  RawFunction* Function() const { return function_; }

  void set_next(QueueElement* elem) { next_ = elem; }
  QueueElement* next() const { return next_; }

  RawObject* function() const { return function_; }
  RawObject** function_ptr() {
    return reinterpret_cast<RawObject**>(&function_);
  }

 private:
  QueueElement* next_;
  RawFunction* function_;

  DISALLOW_COPY_AND_ASSIGN(QueueElement);
};

// Allocated in C-heap. Handles both input and output of background compilation.
// It implements a FIFO queue, using Peek, Add, Remove operations.
class BackgroundCompilationQueue {
 public:
  BackgroundCompilationQueue() : first_(NULL), last_(NULL) {}
  virtual ~BackgroundCompilationQueue() { Clear(); }

  void VisitObjectPointers(ObjectPointerVisitor* visitor) {
    ASSERT(visitor != NULL);
    QueueElement* p = first_;
    while (p != NULL) {
      visitor->VisitPointer(p->function_ptr());
      p = p->next();
    }
  }

  bool IsEmpty() const { return first_ == NULL; }

  void Add(QueueElement* value) {
    ASSERT(value != NULL);
    ASSERT(value->next() == NULL);
    if (first_ == NULL) {
      first_ = value;
      ASSERT(last_ == NULL);
    } else {
      ASSERT(last_ != NULL);
      last_->set_next(value);
    }
    last_ = value;
    ASSERT(first_ != NULL && last_ != NULL);
  }

  QueueElement* Peek() const { return first_; }

  RawFunction* PeekFunction() const {
    QueueElement* e = Peek();
    if (e == NULL) {
      return Function::null();
    } else {
      return e->Function();
    }
  }

  QueueElement* Remove() {
    ASSERT(first_ != NULL);
    QueueElement* result = first_;
    first_ = first_->next();
    if (first_ == NULL) {
      last_ = NULL;
    }
    return result;
  }

  bool ContainsObj(const Object& obj) const {
    QueueElement* p = first_;
    while (p != NULL) {
      if (p->function() == obj.raw()) {
        return true;
      }
      p = p->next();
    }
    return false;
  }

  void Clear() {
    while (!IsEmpty()) {
      QueueElement* e = Remove();
      delete e;
    }
    ASSERT((first_ == NULL) && (last_ == NULL));
  }

 private:
  QueueElement* first_;
  QueueElement* last_;

  DISALLOW_COPY_AND_ASSIGN(BackgroundCompilationQueue);
};

BackgroundCompiler::BackgroundCompiler(Isolate* isolate)
    : isolate_(isolate),
      queue_monitor_(),
      function_queue_(new BackgroundCompilationQueue()),
      done_monitor_(),
      running_(false),
      done_(true),
      disabled_depth_(0) {}

// Fields all deleted in ::Stop; here clear them.
BackgroundCompiler::~BackgroundCompiler() {
  delete function_queue_;
}

void BackgroundCompiler::Run() {
  while (running_) {
    // Maybe something is already in the queue, check first before waiting
    // to be notified.
    bool result = Thread::EnterIsolateAsHelper(isolate_, Thread::kCompilerTask);
    ASSERT(result);
    {
      Thread* thread = Thread::Current();
      StackZone stack_zone(thread);
      Zone* zone = stack_zone.GetZone();
      HANDLESCOPE(thread);
      Function& function = Function::Handle(zone);
      {
        MonitorLocker ml(&queue_monitor_);
        function = function_queue()->PeekFunction();
      }
      while (running_ && !function.IsNull()) {
        // This is false if we are compiling bytecode -> unoptimized code.
        const bool optimizing = function.ShouldCompilerOptimize();
        ASSERT(FLAG_enable_interpreter || optimizing);

        if (optimizing) {
          Compiler::CompileOptimizedFunction(thread, function,
                                             Compiler::kNoOSRDeoptId);
        } else {
          Compiler::CompileFunction(thread, function);
        }

        QueueElement* qelem = NULL;
        {
          MonitorLocker ml(&queue_monitor_);
          if (function_queue()->IsEmpty()) {
            // We are shutting down, queue was cleared.
            function = Function::null();
          } else {
            qelem = function_queue()->Remove();
            const Function& old = Function::Handle(qelem->Function());
            // If an optimizable method is not optimized, put it back on
            // the background queue (unless it was passed to foreground).
            if ((optimizing && !old.HasOptimizedCode() &&
                 old.IsOptimizable()) ||
                FLAG_stress_test_background_compilation) {
              if (old.is_background_optimizable() &&
                  Compiler::CanOptimizeFunction(thread, old)) {
                QueueElement* repeat_qelem = new QueueElement(old);
                function_queue()->Add(repeat_qelem);
              }
            }
            function = function_queue()->PeekFunction();
          }
        }
        if (qelem != NULL) {
          delete qelem;
        }
      }
    }
    Thread::ExitIsolateAsHelper();
    {
      // Wait to be notified when the work queue is not empty.
      MonitorLocker ml(&queue_monitor_);
      while (function_queue()->IsEmpty() && running_) {
        ml.Wait();
      }
    }
  }  // while running

  {
    // Notify that the thread is done.
    MonitorLocker ml_done(&done_monitor_);
    done_ = true;
    ml_done.Notify();
  }
}

void BackgroundCompiler::Compile(const Function& function) {
  ASSERT(Thread::Current()->IsMutatorThread());
  // TODO(srdjan): Checking different strategy for collecting garbage
  // accumulated by background compiler.
  if (isolate_->heap()->NeedsGarbageCollection()) {
    isolate_->heap()->CollectMostGarbage();
  }
  {
    MonitorLocker ml(&queue_monitor_);
    ASSERT(running_);
    if (function_queue()->ContainsObj(function)) {
      return;
    }
    QueueElement* elem = new QueueElement(function);
    function_queue()->Add(elem);
    ml.Notify();
  }
}

void BackgroundCompiler::VisitPointers(ObjectPointerVisitor* visitor) {
  function_queue_->VisitObjectPointers(visitor);
}

class BackgroundCompilerTask : public ThreadPool::Task {
 public:
  explicit BackgroundCompilerTask(BackgroundCompiler* background_compiler)
      : background_compiler_(background_compiler) {}
  virtual ~BackgroundCompilerTask() {}

 private:
  virtual void Run() { background_compiler_->Run(); }

  BackgroundCompiler* background_compiler_;

  DISALLOW_COPY_AND_ASSIGN(BackgroundCompilerTask);
};

void BackgroundCompiler::Start() {
  Thread* thread = Thread::Current();
  ASSERT(thread->IsMutatorThread());
  ASSERT(!thread->IsAtSafepoint());

  MonitorLocker ml(&done_monitor_);
  if (running_ || !done_) return;
  running_ = true;
  done_ = false;
  bool task_started = Dart::thread_pool()->Run<BackgroundCompilerTask>(this);
  if (!task_started) {
    running_ = false;
    done_ = true;
  }
}

void BackgroundCompiler::Stop() {
  Thread* thread = Thread::Current();
  ASSERT(thread->IsMutatorThread());
  ASSERT(!thread->IsAtSafepoint());

  {
    MonitorLocker ml(&queue_monitor_);
    running_ = false;
    function_queue_->Clear();
    ml.Notify();  // Stop waiting for the queue.
  }

  {
    MonitorLocker ml_done(&done_monitor_);
    while (!done_) {
      ml_done.WaitWithSafepointCheck(thread);
    }
  }
}

void BackgroundCompiler::Enable() {
  disabled_depth_--;
  if (disabled_depth_ < 0) {
    FATAL("Mismatched number of calls to BackgroundCompiler::Enable/Disable.");
  }
}

void BackgroundCompiler::Disable() {
  Stop();
  disabled_depth_++;
}

bool BackgroundCompiler::IsDisabled() {
  return disabled_depth_ > 0;
}

#else  // DART_PRECOMPILED_RUNTIME

CompilationPipeline* CompilationPipeline::New(Zone* zone,
                                              const Function& function) {
  UNREACHABLE();
  return NULL;
}

DEFINE_RUNTIME_ENTRY(CompileFunction, 1) {
  const Function& function = Function::CheckedHandle(zone, arguments.ArgAt(0));
  FATAL3("Precompilation missed function %s (%" Pd ", %s)\n",
         function.ToLibNamePrefixedQualifiedCString(),
         function.token_pos().value(),
         Function::KindToCString(function.kind()));
}

bool Compiler::IsBackgroundCompilation() {
  return false;
}

bool Compiler::CanOptimizeFunction(Thread* thread, const Function& function) {
  UNREACHABLE();
  return false;
}

RawObject* Compiler::CompileFunction(Thread* thread, const Function& function) {
  FATAL1("Attempt to compile function %s", function.ToCString());
  return Error::null();
}

RawError* Compiler::EnsureUnoptimizedCode(Thread* thread,
                                          const Function& function) {
  FATAL1("Attempt to compile function %s", function.ToCString());
  return Error::null();
}

RawObject* Compiler::CompileOptimizedFunction(Thread* thread,
                                              const Function& function,
                                              intptr_t osr_id) {
  FATAL1("Attempt to compile function %s", function.ToCString());
  return Error::null();
}

void Compiler::ComputeLocalVarDescriptors(const Code& code) {
  UNREACHABLE();
}

RawError* Compiler::CompileAllFunctions(const Class& cls) {
  FATAL1("Attempt to compile class %s", cls.ToCString());
  return Error::null();
}

void Compiler::AbortBackgroundCompilation(intptr_t deopt_id, const char* msg) {
  UNREACHABLE();
}

void BackgroundCompiler::Compile(const Function& function) {
  UNREACHABLE();
}

void BackgroundCompiler::VisitPointers(ObjectPointerVisitor* visitor) {
  UNREACHABLE();
}

void BackgroundCompiler::Start() {
  UNREACHABLE();
}

void BackgroundCompiler::Stop() {
  UNREACHABLE();
}

void BackgroundCompiler::Enable() {
  UNREACHABLE();
}

void BackgroundCompiler::Disable() {
  UNREACHABLE();
}

bool BackgroundCompiler::IsDisabled() {
  UNREACHABLE();
  return true;
}

#endif  // DART_PRECOMPILED_RUNTIME

}  // namespace dart