src/debug/debug-coverage.cc

// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/debug/debug-coverage.h"

#include "src/base/hashmap.h"
#include "src/deoptimizer.h"
#include "src/isolate.h"
#include "src/objects-inl.h"
#include "src/objects.h"

namespace v8 {
namespace internal {

class SharedToCounterMap
    : public base::TemplateHashMapImpl<SharedFunctionInfo*, uint32_t,
                                       base::KeyEqualityMatcher<void*>,
                                       base::DefaultAllocationPolicy> {
 public:
  typedef base::TemplateHashMapEntry<SharedFunctionInfo*, uint32_t> Entry;
  inline void Add(SharedFunctionInfo* key, uint32_t count) {
    Entry* entry = LookupOrInsert(key, Hash(key), []() { return 0; });
    uint32_t old_count = entry->value;
    if (UINT32_MAX - count < old_count) {
      entry->value = UINT32_MAX;
    } else {
      entry->value = old_count + count;
    }
  }

  inline uint32_t Get(SharedFunctionInfo* key) {
    Entry* entry = Lookup(key, Hash(key));
    if (entry == nullptr) return 0;
    return entry->value;
  }

 private:
  static uint32_t Hash(SharedFunctionInfo* key) {
    return static_cast<uint32_t>(reinterpret_cast<intptr_t>(key));
  }

  DisallowHeapAllocation no_gc;
};

namespace {
int StartPosition(SharedFunctionInfo* info) {
  int start = info->function_token_position();
  if (start == kNoSourcePosition) start = info->start_position();
  return start;
}

bool CompareSharedFunctionInfo(SharedFunctionInfo* a, SharedFunctionInfo* b) {
  int a_start = StartPosition(a);
  int b_start = StartPosition(b);
  if (a_start == b_start) return a->end_position() > b->end_position();
  return a_start < b_start;
}
}  // anonymous namespace

Coverage* Coverage::Collect(Isolate* isolate, bool reset_count) {
  SharedToCounterMap counter_map;

  // Feed invocation count into the counter map.
  if (isolate->IsCodeCoverageEnabled()) {
    // Feedback vectors are already listed to prevent losing them to GC.
    Handle<ArrayList> list =
        Handle<ArrayList>::cast(isolate->factory()->code_coverage_list());
    for (int i = 0; i < list->Length(); i++) {
      FeedbackVector* vector = FeedbackVector::cast(list->Get(i));
      SharedFunctionInfo* shared = vector->shared_function_info();
      DCHECK(shared->IsSubjectToDebugging());
      uint32_t count = static_cast<uint32_t>(vector->invocation_count());
      if (reset_count) vector->clear_invocation_count();
      counter_map.Add(shared, count);
    }
  } else {
    // Iterate the heap to find all feedback vectors and accumulate the
    // invocation counts into the map for each shared function info.
    HeapIterator heap_iterator(isolate->heap());
    while (HeapObject* current_obj = heap_iterator.next()) {
      if (!current_obj->IsFeedbackVector()) continue;
      FeedbackVector* vector = FeedbackVector::cast(current_obj);
      SharedFunctionInfo* shared = vector->shared_function_info();
      if (!shared->IsSubjectToDebugging()) continue;
      uint32_t count = static_cast<uint32_t>(vector->invocation_count());
      if (reset_count) vector->clear_invocation_count();
      counter_map.Add(shared, count);
    }
  }

  // Iterate shared function infos of every script and build a mapping
  // between source ranges and invocation counts.
  Coverage* result = new Coverage();
  Script::Iterator scripts(isolate);
  while (Script* script = scripts.Next()) {
    // Dismiss non-user scripts.
    if (script->type() != Script::TYPE_NORMAL) continue;

    // Create and add new script data.
    Handle<Script> script_handle(script, isolate);
    result->emplace_back(isolate, script_handle);
    std::vector<CoverageFunction>* functions = &result->back().functions;

    std::vector<SharedFunctionInfo*> sorted;
    bool has_toplevel = false;

    {
      // Sort functions by start position, from outer to inner functions.
      SharedFunctionInfo::ScriptIterator infos(script_handle);
      while (SharedFunctionInfo* info = infos.Next()) {
        has_toplevel |= info->is_toplevel();
        sorted.push_back(info);
      }
      std::sort(sorted.begin(), sorted.end(), CompareSharedFunctionInfo);
    }

    functions->reserve(sorted.size() + (has_toplevel ? 0 : 1));

    if (!has_toplevel) {
      // Add a replacement toplevel function if it does not exist.
      int source_end = String::cast(script->source())->length();
      functions->emplace_back(0, source_end, 1u,
                              isolate->factory()->empty_string());
    }

    // Use sorted list to reconstruct function nesting.
    for (SharedFunctionInfo* info : sorted) {
      int start = StartPosition(info);
      int end = info->end_position();
      uint32_t count = counter_map.Get(info);
      Handle<String> name(info->DebugName(), isolate);
      functions->emplace_back(start, end, count, name);
    }
  }
  return result;
}

void Coverage::TogglePrecise(Isolate* isolate, bool enable) {
  if (enable) {
    HandleScope scope(isolate);
    // Remove all optimized function. Optimized and inlined functions do not
    // increment invocation count.
    Deoptimizer::DeoptimizeAll(isolate);
    // Collect existing feedback vectors.
    std::vector<Handle<FeedbackVector>> vectors;
    {
      HeapIterator heap_iterator(isolate->heap());
      while (HeapObject* current_obj = heap_iterator.next()) {
        if (!current_obj->IsFeedbackVector()) continue;
        FeedbackVector* vector = FeedbackVector::cast(current_obj);
        SharedFunctionInfo* shared = vector->shared_function_info();
        if (!shared->IsSubjectToDebugging()) continue;
        vector->clear_invocation_count();
        vectors.emplace_back(vector, isolate);
      }
    }
    // Add collected feedback vectors to the root list lest we lose them to GC.
    Handle<ArrayList> list =
        ArrayList::New(isolate, static_cast<int>(vectors.size()));
    for (const auto& vector : vectors) list = ArrayList::Add(list, vector);
    isolate->SetCodeCoverageList(*list);
  } else {
    isolate->SetCodeCoverageList(isolate->heap()->undefined_value());
  }
}

}  // namespace internal
}  // namespace v8