Debugger: prepare code for debugging on a per-function basis.

src/compiler.cc

 // Copyright 2012 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/compiler.h"
 
 #include <algorithm>
 
 #include "src/ast-numbering.h"
 #include "src/bootstrapper.h"
@@ skipping 63 matching lines @@
 #undef PARSE_INFO_GETTER_WITH_DEFAULT
 
 
 // Exactly like a CompilationInfo, except being allocated via {new} and it also
 // creates and enters a Zone on construction and deallocates it on destruction.
 class CompilationInfoWithZone : public CompilationInfo {
  public:
   explicit CompilationInfoWithZone(Handle<JSFunction> function)
       : CompilationInfo(new ParseInfo(&zone_, function)) {}
 
+  explicit CompilationInfoWithZone(Handle<SharedFunctionInfo> shared)

[Michael Starzinger, 2015/07/20 11:29:40]

See comment below.

[Yang, 2015/07/20 12:13:47]

Acknowledged.

+      : CompilationInfo(new ParseInfo(&zone_, shared)) {}
+
   // Virtual destructor because a CompilationInfoWithZone has to exit the
   // zone scope and get rid of dependent maps even when the destructor is
   // called when cast as a CompilationInfo.
   virtual ~CompilationInfoWithZone() {
     DisableFutureOptimization();
     dependencies()->Rollback();
     delete parse_info_;
     parse_info_ = nullptr;
   }
 
@@ skipping 237 matching lines @@
   void Visit##type(type* node) override {      \
     HOptimizedGraphBuilder::Visit##type(node); \
   }
   DECLARATION_NODE_LIST(DEF_VISIT)
 #undef DEF_VISIT
 };
 
 
 OptimizedCompileJob::Status OptimizedCompileJob::CreateGraph() {
   DCHECK(info()->IsOptimizing());
-  DCHECK(!info()->IsCompilingForDebugging());
 
   // Do not use Crankshaft/TurboFan if we need to be able to set break points.
-  if (isolate()->debug()->has_break_points()) {
-    return RetryOptimization(kDebuggerHasBreakPoints);
+  if (info()->shared_info()->HasDebugInfo()) {
+    return AbortOptimization(kFunctionBeingDebugged);
   }
 
   // Limit the number of times we try to optimize functions.
   const int kMaxOptCount =
       FLAG_deopt_every_n_times == 0 ? FLAG_max_opt_count : 1000;
   if (info()->opt_count() > kMaxOptCount) {
     return AbortOptimization(kOptimizedTooManyTimes);
   }
 
   // Check the whitelist for Crankshaft.
@@ skipping 542 matching lines @@
             function, result,
             Compiler::NOT_CONCURRENT).ToHandle(&opt_code)) {
       result = opt_code;
     }
   }
 
   return result;
 }
 
 
-MaybeHandle<Code> Compiler::GetUnoptimizedCode(
-    Handle<SharedFunctionInfo> shared) {
-  DCHECK(!shared->GetIsolate()->has_pending_exception());
-  DCHECK(!shared->is_compiled());
-
-  Zone zone;
-  ParseInfo parse_info(&zone, shared);
-  CompilationInfo info(&parse_info);
-  return GetUnoptimizedCodeCommon(&info);
-}
-
-
 bool Compiler::EnsureCompiled(Handle<JSFunction> function,
                               ClearExceptionFlag flag) {
   if (function->is_compiled()) return true;
   MaybeHandle<Code> maybe_code = Compiler::GetLazyCode(function);
   Handle<Code> code;
   if (!maybe_code.ToHandle(&code)) {
     if (flag == CLEAR_EXCEPTION) {
       function->GetIsolate()->clear_pending_exception();
     }
     return false;
@@ skipping 42 matching lines @@
       shared->set_scope_info(*target_scope_info);
     }
 
     // The existing unoptimized code was replaced with the new one.
     RecordFunctionCompilation(Logger::LAZY_COMPILE_TAG, &unoptimized, shared);
   }
   return true;
 }
 
 
-// Compile full code for debugging. This code will have debug break slots
-// and deoptimization information. Deoptimization information is required
-// in case that an optimized version of this function is still activated on
-// the stack. It will also make sure that the full code is compiled with
-// the same flags as the previous version, that is flags which can change
-// the code generated. The current method of mapping from already compiled
-// full code without debug break slots to full code with debug break slots
-// depends on the generated code is otherwise exactly the same.
-// If compilation fails, just keep the existing code.
-MaybeHandle<Code> Compiler::GetDebugCode(Handle<JSFunction> function) {
-  CompilationInfoWithZone info(function);
-  Isolate* isolate = info.isolate();
-  VMState<COMPILER> state(isolate);
-
-  info.MarkAsDebug();
-
-  DCHECK(!isolate->has_pending_exception());
-  Handle<Code> old_code(function->shared()->code());
-  DCHECK(old_code->kind() == Code::FUNCTION);
-  DCHECK(!old_code->has_debug_break_slots());
-
-  info.MarkCompilingForDebugging();
-  if (old_code->is_compiled_optimizable()) {
-    info.EnableDeoptimizationSupport();
-  } else {
-    info.MarkNonOptimizable();
+MaybeHandle<Code> CompileForDebuggingImpl(CompilationInfo* info) {
+  info->MarkAsDebug();
+  VMState<COMPILER> state(info->isolate());
+  if (info->shared_info()->is_compiled()) {
+    if (info->shared_info()->code()->is_compiled_optimizable()) {
+      info->EnableDeoptimizationSupport();
+    } else {
+      info->MarkNonOptimizable();
+    }
   }
-  MaybeHandle<Code> maybe_new_code = GetUnoptimizedCodeCommon(&info);
+  MaybeHandle<Code> maybe_new_code = GetUnoptimizedCodeCommon(info);
   Handle<Code> new_code;
   if (!maybe_new_code.ToHandle(&new_code)) {
-    isolate->clear_pending_exception();
-  } else {
-    DCHECK_EQ(old_code->is_compiled_optimizable(),
-              new_code->is_compiled_optimizable());
+    info->isolate()->clear_pending_exception();
   }
   return maybe_new_code;
 }
 
 
+MaybeHandle<Code> Compiler::CompileForDebugging(Handle<JSFunction> function) {
+  CompilationInfoWithZone info(function);
+  VMState<COMPILER> state(info.isolate());
+  return CompileForDebuggingImpl(&info);
+}
+
+
+MaybeHandle<Code> Compiler::CompileForDebugging(
+    Handle<SharedFunctionInfo> shared) {
+  DCHECK(shared->allows_lazy_compilation_without_context());
+  CompilationInfoWithZone info(shared);

[Michael Starzinger, 2015/07/20 11:29:39]

There is a constant back-and-forth refactoring around CompilationInfoWithZone.
Can we make the following lines explicit here to avoid adding a new constructor:

    Zone zone;
    ParseInfo parse_info(&zone, shared);
    CompilationInfo info(&parse_info);

[Yang, 2015/07/20 12:13:47]

Done.

+  return CompileForDebuggingImpl(&info);
+}
+
+
 void Compiler::CompileForLiveEdit(Handle<Script> script) {
   // TODO(635): support extensions.
   Zone zone;
   ParseInfo parse_info(&zone, script);
   CompilationInfo info(&parse_info);
   PostponeInterruptsScope postpone(info.isolate());
   VMState<COMPILER> state(info.isolate());
 
   // Get rid of old list of shared function infos.
   info.MarkAsFirstCompile();
@@ skipping 27 matching lines @@
   DCHECK(parse_info->is_eval() || parse_info->is_global() ||
          parse_info->is_module());
 
   parse_info->set_toplevel();
 
   Handle<SharedFunctionInfo> result;
 
   { VMState<COMPILER> state(info->isolate());
     if (parse_info->literal() == NULL) {
       // Parse the script if needed (if it's already parsed, function() is
-      // non-NULL).
+      // non-NULL). If compiling for debugging, we may eagerly compile inner
+      // functions, so do not parse lazily in that case.
       ScriptCompiler::CompileOptions options = parse_info->compile_options();
       bool parse_allow_lazy = (options == ScriptCompiler::kConsumeParserCache ||
                                String::cast(script->source())->length() >
                                    FLAG_min_preparse_length) &&
-                              !Compiler::DebuggerWantsEagerCompilation(isolate);
+                              !info->is_debug();
 
       parse_info->set_allow_lazy_parsing(parse_allow_lazy);
       if (!parse_allow_lazy &&
           (options == ScriptCompiler::kProduceParserCache ||
            options == ScriptCompiler::kConsumeParserCache)) {
         // We are going to parse eagerly, but we either 1) have cached data
         // produced by lazy parsing or 2) are asked to generate cached data.
         // Eager parsing cannot benefit from cached data, and producing cached
         // data while parsing eagerly is not implemented.
         parse_info->set_cached_data(nullptr);
@@ skipping 89 matching lines @@
     script->set_origin_options(options);
     Zone zone;
     ParseInfo parse_info(&zone, script);
     CompilationInfo info(&parse_info);
     parse_info.set_eval();
     if (context->IsNativeContext()) parse_info.set_global();
     parse_info.set_language_mode(language_mode);
     parse_info.set_parse_restriction(restriction);
     parse_info.set_context(context);
 
+    // If we eval from debug code, compile for debugging as well.
+    if (outer_info->HasDebugCode()) info.MarkAsDebug();
     Debug::RecordEvalCaller(script);
 
     shared_info = CompileToplevel(&info);
 
     if (shared_info.is_null()) {
       return MaybeHandle<JSFunction>();
     } else {
       // Explicitly disable optimization for eval code. We're not yet prepared
       // to handle eval-code in the optimizing compiler.
       if (restriction != ONLY_SINGLE_FUNCTION_LITERAL) {
@@ skipping 171 matching lines @@
     // inner functions yet, so do not try to find them. All bets are off for
     // live edit though.
     DCHECK(script->FindSharedFunctionInfo(literal).is_null() ||
            isolate->debug()->live_edit_enabled());
   } else {
     maybe_existing = script->FindSharedFunctionInfo(literal);
   }
   // We found an existing shared function info. If it's already compiled,
   // don't worry about compiling it, and simply return it. If it's not yet
   // compiled, continue to decide whether to eagerly compile.
+  // Carry on if we are compiling eager to obtain code for debugging,
+  // unless we already have code with debut break slots.
   Handle<SharedFunctionInfo> existing;
   if (maybe_existing.ToHandle(&existing) && existing->is_compiled()) {
-    return existing;
+    if (!outer_info->is_debug() || existing->HasDebugCode()) {
+      return existing;
+    }
   }
 
   Zone zone;
   ParseInfo parse_info(&zone, script);
   CompilationInfo info(&parse_info);
   parse_info.set_literal(literal);
   parse_info.set_scope(literal->scope());
   parse_info.set_language_mode(literal->scope()->language_mode());
   if (outer_info->will_serialize()) info.PrepareForSerializing();
   if (outer_info->is_first_compile()) info.MarkAsFirstCompile();
+  if (outer_info->is_debug()) info.MarkAsDebug();
 
   LiveEditFunctionTracker live_edit_tracker(isolate, literal);
   // Determine if the function can be lazily compiled. This is necessary to
   // allow some of our builtin JS files to be lazily compiled. These
   // builtins cannot be handled lazily by the parser, since we have to know
   // if a function uses the special natives syntax, which is something the
   // parser records.
   // If the debugger requests compilation for break points, we cannot be
   // aggressive about lazy compilation, because it might trigger compilation
   // of functions without an outer context when setting a breakpoint through
   // Debug::FindSharedFunctionInfoInScript.
   bool allow_lazy_without_ctx = literal->AllowsLazyCompilationWithoutContext();
-  bool allow_lazy =
-      literal->AllowsLazyCompilation() &&
-      !DebuggerWantsEagerCompilation(isolate, allow_lazy_without_ctx);
+  bool allow_lazy = literal->AllowsLazyCompilation();
+  // Compile eagerly for live edit.
+  allow_lazy &= !LiveEditFunctionTracker::IsActive(isolate);

[Michael Starzinger, 2015/07/20 11:29:39]

nit: Can we combine this into one big conjunction instead?

[Yang, 2015/07/20 12:13:47]

Done.

+  // When compiling debug code, eagerly compile unless we can lazily compile
+  // without the context (SFI without a JSFunction).
+  allow_lazy &= !info.is_debug() || allow_lazy_without_ctx;
 
   if (outer_info->parse_info()->is_toplevel() && outer_info->will_serialize()) {
     // Make sure that if the toplevel code (possibly to be serialized),
     // the inner function must be allowed to be compiled lazily.
     // This is necessary to serialize toplevel code without inner functions.
     DCHECK(allow_lazy);
   }
 
   bool lazy = FLAG_lazy && allow_lazy && !literal->should_eager_compile();
 
@@ skipping 44 matching lines @@
     result->set_allows_lazy_compilation(literal->AllowsLazyCompilation());
     result->set_allows_lazy_compilation_without_context(allow_lazy_without_ctx);
 
     // Set the expected number of properties for instances and return
     // the resulting function.
     SetExpectedNofPropertiesFromEstimate(result,
                                          literal->expected_property_count());
     live_edit_tracker.RecordFunctionInfo(result, literal, info.zone());
     return result;
   } else if (!lazy) {
-    // We have additional data from compilation now.
-    DCHECK(!existing->is_compiled());
+    // We have additional data from compilation now. Upgrading from
+    // non-compiled code or in case of debugging, from non-debug code.
+    DCHECK(info.is_debug() ? !existing->HasDebugCode()

[Michael Starzinger, 2015/07/20 11:29:39]

nit: Not sure exactly what this assertion is guarding against, I would be fine
with dropping it entirely.

[Yang, 2015/07/20 12:13:47]

This is supposed to guard against replacing existing debug code with a new copy.
In that case we would lose break points, as the new code is not patched.

+                           : !existing->is_compiled());
     existing->ReplaceCode(*info.code());
     existing->set_scope_info(*scope_info);
     existing->set_feedback_vector(*info.feedback_vector());
   }
   return existing;
 }
 
 
 MaybeHandle<Code> Compiler::GetOptimizedCode(Handle<JSFunction> function,
                                              Handle<Code> current_code,
                                              ConcurrencyMode mode,
                                              BailoutId osr_ast_id,
                                              JavaScriptFrame* osr_frame) {
+  Isolate* isolate = function->GetIsolate();
+  Handle<SharedFunctionInfo> shared(function->shared(), isolate);
+  if (shared->HasDebugInfo()) return MaybeHandle<Code>();
+
   Handle<Code> cached_code;
   if (GetCodeFromOptimizedCodeMap(
           function, osr_ast_id).ToHandle(&cached_code)) {
     if (FLAG_trace_opt) {
       PrintF("[found optimized code for ");
       function->ShortPrint();
       if (!osr_ast_id.IsNone()) {
         PrintF(" at OSR AST id %d", osr_ast_id.ToInt());
       }
       PrintF("]\n");
     }
     return cached_code;
   }
 
-  Isolate* isolate = function->GetIsolate();
   DCHECK(AllowCompilation::IsAllowed(isolate));
 
-  Handle<SharedFunctionInfo> shared(function->shared(), isolate);
   if (!shared->is_compiled() ||
       shared->scope_info() == ScopeInfo::Empty(isolate)) {
     // The function was never compiled. Compile it unoptimized first.
     // TODO(titzer): reuse the AST and scope info from this compile.
     CompilationInfoWithZone unoptimized(function);
     unoptimized.EnableDeoptimizationSupport();
     if (!GetUnoptimizedCodeCommon(&unoptimized).ToHandle(&current_code)) {
       return MaybeHandle<Code>();
     }
     shared->ReplaceCode(*current_code);
@@ skipping 41 matching lines @@
   // also tears down the zone and the recompile job.
   base::SmartPointer<CompilationInfo> info(job->info());
   Isolate* isolate = info->isolate();
 
   VMState<COMPILER> state(isolate);
   TimerEventScope<TimerEventRecompileSynchronous> timer(info->isolate());
 
   Handle<SharedFunctionInfo> shared = info->shared_info();
   shared->code()->set_profiler_ticks(0);
 
+  DCHECK(!shared->HasDebugInfo());

[Michael Starzinger, 2015/07/20 11:29:39]

What happens of a concurrent compile job for a function has been enqueued and
the debugger sets a breakpoint inside that function while it's on the queue.
Does the debugger flush the queue somehow? Or is there another mechanism in
place to prevent this?

[Yang, 2015/07/20 12:13:47]

Done. We flush the queue when preparing the function for break points.

+
   // 1) Optimization on the concurrent thread may have failed.
   // 2) The function may have already been optimized by OSR.  Simply continue.
   //    Except when OSR already disabled optimization for some reason.
   // 3) The code may have already been invalidated due to dependency change.
-  // 4) Debugger may have been activated.
-  // 5) Code generation may have failed.
+  // 4) Code generation may have failed.
   if (job->last_status() == OptimizedCompileJob::SUCCEEDED) {
     if (shared->optimization_disabled()) {
       job->RetryOptimization(kOptimizationDisabled);
     } else if (info->dependencies()->HasAborted()) {
       job->RetryOptimization(kBailedOutDueToDependencyChange);
-    } else if (isolate->debug()->has_break_points()) {
-      job->RetryOptimization(kDebuggerHasBreakPoints);
     } else if (job->GenerateCode() == OptimizedCompileJob::SUCCEEDED) {
       RecordFunctionCompilation(Logger::LAZY_COMPILE_TAG, info.get(), shared);
       if (shared->SearchOptimizedCodeMap(info->context()->native_context(),
                                          info->osr_ast_id()).code == nullptr) {
         InsertCodeIntoOptimizedCodeMap(info.get());
       }
       if (FLAG_trace_opt) {
         PrintF("[completed optimizing ");
         info->closure()->ShortPrint();
         PrintF("]\n");
       }
       return Handle<Code>(*info->code());
     }
   }
 
   DCHECK(job->last_status() != OptimizedCompileJob::SUCCEEDED);
   if (FLAG_trace_opt) {
     PrintF("[aborted optimizing ");
     info->closure()->ShortPrint();
     PrintF(" because: %s]\n", GetBailoutReason(info->bailout_reason()));
   }
   return Handle<Code>::null();
 }
 
 
-bool Compiler::DebuggerWantsEagerCompilation(Isolate* isolate,
-                                             bool allow_lazy_without_ctx) {
-  if (LiveEditFunctionTracker::IsActive(isolate)) return true;
-  Debug* debug = isolate->debug();
-  bool debugging = debug->is_active() || debug->has_break_points();
-  return debugging && !allow_lazy_without_ctx;
-}
-
-
 CompilationPhase::CompilationPhase(const char* name, CompilationInfo* info)
     : name_(name), info_(info) {
   if (FLAG_hydrogen_stats) {
     info_zone_start_allocation_size_ = info->zone()->allocation_size();
     timer_.Start();
   }
 }
 
 
 CompilationPhase::~CompilationPhase() {
@@ skipping 19 matching lines @@
 
 
 #if DEBUG
 void CompilationInfo::PrintAstForTesting() {
   PrintF("--- Source from AST ---\n%s\n",
          PrettyPrinter(isolate(), zone()).PrintProgram(function()));
 }
 #endif
 }  // namespace internal
 }  // namespace v8