[debugger,compiler] do not recompile already compiled inner functions.

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 <memory>
 
 #include "src/asmjs/asm-js.h"
@@ skipping 1573 matching lines @@
   parse_info.set_ast_value_factory_owned(false);
 
   if (outer_info->will_serialize()) info.PrepareForSerializing();
   if (outer_info->is_debug()) info.MarkAsDebug();
 
   // Generate code
   TimerEventScope<TimerEventCompileCode> timer(isolate);
   RuntimeCallTimerScope runtimeTimer(isolate, &RuntimeCallStats::CompileCode);
   TRACE_EVENT0(TRACE_DISABLED_BY_DEFAULT("v8.compile"), "V8.CompileCode");
 
-  if (!literal->ShouldEagerCompile()) {
+  if (result->is_compiled()) {
+    // If this inner function is already compiled, we don't need to compile
+    // again. When compiling for debug, we are not interested in having debug
+    // break slots in inner functions, neither for setting break points nor
+    // for revealing inner functions.
+    // This is especially important for generators. We must not replace the
+    // code for generators, as there may be suspended generator objects.
+    return result;
+  } else if (!literal->ShouldEagerCompile()) {
     info.SetCode(isolate->builtins()->CompileLazy());
     Scope* outer_scope = literal->scope()->GetOuterScopeWithContext();
     if (outer_scope) {
       result->set_outer_scope_info(*outer_scope->scope_info());
     }
   } else if (Renumber(info.parse_info()) && GenerateUnoptimizedCode(&info)) {
     // Code generation will ensure that the feedback vector is present and
     // appropriately sized.
     DCHECK(!info.code().is_null());
     if (literal->should_be_used_once_hint()) {
@@ skipping 100 matching lines @@
     DCHECK(shared->is_compiled());
     function->set_literals(cached.literals);
   } else if (shared->is_compiled()) {
     // TODO(mvstanton): pass pretenure flag to EnsureLiterals.
     JSFunction::EnsureLiterals(function);
   }
 }
 
 }  // namespace internal
 }  // namespace v8