src/runtime-profiler.cc - v8/v8.git - Git at Google

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 #include "v8.h"

 #include "runtime-profiler.h"

 #include "assembler.h"
 #include "code-stubs.h"
 #include "compilation-cache.h"
 #include "deoptimizer.h"
 #include "execution.h"
 #include "global-handles.h"
 #include "isolate-inl.h"
 #include "mark-compact.h"
 #include "platform.h"
 #include "scopeinfo.h"

 namespace v8 {
 namespace internal {


 // Optimization sampler constants.
 static const int kSamplerFrameCount = 2;

 // Constants for statistical profiler.
 static const int kSamplerFrameWeight[kSamplerFrameCount] = { 2, 1 };

 static const int kSamplerTicksBetweenThresholdAdjustment = 32;

 static const int kSamplerThresholdInit = 3;
 static const int kSamplerThresholdMin = 1;
 static const int kSamplerThresholdDelta = 1;

 static const int kSamplerThresholdSizeFactorInit = 3;

 static const int kSizeLimit = 1500;

 // Constants for counter based profiler.

 // Number of times a function has to be seen on the stack before it is
 // optimized.
 static const int kProfilerTicksBeforeOptimization = 2;

 // Maximum size in bytes of generated code for a function to be optimized
 // the very first time it is seen on the stack.
 static const int kMaxSizeEarlyOpt = 500;


 Atomic32 RuntimeProfiler::state_ = 0;
 // TODO(isolates): Create the semaphore lazily and clean it up when no
 // longer required.
 Semaphore* RuntimeProfiler::semaphore_ = OS::CreateSemaphore(0);

 #ifdef DEBUG
 bool RuntimeProfiler::has_been_globally_set_up_ = false;
 #endif
 bool RuntimeProfiler::enabled_ = false;


 RuntimeProfiler::RuntimeProfiler(Isolate* isolate)
     : isolate_(isolate),
       sampler_threshold_(kSamplerThresholdInit),
       sampler_threshold_size_factor_(kSamplerThresholdSizeFactorInit),
       sampler_ticks_until_threshold_adjustment_(
           kSamplerTicksBetweenThresholdAdjustment),
       sampler_window_position_(0) {
   ClearSampleBuffer();
 }


 void RuntimeProfiler::GlobalSetup() {
   ASSERT(!has_been_globally_set_up_);
   enabled_ = V8::UseCrankshaft() && FLAG_opt;
 #ifdef DEBUG
   has_been_globally_set_up_ = true;
 #endif
 }


 static void GetICCounts(JSFunction* function,
                         int* ic_with_typeinfo_count,
                         int* ic_total_count,
                         int* percentage) {
   *ic_total_count = 0;
   *ic_with_typeinfo_count = 0;
   Object* raw_info =
       function->shared()->code()->type_feedback_info();
   if (raw_info->IsTypeFeedbackInfo()) {
     TypeFeedbackInfo* info = TypeFeedbackInfo::cast(raw_info);
     *ic_with_typeinfo_count = info->ic_with_typeinfo_count();
     *ic_total_count = info->ic_total_count();
   }
   *percentage = *ic_total_count > 0
       ? 100 * *ic_with_typeinfo_count / *ic_total_count
       : 100;
 }


 void RuntimeProfiler::Optimize(JSFunction* function, const char* reason) {
   ASSERT(function->IsOptimizable());
   if (FLAG_trace_opt) {
     PrintF("[marking ");
     function->PrintName();
     PrintF(" 0x%" V8PRIxPTR, reinterpret_cast<intptr_t>(function->address()));
     PrintF(" for recompilation, reason: %s", reason);
     if (FLAG_type_info_threshold > 0) {
       int typeinfo, total, percentage;
       GetICCounts(function, &typeinfo, &total, &percentage);
       PrintF(", ICs with typeinfo: %d/%d (%d%%)", typeinfo, total, percentage);
     }
     PrintF("]\n");
   }

   // The next call to the function will trigger optimization.
   function->MarkForLazyRecompilation();
 }


 void RuntimeProfiler::AttemptOnStackReplacement(JSFunction* function) {
   // See AlwaysFullCompiler (in compiler.cc) comment on why we need
   // Debug::has_break_points().
   ASSERT(function->IsMarkedForLazyRecompilation());
   if (!FLAG_use_osr ||
       isolate_->DebuggerHasBreakPoints() ||
       function->IsBuiltin()) {
     return;
   }

   SharedFunctionInfo* shared = function->shared();
   // If the code is not optimizable, don't try OSR.
   if (!shared->code()->optimizable()) return;

   // We are not prepared to do OSR for a function that already has an
   // allocated arguments object.  The optimized code would bypass it for
   // arguments accesses, which is unsound.  Don't try OSR.
   if (shared->uses_arguments()) return;

   // We're using on-stack replacement: patch the unoptimized code so that
   // any back edge in any unoptimized frame will trigger on-stack
   // replacement for that frame.
   if (FLAG_trace_osr) {
     PrintF("[patching stack checks in ");
     function->PrintName();
     PrintF(" for on-stack replacement]\n");
   }

   // Get the stack check stub code object to match against.  We aren't
   // prepared to generate it, but we don't expect to have to.
   bool found_code = false;
   Code* stack_check_code = NULL;
 #ifdef V8_TARGET_ARCH_IA32
   if (FLAG_count_based_interrupts) {
     InterruptStub interrupt_stub;
     found_code = interrupt_stub.FindCodeInCache(&stack_check_code);
   } else  // NOLINT
 #endif
   {  // NOLINT
     StackCheckStub check_stub;
     found_code = check_stub.FindCodeInCache(&stack_check_code);
   }
   if (found_code) {
     Code* replacement_code =
         isolate_->builtins()->builtin(Builtins::kOnStackReplacement);
     Code* unoptimized_code = shared->code();
     Deoptimizer::PatchStackCheckCode(unoptimized_code,
                                      stack_check_code,
                                      replacement_code);
   }
 }


 void RuntimeProfiler::ClearSampleBuffer() {
   memset(sampler_window_, 0, sizeof(sampler_window_));
   memset(sampler_window_weight_, 0, sizeof(sampler_window_weight_));
 }


 int RuntimeProfiler::LookupSample(JSFunction* function) {
   int weight = 0;
   for (int i = 0; i < kSamplerWindowSize; i++) {
     Object* sample = sampler_window_[i];
     if (sample != NULL) {
       if (function == sample) {
         weight += sampler_window_weight_[i];
       }
     }
   }
   return weight;
 }


 void RuntimeProfiler::AddSample(JSFunction* function, int weight) {
   ASSERT(IsPowerOf2(kSamplerWindowSize));
   sampler_window_[sampler_window_position_] = function;
   sampler_window_weight_[sampler_window_position_] = weight;
   sampler_window_position_ = (sampler_window_position_ + 1) &
       (kSamplerWindowSize - 1);
 }


 void RuntimeProfiler::OptimizeNow() {
   HandleScope scope(isolate_);

   // Run through the JavaScript frames and collect them. If we already
   // have a sample of the function, we mark it for optimizations
   // (eagerly or lazily).
   JSFunction* samples[kSamplerFrameCount];
   int sample_count = 0;
   int frame_count = 0;
   int frame_count_limit = FLAG_watch_ic_patching ? FLAG_frame_count
                                                  : kSamplerFrameCount;
   for (JavaScriptFrameIterator it(isolate_);
        frame_count++ < frame_count_limit && !it.done();
        it.Advance()) {
     JavaScriptFrame* frame = it.frame();
     JSFunction* function = JSFunction::cast(frame->function());

     if (!FLAG_watch_ic_patching) {
       // Adjust threshold each time we have processed
       // a certain number of ticks.
       if (sampler_ticks_until_threshold_adjustment_ > 0) {
         sampler_ticks_until_threshold_adjustment_--;
         if (sampler_ticks_until_threshold_adjustment_ <= 0) {
           // If the threshold is not already at the minimum
           // modify and reset the ticks until next adjustment.
           if (sampler_threshold_ > kSamplerThresholdMin) {
             sampler_threshold_ -= kSamplerThresholdDelta;
             sampler_ticks_until_threshold_adjustment_ =
                 kSamplerTicksBetweenThresholdAdjustment;
           }
         }
       }
     }

     if (function->IsMarkedForLazyRecompilation()) {
       Code* unoptimized = function->shared()->code();
       int nesting = unoptimized->allow_osr_at_loop_nesting_level();
       if (nesting == 0) AttemptOnStackReplacement(function);
       int new_nesting = Min(nesting + 1, Code::kMaxLoopNestingMarker);
       unoptimized->set_allow_osr_at_loop_nesting_level(new_nesting);
     }

     // Do not record non-optimizable functions.
     if (!function->IsOptimizable()) continue;

     // Only record top-level code on top of the execution stack and
     // avoid optimizing excessively large scripts since top-level code
     // will be executed only once.
     const int kMaxToplevelSourceSize = 10 * 1024;
     if (function->shared()->is_toplevel()
         && (frame_count > 1
             || function->shared()->SourceSize() > kMaxToplevelSourceSize)) {
       continue;
     }

     if (FLAG_watch_ic_patching) {
       int ticks = function->shared()->profiler_ticks();

       if (ticks >= kProfilerTicksBeforeOptimization) {
         int typeinfo, total, percentage;
         GetICCounts(function, &typeinfo, &total, &percentage);
         if (percentage >= FLAG_type_info_threshold) {
           // If this particular function hasn't had any ICs patched for enough
           // ticks, optimize it now.
           Optimize(function, "hot and stable");
         } else {
           if (FLAG_trace_opt_verbose) {
             PrintF("[not yet optimizing ");
             function->PrintName();
             PrintF(", not enough type info: %d/%d (%d%%)]\n",
                    typeinfo, total, percentage);
           }
         }
       } else if (!any_ic_changed_ &&
           function->shared()->code()->instruction_size() < kMaxSizeEarlyOpt) {
         // If no IC was patched since the last tick and this function is very
         // small, optimistically optimize it now.
         Optimize(function, "small function");
       } else if (!code_generated_ &&
           !any_ic_changed_ &&
           total_code_generated_ > 0 &&
           total_code_generated_ < 2000) {
         // If no code was generated and no IC was patched since the last tick,
         // but a little code has already been generated since last Reset(),
         // then type info might already be stable and we can optimize now.
         Optimize(function, "stable on startup");
       } else {
         function->shared()->set_profiler_ticks(ticks + 1);
       }
     } else {  // !FLAG_watch_ic_patching
       samples[sample_count++] = function;

       int function_size = function->shared()->SourceSize();
       int threshold_size_factor = (function_size > kSizeLimit)
           ? sampler_threshold_size_factor_
           : 1;

       int threshold = sampler_threshold_ * threshold_size_factor;

       if (LookupSample(function) >= threshold) {
         Optimize(function, "sampler window lookup");
       }
     }
   }
   if (FLAG_watch_ic_patching) {
     any_ic_changed_ = false;
     code_generated_ = false;
   } else {  // !FLAG_watch_ic_patching
     // Add the collected functions as samples. It's important not to do
     // this as part of collecting them because this will interfere with
     // the sample lookup in case of recursive functions.
     for (int i = 0; i < sample_count; i++) {
       AddSample(samples[i], kSamplerFrameWeight[i]);
     }
   }
 }


 void RuntimeProfiler::NotifyTick() {
 #ifdef V8_TARGET_ARCH_IA32
   if (FLAG_count_based_interrupts) return;
 #endif
   isolate_->stack_guard()->RequestRuntimeProfilerTick();
 }


 void RuntimeProfiler::SetUp() {
   ASSERT(has_been_globally_set_up_);
   if (!FLAG_watch_ic_patching) {
     ClearSampleBuffer();
   }
   // If the ticker hasn't already started, make sure to do so to get
   // the ticks for the runtime profiler.
   if (IsEnabled()) isolate_->logger()->EnsureTickerStarted();
 }


 void RuntimeProfiler::Reset() {
   if (FLAG_watch_ic_patching) {
     total_code_generated_ = 0;
   } else {  // !FLAG_watch_ic_patching
     sampler_threshold_ = kSamplerThresholdInit;
     sampler_threshold_size_factor_ = kSamplerThresholdSizeFactorInit;
     sampler_ticks_until_threshold_adjustment_ =
         kSamplerTicksBetweenThresholdAdjustment;
   }
 }


 void RuntimeProfiler::TearDown() {
   // Nothing to do.
 }


 int RuntimeProfiler::SamplerWindowSize() {
   return kSamplerWindowSize;
 }


 // Update the pointers in the sampler window after a GC.
 void RuntimeProfiler::UpdateSamplesAfterScavenge() {
   for (int i = 0; i < kSamplerWindowSize; i++) {
     Object* function = sampler_window_[i];
     if (function != NULL && isolate_->heap()->InNewSpace(function)) {
       MapWord map_word = HeapObject::cast(function)->map_word();
       if (map_word.IsForwardingAddress()) {
         sampler_window_[i] = map_word.ToForwardingAddress();
       } else {
         sampler_window_[i] = NULL;
       }
     }
   }
 }


 void RuntimeProfiler::HandleWakeUp(Isolate* isolate) {
   // The profiler thread must still be waiting.
   ASSERT(NoBarrier_Load(&state_) >= 0);
   // In IsolateEnteredJS we have already incremented the counter and
   // undid the decrement done by the profiler thread. Increment again
   // to get the right count of active isolates.
   NoBarrier_AtomicIncrement(&state_, 1);
   semaphore_->Signal();
 }


 bool RuntimeProfiler::IsSomeIsolateInJS() {
   return NoBarrier_Load(&state_) > 0;
 }


 bool RuntimeProfiler::WaitForSomeIsolateToEnterJS() {
   Atomic32 old_state = NoBarrier_CompareAndSwap(&state_, 0, -1);
   ASSERT(old_state >= -1);
   if (old_state != 0) return false;
   semaphore_->Wait();
   return true;
 }


 void RuntimeProfiler::StopRuntimeProfilerThreadBeforeShutdown(Thread* thread) {
   // Do a fake increment. If the profiler is waiting on the semaphore,
   // the returned state is 0, which can be left as an initial state in
   // case profiling is restarted later. If the profiler is not
   // waiting, the increment will prevent it from waiting, but has to
   // be undone after the profiler is stopped.
   Atomic32 new_state = NoBarrier_AtomicIncrement(&state_, 1);
   ASSERT(new_state >= 0);
   if (new_state == 0) {
     // The profiler thread is waiting. Wake it up. It must check for
     // stop conditions before attempting to wait again.
     semaphore_->Signal();
   }
   thread->Join();
   // The profiler thread is now stopped. Undo the increment in case it
   // was not waiting.
   if (new_state != 0) {
     NoBarrier_AtomicIncrement(&state_, -1);
   }
 }


 void RuntimeProfiler::RemoveDeadSamples() {
   for (int i = 0; i < kSamplerWindowSize; i++) {
     Object* function = sampler_window_[i];
     if (function != NULL &&
         !Marking::MarkBitFrom(HeapObject::cast(function)).Get()) {
       sampler_window_[i] = NULL;
     }
   }
 }


 void RuntimeProfiler::UpdateSamplesAfterCompact(ObjectVisitor* visitor) {
   for (int i = 0; i < kSamplerWindowSize; i++) {
     visitor->VisitPointer(&sampler_window_[i]);
   }
 }


 bool RuntimeProfilerRateLimiter::SuspendIfNecessary() {
   if (!RuntimeProfiler::IsSomeIsolateInJS()) {
     return RuntimeProfiler::WaitForSomeIsolateToEnterJS();
   }
   return false;
 }


 } }  // namespace v8::internal
	// Copyright 2012 the V8 project authors. All rights reserved.
	// Redistribution and use in source and binary forms, with or without
	// modification, are permitted provided that the following conditions are
	// met:
	//
	// * Redistributions of source code must retain the above copyright
	// notice, this list of conditions and the following disclaimer.
	// * Redistributions in binary form must reproduce the above
	// copyright notice, this list of conditions and the following
	// disclaimer in the documentation and/or other materials provided
	// with the distribution.
	// * Neither the name of Google Inc. nor the names of its
	// contributors may be used to endorse or promote products derived
	// from this software without specific prior written permission.
	//
	// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	#include "v8.h"

	#include "runtime-profiler.h"

	#include "assembler.h"
	#include "code-stubs.h"
	#include "compilation-cache.h"
	#include "deoptimizer.h"
	#include "execution.h"
	#include "global-handles.h"
	#include "isolate-inl.h"
	#include "mark-compact.h"
	#include "platform.h"
	#include "scopeinfo.h"

	namespace v8 {
	namespace internal {


	// Optimization sampler constants.
	static const int kSamplerFrameCount = 2;

	// Constants for statistical profiler.
	static const int kSamplerFrameWeight[kSamplerFrameCount] = { 2, 1 };

	static const int kSamplerTicksBetweenThresholdAdjustment = 32;

	static const int kSamplerThresholdInit = 3;
	static const int kSamplerThresholdMin = 1;
	static const int kSamplerThresholdDelta = 1;

	static const int kSamplerThresholdSizeFactorInit = 3;

	static const int kSizeLimit = 1500;

	// Constants for counter based profiler.

	// Number of times a function has to be seen on the stack before it is
	// optimized.
	static const int kProfilerTicksBeforeOptimization = 2;

	// Maximum size in bytes of generated code for a function to be optimized
	// the very first time it is seen on the stack.
	static const int kMaxSizeEarlyOpt = 500;


	Atomic32 RuntimeProfiler::state_ = 0;
	// TODO(isolates): Create the semaphore lazily and clean it up when no
	// longer required.
	Semaphore* RuntimeProfiler::semaphore_ = OS::CreateSemaphore(0);

	#ifdef DEBUG
	bool RuntimeProfiler::has_been_globally_set_up_ = false;
	#endif
	bool RuntimeProfiler::enabled_ = false;


	RuntimeProfiler::RuntimeProfiler(Isolate* isolate)
	: isolate_(isolate),
	sampler_threshold_(kSamplerThresholdInit),
	sampler_threshold_size_factor_(kSamplerThresholdSizeFactorInit),
	sampler_ticks_until_threshold_adjustment_(
	kSamplerTicksBetweenThresholdAdjustment),
	sampler_window_position_(0) {
	ClearSampleBuffer();
	}


	void RuntimeProfiler::GlobalSetup() {
	ASSERT(!has_been_globally_set_up_);
	enabled_ = V8::UseCrankshaft() && FLAG_opt;
	#ifdef DEBUG
	has_been_globally_set_up_ = true;
	#endif
	}


	static void GetICCounts(JSFunction* function,
	int* ic_with_typeinfo_count,
	int* ic_total_count,
	int* percentage) {
	*ic_total_count = 0;
	*ic_with_typeinfo_count = 0;
	Object* raw_info =
	function->shared()->code()->type_feedback_info();
	if (raw_info->IsTypeFeedbackInfo()) {
	TypeFeedbackInfo* info = TypeFeedbackInfo::cast(raw_info);
	*ic_with_typeinfo_count = info->ic_with_typeinfo_count();
	*ic_total_count = info->ic_total_count();
	}
	percentage = ic_total_count > 0
	? 100 * ic_with_typeinfo_count / ic_total_count
	: 100;
	}


	void RuntimeProfiler::Optimize(JSFunction* function, const char* reason) {
	ASSERT(function->IsOptimizable());
	if (FLAG_trace_opt) {
	PrintF("[marking ");
	function->PrintName();
	PrintF(" 0x%" V8PRIxPTR, reinterpret_cast<intptr_t>(function->address()));
	PrintF(" for recompilation, reason: %s", reason);
	if (FLAG_type_info_threshold > 0) {
	int typeinfo, total, percentage;
	GetICCounts(function, &typeinfo, &total, &percentage);
	PrintF(", ICs with typeinfo: %d/%d (%d%%)", typeinfo, total, percentage);
	}
	PrintF("]\n");
	}

	// The next call to the function will trigger optimization.
	function->MarkForLazyRecompilation();
	}


	void RuntimeProfiler::AttemptOnStackReplacement(JSFunction* function) {
	// See AlwaysFullCompiler (in compiler.cc) comment on why we need
	// Debug::has_break_points().
	ASSERT(function->IsMarkedForLazyRecompilation());
	if (!FLAG_use_osr \|\|
	isolate_->DebuggerHasBreakPoints() \|\|
	function->IsBuiltin()) {
	return;
	}

	SharedFunctionInfo* shared = function->shared();
	// If the code is not optimizable, don't try OSR.
	if (!shared->code()->optimizable()) return;

	// We are not prepared to do OSR for a function that already has an
	// allocated arguments object. The optimized code would bypass it for
	// arguments accesses, which is unsound. Don't try OSR.
	if (shared->uses_arguments()) return;

	// We're using on-stack replacement: patch the unoptimized code so that
	// any back edge in any unoptimized frame will trigger on-stack
	// replacement for that frame.
	if (FLAG_trace_osr) {
	PrintF("[patching stack checks in ");
	function->PrintName();
	PrintF(" for on-stack replacement]\n");
	}

	// Get the stack check stub code object to match against. We aren't
	// prepared to generate it, but we don't expect to have to.
	bool found_code = false;
	Code* stack_check_code = NULL;
	#ifdef V8_TARGET_ARCH_IA32
	if (FLAG_count_based_interrupts) {
	InterruptStub interrupt_stub;
	found_code = interrupt_stub.FindCodeInCache(&stack_check_code);
	} else // NOLINT
	#endif
	{ // NOLINT
	StackCheckStub check_stub;
	found_code = check_stub.FindCodeInCache(&stack_check_code);
	}
	if (found_code) {
	Code* replacement_code =
	isolate_->builtins()->builtin(Builtins::kOnStackReplacement);
	Code* unoptimized_code = shared->code();
	Deoptimizer::PatchStackCheckCode(unoptimized_code,
	stack_check_code,
	replacement_code);
	}
	}


	void RuntimeProfiler::ClearSampleBuffer() {
	memset(sampler_window_, 0, sizeof(sampler_window_));
	memset(sampler_window_weight_, 0, sizeof(sampler_window_weight_));
	}


	int RuntimeProfiler::LookupSample(JSFunction* function) {
	int weight = 0;
	for (int i = 0; i < kSamplerWindowSize; i++) {
	Object* sample = sampler_window_[i];
	if (sample != NULL) {
	if (function == sample) {
	weight += sampler_window_weight_[i];
	}
	}
	}
	return weight;
	}


	void RuntimeProfiler::AddSample(JSFunction* function, int weight) {
	ASSERT(IsPowerOf2(kSamplerWindowSize));
	sampler_window_[sampler_window_position_] = function;
	sampler_window_weight_[sampler_window_position_] = weight;
	sampler_window_position_ = (sampler_window_position_ + 1) &
	(kSamplerWindowSize - 1);
	}


	void RuntimeProfiler::OptimizeNow() {
	HandleScope scope(isolate_);

	// Run through the JavaScript frames and collect them. If we already
	// have a sample of the function, we mark it for optimizations
	// (eagerly or lazily).
	JSFunction* samples[kSamplerFrameCount];
	int sample_count = 0;
	int frame_count = 0;
	int frame_count_limit = FLAG_watch_ic_patching ? FLAG_frame_count
	: kSamplerFrameCount;
	for (JavaScriptFrameIterator it(isolate_);
	frame_count++ < frame_count_limit && !it.done();
	it.Advance()) {
	JavaScriptFrame* frame = it.frame();
	JSFunction* function = JSFunction::cast(frame->function());

	if (!FLAG_watch_ic_patching) {
	// Adjust threshold each time we have processed
	// a certain number of ticks.
	if (sampler_ticks_until_threshold_adjustment_ > 0) {
	sampler_ticks_until_threshold_adjustment_--;
	if (sampler_ticks_until_threshold_adjustment_ <= 0) {
	// If the threshold is not already at the minimum
	// modify and reset the ticks until next adjustment.
	if (sampler_threshold_ > kSamplerThresholdMin) {
	sampler_threshold_ -= kSamplerThresholdDelta;
	sampler_ticks_until_threshold_adjustment_ =
	kSamplerTicksBetweenThresholdAdjustment;
	}
	}
	}
	}

	if (function->IsMarkedForLazyRecompilation()) {
	Code* unoptimized = function->shared()->code();
	int nesting = unoptimized->allow_osr_at_loop_nesting_level();
	if (nesting == 0) AttemptOnStackReplacement(function);
	int new_nesting = Min(nesting + 1, Code::kMaxLoopNestingMarker);
	unoptimized->set_allow_osr_at_loop_nesting_level(new_nesting);
	}

	// Do not record non-optimizable functions.
	if (!function->IsOptimizable()) continue;

	// Only record top-level code on top of the execution stack and
	// avoid optimizing excessively large scripts since top-level code
	// will be executed only once.
	const int kMaxToplevelSourceSize = 10 * 1024;
	if (function->shared()->is_toplevel()
	&& (frame_count > 1
	\|\| function->shared()->SourceSize() > kMaxToplevelSourceSize)) {
	continue;
	}

	if (FLAG_watch_ic_patching) {
	int ticks = function->shared()->profiler_ticks();

	if (ticks >= kProfilerTicksBeforeOptimization) {
	int typeinfo, total, percentage;
	GetICCounts(function, &typeinfo, &total, &percentage);
	if (percentage >= FLAG_type_info_threshold) {
	// If this particular function hasn't had any ICs patched for enough
	// ticks, optimize it now.
	Optimize(function, "hot and stable");
	} else {
	if (FLAG_trace_opt_verbose) {
	PrintF("[not yet optimizing ");
	function->PrintName();
	PrintF(", not enough type info: %d/%d (%d%%)]\n",
	typeinfo, total, percentage);
	}
	}
	} else if (!any_ic_changed_ &&
	function->shared()->code()->instruction_size() < kMaxSizeEarlyOpt) {
	// If no IC was patched since the last tick and this function is very
	// small, optimistically optimize it now.
	Optimize(function, "small function");
	} else if (!code_generated_ &&
	!any_ic_changed_ &&
	total_code_generated_ > 0 &&
	total_code_generated_ < 2000) {
	// If no code was generated and no IC was patched since the last tick,
	// but a little code has already been generated since last Reset(),
	// then type info might already be stable and we can optimize now.
	Optimize(function, "stable on startup");
	} else {
	function->shared()->set_profiler_ticks(ticks + 1);
	}
	} else { // !FLAG_watch_ic_patching
	samples[sample_count++] = function;

	int function_size = function->shared()->SourceSize();
	int threshold_size_factor = (function_size > kSizeLimit)
	? sampler_threshold_size_factor_
	: 1;

	int threshold = sampler_threshold_ * threshold_size_factor;

	if (LookupSample(function) >= threshold) {
	Optimize(function, "sampler window lookup");
	}
	}
	}
	if (FLAG_watch_ic_patching) {
	any_ic_changed_ = false;
	code_generated_ = false;
	} else { // !FLAG_watch_ic_patching
	// Add the collected functions as samples. It's important not to do
	// this as part of collecting them because this will interfere with
	// the sample lookup in case of recursive functions.
	for (int i = 0; i < sample_count; i++) {
	AddSample(samples[i], kSamplerFrameWeight[i]);
	}
	}
	}


	void RuntimeProfiler::NotifyTick() {
	#ifdef V8_TARGET_ARCH_IA32
	if (FLAG_count_based_interrupts) return;
	#endif
	isolate_->stack_guard()->RequestRuntimeProfilerTick();
	}


	void RuntimeProfiler::SetUp() {
	ASSERT(has_been_globally_set_up_);
	if (!FLAG_watch_ic_patching) {
	ClearSampleBuffer();
	}
	// If the ticker hasn't already started, make sure to do so to get
	// the ticks for the runtime profiler.
	if (IsEnabled()) isolate_->logger()->EnsureTickerStarted();
	}


	void RuntimeProfiler::Reset() {
	if (FLAG_watch_ic_patching) {
	total_code_generated_ = 0;
	} else { // !FLAG_watch_ic_patching
	sampler_threshold_ = kSamplerThresholdInit;
	sampler_threshold_size_factor_ = kSamplerThresholdSizeFactorInit;
	sampler_ticks_until_threshold_adjustment_ =
	kSamplerTicksBetweenThresholdAdjustment;
	}
	}


	void RuntimeProfiler::TearDown() {
	// Nothing to do.
	}


	int RuntimeProfiler::SamplerWindowSize() {
	return kSamplerWindowSize;
	}


	// Update the pointers in the sampler window after a GC.
	void RuntimeProfiler::UpdateSamplesAfterScavenge() {
	for (int i = 0; i < kSamplerWindowSize; i++) {
	Object* function = sampler_window_[i];
	if (function != NULL && isolate_->heap()->InNewSpace(function)) {
	MapWord map_word = HeapObject::cast(function)->map_word();
	if (map_word.IsForwardingAddress()) {
	sampler_window_[i] = map_word.ToForwardingAddress();
	} else {
	sampler_window_[i] = NULL;
	}
	}
	}
	}


	void RuntimeProfiler::HandleWakeUp(Isolate* isolate) {
	// The profiler thread must still be waiting.
	ASSERT(NoBarrier_Load(&state_) >= 0);
	// In IsolateEnteredJS we have already incremented the counter and
	// undid the decrement done by the profiler thread. Increment again
	// to get the right count of active isolates.
	NoBarrier_AtomicIncrement(&state_, 1);
	semaphore_->Signal();
	}


	bool RuntimeProfiler::IsSomeIsolateInJS() {
	return NoBarrier_Load(&state_) > 0;
	}


	bool RuntimeProfiler::WaitForSomeIsolateToEnterJS() {
	Atomic32 old_state = NoBarrier_CompareAndSwap(&state_, 0, -1);
	ASSERT(old_state >= -1);
	if (old_state != 0) return false;
	semaphore_->Wait();
	return true;
	}


	void RuntimeProfiler::StopRuntimeProfilerThreadBeforeShutdown(Thread* thread) {
	// Do a fake increment. If the profiler is waiting on the semaphore,
	// the returned state is 0, which can be left as an initial state in
	// case profiling is restarted later. If the profiler is not
	// waiting, the increment will prevent it from waiting, but has to
	// be undone after the profiler is stopped.
	Atomic32 new_state = NoBarrier_AtomicIncrement(&state_, 1);
	ASSERT(new_state >= 0);
	if (new_state == 0) {
	// The profiler thread is waiting. Wake it up. It must check for
	// stop conditions before attempting to wait again.
	semaphore_->Signal();
	}
	thread->Join();
	// The profiler thread is now stopped. Undo the increment in case it
	// was not waiting.
	if (new_state != 0) {
	NoBarrier_AtomicIncrement(&state_, -1);
	}
	}


	void RuntimeProfiler::RemoveDeadSamples() {
	for (int i = 0; i < kSamplerWindowSize; i++) {
	Object* function = sampler_window_[i];
	if (function != NULL &&
	!Marking::MarkBitFrom(HeapObject::cast(function)).Get()) {
	sampler_window_[i] = NULL;
	}
	}
	}


	void RuntimeProfiler::UpdateSamplesAfterCompact(ObjectVisitor* visitor) {
	for (int i = 0; i < kSamplerWindowSize; i++) {
	visitor->VisitPointer(&sampler_window_[i]);
	}
	}


	bool RuntimeProfilerRateLimiter::SuspendIfNecessary() {
	if (!RuntimeProfiler::IsSomeIsolateInJS()) {
	return RuntimeProfiler::WaitForSomeIsolateToEnterJS();
	}
	return false;
	}


	} } // namespace v8::internal