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// 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/execution/runtime-profiler.h"
#include "src/base/platform/platform.h"
#include "src/codegen/assembler.h"
#include "src/codegen/compilation-cache.h"
#include "src/codegen/compiler.h"
#include "src/execution/execution.h"
#include "src/execution/frames-inl.h"
#include "src/handles/global-handles.h"
#include "src/init/bootstrapper.h"
#include "src/interpreter/interpreter.h"
#include "src/tracing/trace-event.h"
namespace v8 {
namespace internal {
// Number of times a function has to be seen on the stack before it is
// optimized.
static const int kProfilerTicksBeforeOptimization = 2;
// The number of ticks required for optimizing a function increases with
// the size of the bytecode. This is in addition to the
// kProfilerTicksBeforeOptimization required for any function.
static const int kBytecodeSizeAllowancePerTick = 1200;
// Maximum size in bytes of generate code for a function to allow OSR.
static const int kOSRBytecodeSizeAllowanceBase = 180;
static const int kOSRBytecodeSizeAllowancePerTick = 48;
// 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 kMaxBytecodeSizeForEarlyOpt = 90;
V(DoNotOptimize, "do not optimize") \
V(HotAndStable, "hot and stable") \
V(SmallFunction, "small function")
enum class OptimizationReason : uint8_t {
#define OPTIMIZATION_REASON_CONSTANTS(Constant, message) k##Constant,
char const* OptimizationReasonToString(OptimizationReason reason) {
static char const* reasons[] = {
#define OPTIMIZATION_REASON_TEXTS(Constant, message) message,
size_t const index = static_cast<size_t>(reason);
DCHECK_LT(index, arraysize(reasons));
return reasons[index];
std::ostream& operator<<(std::ostream& os, OptimizationReason reason) {
return os << OptimizationReasonToString(reason);
RuntimeProfiler::RuntimeProfiler(Isolate* isolate)
: isolate_(isolate), any_ic_changed_(false) {}
static void TraceRecompile(JSFunction function, const char* reason,
const char* type) {
if (FLAG_trace_opt) {
PrintF("[marking ");
PrintF(" for %s recompilation, reason: %s", type, reason);
void RuntimeProfiler::Optimize(JSFunction function, OptimizationReason reason) {
DCHECK_NE(reason, OptimizationReason::kDoNotOptimize);
TraceRecompile(function, OptimizationReasonToString(reason), "optimized");
void RuntimeProfiler::AttemptOnStackReplacement(InterpretedFrame* frame,
int loop_nesting_levels) {
JSFunction function = frame->function();
SharedFunctionInfo shared = function.shared();
if (!FLAG_use_osr || !shared.IsUserJavaScript()) {
// If the code is not optimizable, don't try OSR.
if (shared.optimization_disabled()) return;
// We're using on-stack replacement: Store new loop nesting level in
// BytecodeArray header so that certain back edges in any interpreter frame
// for this bytecode will trigger on-stack replacement for that frame.
if (FLAG_trace_osr) {
PrintF("[OSR - arming back edges in ");
DCHECK_EQ(StackFrame::INTERPRETED, frame->type());
int level = frame->GetBytecodeArray().osr_loop_nesting_level();
Min(level + loop_nesting_levels, AbstractCode::kMaxLoopNestingMarker));
void RuntimeProfiler::MaybeOptimize(JSFunction function,
InterpretedFrame* frame) {
if (function.IsInOptimizationQueue()) {
if (FLAG_trace_opt_verbose) {
PrintF("[function ");
PrintF(" is already in optimization queue]\n");
if (FLAG_always_osr) {
AttemptOnStackReplacement(frame, AbstractCode::kMaxLoopNestingMarker);
// Fall through and do a normal optimized compile as well.
} else if (MaybeOSR(function, frame)) {
if (function.shared().optimization_disabled()) return;
OptimizationReason reason =
ShouldOptimize(function, function.shared().GetBytecodeArray());
if (reason != OptimizationReason::kDoNotOptimize) {
Optimize(function, reason);
bool RuntimeProfiler::MaybeOSR(JSFunction function, InterpretedFrame* frame) {
int ticks = function.feedback_vector().profiler_ticks();
// TODO(rmcilroy): Also ensure we only OSR top-level code if it is smaller
// than kMaxToplevelSourceSize.
if (function.IsMarkedForOptimization() ||
function.IsMarkedForConcurrentOptimization() ||
function.HasOptimizedCode()) {
// Attempt OSR if we are still running interpreted code even though the
// the function has long been marked or even already been optimized.
int64_t allowance =
kOSRBytecodeSizeAllowanceBase +
static_cast<int64_t>(ticks) * kOSRBytecodeSizeAllowancePerTick;
if (function.shared().GetBytecodeArray().length() <= allowance) {
return true;
return false;
OptimizationReason RuntimeProfiler::ShouldOptimize(JSFunction function,
BytecodeArray bytecode) {
int ticks = function.feedback_vector().profiler_ticks();
int ticks_for_optimization =
kProfilerTicksBeforeOptimization +
(bytecode.length() / kBytecodeSizeAllowancePerTick);
if (ticks >= ticks_for_optimization) {
return OptimizationReason::kHotAndStable;
} else if (!any_ic_changed_ &&
bytecode.length() < kMaxBytecodeSizeForEarlyOpt) {
// If no IC was patched since the last tick and this function is very
// small, optimistically optimize it now.
return OptimizationReason::kSmallFunction;
} else if (FLAG_trace_opt_verbose) {
PrintF("[not yet optimizing ");
PrintF(", not enough ticks: %d/%d and ", ticks,
if (any_ic_changed_) {
PrintF("ICs changed]\n");
} else {
PrintF(" too large for small function optimization: %d/%d]\n",
bytecode.length(), kMaxBytecodeSizeForEarlyOpt);
return OptimizationReason::kDoNotOptimize;
void RuntimeProfiler::MarkCandidatesForOptimization() {
HandleScope scope(isolate_);
if (!isolate_->use_optimizer()) return;
DisallowHeapAllocation no_gc;
// 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).
int frame_count = 0;
int frame_count_limit = FLAG_frame_count;
for (JavaScriptFrameIterator it(isolate_);
frame_count++ < frame_count_limit && !it.done(); it.Advance()) {
JavaScriptFrame* frame = it.frame();
if (!frame->is_interpreted()) continue;
JSFunction function = frame->function();
if (!function.shared().IsInterpreted()) continue;
if (!function.has_feedback_vector()) continue;
MaybeOptimize(function, InterpretedFrame::cast(frame));
// TODO(leszeks): Move this increment to before the maybe optimize checks,
// and update the tests to assume the increment has already happened.
int ticks = function.feedback_vector().profiler_ticks();
if (ticks < Smi::kMaxValue) {
function.feedback_vector().set_profiler_ticks(ticks + 1);
any_ic_changed_ = false;
} // namespace internal
} // namespace v8