1// Copyright 2012 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "src/v8.h"
6
7#include "src/runtime-profiler.h"
8
9#include "src/assembler.h"
10#include "src/bootstrapper.h"
11#include "src/code-stubs.h"
12#include "src/compilation-cache.h"
13#include "src/execution.h"
14#include "src/full-codegen.h"
15#include "src/global-handles.h"
16#include "src/isolate-inl.h"
17#include "src/mark-compact.h"
18#include "src/platform.h"
19#include "src/scopeinfo.h"
20
21namespace v8 {
22namespace internal {
23
24
25// Number of times a function has to be seen on the stack before it is
26// optimized.
27static const int kProfilerTicksBeforeOptimization = 2;
28// If the function optimization was disabled due to high deoptimization count,
29// but the function is hot and has been seen on the stack this number of times,
30// then we try to reenable optimization for this function.
31static const int kProfilerTicksBeforeReenablingOptimization = 250;
32// If a function does not have enough type info (according to
33// FLAG_type_info_threshold), but has seen a huge number of ticks,
34// optimize it as it is.
35static const int kTicksWhenNotEnoughTypeInfo = 100;
36// We only have one byte to store the number of ticks.
37STATIC_ASSERT(kProfilerTicksBeforeOptimization < 256);
38STATIC_ASSERT(kProfilerTicksBeforeReenablingOptimization < 256);
39STATIC_ASSERT(kTicksWhenNotEnoughTypeInfo < 256);
40
41// Maximum size in bytes of generate code for a function to allow OSR.
42static const int kOSRCodeSizeAllowanceBase =
43    100 * FullCodeGenerator::kCodeSizeMultiplier;
44
45static const int kOSRCodeSizeAllowancePerTick =
46    4 * FullCodeGenerator::kCodeSizeMultiplier;
47
48// Maximum size in bytes of generated code for a function to be optimized
49// the very first time it is seen on the stack.
50static const int kMaxSizeEarlyOpt =
51    5 * FullCodeGenerator::kCodeSizeMultiplier;
52
53
54RuntimeProfiler::RuntimeProfiler(Isolate* isolate)
55    : isolate_(isolate),
56      any_ic_changed_(false) {
57}
58
59
60static void GetICCounts(Code* shared_code,
61                        int* ic_with_type_info_count,
62                        int* ic_total_count,
63                        int* percentage) {
64  *ic_total_count = 0;
65  *ic_with_type_info_count = 0;
66  Object* raw_info = shared_code->type_feedback_info();
67  if (raw_info->IsTypeFeedbackInfo()) {
68    TypeFeedbackInfo* info = TypeFeedbackInfo::cast(raw_info);
69    *ic_with_type_info_count = info->ic_with_type_info_count();
70    *ic_total_count = info->ic_total_count();
71  }
72  *percentage = *ic_total_count > 0
73      ? 100 * *ic_with_type_info_count / *ic_total_count
74      : 100;
75}
76
77
78void RuntimeProfiler::Optimize(JSFunction* function, const char* reason) {
79  ASSERT(function->IsOptimizable());
80
81  if (FLAG_trace_opt && function->PassesFilter(FLAG_hydrogen_filter)) {
82    PrintF("[marking ");
83    function->ShortPrint();
84    PrintF(" for recompilation, reason: %s", reason);
85    if (FLAG_type_info_threshold > 0) {
86      int typeinfo, total, percentage;
87      GetICCounts(function->shared()->code(), &typeinfo, &total, &percentage);
88      PrintF(", ICs with typeinfo: %d/%d (%d%%)", typeinfo, total, percentage);
89    }
90    PrintF("]\n");
91  }
92
93
94  if (isolate_->concurrent_recompilation_enabled() &&
95      !isolate_->bootstrapper()->IsActive()) {
96    if (isolate_->concurrent_osr_enabled() &&
97        isolate_->optimizing_compiler_thread()->IsQueuedForOSR(function)) {
98      // Do not attempt regular recompilation if we already queued this for OSR.
99      // TODO(yangguo): This is necessary so that we don't install optimized
100      // code on a function that is already optimized, since OSR and regular
101      // recompilation race.  This goes away as soon as OSR becomes one-shot.
102      return;
103    }
104    ASSERT(!function->IsInOptimizationQueue());
105    function->MarkForConcurrentOptimization();
106  } else {
107    // The next call to the function will trigger optimization.
108    function->MarkForOptimization();
109  }
110}
111
112
113void RuntimeProfiler::AttemptOnStackReplacement(JSFunction* function) {
114  // See AlwaysFullCompiler (in compiler.cc) comment on why we need
115  // Debug::has_break_points().
116  if (!FLAG_use_osr ||
117      isolate_->DebuggerHasBreakPoints() ||
118      function->IsBuiltin()) {
119    return;
120  }
121
122  SharedFunctionInfo* shared = function->shared();
123  // If the code is not optimizable, don't try OSR.
124  if (!shared->code()->optimizable()) return;
125
126  // We are not prepared to do OSR for a function that already has an
127  // allocated arguments object.  The optimized code would bypass it for
128  // arguments accesses, which is unsound.  Don't try OSR.
129  if (shared->uses_arguments()) return;
130
131  // We're using on-stack replacement: patch the unoptimized code so that
132  // any back edge in any unoptimized frame will trigger on-stack
133  // replacement for that frame.
134  if (FLAG_trace_osr) {
135    PrintF("[OSR - patching back edges in ");
136    function->PrintName();
137    PrintF("]\n");
138  }
139
140  BackEdgeTable::Patch(isolate_, shared->code());
141}
142
143
144void RuntimeProfiler::OptimizeNow() {
145  HandleScope scope(isolate_);
146
147  if (isolate_->DebuggerHasBreakPoints()) return;
148
149  DisallowHeapAllocation no_gc;
150
151  // Run through the JavaScript frames and collect them. If we already
152  // have a sample of the function, we mark it for optimizations
153  // (eagerly or lazily).
154  int frame_count = 0;
155  int frame_count_limit = FLAG_frame_count;
156  for (JavaScriptFrameIterator it(isolate_);
157       frame_count++ < frame_count_limit && !it.done();
158       it.Advance()) {
159    JavaScriptFrame* frame = it.frame();
160    JSFunction* function = frame->function();
161
162    SharedFunctionInfo* shared = function->shared();
163    Code* shared_code = shared->code();
164
165    List<JSFunction*> functions(4);
166    frame->GetFunctions(&functions);
167    for (int i = functions.length(); --i >= 0; ) {
168      SharedFunctionInfo* shared_function_info = functions[i]->shared();
169      int ticks = shared_function_info->profiler_ticks();
170      if (ticks < Smi::kMaxValue) {
171        shared_function_info->set_profiler_ticks(ticks + 1);
172      }
173    }
174
175    if (shared_code->kind() != Code::FUNCTION) continue;
176    if (function->IsInOptimizationQueue()) continue;
177
178    if (FLAG_always_osr &&
179        shared_code->allow_osr_at_loop_nesting_level() == 0) {
180      // Testing mode: always try an OSR compile for every function.
181      for (int i = 0; i < Code::kMaxLoopNestingMarker; i++) {
182        // TODO(titzer): fix AttemptOnStackReplacement to avoid this dumb loop.
183        shared_code->set_allow_osr_at_loop_nesting_level(i);
184        AttemptOnStackReplacement(function);
185      }
186      // Fall through and do a normal optimized compile as well.
187    } else if (!frame->is_optimized() &&
188        (function->IsMarkedForOptimization() ||
189         function->IsMarkedForConcurrentOptimization() ||
190         function->IsOptimized())) {
191      // Attempt OSR if we are still running unoptimized code even though the
192      // the function has long been marked or even already been optimized.
193      int ticks = shared_code->profiler_ticks();
194      int allowance = kOSRCodeSizeAllowanceBase +
195                      ticks * kOSRCodeSizeAllowancePerTick;
196      if (shared_code->CodeSize() > allowance) {
197        if (ticks < 255) shared_code->set_profiler_ticks(ticks + 1);
198      } else {
199        int nesting = shared_code->allow_osr_at_loop_nesting_level();
200        if (nesting < Code::kMaxLoopNestingMarker) {
201          int new_nesting = nesting + 1;
202          shared_code->set_allow_osr_at_loop_nesting_level(new_nesting);
203          AttemptOnStackReplacement(function);
204        }
205      }
206      continue;
207    }
208
209    // Only record top-level code on top of the execution stack and
210    // avoid optimizing excessively large scripts since top-level code
211    // will be executed only once.
212    const int kMaxToplevelSourceSize = 10 * 1024;
213    if (shared->is_toplevel() &&
214        (frame_count > 1 || shared->SourceSize() > kMaxToplevelSourceSize)) {
215      continue;
216    }
217
218    // Do not record non-optimizable functions.
219    if (shared->optimization_disabled()) {
220      if (shared->deopt_count() >= FLAG_max_opt_count) {
221        // If optimization was disabled due to many deoptimizations,
222        // then check if the function is hot and try to reenable optimization.
223        int ticks = shared_code->profiler_ticks();
224        if (ticks >= kProfilerTicksBeforeReenablingOptimization) {
225          shared_code->set_profiler_ticks(0);
226          shared->TryReenableOptimization();
227        } else {
228          shared_code->set_profiler_ticks(ticks + 1);
229        }
230      }
231      continue;
232    }
233    if (!function->IsOptimizable()) continue;
234
235    int ticks = shared_code->profiler_ticks();
236
237    if (ticks >= kProfilerTicksBeforeOptimization) {
238      int typeinfo, total, percentage;
239      GetICCounts(shared_code, &typeinfo, &total, &percentage);
240      if (percentage >= FLAG_type_info_threshold) {
241        // If this particular function hasn't had any ICs patched for enough
242        // ticks, optimize it now.
243        Optimize(function, "hot and stable");
244      } else if (ticks >= kTicksWhenNotEnoughTypeInfo) {
245        Optimize(function, "not much type info but very hot");
246      } else {
247        shared_code->set_profiler_ticks(ticks + 1);
248        if (FLAG_trace_opt_verbose) {
249          PrintF("[not yet optimizing ");
250          function->PrintName();
251          PrintF(", not enough type info: %d/%d (%d%%)]\n",
252                 typeinfo, total, percentage);
253        }
254      }
255    } else if (!any_ic_changed_ &&
256               shared_code->instruction_size() < kMaxSizeEarlyOpt) {
257      // If no IC was patched since the last tick and this function is very
258      // small, optimistically optimize it now.
259      Optimize(function, "small function");
260    } else {
261      shared_code->set_profiler_ticks(ticks + 1);
262    }
263  }
264  any_ic_changed_ = false;
265}
266
267
268} }  // namespace v8::internal
269