Make size of sample variable based on the profile depth flag

runtime/vm/profiler.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/utils.h"
 
 #include "vm/allocation.h"
 #include "vm/atomic.h"
 #include "vm/code_patcher.h"
 #include "vm/isolate.h"
@@ skipping 28 matching lines @@
 DEFINE_FLAG(bool, profile_native_stack, true,
             "Use native stack in profiler.");
 
 bool Profiler::initialized_ = false;
 SampleBuffer* Profiler::sample_buffer_ = NULL;
 
 void Profiler::InitOnce() {
   // Place some sane restrictions on user controlled flags.
   SetSamplePeriod(FLAG_profile_period);
   SetSampleDepth(FLAG_profile_depth);
+  Sample::InitOnce();
   if (!FLAG_profile) {
     return;
   }
   ASSERT(!initialized_);
   sample_buffer_ = new SampleBuffer();
   NativeSymbolResolver::InitOnce();
   ThreadInterrupter::SetInterruptPeriod(FLAG_profile_period);
   ThreadInterrupter::Startup();
   initialized_ = true;
 }
 
 
 void Profiler::Shutdown() {
   if (!FLAG_profile) {
     return;
   }
   ASSERT(initialized_);
   ThreadInterrupter::Shutdown();
   NativeSymbolResolver::ShutdownOnce();
 }
 
 
 void Profiler::SetSampleDepth(intptr_t depth) {
   const int kMinimumDepth = 1;
-  const int kMaximumDepth = kSampleFramesSize - 1;
+  const int kMaximumDepth = 255;
   if (depth < kMinimumDepth) {
     FLAG_profile_depth = kMinimumDepth;
   } else if (depth > kMaximumDepth) {
     FLAG_profile_depth = kMaximumDepth;
   } else {
     FLAG_profile_depth = depth;
   }
 }
 
 
@@ skipping 1526 matching lines @@
   if (block_count_ < 0) {
     FATAL("Too many calls to Dart_IsolateUnblocked.");
   }
   if (!blocked()) {
     // We just unblocked this isolate, wake up the thread interrupter.
     ThreadInterrupter::WakeUp();
   }
 }
 
 
+intptr_t Sample::pcs_length_ = 0;
+intptr_t Sample::instance_size_ = 0;
+
+
+void Sample::InitOnce() {
+  ASSERT(FLAG_profile_depth >= 1);
+  pcs_length_ = FLAG_profile_depth;
+  instance_size_ =
+      sizeof(Sample) + (sizeof(uword) * pcs_length_);  // NOLINT.
+}
+
+
+uword* Sample::GetPCArray() const {
+  return reinterpret_cast<uword*>(
+        reinterpret_cast<uintptr_t>(this) + sizeof(*this));
+}
+
+
+// Get stack trace entry.
+uword Sample::At(intptr_t i) const {
+  ASSERT(i >= 0);
+  ASSERT(i < pcs_length_);
+  uword* pcs = GetPCArray();
+  return pcs[i];
+}
+
+
+// Set stack trace entry.
+void Sample::SetAt(intptr_t i, uword pc) {
+  ASSERT(i >= 0);
+  ASSERT(i < pcs_length_);
+  uword* pcs = GetPCArray();
+  pcs[i] = pc;
+}
+
+
+SampleBuffer::SampleBuffer(intptr_t capacity) {
+  ASSERT(Sample::instance_size() > 0);
+  samples_ = reinterpret_cast<Sample*>(
+      calloc(capacity, Sample::instance_size()));
+  capacity_ = capacity;
+  cursor_ = 0;
+}
+
+
+Sample* SampleBuffer::At(intptr_t idx) const {
+  ASSERT(idx >= 0);
+  ASSERT(idx < capacity_);
+  intptr_t offset = idx * Sample::instance_size();
+  uint8_t* samples = reinterpret_cast<uint8_t*>(samples_);
+  return reinterpret_cast<Sample*>(samples + offset);
+}
+
+
 Sample* SampleBuffer::ReserveSample() {
   ASSERT(samples_ != NULL);
   uintptr_t cursor = AtomicOperations::FetchAndIncrement(&cursor_);
   // Map back into sample buffer range.
   cursor = cursor % capacity_;
   return At(cursor);
 }
 
 
 class ProfilerDartStackWalker : public ValueObject {
@@ skipping 232 matching lines @@
       ProfilerDartStackWalker stackWalker(sample);
       stackWalker.walk();
     } else {
       // TODO(johnmccutchan): Support collecting only Dart frames with
       // ProfilerNativeStackWalker.
     }
   }
 }
 
 }  // namespace dart