Add SSE optimizations to AudioRendererMixer.

content/renderer/media/audio_device_thread.cc

Index: content/renderer/media/audio_device_thread.cc
diff --git a/content/renderer/media/audio_device_thread.cc b/content/renderer/media/audio_device_thread.cc
index 64a4cd62ed0729117412e4d7080de83fc59b871f..bd0b7da354d7d6adb897d6b35abd6ad3ff0c7e3d 100644
--- a/content/renderer/media/audio_device_thread.cc
+++ b/content/renderer/media/audio_device_thread.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/logging.h"
+#include "base/memory/aligned_memory.h"

[Ami GONE FROM CHROMIUM, 2012/07/27 17:33:11]

CL description says "without the hassle of 32-byte align" - I think you could be
clearer about the requirements/non-requirements.

[DaleCurtis, 2012/07/27 21:23:42]

There I'm specifically referring to versus FFMpeg's vector_fmac.  I'll add some
info about requiring a 16-byte alignment.

 #include "base/message_loop.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/thread_restrictions.h"
@@ -185,7 +186,7 @@ AudioDeviceThread::Callback::Callback(
 
 AudioDeviceThread::Callback::~Callback() {
   for (size_t i = 0; i < audio_data_.size(); ++i)
-    delete [] audio_data_[i];
+    base::AlignedFree(audio_data_[i]);
 }
 
 void AudioDeviceThread::Callback::InitializeOnAudioThread() {
@@ -194,9 +195,10 @@ void AudioDeviceThread::Callback::InitializeOnAudioThread() {
   MapSharedMemory();
   DCHECK(shared_memory_.memory() != NULL);
 
+  // Allocate buffer with a 16-byte alignment to allow SSE optimizations.
   audio_data_.reserve(audio_parameters_.channels());
   for (int i = 0; i < audio_parameters_.channels(); ++i) {
-    float* channel_data = new float[audio_parameters_.frames_per_buffer()];
-    audio_data_.push_back(channel_data);
+    audio_data_.push_back(static_cast<float*>(base::AlignedAlloc(
+        sizeof(float) * audio_parameters_.frames_per_buffer(), 16)));
   }
 }