vp9 decoder: row-based multi-threaded loopfilter

Implemented parallel loopfiltering, which uses existing tile-
decoding threads. Each thread works on one row, and when that row
is loopfiltered, it moves to next unattended row. To ensure the
correct filtering order, threads are synchronized and one
superblock is filtered only if the superblocks it depends on are
filtered already.

To reduce synchronization overhead and speed up the decoder, we use
nsync > 1 for high resolution.

Performance tests:
1. on desktop:
8-tile 4k video using 8 threads, speedup: 70% - 80%
4-tile HD video using 4 threads, speedup: ~35%
2. on mobile device(Nexus 7):
4-tile 1080p video using 4 threads, speedup: 18% - 25%
4-tile 1080p video using 2 threads, speedup: 10% - 15%

Change-Id: If54b4a11960dd706c22d5ad145ad94156031f36a

1 files changed, 0 insertions, 110 deletions

diff --git a/vp9/decoder/vp9_thread.c b/vp9/decoder/vp9_thread.c
index d953e72b3..5d31d3d98 100644
--- a/vp9/decoder/vp9_thread.c
+++ b/vp9/decoder/vp9_thread.c
@@ -24,116 +24,6 @@ extern "C" {
 
 #if CONFIG_MULTITHREAD
 
-#if defined(_WIN32)
-
-//------------------------------------------------------------------------------
-// simplistic pthread emulation layer
-
-#include <process.h>  // NOLINT
-
-// _beginthreadex requires __stdcall
-#define THREADFN unsigned int __stdcall
-#define THREAD_RETURN(val) (unsigned int)((DWORD_PTR)val)
-
-static int pthread_create(pthread_t* const thread, const void* attr,
-                          unsigned int (__stdcall *start)(void*), void* arg) {
-  (void)attr;
-  *thread = (pthread_t)_beginthreadex(NULL,   /* void *security */
-                                      0,      /* unsigned stack_size */
-                                      start,
-                                      arg,
-                                      0,      /* unsigned initflag */
-                                      NULL);  /* unsigned *thrdaddr */
-  if (*thread == NULL) return 1;
-  SetThreadPriority(*thread, THREAD_PRIORITY_ABOVE_NORMAL);
-  return 0;
-}
-
-static int pthread_join(pthread_t thread, void** value_ptr) {
-  (void)value_ptr;
-  return (WaitForSingleObject(thread, INFINITE) != WAIT_OBJECT_0 ||
-          CloseHandle(thread) == 0);
-}
-
-// Mutex
-static int pthread_mutex_init(pthread_mutex_t* const mutex, void* mutexattr) {
-  (void)mutexattr;
-  InitializeCriticalSection(mutex);
-  return 0;
-}
-
-static int pthread_mutex_lock(pthread_mutex_t* const mutex) {
-  EnterCriticalSection(mutex);
-  return 0;
-}
-
-static int pthread_mutex_unlock(pthread_mutex_t* const mutex) {
-  LeaveCriticalSection(mutex);
-  return 0;
-}
-
-static int pthread_mutex_destroy(pthread_mutex_t* const mutex) {
-  DeleteCriticalSection(mutex);
-  return 0;
-}
-
-// Condition
-static int pthread_cond_destroy(pthread_cond_t* const condition) {
-  int ok = 1;
-  ok &= (CloseHandle(condition->waiting_sem_) != 0);
-  ok &= (CloseHandle(condition->received_sem_) != 0);
-  ok &= (CloseHandle(condition->signal_event_) != 0);
-  return !ok;
-}
-
-static int pthread_cond_init(pthread_cond_t* const condition, void* cond_attr) {
-  (void)cond_attr;
-  condition->waiting_sem_ = CreateSemaphore(NULL, 0, 1, NULL);
-  condition->received_sem_ = CreateSemaphore(NULL, 0, 1, NULL);
-  condition->signal_event_ = CreateEvent(NULL, FALSE, FALSE, NULL);
-  if (condition->waiting_sem_ == NULL ||
-      condition->received_sem_ == NULL ||
-      condition->signal_event_ == NULL) {
-    pthread_cond_destroy(condition);
-    return 1;
-  }
-  return 0;
-}
-
-static int pthread_cond_signal(pthread_cond_t* const condition) {
-  int ok = 1;
-  if (WaitForSingleObject(condition->waiting_sem_, 0) == WAIT_OBJECT_0) {
-    // a thread is waiting in pthread_cond_wait: allow it to be notified
-    ok = SetEvent(condition->signal_event_);
-    // wait until the event is consumed so the signaler cannot consume
-    // the event via its own pthread_cond_wait.
-    ok &= (WaitForSingleObject(condition->received_sem_, INFINITE) !=
-           WAIT_OBJECT_0);
-  }
-  return !ok;
-}
-
-static int pthread_cond_wait(pthread_cond_t* const condition,
-                             pthread_mutex_t* const mutex) {
-  int ok;
-  // note that there is a consumer available so the signal isn't dropped in
-  // pthread_cond_signal
-  if (!ReleaseSemaphore(condition->waiting_sem_, 1, NULL))
-    return 1;
-  // now unlock the mutex so pthread_cond_signal may be issued
-  pthread_mutex_unlock(mutex);
-  ok = (WaitForSingleObject(condition->signal_event_, INFINITE) ==
-        WAIT_OBJECT_0);
-  ok &= ReleaseSemaphore(condition->received_sem_, 1, NULL);
-  pthread_mutex_lock(mutex);
-  return !ok;
-}
-
-#else  // _WIN32
-# define THREADFN void*
-# define THREAD_RETURN(val) val
-#endif
-
 //------------------------------------------------------------------------------
 
 static THREADFN thread_loop(void *ptr) {    // thread loop