[Bug 742843] New: ORC compiler is disabled on the iOS devices

Tue Jan 13 04:41:59 PST 2015

https://bugzilla.gnome.org/show_bug.cgi?id=742843
  GStreamer | orc | 1.4.5

           Summary: ORC compiler is disabled on the iOS devices
    Classification: Platform
           Product: GStreamer
           Version: 1.4.5
        OS/Version: Mac OS
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: orc
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: denis.shmyrov at gmail.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
                CC: ds at schleef.org
     GNOME version: ---

Here’s the ORC output in log. Init stage:

ORC: INFO: orcdebug.c(70): void _orc_debug_init()(): orc-0.4.23.1 debug init
ORC: INFO: orcprogram-neon.c(129): void orc_neon_init()(): marking neon backend
non-executable

and then there’s continuous warnings like this one during the pipeline
execution:

ORC: WARNING: orccompiler.c(392): OrcCompileResult
orc_program_compile_full(OrcProgram *, OrcTarget *, unsigned int)(): program
orc_combine4_12xn_u8 failed to compile, reason: Compilation disabled, using
emulation

There’s nothing more specific about why NEON is disabled but tracing with
debugger shows that orc_arm_get_cpu_flags in orccpu-arm.c has practically no
executable code for IOS (one branch is #if'd for linux only and one for
Android-only) and will always return 0 (which means no NEON support).
Verified on iPad 3rd gen and iPad mini 1st gen.

If i apply a hack to orc_arm_get_cpu_flags to return NEON flag support ORC
compiler is enabled and works well on the iPad mini 1st gen. On the iPad 3rd
gen i’m getting segfaults from different gstreamer->orc bridges like
video_orc_chroma_up_v2_u8 (videoscale plugin), video_test_src_orc_splat_u32
(videotestsrc) etc.
per hw info iPad 3rd get uses A5x chip while iPad mini (1st gen) uses A5 so
that’s really strange why orc works ok with 2nd but not with 1st.

Example stack trace for the iPad 3 segfault:

#0    0x02ec8e90 in 0x02ec8e90 ()
#1    0x003d7138 in video_test_src_orc_splat_u32 at
/Users/D/cerbero/sources/ios_universal/armv7/gst-plugins-base-1.0-static-1.5/gst/videotestsrc/tmp-orc.c:215
#2    0x003d71fc in gst_video_test_src_smpte at
/Users/D/cerbero/sources/ios_universal/armv7/gst-plugins-base-1.0-static-1.5/gst/videotestsrc/videotestsrc.c:350
#3    0x003d6c9a in gst_video_test_src_fill at
/Users/D/cerbero/sources/ios_universal/armv7/gst-plugins-base-1.0-static-1.5/gst/videotestsrc/gstvideotestsrc.c:951
#4    0x00a60a80 in gst_base_src_default_create at
/Users/D/cerbero/sources/ios_universal/armv7/gstreamer-1.0-1.5/libs/gst/base/gstbasesrc.c:1482
#5    0x00a5d0ae in gst_base_src_get_range at
/Users/D/cerbero/sources/ios_universal/armv7/gstreamer-1.0-1.5/libs/gst/base/gstbasesrc.c:2455
#6    0x00a5c8de in gst_base_src_loop at
/Users/D/cerbero/sources/ios_universal/armv7/gstreamer-1.0-1.5/libs/gst/base/gstbasesrc.c:2731
#7    0x00acaeec in gst_task_func at
/Users/D/cerbero/sources/ios_universal/armv7/gstreamer-1.0-1.5/gst/gsttask.c:316
#8    0x0093f26c in g_thread_pool_thread_proxy at
/Users/D/cerbero/sources/ios_universal/armv7/glib-2.42.0/glib/gthreadpool.c:307
#9    0x00942156 in g_thread_proxy at
/Users/D/cerbero/sources/ios_universal/armv7/glib-2.42.0/glib/gthread.c:764
#10    0x38502e66 in _pthread_body ()
#11    0x38502dda in _pthread_start ()

Variables for frame 1:

d1    guint8 *    ""    0x03181000
p1    int    -2139034625    -2139034625
n    int    91    91
_ex    OrcExecutor        
program    OrcProgram *    NULL    0x00000000
n    int    91    91
counter1    int    108279884    108279884
counter2    int    460800    460800
counter3    int    16    16
arrays    void *[64]        
params    int [64]        
accumulators    int [4]        
ex    OrcExecutor *    NULL    0x00000000
program    OrcProgram *    NULL    
n    int        
counter1    int        
counter2    int        
counter3    int        
arrays    void *[64]        
params    int [64]        
accumulators    int [4]        
func    void (*)(OrcExecutor *)    NULL    
p    OrcProgram *    NULL    

Code 

void
video_test_src_orc_splat_u32 (guint8 * ORC_RESTRICT d1, int p1, int n)
{
  OrcExecutor _ex, *ex = &_ex;
  static volatile int p_inited = 0;
  static OrcCode *c = 0;
  void (*func) (OrcExecutor *);

  if (!p_inited) {
    orc_once_mutex_lock ();
    if (!p_inited) {
      OrcProgram *p;

#if 1
      static const orc_uint8 bc[] = {
        1, 9, 28, 118, 105, 100, 101, 111, 95, 116, 101, 115, 116, 95, 115,
114, 
        99, 95, 111, 114, 99, 95, 115, 112, 108, 97, 116, 95, 117, 51, 50, 11, 
        4, 4, 16, 4, 128, 0, 24, 2, 0, 
      };
      p = orc_program_new_from_static_bytecode (bc);
      orc_program_set_backup_function (p,
_backup_video_test_src_orc_splat_u32);
#else
      p = orc_program_new ();
      orc_program_set_name (p, "video_test_src_orc_splat_u32");
      orc_program_set_backup_function (p,
_backup_video_test_src_orc_splat_u32);
      orc_program_add_destination (p, 4, "d1");
      orc_program_add_parameter (p, 4, "p1");

      orc_program_append_2 (p, "storel", 0, ORC_VAR_D1, ORC_VAR_P1, ORC_VAR_D1,
ORC_VAR_D1);
#endif

      orc_program_compile (p);
      c = orc_program_take_code (p);
      orc_program_free (p);
    }
    p_inited = TRUE;
    orc_once_mutex_unlock ();
  }
  ex->arrays[ORC_VAR_A2] = c;
  ex->program = 0;

  ex->n = n;
  ex->arrays[ORC_VAR_D1] = d1;
  ex->params[ORC_VAR_P1] = p1;

  func = c->exec; 
  func (ex);                 <---------------- SEGFAUL HERE
}

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