[Bug 739354] New: program-c: loadpq broken on big-endian systems (makes gst volume tests fail for f64)

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=739354
  GStreamer | orc | git

           Summary: program-c: loadpq broken on big-endian systems (makes
                    gst volume tests fail for f64)
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: orc
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: t.i.m at zen.co.uk
         QAContact: gstreamer-bugs at lists.freedesktop.org
                CC: ds at schleef.org
     GNOME version: ---


In -base/tests/check/elements/volume.c the f64 format tests fail on powerpc
because orc generates broken backup code:

-base/gst/volume/tmp-orc.c:

static void
_backup_volume_orc_scalarmultiply_f64_ns (OrcExecutor * ORC_RESTRICT ex)
{
  ...
  orc_union64 var33;

  /* 1: loadpq */
  var33.i = (ex->params[24] & 0xffffffff) | ((orc_uint64)(ex->params[24 +
(ORC_VAR_T1 - ORC_VAR_P1)]) << 32);

  for (i = 0; i < n; i++) {
    ...
  }

}

void
volume_orc_scalarmultiply_f64_ns (double * ORC_RESTRICT d1, double p1, int n)
{
  ...
  ex->arrays[ORC_VAR_A2] = c;
  ex->program = 0;

  ex->n = n;
  ex->arrays[ORC_VAR_D1] = d1;
  {
    orc_union64 tmp;
    tmp.f = p1;
    ex->params[ORC_VAR_P1] = tmp.x2[0];  <====
    ex->params[ORC_VAR_T1] = tmp.x2[1];  <====
  }
  ....
}

It doesn't save/restore the 64-bit double by which to multiply all the samples
with correctly on big-endian architectures, the higher/upper 32-bits are
swapped, which makes everything something around 0 after processing.

What I'm not sure about is whether the value is stored incorrectly, or read
incorrectly.

There's a comment in struct _OrcExecutor saying

  /* high half of params is stored in params[ORC_VAR_T1..] */

which I would interpret such that the values should be stored differently on
big-endian. (But then I don't really understand why they're stored that way via
.x2 in the first place I suppose).

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