Commit b72d3e8a authored by Han Shen's avatar Han Shen
Browse files

Earmark extra space for VSX.

Backend specific optimization for PPC VSX reads 16 bytes, whereas arm neon /
sse2 only reads <= 8 bytes. Although the extra bytes read are actually never
used, this is not a warrant for groping around.  Fixed by allocating more when
building for VSX. This is reported by asan.

Also note - PPC does have assembly that loads 64-bit content from memory - lxsdx
loads one 64-bit doubleword (whereas lxvd2x loads two 64-bit doubleword) from
memory. However, we only have "vec_vsx_ld" builtins that mapped to lxvd2x, no
builtins to lxsdx. The only way to access lxsdx is through inline assembly,
which does not fit well in the origin paradigm.

Refer:
  vsx:
    vpx_tm_predictor_4x4_vsx @ third_party/libvpx/git_root/vpx_dsp/ppc/intrapred_vsx.c
  neon:
    vpx_tm_predictor_4x4_neon @ third_party/libvpx/git_root/vpx_dsp/arm/intrapred_neon_asm.asm
  sse2:
    tm_predictor_4x4 @ third_party/libvpx/git_root/vpx_dsp/x86/intrapred_sse2.asm

BUG=b/63112600

Tested:
  asan tests passed.

Change-Id: I5f74b56e35c05b67851de8b5530aece213f2ce9d
parent 89a116f4
......@@ -71,8 +71,16 @@ void vp8_build_intra_predictors_mbuv_s(
unsigned char *uleft, unsigned char *vleft, int left_stride,
unsigned char *upred_ptr, unsigned char *vpred_ptr, int pred_stride) {
MB_PREDICTION_MODE uvmode = x->mode_info_context->mbmi.uv_mode;
#if HAVE_VSX
/* Power PC implementation uses "vec_vsx_ld" to read 16 bytes from
uleft_col and vleft_col. Play it safe by reserving enough stack
space here. */
unsigned char uleft_col[16];
unsigned char vleft_col[16];
#else
unsigned char uleft_col[8];
unsigned char vleft_col[8];
#endif
int i;
intra_pred_fn fn;
......
......@@ -40,7 +40,15 @@ void vp8_intra4x4_predict(unsigned char *above, unsigned char *yleft,
int left_stride, B_PREDICTION_MODE b_mode,
unsigned char *dst, int dst_stride,
unsigned char top_left) {
unsigned char Aboveb[12], *Above = Aboveb + 4;
/* Power PC implementation uses "vec_vsx_ld" to read 16 bytes from
Above (aka, Aboveb + 4). Play it safe by reserving enough stack
space here. Similary for "Left". */
#if HAVE_VSX
unsigned char Aboveb[20];
#else
unsigned char Aboveb[12];
#endif
unsigned char *Above = Aboveb + 4;
#if HAVE_NEON
// Neon intrinsics are unable to load 32 bits, or 4 8 bit values. Instead, it
// over reads but does not use the extra 4 values.
......@@ -50,6 +58,8 @@ void vp8_intra4x4_predict(unsigned char *above, unsigned char *yleft,
// indeed read, they are not used.
vp8_zero_array(Left, 8);
#endif // VPX_WITH_ASAN
#elif HAVE_VSX
unsigned char Left[16];
#else
unsigned char Left[4];
#endif // HAVE_NEON
......
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