[libav-bugs] [Bug 543] fate-atrac3-[123] fails on AIX when Altivec is enabled

bugzilla at libav.org bugzilla at libav.org
Sun Jul 21 18:44:19 CEST 2013


https://bugzilla.libav.org/show_bug.cgi?id=543

--- Comment #1 from Sean McGovern <gseanmcg at gmail.com> 2013-07-21 18:44:19 CEST ---
I narrowed this down to occur only when ff_vector_fmul_altivec() from
libavutil/ppc/float_dsp_altivec.c is enabled. The non-accelerated C version
works fine.

After conversing with a few people on IRC, we think that this is caused by the
static mdct_window declaration in libavcodec/atrac3.c:

static DECLARE_ALIGNED(32, float, mdct_window)[MDCT_SIZE];

where MDCT_SIZE is defined in the same file as:

#define MDCT_SIZE          512

While digging through AIX documentation on the IBM website, I am being lead to
believe that the AIX ABI may not be able to guarantee 32-byte alignment for
static allocations. It does sport an implementation of posix_memalign() so the
rest of our AltiVec/VMX code seems to do OK.

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