On Sun, 2016-11-20 at 10:28 +0100, Peter Meerwald-Stadler wrote: > > > Do you happen to remember why the audio buffers in run_mix_test() in > > > src/tests/cpu-mix-test.c are forced to have 8-byte alignment? I plan to > > > replace the stack-allocated buffers with regular memblocks, and the > > > memblock backing memory is only aligned to 4 bytes on 32-bit machines. > > > It's possible to still have the old alignment behaviour, but that > > > requires extra code, and if 4-byte alignment is equally fine, then I'd > > > prefer to avoid the extra code. > > > > Also, why is the alignment so carefully controlled? All tests are run > > on a buffer that begins one sample after the 8-byte alignment boundary. > > Is this done to catch bugs related to weird (but valid) sample > > alignments? > > probably this also constitutes a worst-case runtime-wise; I can't remember > really Ok, let's assume that the purpose of the one-sample offset is to test the worst case. That won't work reliably if the initial alignment is random, so that would explain why the buffer is aligned to a 8-byte boundary. Do you think that it makes any difference on 32-bit machines whether the buffer is aligned to 4 or 8 bytes? I would expect there to be no difference. If there's no difference, then the alignment guarantee that a pool-allocated memblock gives is sufficient. > it would be nice to have explicit alignment requirements/guarantees on > buffers that are potentially processed by SIMDy code; alignment might make > the code run faster I think pretty much all audio buffers are aligned to the pointer size. Do you think there would be room for improvement? -- Tanu https://www.patreon.com/tanuk
