On Mon, Oct 21, 2013 at 8:49 AM, Bill Schmidt
<wschm...@linux.vnet.ibm.com> wrote:
> Hi,
>
> In altivec_expand_vec_perm_const, we look for special masks that match
> the behavior of specific instructions, so we can use those instructions
> rather than load a constant control vector and perform a permute. Some
> of the masks must be treated differently for little endian mode.
>
> The masks that represent merge-high and merge-low operations have
> reversed meanings in little-endian, because of the reversed ordering of
> the vector elements.
>
> The masks that represent vector-pack operations remain correct when the
> mode of the input operands matches the natural mode of the instruction,
> but not otherwise. This is because the pack instructions always select
> the rightmost, low-order bits of the vector element. There are cases
> where we use this, for example, with a V8SI vector matching a vpkuwum
> mask in order to select the odd-numbered elements of the vector. In
> little endian mode, this instruction will get us the even-numbered
> elements instead. There is no alternative instruction with the desired
> behavior, so I've just disabled use of those masks for little endian
> when the mode isn't natural.
>
> These changes fix 32 failures in the test suite for little endian mode.
> Bootstrapped and tested on powerpc64{,le}-unknown-linux-gnu with no new
> failures. Is this ok for trunk?
>
> Thanks,
> Bill
>
>
> 2013-10-21 Bill Schmidt <wschm...@vnet.ibm.com>
>
> * config/rs6000/rs6000.c (altivec_expand_vec_perm_const): Reverse
> meaning of merge-high and merge-low masks for little endian; avoid
> use of vector-pack masks for little endian for mismatched modes.
Okay.
Thanks, David
