On Sat, 15 Aug 2020 at 02:32, Richard Henderson
<richard.hender...@linaro.org> wrote:
>
> Missed out on compressing the second half of a predicate
> with length vl % 512 > 256.
>
> Adjust all of the x + (y << s) to x | (y << s) as a
> general style fix.
>
> Reported-by: Laurent Desnogues <laurent.desnog...@gmail.com>
> Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
> ---
> target/arm/sve_helper.c | 30 +++++++++++++++++++++---------
> 1 file changed, 21 insertions(+), 9 deletions(-)
>
> diff --git a/target/arm/sve_helper.c b/target/arm/sve_helper.c
> index 4758d46f34..fcb46f150f 100644
> --- a/target/arm/sve_helper.c
> +++ b/target/arm/sve_helper.c
> @@ -1938,7 +1938,7 @@ void HELPER(sve_uzp_p)(void *vd, void *vn, void *vm,
> uint32_t pred_desc)
> if (oprsz <= 8) {
> l = compress_bits(n[0] >> odd, esz);
> h = compress_bits(m[0] >> odd, esz);
> - d[0] = extract64(l + (h << (4 * oprsz)), 0, 8 * oprsz);
> + d[0] = l | (h << (4 * oprsz));
Why did we drop the extract64() here ? This doesn't seem
to correspond to either of the things the commit message
says we're doing.
Also, if oprsz is < 8, don't we need to mask out the high
bits in l that would otherwise overlap with h << (4 * oprsz) ?
Are they guaranteed zeroes somehow?
> } else {
> ARMPredicateReg tmp_m;
> intptr_t oprsz_16 = oprsz / 16;
> @@ -1952,23 +1952,35 @@ void HELPER(sve_uzp_p)(void *vd, void *vn, void *vm,
> uint32_t pred_desc)
> h = n[2 * i + 1];
> l = compress_bits(l >> odd, esz);
> h = compress_bits(h >> odd, esz);
> - d[i] = l + (h << 32);
> + d[i] = l | (h << 32);
> }
>
> - /* For VL which is not a power of 2, the results from M do not
> - align nicely with the uint64_t for D. Put the aligned results
> - from M into TMP_M and then copy it into place afterward. */
> + /*
> + * For VL which is not a multiple of 512, the results from M do not
> + * align nicely with the uint64_t for D. Put the aligned results
> + * from M into TMP_M and then copy it into place afterward.
> + */
> if (oprsz & 15) {
> - d[i] = compress_bits(n[2 * i] >> odd, esz);
> + int final_shift = (oprsz & 15) * 2;
> +
> + l = n[2 * i + 0];
> + h = n[2 * i + 1];
> + l = compress_bits(l >> odd, esz);
> + h = compress_bits(h >> odd, esz);
> + d[i] = l | (h << final_shift);
Similarly here, why don't we need to mask out the top parts of l and h ?
>
> for (i = 0; i < oprsz_16; i++) {
> l = m[2 * i + 0];
> h = m[2 * i + 1];
> l = compress_bits(l >> odd, esz);
> h = compress_bits(h >> odd, esz);
> - tmp_m.p[i] = l + (h << 32);
> + tmp_m.p[i] = l | (h << 32);
> }
> - tmp_m.p[i] = compress_bits(m[2 * i] >> odd, esz);
> + l = m[2 * i + 0];
> + h = m[2 * i + 1];
> + l = compress_bits(l >> odd, esz);
> + h = compress_bits(h >> odd, esz);
> + tmp_m.p[i] = l | (h << final_shift);
>
> swap_memmove(vd + oprsz / 2, &tmp_m, oprsz / 2);
Aren't there cases where the 'n' part of the result doesn't
end up a whole number of bytes and we have to do a shift as
well as a byte copy?
> } else {
> @@ -1977,7 +1989,7 @@ void HELPER(sve_uzp_p)(void *vd, void *vn, void *vm,
> uint32_t pred_desc)
> h = m[2 * i + 1];
> l = compress_bits(l >> odd, esz);
> h = compress_bits(h >> odd, esz);
> - d[oprsz_16 + i] = l + (h << 32);
> + d[oprsz_16 + i] = l | (h << 32);
> }
> }
> }
thanks
-- PMM
