On Mon, 20 Jun 2022 at 19:23, Richard Henderson
<[email protected]> wrote:
>
> Signed-off-by: Richard Henderson <[email protected]>
> ---
> target/arm/helper-sme.h | 2 ++
> target/arm/translate-a64.h | 1 +
> target/arm/sme.decode | 4 ++++
> target/arm/sme_helper.c | 25 +++++++++++++++++++++++++
> target/arm/translate-a64.c | 14 ++++++++++++++
> target/arm/translate-sme.c | 13 +++++++++++++
> 6 files changed, 59 insertions(+)
>
> +void helper_sme_zero(CPUARMState *env, uint32_t imm, uint32_t svl)
> +{
> + uint32_t i;
> +
> + /*
> + * Special case clearing the entire ZA space.
> + * This falls into the CONSTRAINED UNPREDICTABLE zeroing of any
> + * parts of the ZA storage outside of SVL.
> + */
> + if (imm == 0xff) {
> + memset(env->zarray, 0, sizeof(env->zarray));
> + return;
> + }
> +
> + /*
> + * Recall that ZAnH.D[m] is spread across ZA[n+8*m].
> + * Unless SVL == ARM_MAX_VQ, each row is discontiguous.
This comment led me down a garden path for a while. Each
row in a tile *is* contiguous, whatever the value of SVL.
What isn't contiguous is the entire tile, because the rows
of the tile are striped across the ZA[] array so rows that
are adjacent in the tile aren't adjacent in the ZA[] array.
(And this is true even if SVL is ARM_MAX_VQ.)
> + */
> + for (i = 0; i < svl; i++) {
> + if (imm & (1 << (i % 8))) {
> + memset(&env->zarray[i], 0, svl);
> + }
> + }
> +}
With the comment fixed,
Reviewed-by: Peter Maydell <[email protected]>
I'll also go back to the patch that adds env->zarray to
suggest a beefed-up comment there, because I just had to
spend half an hour with the spec to make sure I understood
what the zarray is compared to the architecture (some of
which is the spec being complicated, of course ;-))
thanks
-- PMM
