Re: [Qemu-devel] [PATCH 04/13] target-ppc: implement lxvll instruction

[Richard Henderson]

On 12/05/2016 03:25 AM, Nikunj A Dadhania wrote:
> +void helper_lxvll(CPUPPCState *env, target_ulong addr,
> +                  target_ulong xt_num, target_ulong rb)
> +{
> +    ppc_vsr_t xt;
> +
> +    getVSR(xt_num, &xt, env);
> +    if (unlikely((rb & 0xFF) == 0)) {
> +        xt.s128 = int128_make128(0, 0);

Nit: int128_zero.

> +    } else {
> +        target_ulong end = ((rb & 0xFF) * 8) - 1;
> +        if (msr_le) {
> +            xt.u64[LO_IDX] = cpu_ldq_data_ra(env, addr, GETPC());
> +            addr = addr_add(env, addr, 8);
> +            xt.u64[HI_IDX] = cpu_ldq_data_ra(env, addr, GETPC());
> +            xt.s128 = int128_and(xt.s128, mask_u128(127 - end, 127));

The ISA document says that this is a sequence of byte operations.  Which means
that END < 127 will not access bytes outside of the length.  Which means that
your code will trigger SIGSEGV near page boundaries when real hardware won't.

I also don't see how this does the right thing for little-endian.


r~