On 11/18/20 12:29 AM, [email protected] wrote:
> +static target_ulong do_grev(target_ulong rs1,
> + target_ulong rs2,
> + const target_ulong masks[])
> +{
I think the masks should be placed here, and not passed in.
What you should pass in is "int bits".
> + target_ulong x = rs1;
> + int shift = 1;
> + int i = 0;
> +
> + while (shift < TARGET_LONG_BITS) {
> + if (rs2 & shift) {
> + x = do_swap(x, masks[i], shift);
> + }
> + shift <<= 1;
> + ++i;
Cleaner as for loop:
for (i = 0, shift = 1; shift < bits; i++, shift <<= 1)
> + static const target_ulong masks[] = {
> +#ifdef TARGET_RISCV32
> + 0x55555555, 0x33333333, 0x0f0f0f0f,
> + 0x00ff00ff, 0x0000ffff,
> +#else
> + 0x5555555555555555, 0x3333333333333333,
> + 0x0f0f0f0f0f0f0f0f, 0x00ff00ff00ff00ff,
> + 0x0000ffff0000ffff, 0x00000000ffffffff,
> +#endif
You don't need to replicate every entry.
dup_const(0x55, MO_8),
dup_const(0x33, MO_8),
dup_const(0x0f, MO_8),
dup_const(0xff, MO_16),
dup_const(0xffff, MO_32),
#ifdef TARGET_RISCV64
UINT32_MAX
#endif
> +target_ulong HELPER(grevw)(target_ulong rs1, target_ulong rs2)
> +{
> + static const target_ulong masks[] = {
> + 0x55555555, 0x33333333, 0x0f0f0f0f,
> + 0x00ff00ff, 0x0000ffff,
> + };
> +
> + return do_grev(rs1, rs2, masks);
This one is broken because do_grev iterated to TARGET_LONG_BITS == 64, and the
masks array is too small.
Fixed by passing in 32 as bits parameter to do_grev, as above.
> +static bool trans_grevi(DisasContext *ctx, arg_grevi *a)
> +{
> + REQUIRE_EXT(ctx, RVB);
> +
> + if (a->shamt >= TARGET_LONG_BITS) {
> + return false;
> + }
> +
> + return gen_grevi(ctx, a);
> +}
While this is ok for an initial implementation, it is worth noticing the shamt
for rev8 as a special case for tcg_gen_bswap_tl.
Otherwise, this needs the same gen_shift treatment.
r~
