Re: [PATCH v5 48/60] target/riscv: vector mask-register logical instructions

[Richard Henderson <richard.henderson@linaro.org>]

Ho hum, failed to send to the list first time.


-------- Forwarded Message --------
Subject: Re: [PATCH v5 48/60] target/riscv: vector mask-register logical
instructions
Date: Sat, 14 Mar 2020 23:41:59 -0700
From: Richard Henderson <richard.henderson@linaro.org>
To: LIU Zhiwei <zhiwei_liu@c-sky.com>

[ Patch didn't make it to the list, so reviewing

https://github.com/romanheros/qemu/commit/8c782677c21909f80c481cfd7ab58c076761642c
]

This is ok as-is, so
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

But you can do better.

> 
> /* Vector Mask-Register Logical Instructions */
> #define GEN_MM_TRANS(NAME)                                         \
> static bool trans_##NAME(DisasContext *s, arg_r *a)                \
> {                                                                  \
>     if (vext_check_isa_ill(s, RVV)) {                              \
>         uint32_t data = 0;                                         \
>         gen_helper_gvec_4_ptr * fn = gen_helper_##NAME;            \
>         data = FIELD_DP32(data, VDATA, MLEN, s->mlen);             \
>         data = FIELD_DP32(data, VDATA, LMUL, s->lmul);             \
>         tcg_gen_gvec_4_ptr(vreg_ofs(s, a->rd), vreg_ofs(s, 0),     \
>             vreg_ofs(s, a->rs1), vreg_ofs(s, a->rs2),              \
>             cpu_env, 0, s->vlen / 8, data, fn);                    \
>         return true;                                               \
>     }                                                              \
>     return false;                                                  \
> }
> GEN_MM_TRANS(vmand_mm)
> GEN_MM_TRANS(vmnand_mm)
> GEN_MM_TRANS(vmandnot_mm)
> GEN_MM_TRANS(vmxor_mm)
> GEN_MM_TRANS(vmor_mm)
> GEN_MM_TRANS(vmnor_mm)
> GEN_MM_TRANS(vmornot_mm)
> GEN_MM_TRANS(vmxnor_mm)

For vl_eq_vlmax, we should use gvec.

For mlen == 1, nothing more is needed, as all bits are significant.  For mlen >
1, we can use

  tcg_gen_gvec_andi(MO_64, vreg_ofs(s, a->rd),
                    vreg_ofs(s, a->rd),
                    pred_mlen_masks[log2_mlen],
                    s->vlen / 8, s->vlen / 8);

where pred_mlen_masks[] are as discussed vs 49/60 (vmpopc).

It might be worth noticing vmclr.mm, which of course does not require that andi.

> /* Vector Mask-Register Logical Instructions */
> #define GEN_VEXT_MASK_VV(NAME, OP)                        \
> void HELPER(NAME)(void *vd, void *v0, void *vs1,          \
>         void *vs2, CPURISCVState *env, uint32_t desc)     \
> {                                                         \
>     uint32_t mlen = vext_mlen(desc);                      \
>     uint32_t vlmax = env_archcpu(env)->cfg.vlen / mlen;   \
>     uint32_t vl = env->vl;                                \
>     uint32_t i;                                           \
>     int a, b;                                             \
>     for (i = 0; i < vl; i++) {                            \
>         a = vext_elem_mask(vs1, mlen, i);                 \
>         b = vext_elem_mask(vs2, mlen, i);                 \
>         vext_set_elem_mask(vd, mlen, i, OP(b, a));        \
>     }                                                     \
>     if (i == 0) {                                         \
>         return;                                           \
>     }                                                     \
>     for (; i < vlmax; i++) {                              \
>         vext_set_elem_mask(vd, mlen, i, 0);               \
>     }                                                     \
> }
> #define DO_NAND(N, M)  (!(N & M))
> #define DO_ANDNOT(N, M)  (N & !M)
> #define DO_NOR(N, M)  (!(N | M))
> #define DO_ORNOT(N, M)  (N | !M)
> #define DO_XNOR(N, M)  (!(N ^ M))

Again, these operations can be done in units of uint64_t, applying the
pred_msize_mask and the residual "rmask" that I mentoned wrt vmpopc.

This would mean that you'd want bitwise, not logical nots above in your DO_*
macros.


r~