Re: [PATCH v6 12/72] target/riscv: rvv-1.0: add fractional LMUL

[Alistair Francis]

On Tue, Jan 12, 2021 at 1:46 AM <frank.chang@sifive.com> wrote:
>
> From: Frank Chang <frank.chang@sifive.com>
>
> Introduce the concepts of fractional LMUL for RVV 1.0.
> In RVV 1.0, LMUL bits are contiguous in vtype register.
>
> Signed-off-by: Frank Chang <frank.chang@sifive.com>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/cpu.h           | 17 +++++++++--------
>  target/riscv/translate.c     | 16 ++++++++++++++--
>  target/riscv/vector_helper.c | 16 ++++++++++++++--
>  3 files changed, 37 insertions(+), 12 deletions(-)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index cd5c77114a4..3b985f6218d 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -105,10 +105,10 @@ typedef struct CPURISCVState CPURISCVState;
>
>  #define RV_VLEN_MAX 256
>
> -FIELD(VTYPE, VLMUL, 0, 2)
> -FIELD(VTYPE, VSEW, 2, 3)
> -FIELD(VTYPE, VEDIV, 5, 2)
> -FIELD(VTYPE, RESERVED, 7, sizeof(target_ulong) * 8 - 9)
> +FIELD(VTYPE, VLMUL, 0, 3)
> +FIELD(VTYPE, VSEW, 3, 3)
> +FIELD(VTYPE, VEDIV, 8, 2)
> +FIELD(VTYPE, RESERVED, 10, sizeof(target_ulong) * 8 - 11)
>  FIELD(VTYPE, VILL, sizeof(target_ulong) * 8 - 1, 1)
>
>  struct CPURISCVState {
> @@ -380,11 +380,12 @@ typedef RISCVCPU ArchCPU;
>  #include "exec/cpu-all.h"
>
>  FIELD(TB_FLAGS, VL_EQ_VLMAX, 2, 1)
> -FIELD(TB_FLAGS, LMUL, 3, 2)
> -FIELD(TB_FLAGS, SEW, 5, 3)
> -FIELD(TB_FLAGS, VILL, 8, 1)
> +FIELD(TB_FLAGS, LMUL, 3, 3)
> +FIELD(TB_FLAGS, SEW, 6, 3)
> +/* Skip MSTATUS_VS (0x600) fields */
> +FIELD(TB_FLAGS, VILL, 11, 1)
>  /* Is a Hypervisor instruction load/store allowed? */
> -FIELD(TB_FLAGS, HLSX, 9, 1)
> +FIELD(TB_FLAGS, HLSX, 12, 1)
>
>  bool riscv_cpu_is_32bit(CPURISCVState *env);
>
> diff --git a/target/riscv/translate.c b/target/riscv/translate.c
> index 18e198bf8a6..d9b3b37f698 100644
> --- a/target/riscv/translate.c
> +++ b/target/riscv/translate.c
> @@ -60,7 +60,19 @@ typedef struct DisasContext {
>      bool hlsx;
>      /* vector extension */
>      bool vill;
> -    uint8_t lmul;
> +    /*
> +     * Encode LMUL to lmul as follows:
> +     *     LMUL    vlmul    lmul
> +     *      1       000       0
> +     *      2       001       1
> +     *      4       010       2
> +     *      8       011       3
> +     *      -       100       -
> +     *     1/8      101      -3
> +     *     1/4      110      -2
> +     *     1/2      111      -1
> +     */
> +    int8_t lmul;
>      uint8_t sew;
>      uint16_t vlen;
>      bool vl_eq_vlmax;
> @@ -843,7 +855,7 @@ static void riscv_tr_init_disas_context(DisasContextBase 
> *dcbase, CPUState *cs)
>      ctx->hlsx = FIELD_EX32(tb_flags, TB_FLAGS, HLSX);
>      ctx->vill = FIELD_EX32(tb_flags, TB_FLAGS, VILL);
>      ctx->sew = FIELD_EX32(tb_flags, TB_FLAGS, SEW);
> -    ctx->lmul = FIELD_EX32(tb_flags, TB_FLAGS, LMUL);
> +    ctx->lmul = sextract32(FIELD_EX32(tb_flags, TB_FLAGS, LMUL), 0, 3);
>      ctx->vl_eq_vlmax = FIELD_EX32(tb_flags, TB_FLAGS, VL_EQ_VLMAX);
>  }
>
> diff --git a/target/riscv/vector_helper.c b/target/riscv/vector_helper.c
> index 12301e943e6..aa8348ea25a 100644
> --- a/target/riscv/vector_helper.c
> +++ b/target/riscv/vector_helper.c
> @@ -86,9 +86,21 @@ static inline uint32_t vext_vm(uint32_t desc)
>      return FIELD_EX32(simd_data(desc), VDATA, VM);
>  }
>
> -static inline uint32_t vext_lmul(uint32_t desc)
> +/*
> + * Encode LMUL to lmul as following:
> + *     LMUL    vlmul    lmul
> + *      1       000       0
> + *      2       001       1
> + *      4       010       2
> + *      8       011       3
> + *      -       100       -
> + *     1/8      101      -3
> + *     1/4      110      -2
> + *     1/2      111      -1
> + */
> +static inline int32_t vext_lmul(uint32_t desc)
>  {
> -    return FIELD_EX32(simd_data(desc), VDATA, LMUL);
> +    return sextract32(FIELD_EX32(simd_data(desc), VDATA, LMUL), 0, 3);
>  }
>
>  static uint32_t vext_wd(uint32_t desc)
> --
> 2.17.1
>
>