Re: [PATCH v6 07/14] target/riscv: Add instructions of the Zbc-extension

[Alistair Francis]

On Thu, Aug 26, 2021 at 3:08 AM Philipp Tomsich
<philipp.tomsich@vrull.eu> wrote:
>
> The following instructions are part of Zbc:
>  - clmul
>  - clmulh
>  - clmulr
>
> Note that these instructions were already defined in the pre-0.93 and
> the 0.93 draft-B proposals, but had not been omitted in the earlier
> addition of draft-B to QEmu.
>
> Signed-off-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

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

Alistair

> ---
>
> Changes in v6:
> - Move gen_clmulh to trans_rvb.c.inc, as per Richard H's request.
>
> Changes in v5:
> - Introduce gen_clmulh (as suggested by Richard H) and use to simplify
>   trans_clmulh().
>
> Changes in v3:
> - This adds the Zbc instructions as a spearate commit.
> - Uses a helper for clmul/clmulr instead of inlining the calculation of
>   the result (addressing a comment from Richard Henderson).
>
>  target/riscv/bitmanip_helper.c          | 27 +++++++++++++++++++++
>  target/riscv/helper.h                   |  2 ++
>  target/riscv/insn32.decode              |  5 ++++
>  target/riscv/insn_trans/trans_rvb.c.inc | 32 ++++++++++++++++++++++++-
>  4 files changed, 65 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/bitmanip_helper.c b/target/riscv/bitmanip_helper.c
> index 5b2f795d03..73be5a81c7 100644
> --- a/target/riscv/bitmanip_helper.c
> +++ b/target/riscv/bitmanip_helper.c
> @@ -3,6 +3,7 @@
>   *
>   * Copyright (c) 2020 Kito Cheng, kito.cheng@sifive.com
>   * Copyright (c) 2020 Frank Chang, frank.chang@sifive.com
> + * Copyright (c) 2021 Philipp Tomsich, philipp.tomsich@vrull.eu
>   *
>   * This program is free software; you can redistribute it and/or modify it
>   * under the terms and conditions of the GNU General Public License,
> @@ -88,3 +89,29 @@ target_ulong HELPER(gorcw)(target_ulong rs1, target_ulong 
> rs2)
>  {
>      return do_gorc(rs1, rs2, 32);
>  }
> +
> +target_ulong HELPER(clmul)(target_ulong rs1, target_ulong rs2)
> +{
> +    target_ulong result = 0;
> +
> +    for (int i = 0; i < TARGET_LONG_BITS; i++) {
> +        if ((rs2 >> i) & 1) {
> +            result ^= (rs1 << i);
> +        }
> +    }
> +
> +    return result;
> +}
> +
> +target_ulong HELPER(clmulr)(target_ulong rs1, target_ulong rs2)
> +{
> +    target_ulong result = 0;
> +
> +    for (int i = 0; i < TARGET_LONG_BITS; i++) {
> +        if ((rs2 >> i) & 1) {
> +            result ^= (rs1 >> (TARGET_LONG_BITS - i - 1));
> +        }
> +    }
> +
> +    return result;
> +}
> diff --git a/target/riscv/helper.h b/target/riscv/helper.h
> index 415e37bc37..c559c860a7 100644
> --- a/target/riscv/helper.h
> +++ b/target/riscv/helper.h
> @@ -63,6 +63,8 @@ DEF_HELPER_FLAGS_2(grev, TCG_CALL_NO_RWG_SE, tl, tl, tl)
>  DEF_HELPER_FLAGS_2(grevw, TCG_CALL_NO_RWG_SE, tl, tl, tl)
>  DEF_HELPER_FLAGS_2(gorc, TCG_CALL_NO_RWG_SE, tl, tl, tl)
>  DEF_HELPER_FLAGS_2(gorcw, TCG_CALL_NO_RWG_SE, tl, tl, tl)
> +DEF_HELPER_FLAGS_2(clmul, TCG_CALL_NO_RWG_SE, tl, tl, tl)
> +DEF_HELPER_FLAGS_2(clmulr, TCG_CALL_NO_RWG_SE, tl, tl, tl)
>
>  /* Special functions */
>  DEF_HELPER_3(csrrw, tl, env, tl, tl)
> diff --git a/target/riscv/insn32.decode b/target/riscv/insn32.decode
> index 1166e7f648..04711111c8 100644
> --- a/target/riscv/insn32.decode
> +++ b/target/riscv/insn32.decode
> @@ -713,6 +713,11 @@ roriw      0110000 .......... 101 ..... 0011011 @sh5
>  greviw     0110100 .......... 101 ..... 0011011 @sh5
>  gorciw     0010100 .......... 101 ..... 0011011 @sh5
>
> +# *** RV32 Zbc Standard Extension ***
> +clmul      0000101 .......... 001 ..... 0110011 @r
> +clmulh     0000101 .......... 011 ..... 0110011 @r
> +clmulr     0000101 .......... 010 ..... 0110011 @r
> +
>  # *** RV32 Zbs Standard Extension ***
>  bclr       0100100 .......... 001 ..... 0110011 @r
>  bclri      01001. ........... 001 ..... 0010011 @sh
> diff --git a/target/riscv/insn_trans/trans_rvb.c.inc 
> b/target/riscv/insn_trans/trans_rvb.c.inc
> index 21d713df27..6a3e0c6a09 100644
> --- a/target/riscv/insn_trans/trans_rvb.c.inc
> +++ b/target/riscv/insn_trans/trans_rvb.c.inc
> @@ -1,5 +1,5 @@
>  /*
> - * RISC-V translation routines for the RVB draft Zb[as] Standard Extension.
> + * RISC-V translation routines for the Zb[acs] Standard Extension.
>   *
>   * Copyright (c) 2020 Kito Cheng, kito.cheng@sifive.com
>   * Copyright (c) 2020 Frank Chang, frank.chang@sifive.com
> @@ -24,6 +24,12 @@
>      }                                            \
>  } while (0)
>
> +#define REQUIRE_ZBC(ctx) do {                    \
> +    if (!RISCV_CPU(ctx->cs)->cfg.ext_zbc) {      \
> +        return false;                            \
> +    }                                            \
> +} while (0)
> +
>  #define REQUIRE_ZBS(ctx) do {                    \
>      if (!RISCV_CPU(ctx->cs)->cfg.ext_zbs) {      \
>          return false;                            \
> @@ -357,3 +363,27 @@ static bool trans_slli_uw(DisasContext *ctx, arg_slli_uw 
> *a)
>      tcg_temp_free(source1);
>      return true;
>  }
> +
> +static bool trans_clmul(DisasContext *ctx, arg_clmul *a)
> +{
> +    REQUIRE_ZBC(ctx);
> +    return gen_arith(ctx, a, gen_helper_clmul);
> +}
> +
> +static void gen_clmulh(TCGv dst, TCGv src1, TCGv src2)
> +{
> +     gen_helper_clmulr(dst, src1, src2);
> +     tcg_gen_shri_tl(dst, dst, 1);
> +}
> +
> +static bool trans_clmulh(DisasContext *ctx, arg_clmulr *a)
> +{
> +    REQUIRE_ZBC(ctx);
> +    return gen_arith(ctx, a, gen_clmulh);
> +}
> +
> +static bool trans_clmulr(DisasContext *ctx, arg_clmulh *a)
> +{
> +    REQUIRE_ZBC(ctx);
> +    return gen_arith(ctx, a, gen_helper_clmulr);
> +}
> --
> 2.25.1
>
>