Re: [PATCH v2 03/15] RISC-V: Adding XTheadBa ISA extension

[Alistair Francis <alistair23@gmail.com>]

On Sat, Dec 24, 2022 at 4:10 AM Christoph Muellner
<christoph.muellner@vrull.eu> wrote:
>
> From: Christoph Müllner <christoph.muellner@vrull.eu>
>
> This patch adds support for the XTheadBa ISA extension.
> The patch uses the T-Head specific decoder and translation.
>
> Changes in v2:
> - Add ISA_EXT_DATA_ENTRY()
> - Split XtheadB* extension into individual commits
> - Use single decoder for XThead extensions
>
> Co-developed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
> Co-developed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
> Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>

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

Alistair

> ---
>  target/riscv/cpu.c                         |  2 ++
>  target/riscv/cpu.h                         |  1 +
>  target/riscv/insn_trans/trans_xthead.c.inc | 39 ++++++++++++++++++++++
>  target/riscv/translate.c                   |  3 +-
>  target/riscv/xthead.decode                 | 22 ++++++++++++
>  5 files changed, 66 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index a848836d2e..809b6eb4ed 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -108,6 +108,7 @@ static const struct isa_ext_data isa_edata_arr[] = {
>      ISA_EXT_DATA_ENTRY(svinval, true, PRIV_VERSION_1_12_0, ext_svinval),
>      ISA_EXT_DATA_ENTRY(svnapot, true, PRIV_VERSION_1_12_0, ext_svnapot),
>      ISA_EXT_DATA_ENTRY(svpbmt, true, PRIV_VERSION_1_12_0, ext_svpbmt),
> +    ISA_EXT_DATA_ENTRY(xtheadba, true, PRIV_VERSION_1_11_0, ext_xtheadba),
>      ISA_EXT_DATA_ENTRY(xtheadcmo, true, PRIV_VERSION_1_11_0, ext_xtheadcmo),
>      ISA_EXT_DATA_ENTRY(xtheadsync, true, PRIV_VERSION_1_11_0, ext_xtheadsync),
>      ISA_EXT_DATA_ENTRY(xventanacondops, true, PRIV_VERSION_1_12_0, ext_XVentanaCondOps),
> @@ -1062,6 +1063,7 @@ static Property riscv_cpu_extensions[] = {
>      DEFINE_PROP_BOOL("zmmul", RISCVCPU, cfg.ext_zmmul, false),
>
>      /* Vendor-specific custom extensions */
> +    DEFINE_PROP_BOOL("xtheadba", RISCVCPU, cfg.ext_xtheadba, false),
>      DEFINE_PROP_BOOL("xtheadcmo", RISCVCPU, cfg.ext_xtheadcmo, false),
>      DEFINE_PROP_BOOL("xtheadsync", RISCVCPU, cfg.ext_xtheadsync, false),
>      DEFINE_PROP_BOOL("xventanacondops", RISCVCPU, cfg.ext_XVentanaCondOps, false),
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 4d3da2acfa..ec2588a0f0 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -465,6 +465,7 @@ struct RISCVCPUConfig {
>      uint64_t mimpid;
>
>      /* Vendor-specific custom extensions */
> +    bool ext_xtheadba;
>      bool ext_xtheadcmo;
>      bool ext_xtheadsync;
>      bool ext_XVentanaCondOps;
> diff --git a/target/riscv/insn_trans/trans_xthead.c.inc b/target/riscv/insn_trans/trans_xthead.c.inc
> index 6009d61c81..79e1f5bde9 100644
> --- a/target/riscv/insn_trans/trans_xthead.c.inc
> +++ b/target/riscv/insn_trans/trans_xthead.c.inc
> @@ -16,6 +16,12 @@
>   * this program.  If not, see <http://www.gnu.org/licenses/>.
>   */
>
> +#define REQUIRE_XTHEADBA(ctx) do {               \
> +    if (!ctx->cfg_ptr->ext_xtheadba) {           \
> +        return false;                            \
> +    }                                            \
> +} while (0)
> +
>  #define REQUIRE_XTHEADCMO(ctx) do {              \
>      if (!ctx->cfg_ptr->ext_xtheadcmo) {          \
>          return false;                            \
> @@ -28,6 +34,39 @@
>      }                                            \
>  } while (0)
>
> +/* XTheadBa */
> +
> +/*
> + * th.addsl is similar to sh[123]add (from Zba), but not an
> + * alternative encoding: while sh[123] applies the shift to rs1,
> + * th.addsl shifts rs2.
> + */
> +
> +#define GEN_TH_ADDSL(SHAMT)                                     \
> +static void gen_th_addsl##SHAMT(TCGv ret, TCGv arg1, TCGv arg2) \
> +{                                                               \
> +    TCGv t = tcg_temp_new();                                    \
> +    tcg_gen_shli_tl(t, arg2, SHAMT);                            \
> +    tcg_gen_add_tl(ret, t, arg1);                               \
> +    tcg_temp_free(t);                                           \
> +}
> +
> +GEN_TH_ADDSL(1)
> +GEN_TH_ADDSL(2)
> +GEN_TH_ADDSL(3)
> +
> +#define GEN_TRANS_TH_ADDSL(SHAMT)                                       \
> +static bool trans_th_addsl##SHAMT(DisasContext *ctx,                    \
> +                                  arg_th_addsl##SHAMT * a)              \
> +{                                                                       \
> +    REQUIRE_XTHEADBA(ctx);                                              \
> +    return gen_arith(ctx, a, EXT_NONE, gen_th_addsl##SHAMT, NULL);      \
> +}
> +
> +GEN_TRANS_TH_ADDSL(1)
> +GEN_TRANS_TH_ADDSL(2)
> +GEN_TRANS_TH_ADDSL(3)
> +
>  /* XTheadCmo */
>
>  static inline int priv_level(DisasContext *ctx)
> diff --git a/target/riscv/translate.c b/target/riscv/translate.c
> index c40617662a..7b35f1d71b 100644
> --- a/target/riscv/translate.c
> +++ b/target/riscv/translate.c
> @@ -127,7 +127,8 @@ static bool always_true_p(DisasContext *ctx  __attribute__((__unused__)))
>
>  static bool has_xthead_p(DisasContext *ctx  __attribute__((__unused__)))
>  {
> -    return ctx->cfg_ptr->ext_xtheadcmo || ctx->cfg_ptr->ext_xtheadsync;
> +    return ctx->cfg_ptr->ext_xtheadba || ctx->cfg_ptr->ext_xtheadcmo ||
> +           ctx->cfg_ptr->ext_xtheadsync;
>  }
>
>  #define MATERIALISE_EXT_PREDICATE(ext)  \
> diff --git a/target/riscv/xthead.decode b/target/riscv/xthead.decode
> index 1d86f3a012..b149f13018 100644
> --- a/target/riscv/xthead.decode
> +++ b/target/riscv/xthead.decode
> @@ -2,6 +2,7 @@
>  # Translation routines for the instructions of the XThead* ISA extensions
>  #
>  # Copyright (c) 2022 Christoph Muellner, christoph.muellner@vrull.eu
> +#                    Dr. Philipp Tomsich, philipp.tomsich@vrull.eu
>  #
>  # SPDX-License-Identifier: LGPL-2.1-or-later
>  #
> @@ -9,12 +10,33 @@
>  #   https://github.com/T-head-Semi/thead-extension-spec/releases/latest
>
>  # Fields:
> +%rd        7:5
>  %rs1       15:5
>  %rs2       20:5
>
> +# Argument sets
> +&r         rd rs1 rs2                               !extern
> +
>  # Formats
>  @sfence_vm  ....... ..... .....   ... ..... ....... %rs1
>  @rs2_s      ....... ..... ..... ... ..... .......   %rs2 %rs1
> +@r          ....... ..... .....  ... ..... .......  &r %rs2 %rs1 %rd
> +
> +# XTheadBa
> +# Instead of defining a new encoding, we simply use the decoder to
> +# extract the imm[0:1] field and dispatch to separate translation
> +# functions (mirroring the `sh[123]add` instructions from Zba and
> +# the regular RVI `add` instruction.
> +#
> +# The only difference between sh[123]add and addsl is that the shift
> +# is applied to rs1 (for addsl) instead of rs2 (for sh[123]add).
> +#
> +# Note that shift-by-0 is a valid operation according to the manual.
> +# This will be equivalent to a regular add.
> +add              0000000 ..... ..... 001 ..... 0001011 @r
> +th_addsl1        0000001 ..... ..... 001 ..... 0001011 @r
> +th_addsl2        0000010 ..... ..... 001 ..... 0001011 @r
> +th_addsl3        0000011 ..... ..... 001 ..... 0001011 @r
>
>  # XTheadCmo
>  th_dcache_call   0000000 00001 00000 000 00000 0001011
> --
> 2.38.1
>
>