Re: [PATCH v3 2/4] target/riscv: Reuse tb->flags.FS

[Weiwei Li]

On 2023/4/29 00:52, Mayuresh Chitale wrote:
> When misa.F is 0 tb->flags.FS field is unused and can be used to save
> the current state of smstateen0.FCSR check which is needed by the
> floating point translation routines.
>
> Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
> ---

Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>

Weiwei Li

>   target/riscv/cpu_helper.c |  9 +++++++++
>   target/riscv/translate.c  | 12 +++++++++++-
>   2 files changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> index b68dcfe7b6..126ac221a0 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -119,6 +119,15 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong 
> *pc,
>           vs = MIN(vs, get_field(env->mstatus_hs, MSTATUS_VS));
>       }
>   
> +    /*
> +     * If misa.F is 0 then the FS field of the tb->flags can be used to pass
> +     * the current state of the smstateen.FCSR bit which must be checked for
> +     * in the floating point translation routines.
> +     */
> +    if (!riscv_has_ext(env, RVF)) {
> +        fs = (smstateen_acc_ok(env, 0, SMSTATEEN0_FCSR) == RISCV_EXCP_NONE);
> +    }
> +
>       if (cpu->cfg.debug && !icount_enabled()) {
>           flags = FIELD_DP32(flags, TB_FLAGS, ITRIGGER, env->itrigger_enabled);
>       }
> diff --git a/target/riscv/translate.c b/target/riscv/translate.c
> index 928da0d3f0..74f624aa62 100644
> --- a/target/riscv/translate.c
> +++ b/target/riscv/translate.c
> @@ -78,6 +78,7 @@ typedef struct DisasContext {
>       int frm;
>       RISCVMXL ol;
>       bool virt_inst_excp;
> +    bool smstateen_fcsr_ok;
>       bool virt_enabled;
>       const RISCVCPUConfig *cfg_ptr;
>       /* vector extension */
> @@ -1155,7 +1156,11 @@ static void riscv_tr_init_disas_context(DisasContextBase 
> *dcbase, CPUState *cs)
>       ctx->pc_succ_insn = ctx->base.pc_first;
>       ctx->priv = FIELD_EX32(tb_flags, TB_FLAGS, PRIV);
>       ctx->mem_idx = FIELD_EX32(tb_flags, TB_FLAGS, MEM_IDX);
> -    ctx->mstatus_fs = FIELD_EX32(tb_flags, TB_FLAGS, FS);
> +    if (has_ext(ctx, RVF)) {
> +        ctx->mstatus_fs = FIELD_EX32(tb_flags, TB_FLAGS, FS);
> +    } else {
> +        ctx->mstatus_fs = 0;
> +    }
>       ctx->mstatus_vs = FIELD_EX32(tb_flags, TB_FLAGS, VS);
>       ctx->priv_ver = env->priv_ver;
>       ctx->virt_enabled = FIELD_EX32(tb_flags, TB_FLAGS, VIRT_ENABLED);
> @@ -1178,6 +1183,11 @@ static void riscv_tr_init_disas_context(DisasContextBase 
> *dcbase, CPUState *cs)
>       ctx->itrigger = FIELD_EX32(tb_flags, TB_FLAGS, ITRIGGER);
>       ctx->zero = tcg_constant_tl(0);
>       ctx->virt_inst_excp = false;
> +    if (has_ext(ctx, RVF) || !cpu->cfg.ext_smstateen) {
> +        ctx->smstateen_fcsr_ok = 1;
> +    } else {
> +        ctx->smstateen_fcsr_ok = FIELD_EX32(tb_flags, TB_FLAGS, FS);
> +    }
>   }
>   
>   static void riscv_tr_tb_start(DisasContextBase *db, CPUState *cpu)