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Re: [Qemu-ppc] [PATCH 5/5] ppc: Improve generation of conditional traps


From: David Gibson
Subject: Re: [Qemu-ppc] [PATCH 5/5] ppc: Improve generation of conditional traps
Date: Tue, 9 Aug 2016 12:07:40 +1000
User-agent: Mutt/1.6.2 (2016-07-01)

On Sun, Jul 31, 2016 at 03:13:13PM +1000, Benjamin Herrenschmidt wrote:
> Translate most conditions to TCG conditions and avoid the helper
> for most of the common cases.
> 
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
> ---
>  target-ppc/translate.c | 168 
> ++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 132 insertions(+), 36 deletions(-)

I've merged 1-4 of this series into ppc-for-2.8.  I'm not really clear
whether a change is still needed on patch 5, so please resend either
way.

> 
> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> index 47eb9ed..561976f 100644
> --- a/target-ppc/translate.c
> +++ b/target-ppc/translate.c
> @@ -3639,82 +3639,178 @@ static void gen_sc(DisasContext *ctx)
>  
>  /***                                Trap                                   
> ***/
>  
> -/* Check for unconditional traps (always or never) */
> -static bool check_unconditional_trap(DisasContext *ctx)
> +static int TO2tcg[32] = {
> +        TCG_COND_NEVER, /* no condition */
> +        TCG_COND_GTU,   /* 0x01 u> */
> +        TCG_COND_LTU,   /* 0x02 u< */
> +        TCG_COND_NE,    /* 0x03 u< or u> -> NE */
> +        TCG_COND_EQ,    /* 0x04 = */
> +        TCG_COND_GEU,   /* 0x05 u> or = */
> +        TCG_COND_LEU,   /* 0x06 u< or = */
> +        TCG_COND_ALWAYS,/* 0x07 u< or u> or = -> ALWAYS */
> +        TCG_COND_GT,    /* 0x08 > */
> +        -1,             /* 0x09 > or u> -> weird */
> +        -1,             /* 0x0a > or u< -> weird */
> +        -1,             /* 0x0b > or u< or u> -> weird */
> +        TCG_COND_GE,    /* 0x0c > or = */
> +        -1,             /* 0x0d > or = or u> */
> +        -1,             /* 0x0e > or = or u< */
> +        -1,             /* 0x0f > or = or u> or u< */
> +        TCG_COND_LT,    /* 0x10 < */
> +        -1,             /* 0x11 < or u> -> weird */
> +        -1,             /* 0x12 < or u< -> weird */
> +        -1,             /* 0x13 < or u< or u> -> weird */
> +        TCG_COND_LE,    /* 0x14 < or = */
> +        -1,             /* 0x15 < or = or u> -> weird */
> +        -1,             /* 0x16 < or = or u< -> weird */
> +        TCG_COND_ALWAYS,/* 0x17 < or = or u< or u> -> ALWAYS */
> +        TCG_COND_NE,    /* 0x18 < or > -> NE */
> +        -1,             /* 0x19 < or > or u> -> weird */
> +        -1,             /* 0x1a < or > or u< -> weird */
> +        -1,             /* 0x1b < or > or u> or u< -> weird */
> +        TCG_COND_ALWAYS,/* 0x1c < or > or = -> ALWAYS */
> +        TCG_COND_ALWAYS,/* 0x1d < or > or = or u> -> ALWAYS */
> +        TCG_COND_ALWAYS,/* 0x1e < or > or = or u< -> ALWAYS */
> +        TCG_COND_ALWAYS,/* 0x1f < or > or = or u< -> ALWAYS */
> +};
> +
> +#define TRAP_UNCOND     (-1)
> +#define TRAP_HELPER     (-2)
> +
> +static int precheck_trap(DisasContext *ctx)
>  {
> -    /* Trap never */
> -    if (TO(ctx->opcode) == 0) {
> -        return true;
> +    int cond = TO2tcg[TO(ctx->opcode)];
> +
> +    /* Weird traps go to helper */
> +    if (cond < 0) {
> +        return TRAP_HELPER;
>      }
> -    /* Trap always */
> -    if (TO(ctx->opcode) == 31) {
> +    /* Unconditionals */
> +    if (cond == TCG_COND_ALWAYS) {
>          gen_exception_err(ctx, POWERPC_EXCP_PROGRAM, POWERPC_EXCP_TRAP);
> -        return true;
> +        return TRAP_UNCOND;
>      }
> -    return false;
> +    if (cond == TCG_COND_NEVER) {
> +        return TRAP_UNCOND;
> +    }
> +    /* Invert the condition as we branch over the exception when the
> +     * condition is *not* met
> +     */
> +    return tcg_invert_cond(cond);
> +}
> +
> +static void gen_trap(DisasContext *ctx)
> +{
> +    TCGv_i32 t0, t1;
> +
> +    t0 = tcg_const_i32(POWERPC_EXCP_PROGRAM);
> +    t1 = tcg_const_i32(POWERPC_EXCP_TRAP);
> +    gen_update_nip(ctx, ctx->nip - 4);
> +    gen_helper_raise_exception_err(cpu_env, t0, t1);
> +    tcg_temp_free_i32(t0);
> +    tcg_temp_free_i32(t1);
>  }
>  
>  /* tw */
>  static void gen_tw(DisasContext *ctx)
>  {
> -    TCGv_i32 t0;
> +    int cond = precheck_trap(ctx);
> +    TCGLabel *l1;
> +    TCGv t0;
> +    TCGv t1;
>  
> -    if (check_unconditional_trap(ctx)) {
> +    if (cond == TRAP_UNCOND) {
> +        return;
> +    } else if (cond == TRAP_HELPER) {
> +        TCGv_i32 trapop = tcg_const_i32(TO(ctx->opcode));
> +        gen_helper_tw(cpu_env, cpu_gpr[rA(ctx->opcode)],
> +                      cpu_gpr[rB(ctx->opcode)], trapop);
> +        tcg_temp_free_i32(trapop);
>          return;
>      }
> -    t0 = tcg_const_i32(TO(ctx->opcode));
> -    gen_helper_tw(cpu_env, cpu_gpr[rA(ctx->opcode)], 
> cpu_gpr[rB(ctx->opcode)],
> -                  t0);
> -    tcg_temp_free_i32(t0);
> +    l1 = gen_new_label();
> +    t0 = tcg_temp_new();
> +    t1 = tcg_temp_new();
> +    tcg_gen_ext32s_tl(t0, cpu_gpr[rA(ctx->opcode)]);
> +    tcg_gen_ext32s_tl(t1, cpu_gpr[rB(ctx->opcode)]);
> +    tcg_gen_brcond_tl(cond, t0, t1, l1);
> +    gen_trap(ctx);
> +    gen_set_label(l1);
> +    tcg_temp_free(t0);
> +    tcg_temp_free(t1);
>  }
>  
>  /* twi */
>  static void gen_twi(DisasContext *ctx)
>  {
> +    int cond = precheck_trap(ctx);
> +    TCGLabel *l1;
>      TCGv t0;
> -    TCGv_i32 t1;
>  
> -    if (check_unconditional_trap(ctx)) {
> +    if (cond == TRAP_UNCOND) {
> +        return;
> +    } else if (cond == TRAP_HELPER) {
> +        TCGv_i32 trapop = tcg_const_i32(TO(ctx->opcode));
> +        t0 = tcg_const_tl(SIMM(ctx->opcode));
> +        gen_helper_tw(cpu_env, cpu_gpr[rA(ctx->opcode)], t0, trapop);
> +        tcg_temp_free_i32(trapop);
> +        tcg_temp_free(t0);
>          return;
>      }
> -    t0 = tcg_const_tl(SIMM(ctx->opcode));
> -    t1 = tcg_const_i32(TO(ctx->opcode));
> -    gen_helper_tw(cpu_env, cpu_gpr[rA(ctx->opcode)], t0, t1);
> +    l1 = gen_new_label();
> +    t0 = tcg_temp_new();
> +    tcg_gen_ext32s_tl(t0, cpu_gpr[rA(ctx->opcode)]);
> +    tcg_gen_brcondi_tl(cond, t0, SIMM(ctx->opcode), l1);
> +    gen_trap(ctx);
> +    gen_set_label(l1);
>      tcg_temp_free(t0);
> -    tcg_temp_free_i32(t1);
>  }
>  
>  #if defined(TARGET_PPC64)
>  /* td */
>  static void gen_td(DisasContext *ctx)
>  {
> -    TCGv_i32 t0;
> +    int cond = precheck_trap(ctx);
> +    TCGLabel *l1;
>  
> -    if (check_unconditional_trap(ctx)) {
> +    if (cond == TRAP_UNCOND) {
> +        return;
> +    } else if (cond == TRAP_HELPER) {
> +        TCGv_i32 trapop = tcg_const_i32(TO(ctx->opcode));
> +        gen_helper_td(cpu_env, cpu_gpr[rA(ctx->opcode)],
> +                      cpu_gpr[rB(ctx->opcode)], trapop);
> +        tcg_temp_free_i32(trapop);
>          return;
>      }
> -    t0 = tcg_const_i32(TO(ctx->opcode));
> -    gen_helper_td(cpu_env, cpu_gpr[rA(ctx->opcode)], 
> cpu_gpr[rB(ctx->opcode)],
> -                  t0);
> -    tcg_temp_free_i32(t0);
> +    l1 = gen_new_label();
> +    tcg_gen_brcond_tl(cond, cpu_gpr[rA(ctx->opcode)],
> +                      cpu_gpr[rB(ctx->opcode)], l1);
> +    gen_trap(ctx);
> +    gen_set_label(l1);
>  }
>  
>  /* tdi */
>  static void gen_tdi(DisasContext *ctx)
>  {
> -    TCGv t0;
> -    TCGv_i32 t1;
> +    int cond = precheck_trap(ctx);
> +    TCGLabel *l1;
>  
> -    if (check_unconditional_trap(ctx)) {
> +    if (cond == TRAP_UNCOND) {
> +        return;
> +    } else if (cond == TRAP_HELPER) {
> +        TCGv_i32 trapop = tcg_const_i32(TO(ctx->opcode));
> +        TCGv t0 = tcg_const_tl(SIMM(ctx->opcode));
> +        gen_helper_td(cpu_env, cpu_gpr[rA(ctx->opcode)], t0, trapop);
> +        tcg_temp_free_i32(trapop);
> +        tcg_temp_free(t0);
>          return;
>      }
> -    t0 = tcg_const_tl(SIMM(ctx->opcode));
> -    t1 = tcg_const_i32(TO(ctx->opcode));
> -    gen_helper_td(cpu_env, cpu_gpr[rA(ctx->opcode)], t0, t1);
> -    tcg_temp_free(t0);
> -    tcg_temp_free_i32(t1);
> +    l1 = gen_new_label();
> +    tcg_gen_brcondi_tl(cond, cpu_gpr[rA(ctx->opcode)], SIMM(ctx->opcode), 
> l1);
> +    gen_trap(ctx);
> +    gen_set_label(l1);
>  }
> -#endif
> +#endif /* defined(TARGET_PPC64) */
>  
>  /***                          Processor control                            
> ***/
>  

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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