Re: [PATCH 4/4] target/ppc: Rework store conditional to avoid branch

[Richard Henderson <richard.henderson@linaro.org>]

On 6/4/23 03:28, Nicholas Piggin wrote:
> Rework store conditional to avoid a branch in the success case.
> Change some of the variable names and layout while here so
> gen_conditional_store more closely matches gen_stqcx_.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>   target/ppc/translate.c | 65 ++++++++++++++++++++----------------------
>   1 file changed, 31 insertions(+), 34 deletions(-)
> 
> diff --git a/target/ppc/translate.c b/target/ppc/translate.c
> index 77e1c5abb6..cf99e961f7 100644
> --- a/target/ppc/translate.c
> +++ b/target/ppc/translate.c
> @@ -3812,31 +3812,32 @@ static void gen_stdat(DisasContext *ctx)
>   
>   static void gen_conditional_store(DisasContext *ctx, MemOp memop)
>   {
> -    TCGLabel *l1 = gen_new_label();
> -    TCGLabel *l2 = gen_new_label();
> -    TCGv t0 = tcg_temp_new();
> -    int reg = rS(ctx->opcode);
> +    TCGLabel *lfail;
> +    TCGv EA;
> +    TCGv cr0;
> +    TCGv t0;
> +    int rs = rS(ctx->opcode);
>   
> +    lfail = gen_new_label();
> +    EA = tcg_temp_new();
> +    cr0 = tcg_temp_new();
> +    t0 = tcg_temp_new();
> +
> +    tcg_gen_mov_tl(cr0, cpu_so);
>       gen_set_access_type(ctx, ACCESS_RES);
> -    gen_addr_reg_index(ctx, t0);
> -    tcg_gen_brcond_tl(TCG_COND_NE, t0, cpu_reserve, l1);
> -    tcg_gen_brcondi_tl(TCG_COND_NE, cpu_reserve_size, memop_size(memop), l1);
> +    gen_addr_reg_index(ctx, EA);
> +    tcg_gen_brcond_tl(TCG_COND_NE, EA, cpu_reserve, lfail);
> +    tcg_gen_brcondi_tl(TCG_COND_NE, cpu_reserve_size, memop_size(memop), lfail);
>   
> -    t0 = tcg_temp_new();
>       tcg_gen_atomic_cmpxchg_tl(t0, cpu_reserve, cpu_reserve_val,
> -                              cpu_gpr[reg], ctx->mem_idx,
> -                              DEF_MEMOP(memop) | MO_ALIGN);
> +                              cpu_gpr[rs], ctx->mem_idx,
> +                              memop | MO_ALIGN);

Lost DEF_MEMOP here.  Otherwise,

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~