Re: [Qemu-devel] [PATCH 1/8] target/ppc: Optimize emulation of lvsl and lvsr instructions

[Richard Henderson]

On 6/6/19 5:15 AM, Stefan Brankovic wrote:
> +    tcg_gen_addi_i64(result, sh, 7);
> +    for (i = 7; i >= 1; i--) {
> +        tcg_gen_shli_i64(tmp, sh, i * 8);
> +        tcg_gen_or_i64(result, result, tmp);
> +        tcg_gen_addi_i64(sh, sh, 1);
> +    }

Better to replicate sh into the 8 positions and then use one add.

    tcg_gen_muli_i64(sh, sh, 0x0101010101010101ull);
    tcg_gen_addi_i64(hi_result, sh, 0x0001020304050607ull);
    tcg_gen_addi_i64(lo_result, sh, 0x08090a0b0c0d0e0full);

and

    tcg_gen_subfi_i64(hi_result, 0x1011121314151617ull, sh);
    tcg_gen_subfi_i64(lo_result, 0x18191a1b1c1d1e1full, sh);

for lvsr.


r~