Re: [Qemu-devel] [PATCH v4 6/9] target-ppc: add lxvh8x instruction

[Richard Henderson]

On 09/27/2016 10:31 PM, Nikunj A Dadhania wrote:
> +DEF_HELPER_1(bswap16x4, i64, i64)

DEF_HELPER_FLAGS_1(bswap16x4, TCG_CALL_NO_RWG_SE, i64, i64)

> +    uint64_t m = 0x00ff00ff00ff00ffull;
> +    return ((x & m) << 8) | ((x >> 8) & m);

... although I suppose this is only 5 instructions, and could reasonably be
done inline too.  Especially if you shared the one 64-bit constant across the
two bswaps.


> +    if (ctx->le_mode) {
> +        tcg_gen_qemu_ld_i64(xth, EA, ctx->mem_idx, MO_BEQ);
> +        gen_helper_bswap16x4(xth, xth);
> +        tcg_gen_addi_tl(EA, EA, 8);
> +        tcg_gen_qemu_ld_i64(xtl, EA, ctx->mem_idx, MO_BEQ);
> +        gen_helper_bswap16x4(xtl, xtl);
> +    } else {
> +        tcg_gen_qemu_ld_i64(xth, EA, ctx->mem_idx, MO_BEQ);
> +        tcg_gen_addi_tl(EA, EA, 8);
> +        tcg_gen_qemu_ld_i64(xtl, EA, ctx->mem_idx, MO_BEQ);
> +    }

Better to not duplicate this.

  tcg_gen_qemu_ld_i64(xth, EA, ctx->mem_idx, MO_BEQ);
  tcg_gen_addi_tl(EA, EA, 8);
  tcg_gen_qemu_ld_i64(xtl, EA, ctx->mem_idx, MO_BEQ);
  if (ctx->le_mode) {
    gen_helper_bswap16x4(xth, xth);
    gen_helper_bswap16x4(xtl, xtl);
  }


r~