Re: [Qemu-devel] [PATCH 08/10 v11] target-tilegx: Add several helpers for instructions translation

[Richard Henderson <rth@twiddle.net>]

On 05/30/2015 02:17 PM, Chen Gang wrote:
> +    for (count = 0; count < 8; count++) {
> +        sel = (rsrcb >> (count * 8)) & 0xf;
> +        if (sel < 8) {
> +            vdst |= ((rdst >> (8 * sel)) & 0xff) << (count * 8);
> +        } else {
> +            vdst |= ((rsrc >> (8 * (8 - sel))) & 0xff) << (count * 8);

8 - sel is wrong; you wanted sel - 8.

That said, you can do better with masking operations.  And for brevity, let
count increment by 8.  E.g.

  uint64_t vdst = 0;
  int count;

  for (count = 0; count < 64; count += 8) {
    uint64_t sel = rsrcb >> count;
    uint64_t src = (sel & 8 ? rsrc : rdst);
    vdst |= ((src >> ((sel & 7) * 8)) & 0xff) << count;
  }


r~