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Subject: Re: [Qemu-devel] [PATCH 08/10 v11] target-tilegx: Add several
 helpers for instructions translation
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To: Chen Gang <xili_gchen_5257@hotmail.com>, Peter Maydell <peter.maydell@linaro.org>, =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= <afaerber@suse.de>, Chris Metcalf <cmetcalf@ezchip.com>
Cc: "walt@tilera.com" <walt@tilera.com>, Riku Voipio <riku.voipio@iki.fi>, qemu-devel <qemu-devel@nongnu.org>

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~