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Re: [Patch, AArch64] Fix shuffle for big-endian.

From: Tejas Belagod <tbelagod at arm dot com>
To: Richard Henderson <rth at redhat dot com>, Marcus Shawcroft <Marcus dot Shawcroft at arm dot com>
Cc: Alan Lawrence <Alan dot Lawrence at arm dot com>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
Date: Tue, 22 Apr 2014 14:40:59 +0100
Subject: Re: [Patch, AArch64] Fix shuffle for big-endian.
Authentication-results: sourceware.org; auth=none
References: <53077F31 dot 8070003 at arm dot com> <533078AC dot 3020307 at redhat dot com> <533C1BAB dot 1020509 at arm dot com> <533EADB6 dot 2060808 at arm dot com>

Alan Lawrence wrote:

Sorry to be pedantic again, but 'wierd' should be spelt 'weird'. Otherwise,
looks good to me and much neater than before. (Seems you'd rather keep the
re-enabling, here and in the testsuite, for another patch?)


Hi,

Yes, the re-enabling is another patch.

Thanks for the typo correction. OK for trunk with that change?

Thanks,
Tejas.

--Alan

Tejas Belagod wrote:

Richard Henderson wrote:

On 02/21/2014 08:30 AM, Tejas Belagod wrote:

+      /* If two vectors, we end up with a wierd mixed-endian mode on NEON.  */
+      if (BYTES_BIG_ENDIAN)
+	{
+	  if (!d->one_vector_p && d->perm[i] & nunits)
+	    {
+	      /* Extract the offset.  */
+	      elt = d->perm[i] & (nunits - 1);
+	      /* Reverse the top half.  */
+	      elt = nunits - 1 - elt;
+	      /* Offset it by the bottom half.  */
+	      elt += nunits;
+	    }
+	  else
+	    elt = nunits - 1 - d->perm[i];
+	}

Isn't this just

  elt = d->perm[i] ^ (nunits - 1);

all the time?  I.e. invert the index within the word,
but leave the word index (nunits) unchanged.

Here is a revised patch. OK for stage-1?

Thanks
Tejas.

2014-04-02  Tejas Belagod  <tejas.belagod@yahoo.com>

gcc/

         * config/aarch64/aarch64.c (aarch64_evpc_tbl): Reverse order of elements
	for big-endian.

Follow-Ups:
- Re: [Patch, AArch64] Fix shuffle for big-endian.
  - From: Marcus Shawcroft

References:
- Re: [Patch, AArch64] Fix shuffle for big-endian.
  - From: Tejas Belagod
- Re: [Patch, AArch64] Fix shuffle for big-endian.
  - From: Alan Lawrence

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