x86: Check XMM destination when optimizing 128-bit VPBROADCASTQ

x86: Check XMM destination when optimizing 128-bit VPBROADCASTQ

commit eb4031cb20aa710834be891f8638e04dbba81edc
Author: Jan Beulich <jbeulich@suse.com>
Date:   Tue Jul 4 17:07:26 2023 +0200

    x86: optimize 128-bit VPBROADCASTQ to VPUNPCKLQDQ

was supposed to optimize

vpbroadcastq %xmmN, %xmmM  -> vpunpcklqdq %xmmN, %xmmN, %xmmM (N < 8)

But it didn't check if the destination operand is XMM.  As the result, it
turned:

vpbroadcastq %xmmN, %ymmM

into

vpunpcklqdq %xmmN, %xmmN, %xmmM

Fixing it by checking XMM destination.

	PR gas/34171
	* config/tc-i386.c (optimize_encoding): Check XMM destination
	when optimizing 128-bit VPBROADCASTQ.
	* testsuite/gas/i386/optimize-2.d: Updated.
	* testsuite/gas/i386/optimize-2.s: Add 256-bit vpbroadcastq.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>