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Date: Thu, 01 Jul 2010 09:17:10 -0700
From: Richard Henderson <rth@twiddle.net>
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Subject: Re: [Qemu-devel] [Bug 600589] [NEW] xchg r8,rax treated as nop
References: <20100701120434.6052.96178.malonedeb@potassium.ubuntu.com>
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To: Bug 600589 <600589@bugs.launchpad.net>
Cc: Vic3Dexe <vic3dexe@gmail.com>, qemu-devel@nongnu.org

On 07/01/2010 05:04 AM, Vic3Dexe wrote:
> Public bug reported:
> 
> xchg r8,rax (49h 90h) executed as nop (90h) in long mode, in other words
> REX not used.
> 
> qemu 0.12.4, host Win 7 x64,  running qemu-system-x86_64.exe.
> 
> ** Affects: qemu
>      Importance: Undecided
>          Status: New
> 

Verified.  Test case for x86_64-linux-user:

	.globl	main
	.type	main, @function
main:
	movl	$0, %r8d
	movl	$1, %eax
	xchgq	%r8, %rax
	ret

Expected result is exit status 0.


r~