From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from eggs.gnu.org ([2001:4830:134:3::10]:33114)
	by lists.gnu.org with esmtp (Exim 4.71)
	(envelope-from <rth7680@gmail.com>) id 1ZhOJX-0005Nx-2n
	for qemu-devel@nongnu.org; Wed, 30 Sep 2015 16:49:23 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71)
	(envelope-from <rth7680@gmail.com>) id 1ZhOJS-000439-Vg
	for qemu-devel@nongnu.org; Wed, 30 Sep 2015 16:49:22 -0400
Received: from mail-pa0-x232.google.com ([2607:f8b0:400e:c03::232]:34142)
	by eggs.gnu.org with esmtp (Exim 4.71)
	(envelope-from <rth7680@gmail.com>) id 1ZhOJS-00042z-QT
	for qemu-devel@nongnu.org; Wed, 30 Sep 2015 16:49:18 -0400
Received: by padhy16 with SMTP id hy16so50812616pad.1
	for <qemu-devel@nongnu.org>; Wed, 30 Sep 2015 13:49:18 -0700 (PDT)
Sender: Richard Henderson <rth7680@gmail.com>
References: <1443627027-2193-1-git-send-email-james.hogan@imgtec.com>
	<1443627027-2193-5-git-send-email-james.hogan@imgtec.com>
From: Richard Henderson <rth@twiddle.net>
Message-ID: <560C4AC7.5010107@twiddle.net>
Date: Thu, 1 Oct 2015 06:49:11 +1000
MIME-Version: 1.0
In-Reply-To: <1443627027-2193-5-git-send-email-james.hogan@imgtec.com>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [Qemu-devel] [PATCH 4/7] tcg/mips: Support r6 JR encoding
List-Id: <qemu-devel.nongnu.org>
List-Unsubscribe: <https://lists.nongnu.org/mailman/options/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <https://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: James Hogan <james.hogan@imgtec.com>, qemu-devel@nongnu.org
Cc: Leon Alrae <leon.alrae@imgtec.com>, Aurelien Jarno <aurelien@aurel32.net>

On 10/01/2015 01:30 AM, James Hogan wrote:
> MIPSr6 encodes JR as JALR with zero as the link register, and the pre-r6
> JR encoding is removed. Update TCG to use the new encoding when built
> for r6.
>
> We still use the old encoding for pre-r6, so as not to confuse return
> prediction stack hardware which may detect only particular encodings of
> the return instruction.
>
> Signed-off-by: James Hogan <james.hogan@imgtec.com>
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Aurelien Jarno <aurelien@aurel32.net>
> ---
>   tcg/mips/tcg-target.c | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/tcg/mips/tcg-target.c b/tcg/mips/tcg-target.c
> index 4305af967326..0a16140b1cdb 100644
> --- a/tcg/mips/tcg-target.c
> +++ b/tcg/mips/tcg-target.c
> @@ -288,7 +288,7 @@ typedef enum {
>       OPC_SRLV     = OPC_SPECIAL | 0x06,
>       OPC_ROTRV    = OPC_SPECIAL | (0x01 <<  6) | 0x06,
>       OPC_SRAV     = OPC_SPECIAL | 0x07,
> -    OPC_JR       = OPC_SPECIAL | 0x08,
> +    OPC_JR_R5    = OPC_SPECIAL | 0x08,
>       OPC_JALR     = OPC_SPECIAL | 0x09,
>       OPC_MOVZ     = OPC_SPECIAL | 0x0A,
>       OPC_MOVN     = OPC_SPECIAL | 0x0B,
> @@ -322,6 +322,9 @@ typedef enum {
>       OPC_SEH      = OPC_SPECIAL3 | 0x620,
>   } MIPSInsn;
>
> +/* MIPS r6 doesn't have JR, JALR should be used instead */
> +#define OPC_JR (use_mips32r6_instructions ? OPC_JALR : OPC_JR_R5)

This could be done in the enum instead of a define, but otherwise,


Reviewed-by: Richard Henderson <rth@twiddle.net>


r~