Re: [Qemu-ppc] [Qemu-devel] [PATCH] PPC64: Add support for ldbrx and stdbrx instructions

[Alexander Graf]

On 09.02.2012, at 08:43, Thomas Huth wrote:

> Am Thu, 9 Feb 2012 11:26:09 +1100
> schrieb David Gibson <address@hidden>:
> 
>> On Wed, Feb 08, 2012 at 02:27:35PM +0100, Thomas Huth wrote:
>>> Am Wed, 8 Feb 2012 21:48:40 +1100
>>> schrieb David Gibson <address@hidden>:
>>> 
>>>> On Wed, Feb 08, 2012 at 10:54:21AM +0400, malc wrote:
>>>>> On Wed, 8 Feb 2012, David Gibson wrote:
>>>>> 
>>>>>> From: Thomas Huth <address@hidden>
>>>>>> 
>>>>>> These instructions for loading and storing byte-swapped 64-bit values 
>>>>>> have
>>>>>> been introduced in PowerISA 2.06.
>>>>>> 
>>>>>> Signed-off-by: Thomas Huth <address@hidden>
>>>>>> ---
>>>>>> target-ppc/translate.c |   30 ++++++++++++++++++++++++++++++
>>>>>> 1 files changed, 30 insertions(+), 0 deletions(-)
>>>>> 
>>>>> I seem to recall that POWER5 machine i had access to didn't have 
>>>>> ld/stdbrx while CBE did have it (or was it the other way around?)
>>>>> so question is - is PPC_64B sufficient?
>>>> 
>>>> Ah, I think it's not.  I think I spotted that before, but then forgot
>>>> about it.  Thanks for the reminder.
>>> 
>>> Maybe it's a better idea to use PPC_64BX here? ... but that flag seems
>>> to be missing in POWERPC_INSNS_POWER7... David, could PPC_64BX also be
>>> included in that flag list?
>> 
>> Um.. what exactly do you mean by 64BX?
>> 
> 
> There is a definition in target-ppc/cpu.h:
> 
>    /*   New 64 bits extensions (PowerPC 2.0x)     */
>    PPC_64BX           = 0x0000000000000040ULL,
> 
> According to the comment, I thought the PPC_64BX might be designed
> for new 64-bit instructions?

Well, we need to be a bit more specific here to know what we're implementing. 
The flag above just indicates the lq opcode:

  target-ppc/translate.c:GEN_HANDLER(lq, 0x38, 0xFF, 0xFF, 0x00000000, 
PPC_64BX),

So how about we create a new PPC2 flag for BRX and add that in POWER7 INSNS? If 
you could find out if Cell also supports these instructions, that'd be great. I 
don't have a 2.05 spec handy and 2.04 doesn't implement it yet.


Alex