Re: [Qemu-devel] [PATCH] tci: Add implementation of rotl_i64, rotr_i64

[Stefan Weil]

Am 09.09.2013 16:53, schrieb Aurelien Jarno:
> On Wed, Sep 04, 2013 at 10:51:54PM +0200, Stefan Weil wrote:
>> Am 04.09.2013 22:49, schrieb Stefan Weil:
>>> It is used by qemu-ppc64 when running Debian's busybox-static.
>>>
>>> Signed-off-by: Stefan Weil <address@hidden>
>>> ---
>>>
>>> This patch is also useful for QEMU 1.6.
>> ... so I should have added qemu-stable. Done now.
>>
> Why is it needed for qemu-stable? It should only improve performance, as
> these two ops are not mandatory ops. In general I don't think we should
> have performance improvements in a stable minor release (unless of course
> it's a big regression from previous).

Hi Aurelien,

tci has always set TCG_TARGET_HAS_rot_i64, and target-ppc64 uses the
rotl_i64 and rotr_i64 TCG opcodes.

The old implementation just triggered a TODO assertion. That's how I
implemented TCI: I started with TODO assertions for all opcodes and
replaced them by real code as soon as I got a test case which used them.
Now I have a test case :-)

=> It's not a performance issue, but fixes a fatal assertion.
=> It should be used in 1.6.

Regards,
Stefan