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Re: [PATCH][ARM] Improve 64-bit shifts (non-NEON)


On 02/08/2012 01:12 PM, Richard Guenther wrote:
> On Wed, Feb 8, 2012 at 1:02 PM, Bernd Schmidt <bernds@codesourcery.com> wrote:
>> On 02/07/2012 11:33 PM, Steven Bosscher wrote:
>>> On Tue, Feb 7, 2012 at 11:19 PM, Ramana Radhakrishnan
>>> <ramana.radhakrishnan@linaro.org> wrote:
>>>> Hi Andrew
>>>>
>>>> I find it interesting that cond_exec's in this form survive all the
>>>> way till reload and "work".  AFAIK we could never have cond_exec's
>>>> before reload .
>>>
>>> There is nothing wrong per-se with cond_execs before reload, as long
>>> as you don't have to reload a predicate pseudo-reg.
>>
>> I thought the problem was that we'd have to emit conditional reload
>> insns and inheritance wouldn't work.
> 
> It probably depends on how DF sees conditional uses / defs.  If they
> look like regular uses / defs then I suppose un-conditional spills/reloads
> are fine - otherwise of course you'd corrupt one of the two register set
> states.

I'm pretty sure conditional defs are always RMW, but I'd have to go
look. Can't imagine it working otherwise though.


Bernd


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