Redundant logical operations left after early splitting

[Jeff Law]

Dave Korn wrote:
> On 20 February 2008 16:34, Jeff Law wrote:
> 
>> Paolo Bonzini wrote:
>>>>> Is there any particular function or pass that should be dealing with
>>>>> IOR rx,0 - that I could trace thru and figure out why it does not
>>>>> like it (or never gets there)?
>>>> I would be looking in combine and simplify-rtx (which is called by
>>>> combine).  If your splitter triggers after combine, then I'm not
>>>> immediately sure where to look -- I'm not offhand aware of a pass
>>>> after combine which would call into simplify-rtx to perform this
>>>> optimization.
>>> Me neither, but this
> 
>>> could be a place where it is done.
>>>
>> I'm still looking at this, but I don't see much of a chance to attack
>> this specific problem in the combiner.
>>
>> I'm thinking this is going to need to be attacked along one of three
>> lines:
>>
> 
>   In the meantime, Andy's quickest and safest option is probably to use peepholes to eliminate the redundant insns altogether, rather than having to replace them with nops.
Probably true.

Jeff