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RE: -fno-tree-cselim not working?


On 26 October 2007 23:46, David Miller wrote:

> From: "Dave Korn" 
> Date: Fri, 26 Oct 2007 17:35:44 +0100
> 
>> On 26 October 2007 17:28, Andrew Haley wrote:
>> 
>>> Richard Guenther writes:
>>>  > >
>>>  > > This is legal POSIX threads code: counter is not accessed when we do
>>>  > > not hold the mutex.  According to POSIX we do not have to declare
>>>  > > volatile memory that we only access when we hold a mutex.  >
>>>  > I hope we're not trying to support such w/o volatile counter.
>>> 
>>> I think we have to: not just for POSIX, but for the Linux kernel too.
>>> 
>>>  > Whatever POSIX says, this would pessimize generic code too much.
>>> 
>>> We don't have to do it for non-threaded code.
>> 
>>   I certainly won't object to any move to prohibit the
>> read-conditional-add-write (and related) optimisation(s) when compiling
>> with an option that explicitly specifies that we are compiling
>> multi-threaded code. 
> 
> What about signals?

  Heh, you got me there.  What about signals?
 
> Those are just another asynchronous context with similar issues.

  Sure.  Lump it all in with threaded in the above statement.
 
> Please don't point me at standards documents in your response,
> that is not what truly matters here.

  Let me generalise the above statement: 

>>   I certainly won't object to any move to prohibit 

  ... any optimisations whatsoever, including but not limited to ...

>> read-conditional-add-write (and related) optimisation(s) when compiling
>> with an option that explicitly specifies that we are compiling

  ... any kind of asynchronous or ...

>> multi-threaded code. 



    cheers,
      DaveK
-- 
Can't think of a witty .sigline today....


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