[LLVMdev] addrspace attribute and intrisics

[Mon P Wang]

Hi,

Though I haven't looked into the implementation details, at the high  
level, I personally think having the address space argument is cleaner  
than having it encoded as a pointer.  The memory barrier places a  
barrier on the entire address space.  When I see the %ptr11 on the  
memory barrier instruction, my first instinct is to that it is a  
memory barrier on the region of memory that %ptr11 points to.  What  
are other people opinions?

  -- Mon Ping

On Jul 7, 2008, at 6:36 AM, Benedict Gaster wrote:

> Thanks, I can now see that this can be implemented with Verifier.cpp.
>
> Even with this ability It is unclear that defining llvm.memory.barrier
> with an explicit address space argument is preferred over the
> llvm.memory.fence definition where the addrspace is encoded as part of
> the type as will be the case with the other atomic operations. What do
> you think?
>
> Ben
>
> On 7 Jul 2008, at 13:43, Gordon Henriksen wrote:
>
>> On 2008-07-07, at 05:40, Benedict Gaster wrote:
>>
>>>       %r1 = call i32 @llvm.atomic.load.add.p0i32( i32 addrspace(0)*
>>> %ptr0, i32 4)
>>> 	%r2 = call i32 @llvm.atomic.load.add.p11i32( i32 addrspace(11)*
>>> %ptr11, i32 4)
>>> 	call void @llvm.memory.barrier(i1 true, i1 true, i1 false, i1  
>>> false,
>>> i32 11, i1 false) ; force read-modify-write %ptr11 to complete
>>>
>>> A problem with this approach is that developing a new pass over the
>>> IL that works with address spaces, will have to include knowledge
>>> that for certain operations address space information is encoded as
>>> data rather than as types and in general, it may not be able to
>>> statically determine the particular address space.
>>
>> It's quite possible to restrict an argument to an intrinsic to an
>> immediate constant. See llvm.gcroot for an example.
>>
>> — Gordon
>>
>>
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>
>
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