[llvm-dev] RFC: Element-atomic memory intrinsics

[Sanjoy Das via llvm-dev]

Hi Daniel,

On Mon, May 8, 2017 at 12:08 PM, Daniel Neilson <dneilson at azul.com> wrote:
>>>       * isunordered param: bit 0 == 1 => stores to dest must be marked
>>> ‘unordered’; bit 1 == 1 => loads from src must be marked ‘unordered'
>>
>> What if the bits are zero -- will the stores / loads (depending on
>> which bit) be "ordered" in that case, or something stronger?
>>
>
>  This is partly why I prefer option 2. An ‘isunordered’ value of 0 is nonsense for the standalone atomic-unordered memory intrinsic. It would imply that neither the source nor dest needs to be loaded/stored via unordered-atomic ops, and so the memory intrinsic is identical to the ordinary non-atomic one.

Perhaps the appropriate thing to do for this option is to not have the
isunordered flag at all and instead call the intrinsic
@llvm.memcpy_element_unordered_atomic?  I suspect we probably won't
care about anything stronger than unordered atomic memcpys, and we can
always generalize if there is a need later.

-- Sanjoy