[PATCH] D84873: AMDGPU: In determining load clobbering in AnnotateUniform, don't scan if there are too many blocks.

[Changpeng Fang via Phabricator via llvm-commits]

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In D84873#2182944 <https://reviews.llvm.org/D84873#2182944>, @asbirlea wrote:

> In D84873#2182544 <https://reviews.llvm.org/D84873#2182544>, @arsenm wrote:
>
>> Does MemorySSA have the same problem? Could we just switch this to use MemorySSA?
>
> Disclaimer: I know nothing about this pass or the purpose of this patch, just trying to answer this question.
> MemorySSA has its own internal threshold limiting the number of **memory instructions** that are traversed upwards. It does not care at how many blocks those memory instructions are spread over.

Thanks for the comments! I see that in MemorySSA, it scans 100 memory instructions upwards to find whether it is clobbered.
In our case, we essentially check every basic block,  and a max of also 100 instructions in each block to find the pointer dependence:
MDR->getPointerDependencyFrom(MemoryLocation(Ptr), true, StartIt, BB, Load);
At this moment, I am not clear how can we use the existing functionality in MemorySSA for our purpose.


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