[LLVMdev] Plan to optimize atomics in LLVM

[Tim Northover]

> Longer term, I hope to improve the fence elimination of the ARM backend with
> a kind of PRE algorithm. Both of these improvements to the ARM backend
> should be fairly straightforward to port to the POWER architecture later,
> and I hope to also do that.
>
> Any reason these couldn't be done at the IR level?

I definitely agree here. At the time, it was a plausible idea (the
barriers didn't even exist in IR most of the time). But the
implementation was always going to be much more complicated and less
portable than in IR, and what we actually have is very flawed in its
own right (only applies to ARM mode, unmaintained,

Actually, I think we decided to remove it a while back, but I haven't
gotten around to it yet.

Cheers.

Tim.