[PATCH] D40831: [AArch64] Only use writeback in the load/store optimizer when needed

[John Brawn via Phabricator via llvm-commits]

john.brawn planned changes to this revision.
john.brawn added a comment.

In https://reviews.llvm.org/D40831#1027276, @evandro wrote:

> I'm not sure what is gained by not performing this optimization, if I understood the gist of it from the new test case below.  For even if the register is killed, the pointer adjustment is folded into the load or store and an instruction is eliminated.  What other optimizations are expected to be happen should this patch be applied?


I'm not quite sure what you're asking here? If you mean "what is gained by not using writeback in cases where we currently don't use writeback", then the answer is that we don't gain anything, but by not using writeback we can optimise cases that can't currently be optimised because the use of writeback would be invalid. Though the title and summary don't really convey that very well, perhaps "Allow more load/store optimization by not using writeback" or something would be better.

I'm not currently planning on working on this patch further at the moment though (but I may get back to it some time in the future), as changing to not using kill flags looks like it would take some work and I currently have other priorities.


Repository:
  rL LLVM

https://reviews.llvm.org/D40831