forked from OSchip/llvm-project
d9e93e8e57
While optimizing the memory instruction, we sometimes need to add offset to the value of `IV`. We could avoid doing so if the `IV.next` is already defined at the point of interest. In this case, we may get two possible advantages from this: - If the `IV` step happens to match with the offset, we don't need to add the offset at all; - We reduce overlap of live ranges of `IV` and `IV.next`. They may stop overlapping and it will lead to better register allocation. Even if the overlap will preserve, we are not introducing a new overlap, so it should be a neutral transform (Disabled this patch, will come with follow-up). Currently I've only added support for IVs that get decremented using `usub` intrinsic. We could also support `AddInstr`, however there is some weird interaction with some other transform that may lead to infinite compilation in this case (seems like same transform is done and undone over and over). I need to investigate why it happens, but generally we could do that too. The first part only handles case where this reuse fully elimiates the offset. Differential Revision: https://reviews.llvm.org/D96399 Reviewed By: reames |
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README.txt
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