Emit vp.strided.load/store from LoopVectorizer

[lukel97]

Now that #147297 is landed there are some follow up items to emit strided accesses in more places:

• Support strided store
• Transform reverse access into strided access with -1 stride.
• Transform gather/scatter with uniform address into strided access with 0 stride.
• Transform interleaved accesses into multiple strided accesses if profitable.

@Mel-Chen @ElvisWang123 I presume you plan on taking on some/most of these items? If there's any you don't plan on taking a look at let me know, I'd be happy to help with some of this work.

[llvmorg-github-actions]

@llvm/issue-subscribers-backend-risc-v

Author: Luke Lau (lukel97)

Details

Now that #147297 is landed there are some follow up items to emit strided accesses in more places:

• Support strided store
• Transform reverse access into strided access with -1 stride.
• Transform gather/scatter with uniform address into strided access with 0 stride.
• Transform interleaved accesses into multiple strided accesses if profitable.

@Mel-Chen @ElvisWang123 I presume you plan on taking on some/most of these items? If there's any you don't plan on taking a look at let me know, I'd be happy to help with some of this work.