[PATCH] D105661: [PowerPC] Add frame index alignment check if the the addressing mode is DS/DQ-Form, and fall back to X-Form if necessary.

[Amy Kwan via Phabricator via llvm-commits]

amyk created this revision.
amyk added reviewers: nemanjai, power-llvm-team, PowerPC.
amyk added projects: PowerPC, LLVM.
Herald added subscribers: shchenz, arphaman, hiraditya.
amyk requested review of this revision.

This patch adds a function that checks whether or not the frame index
is aligned when the computed addressing mode is an aligned D-Form (DS, or DQ-Form).
If the frame index appears to be unaligned, within these two modes, reset
the mode to X-Form in order to fall back to selection X-Form loads.

A test case is added to ensure that the test emits X-Form loads and not DQ-Form
loads since the frame index is not aligned within the test case.

For this patch, `lxvx` is produced since it's pattern utilizes `ForceXForm`, but this is 
to ensure that the  follow up patch,  D95115 <https://reviews.llvm.org/D95115>,  will continue to produce `lxvx` when the instruction is 
updated to no longer use `ForceXForm` (and instead just use `XForm`).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D105661

Files:
  llvm/lib/Target/PowerPC/PPCISelLowering.cpp
  llvm/test/CodeGen/PowerPC/unaligned-dqform-ld.ll

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