[llvm] [AArch64][GISel] Always fold G_SHL into addressing mode where possible, unless the subtarget has addr-lsl-slow-14 (PR #96603)

[Amara Emerson via llvm-commits]

aemerson wrote:

You can pre-commit the tests (don't have to have a PR) so that this change shows the code differences more clearly.

https://github.com/llvm/llvm-project/pull/96603