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

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Him188 wrote:

> You can pre-commit the tests

Nice suggestion. I have prepared one test commit before the code commit. You can review the second commit https://github.com/llvm/llvm-project/pull/96603/commits/c6ec76e712ad7d618e62dc72e4f64a0d03e2644d to see what's changed.

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