[llvm] [AArch64] Reland merge index address with large offset into base address (PR #79951)

[via llvm-commits]

vfdff wrote:

* I am surprised that it does affect the back end of the powerpc64. also simplified test base on above   ppc64-nest.ll, https://gcc.godbolt.org/z/YdG4r3vcb
   > get same issue with :  llvm_build_ubsan/bin/llc --mtriple powerpc64-unknown-linux-gnu test.ll
   > works fine with: llvm_build_ubsan/bin/llc --mtriple aarch64-unknown-linux-gnu test.ll

https://github.com/llvm/llvm-project/pull/79951