[llvm] [LLVM][AArch64] Optimize sign bit tests with TST instruction for SIGN_EXTEND patterns (PR #158061)

[guan jian via llvm-commits]

rez5427 wrote:

> Thanks for the patch. Looks like a nice optimization. It might be worth giving it a test to make sure it is producing the expected results, a boot strap or the llvm-test-suite can be a decent way to test it.

 I tried both bootstrap and llvm-test-suite, and they show nothing wrong.

https://github.com/llvm/llvm-project/pull/158061