[llvm] [AArch64] Improve code generation of bool vector reduce operations (PR #115713)

[Csanád Hajdú via llvm-commits]

Il-Capitano wrote:

@davemgreen @nikic 
It looks like this breaks some things when compiling with `-Ofast`: https://linaro.atlassian.net/browse/LLVM-1481

I was able to reproduce the issue with this test case: https://github.com/fujitsu/compiler-test-suite/blob/main/C/0030/0030_0066.c

The issue seems to be triggered during LTO. If I compile the test case to assembly, there's no difference between `-O3` and `-Ofast`.

https://github.com/llvm/llvm-project/pull/115713