[llvm] [InstCombine] simplify `icmp pred x, ~x` (PR #73990)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-win-x-aarch64` running on `as-builder-2` while building `llvm` at step 9 "test-check-llvm".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/193/builds/5492

<details>
<summary>Here is the relevant piece of the build log for the reference</summary>

```
Step 9 (test-check-llvm) failure: Test just built components: check-llvm completed (failure)
******************** TEST 'LLVM :: Transforms/InstCombine/icmp-of-xor-x.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
c:\buildbot\as-builder-2\x-aarch64\build\bin\opt.exe < C:\buildbot\as-builder-2\x-aarch64\llvm-project\llvm\test\Transforms\InstCombine\icmp-of-xor-x.ll -passes=instcombine -S | c:\buildbot\as-builder-2\x-aarch64\build\bin\filecheck.exe C:\buildbot\as-builder-2\x-aarch64\llvm-project\llvm\test\Transforms\InstCombine\icmp-of-xor-x.ll
# executed command: 'c:\buildbot\as-builder-2\x-aarch64\build\bin\opt.exe' -passes=instcombine -S
# executed command: 'c:\buildbot\as-builder-2\x-aarch64\build\bin\filecheck.exe' 'C:\buildbot\as-builder-2\x-aarch64\llvm-project\llvm\test\Transforms\InstCombine\icmp-of-xor-x.ll'
# .---command stderr------------
# | C:\buildbot\as-builder-2\x-aarch64\llvm-project\llvm\test\Transforms\InstCombine\icmp-of-xor-x.ll:127:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
# |               ^
# | <stdin>:66:30: note: scanning from here
# | define <2 x i1> @src_sgt_vec(<2 x i8> %x) {
# |                              ^
# | <stdin>:67:2: note: possible intended match here
# |  %cmp = icmp sgt <2 x i8> %x, splat (i8 -1)
# |  ^
# | C:\buildbot\as-builder-2\x-aarch64\llvm-project\llvm\test\Transforms\InstCombine\icmp-of-xor-x.ll:148:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
# |               ^
# | <stdin>:76:30: note: scanning from here
# | define <2 x i1> @src_sge_vec(<2 x i8> %x) {
# |                              ^
# | <stdin>:77:2: note: possible intended match here
# |  %cmp = icmp sgt <2 x i8> %x, splat (i8 -1)
# |  ^
# | C:\buildbot\as-builder-2\x-aarch64\llvm-project\llvm\test\Transforms\InstCombine\icmp-of-xor-x.ll:169:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
# |               ^
# | <stdin>:86:30: note: scanning from here
# | define <2 x i1> @src_ult_vec(<2 x i8> %x) {
# |                              ^
# | <stdin>:87:2: note: possible intended match here
# |  %cmp = icmp sgt <2 x i8> %x, splat (i8 -1)
# |  ^
# | C:\buildbot\as-builder-2\x-aarch64\llvm-project\llvm\test\Transforms\InstCombine\icmp-of-xor-x.ll:190:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
# |               ^
# | <stdin>:96:30: note: scanning from here
# | define <2 x i1> @src_ule_vec(<2 x i8> %x) {
# |                              ^
# | <stdin>:97:2: note: possible intended match here
# |  %cmp = icmp sgt <2 x i8> %x, splat (i8 -1)
# |  ^
# | C:\buildbot\as-builder-2\x-aarch64\llvm-project\llvm\test\Transforms\InstCombine\icmp-of-xor-x.ll:200:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: [[CMP:%.*]] = icmp sgt <2 x i8> [[X:%.*]], <i8 -1, i8 -1>
# |               ^
# | <stdin>:101:34: note: scanning from here
...

```

</details>

https://github.com/llvm/llvm-project/pull/73990