[llvm] [VPlan] Introduce m_Cmp; match more compares (PR #154771)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `llvm-clang-x86_64-sie-win` running on `sie-win-worker` while building `llvm` at step 7 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/46/builds/22231

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

```
Step 7 (test-build-unified-tree-check-all) failure: test (failure)
******************** TEST 'LLVM :: Transforms/LoopVectorize/single-early-exit-interleave-only.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
z:\b\llvm-clang-x86_64-sie-win\build\bin\opt.exe -p loop-vectorize -force-vector-width=1 -force-vector-interleave=2 -S Z:\b\llvm-clang-x86_64-sie-win\llvm-project\llvm\test\Transforms\LoopVectorize\single-early-exit-interleave-only.ll | z:\b\llvm-clang-x86_64-sie-win\build\bin\filecheck.exe Z:\b\llvm-clang-x86_64-sie-win\llvm-project\llvm\test\Transforms\LoopVectorize\single-early-exit-interleave-only.ll
# executed command: 'z:\b\llvm-clang-x86_64-sie-win\build\bin\opt.exe' -p loop-vectorize -force-vector-width=1 -force-vector-interleave=2 -S 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\llvm\test\Transforms\LoopVectorize\single-early-exit-interleave-only.ll'
# note: command had no output on stdout or stderr
# executed command: 'z:\b\llvm-clang-x86_64-sie-win\build\bin\filecheck.exe' 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\llvm\test\Transforms\LoopVectorize\single-early-exit-interleave-only.ll'
# .---command stderr------------
# | Z:\b\llvm-clang-x86_64-sie-win\llvm-project\llvm\test\Transforms\LoopVectorize\single-early-exit-interleave-only.ll:22:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: [[TMP5:%.*]] = icmp eq i8 [[TMP3]], 0
# |               ^
# | <stdin>:18:20: note: scanning from here
# |  %4 = and i8 %2, %g
# |                    ^
# | <stdin>:18:20: note: with "TMP3" equal to "%3"
# |  %4 = and i8 %2, %g
# |                    ^
# | <stdin>:43:2: note: possible intended match here
# |  %c = icmp eq i8 %a, 0
# |  ^
# | Z:\b\llvm-clang-x86_64-sie-win\llvm-project\llvm\test\Transforms\LoopVectorize\single-early-exit-interleave-only.ll:91:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: [[TMP5:%.*]] = icmp eq i32 [[TMP3]], 0
# |               ^
# | <stdin>:71:32: note: scanning from here
# |  %4 = load i32, ptr %2, align 4
# |                                ^
# | <stdin>:71:32: note: with "TMP3" equal to "%3"
# |  %4 = load i32, ptr %2, align 4
# |                                ^
# | <stdin>:96:2: note: possible intended match here
# |  %c = icmp eq i32 %l, 0
# |  ^
# | 
# | Input file: <stdin>
# | Check file: Z:\b\llvm-clang-x86_64-sie-win\llvm-project\llvm\test\Transforms\LoopVectorize\single-early-exit-interleave-only.ll
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |             1: ; ModuleID = 'Z:\b\llvm-clang-x86_64-sie-win\llvm-project\llvm\test\Transforms\LoopVectorize\single-early-exit-interleave-only.ll' 
# |             2: source_filename = "Z:\\b\\llvm-clang-x86_64-sie-win\\llvm-project\\llvm\\test\\Transforms\\LoopVectorize\\single-early-exit-interleave-only.ll" 
# |             3:  
# |             4: define i8 @iv_used_in_exit_with_math(i8 noundef %g) { 
# | label:8'0      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# | label:8'1      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# | same:9'0                                            ^~~~~~~~~~~~~~~~
...

```

</details>

https://github.com/llvm/llvm-project/pull/154771