[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 `clang-debian-cpp20` running on `clang-debian-cpp20` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/108/builds/16902

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

```
Step 6 (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 (stderr):
--
/vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/opt -p loop-vectorize -force-vector-width=1 -force-vector-interleave=2 -S /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/Transforms/LoopVectorize/single-early-exit-interleave-only.ll | /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/FileCheck /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/Transforms/LoopVectorize/single-early-exit-interleave-only.ll # RUN: at line 2
+ /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/opt -p loop-vectorize -force-vector-width=1 -force-vector-interleave=2 -S /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/Transforms/LoopVectorize/single-early-exit-interleave-only.ll
+ /vol/worker/clang-debian-cpp20/clang-debian-cpp20/build/bin/FileCheck /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/Transforms/LoopVectorize/single-early-exit-interleave-only.ll
/vol/worker/clang-debian-cpp20/clang-debian-cpp20/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
 ^
/vol/worker/clang-debian-cpp20/clang-debian-cpp20/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: /vol/worker/clang-debian-cpp20/clang-debian-cpp20/llvm-project/llvm/test/Transforms/LoopVectorize/single-early-exit-interleave-only.ll

-dump-input=help explains the following input dump.

Input was:
<<<<<<
           .
           .
           .
          13:  %offset.idx = trunc i32 %index to i8 
          14:  %0 = add i8 %offset.idx, 1 
          15:  %1 = shl nuw i8 1, %offset.idx 
          16:  %2 = shl nuw i8 1, %0 
          17:  %3 = and i8 %1, %g 
          18:  %4 = and i8 %2, %g 
next:22'0                        X error: no match found
...

```

</details>

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