[llvm] [VPlan] Add VPlan-dump-based test for predication (PR #180794)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `ml-opt-rel-x86-64` running on `ml-opt-rel-x86-64-b2` while building `llvm` at step 6 "test-build-unified-tree-check-all".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/185/builds/33852

<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/VPlan/predicator.ll' FAILED ********************
Exit Code: 1

Command Output (stdout):
--
# RUN: at line 2
/b/ml-opt-rel-x86-64-b1/build/bin/opt -disable-output < /b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/LoopVectorize/VPlan/predicator.ll -p loop-vectorize -vplan-print-after=introduceMasksAndLinearize -vplan-print-vector-region-scope 2>&1 | /b/ml-opt-rel-x86-64-b1/build/bin/FileCheck /b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/LoopVectorize/VPlan/predicator.ll
# executed command: /b/ml-opt-rel-x86-64-b1/build/bin/opt -disable-output -p loop-vectorize -vplan-print-after=introduceMasksAndLinearize -vplan-print-vector-region-scope
# executed command: /b/ml-opt-rel-x86-64-b1/build/bin/FileCheck /b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/LoopVectorize/VPlan/predicator.ll
# .---command stderr------------
# | /b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/LoopVectorize/VPlan/predicator.ll:101:15: error: CHECK-NEXT: expected string not found in input
# | ; CHECK-NEXT: BLEND ir<%phi4> = ir<%add3>/vp<[[VP7]]> ir<%add0>/vp<[[VP8]]>
# |               ^
# | <stdin>:60:33: note: scanning from here
# |  EMIT vp<%9> = or vp<%7>, vp<%8>
# |                                 ^
# | <stdin>:60:33: note: with "VP7" equal to "%7"
# |  EMIT vp<%9> = or vp<%7>, vp<%8>
# |                                 ^
# | <stdin>:60:33: note: with "VP8" equal to "%8"
# |  EMIT vp<%9> = or vp<%7>, vp<%8>
# |                                 ^
# | <stdin>:61:2: note: possible intended match here
# |  BLEND ir<%phi4> = ir<%add3>/vp<%7> ir<%iv>/vp<%8>
# |  ^
# | 
# | Input file: <stdin>
# | Check file: /b/ml-opt-rel-x86-64-b1/llvm-project/llvm/test/Transforms/LoopVectorize/VPlan/predicator.ll
# | 
# | -dump-input=help explains the following input dump.
# | 
# | Input was:
# | <<<<<<
# |             .
# |             .
# |             .
# |            55:  EMIT ir<%add3> = add ir<%iv>, ir<3>, vp<%7> 
# |            56:  Successor(s): bb4 
# |            57:  
# |            58:  bb4: 
# |            59:  EMIT vp<%8> = not ir<%c0> 
# |            60:  EMIT vp<%9> = or vp<%7>, vp<%8> 
# | next:101'0                                     X error: no match found
# | next:101'1                                       with "VP7" equal to "%7"
# | next:101'2                                       with "VP8" equal to "%8"
# |            61:  BLEND ir<%phi4> = ir<%add3>/vp<%7> ir<%iv>/vp<%8> 
# | next:101'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# | next:101'3      ?                                                  possible intended match
# |            62:  EMIT store ir<%phi4>, ir<%gep>, vp<%9> 
# | next:101'0     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...

```

</details>

https://github.com/llvm/llvm-project/pull/180794