[llvm] [VectorCombine] foldShuffleOfShuffles - fold shuffle(shuffle(x,y),poison) length changing masks (PR #144690)

[LLVM Continuous Integration via llvm-commits]

llvm-ci wrote:

LLVM Buildbot has detected a new failure on builder `openmp-offload-sles-build-only` running on `rocm-worker-hw-04-sles` while building `llvm` at step 6 "Add check check-clang".

Full details are available at: https://lab.llvm.org/buildbot/#/builders/140/builds/25477

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

```
Step 6 (Add check check-clang) failure: test (failure)
******************** TEST 'Clang-Unit :: ./AllClangUnitTests/34/48' FAILED ********************
Script(shard):
--
GTEST_OUTPUT=json:/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/tools/clang/unittests/./AllClangUnitTests-Clang-Unit-14986-34-48.json GTEST_SHUFFLE=0 GTEST_TOTAL_SHARDS=48 GTEST_SHARD_INDEX=34 /home/botworker/bbot/builds/openmp-offload-sles-build/llvm.build/tools/clang/unittests/./AllClangUnitTests
--

Note: This is test shard 35 of 48.
[==========] Running 510 tests from 104 test suites.
[----------] Global test environment set-up.
[----------] 1 test from MinimizeSourceToDependencyDirectivesTest
[ RUN      ] MinimizeSourceToDependencyDirectivesTest.SplitIdentifier
[       OK ] MinimizeSourceToDependencyDirectivesTest.SplitIdentifier (0 ms)
[----------] 1 test from MinimizeSourceToDependencyDirectivesTest (0 ms total)

[----------] 1 test from LexerTest
[ RUN      ] LexerTest.GetSourceTextInMiddleOfMacroArgument
[       OK ] LexerTest.GetSourceTextInMiddleOfMacroArgument (0 ms)
[----------] 1 test from LexerTest (0 ms total)

[----------] 1 test from PPCallbacksTest
[ RUN      ] PPCallbacksTest.OpenCLExtensionPragmaDisabled
[       OK ] PPCallbacksTest.OpenCLExtensionPragmaDisabled (0 ms)
[----------] 1 test from PPCallbacksTest (0 ms total)

[----------] 1 test from ToolChainTest
[ RUN      ] ToolChainTest.VFSGnuLibcxxPathNoSysroot
[       OK ] ToolChainTest.VFSGnuLibcxxPathNoSysroot (0 ms)
[----------] 1 test from ToolChainTest (0 ms total)

[----------] 1 test from MultilibTest
[ RUN      ] MultilibTest.SelectHard
[       OK ] MultilibTest.SelectHard (0 ms)
[----------] 1 test from MultilibTest (0 ms total)

[----------] 2 tests from ExprMutationAnalyzerTest
[ RUN      ] ExprMutationAnalyzerTest.ArrayToPointerDecay
[       OK ] ExprMutationAnalyzerTest.ArrayToPointerDecay (2 ms)
[ RUN      ] ExprMutationAnalyzerTest.PointeeMutatedByAssign
[       OK ] ExprMutationAnalyzerTest.PointeeMutatedByAssign (4 ms)
[----------] 2 tests from ExprMutationAnalyzerTest (6 ms total)

[----------] 1 test from ArenaTest
[ RUN      ] ArenaTest.GetOrCreateDisjunctionReturnsSameExprOnSubsequentCalls
[       OK ] ArenaTest.GetOrCreateDisjunctionReturnsSameExprOnSubsequentCalls (0 ms)
[----------] 1 test from ArenaTest (0 ms total)

[----------] 1 test from EnvironmentTest
[ RUN      ] EnvironmentTest.LambdaCapturingThisInFieldInitializer
[       OK ] EnvironmentTest.LambdaCapturingThisInFieldInitializer (1 ms)
[----------] 1 test from EnvironmentTest (1 ms total)
...

```

</details>

https://github.com/llvm/llvm-project/pull/144690