[llvm] [LLVM][DAGCombiner][SVE] Fold vselect into merge_pasthru_op. (PR #146917)

[David Sherwood via llvm-commits]

david-arm wrote:

After trying to look at the almost entirely useless interface in the `[Build and Test Linux (pull_request)](https://github.com/llvm/llvm-project/actions/runs/16057099361/job/45314105433?pr=146917)` link, I downloaded the raw logs and discovered a unit test error:

```
/home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/unittests/Target/AArch64/AArch64SelectionDAGTest.cpp
2025-07-03T17:46:14.9411240Z /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/unittests/Target/AArch64/AArch64SelectionDAGTest.cpp:65:10: error: no matching member function for call to 'init'
2025-07-03T17:46:14.9412768Z    65 |     DAG->init(*MF, ORE, nullptr, nullptr, nullptr, nullptr, nullptr, MMI,
2025-07-03T17:46:14.9413290Z       |     ~~~~~^~~~
2025-07-03T17:46:14.9414010Z /home/gha/actions-runner/_work/llvm-project/llvm-project/llvm/include/llvm/CodeGen/SelectionDAG.h:472:17: note: candidate function not viable: requires 10 arguments, but 9 were provided
```

https://github.com/llvm/llvm-project/pull/146917