[llvm] [X86] combineSelect - `fold select(c,vtrunc(x),0)` => `X86ISD::MTRUNC(x,c)` (PR #212865)

[Simon Pilgrim via llvm-commits]

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RKSimon wrote:

```suggestion
  // Fold vselect(mask, vtrunc(x), 0) to vmtrunc for masked vpmovqb.
```

https://github.com/llvm/llvm-project/pull/212865