[llvm] [SLP]Add subvector vectorization for non-load nodes (PR #108430)

[Alexander Kornienko via llvm-commits]

alexfh wrote:

Here is the test that fails after this patch: https://github.com/google/highway/blob/master/hwy/tests/div_test.cc

The failure looks like this:
```
[ RUN      ] HwyDivTestGroup/HwyDivTest.TestAllIntegerDiv/EMU128


u8x8 expect [2+ ->]:
  0x00,0x01,0x01,0x00,0x00,0x00,
u8x8 actual [2+ ->]:
  0x00,0x01,0x00,0x00,0x00,0x00,
Abort at div_test.cc:65: EMU128, u8x8 lane 4 mismatch: expected '0x01', got '0x00'.
```

https://github.com/llvm/llvm-project/pull/108430