[llvm] [LV] Add LoopVectorize/VPlan subdirectory for VPlan printing tests. (PR #180611)

[David Sherwood via llvm-commits]

david-arm wrote:

Thanks for this! Seems like a good idea to me. After quick inspection I think these other vplan testing files could be moved as well:

```
LoopVectorize/conditional-scalar-assignment-vplan.ll
LoopVectorize/vplan_hcfg_stress_test.ll
LoopVectorize/icmp-uniforms.ll
LoopVectorize/RISCV/vplan-riscv-vector-reverse.ll
LoopVectorize/RISCV/vplan-vp-intrinsics-reduction.ll
LoopVectorize/RISCV/vplan-vp-intrinsics-fixed-order-recurrence.ll
LoopVectorize/AArch64/sve2-histcnt-vplan.ll
LoopVectorize/AArch64/widen-call-with-intrinsic-or-libfunc.ll
LoopVectorize/AArch64/vplan-printing.ll
LoopVectorize/AArch64/sve-tail-folding-forced.ll
LoopVectorize/PowerPC/vplan-force-tail-with-evl.ll
LoopVectorize/X86/vplan-vp-intrinsics.ll
```

Not sure if we'd want to maintain the same target hierarchy or not?

https://github.com/llvm/llvm-project/pull/180611