[llvm] [LV] Move check if any vector insts will be generated to VPlan. (PR #96622)

[via llvm-commits]

================
@@ -4795,9 +4783,92 @@ static void emitInvalidCostRemarks(SmallVector<InstructionVFPair> InvalidCosts,
   } while (!Tail.empty());
 }
 
+static bool willGenerateVectorInstructions(VPlan &Plan, ElementCount VF,
----------------
ayalz wrote:

```suggestion
/// Check if any recipe of \p Plan will generate a vector value, which will be assigned a vector register.
static bool willGenerateVectorRegisters(VPlan &Plan, ElementCount VF,
```
or `willGenerateVectors` - this not only looks for recipes that will widen, producing vector IR instructions, but also that the vector values they produce will end up utilizing vector registers.

https://github.com/llvm/llvm-project/pull/96622