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

[via llvm-commits]

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@@ -4795,9 +4783,98 @@ static void emitInvalidCostRemarks(SmallVector<InstructionVFPair> InvalidCosts,
   } while (!Tail.empty());
 }
 
+/// Check if any recipe of \p Plan will generate a vector value, which will be
+/// assigned a vector register.
+static bool willGenerateVectors(VPlan &Plan, ElementCount VF,
+                                const TargetTransformInfo &TTI) {
+  assert(VF.isVector() && "Checking a scalar VF?");
+  VPTypeAnalysis TypeInfo(Plan.getCanonicalIV()->getScalarType(),
+                          Plan.getCanonicalIV()->getScalarType()->getContext());
+  DenseMap<Type *, bool> GeneratesVector;
+  for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
+           vp_depth_first_shallow(Plan.getVectorLoopRegion()->getEntry()))) {
+    for (VPRecipeBase &R : *VPBB) {
+      // Continue early if the recipe is considered to not produce a vector
+      // result. Note that this includes VPInstruction, where some opcodes may
+      // produce a vector to preserve existing behavior originally as
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ayalz wrote:

```suggestion
      // result. Note that this includes VPInstruction where some opcodes may
      // produce a vector, to preserve existing behavior as
```

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