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

[Florian Hahn via llvm-commits]

================
@@ -4795,9 +4783,101 @@ 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());
+  // Set of types known to not generate vector values.
+  DenseSet<Type *> WillNotWiden;
+  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 as VPInstructions model
+      // aspects not directly mapped to existing IR instructions.
+      switch (R.getVPDefID()) {
+      case VPDef::VPDerivedIVSC:
+      case VPDef::VPScalarIVStepsSC:
+      case VPDef::VPScalarCastSC:
+      case VPDef::VPReplicateSC:
+      case VPDef::VPInstructionSC:
+      case VPDef::VPCanonicalIVPHISC:
+      case VPDef::VPVectorPointerSC:
+      case VPDef::VPExpandSCEVSC:
+      case VPDef::VPEVLBasedIVPHISC:
+      case VPDef::VPPredInstPHISC:
+      case VPDef::VPBranchOnMaskSC:
+        continue;
+      case VPDef::VPReductionSC:
+      case VPDef::VPActiveLaneMaskPHISC:
+      case VPDef::VPWidenCallSC:
+      case VPDef::VPWidenCanonicalIVSC:
+      case VPDef::VPWidenCastSC:
+      case VPDef::VPWidenGEPSC:
+      case VPDef::VPWidenSC:
+      case VPDef::VPWidenSelectSC:
+      case VPDef::VPBlendSC:
+      case VPDef::VPFirstOrderRecurrencePHISC:
+      case VPDef::VPWidenPHISC:
+      case VPDef::VPWidenIntOrFpInductionSC:
+      case VPDef::VPWidenPointerInductionSC:
+      case VPDef::VPReductionPHISC:
+      case VPDef::VPInterleaveSC:
+      case VPDef::VPWidenLoadEVLSC:
+      case VPDef::VPWidenLoadSC:
+      case VPDef::VPWidenStoreEVLSC:
+      case VPDef::VPWidenStoreSC:
+        break;
+      default:
+        llvm_unreachable("unhandled recipe");
+      }
+
+      auto WillWiden = [&TTI, VF](Type *ScalarTy) {
+        Type *VectorTy = ToVectorTy(ScalarTy, VF);
+        unsigned NumLegalParts = TTI.getNumberOfParts(VectorTy);
+        if (!NumLegalParts)
+          return false;
+        if (VF.isScalable()) {
+          // <vscale x 1 x iN> is assumed to be profitable over iN because
+          // scalable registers are a distinct register class from scalar
+          // ones. If we ever find a target which wants to lower scalable
+          // vectors back to scalars, we'll need to update this code to
+          // explicitly ask TTI about the register class uses for each part.
+          return NumLegalParts <= VF.getKnownMinValue();
+        }
+        // Two or more parts that share a register - are vectorized.
+        return NumLegalParts < VF.getKnownMinValue();
+      };
+
+      // If no def nor is a store, e.g., branches, continue - no value to check.
+      if (R.getNumDefinedValues() == 0 &&
+          !isa<VPWidenStoreRecipe, VPWidenStoreEVLRecipe, VPInterleaveRecipe>(
+              &R))
+        continue;
+      // For multi-def recipes, currently only interleaved loads, suffice to
+      // check first def only.
+      // For stores check their stored value; for interleaved stores suffice
+      // the check first stored value only. In all cases this is the second
+      // operand.
+      VPValue *ToCheck =
+          R.getNumDefinedValues() >= 1 ? R.getVPValue(0) : R.getOperand(1);
+      Type *ScalarTy = TypeInfo.inferScalarType(ToCheck);
+      if (!WillNotWiden.insert({ScalarTy}).second)
----------------
fhahn wrote:

Renamed, thanks!

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