[VPlan] Get opcode & type from recipe in adjustRecipesForReduction (NFC)

Replace direct access to underlying IR instructions with VPlan-level
equivalents, i.e. VPTypeAnalysis and pattern matching on the recipe.

Removes a few uses of accessing underlying IR.

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -8621,6 +8621,7 @@ VPlanPtr LoopVectorizationPlanner::tryToBuildVPlan(VFRange &Range) {
 void LoopVectorizationPlanner::adjustRecipesForReductions(
     VPlanPtr &Plan, VPRecipeBuilder &RecipeBuilder, ElementCount MinVF) {
   using namespace VPlanPatternMatch;
+  VPTypeAnalysis TypeInfo(*Plan);
   VPRegionBlock *VectorLoopRegion = Plan->getVectorLoopRegion();
   VPBasicBlock *Header = VectorLoopRegion->getEntryBasicBlock();
   VPBasicBlock *MiddleVPBB = Plan->getMiddleBlock();
@@ -8705,8 +8706,8 @@ void LoopVectorizationPlanner::adjustRecipesForReductions(
         LinkVPBB->insert(FMulRecipe, CurrentLink->getIterator());
         VecOp = FMulRecipe;
       } else if (PhiR->isInLoop() && Kind == RecurKind::AddChainWithSubs &&
-                 CurrentLinkI->getOpcode() == Instruction::Sub) {
-        Type *PhiTy = PhiR->getUnderlyingValue()->getType();
+                 match(CurrentLink, m_Sub(m_VPValue(), m_VPValue()))) {
+        Type *PhiTy = TypeInfo.inferScalarType(PhiR);
         auto *Zero = Plan->getConstantInt(PhiTy, 0);
         VPWidenRecipe *Sub = new VPWidenRecipe(
             Instruction::Sub, {Zero, CurrentLink->getOperand(1)}, {},
@@ -8782,7 +8783,7 @@ void LoopVectorizationPlanner::adjustRecipesForReductions(
 
     const RecurrenceDescriptor &RdxDesc = Legal->getRecurrenceDescriptor(
         cast<PHINode>(PhiR->getUnderlyingInstr()));
-    Type *PhiTy = PhiR->getUnderlyingValue()->getType();
+    Type *PhiTy = TypeInfo.inferScalarType(PhiR);
     // If tail is folded by masking, introduce selects between the phi
     // and the users outside the vector region of each reduction, at the
     // beginning of the dedicated latch block.