!fixup address latest comments, thanks

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlan.cpp

@@ -1375,7 +1375,7 @@ static bool isDefinedInsideLoopRegions(const VPValue *VPV) {
 }
 
 Type *VPValue::getType() const {
-  assert(isLiveIn());
+  assert(isLiveIn() && "can only return the type for a live-in");
   return SubclassID == VPSymbolicValueSC ? Ty : getUnderlyingValue()->getType();
 }
 

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -3454,7 +3454,7 @@ class VPlan {
   VPlan(Loop *L, Type *InductionTy);
 
   /// Construct a VPlan with a new VPBasicBlock as entry, a VPIRBasicBlock
-  /// wrapping \p ScalarHeaderBB and a trip count of \p TC.
+  /// wrapping \p ScalarHeaderBB and a trip count of \p TC. Also creates symbolic VectorTripCount, VF and VFxUF VPValues using \p InductionTy.
   VPlan(BasicBlock *ScalarHeaderBB, VPValue *TC, Type *InductionTy)
       : VectorTripCount(InductionTy), VF(InductionTy), VFxUF(InductionTy) {
     setEntry(createVPBasicBlock("preheader"));

llvm/lib/Transforms/Vectorize/VPlanValue.h

@@ -92,7 +92,7 @@ class VPValue {
 public:
   /// Return the underlying Value attached to this VPValue.
   Value *getUnderlyingValue() const {
-    return SubclassID == VPSymbolicValueSC ? nullptr : UnderlyingVal;
+    return isSymbolic() ? nullptr : UnderlyingVal;
   }
 
   /// An enumeration for keeping track of the concrete subclass of VPValue that
@@ -181,9 +181,11 @@ class VPValue {
   /// Returns true if this VPValue is a live-in, i.e. defined outside the VPlan.
   bool isLiveIn() const { return !hasDefiningRecipe(); }
 
+  /// Returns true if the VPValue is symbolic, that is a live-in without underlying value.
   bool isSymbolic() const { return SubclassID == VPSymbolicValueSC; }
 
-  Type *getType() const;
+  /// If the VPValue is a live-in, return its scalar type.
+  Type *getScalarType() const;
 
   /// Returns the underlying IR value, if this VPValue is defined outside the
   /// scope of VPlan. Returns nullptr if the VPValue is defined by a VPDef