!fixup address latest comments, thanks

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -1095,17 +1095,17 @@ template <typename RecipeTy> class VPPhiAccessors {
   }
 
 public:
-  /// Returns the \p I th incoming VPValue.
-  VPValue *getIncomingValue(unsigned I) const {
-    return getAsRecipe()->getOperand(I);
+  /// Returns the incoming VPValue with index \p Idx.
+  VPValue *getIncomingValue(unsigned Idx) const {
+    return getAsRecipe()->getOperand(Idx);
   }
 
   /// Returns an interator range over the incoming values
   VPUser::const_operand_range incoming_values() const {
     return getAsRecipe()->operands();
   }
 
-  /// Returns the \p I th incoming block.
+  /// Returns the incoming block with index \p Idx.
   const VPBasicBlock *getIncomingBlock(unsigned Idx) const;
 
   using const_incoming_block_iterator =
@@ -1121,10 +1121,7 @@ template <typename RecipeTy> class VPPhiAccessors {
   }
   const_incoming_block_iterator incoming_block_end() const {
     return const_incoming_block_iterator(
-        detail::index_iterator(getAsRecipe()->getVPDefID() ==
-                                       VPDef::VPWidenIntOrFpInductionSC
-                                   ? 2
-                                   : getAsRecipe()->getNumOperands()),
+        detail::index_iterator(getAsRecipe()->getNumOperands()),
         [this](size_t Idx) { return getIncomingBlock(Idx); });
   }
 
@@ -1133,7 +1130,7 @@ template <typename RecipeTy> class VPPhiAccessors {
     return make_range(incoming_block_begin(), incoming_block_end());
   }
 
-  /// Returns an iterator range over pairs of incoming values and corrsponding
+  /// Returns an iterator range over pairs of incoming values and correspondingx
   /// incoming blocks.
   detail::zippy<llvm::detail::zip_shortest, VPUser::const_operand_range,
                 const_incoming_blocks_range>

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -1042,24 +1042,27 @@ void VPIRInstruction::print(raw_ostream &O, const Twine &Indent,
 }
 #endif
 
+/// Returns the incoming block at index \p Idx for \p R. This handles both
+/// recipes placed in entry blocks of loop regions (incoming blocks are the
+/// region's predecessor and the region's exit) and other locations (incoming
+/// blocks are the direct predecessors).
 static const VPBasicBlock *getIncomingBlockForRecipe(const VPRecipeBase *R,
-                                                     unsigned I) {
+                                                     unsigned Idx) {
   const VPBasicBlock *Parent = R->getParent();
   const VPBlockBase *Pred = nullptr;
   if (Parent->getNumPredecessors() > 0) {
-    Pred = Parent->getPredecessors()[I];
+    Pred = Parent->getPredecessors()[Idx];
   } else {
     auto *Region = Parent->getParent();
     assert(Region && !Region->isReplicator() && Region->getEntry() == Parent &&
            "must be in the entry block of a non-replicate region");
     assert(
-        I < 2 &&
-        (R->getNumOperands() == 2 || isa<VPWidenIntOrFpInductionRecipe>(R)) &&
+        Idx < 2 && R->getNumOperands() == 2 &&
         "when placed in an entry block, only 2 incoming blocks are available");
 
-    // I ==  0 selects the predecessor of the region, I == 1 selects the region
-    // itself whose exiting block feeds the phi across the backedge.
-    Pred = I == 0 ? Region->getSinglePredecessor() : Region;
+    // Idx ==  0 selects the predecessor of the region, Idx == 1 selects the
+    // region itself whose exiting block feeds the phi across the backedge.
+    Pred = Idx == 0 ? Region->getSinglePredecessor() : Region;
   }
 
   return Pred->getExitingBasicBlock();