[VPlan] Update VPBranchOnMaskRecipe to always set the mask (NFC).

The mask is always available at construction time. Make it non-optional
to simlpify code.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -2503,10 +2503,7 @@ class VPReplicateRecipe : public VPRecipeWithIRFlags {
 class VPBranchOnMaskRecipe : public VPRecipeBase {
 public:
   VPBranchOnMaskRecipe(VPValue *BlockInMask)
-      : VPRecipeBase(VPDef::VPBranchOnMaskSC, {}) {
-    if (BlockInMask) // nullptr means all-one mask.
-      addOperand(BlockInMask);
-  }
+      : VPRecipeBase(VPDef::VPBranchOnMaskSC, {BlockInMask}) {}
 
   VPBranchOnMaskRecipe *clone() override {
     return new VPBranchOnMaskRecipe(getOperand(0));
@@ -2527,21 +2524,10 @@ class VPBranchOnMaskRecipe : public VPRecipeBase {
   void print(raw_ostream &O, const Twine &Indent,
              VPSlotTracker &SlotTracker) const override {
     O << Indent << "BRANCH-ON-MASK ";
-    if (VPValue *Mask = getMask())
-      Mask->printAsOperand(O, SlotTracker);
-    else
-      O << " All-One";
+    printOperands(O, SlotTracker);
   }
 #endif
 
-  /// Return the mask used by this recipe. Note that a full mask is represented
-  /// by a nullptr.
-  VPValue *getMask() const {
-    assert(getNumOperands() <= 1 && "should have either 0 or 1 operands");
-    // Mask is optional.
-    return getNumOperands() == 1 ? getOperand(0) : nullptr;
-  }
-
   /// Returns true if the recipe uses scalars of operand \p Op.
   bool usesScalars(const VPValue *Op) const override {
     assert(is_contained(operands(), Op) &&

llvm/lib/Transforms/Vectorize/VPlanRecipes.cpp

@@ -2471,13 +2471,8 @@ void VPScalarCastRecipe ::print(raw_ostream &O, const Twine &Indent,
 void VPBranchOnMaskRecipe::execute(VPTransformState &State) {
   assert(State.Lane && "Branch on Mask works only on single instance.");
 
-
-  Value *ConditionBit = nullptr;
-  VPValue *BlockInMask = getMask();
-  if (BlockInMask)
-    ConditionBit = State.get(BlockInMask, *State.Lane);
-  else // Block in mask is all-one.
-    ConditionBit = State.Builder.getTrue();
+  VPValue *BlockInMask = getOperand(0);
+  Value *ConditionBit = State.get(BlockInMask, *State.Lane);
 
   // Replace the temporary unreachable terminator with a new conditional branch,
   // whose two destinations will be set later when they are created.