Revert "[VPlan] Support cloning initial VPlan (NFC)."

This reverts commit 5fa985e.

Revert as this seems to introduce a call to a pure virtual function on a
few configs, e.g.
    https://lab.llvm.org/buildbot/#/builders/169/builds/11535

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlan.cpp

@@ -1168,16 +1168,11 @@ VPlan *VPlan::duplicate() {
   const auto &[NewEntry, __] = cloneFrom(Entry);
 
   BasicBlock *ScalarHeaderIRBB = getScalarHeader()->getIRBasicBlock();
-  VPIRBasicBlock *NewScalarHeader = nullptr;
-  if (getScalarHeader()->getNumPredecessors() == 0) {
-    NewScalarHeader = createVPIRBasicBlock(ScalarHeaderIRBB);
-  } else {
-    NewScalarHeader = cast<VPIRBasicBlock>(*find_if(
-        vp_depth_first_shallow(NewEntry), [ScalarHeaderIRBB](VPBlockBase *VPB) {
-          auto *VPIRBB = dyn_cast<VPIRBasicBlock>(VPB);
-          return VPIRBB && VPIRBB->getIRBasicBlock() == ScalarHeaderIRBB;
-        }));
-  }
+  VPIRBasicBlock *NewScalarHeader = cast<VPIRBasicBlock>(*find_if(
+      vp_depth_first_shallow(NewEntry), [ScalarHeaderIRBB](VPBlockBase *VPB) {
+        auto *VPIRBB = dyn_cast<VPIRBasicBlock>(VPB);
+        return VPIRBB && VPIRBB->getIRBasicBlock() == ScalarHeaderIRBB;
+      }));
   // Create VPlan, clone live-ins and remap operands in the cloned blocks.
   auto *NewPlan = new VPlan(cast<VPBasicBlock>(NewEntry), NewScalarHeader);
   DenseMap<VPValue *, VPValue *> Old2NewVPValues;
@@ -1192,7 +1187,8 @@ VPlan *VPlan::duplicate() {
     NewPlan->BackedgeTakenCount = new VPValue();
     Old2NewVPValues[BackedgeTakenCount] = NewPlan->BackedgeTakenCount;
   }
-  if (TripCount && TripCount->isLiveIn())
+  assert(TripCount && "trip count must be set");
+  if (TripCount->isLiveIn())
     Old2NewVPValues[TripCount] =
         NewPlan->getOrAddLiveIn(TripCount->getLiveInIRValue());
   // else NewTripCount will be created and inserted into Old2NewVPValues when
@@ -1205,11 +1201,9 @@ VPlan *VPlan::duplicate() {
   NewPlan->UFs = UFs;
   // TODO: Adjust names.
   NewPlan->Name = Name;
-  if (TripCount) {
-    assert(Old2NewVPValues.contains(TripCount) &&
-           "TripCount must have been added to Old2NewVPValues");
-    NewPlan->TripCount = Old2NewVPValues[TripCount];
-  }
+  assert(Old2NewVPValues.contains(TripCount) &&
+         "TripCount must have been added to Old2NewVPValues");
+  NewPlan->TripCount = Old2NewVPValues[TripCount];
 
   // Transfer all cloned blocks (the second half of all current blocks) from
   // current to new VPlan.

llvm/unittests/Transforms/Vectorize/VPlanTest.cpp

@@ -904,47 +904,6 @@ No successors
     EXPECT_EQ(ExpectedStr, FullDump);
   }
 }
-
-TEST_F(VPBasicBlockTest, cloneAndPrint) {
-  VPlan &Plan = getPlan(nullptr);
-  VPBasicBlock *VPBB0 = Plan.getEntry();
-
-  VPInstruction *I1 = new VPInstruction(Instruction::Add, {});
-  VPInstruction *I2 = new VPInstruction(Instruction::Sub, {I1});
-  VPInstruction *I3 = new VPInstruction(Instruction::Br, {I1, I2});
-
-  VPBasicBlock *VPBB1 = Plan.createVPBasicBlock("");
-  VPBB1->appendRecipe(I1);
-  VPBB1->appendRecipe(I2);
-  VPBB1->appendRecipe(I3);
-  VPBB1->setName("bb1");
-  VPBlockUtils::connectBlocks(VPBB0, VPBB1);
-
-  const char *ExpectedStr = R"(digraph VPlan {
-graph [labelloc=t, fontsize=30; label="Vectorization Plan\n for UF\>=1\n"]
-node [shape=rect, fontname=Courier, fontsize=30]
-edge [fontname=Courier, fontsize=30]
-compound=true
-  N0 [label =
-    "preheader:\l" +
-    "Successor(s): bb1\l"
-  ]
-  N0 -> N1 [ label=""]
-  N1 [label =
-    "bb1:\l" +
-    "  EMIT vp\<%1\> = add\l" +
-    "  EMIT vp\<%2\> = sub vp\<%1\>\l" +
-    "  EMIT br vp\<%1\>, vp\<%2\>\l" +
-    "No successors\l"
-  ]
-}
-)";
-  // Check that printing a cloned plan produces the same output.
-  std::string FullDump;
-  raw_string_ostream OS(FullDump);
-  Plan.duplicate()->printDOT(OS);
-  EXPECT_EQ(ExpectedStr, FullDump);
-}
 #endif
 
 using VPRecipeTest = VPlanTestBase;