[VPlan] Don't print VPlan DT after VPlan construction. (NFC)

Remove unnecessary code to just print VPlan dominator tree.

Author: fhahn

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -58,6 +58,7 @@
 #include "VPRecipeBuilder.h"
 #include "VPlan.h"
 #include "VPlanAnalysis.h"
+#include "VPlanCFG.h"
 #include "VPlanHCFGBuilder.h"
 #include "VPlanHelpers.h"
 #include "VPlanPatternMatch.h"

llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.cpp

@@ -496,9 +496,4 @@ void VPlanHCFGBuilder::buildHierarchicalCFG() {
   // Build Top Region enclosing the plain CFG.
   buildPlainCFG();
   LLVM_DEBUG(Plan.setName("HCFGBuilder: Plain CFG\n"); dbgs() << Plan);
-
-  // Compute plain CFG dom tree for VPLInfo.
-  VPDomTree.recalculate(Plan);
-  LLVM_DEBUG(dbgs() << "Dominator Tree after building the plain CFG.\n";
-             VPDomTree.print(dbgs()));
 }

llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.h

@@ -24,7 +24,7 @@
 #ifndef LLVM_TRANSFORMS_VECTORIZE_VPLAN_VPLANHCFGBUILDER_H
 #define LLVM_TRANSFORMS_VECTORIZE_VPLAN_VPLANHCFGBUILDER_H
 
-#include "VPlanDominatorTree.h"
+#include "llvm/ADT/DenseMap.h"
 
 namespace llvm {
 
@@ -33,6 +33,8 @@ class LoopInfo;
 class VPRegionBlock;
 class VPlan;
 class VPlanTestIRBase;
+class VPBlockBase;
+class BasicBlock;
 
 /// Main class to build the VPlan H-CFG for an incoming IR.
 class VPlanHCFGBuilder {
@@ -48,11 +50,6 @@ class VPlanHCFGBuilder {
   // The VPlan that will contain the H-CFG we are building.
   VPlan &Plan;
 
-  // Dominator analysis for VPlan plain CFG to be used in the
-  // construction of the H-CFG. This analysis is no longer valid once regions
-  // are introduced.
-  VPDominatorTree VPDomTree;
-
   /// Map of create VP blocks to their input IR basic blocks, if they have been
   /// created for a input IR basic block.
   DenseMap<VPBlockBase *, BasicBlock *> VPB2IRBB;

llvm/unittests/Transforms/Vectorize/VPlanVerifierTest.cpp

@@ -8,6 +8,7 @@
 
 #include "../lib/Transforms/Vectorize/VPlanVerifier.h"
 #include "../lib/Transforms/Vectorize/VPlan.h"
+#include "../lib/Transforms/Vectorize/VPlanCFG.h"
 #include "VPlanTestBase.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"