[VPlan] Always create initial blocks in constructor (NFC).

Update C++ unit tests to use VPlanTestBase to construct initial VPlan,
using a constructor that creates the VP blocks directly in the
constructor.

Split off from and in preparation for
#120918.

llvm/lib/Transforms/Vectorize/VPlan.h

@@ -3863,7 +3863,6 @@ class VPlan {
   /// been modeled in VPlan directly.
   DenseMap<const SCEV *, VPValue *> SCEVToExpansion;
 
-public:
   /// Construct a VPlan with \p Entry to the plan and with \p ScalarHeader
   /// wrapping the original header of the scalar loop.
   VPlan(VPBasicBlock *Entry, VPIRBasicBlock *ScalarHeader)
@@ -3873,18 +3872,20 @@ class VPlan {
            "scalar header must be a leaf node");
   }
 
-  /// Construct a VPlan with \p Entry entering the plan, trip count \p TC and
-  /// with \p ScalarHeader wrapping the original header of the scalar loop.
-  VPlan(VPBasicBlock *Entry, VPValue *TC, VPIRBasicBlock *ScalarHeader)
-      : VPlan(Entry, ScalarHeader) {
-    TripCount = TC;
-  }
-
+public:
   /// Construct a VPlan for \p L. This will create VPIRBasicBlocks wrapping the
   /// original preheader and scalar header of \p L, to be used as entry and
   /// scalar header blocks of the new VPlan.
   VPlan(Loop *L);
 
+  /// Construct a VPlan with a new VPBasicBlock as entry, a VPIRBasicBlock
+  /// wrapping \p ScalarHeaderBB and a trip count of \p TC.
+  VPlan(BasicBlock *ScalarHeaderBB, VPValue *TC) {
+    setEntry(new VPBasicBlock("preheader"));
+    ScalarHeader = VPIRBasicBlock::fromBasicBlock(ScalarHeaderBB);
+    TripCount = TC;
+  }
+
   ~VPlan();
 
   void setEntry(VPBasicBlock *VPBB) {

llvm/lib/Transforms/Vectorize/VPlanHCFGBuilder.h

@@ -32,11 +32,11 @@ class Loop;
 class LoopInfo;
 class VPRegionBlock;
 class VPlan;
-class VPlanTestBase;
+class VPlanTestIRBase;
 
 /// Main class to build the VPlan H-CFG for an incoming IR.
 class VPlanHCFGBuilder {
-  friend VPlanTestBase;
+  friend VPlanTestIRBase;
 
 private:
   // The outermost loop of the input loop nest considered for vectorization.

llvm/unittests/Transforms/Vectorize/VPDomTreeTest.cpp

@@ -9,12 +9,15 @@
 
 #include "../lib/Transforms/Vectorize/VPlan.h"
 #include "../lib/Transforms/Vectorize/VPlanDominatorTree.h"
+#include "VPlanTestBase.h"
 #include "gtest/gtest.h"
 
 namespace llvm {
 namespace {
 
-TEST(VPDominatorTreeTest, DominanceNoRegionsTest) {
+using VPDominatorTreeTest = VPlanTestBase;
+
+TEST_F(VPDominatorTreeTest, DominanceNoRegionsTest) {
   //   VPBB0
   //    |
   //   R1 {
@@ -24,8 +27,8 @@ TEST(VPDominatorTreeTest, DominanceNoRegionsTest) {
   //    \    /
   //    VPBB4
   //  }
-  VPBasicBlock *VPPH = new VPBasicBlock("ph");
-  VPBasicBlock *VPBB0 = new VPBasicBlock("VPBB0");
+  VPlan &Plan = getPlan();
+  VPBasicBlock *VPBB0 = Plan.getEntry();
   VPBasicBlock *VPBB1 = new VPBasicBlock("VPBB1");
   VPBasicBlock *VPBB2 = new VPBasicBlock("VPBB2");
   VPBasicBlock *VPBB3 = new VPBasicBlock("VPBB3");
@@ -40,12 +43,7 @@ TEST(VPDominatorTreeTest, DominanceNoRegionsTest) {
   VPBlockUtils::connectBlocks(VPBB2, VPBB4);
   VPBlockUtils::connectBlocks(VPBB3, VPBB4);
 
-  LLVMContext C;
-  auto *ScalarHeader = BasicBlock::Create(C, "");
-  VPIRBasicBlock *ScalarHeaderVPBB = new VPIRBasicBlock(ScalarHeader);
-  VPBlockUtils::connectBlocks(R1, ScalarHeaderVPBB);
-  VPBlockUtils::connectBlocks(VPPH, VPBB0);
-  VPlan Plan(VPPH, ScalarHeaderVPBB);
+  VPBlockUtils::connectBlocks(R1, Plan.getScalarHeader());
 
   VPDominatorTree VPDT;
   VPDT.recalculate(Plan);
@@ -62,7 +60,6 @@ TEST(VPDominatorTreeTest, DominanceNoRegionsTest) {
   EXPECT_EQ(VPDT.findNearestCommonDominator(VPBB2, VPBB3), VPBB1);
   EXPECT_EQ(VPDT.findNearestCommonDominator(VPBB2, VPBB4), VPBB1);
   EXPECT_EQ(VPDT.findNearestCommonDominator(VPBB4, VPBB4), VPBB4);
-  delete ScalarHeader;
 }
 
 static void
@@ -76,9 +73,7 @@ checkDomChildren(VPDominatorTree &VPDT, VPBlockBase *Src,
   EXPECT_EQ(Children, ExpectedNodes);
 }
 
-TEST(VPDominatorTreeTest, DominanceRegionsTest) {
-  LLVMContext C;
-  auto *ScalarHeader = BasicBlock::Create(C, "");
+TEST_F(VPDominatorTreeTest, DominanceRegionsTest) {
   {
     // 2 consecutive regions.
     // VPBB0
@@ -99,8 +94,8 @@ TEST(VPDominatorTreeTest, DominanceRegionsTest) {
     //    R2BB2
     // }
     //
-    VPBasicBlock *VPPH = new VPBasicBlock("ph");
-    VPBasicBlock *VPBB0 = new VPBasicBlock("VPBB0");
+    VPlan &Plan = getPlan();
+    VPBasicBlock *VPBB0 = Plan.getEntry();
     VPBasicBlock *R1BB1 = new VPBasicBlock();
     VPBasicBlock *R1BB2 = new VPBasicBlock();
     VPBasicBlock *R1BB3 = new VPBasicBlock();
@@ -122,10 +117,7 @@ TEST(VPDominatorTreeTest, DominanceRegionsTest) {
     VPBlockUtils::connectBlocks(R2BB1, R2BB2);
     VPBlockUtils::connectBlocks(R1, R2);
 
-    VPIRBasicBlock *ScalarHeaderVPBB = new VPIRBasicBlock(ScalarHeader);
-    VPBlockUtils::connectBlocks(R2, ScalarHeaderVPBB);
-    VPBlockUtils::connectBlocks(VPPH, VPBB0);
-    VPlan Plan(VPPH, ScalarHeaderVPBB);
+    VPBlockUtils::connectBlocks(R2, Plan.getScalarHeader());
     VPDominatorTree VPDT;
     VPDT.recalculate(Plan);
 
@@ -177,7 +169,7 @@ TEST(VPDominatorTreeTest, DominanceRegionsTest) {
     //   |
     //  VPBB2
     //
-    VPBasicBlock *VPPH = new VPBasicBlock("ph");
+    VPlan &Plan = getPlan();
     VPBasicBlock *R1BB1 = new VPBasicBlock("R1BB1");
     VPBasicBlock *R1BB2 = new VPBasicBlock("R1BB2");
     VPBasicBlock *R1BB3 = new VPBasicBlock("R1BB3");
@@ -199,15 +191,12 @@ TEST(VPDominatorTreeTest, DominanceRegionsTest) {
     VPBlockUtils::connectBlocks(R1BB2, R1BB3);
     VPBlockUtils::connectBlocks(R2, R1BB3);
 
-    VPBasicBlock *VPBB1 = new VPBasicBlock("VPBB1");
+    VPBasicBlock *VPBB1 = Plan.getEntry();
     VPBlockUtils::connectBlocks(VPBB1, R1);
     VPBasicBlock *VPBB2 = new VPBasicBlock("VPBB2");
     VPBlockUtils::connectBlocks(R1, VPBB2);
 
-    VPIRBasicBlock *ScalarHeaderVPBB = new VPIRBasicBlock(ScalarHeader);
-    VPBlockUtils::connectBlocks(VPBB2, ScalarHeaderVPBB);
-    VPBlockUtils::connectBlocks(VPPH, VPBB1);
-    VPlan Plan(VPPH, ScalarHeaderVPBB);
+    VPBlockUtils::connectBlocks(VPBB2, Plan.getScalarHeader());
     VPDominatorTree VPDT;
     VPDT.recalculate(Plan);
 
@@ -220,9 +209,8 @@ TEST(VPDominatorTreeTest, DominanceRegionsTest) {
     checkDomChildren(VPDT, R2BB2, {R2BB3});
     checkDomChildren(VPDT, R2BB3, {});
     checkDomChildren(VPDT, R1BB3, {VPBB2});
-    checkDomChildren(VPDT, VPBB2, {ScalarHeaderVPBB});
+    checkDomChildren(VPDT, VPBB2, {Plan.getScalarHeader()});
   }
-  delete ScalarHeader;
 }
 
 } // namespace

llvm/unittests/Transforms/Vectorize/VPlanHCFGTest.cpp

@@ -17,7 +17,7 @@
 namespace llvm {
 namespace {
 
-class VPlanHCFGTest : public VPlanTestBase {};
+class VPlanHCFGTest : public VPlanTestIRBase {};
 
 TEST_F(VPlanHCFGTest, testBuildHCFGInnerLoop) {
   const char *ModuleString =

llvm/unittests/Transforms/Vectorize/VPlanSlpTest.cpp

@@ -16,7 +16,7 @@
 namespace llvm {
 namespace {
 
-class VPlanSlpTest : public VPlanTestBase {
+class VPlanSlpTest : public VPlanTestIRBase {
 protected:
   TargetLibraryInfoImpl TLII;
   TargetLibraryInfo TLI;