Recalculate VPDT in VPlan::execute

Author: Mel-Chen

llvm/lib/Transforms/Vectorize/VPlan.cpp

@@ -983,6 +983,10 @@ void VPlan::execute(VPTransformState *State) {
   State->CFG.PrevVPBB = nullptr;
   State->CFG.ExitBB = State->CFG.PrevBB->getSingleSuccessor();
 
+  // Update VPDominatorTree since VPBasicBlock may be removed after State wsa
+  // constucted.
+  State->VPDT->recalculate(*this);
+
   // Disconnect VectorPreHeader from ExitBB in both the CFG and DT.
   BasicBlock *VectorPreHeader = State->CFG.PrevBB;
   cast<BranchInst>(VectorPreHeader->getTerminator())->setSuccessor(0, nullptr);

llvm/test/Transforms/LoopVectorize/X86/epilog-vectorization-inductions.ll

@@ -137,8 +137,6 @@ define void @test_induction_step_needs_expansion(ptr noalias %j, ptr %k, i64 %l,
 ; CHECK-LABEL: @test_induction_step_needs_expansion(
 ; CHECK-NEXT:  iter.check:
 ; CHECK-NEXT:    [[TMP0:%.*]] = sub i16 0, [[OFF:%.*]]
-; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <16 x i16> poison, i16 [[TMP0]], i64 0
-; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <16 x i16> [[BROADCAST_SPLATINSERT]], <16 x i16> poison, <16 x i32> zeroinitializer
 ; CHECK-NEXT:    [[MIN_ITERS_CHECK:%.*]] = icmp ult i64 [[L:%.*]], 8
 ; CHECK-NEXT:    br i1 [[MIN_ITERS_CHECK]], label [[VEC_EPILOG_SCALAR_PH:%.*]], label [[VECTOR_MAIN_LOOP_ITER_CHECK:%.*]]
 ; CHECK:       vector.main.loop.iter.check:
@@ -149,6 +147,8 @@ define void @test_induction_step_needs_expansion(ptr noalias %j, ptr %k, i64 %l,
 ; CHECK-NEXT:    [[N_VEC:%.*]] = sub i64 [[L]], [[N_MOD_VF]]
 ; CHECK-NEXT:    [[DOTCAST:%.*]] = trunc i64 [[N_VEC]] to i16
 ; CHECK-NEXT:    [[IND_END:%.*]] = mul i16 [[DOTCAST]], [[TMP0]]
+; CHECK-NEXT:    [[BROADCAST_SPLATINSERT:%.*]] = insertelement <16 x i16> poison, i16 [[TMP0]], i64 0
+; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <16 x i16> [[BROADCAST_SPLATINSERT]], <16 x i16> poison, <16 x i32> zeroinitializer
 ; CHECK-NEXT:    [[TMP1:%.*]] = mul <16 x i16> splat (i16 16), [[TMP2]]
 ; CHECK-NEXT:    [[DOTSPLATINSERT:%.*]] = insertelement <16 x i16> poison, i16 [[TMP0]], i64 0
 ; CHECK-NEXT:    [[DOTSPLAT:%.*]] = shufflevector <16 x i16> [[DOTSPLATINSERT]], <16 x i16> poison, <16 x i32> zeroinitializer