[VPlan] Fix header phi VPInstruction verification. NFC (#151472)

Noticed this when checking the invariant that all phis in the header
block must be header phis. I think there's a missing set of parentheses
here, since otherwise it only cast<VPInstruction> when RecipeI isn't a
VPInstruction.

Author: lukel97

llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp

@@ -79,9 +79,8 @@ bool VPlanVerifier::verifyPhiRecipes(const VPBasicBlock *VPBB) {
     if (isa<VPActiveLaneMaskPHIRecipe>(RecipeI))
       NumActiveLaneMaskPhiRecipes++;
 
-    if (IsHeaderVPBB && !isa<VPHeaderPHIRecipe, VPWidenPHIRecipe>(*RecipeI) &&
-        !isa<VPInstruction>(*RecipeI) &&
-        cast<VPInstruction>(RecipeI)->getOpcode() == Instruction::PHI) {
+    if (IsHeaderVPBB &&
+        !isa<VPHeaderPHIRecipe, VPWidenPHIRecipe, VPPhi>(*RecipeI)) {
       errs() << "Found non-header PHI recipe in header VPBB";
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
       errs() << ": ";

llvm/unittests/Transforms/Vectorize/VPlanVerifierTest.cpp

@@ -287,6 +287,37 @@ TEST_F(VPVerifierTest, BlockOutsideRegionWithParent) {
 #endif
 }
 
+TEST_F(VPVerifierTest, NonHeaderPHIInHeader) {
+  VPlan &Plan = getPlan();
+  VPValue *Zero = Plan.getOrAddLiveIn(ConstantInt::get(Type::getInt32Ty(C), 0));
+  auto *CanIV = new VPCanonicalIVPHIRecipe(Zero, {});
+  auto *BranchOnCond = new VPInstruction(VPInstruction::BranchOnCond, {CanIV});
+
+  VPBasicBlock *VPBB1 = Plan.getEntry();
+  VPBasicBlock *VPBB2 = Plan.createVPBasicBlock("header");
+
+  VPBB2->appendRecipe(CanIV);
+
+  PHINode *PHINode = PHINode::Create(Type::getInt32Ty(C), 2);
+  auto *IRPhi = new VPIRPhi(*PHINode);
+  VPBB2->appendRecipe(IRPhi);
+  VPBB2->appendRecipe(BranchOnCond);
+
+  VPRegionBlock *R1 = Plan.createVPRegionBlock(VPBB2, VPBB2, "R1");
+  VPBlockUtils::connectBlocks(VPBB1, R1);
+  VPBlockUtils::connectBlocks(R1, Plan.getScalarHeader());
+
+#if GTEST_HAS_STREAM_REDIRECTION
+  ::testing::internal::CaptureStderr();
+#endif
+  EXPECT_FALSE(verifyVPlanIsValid(Plan));
+#if GTEST_HAS_STREAM_REDIRECTION
+  EXPECT_STREQ(
+      "Found non-header PHI recipe in header VPBB: IR   <badref> = phi i32 \n",
+      ::testing::internal::GetCapturedStderr().c_str());
+#endif
+}
+
 class VPIRVerifierTest : public VPlanTestIRBase {};
 
 TEST_F(VPIRVerifierTest, testVerifyIRPhi) {