Automerge: [VPlan] Verify incoming values of VPIRPhi matches before checking (NFC)

Update the verifier to first check if the number of incoming values
matches the number of predecessors, before using
incoming_values_and_blocks. We unfortunately need also check here, as
this may be called before verifyPhiRecipes runs.

Also update the verifier unit tests, to actually fail for the expected
recipes.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp

@@ -252,6 +252,13 @@ bool VPlanVerifier::verifyVPBasicBlock(const VPBasicBlock *VPBB) {
 
       for (const VPUser *U : V->users()) {
         auto *UI = cast<VPRecipeBase>(U);
+        if (isa<VPIRPhi>(UI) &&
+            UI->getNumOperands() != UI->getParent()->getNumPredecessors()) {
+          errs() << "Phi-like recipe with different number of operands and "
+                    "predecessors.\n";
+          return false;
+        }
+
         if (auto *Phi = dyn_cast<VPPhiAccessors>(UI)) {
           for (const auto &[IncomingVPV, IncomingVPBB] :
                Phi->incoming_values_and_blocks()) {

llvm/unittests/Transforms/Vectorize/VPlanVerifierTest.cpp

@@ -326,22 +326,18 @@ TEST_F(VPVerifierTest, NonHeaderPHIInHeader) {
 
 class VPIRVerifierTest : public VPlanTestIRBase {};
 
-TEST_F(VPIRVerifierTest, testVerifyIRPhi) {
+TEST_F(VPIRVerifierTest, testVerifyIRPhiInScalarHeaderVPIRBB) {
   const char *ModuleString =
       "define void @f(ptr %A, i64 %N) {\n"
       "entry:\n"
       "  br label %loop\n"
       "loop:\n"
       "  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]\n"
-      "  %arr.idx = getelementptr inbounds i32, ptr %A, i64 %iv\n"
-      "  %l1 = load i32, ptr %arr.idx, align 4\n"
-      "  %res = add i32 %l1, 10\n"
-      "  store i32 %res, ptr %arr.idx, align 4\n"
       "  %iv.next = add i64 %iv, 1\n"
       "  %exitcond = icmp ne i64 %iv.next, %N\n"
       "  br i1 %exitcond, label %loop, label %for.end\n"
       "for.end:\n"
-      "  %p = phi i32 [ %l1, %loop ]\n"
+      "  %p = phi i64 [ %iv, %loop ]\n"
       "  ret void\n"
       "}\n";
 
@@ -351,7 +347,48 @@ TEST_F(VPIRVerifierTest, testVerifyIRPhi) {
   BasicBlock *LoopHeader = F->getEntryBlock().getSingleSuccessor();
   auto Plan = buildVPlan(LoopHeader);
 
-  Plan->getExitBlocks()[0]->front().addOperand(Plan->getConstantInt(32, 0));
+#if GTEST_HAS_STREAM_REDIRECTION
+  ::testing::internal::CaptureStderr();
+#endif
+  EXPECT_FALSE(verifyVPlanIsValid(*Plan));
+#if GTEST_HAS_STREAM_REDIRECTION
+  EXPECT_STREQ(
+      "Phi-like recipe with different number of operands and predecessors.\n",
+      ::testing::internal::GetCapturedStderr().c_str());
+#endif
+}
+
+TEST_F(VPIRVerifierTest, testVerifyIRPhiInExitVPIRBB) {
+  const char *ModuleString =
+      "define void @f(ptr %A, i64 %N) {\n"
+      "entry:\n"
+      "  br label %loop\n"
+      "loop:\n"
+      "  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]\n"
+      "  %iv.next = add i64 %iv, 1\n"
+      "  %exitcond = icmp ne i64 %iv.next, %N\n"
+      "  br i1 %exitcond, label %loop, label %for.end\n"
+      "for.end:\n"
+      "  %p = phi i64 [ %iv, %loop ]\n"
+      "  ret void\n"
+      "}\n";
+
+  Module &M = parseModule(ModuleString);
+
+  Function *F = M.getFunction("f");
+  BasicBlock *LoopHeader = F->getEntryBlock().getSingleSuccessor();
+  auto Plan = buildVPlan(LoopHeader);
+
+  // Create a definition in the vector loop header that will be used by the phi.
+  auto *HeaderBlock =
+      cast<VPBasicBlock>(Plan->getVectorLoopRegion()->getEntry());
+  VPInstruction *DefI =
+      new VPInstruction(VPInstruction::ExtractLastElement,
+                        {HeaderBlock->front().getVPSingleValue()});
+  DefI->insertBefore(Plan->getMiddleBlock()->getTerminator());
+  Plan->getExitBlocks()[0]->front().addOperand(DefI);
+  VPValue *Zero = Plan->getConstantInt(32, 0);
+  Plan->getScalarHeader()->front().addOperand(Zero);
 
 #if GTEST_HAS_STREAM_REDIRECTION
   ::testing::internal::CaptureStderr();