[VPlan] Verify number preds and operands matches for VPIRPhis. (NFC)

Extend the verifier to ensure the number of predecessors and operands
match for VPIRPhis.

Author: fhahn

llvm/lib/Transforms/Vectorize/VPlanVerifier.cpp

@@ -97,6 +97,18 @@ bool VPlanVerifier::verifyPhiRecipes(const VPBasicBlock *VPBB) {
       return false;
     }
 
+    // Check if the recipe operands match the number of predecessors.
+    // TODO Extend to other phi-like recipes.
+    if (auto *PhiIRI = dyn_cast<VPIRPhi>(&*RecipeI)) {
+      if (PhiIRI->getNumOperands() != VPBB->getNumPredecessors()) {
+        errs() << "Phi-like recipe with different number of operands and "
+                  "predecessors.\n";
+        // TODO: Print broken recipe. At the moment printing an ill-formed
+        // phi-like recipe may crash.
+        return false;
+      }
+    }
+
     RecipeI++;
   }
 

llvm/unittests/Transforms/Vectorize/VPlanVerifierTest.cpp

@@ -223,4 +223,44 @@ TEST_F(VPVerifierTest, BlockOutsideRegionWithParent) {
 #endif
 }
 
+class VPIRVerifierTest : public VPlanTestIRBase {};
+
+TEST_F(VPIRVerifierTest, testVerifyIRPhi) {
+  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"
+      "  ret void\n"
+      "}\n";
+
+  Module &M = parseModule(ModuleString);
+
+  Function *F = M.getFunction("f");
+  BasicBlock *LoopHeader = F->getEntryBlock().getSingleSuccessor();
+  auto Plan = buildVPlan(LoopHeader);
+
+  Plan->getExitBlocks()[0]->front().addOperand(
+      Plan->getOrAddLiveIn(ConstantInt::get(Type::getInt32Ty(*Ctx), 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
+}
 } // namespace