[LLVM] Avoid warnings when compiling getNumElements with LLVM12+ (#6738)

* [LLVM] Avoid warnings when compiling getNumElements with LLVM12+

Extract the element-count code into GetVectorNumElements and make it
compile cleanly with all LLVM versions.

* Trigger another build

src/target/llvm/codegen_llvm.cc

@@ -487,7 +487,7 @@ llvm::Value* CodeGenLLVM::CreateBroadcast(llvm::Value* value, int lanes) {
 }
 
 llvm::Value* CodeGenLLVM::CreateVecSlice(llvm::Value* vec, int begin, int extent) {
-  int num_elems = llvm::cast<llvm::VectorType>(vec->getType())->getNumElements();
+  int num_elems = GetVectorNumElements(vec);
   if (extent == num_elems && begin == 0) return vec;
   CHECK(begin >= 0 && extent <= num_elems) << "Slicing out of bound!\n";
   std::vector<llvm::Constant*> indices;
@@ -503,7 +503,7 @@ llvm::Value* CodeGenLLVM::CreateVecSlice(llvm::Value* vec, int begin, int extent
 }
 
 llvm::Value* CodeGenLLVM::CreateVecFlip(llvm::Value* vec) {
-  int num_elems = llvm::cast<llvm::VectorType>(vec->getType())->getNumElements();
+  int num_elems = GetVectorNumElements(vec);
 #if TVM_LLVM_VERSION >= 110
   std::vector<int> indices;
 #else
@@ -517,7 +517,7 @@ llvm::Value* CodeGenLLVM::CreateVecFlip(llvm::Value* vec) {
 
 llvm::Value* CodeGenLLVM::CreateVecPad(llvm::Value* vec, int target_lanes) {
   llvm::Value* mask = llvm::UndefValue::get(DTypeToLLVMType(DataType::Int(32, target_lanes)));
-  int num_elems = llvm::cast<llvm::VectorType>(vec->getType())->getNumElements();
+  int num_elems = GetVectorNumElements(vec);
   if (num_elems == target_lanes) return vec;
   CHECK_LT(num_elems, target_lanes);
   for (int i = 0; i < num_elems; ++i) {
@@ -531,15 +531,15 @@ llvm::Value* CodeGenLLVM::CreateVecConcat(std::vector<llvm::Value*> vecs) {
   int total_lanes = 0;
 
   for (llvm::Value* v : vecs) {
-    total_lanes += llvm::cast<llvm::VectorType>(v->getType())->getNumElements();
+    total_lanes += GetVectorNumElements(v);
   }
   while (vecs.size() > 1) {
     std::vector<llvm::Value*> new_vecs;
     for (size_t i = 0; i < vecs.size() - 1; i += 2) {
       llvm::Value* lhs = vecs[i];
       llvm::Value* rhs = vecs[i + 1];
-      const size_t lhs_lanes = llvm::cast<llvm::VectorType>(lhs->getType())->getNumElements();
-      const size_t rhs_lanes = llvm::cast<llvm::VectorType>(rhs->getType())->getNumElements();
+      const size_t lhs_lanes = GetVectorNumElements(lhs);
+      const size_t rhs_lanes = GetVectorNumElements(rhs);
       if (lhs_lanes < rhs_lanes) {
         lhs = CreateVecPad(lhs, rhs_lanes);
       } else if (rhs_lanes < lhs_lanes) {
@@ -843,16 +843,16 @@ llvm::Value* CodeGenLLVM::CreateIntrinsic(const CallNode* op) {
     return builder_->CreateFCmpUNO(a, a);
   } else if (op->op.same_as(builtin::vectorlow())) {
     llvm::Value* v = MakeValue(op->args[0]);
-    int l = llvm::cast<llvm::VectorType>(v->getType())->getNumElements();
+    int l = GetVectorNumElements(v);
     return CreateVecSlice(v, 0, l / 2);
   } else if (op->op.same_as(builtin::vectorhigh())) {
     llvm::Value* v = MakeValue(op->args[0]);
-    int l = llvm::cast<llvm::VectorType>(v->getType())->getNumElements();
+    int l = GetVectorNumElements(v);
     return CreateVecSlice(v, l / 2, l / 2);
   } else if (op->op.same_as(builtin::vectorcombine())) {
     llvm::Value* v0 = MakeValue(op->args[0]);
     llvm::Value* v1 = MakeValue(op->args[1]);
-    int num_elems = llvm::cast<llvm::VectorType>(v0->getType())->getNumElements() * 2;
+    int num_elems = GetVectorNumElements(v0) * 2;
 #if TVM_LLVM_VERSION >= 110
     std::vector<int> indices;
 #else

src/target/llvm/codegen_llvm.h

@@ -242,6 +242,11 @@ class CodeGenLLVM : public ExprFunctor<llvm::Value*(const PrimExpr&)>,
    */
   llvm::Function* GetIntrinsicDecl(llvm::Intrinsic::ID id, llvm::Type* ret_type,
                                    llvm::ArrayRef<llvm::Type*> arg_types);
+  /*!
+   * \brief Get the number of elements in the given vector value.
+   * \param vec The value, must be of a vector type.
+   */
+  inline int GetVectorNumElements(llvm::Value* vec);
   // initialize the function state.
   void InitFuncState();
   // Get alignment given index.
@@ -348,6 +353,15 @@ class CodeGenLLVM : public ExprFunctor<llvm::Value*(const PrimExpr&)>,
    */
   static std::unique_ptr<DebugInfo> CreateDebugInfo(llvm::Module* module);
 };
+
+inline int CodeGenLLVM::GetVectorNumElements(llvm::Value* vec) {
+#if TVM_LLVM_VERSION >= 120
+  return llvm::cast<llvm::FixedVectorType>(vec->getType())->getNumElements();
+#else
+  return llvm::cast<llvm::VectorType>(vec->getType())->getNumElements();
+#endif
+}
+
 }  // namespace codegen
 }  // namespace tvm
 #endif  // LLVM_VERSION

src/target/llvm/codegen_x86_64.cc

@@ -117,7 +117,11 @@ llvm::Value* CodeGenX86_64::CallVectorIntrin(llvm::Intrinsic::ID id, size_t intr
                                              llvm::Type* result_ty,
                                              const std::vector<llvm::Value*>& args) {
   llvm::Function* f = llvm::Intrinsic::getDeclaration(module_.get(), id, {});
+#if TVM_LLVM_VERSION >= 120
+  size_t num_elems = llvm::cast<llvm::FixedVectorType>(result_ty)->getNumElements();
+#else
   size_t num_elems = llvm::cast<llvm::VectorType>(result_ty)->getNumElements();
+#endif
   if (intrin_lanes == num_elems) {
     return builder_->CreateCall(f, args);
   }
@@ -130,7 +134,7 @@ llvm::Value* CodeGenX86_64::CallVectorIntrin(llvm::Intrinsic::ID id, size_t intr
     std::vector<llvm::Value*> split_args;
     for (const auto& v : args) {
       if (v->getType()->isVectorTy()) {
-        CHECK_EQ(llvm::cast<llvm::VectorType>(v->getType())->getNumElements(), num_elems);
+        CHECK_EQ(GetVectorNumElements(v), num_elems);
         split_args.push_back(CreateVecSlice(v, i, intrin_lanes));
       } else {
         split_args.push_back(v);