Adding llvm, mlir, and tensorflow submodules.
diff --git a/.gitmodules b/.gitmodules
index 6974ad8..099cc96 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -1,6 +1,20 @@
 [submodule "third_party/abseil-cpp"]
 	path = third_party/abseil-cpp
 	url = https://github.com/abseil/abseil-cpp.git
+	shallow = true
 [submodule "third_party/googletest"]
 	path = third_party/googletest
 	url = https://github.com/google/googletest.git
+	shallow = true
+[submodule "third_party/llvm-project"]
+	path = third_party/llvm-project
+	url = https://github.com/llvm/llvm-project.git
+	shallow = true
+[submodule "third_party/mlir"]
+	path = third_party/mlir
+	url = https://github.com/tensorflow/mlir.git
+	shallow = true
+[submodule "third_party/tensorflow"]
+	path = third_party/tensorflow
+	url = https://github.com/tensorflow/tensorflow.git
+	shallow = true