add minimum documentation

README.md

@@ -1,2 +1,66 @@
 # ONNF
-Open Neural Network Frontend
+Open Neural Network Frontend : an ONNX frontend to MLIR.
+
+[![CircleCI](https://circleci.com/gh/clang-ykt/ONNF.svg?style=svg)](https://circleci.com/gh/clang-ykt/ONNF)
+
+## Installation
+
+We assume an existing installation of MLIR. The LLVM-Project repo commit hash we used to test against is 9b6ad8466bb8b97082b705270603ad7f4559e931 and the MLIR repo commit hash we used is 0710266d0f56cf6ab0f437badbd7416b6cecdf5f. 
+
+Two environment variables need to be set:
+- LLVM_SRC should point to the llvm src directory (e.g., llvm-project/llvm).
+- LLVM_BUILD should point to the llvm build directory (e.g., llvm-project/build).
+
+To build ONNF, use the following command:
+```
+git clone --recursive git@github.com:clang-ykt/ONNF.git
+mkdir build
+cd build
+cmake ..
+cmake --build . --target all
+```
+
+After the above commands succeed, an `onnf` executable should appear in the `bin` directory. 
+
+## Using ONNF
+
+The usage of `onnf` is as such:
+```
+OVERVIEW: ONNF MLIR modular optimizer driver
+
+USAGE: onnf [options] <input file>
+
+OPTIONS:
+
+Generic Options:
+
+  --help        - Display available options (--help-hidden for more)
+  --help-list   - Display list of available options (--help-list-hidden for more)
+  --version     - Display the version of this program
+
+ONNF Options:
+These are frontend options.
+
+  Choose target to emit:
+      --EmitONNXIR - Ingest ONNX and emit corresponding ONNX dialect.
+      --EmitMLIR   - Lower model to MLIR built-in transformation dialect.
+      --EmitLLVMIR - Lower model to LLVM IR (LLVM dialect).
+      --EmitLLVMBC - Lower model to LLVM IR and emit (to file) LLVM bitcode for model.
+```
+
+## Example
+
+For example, to lower an ONNX model (e.g., add.onnx) to ONNX dialect, use the following command:
+```
+./onnf --EmitONNXIR add.onnx
+```
+The output should look like:
+```
+module {
+  func @main_graph(%arg0: tensor<10x10x10xf32>, %arg1: tensor<10x10x10xf32>) -> tensor<10x10x10xf32> {
+    %0 = "onnx.Add"(%arg0, %arg1) : (tensor<10x10x10xf32>, tensor<10x10x10xf32>) -> tensor<10x10x10xf32>
+    return %0 : tensor<10x10x10xf32>
+  }
+}
+```
+