Merge pull request #28 from spcl/Readme-Update

Update README.md

README.md

@@ -5,8 +5,26 @@ MLIR-DaCe is a project aiming to bridge the gap between control-centric and data
 By bridging these two groups of IRs, it allows the combination of control-centric and data-centric optimizations in optimization pipelines.
 In order to achieve this, MLIR-DaCe provides a data-centric dialect in MLIR to connect the MLIR and DaCe frameworks.
 
-## Building
-This setup assumes that you have built LLVM and MLIR in `$BUILD_DIR` and installed them to `$PREFIX`. To build and launch the tests, run
+## Building MLIR
+If you have already MLIR built you can skip to [Building MLIR-DaCe](#building-mlir-dace). 
+Keep in mind that there are no guarantees for commits other than the one in the submodule.
+
+First clone with submodules:
+```sh
+git clone --recurse-submodules https://github.com/spcl/mlir-dace
+cd mlir-dace
+```
+
+Then build MLIR with:
+```sh
+cd llvm-project
+mkdir build && cd build
+cmake -G Ninja ../llvm -DLLVM_ENABLE_PROJECTS="mlir" -DLLVM_TARGETS_TO_BUILD="host" -DLLVM_ENABLE_ASSERTIONS=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DLLVM_ENABLE_LLD=ON -DLLVM_INSTALL_UTILS=ON
+```
+
+## Building MLIR-DaCe
+This setup assumes that you have built LLVM and MLIR in `$BUILD_DIR` and installed them to `$PREFIX`. If you built using the directions in [Building MLIR](#building-mlir), replace both with `llvm-project/build/`.
+To build and launch the tests, run
 ```sh
 mkdir build && cd build
 cmake -G Ninja .. -DMLIR_DIR=$PREFIX/lib/cmake/mlir -DLLVM_EXTERNAL_LIT=$BUILD_DIR/bin/llvm-lit