write parts of a README

README.md

@@ -1,6 +1,26 @@
 # xDSL
 
-TODO
+## Testing
+
+xDSL includes pytest unit test and llvm-style filecheck tests. They can be executed using to following commands from within the root directory of the project:
+
+```
+# Executes pytests which are located in tests/
+pytest
+
+# Executes filecheck tests
+lit test/filecheck
+```
+
+## Generating executables through MLIR
+
+xDSL can generate executables using MLIR as the backend. To use this functionality, make sure to install the [MLIR Python Bindings](https://mlir.llvm.org/docs/Bindings/Python/). Given an input file `input.xdsl`, that contains IR with only the mirrored dialects found in `src/xdsl/dialects` (arith, memref, func, cf, scf, and builtin), run:
+
+```
+mlir-opt --convert-scf-to-cf --convert-cf-to-llvm --convert-func-to-llvm --convert-arith-to-llvm --convert-memref-to-llvm --reconcile-unrealized-casts *input.xdsl* | mlir-translate --mlir-to-llvmir > tmp.ll
+```
+
+The generated `tmp.ll` file contains LLVMIR, so it can be directly passed to a compiler like clang.
 
 ## Formatting