Update README.md (#9)

Add descriptions about use and consumption.

README.md

@@ -3,7 +3,7 @@
 ```
 mkdir build
 cd build
-cmake .. -DCMAKE_INSTALL_PREFIX=./install_dir
+cmake .. -DCMAKE_INSTALL_PREFIX=./install_dir -DCMAKE_BUILD_TYPE=Release
 # Use ccmake to tweak options
 make install
 ```
@@ -16,3 +16,30 @@ system, `make install` will run the whole build process unconditionally.
 ### Prerequisites
 
 * `hipcc` in `/opt/rocm/bin`, as a part of [ROCm](https://rocm.docs.amd.com/projects/install-on-linux/en/latest/)
+
+## Generation
+
+The kernel definition for generation is done in
+[rules.py](https://github.com/ROCm/aotriton/blob/main/python/rules.py). Edits
+to this file are needed for each new kernel, but it is extensible and generic.
+
+Include files can be added in
+[this](https://github.com/ROCm/aotriton/tree/main/include/aotriton) directory.
+
+The final build output is an archive object file any new project may link
+against.
+
+The archive file and header files are installed in the path specified by
+CMAKE_INSTALL_PREFIX.
+
+## Kernel Support
+
+Currently the first kernel supported is FlashAttention as based on the
+[algorithm from Tri Dao](https://github.com/Dao-AILab/flash-attention).
+
+## PyTorch Consumption
+
+PyTorch [recently](https://github.com/pytorch/pytorch/pull/121561) expanded
+AOTriton support for FlashAttention. AOTriton is consumed in PyTorch through
+the [SDPA kernels](https://github.com/pytorch/pytorch/blob/main/aten/src/ATen/native/transformers/hip/flash_attn/flash_api.hip).
+The Triton kernels and bundled archive are built at PyTorch [build time](https://github.com/pytorch/pytorch/blob/main/cmake/External/aotriton.cmake).