add readme and license

LICENSE

@@ -0,0 +1,17 @@
+MIT License
+
+Copyright (c) 2024 Tianyu Geng
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated
+documentation files (the “Software”), to deal in the Software without restriction, including without limitation the
+rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit
+persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the
+Software.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+

README.md

@@ -0,0 +1,47 @@
+# Archon VM
+
+Low level IR and runtime for [Archon](https://github.com/tgeng/archon).
+
+## What is this?
+
+Archon is a work-in-progress experimental language that combines dependent types, algebraic effects and handlers, and
+quantitative types. Since Archon has algebraic effects and handlers, which supports multi-shot continuations, compiling
+it to machine code is not straightforward. The low level IR in this project is close enough to the core type theory of
+Archon so that compiling Archon to this low level IR should be straightforward: basically just erase unneeded
+information.
+
+## Some Design Choices
+
+* **Selective CPS transformation** Functions with complex effects (e.g. effects whose handlers may capture the
+  continuation and manipulate it) are compiled into state machines with CPS transformation. Delimited continuation is
+  then represented as a singly linked list of continuation objects. Functions that only performs simple effects (e.g.
+  `State`, `IO`, non-resumable exception) are not CPS-transformed and hence can run as fast as normal functions with
+  little additional overhead.
+* **Uniform value representation** All values have a uniform representation so that everything has the same size. That
+  is, larger values that cannot fit 8 bytes are represented as pointers. Pointers are 4 byte-aligned and the lowest two
+  bits are used to tag the value. Native integer is 63-bit because the last bit is used to tag the value as integer.
+* **Conservative GC** A conservative GC is used for simplicity of implementation and also flexibility of calling foreign
+  functions.
+* **Typeless** The low level IR has no type information and no type checking is done on it. This is because Archon is
+  already type-checked and there is no need to do type checking in low level IR again. In fact, adding type checking to
+  the low level IR is not trivial because Archon supports dependent types, which means one can easily create a function
+  whose argument can have any types.
+
+## Getting Started
+
+`cargo build` to build the project. `cargo test` to run tests.
+
+See `src/ast/term.rs` and `src/ast/signature.rs` for the low level IR. One can create a `Signature` and then compile it
+with `src/backend/compiler.rs` to machine code. Currently only ARM64 macOS is supported. Also, there is no plan to
+support 32-bit architectures.
+
+A simpler frontend IR and parser is also provided in `src/frontend/f_term.rs` and it's used in tests.
+See `resources/frontend/transpiler_tests/*.input.txt` for examples.
+
+## TODOs
+
+* Integrate Boehm's GC for memory management.
+* Support more OS/architectures.
+* Add some FFI support.
+* Add more built-in types in addition to 63-bit integers.
+* Add more built-in functions for primitive manipulations.