Backends
========

BearVM supports four execution modes. All of them take the same ``.bear``
source file as input.

Interpreter
-----------

The default mode. No external dependencies required::

    bear <file.bear>

The interpreter surpasses Lua in terms of performance for general workloads.

QBE
---

Emits QBE IR::

    bear qbe <file.bear>

Compiles to a native binary via QBE and ``cc``::

    bear qbe <file.bear> -c

Requires QBE to be installed and available on ``PATH``. The ``-c`` flag
additionally requires a C compiler (``cc``).

LLVM
----

Emits LLVM IR::

    bear llvm <file.bear>

Compiles to a native binary via ``llc`` and ``cc``::

    bear llvm <file.bear> -c

Requires LLVM to be installed and ``llc`` to be available on ``PATH``. The
``-c`` flag additionally requires a C compiler (``cc``).

JIT
---

Compiles and runs directly using an experimental aarch64 code generator::

    bear jit <file.bear>

**This backend is only available on Apple Silicon (aarch64 macOS).** It will
not function on other platforms or architectures. There are no current plans
to extend JIT support to additional targets.

Installing QBE
--------------

QBE is available at https://c9x.me/compile/. On macOS it can be installed
via Homebrew::

    brew install qbe

On Linux, build from source or check your distribution's package manager.

Installing LLVM
---------------

LLVM packages are available at https://llvm.org/. On macOS::

    brew install llvm

On Linux, most distributions ship LLVM packages. Ensure ``llc`` is on your
``PATH`` after installation.