232fb36d8f
Cretonne's encoding recipes need to have a fixed size so we can compute accurate branch destination addresses. Intel's instruction encoding has a lot of variance in the number of bytes needed to encode the opcode which leads to a number of duplicated encoding recipes that only differ in the opcode size. Add an Intel-specific TailEnc Python class which represents an abstraction over a set of recipes that are identical except for the opcode encoding. The TailEnc can then generate specific encoding recipes for each opcode format. The opcode format is a prefix of the recipe name, so for example, the 'rr' TailEnc will generate the 'Op1rr', 'Op2rr', 'Mp2rr' etc recipes. The TailEnc class provides a __call__ implementation that simply takes the sequence of opcode bytes as arguments. It then looks up the right prefix for the opcode bytes.
=======================
Cretonne Code Generator
=======================
Cretonne is a low-level retargetable code generator. It translates a
target-independent intermediate language into executable machine code.
*This is a work in progress that is not yet functional.*
.. image:: https://readthedocs.org/projects/cretonne/badge/?version=latest
:target: https://cretonne.readthedocs.io/en/latest/?badge=latest
:alt: Documentation Status
.. image:: https://travis-ci.org/stoklund/cretonne.svg?branch=master
:target: https://travis-ci.org/stoklund/cretonne
:alt: Build Status
Cretonne is designed to be a code generator for WebAssembly with these design
goals:
No undefined behavior
Cretonne does not have a `nasal demons clause <http://www.catb.org/jargon/html/N/nasal-demons.html>`_, and it won't generate code
with unexpected behavior if invariants are broken.
Portable semantics
As far as possible, Cretonne's input language has well-defined semantics
that are the same on all target architectures. The semantics are usually
the same as WebAssembly's.
Fast sandbox verification
Cretonne's input language has a safe subset for sandboxed code. No advanced
analysis is required to verify memory safety as long as only the safe
instructions are used. The safe instruction set is expressive enough to
implement WebAssembly.
Scalable performance
Cretonne can be configured to generate code as quickly as possible, or it
can generate very good code at the cost of slower compile times.
Predictable performance
When optimizing, Cretonne focuses on adapting the target-independent IL to
the quirks of the target architecture. There are no advanced optimizations
that sometimes work, sometimes fail.
Building Cretonne
-----------------
Cretonne is using the Cargo package manager format. First, ensure you have
installed a current stable rust (stable, beta, and nightly should all work, but
only stable and beta are tested consistently). Then, change the working
directory to your clone of cretonne and run::
cargo build
This will create a *target/debug* directory where you can find the generated
binary.
To build the optimized binary for release::
cargo build --release
You can then run tests with::
./test-all.sh
Building the documentation
--------------------------
To build the Cretonne documentation, you need the `Sphinx documentation
generator <http://www.sphinx-doc.org/>`_::
$ pip install sphinx sphinx-autobuild sphinx_rtd_theme
$ cd cretonne/docs
$ make html
$ open _build/html/index.html
We don't support Sphinx versions before 1.4 since the format of index tuples
has changed.