6b4c28d554
Most of the time, register coloring is almost trivial: just pick available registers for the values defined by the current instruction. However, some instructions have register operand constraints, and it may be necessary to move live registers around to satisfy the constraints. Sometimes the instruction's own operands can interfere with each other in a way that you can't just pick a register assignment for each output in order. This is complicated enough that it is worthwhile to represent as a constraint satisfaction problem in a separate solver module. The representation is chosen to be very fast in the common case where the constraints are trivial to solve. The current implementation is still incomplete, but as functional as the code it's replacing. Missing features: - Handle tied operand constraints. - Handle ABI constraints on calls and return instructions. - Execute a constraint solution by emitting regmove instructions. - Handling register diversions before leaving the EBB.
=======================
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.