91343f208d
The ir::layout module is assigning sequence numbers to all EBBs and instructions so relative positions can be computed in constant time. This works a lot like BASIC line numbers where we initially use numbers 10, 20, 30, ... so we can insert new instructions in the middle of the sequence without renumbering everything. In some cases where the coalescer is misbehaving and inserting a lot of copy instructions, we end up having to renumber a larger and larger number of instructions to make space in the sequence. This causes the following reload pass to be very slow, spending most of its time renumbering instructions. Fix this by putting an upper limit on the number of instructions we're willing to renumber locally. When the limit is reached, switch to a full function renumbering with the major stride of 10. This gives us new elasticity in the sequence numbers. - Time to compile the Python interpreter in #229 drops from 4826 s -> 15.8 s. - The godot benchmark in #226 drops from 1257 s -> 75 s. - The AngryBots1 benchmark does not have the coalescer misbehavior. Its compilation time changes 22.9 s -> 23.1 s. It's worth noting that the sequence numbering is still technically quadratic with this fix. The system is not designed to handle a large number of instructions inserted in a single location. It expects a more even distribution of new instructions. We still need to fix the coalescer. It should not insert so many copies in degenerate cases.
=======================
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:
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
subset is used. The safe subset 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.
For more information, see
`the documentation <https://cretonne.readthedocs.io/en/latest/?badge=latest>`_.
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
You may need to install the *wat2wasm* tool from the `wabt
<https://github.com/WebAssembly/wabt>`_ project in order to run all of the
WebAssembly tests. Tests requiring wat2wasm are ignored if the tool is not
installed.
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.