d64e7fb576
There are two kinds of entity maps: - A primary map is used to allocate entity references and store the primary entity data. This map only grows when adding new entities with 'push'. - A secondary map contains additional information about entities in a primary map. This map always grows with 'ensure', making default entries for any unknown primary entities. Only require the 'Default + Clone' traits for values stored in a secondary map. Also remove the 'grow automatically' feature of the IndexMut implementation. This means that clients need to call 'ensure' whenever using a potentially unknown entity reference. The 'grow automatically' feature could not be implemented for the Index trait, and it seems unfortunate to have different semantics for Index and IndexMut.
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Cretonne Code Generator
=======================
Cretonne is a low-level retargetable code generator. It translates a
target-independent intermediate language into executable machine code.
.. 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, 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, somtimes fail.
Building the documentation
--------------------------
To build the Cretonne documentation, you need the `Sphinx documentation
generator <http://www.sphinx-doc.org/>`_::
$ pip install sphinx==1.3.5 sphinx-autobuild
$ cd cretonne/docs
$ make html
$ open _build/html/index.html
The specific Sphinx version is currently used by Read the Docs. Sphinx 1.4 has
been released, but produces lots of warnings about four-column indices. We'll
upgrade when Read the Docs does.