Author: Maciej Fijalkowski <fij...@gmail.com> Branch: extradoc Changeset: r3879:110b750a7359 Date: 2011-08-12 10:39 +0200 http://bitbucket.org/pypy/extradoc/changeset/110b750a7359/
Log: add a draft about the jitviewer diff --git a/blog/draft/jitviewer.rst b/blog/draft/jitviewer.rst new file mode 100644 --- /dev/null +++ b/blog/draft/jitviewer.rst @@ -0,0 +1,63 @@ +Visualization of JITted code +============================ + +Hello. + +We're proud to announce the first public release of the jitviewer. As of now, +jitviewer is a slightly internal tool that helps understanding how PyPy's JIT +compiles Python down all the way to assembler. If you want to give it a go, +clone the `repository`_ and look up the README. You also need both the PyPy +`source code checkout`_ and a fairly recent compiled PyPy executable, like +`a nightly`_ one. If you want to look first what does it do, check out +`the online demo`_. + +.. _`repository`: http://bitbucket.org/pypy/jitviewer +.. _`source code checkout`: http://bitbucket.org/pypy/pypy +.. _`a nightly`: http://buildbot.pypy.org/nightly/trunk/ +.. _`the online demo`: http://wyvern.cs.uni-duesseldorf.de:5000/ + +What does the jitviewer really do? +---------------------------------- + +In short - it displays how exactly the JIT has compiled python source code +into assembler in a hierarchical way. It displays four levels: + +* Python source code + +* Python bytecode, the one you would get by doing:: + + def f(a, b): + return a + b + + import dis + dis.dis(f) + + This looks like LOAD\_FAST, LOAD\_GLOBAL etc. + +* Intermediate representation of jit code (IR). This is a combination of + operations (like integer addition, reading fields out of structures) and + guards (aborting assembler if invariants are invalidated). Guards are in red. + Those operations operate on machine-level objects, like integers and memory + locations. + +* Assembler + +Sometimes you'll find that a guard fails often enough that a new piece of +assembler is required to be compiled. This is an alternative path through the +code and it's called a bridge. You can see bridges in the jitviewer when +there is a link next to a guard. For more information about purpose look up +the `jit documentation`_. + +.. _`jit documentation`: http://doc.pypy.org/en/latest/jit/index.html + +I'm still confused +------------------ + +Jitviewer is not perfect when it comes to explaining what's going on. Feel free +to pop up on IRC or send us a mail to the mailing list, we'll try to explain +and/or improve the situation. Consult the `contact`_ page for details. + +.. _`contact`: http://pypy.org/contact.html + +Cheers, +fijal _______________________________________________ pypy-commit mailing list pypy-commit@python.org http://mail.python.org/mailman/listinfo/pypy-commit
