Author: Hakan Ardo <ha...@debian.org> Branch: extradoc Changeset: r4792:e5e0c9a46550 Date: 2012-09-12 07:53 +0200 http://bitbucket.org/pypy/extradoc/changeset/e5e0c9a46550/
Log: merge diff --git a/blog/draft/arm-status-update.rst b/blog/draft/arm-status-update.rst new file mode 100644 --- /dev/null +++ b/blog/draft/arm-status-update.rst @@ -0,0 +1,69 @@ +ARM Backend News Update +======================= + +Starting with the good news, we finally merged the ``arm-backend-2`` branch +into the main development line. As described in previous posts the main goal of +this branch was to add support for ARM processors to PyPY's JIT. As a general +byproduct the multi-architecture support should have tgo we improved several +details of PyPy to better support non-x86 architectures such as ARM and the +in-progress support for PPC64. The JIT requires an ARMv7 or newer processor +with a VFP unit targeting the ARM application Profile. These are the same +requirements as those of the Ubuntu ARM port and correspond to the hardware +used in most smartphones and development boards offered today. +The non-JIT version +might support previous architecture versions, but will be slow. + +Floating Point Support +---------------------- +The JIT backends supports floating point numbers and therefore requires a VFP +unit to be present. The **Procedure Call Standard for the ARM Architecture** +(`PDF`_) describes in the *base procedure call standard* how parameters are +passed in processor registers and on the stack when calling a function. + +When supporting floating points there are two incompatible procedure call +standards and three ways of handling floats. Usually they are referred to as +*softfp*, *soft-float* and *hard-float*. The first two use the core registers +to pass floating point arguments. The first uses a software based +float-implementation, while the second can use a floating point unit. The +latter and incompatible one requires a floating point unit and uses the +coprocessor registers to pass floating arguments to calls. A detailed +comparison can be found `here`_. + +The PyPy ARM backend currently supports the soft-float calling convention, +which is the most common one. This means that we have to copy floating point +values from the VFP to core registers and the stack when generating code for a +call that involves floating point values. Because the soft- and hard-float +calling conventions are incompatible, PyPy for ARM currently only will work on +systems built using soft-float. More and more GNU/Linux distributions for ARM +are supporting hard-float. There is almost finished support in the JIT backend +for the hard-float calling convention, but we seem to have hit an issue with +ctypes/libffi on ARM that is blocking us to run our tests against the +hard-float implementation. + + +Testing and Infrastructure +-------------------------- + +By now we have an infrastructure the allows us to create cross-translated +binaries for ARM. Currently we compile binaries in a 32bit Ubuntu 12.04 +environment using scratchbox2_ to encapsulate the cross-compiler calls. The +results can be downloaded and tested from our `nightly build server`_. Some +documentation on how to cross-translate is available in the `PyPy docs`_. + +We also have some hardware to run the subset of the PyPy test-suite relevant to +the ARM-JIT backend and to run the tests suite that tests the translated ARM +binaries. The nightly tests are run on a Beagleboard-xM_ and an i.MX53_ +versatile board (kindly provided by Michael Foord), both boards running the ARM port `Ubuntu +12.04 Precise Pangolin`_. The current results for the different builders can be +seen on the `PyPy buildbot`_. As can be seen there are still some issues to be +fixed. + +.. _`PyPy buildbot`: http://buildbot.pypy.org/summary?branch=%3Ctrunk%3E&category=linux-armel +.. _`PyPy docs`: https://bitbucket.org/pypy/pypy/src/default/pypy/doc/arm.rst +.. _i.MX53: http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=IMX53QSB +.. _Beagleboard-xM: http://beagleboard.org/hardware-xm +.. _`Ubuntu 12.04 Precise Pangolin`: https://wiki.ubuntu.com/ARM +.. _`scratchbox2`: http://maemo.gitorious.org/scratchbox2 +.. _`nightly build server`: http://buildbot.pypy.org/nightly/trunk/ +.. _`PDF`: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0042d/IHI0042D_aapcs.pdf +.. _`here`: http://wiki.debian.org/ArmHardFloatPort/VfpComparison _______________________________________________ pypy-commit mailing list pypy-commit@python.org http://mail.python.org/mailman/listinfo/pypy-commit
