On Mon, Jul 30, 2012 at 8:26 AM, Jon Masters <jonathan@xxxxxxxxxxxxxx> wrote:
> On 07/30/2012 03:13 AM, Peter Robinson wrote:
>> On Mon, Jul 30, 2012 at 5:23 AM, Jon Masters <jonathan@xxxxxxxxxxxxxx> wrote:
>>> Folks,
>>>
>>> In general, we probably want to look at the value of host system type
>>> being picked up for ARMv5 builds, especially on ARMv7 builder systems.
>>> Here's an example output from running an OpenMPI build on Fedora 18
>>> using the current Koji builder setup, note the "armv7l" target:
>>>
>>> --- begin quote ---
>>> checking build system type... armv7l-unknown-linux-gnueabi
>>> checking host system type... armv7l-unknown-linux-gnueabi
>>> checking target system type... armv7l-unknown-linux-gnueabi
>>> --- end quote ---
>>>
>>> I believe that this is incorrect, at least, this is in question. The
>>> compiler options (set elsewhere) are correct from an ABI point of view,
>>> and the output will be a soft float ABI target, but it's not the right
>>> architecture revision target. It will matter in a few cases. For example
>>> when a package is choosing inline assembly or other specifics that
>>> differ between ARMv5 and ARMv7. Mostly, we've been lucky in that the
>>> differences are small, but I suspect hidden breakage is lurking.
>>>
>>> In this specific example, OpenMPI should move to the new GCC atomics
>>> stuff in due course, but they have a giant mess called "asmlib" that
>>> provides their own custom atomic functions (what could go wrong?) for
>>> historical reasons. The macros used to build that are enough to make you
>>> gouge your eyes out, but once you figure it out, it's obvious that they
>>> do already have ARMv5 assembly code that should work, if it thinks it's
>>> building for an armv5l system. And it's faster to just pick that up than
>>> reworking a lot of not just code, but also other arches and build
>>> macros, and other stuff unique to the OpenMPI atomics setup.
>>>
>>> Let's ponder how we're going to fix it. I could be wrong, but I'd think
>>> we want to ensure that configure is picking up
>>> armv5l-redhat-linux-gnueabi as the host type on armv5tel builds. It
>>> should do this irrespective of the actual host architecture of the
>>> builder. I tried just force overriding it in a test build with an
>>> "%{ifarch} armv5tel" but that wasn't picked up, so I missed something,
>>> but in general that's not the right approach anyway. We want something
>>> at the r-r-c level.
>>>
>>> Comments? Dennis? Peter?
>>
>> It should always take the details that the build system is telling it
>> and not the underlying platform without exception. The same goes with
>> features like NEON (and MMX/SSE on x86). I've fixed a number of these
>> before.
>
> Good. Then you agree it should be thinking armv5l-redhat-linux-gnueabi
> there and this is a bug we need to fix. If we figure out why this is
> happening, OpenMPI should just build. Meanwhile, if you do setup a
> "wimpybuilder" channel for v5-specific builds, you could add OpenMPI
> into that channel and it ought to build if the host is ARMv5. I also
> thinking we could do something to get at least one successful build
> through by ensuring it runs on a system that is an ARMv5 host. Then we'd
> at least have an openmpi package that had been built as a dep.
I'll have a play to get it on a guru builder.
Peter
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