Extension elimination pass breaks SPU (Fw: spu gcc-4.5 linaro build failure)

[Mark Mitchell]

On 12/20/2010 10:54 AM, Matthias Klose wrote:

> So, I'll build without Linaro on powerpc.  Next we'll see regressions on
> ix86 and x86_64, which are not fixed, so stop building these
> architectures without the Linaro changes?  Or build without Linaro on
> ix86 and x86_64?  Or maybe be a bit more conservative what gets into the
> Linaro toolchain? 

I'm not trying to take an extreme position; I'm really looking for an
answer here.  We've got something approaching 100 engineers doing
ARM-oriented work in various components.  They build on ARM, test on
ARM, benchmark on ARM.  They live ARM, they breathe ARM.  I think it's
likely they're going to break non-ARM, no matter how well-intentioned
they are.

So, the question is what policies we should have pre-checkin (to
validate other architectures) and post-checkin (when a problem is
reported on another architecture).  I don't think we have very good
clarity there.  I suspect that if more distributions start taking more
technology from Linaro, we'll see this issue arise more and more often.

Correctness is a relatively easy case, but what happens when we see that
a 10% performance improvement on ARM resulted in a 2% decrease on MIPS
or 3% on x86?  What commitment, if any, are we making to a distribution
that cares about all of ARM, MIPS, and x86?

Thank you,

-- 
Mark Mitchell
CodeSourcery
mark at codesourcery.com
(650) 331-3385 x713