Re: Clang as default compiler November 4th

From: Steve Kargl <sgk_at_troutmask.apl.washington.edu>
Date: Tue, 11 Sep 2012 11:13:17 -0700
On Tue, Sep 11, 2012 at 07:19:48PM +0200, Roman Divacky wrote:
> On Tue, Sep 11, 2012 at 08:12:30AM -0700, Steve Kargl wrote:
> > 
> > I'm not sure if anyone has done any extensive testing.
> > I've started to run some of my test codes to compare
> > certain functions in a clang-compiled libm, gcc-compiled
> > libm, and reference solutions generated from math/mpfr.
> > For a locally patched j0f, I found that clang gave
> > much worse accuracy.  If I revert the local patch,
> > clang and gcc are to give the same results.  Unfortnately,
> > an unpatched j0f gives 500000 ULP errors.
> 
> Steve,
> 
> Can you please provide a small self contained test case that shows
> that clang is doing worse on accuracy than gcc?
> 
> So that we can analyze it and decide if it's a bug in the code or
> in the compiler. So far we know absolutely nothing.
> 
> Thank you, Roman

Unfortunately, supplying a test is going to be problematic.
I thought I had a diff in one of my development trees, so I 
reverted the working copy of msun/e_j0f.c to stock source.
gcc and clang give consistent results with stock e_j0f.c.
When I went to re-apply my local changes, I discovered that
I no longer had a diff.  I think I can recreate the problematic
code, but it will need to wait until the weekend.

-- 
Steve
Received on Tue Sep 11 2012 - 16:13:20 UTC

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