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Re: Errors building libgcc for powerpc64le-linux-gnu


On Sun, Dec 15, 2019 at 09:43:20AM -0800, Ian Lance Taylor wrote:
> On Sat, Dec 14, 2019 at 11:25 PM Segher Boessenkool
> <segher@kernel.crashing.org> wrote:
> >
> > On Sat, Dec 14, 2019 at 10:51:50AM -0800, Ian Lance Taylor via gcc wrote:
> > > I'm seeing compiler crashes building libgcc for powerpc64le-linux-gnu,
> > > cross-compiling from x86_64-pc-linux-gnu.  I'm at SVN revision 279830.
> > > I'm seeing the following.  Is anybody else seeing this crash?  Thanks.
> >
> > No, and that makes me wonder what is going on.  The error is simple enough
> > of course, as you note in a later message; but why do we not see it on
> > every other build?
> 
> I think it's because clang treats a left shift by a negative number as
> undefined behavior but GCC does not.  So GCC is consistently producing
> some number, and clang is producing different numbers.
> 
> I should note that I don't really understand what purpose that
> constant is serving anyhow.

It's the (old, changed months ago!) register number for CR7.  This code
creates the bitfield that says which CR fields to save or restore.

Anyway, should be fixed now.  If you can confirm, please do :-)


Segher


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