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Re: [PATCH] PPC64: First in the series of patches implementing POWER8 vector math.

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, February 19, 2019 10:54 PM, Joseph Myers <> wrote:

> On Tue, 19 Feb 2019, GT wrote:
> > GCC fails if an attempt is made to compile code that uses Altivec
> > functionality without passing the -maltivec flag. Additionally it also
> > fails on attempts to build for pre-POWER7 hardware even when
> > -maltivec flag is given to the compiler. Is there need to add a
> > check in configure for attempts to build libmvec on non-Altivec, non-VSX
> > systems; or let the failure happen when make calls GCC?
> It's best to detect the issue at configure time. That's definitely needed
> if you want to enable libmvec by default as on x86_64.

I've had trouble modifying to detect attempts at building
libmvec on machines without Altivec/VSX. But perhaps the problem isn't
with changes I've made:

After making changes to sysdeps/powerpc/powerpc64/ I changed
directory to the root of the glibc source. Then I ran autoconf with no
arguments, as instructed in the manual. Checking the timestamps,
configure was not regenerated. I forced regeneration by running
'autoconf -f' and this time configure was regenerated at the root of
glibc source. But sysdeps/powerpc/powerpc64/configure was not
re-created. Running autoconf -v showed lines that begin with
'autom4te: forbidden tokens: .....'.

Just to be sure it isn't something I introduced, I cloned a new glibc
source tree and the only command run there thus far was autoconf -f -v.
The same lines appear noting forbidden tokens.

Is there an issue generating the configure script or are those messages
about forbidden tokens harmless?

And running autoconf at the glibc source-tree root directory should
regenerate configure scripts in all subdirectories which have in them, right?

> I'm not sure why it would fail for pre-POWER7, if you pass -maltivec for
> the AltiVec versions and -mvsx for the versions requiring VSX.

Turns out POWER7 is the earliest POWERn that implements v2.06 of the ISA.
v2.06 is when type vector double was introduced. So the behavior is
as expected.

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