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Re: [RESEND] [PATCH] PPC64: First in the series of patches implementing POWER8 vector math.
- From: GT <tnggil at protonmail dot com>
- To: "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Date: Thu, 28 Feb 2019 13:09:53 +0000
- Subject: Re: [RESEND] [PATCH] PPC64: First in the series of patches implementing POWER8 vector math.
- References: <mbadK9r7XB9XyVASxb9oTqB0JO9qz9JKdC9mx1hUwBGcmMy7upcWFTvWuWGecBaMT3o5duV5MBjyRTEsgrtcpGltovJXQSJPH1rtECFMW-Yemail@example.com> <alpine.DEB.firstname.lastname@example.org>
- Reply-to: GT <tnggil at protonmail dot com>
> > 5. GCC has no vectorizing support for PPC64. The openmp pragmas
> > are ignored and only scalar cosine calls generated. Exactly as when
> > libmvec doesn't exist.
> I don't see any evidence that the ABI has yet been agreed by all relevant
> > 6. The executables created to test against new glibc installation
> > required a workaround. x86_64 also did when I tried to compile the
> > same test. The test is a modification of Example #1 at
> > https://sourceware.org/glibc/wiki/libmvec. The only change initially
> > is a replacement of the call to cos () with one to the vector version
> > _ZGVbN2v_cos (). Compilation fails due to function without a
> That completely defeats the point of such a test which is to verify that
> an actual vectorized call works with the actual header you are adding -
> not to repeat the verification of manual _Z* calls which is already
> adequately done by the glibc testsuite. That means you need to have a
> compiler which implements this vector ABI. If suitable GCC patches are
> posted to gcc-patches with the stated intent of applying them to GCC trunk
> after GCC 9 has branched, you could use those for testing the glibc
> changes (although I think we should avoid merging the changes into glibc
> until the relevant support is in GCC and you can name the corresponding
> GCC version in the NEWS entry - note that GCC 9 should branch well before
> the next glibc release freeze).
Searching at GCC's main site, and the gcc-patches mailing list and
bugzilla specifically; the best I can tell is that no development is
ongoing to add vectorization for PPC64.
To summarize, then, the status of glibc's PPC64/POWER8 vector math support:
1. A party responsible for the PPC64 toolchain must specify the exact
Vector Function ABI with which to adhere.
2. GCC support for the new PPC64 vector math library must be implemented; and
testing will have to demonstrate that the added functionality in GCC does
vectorize function calls in applications to use vector math versions.
3. Pending resolution of the two items above, PPC64 patches for libmvec will
be kept out of libc-alpha.
Is this an accurate characterization of where matters stand?