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

[Joseph Myers <joseph at codesourcery dot com>]

On Wed, 27 Feb 2019, GT wrote:

> 3. A new file, vec_finite_alias.c is a workaround until the vector
> log function is implemented. It is needed so that libmvec_nonshared.a
> is built. Without it, compiling against the newly-built glibc will
> fail due to its being missing.

It's inappropriate for this file to contain any log functions or 
references.  Presumably an empty file should suffice until a function 
handled in bits/math-finite.h is added.

> 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 
parties.

> 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).

-- 
Joseph S. Myers
joseph@codesourcery.com