Re: [PATCH, rs6000] Use hardware support for vector character multiply

[David Edelsohn <dje dot gcc at gmail dot com>]

On Thu, Sep 3, 2015 at 11:20 AM, Bill Schmidt
<wschmidt@linux.vnet.ibm.com> wrote:
> Hi,
>
> It was pointed out to me recently that multiplying two vector chars is
> performed using scalarization, even though we have hardware support for
> byte multiplies in vectors.  This patch adds an expansion for mulv16qi3
> to correct this.
>
> The expansion is pretty simple.  We do a multiply-even and multiply-odd
> to create halfword results, and then use a permute to extract the
> low-order bytes of each result.  This particular form of a permute uses
> a different set of input/output vector modes than have been used before,
> so I added the altivec_vperm_v8hiv16qi insn to represent this.  (The two
> source operands are vector halfword types, while the target operand is a
> vector char type.)
>
> I've added two test variants, one to test the code generation, and one
> executable test to check correctness.  One other test failed with this
> change.  This turned out to be because PowerPC was excluded from the
> check_effective_target_vect_char_mult target support test.  I resolved
> this by adding check_effective_target_powerpc_altivec to that test.
>
> Bootstrapped and tested on powerpc64le-unknown-linux-gnu with no
> regressions.  Is this ok for trunk?
>
> Thanks,
> Bill
>
>
> [gcc]
>
> 2015-09-03  Bill Schmidt  <wschmidt@vnet.linux.ibm.com>
>
>         * config/rs6000/altivec.md (altivec_vperm_v8hiv16qi): New
>         define_insn.
>         (mulv16qi3): New define_expand.
>
> [gcc/testsuite]
>
> 2015-09-03  Bill Schmidt  <wschmidt@vnet.linux.ibm.com>
>
>         * gcc.target/powerpc/vec-mult-char-1.c: New test.
>         * gcc.target/powerpc/vec-mult-char-2.c: New test.

This is okay.

The "bool be = BYTES_BIG_ENDIAN" and use of "be" is not a common style in GCC.

Thanks, David