Re: [PATCH] powerpc64le: Add single instruction math functions

[David Edelsohn <dje.gcc@gmail.com>]

On Fri, Jun 23, 2017 at 3:35 PM, Rich Felker <dalias@libc.org> wrote:
> On Wed, Jun 21, 2017 at 10:53:13AM -0400, David Edelsohn wrote:
>> The following two patches are a start at single instruction math
>> functions for PowerPC64 architecture.  Although PPC64LE Linux and
>> ELFv2 ABI require Power8 as the minimum architecture, I have added
>> guards that fallback to C code for earlier architectures.
>
> Indeed, musl uses the ELFv2 ABI (minus its gratuitous mandate of
> minimum ISA level) for both little and big endian powerpc64, and I
> think we have users of both (people running it on old powerbooks,
> etc.).
>
> Am I reading correctly that sqrt, fma, and fabs are available even in
> the lowest powerpc64 ISA, and don't need preprocessor conditionals?

fabs and fma are part of the base ISA for Power processors that
include floating point support.  fsqrt originally was optional feature
in the distant past (General Purpose group of optional instructions),
but is required in the ISA for Power processors.

Thanks, David