Re: recent troubles with float vectors & bitwise ops

[Ian Lance Taylor <iant at google dot com>]

Paolo Bonzini <paolo.bonzini@lu.unisi.ch> writes:

> 1) neg, abs and copysign operations on vectors.  These we can make
> available via builtins (for - of course you don't need it); we already
> support them in many back-ends.

Here is my point of view.  People using the vector extensions are
already writing inherently machine specific code, and they are
(ideally) familiar with the instruction set of their processor.  I see
no significant disadvantage to gcc to granting them easy access to the
capabilities of their processor.  Saying that these capabilities are
available in other ways just amounts to putting an obstacle in their
path.  If there is a reason to put in that obstacle--e.g., because we
are implementing a language standard and the language standard forbids
it--then fine.  But citing a PowerPC specific standard to forbid code
appropriate for the x86 does not count as a sufficient reason in my
book.

Permitting this extension continues the preexisting behaviour, and it
helps programmers and helps existing code.  Who does it hurt to permit
this extension?  Who does it help to forbid this extension?

Ian