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Re: GCC Vector Extensions
Christian Schoenebeck writes:
> Es geschah am Wednesday, 19. April 2006 17:20 als Andrew Haley schrieb:
> > OK, I got it now.
> >
> > The full spec is at
> >
> > http://publib.boulder.ibm.com/infocenter/macxhelp/v6v81/index.jsp?topic=/com.ibm.vacpp6m.doc/language/ref/clrc03altivec_types.htm
>
> Well, this is a different compiler and the docs are just about this
> compiler, not a regular language specification.
Sure, but it's the base we used for gcc, and it's what current users
expect.
> Yeah, but also consider that old PPCs did not even have an
> instruction for int->float conversion. Is that a reason for
> defining a scalar int->float cast as bitstream copy? Certainly not.
Too late: it's the specification. See
"2.4.6 Type Casting
"... None of the casts performs a conversion; the bit pattern of the
result is the same as the bit pattern of the argument that is cast."
The full spec is at http://www-306.ibm.com/chips/techlib/techlib.nsf/techdocs/30B3520C93F437AB87257060006FFE5E/$file/SPU_language_extensions_2.1.pdf
Now, you might think that we need a different specification, and lots
of people would agree with you! But it's not a bug in the gcc
implementation.
Andrew.