Vector types and type conversions

[Janis Johnson]

On Wed, Apr 19, 2006 at 05:30:54PM +0200, Paolo Bonzini wrote:
> 
> The C spec for Altivec (not the ISA) is a horrible spec that set a 
> horrible de facto standard.  To some extent, gcc already departed from 
> Altivec, for example by disallowing the (vector int) (1, 2, 3, 4) syntax 
> -- notice the parentheses instead of the braces -- because it was 
> extremely hackish to implement in a Bison parser.

The Motorola AltiVec PIM (sorry, I'm looking at a hard copy and don't
have the link handy) says:

  2.4.2 Assignment

  If either the left hand side or right hand side of an expression has
  a vector type, then both sides of the expression must be of the same
  vector type.  Thus, the expression a = b is valid and represents
  assignment if a and b are of the same vector type (or if neither is
  a vector type).  Otherwise, the expression is invalid and must be
  signaled as an error by the compiler.

We can't blame this admittedly horrible spec for this one.

Janis