On Wed, Apr 19, 2006 at 05:53:30PM +0100, Andrew Haley wrote: > Janis Johnson writes: > > 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. > > You seem to have missed > > "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."
Oops. I guess we can blame the AltiVec PIM after all. Janis
