Why the V4QImode vector operations are expanded into many SImode at "oplower" pass?

[Ling-hua Tseng]

On Wed, 18 May 2005 17:25:35 +0200, Paolo Bonzini wrote
> > Now I'm implementing the V4QI SIMD add operation.
> 
> Maybe there is no register that can store a V4QI.
> 
> Paolo
Doesn't the register allocation pass perform in the RTL optimization passes?
Could it affect the tree-level optimization pass?

BTW,
I have tried to adjust the constraints to 'r' (general registers) for 
the "movv4qi" and "addv4qi" insn patterns,
but I got the same problem.

Thanks.