This patch folds a vector of equal values to the scalar in
vector-shift operation.

ChangeLog:

2010-11-01  Artjoms Sinkarovs <artyom.shinakroff@gmail.com>

     gcc/
     * passes.c (init_optimization_passes): Move veclower after SSA.
     * tree-vect-generic.c (expand_vector_operations_1): Handle conversion.

     gcc/testsuite/
     * gcc.dg/vec-scal-opt.c: New testcase.
     * gcc.dg/vec-scal-opt1.c: New testcase.
     * gcc.dg/vec-scal-opt2.c: New testcase.


bootstrapped and tested on x86_64_unknown-linux

OK?