The vec_fmsubadd instuction actually had add twice, by mistake.
Also improve code-gen for all the complex patterns by using properly
undefined values. Mostly this just prevents the compiler reserving space
in the stack frame.
gcc/ChangeLog:
* config/gcn/gcn-valu.md (cmul<conj_op><mode>3): Use gcn_gen_undef.
(cml<addsub_as><mode>4): Likewise.
(vec_addsub<mode>3): Likewise.
(cadd<rot><mode>3): Likewise.
(vec_fmaddsub<mode>4): Likewise.
(vec_fmsubadd<mode>4): Likewise, and use sub for the odd lanes.