[Bug target/117850] GCC emits DUP, UMULL instead of UMULL2

[rsandifo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117850

--- Comment #3 from Richard Sandiford <rsandifo at gcc dot gnu.org> ---
(In reply to rguenther@suse.de from comment #2)
> I dont See how this is easier?

It's not to simplify things :)  But isn't gimple_fold_builtin restricted to the
same search/valueisation domain as match.pd?  Or does gimple_fold_builtin have
more freedom to follow the argument definitions as far as it likes?