https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81594
--- Comment #3 from Michael Meissner <meissner at gcc dot gnu.org> ---
I looked at this a little. The proposed patch doesn't generate the expected
code any more (due to setting the length attribute, which makes it look like
the fix generates slower code).
I re-implemented it as a peephole2 for ISA 2.07 (power9) and above. The
peephole2 does find several places in the 2017 Spec INT benchmarks, where it
replaces:
MTVSRDD
XXPERMDI
STV
with:
STD
STD
