[Bug target/69577] [5/6 Regression] wrong code with -fno-forward-propagate -mavx and 128bit arithmetics since r215450

[rsandifo at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69577

--- Comment #7 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> ---
(In reply to Uroš Bizjak from comment #6)
> IMO, we should revert r215450, and fix a couple of cases using narrowing
> conversions with gen_lowpart that were introduced after r215450.

Please give me a few days to look at it first.  I still think r215450 is
correct and reverting it is likely to regress code quality.