[Bug rtl-optimization/87678] Redundant vmovss with -fPIC

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87678

--- Comment #4 from Segher Boessenkool <segher at gcc dot gnu.org> ---
It tries twice, first just the substitution, and then that modified with
the REG_EQUAL.  You know a mem is not often valid in the resulting insn,
but combine doesn't, and that is not the same thing as not having a mem
in the inputs anyway!