public v3.1 p182

If the contents of register FRS were produced, either
directly or indirectly, by a Load Floating-Point Single
instruction, a single-precision Arithmetic instruction, or
frsp, then the value stored is undefined. (The contents
of register FRS are produced directly by such an instruc-
tion if FRS is the target register for the instruction. The
contents of register FRS are produced indirectly by such
an instruction if FRS is the final target register of a
sequence of one or more Floating-Point Move instruc-
tions, with the input to the sequence having been pro-
duced directly by such an instruction.)