*IBM may consider it worthwhile to extend these two instructions to
v3.1 Prefixed (`pfmvis` and `pfrlsi`). If so it is recommended that
-`pfmvis` load a full FP32 immediate and `pfrlsi` extend the lower
-32-bits to construct a full FP64 immediate.*
+`pfmvis` load a full FP32 immediate and `pfrlsi` supplies the four high
+missing exponent bits (8 to 10) and the lower additional
+28 mantissa bits (23 to 51) needed to construct a full FP64 immediate.*
## Load BF16 Immediate