Complex floating point instructions are executed under millicode control
when it is not cost effective to implement its function in hardware. One
of the disadvantages to executing complex instructions using millicode
routines is that determining and accessing the instructions operands are
costly for millicode performance. To determine what the source and target
location are, the instruction text is parsed. Furthermore the millicode
instruction stream must be modified to access the operand data from and
write the result to the program registers specified by the complex
floating point instruction. The invention overcomes these disadvantages
by providing millicode with register indirect access to the program
floating point registers.