For the target processor this optimization is additionally significant because, in general case, it is more efficient to set values in register by loading them from memory then by using immediate operand
The extra inputs on the 5-way multiplexers facilitate placement of an immediate operand
[d.sub.n] via the topmost multiplexer or selection of an optional "stack fill" value mfn from memory in the bottom-most multiplexer.
The following instruction combines these upper 16 bits with its own lower 16 bits to generate a 32 bit immediate operand
. An instruction must not be injected after an IMM instruction.
Command Part 1 (CP1) provides a 5-bit operating code, and Command Part 2 (CP2) offers the immediate operand
, which is the lower 5 bits of the command.
For example, a Pentium instruction might include several 8-bit prefixes, an 8-bit opcode, 8-bit format bytes, and a 16-bit immediate operand
. Most likely, the prefixes and opcode would be tokens from the same class, but the format bytes and operand would be from different classes.
Stack activity also can be reduced by moving constants on the stack into native instructions as immediate operands
. Java bytecode instructions must receive constant operands from the stack.
Immediate constants are often small; 69 percent of the immediate operands
can be encoded in 4 or fewer bits and 96 percent in 8 or fewer bits ; the corresponding figures from  are 60 percent and 70 percent.