Tracking operand liveliness information in a computer system and performance function based on the liveliness information

A computer implemented method for maintaining liveness information for executing programs, the method comprising:

• maintaining, by a processor, current operand state information, the current operand state information for indicating whether corresponding current operands are any one of enabled or disabled for use by a first program module, the first program module comprising machine instructions of an instruction set architecture (ISA), the first program module currently being executed by the processor;
• accessing a current operand, by a machine instruction of said first program module, the accessing comprising using the current operand state information to determine whether a previously stored current operand value is accessible by the first program module.