Fast perfect issue of dependent instructions in a distributed issue queue system

A system comprising:

• a memory having computer readable instructions;
• and
• one or more processors for executing the computer readable instructions, the computer readable instructions controlling the one or more processors to perform processes comprising:
• inserting producer information of a producer instruction in a lookup entry in a lookup table, the lookup entry being allocated to a register;
• determining that the register corresponding to the lookup entry is a source for a dependent instruction;
• responsive to storing the dependent instruction in an issue queue, storing the producer information in a back-to-back entry of a back-to-back wakeup table, the back-to-back entry corresponding to the dependent instruction;
• issuing the producer instruction which causes the producer information of the producer instruction to be sent to the back-to-back wakeup table;
• determining that there is a match between the producer information and the back-to-back entry for the dependent instruction;
• and
• allowing the dependent instruction to issue based on the match.

A computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by one or more processors to cause the one or more processors to perform processes comprising:

• inserting producer information of a producer instruction in a lookup entry in a lookup table, the lookup entry being allocated to a register;
• determining that the register corresponding to the lookup entry is a source for a dependent instruction;
• responsive to storing the dependent instruction in an issue queue, storing the producer information in a back-to-back entry of a back-to-back wakeup table, the back-to-back entry corresponding to the dependent instruction;
• issuing the producer instruction which causes the producer information of the producer instruction to be sent to the back-to-back wakeup table;
• determining that there is a match between the producer information and the back-to-back entry for the dependent instruction;
• and
• allowing the dependent instruction to issue based on the match.