Method, system and apparatus for generation of global branch history

A method for generating a global history;

• comprising:
• generating a set of global history bits;
• and
• storing the set of global history bits in a global history register operable to store a first set of bits, wherein the global history bits are generated by global history logic, comprising:
• a plurality of sets of multiplexers, each set of multiplexers corresponding to one of a set of instructions fetched during a cycle, wherein each multiplexer in a set of multiplexers has a select signal coupled to a bit of a shift_in signal corresponding to the one of the set of instructions to which the set of multiplexers corresponds, the plurality of sets of multiplexers including a first set of multiplexers comprising a first multiplexer having a first input coupled to a first bit of a branch history signal corresponding to the one of the set of instructions to which the first set of multiplexers corresponds and a second input coupled to a first bit of the global history register.

An system, comprising:

• an instruction fetch unit operable to fetch a set of instructions;
• a branch history table operable to generate a branch history bit for each of the set of instructions;
• logic operable to generate a shift-in signal, the shift in signal comprising a set of shift_in bits, each shift_in bit corresponding to one of the set of instructions;
• a global history register operable to store a first set of bits;
• and
• global history generation logic operable to generate a set of global history bits, the global history logic comprising:
• a plurality of sets of multiplexers, each set of multiplexers corresponding to one of the set of instructions, wherein each multiplexer in a set of multiplexers has a select signal coupled to the bit of the shift_in signal corresponding to the one of the set of instructions, the plurality of sets of multiplexers including a first set of multiplexers comprising a first multiplexer having a first input coupled to the branch history bit corresponding to the one of the set of instructions to which the first set of multiplexers corresponds and a second input coupled to a first bit of the global history register.

An apparatus for generating a global history;

• comprising:
• a global history register operable to store a first set of bits;
• and
• global history generation logic operable to generate a set of global history bits, the global history logic comprising:
• a plurality of sets of multiplexers, each set of multiplexers corresponding to one of a set of instructions fetched during a cycle, wherein each multiplexer in a set of multiplexers has a select signal coupled to a bit of a signal line corresponding to the one of the set of instructions to which the set of multiplexers corresponds, the plurality of sets of multiplexers including:
• a first set of multiplexers, comprising:
• a first multiplexer having a first input coupled to a first bit of a branch history signal corresponding to the one of the set of instructions to which the first set of multiplexers corresponds and a second input coupled to a first bit of the global history register, and
• a second multiplexer having a first input coupled to a first bit of the global history register and a second input coupled to a second bit of the global history register;
• and
• a second set of multiplexers, comprising:
• a first multiplexer having a first input coupled to a second bit of a branch history signal corresponding to the one of the set of instructions to which the second set of multiplexers corresponds and a second input coupled to the output of the first multiplexer of the first set of multiplexers, and
• a second multiplexer having a first input coupled to the output of the first multiplexer of the first set of multiplexers and a second input coupled to the output of the second multiplexer of the first set of multiplexers.