Patent ID: 8914616

Claim:
A data processing apparatus comprising: a processor unit configured to perform data processing operations in response to data processing instructions, said data processing instructions referencing program model registers; a set of physical registers configured to store data values which are subjected to said data processing operations; a tag storage unit configured to store for each physical register a tag value indicative of one of said program model registers, said processor unit configured to reference said tag storage unit in order to perform said data processing operations and said tag storage unit providing a one-to-one mapping between said program model registers and said physical registers; and a tag value exchanger configured to perform a tag switch to exchange two tag values in said tag storage unit, wherein said tag value exchanger is configured to perform said tag switch when said processor unit executes a predetermined data processing instruction, wherein said predetermined data processing instruction references two program model registers and for which a choice of which two physical registers are mapped to which of said two program model registers will have no effect on an outcome of said data processing operations, and said tag value exchanger is configured to perform said tag switch with respect to the tag values indicative of said two program model registers.