Call-path-indexed branch prediction structure

An apparatus comprising:

• means for performing data processing in response to instructions;
• means for predicting an outcome of a branch instruction to be processed by the processing circuitry, based on branch prediction state information stored in one or more branch prediction structures;
• and
• means for storing call path tracking information, where in response to a procedure calling instruction processed by the means for performing data processing, the means for storing is configured to update the call path tracking information depending on at least a portion of an address associated with the procedure calling instruction;
• in which:
• said one or more branch prediction structures include at least one call-path-indexed branch prediction structure indexed based on an index value which depends on a portion of the call path tracking information stored in the means for storing.

A method comprising:

• performing data processing in response to instructions;
• in response to processing of a procedure calling instruction, updating call path tracking information stored in a call path tracking element depending on at least a portion of an address associated with the procedure calling instruction;
• and
• predicting an outcome of a branch instruction to be processed by the processing circuitry, based on branch prediction state information stored in one or more branch prediction structures;
• said one or more branch prediction structures including at least one call-path-indexed branch prediction structure which is indexed based on an index value which depends on a portion of the call path tracking information stored in the call path tracking element.