Prefetch request generation

A non-transitory computer-readable medium storing computer-readable code for fabrication of an apparatus comprising:

• decoding circuitry to decode instructions defined according to an instruction set architecture, the instruction set architecture supporting a loop control instruction providing an explicit loop presence hint indicating that a sequence of instructions to be executed includes a program loop body to be iterated;
• processing circuitry to perform data processing in response to the decoded instructions;
• and
• prefetch circuitry to generate a prefetch request, the prefetch request comprising a request for data to be prefetched into a cache corresponding to an address predicted to be accessed by the processing circuitry in future;
• in which:
• the prefetch circuitry is configured to:
• determine whether the decoding circuitry has detected the loop control instruction in a sequence of the decoded instructions;
• in response to determining that the decoding circuitry has detected the loop control instruction, activate generation of at least one loop-control-instruction-triggered stream of prefetch requests specifying addresses predicted based on a property of at least one instruction of the program loop body whose presence is indicated by the loop control instruction;
• determine how many loop-control-instruction-triggered streams of prefetch requests are to be activated, based on a count of a number of distinct cache lines specified by target addresses of load instructions appearing within a single iteration of the program loop body;
• and
• in response to detecting that the number of distinct cache lines is greater than a threshold number, suppress activation of said at least one loop-control-instruction-triggered stream of prefetch requests, and switch to a next-cache-line-prefetch mode to trigger, in response to a cache miss detected for a given address, generation of a prefetch request specifying an address that is offset relative to the given address by a predetermined amount.