Abstract: A method and system for maintaining a best-case demand redispatch of an instruction to allow for maximizing the time a rejected thread may execute in lookahead execution mode, while maintaining the smallest L1 cache miss penalty supported by the memory subsystem. In response to a demand miss, a load/store unit sends a fetch request to the next level cache. The cache line of the demand miss is examined to identify the critical sector. Once the critical sector is identified, a best-case data return time is determined based on the fastest time the next level cache is able to return the critical sector of the cache line. The load/store unit then sends a speculative warning to the dispatch unit to coincide with the best-case data return, wherein the speculative warning prepares the dispatch unit to resend the instruction for execution as soon as data is available to the processor core.

Abstract: A method and system for recovering a global history vector. In the event of a non-branch flush, a tag may be received by a queue configured to store information about branch instructions. The queue may read a copy of the global history vector from an entry indexed by the tag. This copy may be inserted in a global history vector mechanism (“GHV mechanism”) configured to manage the global history vector. If the flush operation is a flush to a group of instructions that contains no branch instructions and the tag does not equal the next-to-write pointer in the queue, then the queue may transmit a command to the GHV mechanism to enter a mode where the GHV mechanism does not update the global history vector until the next branch instruction is fetched.