A processor core in an instruction block-based microarchitecture includes a control unit that allocates instructions into an instruction window in bulk by fetching blocks of instructions and associated resources including control bits and operands at once. Such bulk allocation supports increased efficiency in processor core operations by enabling consistent management and policy implementation across all the instructions in the block during execution. For example, when an instruction block branches back on itself, it may be reused in a refresh process rather than being re-fetched from the instruction cache. As all of the resources for that instruction block are in one place, the instructions can remain in place and only valid bits need to be cleared. Bulk allocation also facilitates operand sharing by instructions in a block and explicit messaging among instructions.