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In the illustrated out-of-order execution scheme without a reorder buffer, a reservation station identifier acts as the producer tag for an outstanding result. A register renaming map and waiting operands in other reservation stations can refer to that tag. The tag must remain unique until the result has been broadcast and the required register file update has occurred.

For example, issue a slow multiplication producing r1 into reservation station S, then an addition r4 := r1 + r5 into another reservation station. The addition records S as the unresolved source of r1. Even after the multiplier has accepted its operands, the multiplication can take many cycles; S cannot be reassigned merely because its operands have left the reservation station. If an independent short instruction is assigned S and broadcasts first, the addition would mistake that unrelated value for the multiplication's result. A later multiplication result could likewise corrupt the new instruction's register renaming mapping.

Finishing execution is also insufficient if the result is waiting for common data bus access: consumers and the register file still name S until writeback. Keep the producer tag allocated through broadcast/writeback, so no younger result can masquerade as the outstanding producer. With a separate persistent producer tag, such as a reorder buffer entry or a physical register, a design can release the scheduling slot earlier; this changes the tag-ownership arrangement in the question.

Consider a slow load instruction controlling one conditional addition, followed by independent work. The following is schematic A32 assembly language; the plain ADD and MUL forms shown do not update processor condition flags:Without branch prediction, the unresolved conditional branch prevents fetching beyond it until the load instruction, comparison and branch resolution complete. The multiplication does not depend on r0, yet the out-of-order execution machinery cannot execute it if it has not been fetched and issued.

Conditional execution removes that branch:ADDEQ adds one exactly when the zero flag from CMP is set; otherwise it preserves r2. The instruction stream has a known sequential continuation, so the CPU can fetch and issue the multiplication while the load instruction is outstanding. With available reservation stations and a free multiplier, independent multiplication overlaps the load instruction's latency.

Predication removes a control-flow obstacle to finding independent work; it does not resolve the slow load or its dependent condition earlier. The conditional addition must still select the correct result after the processor condition flags become known. The gain is especially useful for a short conditional region, since instructions whose predicates are false still occupy fetch and issue resources. On a strictly blocking in-order pipeline, a slow demand load instruction would still stop later work in MEM; the overlap here uses the question's out-of-order execution setting and a nonblocking memory path.