Intel® High Level Synthesis Compiler Pro Edition: Reference Manual

ID 683349
Date 10/04/2021

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7.1. Serial Equivalence within a Memory Space or I/O

Within a single memory space or I/O (stream read/write, Avalon-MM interface read/write, or component invocation input and return), every invocation of the component (that is, every cycle where the start signal is asserted and the component holds the busy signal low) on the component invocation interface behaves as though the previous invocation was fully executed.

When visualizing a single shared memory space, think of multiple function calls as executing sequentially, one after another. This way, when the component asserts the done signal, the results of a component invocation in hardware are guaranteed to be visible to both the next component invocation and the external system.

The HLS compiler takes advantage of pipeline parallelism to execute component invocations and loop iterations in parallel if the associated dependencies allow for parallel execution. Because the HLS compiler generates hardware that keeps track of dependencies across component invocations, it can support pipeline parallelism while guaranteeing serial equivalence across memory spaces. Ordering between independent I/O instructions is not guaranteed.