3.5.1.1.1 Instruction-level Parallelism

Instruction-level parallelism allows for the simultaneous execution of computations for instructions by analyzing data dependencies. Computations that are independent of each other can be executed concurrently. For example, the following code snippet performs three addition operations:

z = a + b;
x = c + d;
q = z + x;
...

Observe that the first and second additions do not depend on one another. These additions can therefore be executed concurrently, as long as there are two adder units available in the hardware. SmartHLS™ automatically analyzes the dependencies between computations in the software to exploit instruction-level parallelism in the generated hardware. The user does not need to do anything. In the above example, the third addition operation depends on the results of the first two, and hence, its execution cannot be done in parallel with the others. Instruction-level parallelism is referred to as fine-grained parallelism, as concurrency is achieved at a fine-grained level (instruction-level) of granularity.