High-Level Synthesis: Productivity, Performance, and Software Constraints

Table 3

For loop directives.

Directive	Description
loop_flatten	Combine multiple levels of perfectly nested loops to form a single loop with larger loop bounds
loop_merge	Combine two separate loops at the same hierarchy level into a single loop
loop_unroll	Duplicate computation inside the loop—increase computation resources, decrease number of iterations
pipeline	Pipeline computation within the loop (or region) scope—increase throughput and computation resources
occurrence	Specify that one operation occurs at a slower (integer divisor) rate than the outer loop—improve pipeline scheduling, resource use
expression_balance	Typically automatic-code in the loop (or region) is optimized via associative and commutative properties to create a balanced tree of computation