set_directive_occurrence

Description

When pipelining functions or loops, the OCCURRENCE directive specifies that the code in a location is executed at a lower rate than the surrounding function or loop. This allows the code that is executed at the lower rate to be pipelined at a slower rate, and potentially shared within the top-level pipeline. For example:

  • A loop iterates N times.
  • Part of the loop is protected by a conditional statement and only executes M times, where N is an integer multiple of M.
  • The code protected by the conditional is said to have an occurrence of N/M.

Identifying a region with an OCCURRENCE rate allows the functions and loops in this region to be pipelined with an initiation interval that is slower than the enclosing function or loop.

Syntax

set_directive_occurrence [OPTIONS] <location>
  • <location> specifies the location with a slower rate of execution.

Options

-cycle <int>

Specifies the occurrence N/M where:

  • N is the number of times the enclosing function or loop is executed.
  • M is the number of times the conditional region is executed.
IMPORTANT: N must be an integer multiple of M.

Examples

Region Cond_Region in function foo has an occurrence of 4. It executes at a rate four times slower than the code that encompasses it.

set_directive_occurrence -cycle 4 foo/Cond_Region

See Also