In High Level Synthesis world, effectiveness of any tool depends on  its ability to extract parallelism, inherent in the application. Please read Limits of Instruction Level Parallelism for thorough discussion on parallelism related issues.

Degree of parallelism is directly dependent on Dependence in the code. Any high level synthesis tool should be able to understand, resolve and circumvent dependence to increase effective parallelism of the application. Thorough discussion on dependece can be read here @ Data Dependence Lecture Notes.

There are multiple types of dependencies, as shown below.

• Algorithm Specific - It can not be resolved, change in algorithm required to increase performance.

• Coding Style Specific - Depends on Code Writing Style and nuances of language. There may be unnecessary assignments or Pointer Aliasing in the code. Few can be resolved easily but some may require complex analysis of the system. However, High Level Synthesis tool must be able to handle this to achieve required effectiveness.

• Somewhat related to coding style, these limitations are because of development plateform, for example output dependence. These are minor irritants but can be handled effectively.

Once dependeces are resolved effectively, next issue is effective distribution/partition of the resources. Any partitioning algorithm for high level synthesis should be able to handle following

• Ability to look at resource cost from multiple perspective.
• Ability to combine related resources so that effective sharing can be performed
• Ability to pipeline a resource to meet timing requirements
• Ability to combine two unrelated resources so that area of combined resource is less than sum of area of individual resources.
• Ability to make tradeoff based on timing, latency and area.