Intel® High Level Synthesis Compiler Standard Edition: Best Practices Guide

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ID 683259
Date 12/18/2019
Public
Document Table of Contents
Document Table of Contents x
1. Intel® HLS Compiler Standard Edition Best Practices Guide 2. Best Practices for Coding and Compiling Your Component 3. Interface Best Practices 4. Loop Best Practices 5. Memory Architecture Best Practices 6. Datatype Best Practices 7. Advanced Troubleshooting A. Intel® HLS Compiler Standard Edition Best Practices Guide Archives B. Document Revision History for Intel® HLS Compiler Standard Edition Best Practices Guide
3. Interface Best Practices x
3.1. Choose the Right Interface for Your Component 3.2. Avoid Pointer Aliasing
3.1. Choose the Right Interface for Your Component x
3.1.1. Pointer Interfaces 3.1.2. Avalon® Memory Mapped Master Interfaces 3.1.3. Avalon® Memory Mapped Slave Interfaces 3.1.4. Avalon® Streaming Interfaces 3.1.5. Pass-by-Value Interface
4. Loop Best Practices x
4.1. Reuse Hardware By Calling It In a Loop 4.2. Parallelize Loops 4.3. Construct Well-Formed Loops 4.4. Minimize Loop-Carried Dependencies 4.5. Avoid Complex Loop-Exit Conditions 4.6. Convert Nested Loops into a Single Loop 4.7. Declare Variables in the Deepest Scope Possible
4.2. Parallelize Loops x
4.2.1. Pipeline Loops 4.2.2. Unroll Loops 4.2.3. Example: Loop Pipelining and Unrolling
5. Memory Architecture Best Practices x
5.1. Example: Overriding a Coalesced Memory Architecture 5.2. Example: Overriding a Banked Memory Architecture 5.3. Merge Memories to Reduce Area 5.4. Example: Specifying Bank-Selection Bits for Local Memory Addresses
5.3. Merge Memories to Reduce Area x
5.3.1. Example: Merging Memories Depth-Wise 5.3.2. Example: Merging Memories Width-Wise
6. Datatype Best Practices x
Tutorials Demonstrating Datatype Best Practices 6.1. Avoid Implicit Data Type Conversions 6.2. Avoid Negative Bit Shifts When Using the ac_int Datatype
7. Advanced Troubleshooting x
7.1. Component Fails Only In Cosimulation 7.2. Component Gets Bad Quality of Results
1. Intel® HLS Compiler Standard Edition Best Practices Guide
2. Best Practices for Coding and Compiling Your Component
3. Interface Best Practices
4. Loop Best Practices
5. Memory Architecture Best Practices
6. Datatype Best Practices
7. Advanced Troubleshooting
A. Intel® HLS Compiler Standard Edition Best Practices Guide Archives
B. Document Revision History for Intel® HLS Compiler Standard Edition Best Practices Guide

6. Datatype Best Practices

The datatypes in your component and possible conversions or casting that they might undergo can significantly affect the performance and FPGA area usage of your component. Review the datatype best practices for tips and guidance how best to control datatype sizes and conversions in your component.

After you optimize the algorithm bottlenecks of your design, you can fine-tune some datatypes in your component by using arbitrary precision datatypes to shrink data widths, which reduces FPGA area utilization. The Intel® HLS Compiler Standard Edition provides debug functionality so that you can easily detect overflows in arbitrary precision datatypes.

Tutorials Demonstrating Datatype Best Practices

The Intel® HLS Compiler Standard Edition comes with a number of tutorials that give you working examples to review and run so that you can see good coding practices as well as demonstrating important concepts.

Review the following tutorials to learn about datatype best practices that might apply to your design:
Tutorial Description
You can find these tutorials in the following location on your Intel® Quartus® Prime system:
<quartus_installdir>/hls/examples/tutorials
best_practices/ac_datatypes Demonstrates the effect of using ac_int datatype instead of int datatype.
ac_datatypes/ac_fixed_constructor Demonstrates the use of the ac_fixed constructor where you can get a better QoR by using minor variations in coding style.
ac_datatypes/ac_int_basic_ops Demonstrates the operators available for the ac_int class.
ac_datatypes/ac_int_overflow Demonstrates the usage of the DEBUG_AC_INT_WARNING and DEBUG_AC_INT_ERROR keywords to help detect overflow during emulation runtime.
best_practices/single_vs_double_precision_math Demonstrates the effect of using single precision literals and functions instead of double precision literals and functions.
best_practices/integer_promotion Demonstrates how integer promotion rules can influence the behavior of a C or C++ program.

Section Content
Avoid Implicit Data Type Conversions
Avoid Negative Bit Shifts When Using the ac_int Datatype

Level Two Title