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
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

4.6. Convert Nested Loops into a Single Loop

To maximize performance, combine nested loops into a single loop whenever possible. The control flow for a loop adds overhead both in logic required and FPGA hardware footprint. Combining nested loops into a single loop reduces these aspects, improving the performance of your component.

The following code examples illustrate the conversion of a nested loop into a single loop:

Nested Loop Converted Single Loop 
for (i = 0; i < N; i++)
{
    //statements
    for (j = 0; j < M; j++)
    {
        //statements          
    }
    //statements
} 
for (i = 0; i < N*M; i++)
{
    //statements
}
Level Two Title