Intel® High Level Synthesis Compiler Pro Edition: Reference Manual
ID
683349
Date
1/23/2025
Public
1. Discontinuation of the Intel® HLS Compiler
2. Intel® HLS Compiler Pro Edition Reference Manual
3. Compiler
4. C Language and Library Support
5. Component Interfaces
6. Component Memories (Memory Attributes)
7. Loops in Components
8. Component Concurrency
9. Arbitrary Precision Math Support
10. Component Target Frequency
11. Systems of Tasks
12. Libraries
13. Advanced Hardware Synthesis Controls
14. Intel® High Level Synthesis Compiler Pro Edition Reference Summary
A. Advanced Math Source Code Libraries
B. Supported Math Functions
C. Cyclone® V Restrictions
D. Intel® HLS Compiler Pro Edition Reference Manual Archives
E. Document Revision History of the Intel® HLS Compiler Pro Edition Reference Manual
15. Discontinuation of the Intel® HLS Compiler
7.1. Loop Initiation Interval (ii Pragma)
7.2. Loop-Carried Dependencies (ivdep Pragma)
7.3. Loop Coalescing (loop_coalesce Pragma)
7.4. Loop Unrolling (unroll Pragma)
7.5. Loop Concurrency (max_concurrency Pragma)
7.6. Loop Iteration Speculation (speculated_iterations Pragma)
7.7. Loop Pipelining Control (disable_loop_pipelining Pragma)
7.8. Loop Interleaving Control (max_interleaving Pragma)
7.9. Loop Fusion
12.4.1.1. Integration of an RTL Module into the HLS Pipeline
12.4.1.2. RTL Module Interfaces
12.4.1.3. RTL Reset and Clock Signals
12.4.1.4. Object Manifest File Syntax
12.4.1.5. Mapping HLS Data Types to RTL Signals
12.4.1.6. HLS Emulation Models for RTL-Based Functions
12.4.1.7. Potential Incompatibility between RTL Modules and Partial Reconfiguration
12.4.1.8. Stall-Free RTL
12.4.1.9. RTL Module Restrictions and Limitations for HLS Libraries
14.1. Intel® HLS Compiler Pro Edition i++ Command-Line Arguments
14.2. Intel® HLS Compiler Pro Edition Header Files
14.3. Intel® HLS Compiler Pro Edition Compiler-Defined Preprocessor Macros
14.4. Intel® HLS Compiler Pro Edition Keywords
14.5. Intel® HLS Compiler Pro Edition Simulation API (Testbench Only)
14.6. Intel® HLS Compiler Pro Edition Component Memory Attributes
14.7. Intel® HLS Compiler Pro Edition Loop Pragmas
14.8. Intel® HLS Compiler Pro Edition Scope Pragmas
14.9. Intel® HLS Compiler Pro Edition Component Attributes
14.10. Intel® HLS Compiler Pro Edition Component Default Interfaces
14.11. Intel® HLS Compiler Pro Edition Component Invocation Interface Control Attributes
14.12. Intel® HLS Compiler Pro Edition Component Macros
14.13. Intel® HLS Compiler Pro Edition Systems of Tasks API
14.14. Intel® HLS Compiler Pro Edition Pipes API
14.15. Intel® HLS Compiler Pro Edition Streaming Input Interfaces
14.16. Intel® HLS Compiler Pro Edition Streaming Output Interfaces
14.17. Intel® HLS Compiler Pro Edition Memory-Mapped Interfaces
14.18. Intel® HLS Compiler Pro Edition Load-Store Unit Control
14.19. Intel® HLS Compiler Pro Edition Arbitrary Precision Data Types
B.1. Math Functions Provided by the math.h Header File
B.2. Math Functions Provided by the extendedmath.h Header File
B.3. Math Functions Provided by the ac_fixed_math.h Header File
B.4. Math Functions Provided by the hls_float.h Header File
B.5. Math Functions Provided by the hls_float_math.h Header File
B.6. Default Rounding Schemes and Subnormal Number Support
7.7. Loop Pipelining Control (disable_loop_pipelining Pragma)
When the loop iterations effectively execute sequentially due to loop-carried dependencies, use the disable_loop_pipelining pragma to generate a simple sequential datapath and avoid loop resource hardware duplication. The simpler datapath and lack of resource duplication in hardware reduces the FPGA area utilization of your component.
Use the Loop Analysis section of the high-level design reports (report.html) to help determine if you should apply this pragma to your loops.
In the following example, the Intel® HLS Compiler fails to schedule the loop with a small loop initiation interval (II) because of a memory dependency. Pipelining this loop is unlikely to have any benefit to your component throughput or performance.
#pragma disable_loop_pipelining for (int i = 1; i < N; i++) { int j = a[i-1]; // Memory dependency induces a high-latency loop feedback path a[i] = foo(j) }
You can also disable pipelining the datapath of your entire component with the hls_disable_component_pipelining component attribute. For more information about this attribute, see Component Pipelining Control (hls_disable_component_pipelining Attribute).