Intel® High Level Synthesis Compiler Pro Edition: Reference Manual

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Date 12/13/2021
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Document Table of Contents
Document Table of Contents x
1. Intel® HLS Compiler Pro Edition Reference Manual 2. Compiler 3. C Language and Library Support 4. Component Interfaces 5. Component Memories (Memory Attributes) 6. Loops in Components 7. Component Concurrency 8. Arbitrary Precision Math Support 9. Component Target Frequency 10. Systems of Tasks 11. Libraries 12. Advanced Hardware Synthesis Controls 13. 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
2. Compiler x
2.1. Intel® HLS Compiler Pro Edition Command Options 2.2. Using Libraries in Your Component 2.3. Compiler Interoperability 2.4. Intel® HLS Compiler Hardware Model
2.3. Compiler Interoperability x
2.3.1. Compiling Your Testbench and Component Separately
3. C Language and Library Support x
3.1. Supported C and C++ Subset for Component Synthesis 3.2. C and C++ Libraries 3.3. Templated and Overloaded Functions 3.4. Intel® HLS Compiler Pro Edition Compiler-Defined Preprocessor Macros
3.3. Templated and Overloaded Functions x
3.3.1. Templated Functions 3.3.2. Overloaded Functions 3.3.3. Function Name Mapping
4. Component Interfaces x
4.1. Component Invocation Interface 4.2. Avalon® Streaming Interfaces 4.3. Pipes 4.4. Avalon® Memory-Mapped Host Interfaces 4.5. Agent Interfaces 4.6. Stable Component Parameters 4.7. Global Variables 4.8. Structs in Component Interfaces 4.9. Reset Behavior
4.1. Component Invocation Interface x
4.1.1. Scalar Parameters 4.1.2. Pointer and Reference Parameters 4.1.3. Interface Definition Example: Component Invocation Interface Control Attributes 4.1.4. Interface Definition Example: Component with Both Scalar and Pointer Arguments
4.3. Pipes x
4.3.1. The pipe Class and Its Use
4.4. Avalon® Memory-Mapped Host Interfaces x
4.4.1. Memory-Mapped Host Testbench Constructor 4.4.2. Implicit and Explicit Examples of Describing a Memory Interface 4.4.3. Avalon® Memory-Mapped Host Interfaces and Load-Store Units
4.4.3. Avalon® Memory-Mapped Host Interfaces and Load-Store Units x
4.4.3.1. Load-Store Unit Types 4.4.3.2. Memory-Access Coalescing and Load-Store Units
4.5. Agent Interfaces x
4.5.1. Control and Status Register (CSR) Agent 4.5.2. Agent Memories
5. Component Memories (Memory Attributes) x
5.1. Static Variables
6. Loops in Components x
6.1. Loop Initiation Interval (ii Pragma) 6.2. Loop-Carried Dependencies (ivdep Pragma) 6.3. Loop Coalescing (loop_coalesce Pragma) 6.4. Loop Unrolling (unroll Pragma) 6.5. Loop Concurrency (max_concurrency Pragma) 6.6. Loop Iteration Speculation (speculated_iterations Pragma) 6.7. Loop Pipelining Control (disable_loop_pipelining Pragma) 6.8. Loop Interleaving Control (max_interleaving Pragma) 6.9. Loop Fusion
6.9. Loop Fusion x
6.9.1. Loop Fusion Control (loop_fuse Pragma) 6.9.2. Loop Fusion Exemption (nofusion pragma)
7. Component Concurrency x
7.1. Serial Equivalence within a Memory Space or I/O 7.2. Concurrency Control (hls_max_concurrency Attribute) 7.3. Component Pipelining Control (hls_disable_component_pipelining Attribute)
8. Arbitrary Precision Math Support x
8.1. Declaring ac_int Data Types 8.2. Declaring ac_fixed Data Types 8.3. Declaring ac_complex Data Types 8.4. AC Data Types and Native Compilers 8.5. Declaring hls_float Data Types
8.1. Declaring ac_int Data Types x
8.1.1. Important Usage Information on the ac_int Data Type 8.1.2. Integer Promotion and ac_int Data Types 8.1.3. Debugging Your Use of the ac_int Data Type
8.2. Declaring ac_fixed Data Types x
8.2.1. Arbitrary Precision Fixed-Point Literals in Operations
8.5. Declaring hls_float Data Types x
8.5.1. Operators and Return Types Supported by the hls_float Data Type 8.5.2. Additional Data Types Provided By hls_float.h
9. Component Target Frequency x
9.1. Effects of Specifying Target II and Target fMAX
10. Systems of Tasks x
10.1. Task Functions 10.2. Internal Streams 10.3. System of Tasks Simulation
11. Libraries x
11.1. Static-Object Libraries 11.2. Creating a Static-Object Library 11.3. Creating Objects From HLS Code 11.4. Creating Objects From RTL Code 11.5. Packaging Object Files Into a Library
11.3. Creating Objects From HLS Code x
11.3.1. Creating an Object File From HLS Code 11.3.2. Supported OpenCL* Language Constructs
11.4. Creating Objects From RTL Code x
11.4.1. RTL Modules and the HLS Pipeline 11.4.2. Creating a Static-Object File from an RTL Module
11.4.1. RTL Modules and the HLS Pipeline x
11.4.1.1. Integration of an RTL Module into the HLS Pipeline 11.4.1.2. RTL Module Interfaces 11.4.1.3. RTL Reset and Clock Signals 11.4.1.4. Object Manifest File Syntax 11.4.1.5. Mapping HLS Data Types to RTL Signals 11.4.1.6. HLS Emulation Models for RTL-Based Functions 11.4.1.7. Potential Incompatibility between RTL Modules and Partial Reconfiguration 11.4.1.8. Stall-Free RTL 11.4.1.9. RTL Module Restrictions and Limitations for HLS Libraries
11.4.1.2. RTL Module Interfaces x
11.4.1.2.1. RTL Module Interface Signals
11.4.1.3. RTL Reset and Clock Signals x
11.4.1.3.1. Intel® Agilex™ and Intel® Stratix® 10 Design-Specific Reset Requirements for Stall-Free and Stallable RTL Modules
11.4.1.4. Object Manifest File Syntax x
11.4.1.4.1. XML Elements for ATTRIBUTES 11.4.1.4.2. XML Elements for INTERFACE 11.4.1.4.3. XML Elements for RESOURCES
11.4.1.4.1. XML Elements for ATTRIBUTES x
11.4.1.4.1.1. Interaction Between ALLOW_MERGINGand HAS_SIDE_EFFECTS Elements
12. Advanced Hardware Synthesis Controls x
12.1. Hardware Implementation Control for Math Functions 12.2. The hls_fpga_reg() Function
12.1. Hardware Implementation Control for Math Functions x
12.1.1. Math Function Hardware Implementation Summary 12.1.2. The --dsp-mode Command Option 12.1.3. The ihc::math_dsp_control Function
13. Intel® High Level Synthesis Compiler Pro Edition Reference Summary x
13.1. Intel® HLS Compiler Pro Edition i++ Command-Line Arguments 13.2. Intel® HLS Compiler Pro Edition Header Files 13.3. Intel® HLS Compiler Pro Edition Compiler-Defined Preprocessor Macros 13.4. Intel® HLS Compiler Pro Edition Keywords 13.5. Intel® HLS Compiler Pro Edition Simulation API (Testbench Only) 13.6. Intel® HLS Compiler Pro Edition Component Memory Attributes 13.7. Intel® HLS Compiler Pro Edition Loop Pragmas 13.8. Intel® HLS Compiler Pro Edition Scope Pragmas 13.9. Intel® HLS Compiler Pro Edition Component Attributes 13.10. Intel® HLS Compiler Pro Edition Component Default Interfaces 13.11. Intel® HLS Compiler Pro Edition Component Invocation Interface Control Attributes 13.12. Intel® HLS Compiler Pro Edition Component Macros 13.13. Intel® HLS Compiler Pro Edition Systems of Tasks API 13.14. Intel® HLS Compiler Pro Edition Pipes API 13.15. Intel® HLS Compiler Pro Edition Streaming Input Interfaces 13.16. Intel® HLS Compiler Pro Edition Streaming Output Interfaces 13.17. Intel® HLS Compiler Pro Edition Memory-Mapped Interfaces 13.18. Intel® HLS Compiler Pro Edition Load-Store Unit Control 13.19. Intel® HLS Compiler Pro Edition Arbitrary Precision Data Types
13.13. Intel® HLS Compiler Pro Edition Systems of Tasks API x
13.13.1. ihc::stream Class
A. Advanced Math Source Code Libraries x
A.1. Random Number Generator Library A.2. Matrix Multiplication Library A.3. Cholesky Decomposition Library
B. Supported Math Functions x
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
1. Intel® HLS Compiler Pro Edition Reference Manual
2. Compiler
3. C Language and Library Support
4. Component Interfaces
5. Component Memories (Memory Attributes)
6. Loops in Components
7. Component Concurrency
8. Arbitrary Precision Math Support
9. Component Target Frequency
10. Systems of Tasks
11. Libraries
12. Advanced Hardware Synthesis Controls
13. 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

9. Component Target Frequency

You can specify component target frequency either in the i++ command by specifying the --clock option or by using the hls_scheduler_target_fmax_mhz component attribute. The component attribute takes priority over the command option.

For details about the --clock option, see Command Options Affecting Compiling.

For details about the hls_scheduler_target_fmax_mhz component attribute, see hls_scheduler_target_fmax_mhz Component Attribute.

The two options for setting target frequency are functionally equivalent except their scopes differ:
  • The --clock option applies to all components compiled with the invocation of the i++ command that contains the --clock option.
  • The hls_scheduler_target_fmax_mhz component attribute applies only to the component or task function that has the attribute.
To learn more about the attribute and how it interacts with the loop pragma, review the following tutorial: 
<quartus_installdir>/hls/examples/tutorials/best_practices/set_component_target_fmax
If you use both the i++ command --clock option and the hls_scheduler_target_fmax_mhz component attribute, the component attribute takes priority. For example, you can compile the following code with the i++ … --clock=300MHz command: 
component int test1(){ 
 … 
} 

hls_scheduler_target_fmax_mhz(200) 
component int test2(){ 
 … 
}

The compiler schedules component test1 at 300 MHz (from the command option) and component test2 at 200 MHz (from the component attribute).

Important!

Setting the target fMAX determines the pipelining effort at the compilation stage. Compiling with Quartus Prime software reports the achievable fMAX value for your components. This value is often different from the value you specified.

You can lower the --clock value to reduce the latency of your design at the expense of reducing the fMAX of your component.

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