1. Nios II Custom Instruction Overview
2. Custom Instruction Hardware Interface
3. Custom Instruction Software Interface
4. Design Example: Cyclic Redundancy Check
5. Introduction to Nios® II Floating Point Custom Instructions
6. Nios II Floating Point Hardware 2 Component
7. Nios® II Floating Point Hardware (FPH1) Component
8. Document Revision History for Nios II Custom Instruction User Guide
4.1.1. Setting up the Environment for the CRC Example Design
4.1.2. Opening the Component Editor
4.1.3. Specifying the Custom Instruction Component Type
4.1.4. Displaying the Custom Instruction Block Symbol
4.1.5. Adding the CRC Custom Instruction HDL Files
4.1.6. Configuring the Custom Instruction Parameter Type
4.1.7. Setting Up the CRC Custom Instruction Interfaces
4.1.8. Configuring the Custom Instruction Signal Type
4.1.9. Saving and Adding the CRC Custom Instruction
4.1.10. Generating and Compiling the CRC Example System
6.1. Overview of the Floating Point Hardware 2 Component
6.2. Floating Point Hardware 2 IEEE 754 Compliance
6.3. IEEE 754 Exception Conditions with FPH2
6.4. Floating Point Hardware 2 Operations
6.5. Building the FPH2 Example Hardware
6.6. Building the FPH2 Example Software
6.7. FPH2 Implementation of GCC Options
6.8. Nios II FPH2 and the Newlib Library
6.9. C Macros for round(), fmins(), and fmaxs()
6.6.3.1. -mcustom-<operation>
The -mcustom-<operation> command-line option instructs GCC to call custom instructions instead of emulating the specified operation. The syntax of the -mcustom-<operation> is as follows:
-mcustom-<operation>=N
N custom instruction value, an unsigned decimal. For a complete list of the operations and their N values, refer to the table in "Floating Point Hardware 2 Operations".
By default, the compiler implements all floating point operations in software. You can also specify software emulation for an individual instruction with the -mno-custom-<operation> command-line option.
Note: The command line can specify multiple -mcustom- switches. If there is a conflict, the last switch on the command line takes effect.
The following command-line options should be passed to GCC to instruct it to use all operations provided by the FPH2 that can be inferred by GCC. For more information, refer to "FPH2 and Nios II GCC".
For users of the Nios II SBT, these command-line arguments are automatically added to the invocation of GCC by the generated makefiles. For more information, refer to "Building the FPH2 Example Software".
-mcustom-fabss=224 -mcustom-fnegs=225 -mcustom-fcmpnes=226 -mcustom-fcmpeqs=227 -mcustom-fcmpges=228 -mcustom-fcmpgts=229 -mcustom-fcmples=230 -mcustom-fcmplts=231 -mcustom-fmins=232 -mcustom-fmaxs=233 -mcustom-round=248 -mcustom-fixsi=249 -mcustom-floatis=250 -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254 -mcustom-fdivs=255
Note: There is no command-line option for the round operation.