RISC-V

Create a C library file.

• riscv-nuclei-elf-gcc
• riscv-nuclei-elf-ar
• riscv-nuclei-elf-ranlib
• riscv-nuclei-elf-nm
• Spike emulator

• This tutorial is written and tested for the macOS.
  
  
• Create the following 4 files and place these files in the same directory (for example ~/demo):
  
  add.c
  subtract.c
  calculate.h
  program.c
  
  
• Goto demo directory:
  Type: cd ~/demo
  
  
• Compile add.c:
  Type: riscv-nuclei-elf-gcc -c -march=rv32imac -mabi=ilp32 -mcmodel=medlow add.c
  
  Output: add.o is created.
  
  
• Compile subtract.c:
  Type: riscv-nuclei-elf-gcc -c -march=rv32imac -mabi=ilp32 -mcmodel=medlow subtract.c
  
  Output: subtract.o is created.
  
  
• Create archive file:
  Type: riscv-nuclei-elf-ar rc libcaldemo.a add.o subtract.o
  
  Note 1: Enter the archive name (.a) followed by the files (.o) which will be put inside the archive.
  Note 2: The archive filename MUST start with the prefix "lib": libcaldemo.a
  
  Output: libcaldemo.a is created.
  
  
• View the content of the archive file:
  Type: riscv-nuclei-elf-ar t libcaldemo.a
  
  Output:
  add.o
  subtract.o
  
  To extract all files from the archive file:
  Type: riscv-nuclei-elf-ar x libcaldemo.a
  
  You can also use the tar command:
  View content, type: tar -tvf libcaldemo.a
  Extract content, type: tar -xvf libcaldemo.a
  
  
• Generate an index to the contents of the archive (libcaldemo.a) and store it in the archive:
  Type: riscv-nuclei-elf-ranlib libcaldemo.a
  
  Note:
  The GNU ranlib program is another form of GNU ar; running ranlib is completely equivalent to executing ar -s: Type: riscv-nuclei-elf-ar -s libcaldemo.a
  
  
• Use the nm tool to list this index:
  An archive with such an index speeds up linking to the library and allows routines in the library to call each other without regard to their placement in the archive.
  
  Type: riscv-nuclei-elf-nm --print-armap libcaldemo.a
  
  Output:
  Archive index:
  add_one in add.o
  subtract_one in subtract.o
  
  add.o:
  00000000 T add_one
  
  subtract.o:
  00000000 T subtract_one
  
  
• Compile program.c using the archive/library (libcaldemo.a):
  Type: riscv-nuclei-elf-gcc -march=rv32imac -mabi=ilp32 -mcmodel=medlow
  program.c -L. -lcaldemo -o program
  
  Note 1:
  
  • -l (lowercase L) is for specifying libraries. The linker searches for a file named liblibrary.a
    
    
  • -L is for specifying library locations.
    For example: -L. means currect directory.
    
    
  • -I (uppercase i) is for specifying include directories of header files.
    For example: If the header file is located at ~/demo/includes/calculate.h
    
    Type: riscv-nuclei-elf-gcc -march=rv32imac -mabi=ilp32 -mcmodel=medlow
    -I./includes program.c -L. -lcaldemo -o program
  
  Note 2:
  You can also compile program.c without using the archive/library file.
  Type: riscv-nuclei-elf-gcc -march=rv32imac -mabi=ilp32 -mcmodel=medlow
  program.c add.o subtract.o -o program
  
  
• Execute the program:
  Type: spike $PK_PATH/pk program
  
  Output:
  value=10
  value+1=11
  value-1=9
  
  Note:
  I am using the Spike emulator to execute the program because the program only works on a RISCV architecture. The toolchain used (riscv-nuclei-elf-xxx) targets RISCV hardware.