| File | Description |
|---|---|
| 1to9_custom.c | C program that sums integers from 1 to 9. Calls load.S |
| hello.c | C program that prints 'Hello World' |
| hex8tohex32.py | Python program that converts byte data to 32-bit word data |
| load.S | Assembly program that performs summation of integers from 1 to N |
| picorv32.v | RISC-V 32-bit core example |
| riscv.ld | RISC-V ld script for example |
| rv32im.sh | RISC-V simulation bash script. Run this for example |
| start.S | Assembly program for initializing RISC-V example |
| start.ld | Start ld script for example |
| syscalls.c | C program containing system call definitions for example |
| testbench.v | Verilog testbench for RISC-V example |
Day 1 was comprised of the RISC-V ISA and GNU compiler toolchain, which were used in Day 2 labs.
Compile command:
$ riscv64-unkown-elf-gcc -O<1/fast> -mabi=lp<XLEN> -march=rv<XLEN>i -o <output_program> <input_user_file> [<input_user_file>...]
Assembly preview command:
$ riscv64-unkown-elf-objdump -d <output_program>
Run command:
$ spike pk <output_program>
Debug command:
$ spike -d pk <output_program>
The Application Binary Interface (ABI), also known as the System Call Interface, is used by the program to access the ISA registers. RISC-V architecture contains 32 registers of width 32/64 if using RV32I/RV64I, respectively:
| Register | ABI Name | Usage |
|---|---|---|
| x0 | zero | Hard-wired zero |
| x1 | ra | Return address |
| x2 | sp | Stack pointer |
| x3 | gp | Global pointer |
| x4 | tp | Thread opinter |
| x5-7 | t0-2 | Temporaries |
| x8 | s0/fp | Saved register/frame pointer |
| x9 | s1 | Saved register |
| x10-11 | a0-1 | Function arguments/return values |
| x12-17 | a2-7 | Function arguments |
| x18-27 | s2-11 | Saved registers |
| x28-31 | t3-6 | Temporaries |
There are 3 types of instructions:
- R-type: operate only on registers
Ex:add x8, x24, x8 - I-type: operate on registers and immediate values
Ex:ld x8, 16(x23) - S-type: operate on source registers and store in immediate value
Ex:sd x8, 8(x23)
A simple program for summing numbers 1 to 9 was created; view source here. The compiled output in assembly looks like this:
