Added CSRRWI support

src/cpu/rv32cpu.c

@@ -559,7 +559,10 @@ static void cpu_execute(rv32_cpu_t* cpu, instruction_t* instruction)
 					fprintf(stderr, "CSRRC\n");
 					break;
 				case FUNC3_CSRRWI:
-					fprintf(stderr, "CSRRWI\n");
+					// CSR atomic Read/Write Immediate (immediate in rs1)
+					uint32_t csrrwi_old_value = cpu->csr[instruction->immediate];
+					cpu->csr[instruction->immediate] = instruction->rs1;
+					cpu->regs.x[instruction->rd] = csrrwi_old_value;
 					break;
 				case FUNC3_CSRRSI:
 					fprintf(stderr, "CSRRSI\n");