---
tags : Computer Architecture
---
# Assignment2: RISC-V Toolchain
[TOC]
## Introduction
This is referenced from `段雅培` [Inner Dot Product](https://hackmd.io/@kaeteyaruyo/risc-v-hw1)
## Rewrite in C Code
``` clike=
#include <stdio.h>
////// return floor(a / b) //////
int div(int a, int b){
int counter = 0;
while(a>=0){
a = a-b;
counter++;
}
return counter-1;
}
////// return (a % b) //////
int mod(int a, int b){
int t = 0;
while(a>=0){
t = a;
a = a-b;
}
return t;
}
int _start(){
volatile char *tx = (volatile char*) 0x40002000;
char *str1 = "The inner product of two vectors is ";
int a[3] = {-1, -2, 3};
int b[3] = {4, -5, -6};
int length = 3;
int t = 0;
int sum = 0;
for (int i = 0; i < length; i++){
sum += a[i] * b[i];
}
//------------ print ------------//
////// print a[] //////
*tx = 'a';
*tx = ':';
for(int i = 0; i<length ; i++){
if((a[i]>>31) != 0){
*tx = '-';
t = ~(a[i]-1);
}
else
t = a[i];
*tx = t + '0';
*tx = ' ';
}
*tx = '\n';
////// print b[] //////
*tx = 'b';
*tx = ':';
for(int i = 0; i<length ; i++){
if((b[i]>>31) != 0){
*tx = '-';
t = ~(b[i]-1);
}
else
t = b[i];
*tx = t + '0';
*tx = ' ';
}
*tx = '\n';
////// print str1 //////
while(*str1!='\0')
*tx = *str1++;
////// print sum //////
char ans[10];
int index = 0;
int s = sum;
if((s>>31) != 0){
*tx = '-';
s = ~(s-1);
}
while(s != 0){
t = mod(s, 10);
s = div(s, 10);
ans[index++] = t + '0';
}
while(index>0)
*tx = ans[--index];
*tx = '\n';
return 0;
}
```
## Execute it
###
```
cc -O3 -Wall -std=gnu99 -o emu-rv32i emu-rv32i.c -lelf
riscv-none-embed-gcc -march=rv32i -mabi=ilp32 -O3 -nostdlib -o test dot.c
./emu-rv32i test
a:-1 -2 3
b:4 -5 -6
The inner product of two vectors is -12
>>> Execution time: 251504 ns
>>> Instruction count: 300 (IPS=1192823)
>>> Jumps: 47 (15.67%) - 8 forwards, 39 backwards
>>> Branching T=41 (78.85%) F=11 (21.15%)
```
## Toolchain
### $ riscv-none-embed-objdump -d test
```
test: file format elf32-littleriscv
Disassembly of section .text:
00010054 <div>:
10054: 00050793 mv a5,a0
10058: 02054063 bltz a0,10078 <div+0x24>
1005c: 00000513 li a0,0
10060: 0080006f j 10068 <div+0x14>
10064: 00070513 mv a0,a4
10068: 40b787b3 sub a5,a5,a1
1006c: 00150713 addi a4,a0,1
10070: fe07dae3 bgez a5,10064 <div+0x10>
10074: 00008067 ret
10078: fff00513 li a0,-1
1007c: 00008067 ret
00010080 <mod>:
10080: 00055663 bgez a0,1008c <mod+0xc>
10084: 0140006f j 10098 <mod+0x18>
10088: 00078513 mv a0,a5
1008c: 40b507b3 sub a5,a0,a1
10090: fe07dce3 bgez a5,10088 <mod+0x8>
10094: 00008067 ret
10098: 00000513 li a0,0
1009c: 00008067 ret
000100a0 <_start>:
100a0: fd010113 addi sp,sp,-48
100a4: fff00793 li a5,-1
100a8: 00f12c23 sw a5,24(sp)
100ac: ffe00793 li a5,-2
100b0: 00f12e23 sw a5,28(sp)
100b4: 00300793 li a5,3
100b8: 02f12023 sw a5,32(sp)
100bc: 00400793 li a5,4
100c0: 02f12223 sw a5,36(sp)
100c4: ffb00793 li a5,-5
100c8: 02f12423 sw a5,40(sp)
100cc: ffa00793 li a5,-6
100d0: 02f12623 sw a5,44(sp)
100d4: 40002737 lui a4,0x40002
100d8: 06100793 li a5,97
100dc: 00f70023 sb a5,0(a4) # 40002000 <__global_pointer$+0x3fff0428>
100e0: 03a00793 li a5,58
100e4: 00f70023 sb a5,0(a4)
100e8: 01812783 lw a5,24(sp)
100ec: 0007da63 bgez a5,10100 <_start+0x60>
100f0: 02d00793 li a5,45
100f4: 00f70023 sb a5,0(a4)
100f8: 01812783 lw a5,24(sp)
100fc: 40f007b3 neg a5,a5
10100: 03078793 addi a5,a5,48
10104: 40002737 lui a4,0x40002
10108: 0ff7f793 andi a5,a5,255
1010c: 00f70023 sb a5,0(a4) # 40002000 <__global_pointer$+0x3fff0428>
10110: 02000793 li a5,32
10114: 00f70023 sb a5,0(a4)
10118: 01c12783 lw a5,28(sp)
1011c: 0007da63 bgez a5,10130 <_start+0x90>
10120: 02d00793 li a5,45
10124: 00f70023 sb a5,0(a4)
10128: 01c12783 lw a5,28(sp)
1012c: 40f007b3 neg a5,a5
10130: 03078793 addi a5,a5,48
10134: 40002737 lui a4,0x40002
10138: 0ff7f793 andi a5,a5,255
1013c: 00f70023 sb a5,0(a4) # 40002000 <__global_pointer$+0x3fff0428>
10140: 02000793 li a5,32
10144: 00f70023 sb a5,0(a4)
10148: 02012783 lw a5,32(sp)
1014c: 0007da63 bgez a5,10160 <_start+0xc0>
10150: 02d00793 li a5,45
10154: 00f70023 sb a5,0(a4)
10158: 02012783 lw a5,32(sp)
1015c: 40f007b3 neg a5,a5
10160: 03078793 addi a5,a5,48
10164: 40002737 lui a4,0x40002
10168: 0ff7f793 andi a5,a5,255
1016c: 00f70023 sb a5,0(a4) # 40002000 <__global_pointer$+0x3fff0428>
10170: 02000793 li a5,32
10174: 00f70023 sb a5,0(a4)
10178: 00a00793 li a5,10
1017c: 00f70023 sb a5,0(a4)
10180: 06200793 li a5,98
10184: 00f70023 sb a5,0(a4)
10188: 03a00793 li a5,58
1018c: 00f70023 sb a5,0(a4)
10190: 02412783 lw a5,36(sp)
10194: 0007da63 bgez a5,101a8 <_start+0x108>
10198: 02d00793 li a5,45
1019c: 00f70023 sb a5,0(a4)
101a0: 02412783 lw a5,36(sp)
101a4: 40f007b3 neg a5,a5
101a8: 03078793 addi a5,a5,48
101ac: 40002737 lui a4,0x40002
101b0: 0ff7f793 andi a5,a5,255
101b4: 00f70023 sb a5,0(a4) # 40002000 <__global_pointer$+0x3fff0428>
101b8: 02000793 li a5,32
101bc: 00f70023 sb a5,0(a4)
101c0: 02812783 lw a5,40(sp)
101c4: 0007da63 bgez a5,101d8 <_start+0x138>
101c8: 02d00793 li a5,45
101cc: 00f70023 sb a5,0(a4)
101d0: 02812783 lw a5,40(sp)
101d4: 40f007b3 neg a5,a5
101d8: 03078793 addi a5,a5,48
101dc: 40002737 lui a4,0x40002
101e0: 0ff7f793 andi a5,a5,255
101e4: 00f70023 sb a5,0(a4) # 40002000 <__global_pointer$+0x3fff0428>
101e8: 02000793 li a5,32
101ec: 00f70023 sb a5,0(a4)
101f0: 02c12783 lw a5,44(sp)
101f4: 0007da63 bgez a5,10208 <_start+0x168>
101f8: 02d00793 li a5,45
101fc: 00f70023 sb a5,0(a4)
10200: 02c12783 lw a5,44(sp)
10204: 40f007b3 neg a5,a5
10208: 03078793 addi a5,a5,48
1020c: 40002737 lui a4,0x40002
10210: 0ff7f793 andi a5,a5,255
10214: 00f70023 sb a5,0(a4) # 40002000 <__global_pointer$+0x3fff0428>
10218: 02000793 li a5,32
1021c: 00f70023 sb a5,0(a4)
10220: 00a00793 li a5,10
10224: 00f70023 sb a5,0(a4)
10228: 000107b7 lui a5,0x10
1022c: 3b078793 addi a5,a5,944 # 103b0 <_start+0x310>
10230: 05400713 li a4,84
10234: 400026b7 lui a3,0x40002
10238: 00178793 addi a5,a5,1
1023c: 00e68023 sb a4,0(a3) # 40002000 <__global_pointer$+0x3fff0428>
10240: 0007c703 lbu a4,0(a5)
10244: fe071ae3 bnez a4,10238 <_start+0x198>
10248: 02d00793 li a5,45
1024c: 00c10593 addi a1,sp,12
10250: 00100813 li a6,1
10254: 00f68023 sb a5,0(a3)
10258: 40b80833 sub a6,a6,a1
1025c: 00c00793 li a5,12
10260: 00b80533 add a0,a6,a1
10264: 00078693 mv a3,a5
10268: 0080006f j 10270 <_start+0x1d0>
1026c: 00070693 mv a3,a4
10270: ff668713 addi a4,a3,-10
10274: fe075ce3 bgez a4,1026c <_start+0x1cc>
10278: 00000713 li a4,0
1027c: 0080006f j 10284 <_start+0x1e4>
10280: 00060713 mv a4,a2
10284: ff678793 addi a5,a5,-10
10288: 00170613 addi a2,a4,1
1028c: fe07dae3 bgez a5,10280 <_start+0x1e0>
10290: 03068693 addi a3,a3,48
10294: 00d58023 sb a3,0(a1)
10298: 00070863 beqz a4,102a8 <_start+0x208>
1029c: 00158593 addi a1,a1,1
102a0: 00070793 mv a5,a4
102a4: fbdff06f j 10260 <_start+0x1c0>
102a8: fff50713 addi a4,a0,-1
102ac: 03010793 addi a5,sp,48
102b0: 00e787b3 add a5,a5,a4
102b4: fdc7c683 lbu a3,-36(a5)
102b8: 400027b7 lui a5,0x40002
102bc: 00d78023 sb a3,0(a5) # 40002000 <__global_pointer$+0x3fff0428>
102c0: 0c070c63 beqz a4,10398 <_start+0x2f8>
102c4: ffe50713 addi a4,a0,-2
102c8: 03010693 addi a3,sp,48
102cc: 00e686b3 add a3,a3,a4
102d0: fdc6c683 lbu a3,-36(a3)
102d4: 00d78023 sb a3,0(a5)
102d8: 0c070063 beqz a4,10398 <_start+0x2f8>
102dc: ffd50713 addi a4,a0,-3
102e0: 03010693 addi a3,sp,48
102e4: 00e686b3 add a3,a3,a4
102e8: fdc6c683 lbu a3,-36(a3)
102ec: 00d78023 sb a3,0(a5)
102f0: 0a070463 beqz a4,10398 <_start+0x2f8>
102f4: ffc50713 addi a4,a0,-4
102f8: 03010693 addi a3,sp,48
102fc: 00e686b3 add a3,a3,a4
10300: fdc6c683 lbu a3,-36(a3)
10304: 00d78023 sb a3,0(a5)
10308: 08070863 beqz a4,10398 <_start+0x2f8>
1030c: ffb50713 addi a4,a0,-5
10310: 03010693 addi a3,sp,48
10314: 00e686b3 add a3,a3,a4
10318: fdc6c683 lbu a3,-36(a3)
1031c: 00d78023 sb a3,0(a5)
10320: 06070c63 beqz a4,10398 <_start+0x2f8>
10324: ffa50713 addi a4,a0,-6
10328: 03010693 addi a3,sp,48
1032c: 00e686b3 add a3,a3,a4
10330: fdc6c683 lbu a3,-36(a3)
10334: 00d78023 sb a3,0(a5)
10338: 06070063 beqz a4,10398 <_start+0x2f8>
1033c: ff950713 addi a4,a0,-7
10340: 03010693 addi a3,sp,48
10344: 00e686b3 add a3,a3,a4
10348: fdc6c683 lbu a3,-36(a3)
1034c: 00d78023 sb a3,0(a5)
10350: 04070463 beqz a4,10398 <_start+0x2f8>
10354: ff850713 addi a4,a0,-8
10358: 03010693 addi a3,sp,48
1035c: 00e686b3 add a3,a3,a4
10360: fdc6c683 lbu a3,-36(a3)
10364: 00d78023 sb a3,0(a5)
10368: 02070863 beqz a4,10398 <_start+0x2f8>
1036c: ff750713 addi a4,a0,-9
10370: 03010793 addi a5,sp,48
10374: 00e787b3 add a5,a5,a4
10378: fdc7c683 lbu a3,-36(a5)
1037c: 400027b7 lui a5,0x40002
10380: 00d78023 sb a3,0(a5) # 40002000 <__global_pointer$+0x3fff0428>
10384: 00070a63 beqz a4,10398 <_start+0x2f8>
10388: 03010713 addi a4,sp,48
1038c: 00a70533 add a0,a4,a0
10390: fd254703 lbu a4,-46(a0)
10394: 00e78023 sb a4,0(a5)
10398: 400027b7 lui a5,0x40002
1039c: 00a00713 li a4,10
103a0: 00e78023 sb a4,0(a5) # 40002000 <__global_pointer$+0x3fff0428>
103a4: 00000513 li a0,0
103a8: 03010113 addi sp,sp,48
103ac: 00008067 ret
```
### $ riscv-none-embed-readelf -h test
```
ELF Header:
Magic: 7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00
Class: ELF32
Data: 2's complement, little endian
Version: 1 (current)
OS/ABI: UNIX - System V
ABI Version: 0
Type: EXEC (Executable file)
Machine: RISC-V
Version: 0x1
Entry point address: 0x100a0
Start of program headers: 52 (bytes into file)
Start of section headers: 1428 (bytes into file)
Flags: 0x0
Size of this header: 52 (bytes)
Size of program headers: 32 (bytes)
Number of program headers: 1
Size of section headers: 40 (bytes)
Number of section headers: 7
Section header string table index: 6
```
### $ riscv-none-embed-size test
```
text data bss dec hex filename
900 0 0 900 384 test
```
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