# Assignment2: RISC-V Toolchain Bubble Sort

###### tags: `Computer architure 2020`, `riscv`, `rv32emu`

The original program was implemented by 王傑世, and I took the sample lab as a reference.

C Program:

####

void _start() {
    int tmp;
    int c=0;
    int *arr = (int*)0x15000;
    arr[0] = 2;
    arr[1] = 3;
    arr[2] = 7;
    arr[3] = 4;
    arr[4] = 1;


    for( int i = 0; i < 4; i++ ) {
        for( int j = 0; j < 4 - i; j++ ) {
            if( arr[j] > arr[j + 1] ) {
                tmp = arr[j];
                arr[j] = arr[j + 1];
                arr[j + 1] = tmp;
            }
        }
    }

    volatile int* tx = (volatile int*)0x40002000;

    while( c < 5 ) {
        *tx = *arr;
        arr++;
        c++;
    } 
}

####

-Os

./emu-rv32i test1
illegal write 32, PC: 0x000100d0, address: 0x40002000

>>> Execution time: 77174 ns
>>> Instruction count: 127 (IPS=1645631)
>>> Jumps: 23 (18.11%) - 10 forwards, 13 backwards
>>> Branching T=19 (67.86%) F=9 (32.14%)

-O1

./emu-rv32i test1
illegal write 32, PC: 0x000100d4, address: 0x40002000

>>> Execution time: 96923 ns
>>> Instruction count: 111 (IPS=1145239)
>>> Jumps: 20 (18.02%) - 6 forwards, 14 backwards
>>> Branching T=15 (53.57%) F=13 (46.43%)

-O2

./emu-rv32i test1
illegal write 32, PC: 0x000100bc, address: 0x40002000

>>> Execution time: 81763 ns
>>> Instruction count: 97 (IPS=1186355)
>>> Jumps: 15 (15.46%) - 6 forwards, 9 backwards
>>> Branching T=15 (62.50%) F=9 (37.50%)

-O3

./emu-rv32i test1
illegal write 32, PC: 0x00010128, address: 0x40002000

>>> Execution time: 30513 ns
>>> Instruction count: 47 (IPS=1540327)
>>> Jumps: 4 (8.51%) - 4 forwards, 0 backwards
>>> Branching T=4 (57.14%) F=3 (42.86%)

objdump:

test1:     file format elf32-littleriscv

Disassembly of section .text:

00010054 <_start>:
   10054:	000157b7          	lui	a5,0x15
   10058:	00300613          	li	a2,3
   1005c:	00c7a023          	sw	a2,0(a5) # 15000 <__global_pointer$+0x36ac>
   10060:	00100613          	li	a2,1
   10064:	00600713          	li	a4,6
   10068:	00500693          	li	a3,5
   1006c:	00c7a223          	sw	a2,4(a5)
   10070:	00400613          	li	a2,4
   10074:	00d7a823          	sw	a3,16(a5)
   10078:	00c7a423          	sw	a2,8(a5)
   1007c:	00e7a623          	sw	a4,12(a5)
   10080:	00e6d663          	bge	a3,a4,1008c <_start+0x38>
   10084:	00d7a623          	sw	a3,12(a5)
   10088:	00e7a823          	sw	a4,16(a5)
   1008c:	000157b7          	lui	a5,0x15
   10090:	0007a703          	lw	a4,0(a5) # 15000 <__global_pointer$+0x36ac>
   10094:	0047a683          	lw	a3,4(a5)
   10098:	00e6d663          	bge	a3,a4,100a4 <_start+0x50>
   1009c:	00d7a023          	sw	a3,0(a5)
   100a0:	00e7a223          	sw	a4,4(a5)
   100a4:	000157b7          	lui	a5,0x15
   100a8:	0047a703          	lw	a4,4(a5) # 15004 <__global_pointer$+0x36b0>
   100ac:	0087a683          	lw	a3,8(a5)
   100b0:	00e6d663          	bge	a3,a4,100bc <_start+0x68>
   100b4:	00d7a223          	sw	a3,4(a5)
   100b8:	00e7a423          	sw	a4,8(a5)
   100bc:	000157b7          	lui	a5,0x15
   100c0:	0087a703          	lw	a4,8(a5) # 15008 <__global_pointer$+0x36b4>
   100c4:	00c7a683          	lw	a3,12(a5)
   100c8:	08e6c063          	blt	a3,a4,10148 <_start+0xf4>
   100cc:	000157b7          	lui	a5,0x15
   100d0:	0007a703          	lw	a4,0(a5) # 15000 <__global_pointer$+0x36ac>
   100d4:	0047a683          	lw	a3,4(a5)
   100d8:	00e6d663          	bge	a3,a4,100e4 <_start+0x90>
   100dc:	00d7a023          	sw	a3,0(a5)
   100e0:	00e7a223          	sw	a4,4(a5)
   100e4:	000157b7          	lui	a5,0x15
   100e8:	0047a703          	lw	a4,4(a5) # 15004 <__global_pointer$+0x36b0>
   100ec:	0087a683          	lw	a3,8(a5)
   100f0:	00e6d663          	bge	a3,a4,100fc <_start+0xa8>
   100f4:	00d7a223          	sw	a3,4(a5)
   100f8:	00e7a423          	sw	a4,8(a5)
   100fc:	000157b7          	lui	a5,0x15
   10100:	0007a703          	lw	a4,0(a5) # 15000 <__global_pointer$+0x36ac>
   10104:	0047a683          	lw	a3,4(a5)
   10108:	00e6d663          	bge	a3,a4,10114 <_start+0xc0>
   1010c:	00d7a023          	sw	a3,0(a5)
   10110:	00e7a223          	sw	a4,4(a5)
   10114:	00015737          	lui	a4,0x15
   10118:	00072683          	lw	a3,0(a4) # 15000 <__global_pointer$+0x36ac>
   1011c:	00472583          	lw	a1,4(a4)
   10120:	400027b7          	lui	a5,0x40002
   10124:	00872603          	lw	a2,8(a4)
   10128:	00d7a023          	sw	a3,0(a5) # 40002000 <__global_pointer$+0x3fff06ac>
   1012c:	00c72683          	lw	a3,12(a4)
   10130:	00b7a023          	sw	a1,0(a5)
   10134:	01072703          	lw	a4,16(a4)
   10138:	00c7a023          	sw	a2,0(a5)
   1013c:	00d7a023          	sw	a3,0(a5)
   10140:	00e7a023          	sw	a4,0(a5)
   10144:	00008067          	ret
   10148:	00d7a423          	sw	a3,8(a5)
   1014c:	00e7a623          	sw	a4,12(a5)
   10150:	f7dff06f          	j	100cc <_start+0x78>

readelf

riscv-none-embed-readelf -h test1
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:               0x10054
  Start of program headers:          52 (bytes into file)
  Start of section headers:          608 (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:         6
  Section header string table index: 5

size:

   text	   data	    bss	    dec	    hex	filename
    256	      0	      0	    256	    100	test1