CSE12 ASM/C
• Lab3 this week • lab4 soon
•Must install WSL (Windows) or brew (OSX)
Copyright By PowCoder代写加微信 assignmentchef
Annoucements
Prof. Renau
•6.1-Assembly code snippets •if/else
•6.2-Assembly directives
Last class
Prof. Renau
•6.3-compiling RISC-V baremetal •6.4-C vs assembly
•6.6-C-array in assembly •6.7-C-string in assembly
Prof. Renau
Compiling Assembly
• Compile assembly to machine code
riscv64-unknown-elf-gcc -march=rv32i -mabi=ilp32 -c -o sequential.o sequential.s
• Generate an hex file out of machine code riscv64-unknown-elf-objcopy -O ihex sequential.o sequential.hex
# Sequential code example
addi x2, x2, 80
lw x3, 0(x2)
addi x3, x3, 3
addi x4, x0, 84
lw x5, 0(x4)
subx3, x3, x5
sw x3, 0(x2)
jalx0, 0
Prof. Renau
• Anything after a #
Assembly Comments
# Sequential code example
addi x2, x2, 80
lw x3, 0(x2)
addi x3, x3, 3# also comment
addi x4, x0, 84
lw x5, 0(x4)
subx3, x3, x5
sw x3, 0(x2)
jalx0, 0
Prof. Renau
• identifier followed by a colon foo:
# Sequential code example
addi x2, x2, 80
lw x3, 0(x2)
addi x3, x3, 3# also comment
addi x4, x0, 84
lw x5, 0(x4)
subx3, x3, x5
sw x3, 0(x2)
my_end_of_code:
jalx0, my_end_of_code
jalx0, label3
Assembly Labels
Prof. Renau
• period and command .byte
.global __reset
lw x3, money
addix3,x3,3 #money=money+3
lw x5, interest
sub x3, x3, x5 # money = money – interest sw x3, money, x8
my_end_of_code:
jalx0, my_end_of_code
.word 33 # initialized to 33
.word2 # initialized to 2
Assembly Directives
Prof. Renau
Assembly RISC-V Pseudo-instructions
• Syntax sugar
•Assembler translates for you
• RISC-V spec
• https://riscv.org/wp-content/uploads/2017/05/riscv-spec-v2.2.pdf •page 110
CMPE 110 Prof. Renau
Elements of Assembly Language
# This is a comment
.global __reset
• Instructions
•risc-v (same as before with help) •risc-v pseudo-instructions
• Comments (#…) • Labels
•The compiler help to compute immediates • Assembler Directives
• https://michaeljclark.github.io/asm.html
# call C main
j irq_handler
irq_handler:
la gp, __global_pointer
la sp, __stack_pointer
la t0, __bss_start
la t1, __bss_end
bgeu t0, t1, memclr_done
sw zero, (t0)
addi t0, t0, 4
bltu t0, t1, memclr
memclr_done:
Prof. Renau
• Linux binaries have 3 main sections •Most OS have similar systems
•Read only data or program binary
•Increases binary size • DATA
•Read/Write data that can be initialized to some value
•Increases binary size • BSS
•Read/Write data initialized to zero
•Allocated by OS, it does not increase binary size •An extra load may be needed to get BSS starting point
• Since we do not have OS, in emulsiv, DATA is similar to BSS •Just that “someone” has to clear to zero
Review on Binary Sections
CMPE 110 Prof. Renau
Share notes and comments with the people next to you. You can prepare a question for the end of the break.
2 MINUTE THINKING BREAK
CMPE 110 Prof. Renau
#include
int main() {
printf(“hello world
”);
Compiling Hello World
Prof. Renau
separated by spaces that does not start with a digit (0-9)
• Variable declaration int potato;
char foo,bar; // not so nice coding wise, but legal
• Variable Assignment potato = 3;
• Variable
•a continuous sequence of alphanumeric characters or underscores
CMPE 110 Prof. Renau
•a continuous sequence of alphanumeric characters or underscores
separated by spaces that starts with a digit (0-9)
•33 // Decimal •0x33 // Hexadecimal •012 // Octal
Numbers vs Variables
• Variables
•a continuous sequence of alphanumeric characters or underscores
separated by spaces that does not start with a digit (0-9)
CMPE 110 Prof. Renau
• Arithmetic a = b+c
a = b*c a = c+3*4 a = 3+-3 /%
• Bitwise a = b|c a = b^3
a = b & 0x3
•a=b&&c //bandc :better: b!=0andc!=0 •c=a||c //a!=0orc!=0
Expressions
CMPE 110 Prof. Renau
• a += 3 •…
Shorthand Expressions
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b = a++ + a++ + a++;
What is the value of c?
What is the value of b?
Precedence
Prof. Renau
1. Left-to-right: (), aa++
2. Right-to-left: ++aa, -, +, !, ~
3. Left-to-right: *, /, %
4. Left-to-right: +, –
5. Left-to-right: <<, >>
6. Left-to-right: <, <=, >, >=
7. Left-to-right: ==, !=
8. Left-to-right: &
9. Left-to-right: ^
10. Left-to-right: |
11. Left-to-right: &&
12. Left-to-right: ||
13. Right-to-left: +=, -=, ^=, …
b = a++ + a++ + a++; // 1+2+3
Expressions Operator Precedence
Prof. Renau
1. Left-to-right: (), aa++
2. Right-to-left: ++aa, -, +, !, ~
3. Left-to-right: *, /, %
4. Left-to-right: +, –
5. Left-to-right: <<, >>
6. Left-to-right: <, <=, >, >=
7. Left-to-right: ==, !=
8. Left-to-right: &
9. Left-to-right: ^
10. Left-to-right: |
11. Left-to-right: &&
12. Left-to-right: ||
13. Right-to-left: +=, -=, ^=, …
b0=~a; //-2 b1 = ~a++; //
b2 = ~++a; //
b3 = ~(a+1);//
b4 = (~a)+1;//
Expressions Operator Precedence
Prof. Renau
1. Left-to-right: (), aa++
2. Right-to-left: ++aa, -, +, !, ~
3. Left-to-right: *, /, %
4. Left-to-right: +, –
5. Left-to-right: <<, >>
6. Left-to-right: <, <=, >, >=
7. Left-to-right: ==, !=
8. Left-to-right: &
9. Left-to-right: ^
10. Left-to-right: |
11. Left-to-right: &&
12. Left-to-right: ||
13. Right-to-left: +=, -=, ^=, …
b0=~a; //-2 b1 = ~a++; // -2 b2=~++a;//-3 b3 = ~(a+1);// -3 b4 = (~a)+1;// -1
Expressions Operator Precedence
Prof. Renau
1. Left-to-right: (), aa++
2. Right-to-left: ++aa, -, +, !, ~
3. Left-to-right: *, /, %
4. Left-to-right: +, –
5. Left-to-right: <<, >>
6. Left-to-right: <, <=, >, >=
7. Left-to-right: ==, !=
8. Left-to-right: &
9. Left-to-right: ^
10. Left-to-right: |
11. Left-to-right: &&
12. Left-to-right: ||
13. Right-to-left: +=, -=, ^=, …
b0 = 1 || 0 && 1; // b1 = !1 && 1; // b1 = ~1 && 1; // b1=~1 &1; // b1=!1 &1; //
Expressions Operator Precedence
Prof. Renau
1. Left-to-right: (), aa++
2. Right-to-left: ++aa, -, +, !, ~
3. Left-to-right: *, /, %
4. Left-to-right: +, –
5. Left-to-right: <<, >>
6. Left-to-right: <, <=, >, >=
7. Left-to-right: ==, !=
8. Left-to-right: &
9. Left-to-right: ^
10. Left-to-right: |
11. Left-to-right: &&
12. Left-to-right: ||
13. Right-to-left: +=, -=, ^=, …
b0 = 1 || 0 && 1; // 1 b1 = !1 && 1; //0 b1 = ~1 && 1; //1 b1=~1 &1; //0 b1=!1 &1; //0
Expressions Operator Precedence
Prof. Renau
Expressions Operator Precedence
• Precedence can get tricky
•My suggestion: DO NOT COMPLICATE YOUR LIFE
•Unary higher precedence (!, ~) •* more precedence than +
•Use parenthesis otherwise
a || (b && c)
•Do not use modifying operators in an expression.
•Avoid things like: a = b++ + 3
CMPE 110 Prof. Renau
• gcc or clang
• https://learn.onlinegdb.com/
•More for teaching C (no RISC-V)
• https://godbolt.org/
•Can generate risc-v assembly and useful
C compiler
Prof. Renau
int myfun(int a) {
if (a == 2) {
return 33;
return 44; }
Prof. Renau
#include
int main() {
int a = 1;
if (a == 2) {
printf(“never_called
”);
printf(“hello world
”);
Prof. Renau
#include
int main() {
int a = 1;
while (a < 3 ) { printf(“hello world
“);Prof. Renau #include
int main() {
for(int i=0;i<5;i++) { printf(“hello world
“);Prof. Renau #include
int fun1(int a) {
int b = a;
int a = 3;
printf(“1. a=%d
”,a);
printf(“2. a=%d
”,a);
int main() {
int c = fun1(a);
printf(“3. a=%d c=%d
”,a,c);
Variable Scope
Prof. Renau
• C strings are zero terminated •“hello” becomes ‘h’ ‘e’ ‘l’ ‘l’ ‘o’ 0
#include
int main() {
char array[10] = “hello”;
char *ptr = “hello”;
printf(“my string is %s
”,array); printf(“my string is %s
”,ptr);
for(int i=0;i<8;i++) {printf(“[%c] is [%d]
“, array[i], array[i]); }Prof. RenauShare notes and comments with the people next to you. You can prepare a question for the end of the break.2 MINUTE THINKING BREAK CMPE 110 Prof. Renau •6.3-compiling RISC-V baremetal •6.4-C vs assembly•6.6-C-array in assembly •6.7-C-string in assemblyProf. Renau•6.3-compiling RISC-V baremetal •6.4-C vs assemblyNext ClassProf. Renau程序代写 CS代考 加微信: assignmentchef QQ: 1823890830 Email: [email protected]
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