Download ARC assembly code

Cosc 2150:
Computer Organization
ARC assembly code
Simplified SPARC language
ARC Hardware
• There are 32 32-bit registers. %r0 through
%r31.
• Reserved registers:
—%r0 is always 0.
– Storing anything in %r0 will be lost.
• %r14 is a stack pointer register
— also called %sp
• %r15 is link register (used for subroutine
calls)
The ARCTools Simulator Window
• There are two addition registers
— %pc, a 32-bit program counter register
— %psr, which is a processor status register Where arithmetic/logic flags
are set.
— They are N,Z,V,C,
–
–
–
–
where N is a negative flag
Z is the zero flag
V is the overflow flag
C is the carry flag.
• The lowest 211 = 2048 addresses of the memory map are
reserved for use by the operating system.
A Basic ARC assembly program
.begin
.org 2048 !Lowest space in memory a program can go
main: !special label, for start of your code
!Assembly instructions
halt !end of assembly code
var: value
.end
! variable: value of the variable.
Arithmetic instructions
• All arithmetic and logic instructions have 3 opcode:
instruction op1, op2, op3.
– Only op2 can be immediate load/ number otherwise, they will refer to a
register.
– Any instructions that end in a cc, set condition codes (NZVC)
• addcc %r0, 1, %r1
— (%r1 = 0 + 1) would set N=0, Z=0, V=0, and C=0
•
subcc %r0, 1, %r1
— (%r1 = 0 – 1) would set N=1, Z=0, V=1, and C=0
• Assuming %r1 = 1, subcc %r1, 1, %r1
— (%r1 = %r1 –1), would set N=0, Z=1, V=0, and C=0
Data transfer instructions
• All have 2 opcode instructions.
• load:
—ld [x], %r1 !load the value of x into %r1
—ld %r1+x, %r2 !load the value found by %r1 +x (offset)
into %r2
• store:
—st %r1, [x] !store the value of %r1 into x
—st %r2, %r1+x ! store the value of %r2 into the address
%r1 +x
Branch instructions
• All but one branch instruction have a single opcode in the
following format
— branch label ! branch conditionally or unconditionally to the label
• example:
ba done !branch to the label done
! assembly code
done: halt ! stop the program
• be, bcs, bcc, bneg, bvs, bvc, bne, bpos all use the NZVC
condition flags to as the condition whether to branch or not.
• jmpl and call are used for subroutines, which will be covered
later.
The ARCTools Edit Window
The ARCTools Edit Window
• • The Edit window with an asm file and the file
dialog
Assembly
• The arc4 program after assembly, showing arc4.lst, the listing file.
Binary File
• The arc4 bin file, displayed after pressing the Show Binary File
button.
Simulation
• The ARCTools simulator window after pressing
Bin -> Sim.
Simulator note.
• You need a blank line at
the end of the program or
the program will not
compile with normally a
very strange error that
makes no sense.
ARC example code (1)
Example 1
main () {
int a=15, b=5,c;
c = a+ b;
}
.begin
.org 2048
main: ! c = a +b
ld [a], %r1
ld [b], %r2
addcc %r1, %r2, %r3
st %r3, [c]
halt
a: 15
b: 5
c: 0
.end
ARC Example code (2)
Example 2
main() {
int a =2, c=0;
if (a == 2) {
c =a*4;
} else {
c = a/2;
}
}
.begin
.org 2048
main: ld [a], %r1
!if (a==2)
subcc %r1, 2, %r0
bne else
! true c= a*4
sll %r1, 2, %r1
ba done
! false c = a/2
else: srl %r1, 1, %r1
done: st %r1, [c]
halt
a: 2
c: 0
.end
ARC code example (3)
Example 3
main () {
int a=15, b=5, c;
if (a>=b)
c = a - b;
else
c a + b;
}
.begin
.org 2048
main: ld [a], %r1
ld [b], %r2
!if (a>=b)
subcc %r1, %r2, %r3
bneg false
st %r3, [c]
ba done
false:
add %r1, %r2, %r3
st %r3, [c]
done:
halt
a: 15
b: 5
c: 0
.end
ARC code example (4)
Example 4
main () {
int x = 0;
while (x <5) {
x = x +1;
}
.begin
.org 2048
main: ld [x], %r1
!while (x<5)
top: subcc %r1, 5, %r0
bpos done
!x = x+1
add %r1, 1, %r1
st %r1, [x]
ba top
done: halt
x: 0
.end
ARC code example (4 modified)
• Example 4
main () {
int x = 0;
while (x <=5) {
x = x +1;
}
.begin
.org 2048
main: ld [x], %r1
top: subcc %r1, 5, %r2
subcc %r2, 1, %r0
bpos done
add %r1, 1, %r1
st %r1, [x]
ba top
done: halt
x: 0
.end
Helpful things to know
•
•
•
•
•
•
•
What is the logic to figure out the following
If (a>=b) or (a>=1) or any constant
If (a>b) or (a> 1)
If (a < b) or (1 < b)
If (a <= b) or (1 <= b)
If (a==1) or (a==b)
Complex if statements
—If ( (a >10) && (b < 10) )
ARC code example (5)
• Example 5
int a=2, b=2, i=1;
while (i < 5) {
a += b;
++i;
}
}
• Give it a try
ARC code example (5 cont.)
.begin
.org 2048
main: ld [i], %r1
top:
subcc %r1, 5, %r0
bpos done
ld [a], %r2
ld [b], %r3
add %r2, %r3, %r2
st %r2, [a]
add %r1, 1, %r1
st %r1, [i]
ba top
done: halt
a: 2
b: 2
i: 1
.end
Q&A