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Perry Kivolowitz 2022-12-11 08:43:29 -06:00
parent 90833b214a
commit 3834b607ab
1 changed files with 42 additions and 1 deletions
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43
projects/snow/main.s
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@ -3,6 +3,9 @@
.text
.equ NUM_FLAKES, 150
.equ MAX_COLUMN, 80
.equ MAX_LINE, 24
.equ MAX_LINE_X2, 48
storm .req x27
@ -34,7 +37,7 @@ main: stp x29, x30, [sp, -16]!
// allocated memory will be
// preserved in x27.
ldr x2, [sp], 16 // Restore the allocation size.
mov w1, xzr // Fill with zero.
mov w1, wzr // Fill with zero.
bl memset // x0 still had base address.
99: mov x0, storm
@ -54,9 +57,47 @@ bye: ldp x27, x28, [sp], 16
*/
ResetFlake:
stp x20, x30, [sp, -16]!
mov x20, x0
// Initialize Column --- 1 <= random value <= 80
bl rand
mov x1, MAX_COLUMN
bl mod
add w1, w1, 1
str w1, [x20, 4]
// Initialize Line --- -(1 <= random value <= 48)
bl rand
mov x1, MAX_LINE_X2
bl mod
add w1, w1, 1
neg w1, w1
str w1, [x20]
ldp x20, x30, [sp], 16
ret
/* mod(a, b) - implements a % b - AARCH64 lacks a mod instruction.
A strange place to economize, but there you have it.
a comes to us in x0
b comes to us in x1
method:
* integer divide a by b
for example - 5 % 3 would need 5 // 3 yielding 1
* multiply result by b
1 * 3 is 3
* subtract result from a
5 - 3 is 2 and that's our return value.
*/
mod: sdiv x2, x0, x1 // x2 gets a // b
msub x0, x2, x1, x0 // x0 gets a - a // b * b
ret
.data
bad_malloc: .asciz "Allocation of flakes has failed"